Bridge Management System Tall Buildings NDT - The Indian ...

Bridge Management System 

Tall Buildings 

NDT 

Published by ACC Limited 

March 2012, Vol. 86, No. 3, Rs. 65

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Technical Papers 

07 

13 

33 

43 

maRch 2012 VOLUmE 86 NUmBER 3 

Some studies on the effect of carbonation on the engineering properties 

of concrete 

B.B. Das, S.K. Rout, D.N. Singh and S.P. Pandey 

Review of inspection practices, health indices, and condition states for 

concrete bridges 

Sanjay S. Wakchaure and Kumar N. Jha 

Non destructive evaluation of concrete interlocking paving blocks 

M.C. Nataraja and Lelin Das 

Superposition principle invalid in IS 13920 design of slender Rc walls 

with boundary elements 

D.H.H. Rohit, P. Narahari, Arvind Kumar Jaiswal and C.V.R. Murty 

Features 

03 EdITORIaL 

05 

27 

39 

52 

53 

NEwS & EVENTS 

dIScUSSION FORUm 

TaLL BUILdINGS: a year in review : Trends of 2011 – Skyscraper 

completion reaches new high for fifth year running 

Nathaniel Hollister and Antony Wood 

LETTER TO ThE EdITOR 

POINT OF VIEw: are heritage structures in Tamilnadu seismically 

vulnerable? 

A. Veerappan 

MARCH 2012 ThE INdIaN cONcRETE JOURNaL 

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Editorial 

Utilisation of agricultural residue in housing and 

construction has been investigated for many years 

with limited commercial success. Rice husk are a residue 

produced in significant quantities in India. In broad 

terms, one tonne of rice gives 200 kg of husk. For every 

1000 kg of rice husk burnt, 200 kg of ash are produced. 

This means rice husk ash (RHA) production rate is about 

40 kg per ton of rice. 1 

In 2009, it was estimated that the world production 

of rice was 480 million tonnes. 2 With India currently 

producing about 95 million tonnes of rice, the potential 

for rice husk ash in our country is about 3.5 million 

tonnes. 3 It was estimated that about 1/3 of the available 

husk in India can be collected and converted to ash for 

use as a Portland cement replacement. So, about one 

million tonne of rice husk ash is potentially available as 

a mineral admixture. 

1. Cement Replacement Materials, Rice Husk Ash, Chapter 6, by D. J. Cook, 

Surrey Press (1986) 

2. http://www.fao.org/docrep/014/am491e/am491e00.pdf 

3. http://www.livemint.com/2011/08/09184142/Rice-production-likely-tosurp.html 

Rice husk ash 

In the conversion process of rice husk to ash, the 

combustion process removes the organic matter and 

leaves a silica-rich reside. When rice husks are heated, 

weight loss occurs at 100 o C due to evaporation of 

absorbed water. At 350 o C, the volatiles ignite, causing, 

further weight loss and husks commence to burn. From 

400 o C to 500 o C, the residue carbon oxidises with the 

majority of the weight loss occurring in this period. 

The silica in the ash is still in an amorphous form 

with high reactivity. Above 600 o C, in some cases the 

formation of quartz may be detected. Prolonged heating 

at temperatures beyond 800 o C produces essentially, 

crystalline silica. 1 

The relative proportion of the forms of silica in the ash 

depends not only on the temperature of combustion but 

also the duration. Combusting husk at below 500 o C and 

up to 680 o C under oxidising atmosphere can produce 

amorphous silica provided the hold time is controlled. 

Apart from influencing the degree of crystallinity, 

the time-temperature relationship also influences the 

specific surface area of the ash, a parameter which is 

MARCH 2012 The IndIan ConCreTe Journal

closely related to the pozzolanic activity of the ash. The 

pozzolanic behavior of rice husk ash is the ability to react 

with calcium hydroxide at ambient temperature in the 

presence of moisture to form cementitious hydration 

products. 

Several researches have offered furnace designs for the 

production of this kind of ash. After Mehta described the 

effect of pyro-processing parameters on the pozzoloanic 

reactivity of RHA, Pitt designed a fluidised bed furnace 

for controlled combustion of RHA. 4 Until recently, the 

RHA generated by the processes that are on the market 

had 3% or more graphitic carbon which gave the dark 

color to the material, restricting its use in architectural 

applications where color is the driver and leads to 

excessive demand from water and chemical admixtures 

in order to maintain appropriate slump and other 

properties in concrete. 

Recently, researchers in the USA have developed a new 

continuous production process of manufacturing RHA in 

which the rotary tube furnace was maintained in aerobic 

conditions at 700 o C with a residence time of 40 min to 

obtain off-white RHA with a carbon content of less than 

0.3%. 5 Another associated group has achieved this feat 

under a different set of conditions; using a rotary kiln 

furnace in which incineration of rice husk was done 

under oxidizing conditions at 400 o C for 4 h. 6 

Generally, the findings reported in the literature highlight 

the role of RHA as an effective pozolana that increases 

4. Mehta P.K., Siliceous ashes and hydraulic cements prepared therefrom, 

Belgium Patent 802, 909 (1973). 

5. Ferraro R.M., Nanni A, Vempati R.K. and Matta F., Carbon neutral off-white 

rice husk ash as a potential white cement replacement , Journal of Materials 

in Civil Engineering, October 2010, pp. 1078 -1083. 

6. Harish K.V, Rangaraju P.R and Vempati R.K., Fundamental Investigations 

into Performance of Carbon –Neutral Rice Husk Ash as Supplementary 

Cementitious Material, Transport Research Record: Journal of Transportation 

Research Board, No 2164, Transportation Research Board of the National 

Academies, Washington, D.C., 2010, pp 26-35. 

7. An V. and Ludwig H.-M, Using rice husk ash and ground granulated blastfurnace 

slag to replace silica fume in UHPC, Performance –based Specification 

for Concrete Proceedings , Editors Frank Dehn and Hans Beushausen,, MFPA 

Leipzig GmbH, Institute for Material Research and Testing, Leipzig, June 

2011, pp 80-89 

The IndIan ConCreTe Journal MARCH 2012 

Weight composition 

strength and durability of Portland cement mixtures 

and that the performance of RHA is very comparable to 

that of silica fume. However, the compressive strength 

in such reports rarely cross 50 MPa. 6 

A paper published in 'Performance-based specifications for 

concrete' suggests that RHA can be a good supplementary 

material to produce ultra high performance concrete 

with compressive strength of 120 MPa or more. 7 The 

typical weight composition is given in the Figure. 

(Water/binder ratio range : 0.21 -0.23. The mix includes 

1 % fibres by volume of mixture. Volume of water to 

volume of fine material ratio was 0.50 to 0.55.) 

The combination of RHA and ground granulated blast- 

furnace slag (GGBS) improved not only the workability 

but also compressive strength. 

The use of RHA in cement production is essentially 

undertaken in small village units. However, the 

potential for this material is quite clear from the above 

example. Cost reduction, performance , durability and 

environmental concerns are the primary characteristics 

that can make RHA a valid alternative to partially 

substitute Portland cement. 

quartz sand, 42%

News & Events 

Global Demand for 

Construction Aggregates 

to Exceed 48 Billion Metric 

Tons in 2015 

The global market for construction 

aggregates is expected to increase 5.2 

percent per year through 2015 to 48.3 

billion metric tons. This represents 

a slower rate of growth than during 

the 2005-2010 period, reflecting a 

moderation in aggregates-intensive 

nonbuilding construction activity. 

Nevertheless, demand for construction 

aggregates will still post solid gains 

from 2010 to 2015. The Asia/Pacific 

region will register the largest increases 

in product sales, as construction activity 

will rise rapidly, particularly in China 

and India. China alone will account 

for half of all new aggregates demand 

worldwide during the 2010-2015 period. 

These and other trends are presented 

in World Construction Aggregates, a 

new study from The Freedonia Group, 

Inc., a Cleveland-based industry market 

research firm. 

Eastern Europe and the Africa/Mideast 

region are also expected to undergo 

significant growth in consumption of 

construction aggregates, stimulated 

by infrastructure development projects 

and strong growth in general economic 

activity. While the Central and South 

America market will climb at a somewhat 

slower pace, aggregates suppliers will 

benefit from gains in regional construction 

spending. 

Expansions in demand in developed 

parts of the world -- the US, Canada, 

Japan, Western Europe, South Korea 

and Australia -- will not be as strong 

as in most industrializing areas. This 

is primarily due to the already welldeveloped 

infrastructures found in 

these countries and the construction 

methods utilized, which tend to feature 

less concrete. 

Demand for crushed stone, sand and 

gravel products will post similar growth 

rates of just over five percent per 

year through 2015. As in 2010, sand 

will continue to make up the largest 

portion of global sales, followed closely 

by crushed stone and then gravel. 

Due to more restrictive land use and 

environmental regulations, as well as 

the depletion of natural aggregates 

reserves, sales of recycled, secondary 

and other aggregates will climb at an 

above-average pace during the 2010- 

2015 period. However, despite projected 

growth of 7.1 percent per year over this 

span, these products will continue to 

play a small role in world markets due 

World construction aggregates demand (million dollars) % Annual Growth 

Item 200 2010 201 200 -2010 2010-201 

Construction aggregates demand 27300 37400 48300 6. .2 

North America 3280 3010 3710 -1.7 4.3 

Western Europe 2920 2630 3050 -2.1 3.0 

Asia/Pacific 16000 24750 32600 9.1 5.7 

Other 5100 7010 8940 6.6 5.0 

© 2012 by The Freedonia Group, Inc. 

to quality concerns and limitations in the 

availability of feed material. 

World Construction Aggregates 

(published 01/2012, 334 pages) is 

available for $5900. 

For more details, please contact: 

Corinne Gangloff 

The Freedonia Group, Inc., 

767 Beta Drive, Cleveland, 

OH 44143-2326, USA 

Tel: 440.684.9600, 

Fax 440.646.0484 

e-mail: pr@freedoniagroup.com. 

Web: www.freedoniagroup.com. 

AARCV 2012 

The School of Architecture and the 

Department of Civil Engineering, 

M. S. Ramaiah Institute of Technology, 

Bangalore, is organising an international 

conference on Advances In Architecture 

and Civil Engineering (AARCV – 2012) 

during June 21 to 23, 2012. 

Advances in Civil Engineering and 

Architecture are the order of the day 

with the rapid industrialization and 

urbanization seen in developed and 

developing nations. Innovative design and 

construction practices are challenging 

tasks to the architects and engineers 

to meet the ever growing demands 

of the society. Keeping these in mind 

the present international conference 

is being organized. The themes of 

the conference cover architectural, 

structural, geotechnical, transportation, 

environmental and urban planning 

disciplines. 

The event is targeted at architects, 

engineers, infrastructure and project 

managers, academicians, consultants, 

designers, builders, equipment and 

materials manufacturers, govt., 

semi govt., private and autonomous 

MARCH 2012 The IndIan ConCreTe Journal

organisations, research scholars and 

students. 


The Convenor 

Dept. of Civil Engineering / Architecture 

M. S. Ramaiah Institute of Technology 

MSR Nagar, MSRIT Post, Bangalore 560 054 

Tel: 080-23600822, 23606934 

Fax: 23603124, 23606616 

Powder & Bulk Solids India 

2012 

Powder & Bulk Solids India 2012, 

formerly known as Bulk Solids India, is 

a conference and exhibition, that will be 

held from 13th to 15th March, 2012 at 

Ahmedabad. 

Powder and Bulk Solids India 2012 is a 

member of the international Powder & 

Bulk Network. The event will present 

basic processing technologies for powder 

and bulk materials, plant engineering and 

processing components, as well as a wide 

range of specialised products related to 

the chemical, food, pharmaceutical, 

cement, mining and ports industry 

At the powder section of the exhibition, 

manufacturers and suppliers of 

mechanical processing and material 

handling technologies will be showcasing 

solutions for conveying, transporting, 

storing and size reduction as well as 

screening and mixing and the granulation 

for powder and bulk solids in the various 

industries. 

There conference and workshop that will 

focus on two main topics: “From Port to 

Plant. Challenges in Power Generation”, 

which addresses the bulk sector, and 

“Powder & Granules in Chemicals 

and Plastics Production – Innovative 

Approaches for Optimum Results” 

addressing the powder sector. 


Ms. Priya Sharma 

Indo-German Chamber of Commerce 

New Delhi, India 

Tel: +91-11-47168830 

E-mail : priya@indo-german.com 

Web: www.powderbulksolidsindia.com 

6 


Pre-Engineered Buildings 

The Indian Buildings Concrete is holding 

its mid term seminar on the theme ‘‘Pre- 

Engineered Buildings and Innovative 

Techniques in Construction Industry’’ 

during May 25-26, 2012 at Kolkata. 

The sub-themes of the event are as 

follows:- 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

Scope for use of Pre- 

Engineered Buildings; 

Pre-Engineered Metal 

Buildings; 

Pre-Engineered RCC Buildings; 

Innovative Techniques in 

Construction Industry – Design 

Related; 

Innovative Techniques 

in Construction Industry 

– Construction Related; 

Innovative Techniques 

in Construction Industry 

– Maintenance Related and 

Case Studies 

An abstract of the paper not exceeding 

200 words may please be sent to us, 

so as to reach us by March 15, 2012. 

We expect full paper to be received 

within three weeks of communication of 

acceptance of the abstract. 


P.S. Chadha 

Indian Buildings Congress 

Sector VI, R.K. Puram, 

New Delhi 110022 

Tel: 011-26169531, 26170197 

Fax: 011-026196391 

Website: www.ibc.org.in 

E-mail: info@ibc.org.in 

Indian carbon nanotubes in 

Forbes 30 listing 

Vivek Nair, 23, founder, Damascus 

Fortune, a Mumbai-based start-up 

says "I got listed in Forbes’ ‘30 Under 

30’ under the energy category. Carbon 

nanotubes are the strongest and stiffest 

material known, with a strength-toweight 

ratio 117 times greater than 

steel. Our company has developed 

a technology that converts carbon 

emissions from automotive and industrial 

plants to produce carbon nanotubes and 

nanofibres. One needs to have courage 

to initiate things. Due to the cost, I had 

to face adminstrative hurdles to make 

carbon nanotubes in the university 

laboratory. So, I converted flue gas 

from Maruti Modern rice mill, and 

Neyveli Lignite Corporation’s thermal 

power station to carbon nanotubes 

and nanofibres. It was a miracle. I 

was born in Kerala, and completed 

bioengineering in T amil Nadu. Now a 

doctoral research student at Singapore’s 

Nanyang Technological University. I 

am, along with 15 people, working on 

developing the technology and finding 

new applications such as strong body 

parts of buildings, automobiles, ships 

and aircraft. Our aim is to install the 

technology in almost all flue gas-emitting 

industrial plants in India, Middle East, 

Africa, Asia Pacific, Europe and US. 

This will help reduce global warming on 

a large scale and monetise the carbon 

nanotubes." 

– The Economic Times 03.02.2012 

Global Cement Expo 2012 

Global Cement is pleased to announce 

the launch of the Global Cement Expo 

2012 (www.GlobalCementExpo.com), 

which will take place at the Targi w 

Krakowie exhibition centre in Krakow, 

Poland, on 14-15 June 2012. 

The Global Cement Expo will include a 

free seminar programme with parallel 

sessions that will cover wear and 

maintenance, alternative fuels including 

RDF and MSW, waste heat recovery 

options (ORC and Kalina cycle), 

electrical energy efficiency, refractories, 

quality control, environmental impact 

abatement, mortars and alternatives 

to OPC. 


Dr. Robert McCaffrey 

PRo Publications International Ltd 

First Floor, Adelphi Court 

1 East Street, Epsom, Surrey 

KT17 1BB, UK 

e: rob@propubs.com 

t: +44-1372840951

Some studies on the effect of 

carbonation on the engineering 

properties of concrete 

This paper reports the effect of carbonation on three 

different grades of concrete each cured for 28, 56, 90 

and 120 days. Carbonation was carried out by placing 

the specimens in a chamber of 10% carbon dioxide for 

150 days. The tests included compressive strength 

and porosity measurement using a compression 

testing machine and mercury intrusion porosimeter 

respectively. In addition, electrical conductivity was 

measured following ASTM C 1202. The results indicate 

that carbonation increases the compressive strength and 

decreases the porosity and electrical conductivity of the 

specimen. The results give factors for estimating concrete 

performance between carbonated and non-carbonated 

specimens. 

Keywords: Concrete, carbonation, electrical conductivity, 

porosity, and laboratory studies. 

Introduction 

It is well known that carbonation affects the durability 

of concrete, involves CO 2 reaction with the hydration 

products of cement to reduce the pH of the concrete 

pore solution from about 12 to less than 9 and causes 

B.B. Das, S.K. Rout, D.N. Singh and S.P. Pandey 

the formation of calcium carbonate. 1-3 The following 

equation describes the reaction. 4 

MARCH 2012 The IndIan ConCreTe Journal 

......(1) 

Researchers have found that the reaction consumes 

Ca(OH) 2 from the hydrated paste as calcium silicate 

hydrates (CSH) liberating CaO to maintain the 

equilibrium. In addition, concrete‘s residual unhydrated 

cement compounds such as C 3 S and C 2 S react with CO 2 

in the presence of H 2 O further carbonating the concrete. 5 

In this manner, the reaction destroys the passivity of 

concrete making it prone to corrosion. The literature 

has several reports on changes in concrete’s physicomechanical 

and durability properties resulting from 

carbonation. 6-13 

Concrete’s conductivity is used to determine its 

service life in corrosive environments. Both American 

Association of State Highway and Transportation 

Officials (AASHTO) and American Society for Testing 

and Materials (ASTM 2008) have standardised tests 

for electrical conduction (Q). Rapid chloride ion

permeability test (RCPT) is one such well known test 

that measures the cumulative electrical charge passing 

through a specimen subjected to a 60 V potential for 6 

hours. 

This paper attempts to understand the influence of 

carbonation on the compressive strength, electrical 

conductivity and microstructure of concrete. 

Materials 

Ordinary Portland cement (OPC) conforming to 

ASTM Type-I cement was used in this study. The 

fine-aggregates conformed to Zone-III of BS 882 and 

had a fineness modulus of 1.99. 14 The maximum size 

of coarse-aggregates was 20 mm. Table 1 presents the 

specific gravity of these materials determined using 

an ultra-pycnometer (make Quantachrome, USA). The 

particle-size distribution of the cement was determined 

using a Granulometer (Model No. 920, CILAS), which 

works on the principle of laser diffraction. Figure 1 

shows the particle-size distribution of cement and that 

of fine and coarse aggregates determined according to 

ASTM C 136-01. 15 

The fineness of the cement was determined using 

Blaine’s air-permeability apparatus following ASTM C 

204-00 (Table 1). 16 

The chemical composition of OPC was determined 

using an X-Ray Fluorescence setup and the results are 


presented in Table 2. The mineralogical composition 

of the OPC was determined with the help of an X-Ray 

diffraction spectrometer (make D8 Advance-Bruker, AXS 

Germany), which employed a graphite monochromator 

and Cu-Kα source. The sample was scanned from 5° 

to 60°. The various compounds present in the cement 

composition were identified with the help of TOPAS 

software (Table 3). 17 

Table 1. Physical properties of the materials used in the 

study 

Material Specific 

gravity 

Fineness, 

m 2 /kg 

Ordinary Portland Cement 3.16 294 

Coarse 

aggregate 

Fine aggregate 2.71 NA 

NA - Not applicable 

10 mm 2.79 NA 

20 mm 2.77 NA 

Table 2. Chemical composition of the ordinary Portland 

cement 

Oxide % by weight 

Al2O3 5.55 

CaO 60.46 

Fe2O3 4.98 

K2O 0.487 

MgO 1.27 

Na2O 0.232 

SiO2 20.89 

(SiO2 +Al2O3 +Fe2O3 ) 31.42 

(SiO2 +Al2O3 ) 26.44 

LOI 2.26 

Table 3. Phases present in the ordinary Portland cement 

Compound % by weight 

C 3 S 59.38 

C 2 S 24.58 

C 3 A 5.11 

C 4 AF 10.37 

Table 4. Mix proportions for different grades of 

concrete 

Mix 

Designation 

Cement 

content, 

kg/m 3 

w/c Mix proportion 

(OPC: W: FA: CA) 

Compacting 

factor 

C1 300 0.55 1:0.55:2.06:4.37 0.90 

C2 320 0.45 1:0.48:1.98:4.60 0.84 

C3 360 0.40 1:0.40:1.88:4.59 0.82

Testing methodology 

The details of the mix and their designation are presented 

in Table 4. The mixing was done in a rotary mixer for 

about 2 minutes. The desired compaction of concrete was 

achieved with the help of a table vibrator. The samples 

were first cured at 95±5% relative humidity and 27±2 ˚C. 

After 24 h, the cubes were de-molded and cured under 

water at 27±2˚C. Four curing periods (t = 28, 56, 90 and 

120 days) were chosen for this study. The compressive 

strength of the cubes at the end of each curing period was 

determined by employing an automatic compression 

testing machine. Table 5 presents the results. 

Cubes of 150 mm and 100 mm were used for determining 

the compressive strength (f c ) and the carbonation depth 

(d), respectively. In addition, 150 mm×150 mm×700 

mm beams ( one beam or more than one ?) were cast 

for extracting several cylindrical cores for conducting 

the rapid chloride ion penetration test; before and after 

carbonation. 

The porosity (η) of concrete was determined with the 

help of an auto scan mercury intrusion porosimeter 

which operated up to 60,000 psi (414 MPa). The technique 

involves the intrusion of mercury (Hg) at high pressure 

into a specimen through the use of a penetrometer. Hg 

does not penetrate into the pores until such a pressure 

is applied that forces the liquid into the pores. The 

ratio between the applied pressure and the size of the 

pores is defined by Washburn’s equation, where the 

pore diameter is inversely proportional to the applied 

pressure: the higher the pressure, the smaller are the 

pores into which it is possible to intrude the liquid. The 

mercury intrusion porosimetry procedure for concrete 

samples was published earlier. 18 

accelerated carbonation studies 

Cured cubes and cores extracted from the beams were 

taken out of the curing tank and stored at 60% relative 

humidity and 27˚ C for 15 days to stabilise their internal 

humidity. 19 These specimens were next transferred to an 

a chamber containing 10% concentration of CO 2 at 27˚ C 

Table 5. Compressive strength of different grades of 

the concrete 

Curing period 

Compressive Strength, MPa 

days 

C1 C2 C3 

28 31.76 42.81 51.20 

56 38.06 46.14 53.82 

90 39.44 46.25 54.13 

120 40.12 47.82 56.48 

and 65% relative humidity for accelerated carbonation. 

(The CO 2 concentration in the air is about 0.03%). To 

provide an uninterrupted ingress of CO 2 , the specimens 

were placed on a wire mesh. After 150 days of exposure 

(T=150), cubes were taken out of the chamber and cut 

into two equal parts in the direction perpendicular to 

the plane of casting. Next, the depth of carbonation was 

determined by spraying 1% phenolphthalein in 70% 

ethyl alcohol that changes from colourless to purple 

when pH is >9. 20 

So the colour of the carbonated portion of the specimen 

remained unchanged, while that of the uncarbonated 

portion became purple. Based on this, the average 

depth of the carbonation in the cubes (corresponding 

to the four cut faces of the cube) was measured. The 

average of three results gave the carbonation depth d 

for a particular grade of concrete. The carbonated cores 

were subjected to rapid chloride ion permeability test 

as described below. 

rapid chloride ion penetration test 

The test apparatus used was from Control, Italy and 

conformed to ASTM C-1202. 21 The test method involved 

obtaining a 100 mm diameter core or cylinder sample 

from the concrete being tested. A 50 mm specimen was 

cut from the sample. The side of the cylindrical specimen 

was coated with epoxy, and after the epoxy dried out, it 

was put in a vacuum chamber for 3 hours. The specimen 

was vacuum saturated for 1 hour and allowed to soak 

for 18 hours. It was then placed in the test device. The 

left-hand side (–) of the test cell was filled with a 3% 

NaCl solution. The right-hand side (+) of the test cell 

was filled with 0.3N NaOH solution. The system was 

then connected and a 60-volt potential was applied for 6 

hours. Readings were taken every 30 minutes. At the end 

of 6 hours the sample was removed from the cell and the 

amount of coulombs passed through the specimen was 

calculated. Table 6 shows the chloride ion permeability 

following ASTM C 1202. 

Table 6. Chloride Ion permeability based on charge 

passed (ASTM C 1202) 

Charge passed, 

Coulomb 

Chloride 

permeability 

Typical concrete 

>4000 High High w/c (>0.60) 

2000-4000 Moderate Moderate w/c (0.40-0.50) 

1000-2000 Low Low w/c (

The average charge Q (in Coulomb) from three identical 

cores of a specific grade of concrete was taken as the 

electrical conductivity of that grade of concrete. 

results and discussions 

Carbonation depth 

Table 7 presents the carbonation depth results. The 

carbonation resistance of the concrete can be expressed 

using Fick’s first law of diffusion as under 11 

d = K (t) 0.5 

10 


......(2) 

where, d is the carbonation depth in mm and t is 

the curing period in weeks and K is the carbonation 

coefficient expressed in mm/weeks 0.5 . 

Table 7. Carbonation depth for different grades of 

concrete specimens 

t 

(days) 

Table 8. Compressive strength of different grades of 

non-carbonated and carbonated concrete 

t 

(days) 

T=150 

Carbonation depth, d (mm) % reduction 

C1 C2 C3 C1 C2 C3 

28 28.2 24.2 19 NA NA NA 

56 25 22.1 16.5 11.35 8.68 13.16 

90 22.2 19 13 21.28 21.49 31.58 

120 18.6 15.2 10 34.04 37.19 47.37 

NA - Not applicable 

f c (MPa) 

T = 0 (Non- carbonated 

concrete) 

T = 150 (Carbonated 

concrete) 

C1 C2 C3 C1 C2 C3 

28 31.76 42.81 51.20 41.79 54.19 64.00 

56 38.06 46.14 53.82 49.43 56.96 65.63 

90 39.44 46.25 54.13 51.22 56.40 66.01 

120 40.12 47.82 56.48 50.15 57.61 68.88 

Table 9. Ratio of the properties of non-carbonated 

concrete to carbonated concrete 

t 

fc Q η 

(Days) 

C1 C2 C3 C1 C2 C3 C1 C2 C3 

28 0.76 0.79 0.80 3.24 3.06 2.96 1.04 1.12 1.16 

56 0.77 0.81 0.82 2.89 2.86 2.78 1.04 1.18 1.18 

90 0.77 0.82 0.82 2.75 2.71 2.61 1.05 1.20 1.20 

120 0.80 0.83 0.82 2.65 2.62 2.56 1.10 1.20 1.23 

Figure 2 is a plot of carbonation coefficient and curing 

period at three levels of water to cement ratios. This 

figure suggests that w/c ratio has a strong influence 

on the carbonation resistance of concrete. With w/c 

decreasing from 0.55 to 0.40 carbonation coefficient 

K reduced by a factor of 3. The data on carbonation 

depth and curing in Table 7 suggests that curing period 

plays an important role in developing the carbonation 

resistance of concrete. The reduction in carbonation 

ranged from about 8% to about 47%. Considering the 

28 day specimen as control, the carbonation depth in the 

specimen of w/c ratio 0.55 reduced by 11.35%, 21.28% 

and 34% at 56, 90 and 120 day respectively. 

Compressive strength 

Table 8 presents the compressive strength of both 

carbonated and non carbonated specimens. From this 

table, it is evident that carbonation leads to an increase 

in compressive strength. The formation of CaCO 3 

which is known to occupy more volume than Ca(OH) 2 , 

reduces the porosity in concrete resulting in a higher 

compressive strength. The results show the strength 

improvement is more in the case of low strength 

concrete. The compressive strength of the carbonated 

concretes increased as compared to the non carbonated 

concretes. Table 9 shows that the compressive strength 

ratio of non carbonated concrete to carbonated concrete 

at 28 days is lower by 0.76, 0.79, and 0.80 for w/c ratio 

of 0.55. 0.45 and 0.40 respectively. These ratio reduction 

can be considered as the factors to be used to determine 

the actual compressive strength of carbonated concretes 

in structures. However, Table 9 data is not a clear 

function of curing period t. It means the carbonation 

has less influence on the compressive strength if the

concrete is cured for a longer time. A lower concrete 

porosity resulting from a longer curing time explains 

this observation. 

electrical conductivity 

Figures 3 and 4 show the electrical conductivity of non 

carbonated and carbonated specimens respectively. The 

specimens' curing period and water to cement ratios 

were varied. It can be observed from the figures that 

the electrical conductivity of the carbonated concrete 

decreased by a factor of 3 as compared to that of the 

non-carbonated concrete. Figure 4 suggests that the 

electrical conductivity deceased as the grade of concrete 

increased. It can also be noted from Table 9 that the 

electrical conductivity of carbonated concrete cured for 

28 days decreased by a factor of 3.24, 3.06 and 2.96 for 

w/c ratio of 0.55, 0.45 and 0.40 respectively. The reducing 

chloride ion penetration indicates that carbonation 

of higher grades of concrete results in decreasing the 

specimen’s porosity. It can be observed from Figure 4 

that the electrical conductivity is inversely proportional 

to curing period (t). At the w/c ratio of 0.40 the electrical 

conductivity of carbonated concrete decreased by a 

factor of 2.96, 2.78, 2.61 and 2.56 for curing period of 

28, 56, 90 and 120 days respectively. So carbonated 

specimens with longer curing periods show reduced 

electrical conductivity. 

Porosity 

Figures 5 and 6 show the effect of carbonation on the 

porosity of non-carbonated and carbonated specimens 

respectively. It can be observed from the figures that 

the porosity is inversely related to w/c ratio for both 

carbonated and non-carbonated concretes. The porosity 


11

eduction factors of 28 day specimens was 1.04, 1.12 and 

1.16 times for w/c ratio of 0.55, 0.45 and 0.40 respectively. 

The factors for other specimens are given in Table 9. 

Based on the porosity of non-carbonated specimens 

cured for 28 days, the porosity of both carbonated and 

non carbonated concrete decreased with increasing 

curing period as tested. In comparison to the noncarbonated 

concrete, for the w/c ratio of 0.40 the porosity 

for carbonated concrete decreased by a factor of 1.16, 

1.18, 1.20 and 1.23 at 28 days, 56 days, 90 days and 120 

days respectively (Table 9). 

Conclusions 

The following conclusions can be drawn from this 

experimental work: 

12 

1. 

2. 

3. 

Both carbonation coefficient and depth decreased 

with the increase in the curing period. The 

compressive strength increased with the 

increase in the curing period and decrease in the 

water /cement ratios. 

Under these conditions of w/c ratio and curing 

periods, the electrical conductivity of the 

carbonated concrete decreased by a factor of 3 

compared to the non-carbonated specimen. 

As the curing period increased, the porosity 

decreased in both carbonated and non carbonated 

concrete specimens. Also there was a reduction in 

the porosity with the lowering of water/cement 

ratios. The factor of reduction was different for 

carbonated and non-carbonated specimens. 

The difference could be due to the extent of 

carbonation and resulting CaCO 3 formation. 

references 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

Haque, M. N., and Kawamura, M., “Carbonation and Chloride-induced 

Corrosion of Reinforcement in Fly Ash Concretes,” ACI Materials Journal, 

Vol. 89 (1), 1993, pp. 41-48. 

Ihekwaba, N. M., Hope, B. B., and Hansson, C. M., “Carbonation and 

Electrochemical Chloride Extraction from Concrete”, Cement and Concrete 

Research, Vol. 26 (7), 1996, pp. 1095–1107. 

Basheer, P. A. M., Chidiac, S. E., and Long, A. E., “Predictive Models for 

Deterioration of Concrete Structures”, Construction and Building Materials, 

Vol. 10, 1996, pp. 27–37. 

Johannesson, B., and Utgenannt, P., “Microstructural Changes Caused by 

Carbonation of Cement Mortar”, Cement and Concrete Research, Vol.31, 2001, 

pp. 925-931 

Claisse, P. A., El-Sayad, H., and Shaaban, I. G., “Permeability and Pore 

Volume of Carbonated Concrete”, ACI Materials Journal, Vol.96 (3), 1999, 

pp. 378-381. 

Jerga, J., “Physico-mechanical Properties of Carbonated Concrete’, 

Construction and Building Materials, Vol.18, 2004, pp. 645-652. 

Silva, C. A. R., Reis, R. J. P., Lameiras, F. S. And Vasconcelos, W. L., 

“Carbonation-Related Microstructural Changes in Long-Term Durability 

Concrete”, Materials Research, Vol. 5 (3), 2002, pp. 287-293. 


8. Xiao, J., Li, J., Zhu, B., and Fan, Z., “Experimental Study on Strength and 

Ductility of Carbonated Concrete Elements”, Construction and Building 

Materials, Vol. 16, 2002, pp. 187-192. 

9. Chang, C. F., and Chen, J. W., “Strength and Elastic Modulus of Carbonated 

Concrete”, ACI Materials Journal, Vol. 102 (5), 2005, pp. 315-321. 

10. Song, H. W., and Kwon, S. J., “Permeability Characteristics of Carbonated 

Concrete Considering Capillary Pore Structure”, Cement and Concrete 

Research, Article in press. 

11. Valcuende,M. and Parra,C., “Natural Carbonation of Self Compacting 

Concrete”, Construction and Building Materials, Vol. 24 (5), 2010, pp. 848- 

853. 

12. Vaysburd, A. M., Sabnis, G. M., and Emmons, P. H., “Concrete Carbonation— 

A Fresh Look,” Indian Concrete Journal, V. 67, No. 5, May 1997, pp. 215-220. 

13. Chi, J.M., Huang, R., and Yang, C. C., “Effects Of Carbonation On Mechanical 

Properties And Durability Of Concrete Using Accelerated Testing Method”, 

Journal of Marine Science and Technology, Vol. 10, No. 1,2002, pp. 14-20. 

14. ______BS 882. “Specification for Aggregates from Natural Source for 

Concrete”, British Standards Institution, London, 1992. 

15. ______ASTM C 136-01, “Standard Test Method for Sieve Analysis of Fine 

and Coarse Aggregates, Annual book of ASTM Standards”, Vol. 04.02, ASTM, 

West Conshohocken, PA, 2002. 

16. ______ASTM C 204-00, “Standard Test Method for Fineness of Hydraulic 

Cement by Air-Permeability Apparatus”, Annual book of ASTM Standards, 

Vol. 04.01, ASTM, West Conshohocken, PA, 2002. 

17. TOPAZ 2.1, “Diffract Plus”, Bruker AXS GmbH, Karlsruhe, Germany, 2003. 

18. Das, B. B., Singh, D. N., and Pandey, S. P., “Characterization of Concrete 

by three ASTM Specified Techniques for Determination of Pore Volume”, 

Indian Concrete Journal, December 2010. 

19. Sulapha, P., Wong, S. F., Wee, T. H., and Swaddiwudhipong, S., “Carbonation 

of Concrete Containing Mineral Admixtures”. Journal of Materials in Civil 

Engineering, ASCE, Vol. 15 (2), 2003, pp. 134-143. 

20. ______CPC-18. “Measurement of Hardened Concrete Carbonation Depth”, 

Materials and Structures, Vol. 17 (6), 1988, pp. 453-455. 

21. ______ASTM C 1202, “Standard test method for electrical indication of 

concrete’s ability to resist chloride ion penetration.” Annual book of ASTM 

Standards, Vol. 04.02, ASTM, West Conshohocken, PA, 2002. 

Dr. B.B. Das is an Associate Professor at KIIT 

Deemed University, Bhubaneswar, He has been 

a Post-Doctoral Research Associate and Adjunct 

Professor in the Department of Civil Engineering 

at Lawrence Technological University, Southfield, 

Michigan, USA. His areas of research include 

microstructure characterization of materials, nondestructive 

testing of concrete, corrosion of reinforcement 

and durability studies on concrete. 

S.K. Rout is a Graduate Student at the 

Department of Civil Engineering, Lawrence 

Technological University, Southfield, Michigan, 

USA. His present area of research interest is in 

structural engineering and structural materials. 

Dr. D.N. Singh holds a Civil Engineering from 

IIT Kanpur and PhD. in Geotechnical Engineering. 

He is a Professor in the Department of Civil 

engineering, Indian Institute of Technology, 

Mumbai. His major research focus is in the field 

of Environmental Geotechnology. 

Dr. S.P. Pandey holds a PhD in solid-state 

chemistry from Gorakhpur University, U.P. He is 

Vice President of Central R&D, UltraTech Cement 

Ltd., Mumbai. His research interests are in 

Cement chemistry and material science.

Review of inspection practices, health 

indices, and condition states for 

concrete bridges 

A bridge is a structure built to span physical obstacles 

such as a body of water, valley, road or railway for the 

purpose of providing passage over the obstacle. A weak 

bridge can either reduce the load carrying capacity or 

compromise on safety, hindering the flow of traffic and 

affecting the economy. Hence, it is necessary to maintain 

the traffic-worthiness of bridges with requisite levels of 

safety and serviceability. However, those responsible 

for such works often feel that the funds made available 

to them are insufficient. One of the ways to address 

this challenge is to utilise the available resources in an 

optimal manner using scientific methods and tools. 

Instituting a bridge management system or BMS is a 

good way for managing design, construction, operation 

and maintenance of bridges. Many countries have 

developed such systems. A BMS guides the decision 

making processes regarding the maintenance, planning 

by ascertaining the present condition and pointing out 

the immediate maintenance requirements of a bridge. 

It does not wholly rely on the physical condition of 

bridges, which is often described by discrete condition 

states on the basis of visual inspection. Since the results 

of visual inspection are subjective and vary according 

to the knowledge and judgment of the bridge inspector, 

most BMS systems make use indices as one of the tools 

for decision making. 

Keywords: Bridge management system, bridge inspection, 

condition states, bridge health index 

Sanjay S. Wakchaure and Kumar N. Jha 

This paper compares the condition states and bridge 

indices used by various countries. Included in the paper 

are definition of a bridge, types of inspection, bridge 

health index, and condition states. The paper attempts 

to point out the limitation and constraints in BMS for 

adopting them universally and evolving a structure for 

comprehensive condition states and bridge index. The 

study reveals that there is no unanimity among bridge 

authorities across the globe regarding length of a bridge, 

the condition states and bridge indices. A comprehensive 

and universal categorisation of condition scales and 

bridge index would go a long way in improving the 

understanding about the performance of concrete 

bridges regardless of their location. 

Introduction 

The history of bridges is almost as old as that of human 

civilisation. Bridges have greatly contributed to the 

human endeavour by providing passage over obstacles 

such as a body of water, valley, road or railway and 

improving mobility. India has one of the largest road 

and rail networks in the world, with the total road 

length being 4.1 million kilometers (http://www.morth. 

nic.in), and rail length being 64,099 km (http://www. 

indianrailways.gov.in). Both roads and railways run 

across the length and breadth of the country, connected 

by many bridges, negotiating the varied terrains and 

environmental conditions in the country. 


13

Table 1. Minimum length to be traversed to be classified as a bridge 

There are more than 92, 000 bridges and over 1.1 million 

culverts (length ≤ 6 m) of different types along Indian 

roads. 1 Out of the 92,000 bridges, about 14,500 bridges 

are on the National Highways. Out of these, 1713 

bridges are in a ‘distressed’ condition and require 

repair/rehabilitation, while 2018 bridges are old, weak 

and need reconstruction. 2 

Like roads, bridges are inseparable parts of the Indian 

Railways. There are about 1.27 million bridges of 

different types and varying spans on Indian railway 

tracks. About 40 percent of these bridges are over 100 

years old and 16 percent are reported to be deficient, 

requiring rehabilitation and strengthening. 3,4 

Bridge owners all over the world face difficulties in 

maintaining bridges with the available funds. Before 

allocating resources for the maintenance of bridges, it 

is necessary to ascertain their present condition, their 

immediate and future maintenance requirements. This 

need has led to the development of bridge management 

system (BMS). BMS consists of various scientific methods 

and tools for efficient allocation of funds. Reliable data 

on the history of bridge condition and maintenance are 

of prime importance to the development of this system. 

The assessment of bridge condition is mostly based on 

visual inspection by inspectors and is expressed in terms 

of discrete condition states which often dependent on 

the judgment and experience of the inspector. Hence, 

the development of a method that does not solely 

depend on subjective data is essential. 5 The application 

of condition states in the assessment of bridges in BMS 

and decision making has not been much attended 

to by researchers. 6 Further, there is no established 

methodology or systematic approach in this regard 

though bridge engineers and decision makers routinely 

face the problem of prioritizing the maintenance needs. 

Ranking of bridges for the purpose of maintenance very 

often follows a personal judgment. 6 

Considering the importance of inspection, bridge health 

index and condition states in efficient allocation of funds, 

this paper embarks on reviewing the practices followed 

in different parts of world based on the available 

literature. As it will be seen in subsequent sections there 

is a wide disparity in the manner in which bridges are 

maintained and the funds are allocated. In fact there 

14 

Country Austria Denmark France Norway Slovenia United Kingdom United States India 

Length in ‘m’ >2 ≥ 5 > 2 m ≥ 2.5 ≥ 5 > 3 > 6.10 > 6 


is no unanimity in the bridge definition itself to start 

with. The review is aimed at comparing the current 

practices, pointing out the limitations and constraints 

in the existing practices and thereby proposing suitable 

recommendations. 

Bridge definition 

In order to be classified as a bridge, a structure should 

be of a minimum length. 7 The Indian Roads Congress 

defines a bridge as a structure having a length of more 

than six metres and meant for carrying vehicular 

traffic across rivers, canals, viaducts, structures for 

interchanges including underpasses and flyovers across 

the highway/railways, aqueducts/siphon. 8 National 

Bridge Inspection Standards published in the Code 

of Federal Regulations (23 CFR 650.3), USA, defines a 

bridge as ‘a structure including supports erected over a 

depression or an obstruction, such as water, highway, or 

railway; having a track or passageway for carrying traffic 

or other moving loads, and having an opening measured 

along the centre of the roadway of more than 20 feet 

(6.1 m) between under copings of abutments or spring 

lines of arches, or extreme ends of openings for multiple 

boxes; it may also include multiple pipes, where the clear 

distance between openings is less than half of the smaller 

contiguous opening. 9 In simple words, a bridge can be 

defined as a structure meant for carrying vehicular traffic 

across an artificial or natural obstruction. Although a 

structure has to be of a minimum length in order to be 

classified as a bridge, there is no unanimity on the exact 

length. The minimum length of bridge specified by 

bridge authorities varies from two to six metres 7 . Table 1 

gives the minimum bridge lengths prescribed in select 

countries. According to IRC: 5-1998, bridges having 

length up to 60 m are classified as minor bridges while 

bridges having length more than 60 m are classified as 

major bridges. 

Bridge management 

Bridges can be regarded as a separate infrastructural 

facility owing to their distinct importance. Infrastructure 

management is the process by which agencies monitor, 

maintain and repair deteriorating facilities within 

stipulated budgets so as to improve their performance. 10 

Federal Highway Administration manual (USA) defines 

‘asset management’ in the following manner. 11

“Asset management is a systematic process of 

maintaining, upgrading, and operating physical assets 

cost-effectively. It combines engineering principles with 

sound business practices and economic theory and it 

provides tools to facilitate a more organized, logical 

approach to decision-making”. 

A weak bridge in a network of roads leads to either 

reduction in load carrying capacity and safety, change 

of route(s) thereby increasing the length of transit or 

complete stoppage of traffic in the absence of alternate 

route(s). This, in turn, adversely affects the movement 

of men and goods which may result in an increase in 

transportation cost of road users, and thereby affecting 

the commerce and economy of the region, or even of the 

whole country. Hence, it is necessary to maintain trafficworthiness 

of bridges with requisite levels of safety 

and serviceability. Like any other structure, bridges 

are to be planned, constructed, maintained, operated 

and replaced at the end of their service lives. Usually, 

concrete bridges are designed for 50-60 years. 12 

Often, the funds available for maintaining bridges 

are scanty. Hence, the most important task of bridge 

engineers is to minimise the cost of maintenance. This 

can be accomplished by the application of rational 

and scientific methods in all the activities pertaining 

to management of bridges throughout their lifespan. 

A scientific Bridge Management System (BMS) thus 

helps in making right decisions regarding maintenance 

and using the available resources in the best possible 

manner. 

Status of management of road bridges 

in India 

Indian Roads Congress (IRC) is responsible for the 

development of guidelines for various aspects of roads 

and bridges in India. It has developed a manual to 

provide guidelines for Highway Bridge Maintenance 

Inspection (IRC:SP-18). 13 In addition IRC:SP-35 is being 

used as a manual of guidelines on the inspection and 

maintenance of culverts, minor bridges, and major 

bridges including submersible bridges, but excluding 

cable-stayed and suspension bridges. 14 The latter 

document summarizes the status of bridge management 

in the following manner: 

• 

• 

• 

Present practices of bridge management vary 

from state to state. 

Inspection and maintenance are mostly carried out 

by State Public Works Departments (PWDs). 

Databases are usually inadequate. 

• 

• 

• 

• 

Maintenance policy is reactive and not 

responsive. 

Very little funds are allocated for bridge 

maintenance and repair. 

No organization exists exclusively for inspection 

and maintenance of bridges. 

There are no avenues of formal institutional 

training. 

IRC:SP-35 also summarises the requirements for research 

and development in the maintenance of bridges as the 

need to: 14 

• 

• 

• 

• 

Investigate the effectiveness of present methods 

of maintenance. 

Develop criteria for evaluating the performance/ 

efficacy of different maintenance strategies. 

Develop improved materials and techniques for 

bridge maintenance. 

Study of the economics of maintenance of bridges 

of various ages and types. 

Jain has highlighted the issues in the development 

and implementation of scientific BMS in India. Some 

important ones are: 4 

• 

• 

• 

The study of the desirability and practicality 

of application of BMS to highway and railway 

bridges in India. 

The development of procedures for compilation 

of data on bridges, particularly old and deficient 

ones. 

The development of procedures for bridge 

inspection and rating. 

The following characteristics of the current maintenance 

practices of the National Highways in India are mentioned 

in the Guidelines for Maintenance Management of 

Primary, Secondary and Urban Roads. 15 

• 

• 

• 

• 

The maintenance work is based on subjective 

judgment and engineering experience. 

Analytical tools are generally not used in decision 

making. 

Life cycle cost analysis is not a criterion for the 

selection of the best strategies of maintenance. 

The causes of deterioration of bridges and of the 

effectiveness of different maintenance strategies 

are often unevaluated due to non-availability of 

requisite data. 


15

On the basis of the study of bridge inventory and 

inspection reports of 5237 bridges spread across various 

National Highways in 20 States of India managed by 

different State Public Works Departments, the following 

observations were made: 2 

16 

• 

• 

• 

• 

• 

• 

The inventory of bridges was not updated. 

The year of construction of about 30 per cent of 

the bridges studied was not known. 

In the majority of cases, the condition of bridge 

components was mentioned as good without any 

quantitative criteria for such assessment. 

The types of distresses of various bridge 

components were mentioned, but their extent 

and severity were not. 

The history of inspections and maintenance works 

was either missing or not properly recorded. 

The lack of data was found to be the main hurdle 

in developing a scientific BMS. 

The fund allocation for bridge maintenance was about 

2% of the total allocation for the total highway budget. 16 

Table 2. Objectives, activities and modules of BMS 

Objectives of BMS Activities associated 

with BMS 

To maintain a bridge or a network of 

bridges in a satisfactory condition 

To guarantee the safety of the users 

with specified risk 

To ensure a targeted level of service 

To allocate and use limited resources 

in a judicious manner 

To determine present needs for 

maintenance, rehabilitation, and 

replacement of bridges 

To predict future needs among the 

various alternatives 

To prioritize bridges for 

maintenance, rehabilitation and 

replacement 

To predict the remaining service life 

and minimize life cycle costs 

To ensure collection of objective 

information on all bridges 

To ensure techno-economical 

feedback 

To provide information to the road 

users 

Maintaining an 

appropriate data base 

Inspecting bridges 

Defining bridge 

conditions 

Predicting bridge 

requirement 

Prioritizing bridges for 

maintenance, repair, 

rehabilitation and 

replacement 

Allocation of funds 

Identifying bridges for 

posting (monitoring and 

rating of bridges) 

Cost-effective alternative 

for each bridge 

Scheduling maintenance 

Accounting for actual 

bridge expenditure, and 

Tracking minor 

maintenance activities 


In the case of India, only 40 % of the amount required 

for maintenance of highways is generally available. As 

the funds allocated are meagre, it is imperative that they 

are spent judiciously. 

objectives, activities and modules of 

bridge management system 

A scientific Bridge Management System (BMS) helps 

in making right decisions regarding maintenance and 

optimal utilization of the available resources. The 

Organization for Economic Cooperation and Development 

(OECD) report on bridge management defines BMS as a 

tool for assisting highway and bridge agencies in making 

the right choice of optimum improvements to the bridge 

network that is consistent with their policies, long-term 

objectives, and budgetary constraints. 7 Scherer and 

Glagola have defined BMS as a rational and systematic 

approach to organizing and carrying out all the activities 

relating to managing a network of bridges. 17 The 

literature on bridges mentions a number of functions 

of BMS. The various BMS objectives and associated 

activities with various BMS modules are summarised in 

Table 2. 7, 14, 17 to 24 The BMS is purported to optimize the 

selection of maintenance and improvement activities 

BMS Modules 

Bridge inventory – It contains all administrative and technical 

information pertaining to a bridge or a network of bridges e.g., location, 

type, age, etc. 

Inspection and reports – Collection and maintenance of reports of all 

inspections and maintenance work carried out since opening to traffic. 

Many of the BMS modules are developed by using this information. 

Condition state – Present physical state indicating soundness of a bridge 

determined on the basis of an inspector’s judgment and/or testing 

Deterioration rate – How the structure has deteriorated since opening to 

traffic due to increasing age and erosive effect of traffic and environment? 

Prediction of life – Minimum expected life at the time of design/ 

maximum period up to which bridge can be subjected to traffic flow to 

serve as intended function 

Requirement of inspection, maintenance, repair, rehabilitation and 

replacement – when, what and how much? 

Cost of inspection, maintenance, repair, rehabilitation and replacement 

of a bridge or a network of bridges 

Estimation of LCC of bridge/bridge stock considering both direct and 

indirect costs 

Rating - Method by which ability of a bridge to safely bear the present 

volume of traffic is ascertained 

Prioritization of maintenance, repair, rehabilitation and replacement – By 

ranking of bridges based on rating and/or LCC 

Optimal utilization of funds for maintenance, repair, rehabilitation and 

replacement, reprioritization depending on the availability of funds

in order to maximize the benefits and minimize the 

costs. BMS assists decision making, but does not replace 

human judgment. Though the requirements and general 

principles of bridge management remain same, the art 

and practice vary from country to country and even from 

state to state within a country owing to factors, such 

as goals and objectives of the concerned organization, 

bridge stock and its characteristics, environmental 

factors, the type of personnel employed, availability 

of funds, construction and maintenance practices, 

availability of materials, minimum serviceability 

requirement and so on. 

Bridge inspection practices 

For effective repair and rehabilitation of bridges, proper 

understanding of their existing conditions is required 

and this starts with inspection. 25 Environmental factors 

perennially impact the condition of bridges and are 

beyond human control. A newly built bridge requires 

due attention right from the day it is opened to traffic. 

Due consideration may also be required in the upkeep 

of the constructed parts of bridges if the construction 

period spans more than a year as otherwise by the time 

construction is completed some components might have 

been deteriorated. Eventually, the condition at the time 

of opening a bridge to traffic may not be the same as 

anticipated and will impact the overall performance of 

the bridge. 

Table 3. Types of inspection in different countries 

No. Country Type of inspection 

1 Austria 7 

2 Denmark 7 

3 France 7 

4 Germany 7 

5 Norway 7 

6 Slovenia 7 

7 United Kingdom 7 

8 United States 26 

9 Vietnam 27 

10 Taiwan 28 

11 Ireland 29 

12 Sweden 30 

13 India (a) Road bridges 13,14 

14 India (b) Railway bridges 3 

Initial / 

Preliminary / 

Acceptance 

Superficial / 

Routine / Regular / 

Assessment 

Visual inspection is the cheapest and easiest way of 

assessing the condition of bridges although a better 

appraisal can be done only with detailed testing 

and/or sophisticated health monitoring means, tools 

and equipments. Regular inspection ensures sound 

performance of a bridge, timely identification of 

distresses and remedial measures, creation, updating 

and maintenance of data base, and right feedback to the 

3, 13 

designer, owner, and road user. 

Depending on the objective of inspections, the type 

of inspection and its frequency vary. The inspection 

may be daily patrol, preliminary inspection, and end 

of guarantee inspection, routine inspection, general 

inspection, major inspection, special inspection and 

exceptional inspection. 

Routine inspection is performed after extreme seasonal 

variations and consists of visual inspection of all parts 

of a bridge. Detailed inspection, on the other hand, is 

performed after every 5-10 years and consists of visual 

inspection with or without testing of all parts of a bridge. 

Special inspection is carried out first before opening 

to the traffic and in case of extraordinary events and 

justification of funds. It consists of detailed inspection 

with non destructive testing of all parts of a bridge. The 

types of inspection prevalent in different countries are 

summarized in Table 3. 

General / 

Detailed 

Major / 

Principal 

Special Exceptional 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


17

Bridge health index 

The use of indices is one of the easiest means of 

determining the priority of bridge maintenance. Bridge 

indices may be broadly classified into: (1) Bridge health 

index, and (2) Maintenance priority index / Priority 

ranking functions. 

The general form of a bridge health index (BHI) may be 

given by equation (1). 

18 


......(1) 

where, BHI = bridge health index, K i = weight of the 

i th component, C i = condition of the i th component, n = 

number of bridge components 

Maintenance priority index has the general form as per 

equation (2). 18 

......(2) 

Where, MPI = Maintenance priority index, K i = Weight of 

the i th deficiency, F i = i th deficiency, a, b, c, …. = Attributes 

of the deficiency 

The application of maintenance priority index is 

quite common in some countries. However, not 

many systematic studies have been carried out on the 

development of bridge health index. The development 

of these indices invariably involves evaluation of various 

bridge components in order to arrive at their relative 

importance. 32 Also, from equations (1) and (2) it is 

evident that the determination of K i ’s is paramount in 

the development of both the indices. 

The description and characteristics of some specific 

bridge indices used in different countries are given. 

united States of america 

Roberts and Shepard have developed a health index (HI) 

for the state of California in the USA. 33 The expressions 

used to calculate the HI are given in equations (3) to 

(5): 

......(3) 

where, 

and 

......(4) 

......(5) 

FC = Failure cost of element; WF i = Condition state 

weighting factor 

In equation 3, HI is defined as the ratio of current element 

value (CEV) to the total element value (TEV) of all the 

elements of a bridge. The value of HI varies from 0 to 

100. The CEV is the sum of the weighted product of 

quantities of elements in various conditions and the 

failure cost of elements. TEV is the product of the total 

element quantity and the failure cost of elements. In this 

equation, relative importance of bridge components is 

computed on the basis of their quantity and failure cost 

of elements. Cost may not be the criteria while assessing 

the condition of bridge components. The bridge 

attributes, such as strength, safety and serviceability 

are the basis of determining the relative importance of 

bridge components. 

In the USA, many states are implementing PONTISBMS 

in which the above mentioned Bridge Health Index 

(BHI) is used as a diagnostic tool to assess bridge health 

condition. POINTIS was developed in the early 1990s 

for the FHWA and became an AASHTO product in 

1994. POINTIS is a Windows-based BMS that performs 

functions such as recording bridge inventory and 

inspection data, simulating conditions and suggesting 

actions, developing preservation policy etc. However, 

while implementing this BHI to the bridges in City and 

County of Denver (CCD), Jiang and Rens observed that 

it does not take into cognizance all the defects in a bridge 

and is subjective to imprecise cost data. 34 Engineers 

at the CCD were of the opinion that the current BHI 

neglects the effect of element damage on bridge health, 

function, and safety. The study carried out by Jiang and 

Rens pointed out the following issues in the use of the 

above BHI: 34 

• 

The accuracy of BHI value was not conservative. 

Most bridges rated in the highest BHI level 

(between 90 and 100 percent) even after they 

had served for many years and suffered element 

damage to various degrees.

• 

• 

• 

The BHI variation was not sensitive to individual 

element distresses. Even when a bridge had 

suffered from heavy element damage between 

two inspections, the BHI was found to be 

decreasing by an extremely minimal amount. 

The uniformity of bridge distribution based on 

BHIs was suspect. 

PONTIS BHI gave the percentage of residual 

element value and had no relationship to bridge 

health condition. 

In order to remove these drawbacks, a new index called 

Denver Bridge Health Index (DBHI) was developed by 

Jiang and Rens with the following three modifications 

resulted in a more conservative BHI estimate: 34 

• 

• 

The element quantity and cost were removed 

from the formula and 

a non-linear health index coefficient was 

introduced. ; and 

In addition, the weight coefficient adjustment method 

was incorporated. In DBHI, weights of the bridge 

components are still dependent on the condition state of 

the components. To make the index more conservative, 

weight coefficients are adjusted in consultation with 

the practicing engineers of CCD. However, adjustment 

factors may not be same for all the components. For 

example, adjustment factor for girders may not be same 

as that for railing. 

McClure and Hoffman have described the deficiency 

rating system used in the state of Pennsylvania, USA. 23 

The system consists of activity ranking, activity urgency, 

bridge criticality, and bridge adequacy. Depending on 

the condition of a bridge, points are assigned on the 

basis of the aforesaid four parameters and they add up 

to 100. In a network, each bridge has its deficiency score, 

which can be used to decide the urgency of maintenance. 

Priority of rehabilitation and replacement is decided on 

the basis of the degree of deficiency. Deficiencies are 

evaluated in following three categories: 

a) Level of service deficiencies: Four characteristics 

are included in level of service, viz., load capacity 

(LCD), clear deck width (WD), vertical clearance 

above the bridge (VCOD), and vertical clearance 

below the bridge (VCUD). 

b) Bridge condition deficiencies (BCD): Deficiency 

points for the primary elements, viz., superstructure 

(SPD), substructure (SBD) and bridge deck (BDD) 

are given on the basis of condition ratings. These 

three are then added up to give the bridge 

condition deficiency. 

c) Other deficiencies: They are related to remaining 

life (RLD), approaches (AAD) and waterway 

adequacy (WAD). These, in turn, are directly 

related to the condition ratings in the database 

and calculated by prescribed equations. 

Total Deficiency Rating (TDR): It is the sum total of all 

deficiency points multiplied by functional classification 

factor and is given by equation (6) below: 

(LCD + WD + VOCD + VCUD + BCD + 

RLD + AAD + WAD) ......(6) 

Functional classification factor (φ) is used as per the 

importance of the road, for example, value of φ for 

interstate: 1.0, arterial: 0.95, collector: 0.85 and local: 

0.75 

TDR, combined with the cost information and other 

factors, will help in listing of the bridges that are in 

need of rehabilitation and replacement, in the order of 

priority. 

The sufficiency rating formula given by Federal 

Highway Administration , USA, is a method of 

evaluating Highway Bridge by calculating four separate 

factors to obtain a numeric value which is indicative 

of bridge sufficiency, i.e., serviceability. 9 This method 

yields a percentage of sufficiency in a scale wherein 100 

percent represents an entirely sufficient bridge and zero 

percent, an entirely insufficient or deficient bridge. The 

sufficiency rating is given by equation (7) below: 


......(7) 

Where, S1 stands for structural adequacy and safety; 

S2 for serviceability and functional obsolescence; S3 for 

essentiality for public use and S4 for special reductions 

(used only when (S1 + S2 + S3) > 50). However, 

sufficiency rating involves several equations and is 

rather a tedious system. 

Taiwan 

Tserng and Chung have reported the condition index 

used in Taiwan. 35 In Taiwan, 20 main bridge components 

19

and corresponding weights are considered to calculate 

the condition index. Condition of the main component 

is the average condition of sub-components. The 

expressions used therein are given by equations (8) to 

(10): 

where, 

and 

20 


......(8) 

......(9) 

......(10) 

where, IC i is the condition of component ‘i’, W i is the 

weights of importance of component ‘i’, IC ij is the index 

of the ‘j’ part of component ‘i’ and ‘n’ is the number of 

parts. The factor ‘a’ is dependent on the importance of 

road. For example, a=1 stands for the highway bridge, 

and a=2 for the freeway bridge. 

The above model is based on a deduct point system 

ranging from a perfect score of 100 to zero. 

The condition of a sub-component is determined by 

rating it on a scale of 0-4 on the basis of degree (D), 

extent (E) and relevancy (R) of the defects. In case any 

element has more than one defect, the most severe 

defect is chosen for the rating. However, it would 

have been prudent to consider the effects of all types 

of distress affecting the condition of a bridge element. 

Moreover, D, E, and R are taken as same for all types 

of distress. This may not be true for all the defects and 

every possible defect would have a different degree, 

extent and severity corresponding to condition states 

of bridge components. 

It is also observed by Tserng and Chung that there 

is no relation between the index obtained by the 

above mentioned equations and the age of the bridge, 

Sothey proposed a new performance index called Net 

Performance Index (NPI). 35 The index is based on a 

point deduction system that is subtracted from a perfect 

score of 100. 

Vietnam 

Priority Maintenance Index (PMI) in Vietnam is the 

combination of Bridge Health Index (BH) and Bridge 

Importance (BI). 27 The index BH represents physical 

and serviceable conditions of a bridge and comprises 

three components: safe degree of bridge structures 

(SF), bridge serviceability (SV) and bridge impact on 

third parties (TP). BI index represents the important 

characteristics of an individual bridge in terms of its 

location, serviceability, and traffic demand in the road 

network. The factors used in the computation of BH are 

based on the suggestions of key personnel of the bridge 

owners and their agencies, academic researchers and 

field specialists in Vietnam. PMI is given by equation 

(11): 

......(11) 

∝ 1 and ∝ 2 are relative importance and health factors, 

respectively and (∝ 1 + ∝ 2 =1). 

BI has a maximum value of 100 in accordance with the 

equation (12) below: 

......(12) 

I L , I W and I T are practical indexes of location, width and 

traffic volume respectively. 

The index BH represents physical and serviceable 

conditions of the bridge and has a maximum value 

of 100. The expression for BH is given in equation 

(13). The maximum value of the safe degree of bridge 

structures (SF) is 50 while those of bridge serviceability 

(SV) and bridge impact on third parties (TP) are 40 and 

10 respectively. 

europe 

......(13) 

The expression and the details for the computation of 

condition rating in Austria, Slovenia, and the United 

Kingdom are discussed briefly in the following 

sections. 7 

The condition rating is calculated by the equation (14) 

in Austria.

where, 

......(14) 

G i - Type of damage: There are 32 types of damages. G i 

varies from 1 to 5 representing the severity of damage. 

K 1i - It is the extent of damage expressed by numerical 

values between 0 and 1 and described by words: few or 

some, frequent and very frequent or large and usually 

refers to components of the bridge or to the whole 

bridge structure. The extent K 1i is not quantified by the 

measured sizes (length, area, etc.) of the damage. 

K 2i - It is the intensity of damage expressed by numerical 

values between 0 and 1 and also described by words: 

little or insignificant, medium, heavy and very heavy. 

K 3i – It is the importance of the structural component 

or member: K 3i varies between 0 and 1. The structural 

components are classified as primary, secondary and 

other parts. 

Depending on the value of condition rating ‘S’, severity 

of deterioration is prescribed. 

In equation (14), the type of damage, the extent and 

severity of damage and the relative importance of bridge 

components are taken into consideration. However, for 

each damage type, the extent, severity, and importance 

of component have been given values in the range of 0 

to 1. It would have been more appropriate to consider 

the actual values of distress, as is the case in the method 

used in Taiwan. The condition of a bridge is dependent 

on its components which may be affected by a number 

of distress types. The effect of various damages on 

components should be considered during assessment. 

Moreover, severity of damage may not be represented 

by numbers 1-5 implicitly. 

The condition rating R for assessing the condition of 

a bridge structure is expressed by equation (15) in 

Slovenia. 

......(15) 

Where, ∑V D is the effective sum of the damage values 

calculated for the observed structure or its part (e.g., 

bridge component), related to the detected damage types 

and given by equation (16) below. 


......(16) 

where, V D is damage type value, B i is basic value (1-4) 

associated with the effect of damage type on the safety 

and/or durability of the observed structural element. 

K 1i – Factor which describes the extent of damage and is 

expressed by numerical values ranging from 0 to 1. The 

extent is not described by the measured sizes (length, 

area, etc.) of the damage on the affected component or 

structure. 

K 2i – Factor which describes the intensity of damage and 

is expressed by values ranging from 0 to 1. In the field, 

only the intensity grades I to IV (I – light, II – medium, 

III – severe, IV – very severe) are recorded. 

K 3i – Factor which describes the importance of the 

structural component or member for the safety of the 

entire structure. The values range between 0 and 1. 

K 4i – Factor which describes the urgency of intervention. 

The values range between 0 and 1. 

∑V Dref is the sum of damage values obtained by taking 

into account every damage type from the same list 

of damages that could potentially occur on the same 

observed structure or its part, multiplied by unit 

values of factors of intensity and extent (K 2i = K 3i = K 4i 

= constant = 1). 

On the basis of the calculated condition rating the 

inspected structure is classified into one of the 

deterioration classes I (R=0-5), II (R=3-10), III (R=7-15), 

IV (R=12-25), V (R=22-35) and VI (R≥30). 

In the United Kingdom, Total Assessment Rating (TA) is 

calculated by the equation (17). 7 Thirty three structural 

items are considered in terms of estimated costs, extent, 

severity, work and priority. 

......(17) 

where, R a (1 - 5): Age of bridge rating depends on the 

year of bridge construction; R f (1, 3, 4 or 5): Bridge form 

rating depends on the type of construction; R d (1 - 5): 

Vulnerable detail rating depends on the number of 

vulnerable details (few-1, many-5); R v : Traffic volume 

assessment rating (R v is 1 up to 20,000 vehicles per day 

21

and 5 for over 80,000 vehicles per day), depends on the 

daily traffic flow, i.e., the number of vehicles per day; R u : 

Annual average daily flow below or adjacent to bridge 

(same as R v ), and R i : Route importance rating (0 – 5), i.e., 

strategic importance of the route. 

The value of TA varies between 8 and 50. The priority 

rating (PR) is determined on basis of the TA rating value 

into five classes viz. 1(TA=43-50), 2(TA=36-42), 3(TA=29- 

35), 4(TA=22-28), and 5(TA=8-21). 

Total assessment rating consists of six ratings relating 

to bridge age, bridge form, vulnerable detail, traffic 

volume, annual average daily flow and importance of 

route. The priority rating (PR) is determined on basis of 

the range of values for TA classified into five categories. 

It is primarily a priority ranking wherein age of the 

bridge, the type of construction, traffic volume and the 

importance of the route are taken into consideration for 

determining priority rather than the condition rating of 

a bridge. 

Chile 

Valenzuela et al presented an integrated bridge index 

(IBI) describing it as a function of the structure condition, 

the bridge importance and the natural risk factors that 

can affect bridge serviceability. 36 The main factors in 

the IBI are strategic importance (SI), bridge condition 

(BCI), hydraulic vulnerability (HV), and Seismic risk 

(SR) and. The IBI, whose value varies between 1 and 10, 

is computed using equation (18): 

IBI = -1.411+1.299BCI+0.754HV+0.458SR - 0.387SI 

......(18) 

In the above equation BCI relates to the condition of a 

bridge and is given by equation (19): 

22 


......(19) 

Where, ECI i is element condition index of the element ‘i’; 

w i is weight of the element ’i’ with respect to the whole 

structure; and m i is material factor of each element. 

ECI is computed on the basis of visual inspection and 

the description for condition states and its value ranges 

from 1 to 5. The weights are strongly dependent on the 

type of structure and should be defined case by case. 

From the above it may be concluded that different 

countries and researchers have used select components 

for development of bridge indices. Due to this, although 

the aim of all these indices remains the same which is 

to predict the present status of the bridge condition, the 

principles and approaches behind developing them are 

quite different. 

In all the health indices described above, condition states 

of bridge components are invariably used. Condition 

states are described by using qualitative terms. They 

are detailed in next section. In addition to the condition 

states, the models used in Taiwan, United Kingdom, 

and Slovania stress on the importance of the extent and 

severity of a distress on the condition of various bridge 

components. However, the models do not specify the 

various distress types and the extent and severity of 

each. 

BHI may exclusively consider bridge components 

and corresponding distress types. For each type of 

distress, its characteristics, extent, severity, urgency 

of maintenance, type of maintenance task should be 

considered for evaluating BHI. Priority indices include 

factors causing the distress of a bridge as well as those 

influencing the priority of maintenance. 

Bridge condition states 

It is expected that a bridge made of certain materials (e.g. 

concrete, steel etc.) of specific structural configuration 

would behave in the same manner in spite of variations 

in site condition and severity of environment. Site 

conditions and severity of environment would affect 

the performance of a bridge. They may be factored 

in while ascertaining the condition of a bridge. 

Infrastructure condition is often represented by discrete 

condition states. 37 Condition at a point is the function 

of past condition and other factors, such as age, traffic, 

weather, and maintenance. Condition rating reflects 

physical deterioration due to environmental effects 

and traffic while appraisal rating indicates changes in 

traffic volume, existing load capacities, and compliance 

with safety standards related to bridge geometry and 

clearances. 

There are two approaches to the evaluation of the 

condition of the whole structure. 7 The first one is based 

on a cumulative condition rating, wherein the most 

severe damage to each element is summed up for each 

span of the superstructure, each part of the substructure, 

the carriageway and accessories. The second method 

uses the highest condition rating of the bridge 

components as the condition rating for the structure as a

whole. The highest (most unfavourable) condition rating 

assigned to one of the components is not necessarily 

the condition rating of the whole structure. In the final 

assessment of the structure, damaged components, type 

and extent of damages, expected growth of the damage 

and its influence on the traffic flow and safety should 

be identified. The condition rating for the whole bridge 

cannot be higher than the one assigned to the most 

deteriorated component and cannot be lower than the 

one assigned to either of the main components, such as 

abutments, piers, bearings, slabs and girders. 7 

Clearly, different countries and researchers have adopted 

different scales of rating condition states for assessing 

the state of bridge health. In spite of the single objective 

of representing the overall condition of a bridge based 

on the visual inspection, there is no unanimity on the 

number of scales and their description. From the analysis 

of the scales of rating condition state, it is observed that 

following three main objectives are to be included in the 

definition of condition state: 

• 

• 

• 

Strength of various elements of a bridge- Strength 

refers to the ability of a bridge element to sustain 

all the forces that are likely to occur due to its own 

weight and environment, interdependencies and 

its usage. It can be achieved by using appropriate 

materials and providing requisite dimensions. 

The strength also indicates the soundness of a 

bridge. 

Safety to road users- Safety refers to the passage 

of users through a bridge without any harm or 

discomfort. Safety can be ensured by proper 

alignment, adopting appropriate geometric 

standards and providing auxiliary means of 

protection. 

Serviceability – Serviceability indicates the ability 

of a bridge to serve the intended function, or in 

other words, to satisfy the present requirement 

of users. Serviceability can be enhanced by 

providing adequate width, number of lanes and 

clearances over and/or under the bridge. 

Condition states also include the type of distresses 

causing bridge failure and the urgency of maintenance. 

Some countries and researchers tried to accommodate 

one or two types of distresses while defining the scales of 

rating condition states. Condition states are the relative 

qualitative measures of the condition of a bridge on the 

basis of visual inspection. Condition states are described 

by terms, such as excellent, fair, critical etc. They are 

designated by numeric/roman numbers ranging from 

3 to 10, either in the ascending or descending order of 

degree of the fitness of a bridge. Majority of countries 

use five-point scale of rating for condition states. While 

higher number of condition states are difficult to judge, 

lesser numbers are inadequate to completely describe 

all the conditions. 

Condition ratings are important to automate decisions 

on maintenance, repair and replacement of bridges. The 

relation of condition states to decisions and planning 

activities has been increasingly recognized, prompting 

new definitions of condition states as a part of the 

development of bridge management systems. 38 Each 

factor, damage, function, and vulnerability, can be 

expressed as condition, and can be reported as condition 

ratings. 38 

Table 4 shows the details of condition scales followed 

by different countries. The condition states adopted in 

all the countries except the USA are in the ascending 

order, i.e., a bigger number is ascribed to a more severe 

condition. 7, 19, 27, 39, 40 It may be noted that many condition 

states prescribe the severity of damage while describing 

condition states. 7, 19, 27, 35, 39, 40, 42 The type of distress, 

extent of distress, maintenance actions, urgency of 

maintenance, etc., are also considered by some countries 

7, 35 

while defining the scales of rating condition states. 

Condition state also includes the types of distress 

causing bridge failure in combination with other factors 

including the urgency of maintenance. Although some 

countries and researchers have tried to accommodate 

one or two types of distresses while defining the 

condition state scales, these are still insufficient as they 

do not capture all the factors discussed above. Moreover, 

these condition states are unable to quantify the extent 

and severity of all possible distress types. 

Another limitation of condition states is that they are 

subjective and likely to vary according to the judgment 

and experience of a bridge inspector. Ambiguity and 

subjectivity is unavoidable in the results of visual 

inspection. Subjectivity can be reduced with the help of 

non-destructive evaluation but such evaluation reports 

are required to be interpreted cautiously. There is hardly 

any method which is capable of predicting the composite 

behaviour of all components of a bridge. A judicious 

combination of visual inspection and non-destructive 

testing is required to reduce the subjectivity. 

It is not possible to accurately evaluate serviceability 

and safety on the basis of visual inspection. 43 Visual 


23

inspections and the resulting condition states are not 

accurate measures of the safety and serviceability 

of a bridge, as they do not take into consideration 

the initial safety of the bridge component, the effect 

of the deterioration on the safety, and the relevance 

of component safety to the safety of the overall 

structure. 3 

Reliability and Life Cycle Cost (LCC) methods depend 

on quantitative rather than qualitative information. 

Development of method that does not rely solely on 

subjective data is essential. Many uncertainties and 

ambiguities exist in the interpretation of inspection 

data for reinforced concrete bridges. 5 It is necessary 

to redefine the comprehensive condition states so as 

to minimize the draw backsin health assessment of 

bridges. 

Condition-ratings are subjective and do not always 

reflect the actual serviceability or vulnerability of a 

bridge. 44 The quality of results obtained necessarily 

depends on the skill, experience and theoretical 

Table 4. Type of condition states 

No. BMS/Country 

24 

Number of 

condition state 


knowledge of the inspector. It is possible to get consistent 

results from visual inspection if the bridge inspectors are 

well qualified and trained. Subjectivity can be reduced 

to a certain extent if visual inspection is aided by nondestructive 

evaluation. Variability of observations 

can be reduced by supplying standard forms of all 

distress types for the sake of uniformity in evaluation. 

Subjectivity and variability can also be reduced to a 

greater extent by considering the combination of distress 

types and condition states. In view of the above, it is 

necessary to develop the condition states combined with 

distress types and range of values predicting the extent 

and severity of each distress type. 

Concluding remarks 

A comparative study for bridge definitions, types of 

inspection, condition states and bridge indices has been 

presented. Results of visual inspection are prescribed 

by the condition states which are further used for 

development of bridge indices. Condition states as 

expressed now are unable to predict the combined effect 

of defects and hence need to be modified. 

Scale Damage/condition based on 

Urgency of 

maintenance 

included? 

Maintenance 

actions included? 

1 Austria 7 1-6 severity No No 

2 Denmark 6 0-5 severity Yes No 

3 France 4 0-3 severity Yes No 

4 Germany 5 1-4 severity Yes Yes 

5 Norway 5 1-4 severity Yes No 

6 Slovenia 5 1-5 distress type, severity, extent No No 

7 Slovenia (Modified) 6 I-VI distress type, severity, extent Yes Yes 

8 United Kingdom 4 1-4 severity Yes No 

9 United States 10 9-0 distress type, severity, extent Yes No 

10 PONTIS 4 1-4 distress type, severity, extent No No 

11 

The United States Army Corps of 

Engineers (USACE) 

6 0-5 distress type, severity, extent No No 

12 Quebec, Canada 6 6-1 severity No No 

13 Vietnam 4 0-III severity No No 

14 Taiwan 5 0-4 distress type, severity, extent Yes Yes 

15 KUBA-MS, Switzerland 5 1-5 severity 

16 EIRSPAN, Ireland 6 0-5 severity Yes No 

17 J-BMS, Japan 5 0-4 severity Yes Yes 

18 DISK, Netherlands 7 0-6 severity Yes No 

19 

Swedish National Road 

Administration 

4 0-3 severity Yes No

The model used in Taiwan stresses on the importance 

of the extent and severity of distress on the condition 

of various bridge components. However, the model 

does not specify the various distresses in terms of type, 

extent and severity. 

Bridge index is used for presenting the condition 

of a bridge and deciding the ranking of bridges for 

maintenance planning. There is not a single bridge 

index which takes into consideration different types of 

distresses causing ineffective performance of a bridge. 

It is thus appropriate to take into consideration the 

different components, their relative weights and the 

types of distresses affecting the bridge components for 

the development of BHI. From the review of literature 

presented in previous sections, the following conclusions 

can be derived: 

Present inspection data in India are not updated 

and hence not useful for the development of 

BMS modules especially deterioration and LCC 

modules. It is, therefore, necessary to develop 

an appropriate format for visual inspection of 

bridges. 

Funds provided for bridge maintenance in 

India are scarce and therefore should be used 

scientifically and rationally. 

A description of condition states is yet to be 

prescribed by the Indian Roads Congress. It is 

necessary to develop comprehensive definitions 

of various condition states. 

It is also necessary to correlate the condition states 

with different types of distresses/defects and 

work out their corresponding numerical values, 

i.e., quantify the distress types. There is a need 

to develop a BHI which takes into consideration 

bridge components and distress types. 

In India, bridges are ageing and there is a need 

for a ranking method for deciding the priority of 

maintenance tasks. 

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management of highway bridges, Journal of Computing in Civil Engineering, 

2001, Vol. 15, No. 1, pp. 27-34. 

Hudson, R.W., Carmichael III, R.F., Hudson, S.W., Diaz, M.A., and Moser, 

L.O., Microcomputer bridge management system, Journal of Transportation 

Engineering, 1993, Vol. 119, No. 1, pp. 59-76. 

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Publishers Ltd. London, 1990. pp. 75-87. 

24. 

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and Maintenance Systems (BMMS) in Europe and the Far East, Bridge 


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1, No. 2, pp. 100-19. 


Dr. Sanjay S. Wakchaure received his civil 

engineering degree from Government College 

of Engineering, Shivajinagar, Pune, Masters in 

structural engineering from the Indian Institute 

of Technology Bombay, Mumbai, and PhD 

from the Indian Institute of Technology Delhi. 

He is an Executive Engineer in the Ministry of 

Road Transport and Highways, Government of India and is 

responsible for planning and monitoring of World Bank/Asian 

Development Bank funded Highway and Bridge Projects 

being carried out in different states of the country. 

Dr. Kumar N. Jha is with the Department of 

Civil Engineering, Indian Institute of Technology 

Delhi. He started his career with Larsen and 

Toubro Ltd. He has been involved with a number 

of construction projects and specialises in project 

management and formwork. He has published in 

a number of international and national journals 

and conference proceedings. His book on construction 

project management has recently been published by Pearson 

Education. He teaches various courses in construction 

technology and management. He has conducted a number 

of training programs for industry and has also been involved 

with a number of consultancy projects. 

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Discussion Forum 

Dear Sir, 

Discussion Forum 

Effect of improper casting sequence 

on compressive strength 

Please refer to the paper titled ‘Effect of improper casting 

sequence on compressive strength’ published in The Indian 

Concrete Journal, January 2012, Vol. 86, No. 1, pp. 30-41. I wish 

to congratulate the authors for choosing this topic. I find that 

the cube test results are exceeding the 28 days compressive 

strengths, prescribed in the IS 456:2000. I used to be very strict 

for not having any cold joints in the case of vertical cement mill 

bed concrete. This was many years ago. Now, after reading this 

paper, I am more reassured about the idea of cold joints. 

Under Table 1, in Sr. No. 6, the authors have given the ‘fineness 

of cement’ as 4%. But as per BIS specification IS 12269:1987, 

the fineness of cement should be not less than 225 m 2 /kg. 

I request you to get the correct information from the authors. 

I also request you to get the information of the weight of 

the cement used per cubic meter of concrete for the various 

concrete mixes used in the experiment. 

Thanking you, 

S. Lakshmanan 

Ovium Apartment, 

Block 3, Flat I, Door No 3-3- F1, 

2nd Street, Ponnuvelnagar, 

Narasothypatti, Salem 636004. 

The author replies 

Dear Sir, 

I would like to clarify that the cement fineness 

test was the sieve analysis fineness, conducted 

using a 90 microns sieve. According to 

IS 122269:2007, the fineness should not exceed 

10% by weight. The Blaine’s Air permeability 

test that gives fineness in m 2 /kg was not 

carried out by us. 

For other queries I would like to have the 

reader's direct contact details. 

with best regards, 

Ms. Amitha. N.R 

Assistant Professor 

Acharya Institute of Technology 

Acharya Dr. Sarvepalli Radhakrishnan Road, 

Soldevanahalli, Hesarghatta Main Road, 

Bangalore 560 090 


27

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Non destructive evaluation of concrete 

interlocking paving blocks 

Concrete interlocking blocks (CIBs) are used in 

commercial, municipal, and industrial constructions. 

Good engineering properties, low maintenance cost, 

ease of placement, removal, and reuse, aesthetic appeal, 

and easy availability make them a preferred paving 

material. However, often their quality leaves much to 

be desired. This paper presents the results of a non 

destructive testing exercise undertaken using both 

ultrasonic pulse velocity and rebound hammer tests to 

assess the compressive strength of commercially available 

paver blocks. 

Keywords: Interlocking paver blocks, NDT, rebound hammer, 

ultrasonic pulse velocity, compression test. 

With their increasing use in commercial, municipal 

and industrial projects, paving blocks are getting 

popular in the construction market. As a result, many 

manufacturers have mushroomed in the country. 

Although following IS 15658:2006 and paying attention 

to the quality are their prime concerns, sometimes the 

products being sold in the market show inconsistent 

strength development. 

Uncontrolled use of quarry waste and unconventional 

materials in the manufacturing process could cause 

the blocks’ compressive strengths to vary with some 

M.C. Nataraja and Lelin Das 

cases becoming unacceptable for construction. This 

paper reports the results from non destructive tests 

such as ultrasonic pulse velocity and rebound hammer 

and a destructive test namely compressive strength 

test performed on concrete blocks. Based on the 

results, graphs correlating the compressive strength 

with ultrasonic pulse velocity and rebound number 

were made for predicting the compressive strength 

of unknown samples. The correlation successfully 

predicted the compressive strengths quite close to the 

measured ones. 

literature review 

Although many factors affect the compressive strength 

of concrete paver blocks, some important ones are 

casting method, curing shape and size of the specimens. 

So, the calibration chart developed using standard cubes 

and cylinders [IS 13311 (Part-2):1992] and supplied with 

the rebound hammer are not suitable for determining 

their strength. As the blocks are relatively thin with a 

lower aspect ratio than the cubes, one needs to develop 

a separate calibration chart for paver blocks. In this 

regards, the influence of the shape and size of the 

specimens on the compressive strength of concrete is 

well documented. 1-3 It is also well known that the crack 

pattern in paver blocks is different from that in the 

standard cubes and cylinders. The extent of cracking 

in paver blocks is denser compared that in cubes and 


33

cylinders. In cylinders, a main inclined fracture surface 

is nucleated, whereas in cubes the lateral sides get 

spalled. In paver blocks, the failure is gradual with the 

central core getting fragmented due to crushing, in some 

cases exhibiting a dense columnar cracking in the bulk 

of the specimen. The compaction pressure also affects 

the strength of paver blocks. Wattanasiriwech et al. 4 

found that increasing the compaction pressure enhanced 

the densification and thus increased the compressive 

strength. The compaction pressure is therefore expected 

to significantly affect the rebound hammer number and 

the ultra sonic pulse velocity. As the blocks are thin 

and relatively strong, the conventional velocity ratings 

meant for structural concrete cannot be applied. A poorly 

compacted paver may give a higher rebound number, a 

relatively lower pulse velocity rating and strength than a 

150 mm cube of the same concrete. Hence it is advisable 

to develop separate correlation curves for assessing the 

quality of paver blocks. 

The use of recycled aggregates (RA) also affects the 

quality and strength of paver blocks .Although such 

aggregates have been successfully introduced in both 

structural and non structural concrete products , Poon 

and Chan studied the properties of concrete paving 

blocks prepared with contaminated recycled concrete 

aggregates (tiles, clay bricks, glass, wood) commonly 

found in the construction and demolition wastes and 

reported that density, compressive strength, tensile 

splitting strength, water absorption value, abrasion 

resistance, skid resistance and some durability 

parameters were greatly affected. 5-9 The use of RA as 

a replacement of conventional aggregates reduced the 

density and strength but increased the water absorption 

of the blocks. 10 Therefore, the waste generated from 

building activities is generally considered unsuitable 

for this application. Some other wastes that may be used 

include brick powder and fine-grained solid gasification 

residues. 11, 12 As ascertaining the quality of blocks made 

Table 1. Properties of blocks 

34 

Proportions Shape and size 

L x B, mm 

w/c= 0.4 1: 5.9 : 3.4 

190 x 160 

Thickness, 

mm 


Plan area, 

mm 2 

with such materials is difficult, their use is restricted to 

non structural applications. Under such a quality matrix, 

having a set of non destructive tests (NDT) to control the 

blocks’ quality both at the manufacturing plants and at 

site seems desirable. 13,14 

When CIPBs manufactures lack technical experience, 

they tend to produce the blocks by trial and error, 

resulting in an uneconomical process and blocks of 

low engineering properties. 15 Applying their expertise 

and experience, however, Aticin et al have developed a 

process prescription (optimum parameters of aggregate 

proportion, water/cement (w/c) ratio and dosage) for 

producing CIPB based on destruction specific energy 

(SE des ), strength, hardness and abrasion resistance of 

the blocks. 15 The destructive specific energy (SE des ) is 

estimated from the area under the stress-strain envelope 

in compressive strength test. The authors claim that the 

application of destruction specific energy for production 

of CIPB results in a lower cost and better engineering 

properties. 

A classical example of this application is the SONREB 

method developed by RILEM Technical committee 

and widely adopted in Romania. 22 It is gives a 

relationship between UPV, rebound hammer number 

and compressive strength of concrete in the form of a 

nomogram. The accuracy of the estimated strength is in 

the range of 15 to 20 percent. 

In addition, several other linear and non linear multiple 

correlation equations are available in the literature. 23,24 

Arioglu et al. obtained best strength prediction by using 

the non linearity of rebound number R and UPV, V in 

the form of power products. 24 Such regression models 

based on power products were used to correlate the 

compressive strength of concrete to its UVP (V) and 

rebound hammer number (N). In order to optimise the 

correlation, the mass density (MD) and class strength 

Porosity, at 28 

days, % 

Average Strength, at 28 days, MPa 

Compression Splitting Flexure 

70 28240 7.98 48.92 2.94 4.83

(CS) were also used in the model. Equation 1 is a typical 

regression model using these variables. 

c d e f 

y = a + b x1 . x2 . x3 . x4 

......(1) 

where y is the concrete strength (true or potential) 

and x 1 , x 2 , x 3 , x 4 , the quantitative variables UPV, RHN, 

MD and CS, when present, and a, b, c, d, e, f the model 

parameters. 

As many unconventional materials are used in 

the production of blocks which affect their quality 

significantly, research is continuing to assess engineering 

properties without destructively testing the blocks. This 

paper represents one such attempt 

Present study 

Two hundred paver blocks were procured from a single 

source and subjected to conventional curing and testing 

following the provisions of IS 13311 (Part 1 and 2):1992 

for rebound hammer number and the ultrasonic pulse 

velocity and IS 15658:2006 for compressive strength. 17-19 

A total of 72 blocks were tested, 36 blocks pertaining to 

7 and 28 day specimens each. Graphs were generated 

correlating the results of these measurements. The 

charts were later used for checking the quality of other 

blocks. Multiple correlations were also developed 

among compressive strength, rebound hammer number 

and ultrasonic pulse velocity for the same purpose. 

The mixture proportion of the concrete used in the paver 

block production was as follows: 

Cement: crushed granite rock fines: 10 mm and down 

granite chips is 1: 5.9:3.4 with w/c = 0.6. Some of the 

properties of the paver blocks such as shape, size, 

porosity and tensile strength are presented in Table 1. 

Schmidt rebound hammer test 

The most satisfactory way of establishing a correlation 

between the compressive strength of concrete and its 

rebound number is to measure both the properties 

simultaneously on concrete blocks. So the blocks were 

held in a compression testing machine under a fixed 

load of about 7 MPa and nine rebound numbers were 

taken on each of the two accessible faces. The average 

of 18 readings following IS 8900:1978 gave the rebound 

index for the block. 20 . Here the procedure given in IS 

13311(Part-2):1992 was followed. Subsequently, the 

blocks were tested for compressive strength following 

17, 21 

IS 15658:2006. 


35

ultrasonic pulse velocity test 

In this test, the direct transmission method was 

employed across the thickness of the blocks. This test 

was performed following IS 13311(Part-1):1992 at 

the centre of the specimen, as the core of the block is 

vulnerable to bending. From the path length and the 

transit time, the ultrasonic pulse velocity was calculated. 

The testing was done at the same spot twice and the 

average velocity was reported. The variation between 

two measurements was within about 5 percent. 

Compression test on paver blocks 

The most commonly used dumble shaped paver blocks 

(140 mm x 200 mm x 75 mm) were tested following 

IS 15658:2006. 

results and discussion 

Based on the destructive and non destructive results, 

calibration correlations were developed using the method 

of least squares. Figures 1 to 3 correlate compressive 

strength with rebound number, compressive strength 

with ultrasonic pulse velocity and rebound number with 

ultrasonic pulse velocity respectively. 

These figures give the calibration correlation as 

a straight line. In such expressions, the degree of 

correlation and its efficiency is evaluated in terms of ‘r’ 

the correlation coefficient. For practical applications, 

‘r’≥0.85 is acceptable. Figures 1 to 3 show a high degree 

of correlation between the parameters considered 

and hence these graphs can be used for practical 

applications. 

Table 2. Calculated and estimated compressive strength of paver blocks 

36 

Source Calculated 

actual 

compressive 

strength, MPa 

Calculated 

average 

rebound 

number, R 


Calculated 

average 

ultrasonic pulse 

velocity UPV, 

m/s 

Sample-1 35.5 30 3520 

Sample-2 42.8 42 3810 

Combined method 

In the present work, an effort also was made to develop 

multiple correlation of the type 

C = k + a N + b V ......(2) 

where k, a and b are constants of the equation. 

The constants k, a and b are 57.31, 0.692 and 20.584 

respectively. N is the calculated rebound number and V 

is the UPV value in km/s. Here the r 2 is 0.94 and standard 

error is 2.02. As the r 2 is higher than that obtained in the 

other cases, the combined method represents a better 

correlation. 

use of calibration charts 

In order to check the applicability of these charts, three 

sets of paver blocks were tested; two sets were from the 

same manufacturer (Sample 1) and the third set was from 

a different source (Sample 2). Eight blocks were tested at 

the age of 21 days by the non destructive and destructive 

methods and the corresponding compressive strength 

was determined as explained above. Table 2 presents 

the results. The strength variation based on the rebound 

number was within ±7 percent. 

The compressive strength variation based on the UPV 

was about +17 percent for the blocks from the same 

manufacturer. However, the variation increased to 33% 

when the samples were from the second manufacturer. 

Clearly, the calibration charts give incorrect strengths 

if the blocks are not manufactured under the same 

conditions. 

Estimated 

compressive 

strength from Fig.1 

based on N, MPa 

Estimated 

compressive 

strength from Fig. 2 

based on UPV, MPa 

Estimated 

compressive 

strength from 

equation 1, 

combined method 

MPa 

33.3, 41.49, 35.90 

-6.2% +16.9% +1.1% 

45.7, 56.9, 50.18 

+6.8% +32.9% +14.70%

Table 3. Calculated and estimated compressive strength of paver blocks using charts and equations 

Source Calculated 

actual 

compressive 

strength, MPa 

use of combined method 

Calculated 

average 

rebound 

number, R 

Calculated 

average 

ultrasonic pulse 

velocity UPV, 

m/s 

Sample-3 41.04 38 3455 

Sample-4 44.46 45 3605 

The compressive strength estimated using the combined 

method based on equation 2 was close to the actual value 

for sample 1 but +14.7 percent for sample 2. However, 

the variation in the combined method was less than that 

in the individual method. 

The analysis was extended to include two more samples. 

These additional blocks were again procured from two 

different sources and were designated Sample 3 and 

Sample 4. Ten blocks from each source were tested 

following the same sequence as described before. Table 3 

summarises an estimate of the compressive strength 

made using the charts. The UPV is the average of all 

10 values based on direct transmission method. The 

Rebound numbers are average for each block and the 

average of 10 such averages was taken for strength 

evaluation. The ’V’ values shown in the brackets are 

from the equations shown in the graphs. The combined 

method was also applied using equation 2. Table 3 gives 

the calculated compressive strength for the observed 

values of R and V. The strength estimated by the 

rebound method was higher by 2.3 percent and 10.2 

percent for samples 3 and 4 respectively. However, UPV 

gave a lower estimate for samples 3 (by 7.4 percent) 

and a marginally higher estimate for sample 4 (by 1.2 

percent). However, these variations were within the 

limits permitted by the codes. 

The combined method based on the equation 2 gave a 

lower strength for samples 3 (2.3 percent lower) and a 

higher strength (about 8.1 percent) for sample 4 than the 

actual strength. However, these variations were within 

the limits permitted by the codes and were significantly 

less than the individual methods. 

Conclusions 

The compressive strength prediction by knowing two 

NDT parameters namely the UPV and rebound number 

appears to be practicable. The strength assessment is 

rather quick and gives initial information about the 

Estimated 

compressive 

strength from 

Figure 1 based on 

N, MPa 

quality of the blocks. Since the factors such as the type 

of cement and mineral admixtures, aggregates, surface 

condition, moisture condition, age of concrete influence 

the test results, they are to be kept in mind while 

interpreting the results. If these factors change separate 

calibration charts are to be developed. The combined 

method of predicting the compressive strength the based 

on both rebound number and UPV gave better results 

than the individual methods. 

references 

Estimated 

compressive 

strength from 

Figure 2 based on 

UPV, MPa 

Estimated 

compressive 

strength from 

equation 1, 

combined method 

MPa 

42 (41.6), 38 (38.02), 40.10 

+2.3% -7.4% -2.3% 

49 (48.9) 45 (46.02), 48.04, 

+10.2% +1.2% +8.1% 

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Edition), Bureau of Indian Standards, New Delhi, India. 

IS 15658:2006. Pre cast concrete blocks for paving-Specifications, Bureau of 

Indian Standards, New Delhi, India. 

IS 13311(Part-1):1992. Non destructive testing of concrete - Methods of test, 

Ultrasonic pulse velocity, Bureau of Indian Standards, New Delhi, India. 

IS 13311(Part- 2):1992. Non destructive testing of concrete - Methods of test, 

Rebound hammer, Bureau of Indian Standards, New Delhi, India. 

IS 8900:1978. Criteria for rejection of outlying observations, Bureau of Indian 

Standards, New Delhi, India. 

Proceq-Concrete test hammer, Operating instructions, Type N, PROCEQ 

SA Zurich, Switzerland, 1977. 

RILEM, 1994, RILEM technical recommendations for testing and use of 

concrete construction materials, E & FN Spon. 

Qasrawi, HY. ‘Concrete strength by combined nondestructive methods 

simply and reliably predicted’, Cement and Concrete Research, Volume 

30, 2000, pp. 739-746. 


24. Arioglu, E., Arioglu, N., Girgin, C. A. Discussion of the paper “Concrete 

strength by combined nondestructive methods simply and reliably 

predicted” by H.Y. Qasrawi’, Cement and Concrete Research, Volume 31, 

2001, pp. 1239-1240. 

Dr. M.C. Nataraja holds a PhD from Indian 

Institute of Technology, Kharagpur. Presently, 

he is a Professor in the department of civil 

engineering at Sri Jayachamarajendra College of 

Engineering, Mysore. He has research experience 

of 25 years and has published over 100 technical 

papers in national and international journals and 

conferences. His areas of interest are SFRC, concrete mix 

design and controlled low strength materials. He is in the 

international technical committee of PROTECT in connection 

with international conferences. 

Mr. Lelin Das received his BE in Civil Engineering, 

M.Tech in Structural Engineering and is pursuing 

his PhD at Sri Jayachamarajendra College of 

Engineering, Mysore. Presently, he is a Technical 

Officer at Ultratech Cement Ltd. at Mysore. 

His research interests include use of marginal 

materials in concrete, special concretes and 

concrete mix design. 

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The annual story of tall building construction is 

becoming a familiar one: 2007, 2008, 2009, 2010, and 

now 2011 have each sequentially broke the record for 

the most 200 meter or higher buildings completed in a 

given year. Once again, more 200 m+ buildings were 

completed in 2011 than in any year previous, with a total 

of 88 projects opening their doors. Shenzhen’s Kingkey 

100, at 442 meters, tops the 2011 list. 

Continuing shifts 

The buildings completed in 2011 have effected a 

significant change in the world’s tallest 100 buildings, 

with 17 new buildings added to the list. Perhaps most 

significantly, for the first time in history the number of 

office buildings in the tallest 100 has diminished to the 

50% mark, as mixed-use buildings continue to increase, 

jumping from 23 to 31. As recently as the year 2000, 85% 

of the world’s tallest were office buildings – meaning 

that a 35% change has occurred in just over a decade. In 

terms of location, Asia, now with 46 of the 100, continues 

to edge toward containing half of the world’s tallest 

buildings. The Middle East region saw an increase of 

three, while Europe diminished to only one building in 

the tallest 100: Capital City Moscow Tower. 

dominant and emerging markets 

The eighty-eight 200 m+ projects completed in 2011 

(the tallest 20 of which are profiled in Figure 1) provide 

a helpful insight into where this expected increase in 

international building development will take place. On 

the one hand, statistics show that several of the major 

markets in recent years continue to thrive – and drive 

a significant percentage of the tall building market. 

China and the UAE contain a total of 39 of the projects 

– over 44% of the world’s completions in 2011. However, 


A year in review : Trends of 2011 

Skyscraper completion reaches new high for fifth year running 

Nathaniel Hollister and Antony Wood 

several cities, not previously seen as centers of tall 

building construction, are quite evident in this group 

of projects. In fact, the three cities to complete the most 

200 m+ buildings in 2011 are all relative newcomers to 

the list: Panama City (10 completions), Abu Dhabi (9 

completions), and Busan (9 completions). Before 2011, 

these cities had a combined total of six 200 m+ buildings. 

Together, they now contain 34 such buildings and 

accounted for 32% of completions in 2011, surpassing 

traditional tall building centers such as Dubai, Shanghai, 

and Singapore. 

China 

When discussing skyscraper completion, it is impossible 

to neglect the market of China, which contributed 23 

completions in 2011. 

However, quite surprisingly given the region’s 

impressive market, we have seen China’s global 

percentage of building completions begin to drop off 

slightly. In 2009, China contained 45% of the buildings 

completed and 33% in 2010. In 2011, China contained 

only 26% of the global total of 200 m+ completions. 

This decreasing figure demonstrates that, despite the 

continued increase in building construction in China and 

relatively tame historical markets, other new markets 

are immerging. 

Shenzhen’s Kingkey 100, at 442 meters (1,449 feet), was 

the tallest to complete in 2011, opening in December. 

The 100-story building is topped by a 38-meter (125-foot) 

sky garden which serves as the lobby of the building’s 

hotel and contains three levels of restaurants/ bars. Also 

completed in 2011 was the Longxi International Hotel, 

located near the Chinese village of Huaxi. The village, 

rumored to be the richest in China, sees the building as a 


39

40 



Figure 1. The tallest 20 buildings completed in 2011, 10 of which, for the first time in history, are supertalls. © CTBUH 

mark of their economic development over the past halfcentury, 

with its height symbolically matching (within 

two meters) the height of the tallest building in Beijing, 

the capital of China. 

dubai 

Another significant existing market is the city of Dubai, 

which added six 200 m+ buildings in 2011. It is helpful to 

recall that, just a decade ago, the entire UAE contained a 

total of only three 200 m+ buildings. It now contains 60 

such buildings, behind only China and the USA. Within 

ten years, the country has established itself as a centre 

of tall building construction, and has completed more 

200 m+ buildings than any other country except China 

in the past two years. 

In 2011, Dubai’s 23 Marina became the world’s 

tallest residential building, at 393 meters (1,289 feet). 

Coincidentally, the building sits near both The Torch (the 

previous world’s tallest residential for a short time) and 

the under construction Princess Tower (set to become 

the world’s tallest in 2012), making the Dubai Marina the 

tallest residential skyscraper cluster in the world. 

Panama 

Before 2008, no 200 m+ buildings existed in all of 

Panama. Then, between 2008 and 2010, three buildings 

opened. In 2011, Panama City completed ten 200 m+ 

skyscrapers, more than any other city and more than 

double the number of completions in all of North 

America. With these completions, there are now 12 such 

buildings in Panama, perhaps signalling a new day for 

the tall building in this region. 

One of these buildings, the Trump Ocean Club 

International Hotel & Tower, became the tallest 

building in Central America when it completed in 

2011 at 284 meters (932 feet) in height. Additionally, 

there are another eight buildings currently under 

construction and set for completion by the end of 2012, 

an impressive figure for a country of only 3.5 million 

inhabitants. While these numbers are easily dwarfed by 

the immense number of completions in China or other 

major tall building markets, they point to an immerging 

tall building market. Panama is not the only emerging 

market in this region: Mexico also completed its third 

200 m+ building in 2011 and currently has three other 

significant tall building projects under construction.

Figure 1. continued 

abu dhabi 

Another emerging market in 2011 was Abu Dhabi, 

Dubai’s neighbour. This city added nine 200 m+ 

buildings in 2011, remarkable as it contained only 

two such buildings at the beginning of the year. 

Another thirteen 200 m+ buildings are currently under 

construction in Abu Dhabi, showing that the city will 

continue to be an important market for the next several 

years. 

Abu Dhabi’s largest project to complete in 2011 was 

Etihad Towers, a complex comprised of five towers 

ranging between 218 meters to 305 meters. The complex 

provides a significant amount of residential, office, and 

hotel space to the city. The tallest of the towers, Etihad 

Towers 2, became the city’s tallest building and first 

supertall. 

Busan 

The Korean tall building market has also seen significant 

development in recent years, containing twenty-four 200 

m+ buildings by the end of 2010. However, only one 

such building existed in the country’s second largest 


city, Busan. 2011 saw all this change with 9 of the 11 

Korean completions taking place in Busan. This included 

the completion of the Doosan Haeundae We’ve the 

Zenith Tower complex and Studio Daniel Libeskind’s 

Haeundae I’Park complex. These two projects, which 

sit directly next to each other, added five 250-meter 

(820-foot) residential buildings to Busan. 

2011 also saw the completion of Korea’s tallest building, 

the Northeast Asia Trade Tower. The building is located 

in Incheon which, since it became Korea’s first free 

economic zone in 2003, has seen significant tall building 

development. 

united States and europe 

What role do developed regions, like the United States 

and Europe, play in the future of the tall building? Are 

these markets expanding or expended? 

Historically speaking, the United States experienced its 

skyscraper “heyday” in the 1980s, when forty-nine 200 

m+ buildings were completed. To put this in perspective, 

during the same decade China and South Korea each 

completed only two such buildings, while Europe and 


41

the UAE completed none. This building boom continued 

into the early 90s, until it ended in 1994, after which the 

US did not complete any 200 meter buildings for a full 

five years. 

In 2011, two 200 m+ buildings were completed in the 

US: New York’s Eight Spruce Street and Cincinnati’s 

Great American Tower. Eight Spruce Street, recipient of 

the CTBUH 2011 Best Tall Building Americas Award, 

uses its façade to create a draping fabric-like quality, a 

unique addition to the city’s skyline. 

Europe, another significantly developed tall building 

market, completed four 200 m+ buildings in 2011, 

matching its record set in 2008. These buildings, spread 

through the UK, France, Germany, and Russia, seem 

to point to a possible resurgence of the tall building 

in continental Europe. There are currently 20 such 

buildings under construction in Europe, with some ten 

set to complete in the next two years. 

France’s Tour First building, completed in 2011, took a 

40-story building completed in the 1970s and completely 

refurbished it. The project retains the integrity of the 

original tower while providing a modern interpretation 

of the concept and vastly improving the environmental 

performance, internal conditions, and circulation. With 

the addition of ten floors, the project became France’s 

tallest building at 231 meters (758 feet). This reuse and 

reinvigoration of an existing building can be seen as 

a model for what is likely to become a common event 

around the world. As buildings age and become in 

42 



danger of becoming obsolete, significant renovations 

can be more effective than complete demolition. 

Conclusion 

Having examined the history and status of a variety of 

tall building markets, several assumptions can be made 

about the next decade of tall building construction. 

Existing skyscraper markets, particularly China and the 

Middle East, are predicted to continue to play a major 

role in the tall building industry. China currently has 

over 180 projects under construction that are over 200 

meters in height, and thus will undoubtedly play the 

primary role in tall building development for the rest 

of this decade. However, the tall building typology 

continues to diversify, and we can expect to see the 

further development of a number of new markets over 

the next few years. Cities like Panama City, Abu Dhabi, 

Busan, and many others in Central and South America, 

Asia, and the Middle East will continue to play an 

increasing role in tall building development. 

With over 300 projects above the 200-metre mark 

currently under construction internationally, the tall 

building community is set to continue to develop at an 

incredible pace. As new markets continue to discover 

and develop the tall building, it is quite possible that 

this pace will continue through the end of this decade. 

Without a doubt, the skylines of the world will see 

tremendous change by the year 2020. 

For the detailed report, readers are requested to get in 

touch with the authors at info@ctbuh.org 

Nathaniel Hollister, BArch, received his 

professional Bachelor’s degree in architecture 

from the Illinois Institute of Technology. He is 

the Production Coordinator at the Council on 

Tall Buildings and Urban Habitat (CTBUH), USA 

and is primarily responsible for contributing to 

the research, design, and production of various 

CTBUH publications and press releases, including the 2010 

CTBUH Reference Guide — a book documenting current tall 

building statistics. In addition, he facilitates the research and 

organization necessary for the production of the “CTBUH in 

Numbers” articles and other technical reports. 

Dr. Antony Wood, PhD RIBA, is Executive 

Director of the CTBUH, responsible for the dayto-day 

running of the Council and steering in 

conjunction with the Board of Trustees. Based 

at the Illinois Institute of Technology, Antony 

is also an Associate Professor in the College of 

Architecture at IIT, where he convenes various 

tall building design studios. A UK architect by training, 

his field of specialism is the design, and in particular the 

sustainable design, of tall buildings.

Superposition principle invalid in 

iS 13920 design of slender rc walls 

with boundary elements 

D.H.H. Rohit, P. Narahari, Arvind Kumar Jaiswal and C.V.R. Murty 

Current code IS 13920:2002 for ductile detailing of 

concrete structures assumes that moment capacity of a 

RC structural wall with boundary elements is the sum of 

moment capacity of the web portion of the wall and that 

due to the couple using axial capacity of the boundary 

elements and lever arm between them. This assumption 

leads to gross over-estimation of design moment capacity 

of the wall. In this paper, provisions are reviewed and 

improvements suggested eliminating this deficiency in 

the code provisions. A nonlinear method is suggested 

based on principles of mechanics for estimating the 

combined P u-M u strength envelope, considering the 

combined contribution of the web and boundary elements 

of the wall. Using this, a numerical study was performed 

of moment capacity of RC structural walls (both with 

and without boundary elements) to demonstrate that 

superposition principle is not acceptable in the design 

of RC structural walls with boundary elements. 

Key words: RC frame buildings; RC structural walls; design 

code; moment capacity; superposition. 

rC Walls with boundary elements 

RC structural walls in RC frame buildings can be 

designed without or with boundary elements (Figure 1). 

Often, a uniform column grid is maintained and walls 


43

44 

Notations 

A si = Area of steel reinforcement bar i 

A st = Area of uniformly distributed vertical 

reinforcement 

be = Boundary element 

BE = Boundary element 

CA = Centroidal axis 

d = Cover to steel reinforcement bar 

E s = Elastic modulus of steel 

f ck = Characteristic compressive strength of 

concrete 

f scx = Stress in concrete at depth x from extreme 

compression fibre 

f si = Stress in steel reinforcement bar i 

f y = Characteristic strength of steel 

h w = Vertical height of wall 

l w = Length of wall inclusive of boundary elements 

P u = Axial compression on whole wall crosssection 

P be = Axial compression on boundary element 

only 

P uz = Axial capacity of whole wall cross-section 

(with M u =0) 

M u = Moment on whole wall cross-section 

M uv = Moment on wall web only 

M uz = Moment capacity of whole wall cross-section 

(with P u =0) 

NA = Neutral axis 

t w = Thickness of wall 

x u = Depth of neutral axis from extreme compression 

fibre 

x i = Depth of steel reinforcement bar i from neutral 

axis 

ε c = Strain in concrete 

ε si = Strain in steel reinforcement bar i 

ρ t = Percentage of vertical steel reinforcement 

σ c = Stress in concrete 

σ si = Stress in steel reinforcement bar i 

built between two column lines (placed symmetrically 

in the two plan directions to avoid twisting in the 

building). 1 The boundary elements provide the needed 

confinement at the wall ends as well as offer a consistent 

architectural form at the exterior surface, in addition to 

providing for a uniform structural grid. 2 

Conventionally, Reinforced Concrete (RC) structural 

elements should be designed to behave in an underreinforced 

manner; steel should yield before concrete 

crushes, and this gives enough warning before the 


structural element fails. But, a critical review of the 

current design provisions in the IS 456 confirm that this 

desired mode of failure is not realised analytically. 3 IS 

456 specifies that the limiting state in compression of 

concrete is reached when compression strain in the 

extreme concrete fibre reaches 0.0035. But, many text 

books and handbooks on the subject take this strain of 

0.0035 in the calculation of moment capacity M u of the 

section to occur under all circumstances, irrespective of 

whether the RC section is in compression or in tension. 

The negative consequence of this is that academics, 

students and practitioners involved in design of RC 

structures do not internalise the importance of making 

RC structures under-reinforced. In the specific context 

of structural walls, being made under-reinforced means 

tension steel reaches the limiting strain in tension before 

the extreme fibre in compression reaches limiting strain 

in compression. M u calculated by the textbooks and 

handbooks is not far from the exact intent when the RC 

section is shallow, e.g., RC columns or beams. 4-7 But, 

the said misinterpretation leads to M u estimates that 

are significantly off from those obtained from the exact 

interpretation of the clause, when the RC sections are 

deep, e.g., RC walls. 1,2,3,8 In RC slender walls with low 

elevation aspect ratio (h w /t w ), the under-estimation of 

M u is even more amplified by the linear super-position 

suggested in IS 13920 in the calculation of M u . 9-11 This 

paper explains the above mentioned misinterpretation; 

lays down the exact method of estimating M u that 

is based on fundamentals of mechanics, namely 

equilibrium, compatibility and constitutive law; and 

argues in favour of discontinuing the use of principle 

of superposition for estimating M u of RC walls as laid 

down in IS 13920. 

estimating moment capacity M u of 

structural walls 

The moment capacity of RC structural walls subjected 

to compression and flexure is governed by Clauses

38.1 and 39.1 of IS 456 and based on the following 

considerations: 3 

• 

• 

• 

• 

• 

• 

Plane section normal to the axis of bending 

remains plane even after bending 

Bending compressive strength of concrete is 

0.67 times the characteristic cube compressive 

strength. Design stress-strain curves of concrete 

and steel are shown in Figure 2. 

Maximum compressive strain at the highly 

compressive extreme fibre in concrete is 0.002 in 

pure compression, 0.0035 in bending compression, 

and 0.0035 minus 0.75 times the strain at the least 

compressive extreme fibre under combined axial 

compression and bending (when there is no 

tension on the cross-section) 

Tensile strength of concrete is ignored 

Maximum strain in tension reinforcement at 

failure is not less than 0.002 + (f y /1.15E s ), where f y 

is characteristic strength of steel, and E s modulus 

of elasticity of steel; and 

Partial safety factors for material strengths are 1.5 

for concrete and 1.15 for steel. 

Using these considerations, Annex A of IS 13920 

provides the following closed-form expression to 

estimate ultimate moment capacity M u of RC structural 

walls without boundary elements: 11-13 

(a) When , 

where 

; and 

......(1) 

(b) When , 

where 

and . 


......(2) 

In Eq.(2), (x u /l w ) is obtained by solving the quadratic 

equation 

and . 

, where 

Eq.(2) has an error; the expression for α 2 should read 

as: 

......(3) 

The assumptions and limitations behind expressions 

for M u are: 7,12,13 

1. 

2. 

The stress–strain curve for steel is assumed to be 

the bilinear one (Figure 2(b)). 

Reinforcement bars are assumed to be distributed 

uniformly along the wall length. If any other 

distribution is adopted, the expression may not 

help in obtaining M u . 

45

46 

3. 

4. 

5. 

6. 

7. 

The extreme compressive fibre 

of concrete always develops a 

strain of 0.0035. Assuming the 

concrete fails first even when 

the structural wall section is 

under-reinforced, results in 

violation of basic mechanics. 

Annex A of IS 13920 does 

not provide expression for 

M u when neutral axis is 

located outside the section 

[Figure 3 (d)]. 

The minimum value of 

maximum tension strain in 

reinforcement bars is 0.0020 

+ (0.87f y /E s ). 

When boundary elements are provided, Clause 

9.4 of IS 13920 uses principal of superposition to 

determine the total M u contributed by structural 

wall and boundary element, even though the 

stress-strain curves are nonlinear for both steel 

and concrete. 

Under pure axial compression, the axial 

strain is 0.002 throughout the section. In the 

expression of P uz , the contribution of concrete, i.e., 

0.446 f ck l w t w with 0.446 f ck being the stress in 

concrete throughout the section, is consistent 

with the axial strain of 0.002, but that of steel is 

not. At a strain of 0.002, the stress in steel must 

be 0.79f y , but is taken as 0.75f y for Fe 415 steel 

(Table 1) in IS 456:2000 and SP 16; and it is about 

0.75f y for Fe 500. 

Suggested improvements in 

calculation of M u of structural walls 

Changes are required in both interpretation and 

assumptions made in the Indian Codes for calculating 

the ultimate moment of resistance M u of RC structural 

walls. The following improvements are suggested: 

• 

Principles of Mechanics should be employed to 

arrive at M u of RC structural walls, which are 

consistent with the basic tenets of Limit State 

Method of design for strength. This approach 

will provide a general method to arrive at M u for 

any location of neutral axis; this will eliminate 

the incorrect assumption that concrete will 

always fail first and that too at axial-cum-bending 


Table 1. Calculation of stress in steel during pure axial 

compression for different steels (from Table A of SP 16) 

• 

• 

Design Stress 

Strain 

Fe 415 Fe 500 

0.85 × 0.87f y = 0.7395f y 0.00163 0.00195 

0.90 × 0.87f y = 0.7830f y 0.00192 0.00226 

0.95 × 0.87f y = 0.8265f y 0.00241 0.00277 

compression strain of 0.0035. Also, exact stressstrain 

curves can be used of concrete and steel. 

When boundary elements are provided at ends 

of RC structural walls, the whole cross-section 

should be considered together in arriving at M u , 

thereby eliminating the need to apply principles 

of superposition on individual contributions 

of moments of resistance of wall web and wall 

boundary elements. 

Instead of specifying the minimum value 

of maximum strain (of 0.0020+0.87f y /E s ) in 

reinforcement bars with highest tension strain, 

a limiting strain (of 0.0020+0.87f y /E s ) should be 

specified. This will complete the definition of limit 

state design by specifying the limiting strain on 

the tension side. 

The advantage of such an approach is that a section can 

be designed to be under-reinforced, and thereby have 

adequate warning, before failure of the wall. 

Principles of mechanics for estimating M u 

Rectangular RC structural wall sections (Figure 4) have 

two equilibrium equations, one for axial force on the 

section (Eq. (4)) and another for bending moments about 

axis of bending (Eq. (5)):

and ......(4) 

where N is the number of steel reinforcement bars in the cross-section. 


......(5) 

Stress-strain constitutive relations of concrete (Eq.(6)) and Fe 415 steel (Eq.(7)) can be expressed respectively 

(Figure 2) as: 

......(6) 

......(7) 

The RC structural wall section consists of two materials, namely concrete and steel bars. As per Limit State Method of 

design, either or both of them can reach the limiting strain first; the limiting strains of concrete and steel bars are: 

......(8) 

47

and 

If concrete reaches the limiting strain first, 

and , then 

and if steel reaches the limiting strain first, 

and , then 

numerical study and discussion 

48 


......(9) 

......(10) 

......(11) 

As per Clause 9.1 of IS 13920, the thickness of wall shall 

not be less than 150 mm, and the reinforcement shall 

be provided along the plane of the wall. The thickness 

of the web of the wall is taken as 300 mm. The material 

properties of RC structural walls are taken as per IS 456 

[IS 456:2000] (Figure 2). 6 The percentage of minimum 

longitudinal reinforcement used is 0.25% of the gross 

cross-sectional area in accordance with IS 13920. This 

minimum longitudinal reinforcement is distributed 

across the cross-section as per literature. 14 This study 

uses the basis of minimum longitudinal reinforcement 

as proposed in the said publication (Figure 5). The 

discussion is based on P-M interaction curves of chosen 

wall sections. 

Walls without boundary elements 

Some changes are needed in the current code design 

philosophy as well as provisions. To establish the same, 

a comparative study between IS 13920 and the proposed 

Table 2. Error in Mu of a RC structural wall with crosssection 

aspect ratio 5.0 and reinforcement 0.25% as per 

IS 13920 and method given in literature 14 

ρ t 

Error in estimating M u (%) 

P u /P uz =0 P u /P uz =0.1 P u /P uz =0.2 P u /P uz =0.3 P u /P uz =0.4 

0.25 13.6 5.05 1.13 -1.64 -2.46 

0.3 12.46 4.67 0.95 -1.97 -2.75 

0.4 12.4 4.51 0.65 -2.57 -3.03 

0.5 11.11 4 0.6 -3.18 -3.29 

0.75 8.79 2.64 -1.08 -4.88 -7.69

method on estimating the strength of the structural 

element with aspect ratios 1.5 and 5.0 was carried out. 

To begin with, the error in the expression for M u (as 

given by Eqs.(1), (2) and (3)) is emphasised (Figure 6 

and 7). Figure 6 shows a kink due to the error, which is 

eliminated by using Eq.(3) and reflected in Figure 7; this 

kink occurs at the balanced section. 


49

Consider an RC column with cross-section aspect ratio 

of 1.5 and vertical reinforcement of 0.8%. Figure 8a 

shows that expression from IS 13920 (with correction) 

estimates a lower moment capacity of the section when 

compressive axial load P u is below the balanced level 

(and failure occurs by steel reaching the limiting strain in 

tension). Now, consider a RC structural wall with crosssection 

aspect ratio of 5.0 and vertical reinforcement of 

0.25%. Figure 8b shows that expression from IS 13920 

(with correction) estimates higher moment capacity of 

the section when compressive axial load P u is below the 

balanced level; Table 2 shows the error in estimating M u 

by IS 13920. The maximum error is 13.6%. 

Walls with boundary elements 

For RC structural walls with boundary elements, the 

axial compressive load demand on the boundary 

element as per IS 13920 is: 

50 


......(12) 

where M u and M uv are the moment demand on the RC 

wall and moment capacity of the web alone of the RC 

wall, respectively. Eq.(12) is based on the assumption 

that the boundary elements of the RC wall (a) resist 

only pure axial load without any bending moment on 

it, and (b) contribute to overall wall moment capacity 

through moment couple between the axial loads on 

the boundary elements at wall ends separated by the 

distance C w (Figure 9). 

In IS 13920, the moment capacity of a wall with boundary 

elements is required to be calculated as a sum of the 

moment capacity of the web alone and moment couple 

due to axial capacity of boundary elements as shown 

in Figure 9; this procedure hereinafter is referred as the 

Principle of Superposition. But, it is to be noted that 

in order to fully comply with the assumptions behind 

this principle, the strain variation has to be linear and 

continuous across the cross-section whereas IS 13920 

considers separate strain conditions for wall/web and 

boundary elements. Hence, the Superposition Principle 

is invalid. 

The axial load capacity P uz under pure compression is 

given by: 

......(13)

where 

A c,BE is area of concrete in the boundary element, and 

A st,BE area of steel in the boundary element. Rewriting 

Eq.(12), 

......(14) 

This superposition approach for estimating the moment 

capacity of RC structural walls is not acceptable 

even when cross-sectional aspect ratio of wall is 20.0. 

Figure 10 shows P-M interaction diagrams of walls of 

different cross-sectional aspect ratios l w /t w of 3, 5, 10, 15 

and 20. Four curves are shown representing: 

1. 

2. 

3. 

4. 

IS 13920 : Web only 

Method given in literature Web only 14 

IS 13920 : Web and boundary elements 

Method given in literature: Web and boundary 

elements 14 

IS 13920 estimates higher moment of resistance of RC 

structural walls than method given in literature that 

is based on principles of mechanics; 14 for small crosssectional 

aspect ratios l w /t w , moment capacity of RC wall 

with web and boundary elements is amplified by use of 

the principle of superposition (Eq.(14)). The difference 

reduces with increase in cross-sectional aspect ratio l w /t w . 

The code expression for calculating M u for RC walls with 

boundary elements should be replaced with a rational 

approach similar to that suggested in this paper. Also, 

SP 16 1978 provides details for P-M interaction curves for 

rectangular column cross-sections with reinforcement 

distributed equally on two sides parallel to the axis 

of bending, and reinforcement distributed equally on 

four-sides. 4 Similar curves should be made available for 

use in design of RC structural walls with reinforcement 

distributed equally on two sides perpendicular to the 

axis of bending. 

Concluding remarks 

This analytical study on moment of resistance of RC 

structural walls discusses IS 13920:2008 provisions. 

Rational interpretation is suggested on the provisions 

available in IS 13920 for design of structural walls. 

Expressions are presented, which are consistent 

with fundamental principles of mechanics, namely 

equilibrium, compatibility and constitutive law. A 

numerical study is performed to study P-M interaction 

curves of structural walls of different cross-sectional 

aspect ratio. This study suggests that: 

Superposition principle should not be used to 

estimate moment capacity of RC structural walls 

with boundary elements as given in IS 13920; 

and strength of wall web and boundary elements 

should be estimated considering composite action 

of wall and web elements. 

IS 13920 provision as given in Annex A, should 

be corrected related to estimating moment 

capacity of RC structural walls without boundary 

elements; the error is in the expression for α 2 as 

given in Eq.(3). 

Consistent with the limiting states specified in 

Limit State Method of design for RC structural 

walls (when high yield strength deformed steel 

bars are used), in the derivation of the expression 

for ultimate moment capacity M u of the wall 

section, the limiting strain for steel should be 

taken as 0.002+0.87 f y /E s and not just 0.87 f y /E s 

as taken in Annex A of IS 13920. This should be 

reflected eventually in the expressions of two 

parameters β and , as 

and ......(15) 


......(16) 

IS 13920 provisions on expression for M u of structural 

walls needs to be revised accordingly. Eqs.(15) and (16) 

are purely based on strain variation across the section 

and position of neutral axis as shown in Figure 3. 

references 

1. 

2. 

3. 

1. 

2. 

3. 

Dasgupta,K., (2008), Improvement of Geometric Design of Reinforced Concrete 

Structural Wall to resist Earthquake Forces, Ph.D Thesis, IIT Kanpur, June 

2008. 

Dasgupta,K., (2002), Investigation of IS Code Provisions on Seismic design of 

Reinforced Concrete Structural Wall, M.Tech thesis, IIT Kanpur, August 2002 

IS:456, (2000), Indian Standard Code of Practice for Plain and Reinforced Concrete, 

Bureau of Indian Standards, New Delhi 

51

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

52 

SP:16, (1978), Design Aids for Reinforced Concrete to IS: 456-1978, Bureau of 

Indian Standards, New Delhi 

SP:24, (1983), Explanatory Handbook on Indian Standard Code of Practice for 

Plain and Reinforced 

Sinha,S.N., (2008), Reinforced Concrete Design, Tata Mc-Graw Hill, 2008 

Varghese,P.C., (2007), Advanced Reinforced Concrete Design, Prentice Hall (India), 

New Delhi 

Dasgupta,K., and Murty,C.V.R., (2005), “Seismic Design of RC Columns and 

Wall Sections, Part I: Consistent Limit State Design Philosophy,” The Indian 

Concrete Journal, March 2005, pp 33-42 

Dasgupta,K., Murty,C.V.R., and Agarwal,S.K., (2003), “Seismic Shear Design 

of RC Structural Walls – Part I: Review of Code Provisions,” Indian Concrete 

Journal, November 2003, pp 1423-1430 

Dasgupta,K., Murty,C.V.R., and Agarwal,S.K., (2003), “Seismic Shear Design 

of Reinforced Concrete Structural Walls - Part II: Numerical Investigation 

of IS:13920-1993 Provisions,” Indian Concrete Journal, November 2003, pp 

1459-1468 

IS:13920, (2008), Indian Standard Code of Practice for Ductile Detailing of 

Reinforced Concrete Structures subjected to Seismic Forces, Bureau of Indian 

Standards, New Delhi 

Medhakar,M.S., and Jain,S.K., (1993), “Seismic Behavior, Design and 

Detailing of RC Shear Walls, Part I: Behaviour and Strength,” The Indian 

Concrete Journal, July 1993, Vol.7, pp 311-318 

Medhakar,M.S., and Jain,S.K., (1993), “Seismic Behavior, Design and 

Detailing of RC Shear Walls, Part II: Design and Detailing,” The Indian 

Concrete Journal, September 1993, pp 451-457 

Rohit,D.H.H., Narahari,P., Sharma,R., Jaiswal,A., Murty,C.V.R., (2011), 

“When RC columns become RC Structural Walls,” The Indian Concrete Journal, 

May 2011, Vol. 85, No. 5, pp 35-45 

D.H.H. Rohit is Graduate Pway Engineer at 

WS Atkins (India) Private Limited. His research 

interests include design and analysis of concrete 

structures, and earthquake engineering. 

P. Narahari is a Field Engineer at NTPC- 

BHEL Power Projects Ltd., currently posted in 

Mannavaram, Andhra Pradesh. His research 

interests include seismic analysis and design of 

steel and RC structures. 

Arvind Kumar Jaiswal is Chief Consulting 

Engineer at EON Designers, Secunderabad. 

He is also a Visiting Faculty at Engineering 

Staff College, National Council for Cement & 

Building Materials, and National Academy of 

Construction. His areas of interests include 3D 

computer modelling of structures, behaviour 

of RC frames due to earthquake loads, structural design 

software validation, large span structures, continuing 

education, and capacity building in earthquake engineering 

education for professional engineers. 

C.V.R. Murty is a Professor in Department of Civil 

Engineering at the Indian Institute of Technology 

Madras, Chennai. His research interests include 

the non-linear behaviour of reinforced concrete 

and steel buildings and bridges, and of limit 

state design of reinforced concrete, relevant to 

earthquake-resistant structures. He is a member 

of the Earthquake Engineering Committee of the Bureau of 

Indian Standards. 


Letter to the Editor 

Design of confinement 

reinforcement for RC columns 

Dear Sir, 

This has reference to the Point of View by 

Dr. N. Subramanian titled " Design of confinement 

reinforcement for RC columns" published in 

the ICJ issue of August 2011, Vol. 85, No. 8. 

The topic of Dr. Subramanian is nice and 

informative. I feel that confinement of stirrups is 

required at the supporting junctions to withstand 

more shear forces. This statement is missing in 

IS codes. On the other hand, ACI 318 clearly states 

that confined stirrups is required at supporting 

points, for example, in columns junctions between 

footing and column and at the floor level to 

handle the horizontal forces transferring due to 

diaphragm effect. I suggest that we take up this 

in the next revision of IS codes. The same type 

confinement of stirrups required in the beams 

supporting points also. 

Thanking you and with regards, 

Shridhar 

Technical Manager 

TEEMAGE PRECAST IN 

39/2, N.G. Palayam Pirivu, Thekkalur, 

Avinashi, Tirupur 641 654, Tamilnadu

Point of View 

Are heritage structures in Tamilnadu seismically vulnerable? 

This article is written with the sole purpose of starting 

a healthy discussion and providing a different point 

of view on the earthquake vulnerability of Chennai’s 

historical buildings such as Fort St. George and Madras 

High Court, following the revision in IS 1893:2002 

changing Chennai’s earthquake proneness from Zone 

II to Zone III. 

The basis for this discussion is a report published in a 

Chennai daily using somewhat debatable observations 

made by a well-known Professor and structural 

engineering consultant. The expert is reported to have 

said that: 

From colonial structures such as Fort St. George to single 

pier flyovers and 20-storey high rise buildings springing 

up in the suburbs, there is a need to check their earthquake 

resistance and carry out seismic retrofitting 

While delivering a lecture at a well known University 

in Chennai, the expert is reported to have further stated 

that: 

Fort St. George, seat of power in the state, would not 

withstand earth quakes of Zone 2 intensity”. (When the 

codes for the earthquake were revised in 2002, Chennai was 

moved up to Zone 3 up from Zone 2 as it was found to be 

more vulnerable). “No effort has been made to strengthen 

it” said the expert. 

A. Veerappan 

Similar is the case of the Madras High Court buildings. 

In Ripon Buildings, modifications have been suggested as 

part of extensive rehabilitation, but as of today it was also 

vulnerable, said the retired professor. 

The thickness of the shear walls, the ground floor car 

park and the use of flat slabs in high-rises were also quite 

vulnerable to earthquakes, as they would not be able to 

resist the “lateral load”. 


53

The expert claims that his study on eight modern 

apartment buildings in the city has revealed that seven 

of them were not earthquake-resistant. He further states 

that the single-pier bridges in the city on Pantheon 

Road, Royapettah High Road and TTK Road would 

suffer from “functional vulnerability” in the event of 

an earthquake. To reinforce his point he showed slides 

featuring quake damaged bridges that were designed 

with single-piers. For some other bridges in Chennai his 

recommendation was for providing seismic arresters to 

prevent their collapse in the event of an earthquake. He 

listed inadequate planning, design and application, poor 

code compliance, non-engineered buildings, inadequate 

detailing of reinforcements, extensions, alterations and 

encroachment as the reasons for the vulnerability of 

the Chennai monuments and buildings of historical 

importance to earthquake forces. 

54 


Point of View 

In my opinion these observations must be examined in 

detail and the context understood. 

Perhaps these statements were made with the purpose of 

creating an awareness among civil engineering students 

and faculty about the importance of designing structures, 

both load bearing and RC framed structures, taking the 

seismic forces into account and following IS 1893 : 2002. 

Perhaps the expert was also right in pointing out that 

many of the multi-storeyed apartment buildings with 

stilt (soft storey) constructed recently were not designed 

to resist even an earthquake of moderate intensity. 

However, to me most of the observations appeared to 

be generalised statements made without any specific 

data on building distresses and corresponding past 

earthquakes.

In my opinion, even though many of buildings the 

expert referred to were designed 100 years ago, without 

taking earthquake forces into consideration, they might 

not get distressed in the event of an earthquake simply 

because their layout, wall thickness and other systems 

for transmitting loads were adequately constructed 

based on the knowledge available then. 

And it is not only true for Chennai buildings, throughout 

the world century old buildings and monuments were 

not designed constructed considering earthquake 

forces. 

However, renowned architects and builders of the yester 

years constructed buildings by designing them following 

the norms prevailing then. They especially included 

wider foundation base, thicker walls (say min 1’6” to 

5’0”) that distributed loads more or less uniformly; 

more particularly they ensured that the centre of 

gravity (CG) of the load system was below 1/3 height 

of the structure, thereby providing stability, safety and 

serviceability to the structure. They also made sure that 

the buildings were without any tilt or overtapping. Many 

such constructions have performed well until now. 

Chennai‘s previous classification of earthquake 

proneness was under zone II. In 2002, it was changed to 

zone III in IS 1893 (Part – I): 2002 based on the digitised 

data of Survey of India. 

Would such a re-rating of earthquake proneness cause 

any severe effect on the existing century old structures? 

Should a mere change in the classification be the basis for 

worrying about the stability of century old structures? 

Point of View 

The answer to these questions lies in examining the 

structures and analysing their construction data. To 

begin with, TN never experienced an earthquake 

exceeding 6 on the Richter scale. The quakes of 1966 

and 2001 measured 5.4 and 5.6 on the Richter scale 

respectively. 

The change in classification means that in future the 

buildings have to be planned, designed and constructed 

providing adequate safety against the likely Zone III 

seismic forces (3.5 to 4.20 in Ritcher Scale).. 

In order to effectively resist the seismic and lateral forces, 

one of the important criteria specified in the building 

construction in general and in the framed structures in 

particular is the provision of strong column and weak 

beams. In other words, the stiffness of columns, piers 

or pillars should always be greater than the stiffness of 

beams and supporting floor or roof slabs. 

An examination of the old buildings in Tamil Nadu 

suggests that this theory was indeed followed in 

Chennai’s Fort. St.George Secretarial buildings, Rajaji 

Hall, Cheppakkam PWD Buildings, Presidency College, 

High Court Buildings, Madurai’s Thirumalai Nayakkar 

Mahal, Thanjavur’s Serfoji Palace and in many 

multitiered Hindu Temples. 

In sizing piers and the thickness of the load bearing 

walls the engineers of yester years have taken care to 

effectively prevent distress in the structure due to lateral 

loads including from seismic forces by constructing 

stronger pillars, piers, walls compared to floor, roof 

beams and slabs. 


55

Similarly, the foundation base of these buildings are 

symmetrical either as a square or rectangular, without 

any eccentricity or cantilever projections. Building such 

foundations is one of the criteria specified for earthquake 

resistant structures. The Fort St. George Secretariat 

buildings and multistoreyed Building (MSB) satisfy this 

important criterion and thereby minimize the effect of 

earthquake forces. Many of them are supported on a 

serried of well foundations? 

To resist lateral forces, some other factors that play an 

important role in the foundation system are the width of 

the foundation and thickness of the load bearing walls. 

In many of Tamil Nadu’s historical and monumental 

buildings including the palaces and temples, the base 

width of the foundation is in the range of 5’0” to 10’0” 

or more and the ground floor wall thickness is in the 

range of 1’6” to 3’0”. Further the CG of the entire load 

system is ingeniously arranged to be at 1/3 rd of the 

height of the buildings. Further, Height/Breadth/Width 

or Length/Breadth value is also kept well within 2 to 

56 


Point of View 

impart safety and stability to the structure against lateral 

forces including earthquake. 

• 

The Fort St.George and New MSB Secretariat 

buildings also satisfy these criteria. They are 

therefore are not likely to get distressed due to 

earthquake forces of the intensity as experienced 

in the past. 

Yet another important aspect in these structures is the 

load bearing masonry construction with allowable 

compressive and tensile bearing stresses. 

• 

The factor of safety in many of these old 

constructions is 10 (not 3) in compression and 8 

in bending /tension as against ( 1.5 x 1.5 =2.25) 

2.25 specified in IS: 456 - 2000. Due to this higher 

factor of safety adopted in the load bearing 

masonry structures such as Fort St. George 

Secretariat and other historical buildings, the 

safety and stability of these structures against

seismic forces is adequate. 

These details explain why 

these buildings did not 

get affected during the 

earthquakes of 1966 and 

2001. 

The design concept for structural 

use of unreinforced masonry is 

given in TN Building Practice, 

NBC of India – 2005 , IS 1905 

– 1985 - Code of Practice and 

SP : 20 (S & T) – 1991 Hand 

book on Masonry Design and 

Construction – BIS. Although the 

present day structural engineers 

and design experts are highly knowledgeable about 

framed RC structures, their exposure to the nuances of 

load bearing masonry structures is not enough. It would 

not be a surprise if many of them are not even aware of 

what the guidelines provide in IS : 1905 – 1985 and SP 

: 20 (S&T) – 1991. 

Point of View 

More than theory, analysis and design of structures 

conforming to the latest codal provisions, the 

performance of the structure during its life time 

should be the basis for vulnerability comments. 

Needless to say that buildings such as St. George, 

Chennai High Court and other Secretariat buildings 


57

withstood and performed excellently 

during the earthquake in 1966 and 

2001. 

The expert’s comment about the 

vulnerability of single piered flyovers 

on Pantheon Road and TTK Road, 

casting doubts on the ability of 

these structures to withstand the 

earthquake forces corresponding to 

Zone II / III is also debatable. Those 

involved in the construction of these 

structures were expected to follow the 

applicable design codes in designing 

and constructing the flyovers’ 

structural elements including 

single piered columns (with double 

cantilevers). The design of these 

structures follows IRC Standards 

and includes seismic forces. Only 

after satisfying themselves about 

the competitiveness of the designs 

do the authorities approve them for 

execution. Therefore, these flyovers 

are also not likely to suffer from any 

distress during earthquakes of the 

intensity as experienced in the past. 

For the sake of this discussion it 

is presumed that the expert has 

analysed and checked the stability 

of these single piered columns as 

free standing cantilever. However, 

design practices suggest that these 

single piered columns, from their 

real edge conditions, are to be treated 

as propped cantilever (since sway is 

adequately resisted and restrained 

by the heavy beam elements, under 

which the intensity of moment due 

to lateral load is reduced to ¼ of that 

of the free standing cantilever). In 

view of this fact, the approving civic 

authorities are encouraged to check 

the design details of the structures 

and reply to the expert based on the 

data. 

Notwithstanding the above, it is 

necessary to check the safety and 

stability of the historical buildings 

and present day RC framed structures 

with respect to likely earthquake 

58 


Point of View

forces and take suitable measures as specified in the 

following codes. 

1. 

2. 

3. 

4. 

IS 1893:2002 Indian Standard criteria for 

Earthquake Resistant Design of Structures 

IS 4326:1993 COP – Earthquake Resistant Design 

and Construction of Buildings. 

IS 13828:1993 Indian Standard – Guidelines for 

improving Earthquake resistance of Low strength 

masonry buildings 

IS 13920:1993 Ductile Detailing of RC Structures 

subjected to Seismic forces. 

In this connection it is worthwhile to consider the 

opinion of Prof. S.K.Duggal, Prof of Civil Engineering, 

Motilal Nehru National Institute of Tech, Allahabad 

and author of the book titled “Earthquake Resistant 

Design of Structures” published Oxford University of 

Press (2007). 

Point of View 

“Severity of ground shaking at a given location during an 

earthquake may be minor (occurs frequently), moderate 

(occurs occasionally) or strong (occurs rarely). The 

probability of a strong earthquake occurring within the 

expected life of a structure is very low. Statistically, 

about 800 earthquakes of magnitude 5.0-5.9 occur in 

the world, while only about 18 of magnitude above 7.0 

are registered annually. If a building is designed to be 

earthquake – proof for a rare but strong earthquake, it will 

be robust but too expensive. The most logical approach to 

the seismic design problem is to accept the uncertainly of 

the seismic phenomenon. Consequently, the main elements 

of the structure are designed to have sufficient ductility, 

allowing the structure to sway back and forth during a 

major earthquake, so that is withstands the earthquake 

with some damage, but without collapse. An earthquakeresistant 

structure resists the effects of ground shaking; 

although it may get severely damaged, it does not collapse 

during a strong earthquake. This implies that the damage 

should be controlled to acceptable levels, preserving the 

lives of the occupants of the building at a reasonable cost. 

Engineers thus tend to make the structures earthquake 

resistant”. 


59

Finally, the following may be suggested for making the 

buildings and structures resist the seismic forces to a 

reasonable extent. 

60 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

Construct RC / Concrete Tie beams in both 

directions at Grade beam level (just below the 

EGL) 

Provide RC continuous lintel at lintel level 

Have RC Floor / Roof beams in both directions 

at Floor level / Roof level. 

Reinforce the four sides / circumference of large 

openings 

Separate the asymmetrically loaded / projected 

cantilever elements from the main structures 

Reinforcing load bearing masonry walls at corners 

and junctions as shown in the enclosed sketch. 

Have compulsory provision of Ductile detailing 

of Rebars in foundation footings, Columns, 

Beams, Slabs and beam – column junctions as 

specified and detailed in IS 13920 – 1993 (Sketches 

enclosed) 


Point of View 

What is your opinion? 

8. 

Adopt Grade of concrete and steel Rebars 

according to exposure conditions as specified 

in Table No. 3 & No. 5 of IS : 456 -2000 Code of 

practice for Plain & Reinforced concrete – BIS 

These measures are sufficient to protect buildings and 

structures against the seismic forces expected to occur 

in and around Chennai. So the learned Professor’s 

statements should be seen as a statement of caution 

and his stress on the importance of designing and 

constructing buildings and structures against the 

codified earthquake forces must be understood, 

appreciated and adopted in practice to have durable 

structures in the state of Tamil Nadu. 

A. Veerappan, ME(Struct) FIE, MICI, Dip LL and 

AL is former Chief Engineer, Tamil Nadu Public 

Works Department. Presently, he is a structural 

consultant and state secretary of TNPWD Senior 

Engineers Association. He has delivered more 

than 2500 technical lectures to practising 

engineers (government engineers in particular). 

He has edited and published 40 technical handbooks for 

day-to-day use of field engineers and engineering students. 

He has won several prizes for his engineering writings, 

which have highlighted the importance of adopting modern 

constructions techniques and cost effective construction 

materials including the use of construction chemicals. He has 

many years of experience in restoration and strengthening 

of distressed buildings and foundations. 

Do you wish to share your thoughts/views regarding the 

prevalent construction practices in the construction industry 

with our readers? 

If yes, The Indian Concrete Journal gives a chance to 

the engineering fraternity to express their views in its 

columns. 

These shall be reviewed by a panel of experts. Your views could 

be limited to about 2000 words supplemented with good 

photographs and neat line drawings. Send them across by e-mail 

to editor@icjonline.com.

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