Carbon fibre reinforced laminates Bonded steel ... - Siegwart, Michael

Carbon fibre reinforced laminates Bonded steel ... - Siegwart, Michael

Carbon fibre reinforced laminates Bonded steel ... - Siegwart, Michael


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<strong>Carbon</strong> <strong>fibre</strong> <strong>reinforced</strong> <strong>laminates</strong><br />

<strong>Bonded</strong> <strong>steel</strong> plates<br />

Previous<br />



- Jordanstown -<br />

School of the Built Environment<br />

Introduction<br />


A building has to withstand various loads, e.g. the normal vertical loads from its weight,<br />

different load combinations, etc.. In addition, tall buildings are under attack from lateral<br />

forces caused by wind and earthquakes or other catastrophic impacts. Buildings are stiffened<br />

by means of structural elements such as shear walls. These walls are placed in form of a core<br />

to provide additional stiffness against lateral forces.<br />

In order to transform the forces that act on shear walls with openings, they are connected by<br />

means of coupling beams (coupled shear wall system). When a building with a coupled shear<br />

wall system is under attack by seismic forces, the energy is dissipated along the core of<br />

coupled shear walls by means of plastic hinges, which occur either in the beam or in the joint<br />

to the shear wall. After the seismic event, the beams can be repaired in order to restore the<br />

structural integrity of the building (Figure 1).<br />

The report presents the effectiveness of structural repair methods such as resin injection, plate<br />

bonding and glass <strong>fibre</strong>s. To do so, five full-scale concrete specimens, half of a coupled shear<br />

wall system, were produced and overloaded. Three of them were repaired by of means resin<br />

injection and structurally strengthened using externally bonded <strong>steel</strong> shear strips, <strong>steel</strong> plates<br />

and glass <strong>fibre</strong> <strong>laminates</strong>. After a curing period they were reloaded. Their behaviour was<br />

recorded and is presented and analysed in this report.<br />

<strong>Michael</strong> <strong>Siegwart</strong> 1


- Jordanstown -<br />

School of the Built Environment<br />

Background Knowledge<br />



Shear walls in seismic regions show good behaviour when seismic forces attack a building<br />

since they take and dissipate horizontal shear forces. They prevent buildings from collapsing<br />

during strong earthquakes and also avoid or limit structural damage when the applied seismic<br />

disturbance is moderate. Structures such as shear walls ensure that in the event of earthquakes<br />

human lives are protected, damage is limited and structures important for civil protection<br />

remain operational [8] . Different types of shear walls can be determined according to their<br />

design. The types are cantilever shear walls, coupled shear walls and slit shear walls (Figure<br />

4).<br />

The ultimate strength of such coupled shear walls is reached when a collapse mechanism is<br />

formed within the system. The collapse mechanism occurs when two plastic hinges develop in<br />

each coupling beam and one plastic hinge in each cantilever wall (at their base) is generated<br />

due to the subjected lateral load (Figure 3Figure 4, Figure 5). The sequence of hinge<br />

formation in a structure depends on the relative strength and stiffness of its components.<br />


The deformation of the coupling beams is a combination of shear (Figure 8) and flexure<br />

(Figure 7). The actions of a beam where shear and flexural stress are subjected is complex<br />

(Figure 9). There are two different types of behaviour. Firstly, where flexural action governs<br />

over shear action the behaviour is similar to the behaviour of beams that are only subjected to<br />

flexural stress. The second type, where shear stress governs, is more complex. The flexural<br />

deformations that cause a double curvature of the beam and consequently tension along one<br />

side and stress on the other half, conflict with the shear deformation, which puts the beam into<br />

tension along both surfaces [31] . At the early state of loading the beam deforms in a flexural<br />

load manner with a double curvature and a line of contraflexure at the centre of the span.<br />

When the shear is strong enough to initiate a diagonal crack, the flexural behaviour changes.<br />

A shift of the points of contraflexure from the midspan towards the supports in the opposite<br />

direction occurs. Hence, the line of contraflexure rotates anticlockwise as the diagonal crack<br />

<strong>Michael</strong> <strong>Siegwart</strong> 2


- Jordanstown -<br />

School of the Built Environment<br />

Background Knowledge<br />

in the concrete progresses. The shift of the points of contraflexure will stop near the end<br />

supports. At the end supports the conflicting forces of shear and flexure causes the<br />

reinforcement to kink. The maximum load-carrying capacity of the concrete is reached when<br />

small parts of concrete in the compression corners of the beam crush.<br />


Although concrete is a material which provides high durability and resistance against<br />

aggressive environmental factors, concrete structures undergo some damage due to physical<br />

impact or environmental attack and therefore need to be repaired. Damage might occur<br />

because of the following reasons: cracks in concrete, high permeability or high porosity,<br />

insufficient cover, carbonation and chloride, abrasion, freeze thaw, thermal shock, fire<br />

damage, high velocity waters, overloading, chemical reactions and alkali-silica reaction.<br />

Two basic types of repair work can be classified. The structural repair and the non-structural<br />

repair (Figure 11). The aim of any concrete repair is to protect the reinforcement from further<br />

corrosion, to enhance or restore the appearance of the structure, and to restore or increase the<br />

load carrying capacity. The selected repair method must provide durable repair within an<br />

acceptable cost range.<br />

Deep cracks in massive concrete members and cracks, which pass through a member, can be<br />

repaired by crack injection using a selected polymer such as epoxy resin. It is very important<br />

that the work is carried out carefully since inadequately repaired cracks cannot be repaired for<br />

a second time. Once epoxy has filled the cracks, it will rest there and cannot be removed any<br />

more. The resin is suitable to restore the structure to its original strength and stiffness [1] .<br />

The strengthening of beams by means of epoxy-bonded <strong>steel</strong> or composite plates is widely<br />

used. A major shortcoming of the system is the corrosion of the plates since the surface is<br />

fully exposed to the environment. An alternative to <strong>steel</strong> plates is therefore the bonding of<br />

<strong>reinforced</strong> plastics, which do not corrode. Other basic advantages are their low weight, which<br />

makes installation very easy and their greater length since the need for lapping at joints is<br />

eliminated. The material can be pre-stressed [20] and is fire resistant. [11] . On the other hand the<br />

material is relatively costly compared to <strong>steel</strong>.<br />

<strong>Michael</strong> <strong>Siegwart</strong> 3


- Jordanstown -<br />

School of the Built Environment<br />

Research<br />



The test specimens were designed as a part of a coupled shear wall that is connected by beams<br />

and cut in the midspan of the beam. The samples exist as a part of a shear wall that has<br />

dimensions of 1000mm in width, 150mm in depth, and 1200mm in height. The wall parts of<br />

all five samples were <strong>reinforced</strong> with 16mm high yield <strong>steel</strong> bars in the longitudinal direction,<br />

and with binders in 6mm of diameter @ 120mm. The ends of the wall contained a column<br />

reinforcement in order to dissipate the expected forces and to limit the failure on the beam.<br />

The concrete was designed f cu = 50 N/mmÄ. [7] Two different dimensions of coupling beams<br />

were produced. Two samples, Sample 1-40 and Sample 2-40 had a beam height of 40 cm, a<br />

length of 80 cm and a width of 15 cm (Figure 13). Sample 1-30, Sample 2-30 and Sample 3-<br />

30 had a beam height of 30 cm whilst the other dimensions were the same (Figure 12 and<br />

Table 1).<br />


Adjustable stanchions were placed on the surface of the shear wall section of the specimen.<br />

They supported the specimens vertically. Horizontal support was provided by means of three<br />

different mechanisms. First, an adjustable stanchion was placed horizontally at the top of the<br />

shear wall section and screwed onto a vertical rack stanchion. Second, a clamping mechanism<br />

that pulled the shear wall on the same vertical rack stanchion was applied at the bottom. And<br />

third, a pushing mechanism was applied to the bottom of the shear wall by means of two long<br />

adjustable <strong>steel</strong> beams. The load was applied by using a hydraulic jack with 700mm clearance<br />

from the wall. Underneath the jack, a 200 kN load cell was installed. To monitor the<br />

movements and deflections three dial gauges were installed along the surface of the specimen<br />

(Figure 15).<br />

<strong>Michael</strong> <strong>Siegwart</strong> 4


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School of the Built Environment<br />

Research<br />

REPAIR<br />

Sample 1-40 and Sample 2-40 could not be repaired since the achieved crack opening was too<br />

small due to the failure of the supporting rack. Samples 1-30 to 2-30 were repaired by means<br />

of resin injection in the failure cracks. Thereafter <strong>steel</strong> shear strips, <strong>steel</strong> shear plates and glass<br />

fibers were externally bonded onto the beams to strengthen them.<br />


The tension and shear cracks were injected using TamRez 210 . Before the cracks were<br />

sealed the surface area around them was cleaned mechanically. Thereafter, holes were drilled<br />

along the major cracks at distance of approximately 10 cm. The sealant (TamRez 310) was<br />

placed over the cleaned area. Tam plastic injection ports were then glued, using TamRez<br />

310, over the drilled holes (Figure 14). The bond of the injection ports to the concrete failed<br />

during the injection process after about 40 seconds, although the pressure was only 3 bar. The<br />

resin came out of small cracks around the injection ports. The degree of filling by the resin is<br />

therefore assumed to be very low and mainly dependent upon capillary effects rather than<br />

injection pressure. An investigation of the specimen using the ultrasonic method, in order to<br />

prove filling of cracks, did not succeed.<br />


Sample 1-30 was the strengthened by means of two shallow shear plates that were bonded on<br />

the surface of both sides of the beam by means of TamRez 220. To achieve adequate bond<br />

the plates were pressed onto the surface of the sample using weights until the resin was cured<br />

(Figure 16, Figure 17).<br />

Sample 2-30 was strengthened against shear failure using shear strips. The strips were placed<br />

above the surface using a cover meter in the same spacing of 120 mm. The joint to the shear<br />

wall was covered by means of T-shaped <strong>steel</strong> plates The dimensions were 30 mm x 300 mm<br />

for the beam section and 45 mm x 500 mm for the wall section. The plate thickness was 3<br />

mm. The <strong>steel</strong> was the same as used for the shear strips (Figure 18).<br />

<strong>Michael</strong> <strong>Siegwart</strong> 5


- Jordanstown -<br />

School of the Built Environment<br />

Research<br />

Sample 3-30 was strengthened using the Tyfo Fibrwrap System. Two layers of glass<br />

<strong>fibre</strong>s (TyfoS / SEH) were wrapped around the beam section. The joint was strengthened<br />

using two layers of Tyfo BC. The glass <strong>fibre</strong>s were pre-cut and manually saturated by<br />

means of epoxy resin Tyfo S. The dimensions of the T-shaped Tyfo BC layers were 100<br />

mm x 500 mm bonded to the shear wall section and 100 mm x 300 mm bonded to the beam<br />

section of the specimen (Figure 19).<br />

The installation was carried out according the proposal of Fyfe Co. LLC, USA. The beam was<br />

wrapped in such a way that both sides and the underside were covered by the TyfoS / SEH<br />

glass <strong>fibre</strong>s. The surface was not covered in order to simulate a non-accessible surface. The<br />

<strong>fibre</strong>s were allocated vertical direction in order to strengthen against shear failure. Therefore<br />

the effect of the layers bonded onto the underside (flexure) is likely to be marginal. The<br />

Tyfo BC glass <strong>fibre</strong>s are allocated in a grid of 45 degrees inclined against the horizontal in<br />

each direction in order to transfer the forces from the beam to the shear wall. The thickness of<br />

one layers (Tyfo BC and TyfoS / SEH) was approximately 1 mm. Before the glass <strong>fibre</strong>s<br />

were installed the surface of the specimen was cleaned using a needle gun. Dirt and dust was<br />

removed by means of vacuum cleaning. The surface was coated using the epoxy resin Tyfo<br />

S before the glass <strong>fibre</strong>s were bonded onto the specimen. After one day, the saturated <strong>fibre</strong>s<br />

were bonded onto the surface. The <strong>fibre</strong>s were not anchored. Due to the nature of the<br />

installation process, which does not require any clamping of the bonded material, the<br />

specimen was repaired in its testing position.<br />


Sample 1-30<br />

The main cracks during the first test were a tension crack in the joint to the shear wall and a<br />

diagonal shear crack in the beam section (Figure 20). The crack width reached during the first<br />

test is very small. Only crack 13 reached a width of 0,2 mm at a load of 73 kN. The vertical<br />

displacement is high compared to Sample 2-30 and Sample 3-30. The sample was repaired by<br />

means of an externally bonded shear plate. The repair was effective although the calculated<br />

load capacity was not reached since the joint to the shear wall failed at a load of 84 kN. No<br />

cracks occurred until the load of 42 kN was reached then a flexural crack opened at a distance<br />

<strong>Michael</strong> <strong>Siegwart</strong> 6


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School of the Built Environment<br />

Research<br />

of 15 cm from the shear wall section until the shear plate was reached. The crack opened at a<br />

place that was previously undamaged. The reason for this is the difference in the initial<br />

stiffness due to the shear plate. However, as the load increased to 48 kN hairline cracks<br />

appeared at the border to the <strong>steel</strong> plate in the lower part of the T-shaped end section of the<br />

shear plate in the resin layer. The cracks were found from the middle axis downwards. No<br />

other cracks developed. The sample failed suddenly at a load of 84 kN. The failure occurred<br />

in the concrete. The bond of the plate to the concrete did not fail (Figure 22). The ultimate<br />

capacity of the reference sample (sample 3-30) was reached at a load of 80 kN. The test of<br />

sample 1-30 was stopped at a load of 74 kN.<br />

Sample 2-30<br />

The first crack, crack 1 occurred at a load of 28 kN at the joint to the shear wall. This crack<br />

proceeded further as the load increased and reached its final length of 25 cm at a load of 42<br />

kN. The crack opened wider as the load increased. The crack width was 0,6mm at a load of 71<br />

kN. The early occurrence of a tension crack in the shear wall can be put down to the fact of a<br />

much stiffer test set-up as for sample 1-30. However at 30 kN two further cracks, crack 2 and<br />

crack 3 occurred. Crack 2 stopped to increase at a load of 56 kN. The crack opening was<br />

between 0,1 mm and 0,2 mm. Crack 3 increased until 60 kN were reached. At this load stage<br />

a 12 cm long shear crack grew of crack 3 towards the bottom face of the beam. At a load of<br />

50 kN the last tension crack, crack 5 developed from the bottom face of the beam. This crack<br />

did not increase any further. As the load increased by 2 kN to 52 kN the diagonal shear crack,<br />

crack 6, started to develop. It stopped at a load of 70 kN at a distance of 3 cm from the top<br />

face of the beam. As the load increased to 72 kN spalling of the concrete cover occurred at<br />

crack 6 in the middle axis of the beam. The slope of the test graph became 0 so that the test<br />

was stopped. The displacement of the beam increased at a load of 30 kN from 2,5 mm to 6<br />

mm. This was due to the uplift of the supporting rack due to the insufficient lateral support of<br />

the shear wall section.<br />

Sample 2-30 was externally <strong>reinforced</strong> by means of high yield <strong>steel</strong> strips for shear. Although<br />

the dimensions of the shear strips were small compared to the shear plate of sample 1-30, the<br />

repair was successful. A flexural crack occurred between the joint plate and the first shear<br />

strip of the beam section at a load of 26 kN. It increased to a length of 15 cm as the load was<br />

<strong>Michael</strong> <strong>Siegwart</strong> 7


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School of the Built Environment<br />

Research<br />

increased to 34 kN. When the load reached 56 kN the crack width between the T-plate and the<br />

shear strip increased further.<br />

The original shear crack (crack 6) that was repaired by means of resin injection reopened at a<br />

load of 60 kN. This did not affect the performance of the beam since the stiffness did not<br />

decrease. The failure occurred at a load of 82 kN. The initial crack between the joint plate and<br />

the first shear strip increased in its length. It stopped 5 cm from the top face of the beam. The<br />

opening of the crack was 3 mm (Figure 23).<br />

Sample 3-30<br />

The tension crack in the joint of the beam occurred at a load of 22 kN. It increased until a load<br />

of 30 kN was reached. The crack length was 20 cm at this load stage. As the load increase the<br />

crack width increased to 1 mm at 72 kN. Cracks 2, 3, 4 and 5 occurred at 40 kN. Crack 3 did<br />

not proceed any further as its initial length of 7 cm. Crack 2 did not proceed further as well.<br />

At a load of 48 kN crack 4 reached its final length of 14 cm and crack 6 occurred. As the load<br />

increased to 68 kN the crack length of crack 6 increased to its final length of 25 cm. The<br />

diagonal shear crack occurred at a load of 52 kN and reached its final length of 40 cm at a<br />

load of 62 kN. The crack opened wider as the load increased. It reached a width of 1mm. At a<br />

load of 80 kN the sample failed at the beam joint to the shear wall and the slope of the test<br />

graph became zero. The early occurrence of a tension crack in the shear wall can be put down<br />

to the fact that there was very effective lateral support. As the load was taken away the cracks<br />

closed and were only visible as hairline cracks on the surface of the beam. The crack at the<br />

joint and the shear crack (crack 1 and crack 7) did not, however, close as far. The crack<br />

opening of the latter cracks after the load was taken away were 0,5mm. Sample 3-30 was the<br />

only specimen that reached a wide opening of cracks at its failure load.<br />

It was repaired by means of wrapped glass <strong>fibre</strong>s. The wrapping was done in such a way that<br />

made the observation of crack development in the beam section not possible since the side<br />

section and the bottom section of the beam were fully covered. As the load reached 20 kN and<br />

was increased, a cracking sound could be heard. This had, however, no influence on the<br />

stiffness since the slope of the load/deflection curve did not change. At a load of 86 kN<br />

Sample 3-30 failed suddenly at the joint of the beam to the shear wall. The failure occurred<br />

similar to that in Sample 1-30. The external reinforcement did not fail. The failure occurred<br />

<strong>Michael</strong> <strong>Siegwart</strong> 8


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School of the Built Environment<br />

Research<br />

due to tension failure in the concrete in the shear wall section underneath the T-shaped glass<br />

<strong>fibre</strong> (Figure 24).<br />


The tests have shown the ways in which way different structural repair and strengthening<br />

methods are suitable to restore the structural strength and stiffness of damaged <strong>reinforced</strong><br />

concrete structures. The test elucidated the complex behaviour of a coupled shear wall system<br />

under static loading conditions.<br />

Sample 1-30, Sample 2-30 and Sample 3-30 are compared under consideration of different<br />

aspects. The stiffness, ultimate strength, the plate bonding by means of shallow shear plates<br />

and shear strips and the bonding of glass <strong>fibre</strong>s and the effect of resin injection are now<br />

discussed.<br />

Stiffness<br />

The initial stiffness is evaluated using the deflection measured at a load of 20 kN. The final<br />

stiffness is found by dividing the load at failure by the deflection at this load stage.<br />

In the original test of Sample 1-30 the corrected initial stiffness was 100 % higher than in all<br />

other tests procedures. This can be put down to the fact that there was provided a stronger<br />

vertical support for the tests of the other samples (Graph 1).<br />

The initial stiffness of Sample 1-30, Sample 2-30 and Sample 3-30 increased after repair. The<br />

shallow shear plates of Sample 1-30 gave the best performance since the stiffness increased<br />

by 124 % compared to the original. Sample 3-30 increased by 83 % in its initial stiffness. The<br />

stiffness of Sample 2-30 increased by only 16 %. This behaviour can be explained when the<br />

repair mechanisms are examined. Sample 1-30 and Sample 3-30 had strong shear<br />

reinforcement after repair. The samples were over-<strong>reinforced</strong>. The opening of previous shear<br />

and tension cracks had no influence on the stiffness of the specimens since the load was<br />

completely carried by the additional reinforcement. Sample 2-30 carried weak external<br />

reinforcement. The shear strips enabled the opening of unrepaired cracks, so that the stiffness<br />

could not be increased to the level of the other specimens.<br />

<strong>Michael</strong> <strong>Siegwart</strong> 9


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Research<br />

These results can be explained as follows. The initial tests of Sample 1-30 and Sample 2-30<br />

did not load the specimen until failure. Therefore Sample 2-30 with the weakest<br />

reinforcement reached the best performance of all specimens. The shear plate of Sample 1-30<br />

transformed the forces from the beam into the shear wall. The shear wall section was weaker<br />

than the beam section. Hence the final stiffness was only 117 %. Sample 3-30 was the only<br />

specimen that was tested providing full vertical and lateral support. It was the only sample<br />

that was overloaded. The loss in the final stiffness can be explained because of the elongation<br />

of the glass <strong>fibre</strong> material that is higher than that of <strong>steel</strong> and the successful original test that<br />

loaded the specimen until failure (Graph 2).<br />

Ultimate Strength<br />

The test of Sample 1-30 and Sample 2-30 was interrupted early so that the failure could not<br />

develop to its full extent. Therefore a comparison of the “ultimate” strength before and after<br />

repair is difficult. However, the ultimate strength of Sample 3-30 increased by 7,5 %. The<br />

failure mode of all samples was a diagonal shear failure in the beam section at the final load<br />

during the first test. This changed after repair. Sample 1-30 and 3-30 did not fail in the beam<br />

section. The failure occurred at load of 84 kN and 86 kN in the joint of the beam to the shear<br />

wall section. The failure mechanism was tension failure in the concrete. Sample 3-30 failed<br />

after repair at a load of 83,5 kN due to a flexural crack near the joint to the shear wall.<br />

From these results it can be seen that the real ultimate strength of the specimen was in the<br />

range of 80 kN compared to calculated 72 kN. The real ultimate load was only reached by<br />

Sample 3-30. However the repair methods were suitable to increase the ultimate load capacity<br />

of the specimen. The tension plate determined the ultimate loading capacity after repair over<br />

the joint to the shear wall. The dimensions of the tension plates used for Sample 1-30 and<br />

Sample 2-30 were the same. Therefore, the ultimate loading capacities of Sample 1-30 and<br />

Sample 2-30 are similar 84 kN and 83,5 kN. The ultimate load capacity of Sample 3-30 was<br />

greater because the area of the tension glass <strong>fibre</strong> web was greater than for the other samples.<br />

The area for Sample 3-30 was 10 x 50 + 10 x 30 = 800 cmÄ compared to 4 x 50 + 3.5 x 30 =<br />

305 cmÄ for Sample 1-30 and Sample 2-30.<br />

<strong>Michael</strong> <strong>Siegwart</strong> 10


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Research<br />

Resin injection<br />

The resin injection was only carried out successfully for Sample 3-30. The crack width of this<br />

sample was wide enough to enable the full penetration of the crack. This was visible after the<br />

coating was removed.<br />

Steel Shear Plate and Steel Shear Strips<br />

The failure of Sample 1-30 did not occur in the beam nor in the bonded <strong>steel</strong> plates. However<br />

the quantity of <strong>steel</strong> that was used to reinforce the sample was quite considerable (overreinforcement).<br />

Sample 2-30 reached similar results with much less <strong>steel</strong>. In order to reach<br />

maximum bond of the <strong>steel</strong> plates the installation of the plates and strips was done whilst the<br />

samples were lying on the structural floor (Figure 17). This is not possible in situ.<br />

Glass <strong>fibre</strong>s<br />

The main advantage of the applied glass <strong>fibre</strong> system Tyfo SEH 51 É was its easy<br />

application. Sample 3-30 remained in its upward testing position whilst the repair process was<br />

carried out. The installation process would have been similar for real structures (Figure 21).<br />

The glass <strong>fibre</strong> layers were very thin so that voids and air bubbles, which would reduce the<br />

performance were visible. The ultimate load was the highest of the three samples. The reason<br />

for the reduced final stiffness of the sample is complex due to a combination of various<br />

factors. Sample 3-30 was the only sample that reached its ultimate load and failed certainly.<br />

The voids were not repaired as recommended by the manufacturer.<br />

<strong>Michael</strong> <strong>Siegwart</strong> 11


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Conclusion<br />

Conclusion<br />

The experiments were carried out in order to gain an understanding of the complex behaviour<br />

of the beam coupling shear wall structures. The effectiveness of resin injection and externally<br />

bonded <strong>steel</strong> plates and glass <strong>fibre</strong>s were investigated and compared. From this experimental<br />

work, a number of conclusions could be derived.<br />

Reinforced concrete sections, namely <strong>reinforced</strong> concrete coupling beams to shear walls, are<br />

suitable for the transformation of lateral forces from shear wall section to shear wall section in<br />

a coupled system. The beams dissipate energy that is created by such events as earthquakes by<br />

developing hinges either in the beam or in the joint to the shear wall. This is dependent upon<br />

the embedment length and strength of the beam.<br />

The repaired samples were able to resist a higher static load than in the first test. This can be<br />

put down to the fact that the structural strengthening measures were accompanied by the resin<br />

injection.<br />

The stiffness of the samples that were strengthened by means of externally bonded metal<br />

plates (resin TamRez 220É) increased between 17 % and 43 % compared to the original. This<br />

can be explained regarding the incomplete damage that was reached during the first test of the<br />

samples. The fully loaded and damaged Sample 3-30 was restored to 80 % of its original<br />

stiffness by means of the bonded glass <strong>fibre</strong> system Tyfo SEH 51É.<br />

The application of the glass <strong>fibre</strong> system is quick and simple since the installation and<br />

preparation process is simple compared to externally bonded <strong>steel</strong> plates. Defects in the bond<br />

are easy to detect since they are visible.<br />

The effectiveness of resin injection is well known but could not been proven by this<br />

investigation due to unsuitable injection procedure, and the fact that each sample that was<br />

resin injected was also strengthened.<br />

<strong>Michael</strong> <strong>Siegwart</strong> 12


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References<br />


[1]<br />

Abu Tair A.I., Burley E., Rigden S.R.,<br />

“The effectiveness of the resin injection repair method for cracked RC beams”<br />

The Structural Engineer, Volume 69, No. 19, 1 October 1991, pp 335-341<br />

[2]<br />

Adin, Moshe A., Yankelewsky, David Z., Farhey, Daniel N.<br />

“Cyclic behaviour of epoxy-repaired <strong>reinforced</strong> concrete beam column joints”<br />

ACI Structural Journal, March- April 93, pp 170 - 179<br />

[3]<br />

Allen, R. T. L,<br />

“The Repair of Concrete Structures”,<br />

Blachie & Son Ltd, 1993<br />

[4]<br />

Ajay Singhal, Anne S. Kiremidjian<br />

“Method for probabilistic evaluation of seismic structural damage”<br />

Journal of Structural Engineering, December 1996, pp1459-1467<br />

[5]<br />

Alexandrou A. , Beckett D.,<br />

“An Introduction to Eurocode 2: Design of concrete structures – including seismic actions”<br />

University of Greenwich, Faculty of the Built Environment 1993, p 171,<br />

UUJ Shelf 624.1834<br />

[6]<br />

Chaallai O., Gauthier D., Malenfant P.,<br />

“Classification methodology for coupled shear walls”;<br />

Journal of Structural Engineering, December 1996; pp1453-1458<br />

[7]<br />

DoE, Teychenn DC., (David Clayton),<br />

“Design of normal concrete mixes”<br />

Building research establishment, 1975<br />

[8]<br />

EC 8, Eurocode 8<br />

“Design provisions for earthquake resistance of structures “<br />

ENV 1998-1-1: 1994, ENV 1-2: 1996, ENV 1998-1-3:1995<br />

[9]<br />

Ehsani ER., Saadatmanesh H.,<br />

“Fiber Composite Plates for strengthening bridge beams”<br />

Composite Structures 15 (1990) pp 343-355<br />

[10]<br />

Emmons, P. H. & Vaysburd, A. M.,<br />

“Factors affecting durability of concrete repair - The contractor’s viewpoint”;<br />

Structural Faults + Repair-93, Vol. 2, PP 253 – 267<br />

[11]<br />

Farmer Neil, Gee Tony,<br />

“Strengthening with CFRP <strong>laminates</strong>”<br />

Construction Repair, January/February 1997, pp2-4<br />

[12]<br />

FYFE CO: “TyfoÉ Systems For Beams and Slabs”,<br />

manufactures manual, Fyfe Co. L.L.C., “The FibrewrapÉ Company”, 6044 Cornerstone<br />

Court West, Suite C, San Diego, CA 92121-4730<br />

[13]<br />

Harries K.A., Mitchell D., Cook W.D., Redwood G.R.,<br />

“Seismic response of <strong>steel</strong> beams coupling concrete walls”<br />

Journal of Structural Engineering, Vol. 119, No 12, December 1993, pp3611-3629<br />

<strong>Michael</strong> <strong>Siegwart</strong> 13


- Jordanstown -<br />

School of the Built Environment<br />

References<br />

[14]<br />

Holl C.H., OÄConnor A.S.;<br />

“Cleaning and Preparing Concrete before repair”<br />

Concrete International, March 1997, pp60-63<br />

[15]<br />

Husain, M., Sharif Alfarabi, Basunbul, I.A. Baluch, M.H., Al-Sulaimani G.J.<br />

“Flexural Behaviour of Precracked Reinforced Concrete Beams Strengthened Externally by<br />

Steel Plates”,<br />

ACI Structural Journal, Vol. 92, No. 1, January-February 1995, pp14-22<br />

[16]<br />

ICBO Evaluation Service, Inc.<br />

“Acceptance Criteria for concrete and <strong>reinforced</strong> and un<strong>reinforced</strong> masonry strengthening<br />

using <strong>fibre</strong> <strong>reinforced</strong>, composite systems”<br />

International Conference of Building Officials, AC 125, April 1997<br />

[17]<br />

Kay EA.,<br />

“The European Standard on Concrete repair principles”<br />

Construction Repair: Concrete Repairs 6, January/February 1997, pp 52-55<br />

[18]<br />

Kwan A.K.H.,<br />

“Local deformations and rotational degrees of freedom at beam-wall joints”<br />

Computers and Structures,1993, Vol. 48, No. 4, pp615-625<br />

[19]<br />

Kabeyasawa, T., Shiorara, H., and Otani, S. (1984).<br />

“U.S.-Japan co-operative research on RC full scale building test-Part 5: discussion on<br />

dynamic response system.”<br />

Proc., 8 th World Con. on Earthquake Engrg., 6.Prentice Hall, Inc., Englewood Cliffs, N.J.<br />

Paulay, T.<br />

“Coupling beams of <strong>reinforced</strong> concrete shear walls”<br />

Journal of the Structural Division, Proc.ASCE, 97, No. ST3, March 1971, pp843-861<br />

Queens University TA 680A5<br />

Schnobrich, WC (1977).<br />

“Behaviour of RC structures predicted by finite element method.”<br />

Comp. and Struct., 7(3),pp365-376<br />

Wight, J.K. (1988).<br />

“Earthquake design compared to measured response”<br />

Journal of Structural Engineering , ASCE, Volume 112 (1), pp149-164<br />

[20]<br />

Lane JS., Leeming, M.B.,<br />

“Testing of strengthened <strong>reinforced</strong> and prestressed concrete beams”,<br />

Construction Repair, January/February 1997, pp10-13<br />

[21]<br />

Museum of San Francisco<br />

“Damage after the 1906 earthquake”,<br />

Internetpage by the Museum of San Francisco<br />

[22]<br />

Moehle J. P., Mahin S. A.<br />

“Observations on the behaviour of <strong>reinforced</strong> concrete buildings during earthquakes”<br />

National Information Service for Earthquake Engineering,<br />

Internetpage of the University of California, Berkley<br />

[23]<br />

Norris T., Saadatmanesh H., Ehsani RM.,<br />

“Shear and flexural strengthening or R/C beams with carbon <strong>fibre</strong> sheets”<br />

Journal of Structural Engineering, July 1997, pp 903-911<br />

<strong>Michael</strong> <strong>Siegwart</strong> 14


- Jordanstown -<br />

School of the Built Environment<br />

References<br />

[24]<br />

Park R., Paulay T.;<br />

“Reinforced Concrete Structures”,<br />

Pub. John Wiley & Sons 1975, UUJ shelf no. 624.18341/PAR, pp628, 629, 639, 645, 652,<br />

[25]<br />

Perkins, PH.,<br />

“Repair, Protection and Waterproofing of Concrete Structures” ,<br />

E&FN Spoon 3 rd edit, ISBN 0-419-202-803, UUJ-Library 624.1834 / Per , pp 45-65<br />

[26]<br />

Reynolds C.E., Steedman J.C.,<br />

“Reinforced concrete Designer’s Handbook”,.<br />

E.&F. N. Spoon, Tenth Edition Table 143, p 335<br />

[27]<br />

Roberts, T.M.,<br />

“Approximate Analysis of the Shear and Normal Stress Concentrations in the Adhesive Layer<br />

of the Plated RC Beams”,<br />

Structural Engineer, V.67, No.12, June 20, 1989, pp229-233<br />

[28]<br />

Robery, Peter,<br />

“Maintenance and repair strategies”,<br />

Construction Repair –Concrete Repairs 6- Vol. 11, No. 2, March/April 1997, pp 33–38<br />

[29]<br />

Subedi N.K.,<br />

“Ultimate strength analysis of <strong>reinforced</strong> concrete coupling beams”<br />

The Structural Engineer, Volume 68, No. 3, 6 th February 1990, pp45 –50<br />

[30]<br />

Subedi K.N.;<br />

“RC-coupled shear wall structures. I: analysis of coupling beams”,<br />

Journal of Structural Engineering, March 1991, Vol. 3, pp667-680<br />

[31]<br />

Subedi K.N.;<br />

“Reinforced concrete beams with plate reinforcement shear”<br />

Proc. Inst. Civ. Engrs, Part 2, 1989, 87, Sept., pp 377-379<br />

[32]<br />

TÅljsten BjÇrn,<br />

“Defining anchor lengths of <strong>steel</strong> and CFRP plates bonded to concrete”,<br />

International Journal of Adhesion and Adhesives, Volume 17, Number 4, 1997, pp319-327<br />

[33]<br />

TÅljsten, BjÇrn;<br />

“Strengthening of beams by plate bonding”<br />

Journal of Material in Civil Engineering, November 1997, pp206-212<br />

[34]<br />

University of Bristol, Faculty of Engineering,<br />

http://www.fen.bris.ac.uk/faculty/copyrght.htm<br />

[35]<br />

University of Bristol, “earthquake design” Internetpage<br />

<strong>Michael</strong> <strong>Siegwart</strong> 15


- Jordanstown -<br />

School of the Built Environment<br />

Illustrations<br />

Figure 1 Building subjected to lateral load<br />

Figure 2 damaged concrete beam<br />

Figure 4 types of shear walls<br />

a) cantilever shear wall b) coupled shear wall c) slit shear wall<br />

Canadian Concrete Standard CSA 1994 Eurocode 8 (Prestandard)<br />

M 0 =M 1 +M 2 +P x L<br />

M 0 =M 1 +M 2 + D x N<br />

DC = P x L / M 0 (DC= 1/a s ) D x N / M 0<br />

condsidered as fully coupled:<br />

Treat as wall if:<br />

DC > 0.66 1.0 > D x N / M 0 < 2/3 (=0.66)<br />

condsidered as partially coupled:<br />

Treat as coupled shear wall if:<br />

DC < 0.66 2/3 (=0.66) > D x N / M 0 < 1/3 (=0.33)<br />

minimum for efficient coupling:<br />

Treat as frame:<br />

DC = 0.33 1/3 (=0.33) > D x N / M 0<br />

Figure 3 Location of internal compression resultant<br />

in flanged low-rise shear wall [24]<br />

Figure 5 Shear failure of low-rise flanged shear wall [24]<br />

<strong>Michael</strong> <strong>Siegwart</strong> 16


- Jordanstown -<br />

School of the Built Environment<br />

Illustrations<br />

Figure 7 Flexural deformation of beam and forces [30]<br />

Figure 6 close-up of coupling<br />

beams in the Mount McKinley<br />

Building in Anchorage [24]<br />

Figure 8 shear deformation of beam [30]<br />

Figure 9 combined shear and flexural actions,<br />

final stage [31]<br />

Figure 10 Local stress concentrations and deformations<br />

around beam-wall joint [18]<br />

<strong>Michael</strong> <strong>Siegwart</strong> 17


- Jordanstown -<br />

School of the Built Environment<br />

Illustrations<br />

Evaluation<br />

Repair<br />

Analysis<br />

Repair<br />

Strategy<br />

User<br />

Needs<br />

Cause<br />

?<br />

Scope<br />

Effect<br />

?<br />

S c o p e<br />

Useful Life<br />

Urgency<br />

Cost<br />

Technical<br />

Performance<br />

Requirements<br />

Structural Needs<br />

Effect of Repair<br />

on Structure<br />

Constructibility<br />

Environment<br />

Yes<br />

Protection / Appearance<br />

(Cosmetic)<br />

Surface Repair<br />

Both<br />

Yes<br />

Load Carrying<br />

(Structural)<br />

Aesthetics<br />

Safety<br />

Barrier to<br />

unwanted<br />

Environment<br />

Aesthetic<br />

Water<br />

resistant<br />

Live<br />

Loads<br />

Impact<br />

Loads<br />

Dead<br />

Loads<br />

Figure 11Performance Requirements [10]<br />




EC 2<br />

BS 8110<br />

1-40 and 2-40 1-30 to 3-30 140 and 2-40 1-30 to 3-30<br />

SHEAR 63.3 kN 51.6 kN 69.0 kN 55.0 kN<br />

ULTIMATE SHEAR 98.8 kN 72.2 kN 75.0 kN 60.0 kN<br />

TENSION 81.2 kN 63.8 kN 85.1 kN 62.0 kN<br />

Table 1 Loading capacities of the specimen according to EC 2 and BS 8110<br />

<strong>Michael</strong> <strong>Siegwart</strong> 18


- Jordanstown -<br />

School of the Built Environment<br />

Illustrations<br />

Figure 12 Specimen 1-30 to 3-30 (reinforcement)<br />

Figure 13 Specimen 1-40 and 2-40 (reinforcement)<br />

<strong>Michael</strong> <strong>Siegwart</strong> 19


- Jordanstown -<br />

School of the Built Environment<br />

Illustrations<br />

Figure 15 final test set-up<br />

Figure 14 Sealed cracks with injection ports<br />

Figure 16 Sample 1-30 with shallow shear plate<br />

Figure 17 Installation of shear plates<br />

Figure 18 Sample 2-30 (shear strips)<br />

Figure 19 Sample 3.30 (glass <strong>fibre</strong>s)<br />

<strong>Michael</strong> <strong>Siegwart</strong> 20


- Jordanstown -<br />

School of the Built Environment<br />

Illustrations<br />

Figure 21 installation process (glass <strong>fibre</strong>s)<br />

Figure 20 Crack pattern sample 1-30<br />

Figure 22 Sample 1-30 failure<br />

Figure 23 Failure Sample 2-30<br />

Figure 24 Sample 3-30 (Failure<br />

in beam joint to shear wall)<br />

<strong>Michael</strong> <strong>Siegwart</strong> 21


- Jordanstown -<br />

School of the Built Environment<br />

Illustrations<br />

Sample 1-30 Sample 2-30 Sample 3-30<br />

Load [kN]<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

0<br />

0 5 10 15 20 25<br />

Displacement [mm]<br />

Graph 1 Test Results Sample 1-30, 2-30 and 3-30 before repair<br />

Load [kN]<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

0<br />

Sample 1-30 (T-Plate)<br />

Sample 3-30 (glass <strong>fibre</strong>)<br />

Sample 2-30 (Strips)<br />

0 5 10 15 20 25<br />

Displacement [mm]<br />

Graph 2 Test Results Sample 1-30, 2-30 and 3-30 after repair<br />

Reference Curve<br />

<strong>Michael</strong> <strong>Siegwart</strong> 22

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