Design for Service Life, Bridge Birth Certificate & Concrete ...

Design for Service Life,
Bridge Birth Certificate &
Concrete Structures
Management Concepts
Presented by: Mike Bartholomew, PE
CH2M HILL
AASHTO Bridge Sub-Committee Meeting
T-9 – Technical Committee for Bridge
Preservation
July 6, 2009
New Orleans, LA
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Discussion Topics
Service Life Design
– Work Being Done in Europe
– Current US Practice
– Exposure Conditions
– Deterioration Mechanisms / Protection Systems
– Mathematical Modeling
– Limit States / Design Process
Bridge Birth Certificate
– Purpose
– Documentation Examples & Templates
– Integration with Inventory Management
Systems
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fédération
internationale du béton
(The International Federation for
Structural Concrete)
Writing new Model Code to include
Service Life Design
Publication of 1 st draft scheduled for
The Third International fib Congress
– Washington, DC
– May 29 to June 3, 2010
3

fib Commission 5:
Structural Service Life Aspects
Some key areas of interest
– Probabilistic performance based service
life design.
– Service life management.
– Inspection, assessment and
performance monitoring.
– Development and validation of
deterioration mechanisms.
4

What do these Bridges have in
common?
5

Answer
Although not similar in:
– Structure Type
– Materials
– Age
– Geographic Locations
They are all:
– Deteriorating with time
6

Service Life (Durability) Design
fib Bulletin 34 – Model Code for Service
Life Design (2006)
Establishes design procedures
– to Resist Deterioration
– from Environmental Actions
In 4 Levels of Design
– Full Probabilistic
– Partial Factor
– “Deemed to Satisfy”
– Avoidance of Deterioration
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AASHTO LRFD Service Life
(Durability) Design Requirements
2.5.2.1.1 – The contract documents
shall call for quality materials and for
the application of high standards of
fabrication and erection.
Structural steel shall be self
protecting or have long-life life coating
systems or cathodic protection.
8

AASHTO LRFD Service Life
Design Requirements
C2.5.2.1.1 – The intent of this Article
is to recognize the significance of
corrosion and deterioration of
structural materials to the long-term
performance of a bridge.
Durability also mentioned in C5.4.2.1
and 5.12.1.
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AASHTO LRFD Service Life
Design Requirements
Expectations for durability exist
All recommendations qualify as
“deemed to satisfy” requirements
Code gives no guidance on how long
a structure should remain in service
Lacks models for prediction of
deterioration of structures
No metrics to define if a durable
design is achieved
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Service Life Design Basics
Establishing Life Expectancy
Identifying
– Environmental Exposure Conditions
– Deterioration Mechanisms
– Material Resistance to Deterioration
Establishing Mathematical Modeling
Parameters to Predict Deterioration
Setting Acceptable Damage Limits
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Life Expectancy
AASHTO LRFD Bridge Design
Specifications – Section 1.2
– Design Life – Period of time on which
the statistical derivation of transient
loads is based – 75 years for these
Specifications.
– Service Life – The period of time that
the bridge is expected to be in
operation.
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What’s s a Reasonable Service Life?
50, 75, 100, 150 years, … more?
Expected Service Life is based on
– Owner’s s desires and expectations
Actual Service Life will depend on
– Exposure conditions of structure
– Quality of materials, design and
construction
– Level of maintenance performed
13

Indicative Values for
Design Service Life – fib Bulletin 34
Design Service
Life, yrs
Examples
10 Temporary Structures
(Structures or parts of structures that can be dismantled with a
view to being re-used are not to be considered temporary)
10-25
Replaceable structure parts, e.g.,
gantry girders, bearings
15-30
Agricultural and similar structures
50 Buildings and other common
structures
100 Monumental buildings, bridges, and
other civil engineering structures
14

Service Life Designed Structures
Great Belt Bridge, Denmark (100
yrs)
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Service Life Designed Structures
Confederation Bridge, Canada (100
yrs)
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Service Life Designed Structures
San Francisco – Oakland Bay Bridge
(150 yrs)
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What About These Structures?
Representing the majority of the
600,000+ Bridges in the US
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Exposure Conditions
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Site Exposure Conditions
Aggressivity of Environment
– Sea water
– De-icing agents
– Chemical attack
Temperature / Humidity
– Freeze / thaw cycles
– Wet / Dry cycles
– Tropical (every +10º C doubles rate of
corrosion)
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Member Exposure Conditions
Marine
– Submerged, tidal, splash, atmospheric
zones
Geographic Orientation
– N-S-E-W, seaward, landward
Surface Orientation
– Ponding, , condensation, protection from
wetting, corners
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Exposure Classes –
European Standard EN-206
206-1
Class
X0
XC1-XC4
XC4
XD1-XD3
XD3
XS1-XS3
XS3
XF1-XF4
XF4
XA1-XA3
XA3
Description
No Risk of Corrosion or Attack
Corrosion Induced by Carbonation
Corrosion induced by chlorides other
than from sea water
Corrosion induced by chlorides from
sea water
Freeze/thaw attack with or without de-
icing agents
Chemical attack
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Deterioration
Nothing lasts forever
Every material deteriorates at a
unique rate
Deterioration rate is dependent on
exposure conditions
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Deterioration Mechanisms
Reinforced Concrete
– Chloride Induced Corrosion
(Seawater, de-icing salts)
– Carbonation Induced Corrosion
(Normal CO 2 from atmosphere)
24

Deterioration Mechanisms
Structural Steel
– Corrosion after Breakdown of Protective
Coating Systems
25

Protection Systems
Material’s s Own Ability to Resist
Deterioration – Concrete Quality
(Permeability) and Cover
Protective Coatings
Membranes & Overlays
26

Deterioration Models
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Chloride Induced Corrosion Models
Fick’s 2 nd Law Models Time to Initiate Corrosion in
Uncracked Concrete
C crit Cx ( covt , ) C o ( C s , Δx − C o )
⎛ ⎛ cov − Δx ⎞⎞
+
⋅⎜
1 − erf⎜
⎟⎟
⎝ ⎝ 2⋅
D app , C ⋅t
⎠⎠
C(x,t)
erf
C crit
C o
C s,Δx
cov
D app,C
Chloride concentration at depth & time
Mathematical error function
Critical chloride content (to initiate corrosion)
Initial chloride content of the concrete
Chloride concentration at surface or depth Δx
Depth of concrete cover
Apparent coefficient of chloride diffusion in
concrete (permeability)
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Deterioration Models / Limit States
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Limit States – Reinforced Concrete
1 - Depassivation – No damage to
reinforcing / end of initiation phase,
corrosion begins
2 - Cracking – Initial expansion of
corrosion by-products
3 - Spalling – Corrosion by-products cause
loss of concrete cover and bond to
reinforcing steel
4 - Collapse – Loss of reinforcing steel
cross section from corrosion
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Limit States
Current practice for new structures is
Depassivation phase
fib Commission 5 established task
groups on June 18-19, 19, 2009 in
London to better define:
– Critical Chloride Content to cause
reinforcing steel depassivation
– Measurable limits for cracking, spalling,
and loss of section
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Structural vs. Durability Issues
Design
Design Work Item
Structural Issues
Durability Issues
Identify Owner’s
Requirements & Desires
Identify Externally Applied
Actions
Select Materials
Determine Dimensions
Summarize Results
Functionality, Capacity (#
lanes), Appearance
Loads (Self weight, Live
Loads, Wind, Thermal,
Seismic, etc.) and Load
Factors
Concrete Strength, Steel Yield
& Ductility and Resistance
Factors
Spans, Component cross
sections
Construction Plans &
Specifications, Engineer’s
Cost Estimate, Calculation
Books
Target Service Life
Environmental actions
(chloride attack, carbonation,
freeze-thaw, chemical attack,
etc.)
Chloride diffusion coefficient
in concrete, reinforcing steel
type & coating (plain, epoxy
coated, stainless)
Cover dimensions
Durability Report (initiate
Birth Certificate),
Construction Specifications
(new Diffusion Coefficient
testing), Engineer’s s Cost
Estimate
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What is Needed to Implement a
Service Life Design Process?
Further Development of
– Deterioration Models (especially for
Propagation phase)
– Limit States for Acceptable Damage (including
critical chloride content)
Creating Design Examples / Workshops
Transfer Concrete Service Life Design
Process to Steel and Other Materials
Get the Attention of FHWA & AASHTO
State Bridge Engineers
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Birth Certificate
fib New Model Code chapter 2, will
define a Birth Certificate.
A document, report or technical file (depending on the size and
complexity of the structure concerned) containing engineering
information formally defining the form and the condition of the structure
after construction. The document / report should provide specific details
on parameters important to the durability and service life of the structure
concerned (e.g. cover to reinforcement, concrete permeability,
environmental conditions, quality of workmanship achieved etc) and the
basis upon which future knowledge of through-life performance should
be recorded. This framework should provide a means of comparing
actual behaviour / performance with that anticipated at the time of design
of the structure. The document / report should facilitate ongoing
(through-life) evaluation of the service life which is likely to be achieved
by the structure.
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Birth Certificate Purpose
Contains engineering information
defining form and condition of
structure at end of construction
Documents specific parameters
affecting durability of structure
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Structural vs. Durability Issues
Construction
Construction Work Item
Structural Issues
Durability Issues
Perform, Monitor & Inspect
Work
Track Variances
Summarize Results
Verify dimensions, test &
document material strength
properties
Accept / Accept with cost
adjustment for deficiencies /
Reject
As-Built Plans, Load Rating
Verify and map cover, test &
document actual material
durability properties (chloride
diffusion coefficient, etc.)
Accept / Accept with cost
adjustment for deficiencies /
Reject
Durability Rating, update
Birth Certificate
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Birth Certificate Purpose
(continued)
Compares actual behavior /
performance with that anticipated
during design
Facilitates on-going (through-life)
evaluation of remaining service life
37

Structural vs. Durability Issues
In-Service Use
Work Item
Structural Issues
Durability Issues
Routine Visual Inspections
(Biennial – required by law)
In-Depth Monitoring (every 7-7
10 years)
Assessment
Rehabilitation/Intervention
Dismantling
To detect obvious defects
with minimal testing
Reactive – Identify problem
areas as they occur (Concrete
Cracks & Spalls, Reinforcing
Corrosion, Joint and Bearing
failure)
Change in Use/Loading or
After Significant Event
(Earthquake, Hurricane,
Flood, Fire, Explosion,
Truck/Ship Impact)
Replace/Repair/Strengthen
damaged structural
components
Demolish & Remove Waste
Same as structural
Proactive – Testing to monitor
in-service conditions (chloride
diffusion coefficient, chloride
profiles, chloride surface
concentration)
Assess Remaining Service Life
of Components
Perform Corrosion Surveys -
Add Corrosion Protection
Systems (Galvanic, Cathodic
Protection, or Electrochemical
Systems)
Recycle & Re-Use Materials
38

Birth Certificate –
Table of Contents
1) Identification of Asset
– Description & Identification of Structure
– General Plan & Typical Section Drawings
– Design Parameters / Target Service Life
2) Environmental Exposure
Conditions
3) Deterioration Models
39

Birth Certificate –
Table of Contents (continued)
4) Summary of Individual Structure
Components
– Mapping of:
Exposure Classes/Severities
Deterioration Models
Mean Material Properties
Mean Cover Dimensions
Expected Service Life (Target & Remaining)
40

Birth Certificate –
Table of Contents (continued)
5) Summary of Ancillary
(Replaceable) Components
– Mapping & Documentation (similar to
Structural Components) for:
Bearings
Expansion Joints
Protective Membrane Systems
41

Birth Certificate –
Table of Contents (continued)
6) In-Service Inspection
– Routine & Special Maintenance Schedule
– Schedule of Inspections
Routine Visual (Biennial)
In-Depth Monitoring and Sampling (7-10
years)
– Special Test Method Requirements
7) Dismantling Plan
42

Example Birth Certificate
43

Birth Certificate – Next Steps
Determine Guidelines for:
– Type and number of tests of material
durability properties
– Type and extents of as constructed
concrete cover measurements
Develop templates for additional
Deterioration Models for the Example
Birth Certificate (Carbonation)
49

Birth Certificate – Next Steps
Develop criteria for deterioration
models for Ancillary Components
(Joints & Bearings)
Develop a suggested format for
Inspection & Maintenance Schedule
(similar to automobile maintenance
schedules)
Develop a template for a Dismantling
Plan
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Concluding Remarks
Service Life Design & Inventory
Management
– Addresses the whole life of the structure
– Requires a new proactive mindset for the
industry
– Has huge potential for predicting the future
health, safety, and allocation of funding of our
infrastructure
Process in its Infancy
– Better prediction tools need to be developed
– But, we need to start somewhere
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Questions?
Thank you
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