Transcript Decision Support Tools for Life Cycle Bridge Management

Meeting of the National Round Table on Sustainable Infrastructure
March 26, 2008, Toronto
Framework for Assessment of State
Performance and Management of Canada’s
Core Public Infrastructure (CPI)
Review of State- of- Art
Outline
• Background
• Review of performance assessment of CPI
• Knowledge “deficit” in performance assessment
• Approach
Background
• CPI: roads, bridges, transit, water and wastewater systems
• Canada’s CPI enable:
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personal mobility
transport of people and goods,
provide safe drinking water
remove wastes
critical to competitiveness of economy and quality of life
• NRC Cross-Canada Tour- Concerns of decision-makers:
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aging infrastructure
lack of reliable performance data
ill-defined acceptable minimum levels of performance
few management tools
PSAB 3150 requirements
ineffective communications to decision makers
closing small towns, concerns of northern communities
Environment now on agenda- Sustainability concerns
Background
Aging CPI
Increasing
Aggressive
Climate
Systems
Demand
Environment
Change
Deterioration of Core Public Infrastructure
+
Inadequate Performance Assessment
Decreasing Capacity / Increasing Risk of Failure
Consequences:
Health & Safety problems
Economic & Social impacts
Environmental impact
Background
Challenges
• Life cycle management of CPI = challenging problem
• Optimize allocation of funds for maintenance, rehabilitation & renewal
for different CPI systems, given:
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large network of CPI systems and components
CPI systems/components deteriorate with time
risk of failure increases with time
lack of reliable data on current and future state of systems
different assets with different consequences of failure
limited funds
CPI Performance Assessment
Performance Indicators – Bridges
• Safety
– load rating, load carrying capacity, reliability index
– condition rating, sufficiency rating, appraisal rating, health index
• Serviceability
– condition rating
– excessive stresses, cracking, deformation, vibration
• Fatigue
• Functionality
– condition rating, sufficiency rating
– bridge width, vertical/horizontal clearances
CPI Performance Assessment
Performance Indicators - Bridges
Agency
FHWA
Condition rating system
9 to 0 (excellent, very good, …,
imminent, failed)
Three general ratings (deck,
superstructure and
substructure)
Pontis: 1 to 5 or 1 to 3
AASHTO
(CoRe elements)
Canada (e.g. MTO)
Based on detailed element-level
inspection (one rating per
element type)
Four conditions states : excellent,
good, fair and poor
Performance Indicator
• Appraisal ratings
• Sufficiency rating
• SD/FO classification
• Appraisal ratings
• Sufficiency rating
• SD/FO classification
• Health Index (CalTrans)
• Bridge condition index (BCI)
• Bridge sufficiency index (BSI)
Based on detailed element-level
inspection (one rating per
element type)
CPI Performance Assessment
Performance Indicators - Roads
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Riding comfort index
Surface distress index
Structural adequacy index
Pavement condition index
International roughness index
Pavement quality index
CPI Performance Assessment
Performance Indicators - Roads
Agency
MTO
Performance Indicators
- Ride Condition Rating (RCR)
- Pavement distress severity and
extent
- Pavement condition index (PCI)
Evaluation
0-10 (very poor to excellent)
6 severity levels, extent in %
0-100 (poor to excellent)
-International roughness index (IRI)
-Rutting
-Pavement cracking
Engineering units (m/km)
Alberta
-IRI
-Surface distress index (SDI)
-Structural adequacy index (SAI)
-Pavement quality Index (PQI)
Engineering units (m/km)
FHWA
IRI
Present serviceability rating (PSR)
Engineering units (m/km)
0-5 (subjective rating)
MTQ
Rutting depth
0-100 (poor to excellent)
Three ratings : wheel path,
transverse cracking and general
condition
CPI Performance Assessment
Performance Indicators – Water Systems
Failure Criteria
1)
Water Quality
Hydraulic and
Quantity of flow
System Integrity
Performance Indicator
Sub Criteria
2)
Point of Entry (POE) and
distribution guidelines
Customer Satisfaction
1)
2)
3)
4)
Residual Chlorine
Customer complaints (#)
Boil water advisories (# / time)
…
1)
2)
3)
4)
5)
Adequate Pressure
Fire Fighting Capability
Emergency Storage
Adequate Capacity
Customer Satisfaction
1)
2)
3)
4)
5)
6)
7)
Flow velocity (max)
Pressure (min/max)
Water age (>1 day)
Demand (average, peak)
Pumps and storage capacity
Water consumption/capita
Low Pressure Complaints …
1)
Minimize # and Duration of
Interruptions
Minimize Response Time
Minimize Non-Revenue Water
Maximize Efficiency
1)
2)
3)
4)
5)
# of Breaks (normalized)
# of Leaks (normalized)
Amount Non-Revenue Water
# Service interruptions
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2)
3)
4)
CPI Performance Assessment
Performance Indicators – Wastewater Systems
Failure Criteria
Quality
Sanitary/Storm
Hydraulic and
Quantity of flow
Performance Indicator
Sub Criteria
1)
2)
Effluent guidelines
Customer Satisfaction
1)
2)
3)
4)
Fecal Coliform Count
Sewer bypass (#)
Sewer overflows (#)
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1)
2)
3)
4)
Adequate Flow
Emergency Overflow
Adequate Capacity
Customer Satisfaction
1)
2)
3)
4)
5)
Flow velocity (min/max)
Average daily flow
Pumps and storage capacity
Wastewater produced/capita
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1)
Minimize # and Duration of
Interruptions
Minimize Response Time
Maximize Efficiency
1)
2)
3)
4)
Blockages and backups (#)
Collapses (#)
I & I (% or amount)
Sewage flooding incidents due
to capacity and blockages (#)
Service interruptions (#)
Pollution incidents (#, Severity)
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System Integrity
2)
3)
5)
6)
7)
CPI Performance Assessment
Performance Indicators – Water & Wastewater Systems
Water
1)
2)
Managing breaks for small diameter
distribution systems
Transmission Trunks (Large Diameter) use
Structural distress indicators (NRCAwwaRF)
Sanitary and Storm Water
1)
2)
3)
4)
WRc Condition Grade (1-5 Defect-based)
– Structural (Physical Condition)
– Operational (Blockages and
Infiltration)
NRC Trunk Sewers Guidelines (Defects)
National Association of Sewer Service
Contractors - NASSCO (Simplified WRc)
North American Association of Pipeline
Inspectors – NAAPI (Simplified WRc)
CPI Performance Assessment
Deterioration Prediction Models
• State-of-art deterioration prediction models are based on Markov
chain models :
– qualitative prediction of future performance based on ratings
– modeling of cumulative damage only – No “shock” modeling
– assumption of constant rate of deterioration - Not realistic at all !
– no information on residual capacity and safety
– predicted service life is a rough approximation
– ‘true” condition can be seriously overestimated – disaster!
– examples of decision support systems: “Pontis”, “Bridgit”, etc.
CPI Performance Assessment
Reliability of Performance IndicatorsExamples
• Same bridges rated by different inspectors :
– up to 5 rating points difference! (FHWA 2000)
– unacceptable for such critical structures!
– predicted remaining life is arbitrary and may lead to unsafe
estimates- disasters (loss of life, injuries, economic impacts, etc.)
• Same bridge can be rated by 3 different inspectors as either:
– Serious condition – Probability of collapse could be 0.01
– Fair condition - Probability of collapse could be 0.05
– Critical condition - Probability of collapse could be 0.1
Unacceptable for safety-critical systems
CPI Performance Assessment
Reliability of Performance Indicators- Examples
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Condition Rating
I35 bridge superstructure:
– bridge opened to traffic in 1967
4
– rated “Poor” not “Critical”
3
– scheduled for reconstruction in 2020-25
2
– estimated Remaining Life 12-15 years
–bridge collapsed 2 years after evaluation !
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Probability of failure
Poor
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Serious
?
Critical
?
Imminent failure
Failed
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1 ?
CPI Performance Assessment
Summary
• Current performance assessment is mainly qualitative
• Focus on material distresses instead of system distresses
• Based on “visual” inspection + some non-destructive techniques
– mapping observed material distresses to subjective rating scales
• Arbitrary definition of minimum performance or failure criteria
• No differentiation between safety-critical and secondary systems
• Limited or no quantitative data on:
– residual capacity, safety
– probability of failure and risk of failure
– remaining life
“Knowledge Deficit” in CPI
Performance Assessment
Cumulative damage
“wear & tear”
Random shock- induced damage
Repair/Rehab/Replace
Limit state/
acceptable
minimum
performance
Service life 1
Service life 2
Service life 3
Life cycle
Time (years)
Residual life
“Knowledge Deficit” in CPI
Performance Assessment
Quantitative Measures of CPI Performance - Examples
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Performance= Capacity – Load
Performance= Capacity / Load
Performance= Probability that Capacity is higher than Load
Time-varying probability of failure
Time-decreasing capacity
Capacity
Initial capacity
Load
Load
Time
“Knowledge Deficit” in CPI
Performance Assessment
Acceptable Minimum Levels of Performance
• Develop rational and objective acceptable minimum levels of
performance or limit states considering:
– type of CPI system and component
– consequences of failure/ importance/ criticality of CPI system: e.g.
loss of life, health/ injury risks, property loss, environmental impact
– type of failure mode: ductile / progressive or brittle / sudden
– design life of CPI system/ component
“Knowledge Deficit” in CPI
Performance Assessment
Quantifying Risk of Failure of CPI
• Develop approaches to assess risk of failure of CPI systems:
Risk of failure = Probability of Failure X Consequences of failure
• Risk of failure enables decision makers to :
– identify critical / high priority components of CPI
– Integrate management of different CPI systems
CPI Project
Management
CPI Network
Management
Integrated CPI
Management
Approach
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Build on existing knowledge and best practices
Advance state of knowledge using sound scientific and
engineering approaches and develop:
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reliable and practical performance assessment of CPI systems
objective minimum performance levels
“unified” or “model” CPI performance indicators and measures
Promote adoption and implementation of developed
approaches for CPI performance assessment and
management
Approach
• NRC and NRTSI will collaborate on research projects:
– Phase 1: Development of a framework for assessment of state,
performance and management of CPI
– Phase 2: Development of approaches and tools for performance
assessment and management of CPI
• Benefits
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ensure safety and health of Canadians
improve the performance of Canada’s CPI
support decision making at all levels of government
reduce economic, environmental, and social impacts of CPI
evaluate impact of funding on performance of CPI
Questions?
Zoubir Lounis, Ph.D., P. Eng.
[email protected]
Tel: (613) 993-5412