state-wide vulnerability assessment of bridges
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State-Wide Vulnerability Assessment of Bridges. Talking Freight Seminar Series Security and System Resiliency November 18, 2009 1:00 – 2:30 PM By J. Englot, PE HNTB Corporation. Review how the state’s bridge inventory list (6,600+ bridges) was previously reduced and prioritized - PowerPoint PPT PresentationTRANSCRIPT
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State-Wide Vulnerability Assessment State-Wide Vulnerability Assessment of Bridgesof Bridges
Talking Freight Seminar SeriesSecurity and System Resiliency
November 18, 2009
1:00 – 2:30 PM
By J. Englot, PE
HNTB Corporation
State-Wide Vulnerability
Assessment of Bridges
Scope of Project
• Review how the state’s bridge inventory list (6,600+ bridges) was previously reduced and prioritized
• Update the ranking methodology to create a “Top 50” list of bridge and tunnel assets for the state
• Include critical rail (passenger & freight) and highway bridges and tunnels
• Include any other adjacent critical or hazardous infrastructure in the assessment
• Conduct assessment of threats/hazards, vulnerability, impact and countermeasure needs for top 50 assets
• Submit findings in a report for general countermeasures for all highways, bridges, and tunnels
State-Wide Vulnerability
Assessment of Bridges
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Extreme Events for
Bridges
Extreme Events
• Seismic
• Vessel Collision
• Wind (Long Span Bridges)
• Hydrocarbon Fire
• Terrorist Attack (Man-Made)
• Vehicular Impact
• Scour and Flooding
Multi-hazard Extreme Events
State-Wide Vulnerability
Assessment of Bridges
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Bridges – Progressive / Disproportionate Collapse History
Silver Bridge (1967)(fracture)
Mianus River (1983)(fracture)
SFOBB –East Bay Spans (1989)
(Seismic)
Queen IsabellaCauseway (2001)(barge collision)
Example:Progressive
Collapse Bridges
I 90 Bridge at SchoharieCreek (1987)
(Scour)
I 35 Minneapolis (2007)(fracture)
State-Wide Vulnerability
Assessment of Bridges
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Rail Bridge Collapse – Flooding/Scour
•Amtrak Bridge Collapse Mobile Alabama September 22, 1993
•1993 Great Midwest Floods washed away several railway bridges
Example:Progressive
Collapse Bridges
State-Wide Vulnerability
Assessment of Bridges
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Previous Screening
and Ranking Criteria
Limited Criteria to a Transportation Focus in the Screening Phase
• Ability to Provide Protection• Relative Vulnerability to Attack• Casualty Risk (ADT & Bridge
Length)• Environmental Impact (utilities)• Replacement Cost Replacement Down Time Emergency Response Function• Government Continuity• Military Importance Available Alternate (detour
length)• Communication Dependency
(utilities) Economic Impact (ADT) Functional Importance (ADT)• Symbolic Importance (Historical)
State-Wide Vulnerability
Assessment of Bridges
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New Screening
Criteria
Development of New Screening Criteria• Goal is to independently develop criteria using
latest DHS guidance (NIPP) and compare to previous results
• Bridge criticality should be related to the state’s mission and the DHS mission for transportation sector
• Align with DHS goal of “Resiliency of Critical Transportation Infrastructure”
• Include priority for emergency evacuation routes
• Develop a metric to fairly compare criticality of highway and rail passenger/freight bridges and tunnels
• Relate criticality to economic impact on region
State-Wide Vulnerability
Assessment of Bridges
Modified Screening
Method
Summary - Screening to determine “Top 50” facilities
• Criteria– Hazard independent
– Casualties not included
• Assumptions– Complete Collapse of Span
– Based on volume of goods and people transported
• Based on Structural Inventory and Appraisal (SI&A) data– Rank all 6,000+ facilities
• Formula based on:– Max. Span Length
– No. Spans
– No. Lanes
– County
– Detour Length
– Average Daily Traffic (ADT)
– Average Daily Truck Traffic (ADTT)
State-Wide Vulnerability
Assessment of Bridges
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Multi-modal
Aspects
Multi-modal Aspects• Develop a unit for measuring movement
(throughput) of people and goods independent of mode (highway or rail)
• Utilize the wealth of technical references and traffic studies on the economic impact of traffic delays to the regional economy
• Perform a reality check on the results:
Verify that people have redundant multi-mode travel paths
Verify that freight has redundant multi-mode travel paths
State-Wide Vulnerability
Assessment of Bridges
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Multi-modal
Aspects
Equivalent Units of Transport
State-Wide Vulnerability
Assessment of Bridges
Modified Screening
Method
Transport unit:– 1 automobile (1.2 avg. pass.) = 1 Transport Unit
– 1 truck = 2 Transport Units
– 1 railroad passenger = 0.83 Transport Units
– 1 rail hopper car = 4 trucks = 8 Transport Units
– 1 cargo container = 1 truck = 2 Transport Units
State-Wide Vulnerability
Assessment of Bridges
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Screening Formula
PDTU = [TVTU × DD × TDD] × ER
Where:
PDTU = Potential delay of transport units (in unit-hours).
TVTU = Total volume of transport units (in units/day).
DD = Days of downtime when bridge or tunnel is not functional (in days).
TDD = Time delay due to detour (in hours)
ER = Importance factor for bridges that are designated evacuation routes. This is a multiplier (e.g., 1.2) to increase the importance of those facilities that are intended for use during emergencies.
Modified Screening
Method
State-Wide Vulnerability
Assessment of Bridges
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Screening Formula
Recovery time of bridge based upon maximum span length:
DD = Max Span Length Factor
Max Span Length Factor (measured in months)
DD(months) = 7.0E-6(Lmax)2 + 0.0168(Lmax)
Based on construction time of recent bridges, best fit
Oakland MacArthur Maze < 100 feet 1 month
Interpolate between 100-500 feet 6 months (315 ft.)
Interpolate between 500-1,500 feet 24 months (1,000 ft.)
Tacoma Narrows Bridge > 1,500 feet 42 months
Modified Screening
Method
State-Wide Vulnerability
Assessment of Bridges
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Rail Information
NJ Transit, Amtrak, and CSX, Norfork Southern, and the Short lines
• Owner
• Line
• Structure Number or ID
• Name of Structure
• County
• Township
• Overall length of structure
• Maximum Span
• Number of Tracks on structure
• Avg. daily number of passengers carried
• Avg. daily number of freight cars
Note: Limit data to most heavily traveled lines.
Modified Screening
Method
State-Wide Vulnerability
Assessment of Bridges
Top 50 with Rail Bridges
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Freight Rail Bridge DataFreight Rail Bridge Data
Sources of Information for Freight Rail Volumes
•FRA data is most reliable if available•Rail freight studies published by State DOT, regional Authorities, and MPOs•State-wide freight study showing freight rail density
State-Wide Vulnerability
Assessment of Bridges
Top 50 with Rail Bridges
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Freight Rail Bridge DataKey Freight Rail Bridges
Multi-Arch Bridge (Freight & Passenger) Multi-Truss Bridge (Freight)
Key Freight Rail Bridges
•15-25 avg. daily trains•Average train length 61 rail cars•Have long detours (10 – 55 miles)•Have long spans (90 - 330 feet)•Passenger trains increase criticality
Swing Bridge (Freight & Passenger)
State-Wide Vulnerability
Assessment of Bridges
Top 50 with Rail Bridges
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Top 50 Results of Screening of Bridges and Tunnels for All Public Agencies
Bridge Characteristics Percent Number
State-Owned Bridges 24% 12 / 50
Evacuation Routes 70% 35 / 50
ADTT exceeding 10,000 34% 17 / 50
ADT exceeding 100,000 (w/o trucks)
38% 19 / 50
12 or more months of recovery time
24% 12 / 50
Passenger Rail Tunnels 10% 5 / 50
Passenger Rail Bridges 8% 4 / 50
Rank of Top 3 Freight Rail Bridges
52, 110, 145 (In top 2 percentile of all 6,600 bridges in state)
State-Wide Vulnerability
Assessment of Bridges
Top 50 with Rail Bridges
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Top 50 Results of Screening of State-Owned Bridges
Bridge Characteristics Percent Number
Moved into Top 50 w New Screening Methodology
44% 22 / 50
Evacuation Routes 70% 35 / 50
No detour available 8% 4 / 50
ADTT exceeding 10,000 36% 18 / 50
ADT exceeding 100,000 (w/o trucks)
44% 22 / 50
3 or more months of recovery time
26% 13 / 50
State-Wide Vulnerability
Assessment of Bridges
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Threat and Vulnerability Assessment
Steps For Detailed Vulnerability Assessment and Extrapolation
• Complete Threat Analysis
• Complete 7 representative TVA Risk Assessments
• Identify and estimate preliminary mitigations
• Extrapolate TVA and mitigations from 7 representative bridges to all 50 state owned bridges
• Summarize findings in a report for general countermeasures for top 50 critical bridges and tunnels
State-Wide Vulnerability
Assessment of Bridges
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Top 50 Bridges Sorted by Type and Feature CrossedBridge Structure Types Identified No. Longest Span in Group(02) Stringer/Multi-beam or Girder 37
Longest main span over water (252 ft. span)Longest main span over land (230 ft. span)
(03) Girder and Floorbeam System 5Longest main span over water (150 ft. span)Longest main span over land (161 ft. span)
(09) Truss – Deck 2Longest main span over water (550 ft. span)
(11) Arch – Deck 1Longest main span over water (96 ft. span)
(15) Movable – Lift 3Longest main span over water (333 ft. span)
(16) Movable – Bascule 2Longest main span over water (185 ft. span)
Threat and Vulnerability Assessment
State-Wide Vulnerability
Assessment of Bridges
Typical Mitigations to Reduce Multi-hazard Risk
Typical Mitigations
State-Wide Vulnerability
Assessment of Bridges
Mitigation Effectiveness
Compiled Mitigation Evaluation
0.01
0.10
1.00
10 100 1,000 10,000 100,000
Cost (thousands of $)
Ris
k R
ed
uc
tio
n
Higher Benefit/Lower Cost
Higher Benefit/Higher Cost
Lower Benefit/Lower Cost
Lower Benefit/Higher Cost
State-Wide Vulnerability
Assessment of Bridges
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Results
Results of State-Wide Assessment
• Criticality of Every Highway and Rail Bridges as part of the State Transportation System is Known
• Use as Tool for Prioritizing Investing of Funds for Security, State-of-Good-Repair, and Rehabilitation
• “Risk Based” Assessment for DHS/TSA Federal Funding Purposes
• Use as Tool for Planning New Crossings to Increase Transportation Network Resiliency
• Use to Perform Detailed Vulnerability Assessment of Grouped Assets
• Use to Develop Security/Hazard Mitigation Budget and the Order of Priority for Spending Funds