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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

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state wide vulnerability assessment of bridges

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

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
Scope of Project
extreme events for bridges

Multi-hazard Extreme Events

Extreme Events

  • Seismic
  • Vessel Collision
  • Wind (Long Span Bridges)
  • Hydrocarbon Fire
  • Terrorist Attack (Man-Made)
  • Vehicular Impact
  • Scour and Flooding
Extreme Events for Bridges
example progressive collapse bridges

Bridges – Progressive / Disproportionate Collapse History

I 90 Bridge at Schoharie

Creek (1987)

(Scour)

Silver Bridge (1967)

(fracture)

Mianus River (1983)

(fracture)

Example:Progressive Collapse Bridges

SFOBB –East Bay

Spans (1989)

(Seismic)

Queen Isabella

Causeway (2001)

(barge collision)

I 35 Minneapolis (2007)

(fracture)

example progressive collapse bridges5

Rail Bridge Collapse – Flooding/Scour

Example:Progressive Collapse Bridges
  • Amtrak Bridge Collapse Mobile Alabama September 22, 1993
  • 1993 Great Midwest Floods washed away several railway bridges
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)
Previous Screening and Ranking Criteria
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
New Screening Criteria
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)
Modified Screening Method
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

Multi-modal Aspects
modified screening method11
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
Modified Screening Method
modified screening method12
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
modified screening method13
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
modified screening method14
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
top 50 with rail bridges

Freight Rail Bridge Data

Freight Rail Bridge Data

Top 50 with Rail Bridges
  • 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
top 50 with rail bridges16

Key Freight Rail Bridges

Freight Rail Bridge Data

Top 50 with 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)

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
Threat and Vulnerability Assessment
threat and vulnerability assessment20

Top 50 Bridges Sorted by Type and Feature Crossed

  • Bridge Structure Types IdentifiedNo.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 5
    • Longest main span over water (150 ft. span)
    • Longest main span over land (161 ft. span)
  • (09) Truss – Deck 2
    • Longest main span over water (550 ft. span)
  • (11) Arch – Deck 1
    • Longest main span over water (96 ft. span)
  • (15) Movable – Lift 3
    • Longest main span over water (333 ft. span)
  • (16) Movable – Bascule 2
    • Longest main span over water (185 ft. span)
Threat and Vulnerability Assessment
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
Results