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May 18, 2005. Structural Vulnerability, Risk Assessment and Land Use Issues for Transportation Infrastructure. Shay K. Burrows, P.E. Senior Structural Engineer. July 13, 2014. Outline. Identify threats to bridges and tunnels Describe the effective defense strategy
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May 18, 2005 Structural Vulnerability, Risk Assessment and Land Use Issues for Transportation Infrastructure Shay K. Burrows, P.E. Senior Structural Engineer
July 13, 2014 Outline • Identify threats to bridges and tunnels • Describe the effective defense strategy • How land use plays a major part in supporting the defense
Are Bridges and Tunnels Really Targets? • Bridges and tunnels are attractive terrorist targets due to: • Economic importance to traffic and commerce • Symbolism (I.e. Golden Gate Bridge, Lincoln Tunnel, etc.) • Cost and time for replacement • Public impact from an attack • Relatively high vulnerability, both susceptibly and structurally Source: Transportation Security Administration
Encyclopedia of Afghan Resistance Are Bridges and Tunnels Really Targets? Pressure point #1 Pressure point #2 Pressure point #3 “When you destroy large bridges by explosives, loading the middle part will destroy the netted area (the roadway), the explosives should be combined with others placed at the two pressure points. This will destroy the bridge.”
Terrorist TacticsPossible Course of Action – Decision Criteria • High probability of success • Impact – maximize damage and casualties • Realistic Logistics – easily obtained materials • Speed – minimize placement and priming time • Secrecy and surprise • Simplicity and easy coordination • Flexibility
Terrorists Threats to Bridges • Mechanical cutting devices • Chemicals (acids, corrosives, etc.) • Thermite • Torches • Area denial • Chemical/ biological • Small bombs, or just the threat of one
Terrorist Threats to Bridges Explosion! Bombs constitute a high percentage of terrorist attacks worldwide
Explosive Effectiveness • Depends on: • Type • Amount (the more the better!) • Location • Internally placed • External contact • Standoff Decreasing effectiveness Decreasing time on target
Explosive Location 5' Required C-4 Charge Size for Breaching of Concrete 6' 2.5' Standoff of 6': 267x lb Center of mass: x lb Contact, elevated, un-tamped: 34x lb Source: FM5-250 and ConWep
Vehicle Bombs • Historically, the terrorist weapon of choice • Can use more explosives • Doesn’t require any time on target
Mitigation – In General • The goal is to implement measures which are appropriate and effective for a particular risk, yet economical and do not interfere with a bridge’s operation
Construct an Effective Defense • Response and Recovery • Prepare to deal with multiple, cascading events • Deterrence • Make them know you are watching • Denial • Physically limit access • Detection • Use security, sensors, surveillance • Defense • Apply permanent standoff, structural hardening
Defense Priority • First Priority • Develop an accelerated response and recovery plan • Second Priority • Deter, deny, detect • Third Priority • Defend with standoff • Fourth Priority • Defend with structural toughening How effective land use can help: - Denying access - Providing standoff
Deny Access – Fencing and Area Control • Fencing or bollards to deny vehicle access or parking
Provide Standoff on Land • Permanent barriers may provide sufficient standoff, including bollards • Temporary barriers can be used to close roads/lanes or provide standoff around critical elements during a heightened alert or specific threat • Any barrier is better than none, since standoff is more important
Contact Information • Shay K. Burrows, P.E. • FHWA- Resource Center • 10. S. Howard Street • Suite 4000 • Baltimore, MD 21201 • (410) 962-6791 • email@example.com