Structural Vulnerability, Risk Assessment and Land Use Issues for Transportation Infrastructure May 18, 2005 Shay K. Burrows, P.E. Senior Structural Engineer

Outline Identify threats to bridges and tunnels Describe the effective defense strategy How land use plays a major part in supporting the defense April 28, 2015

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

Are Bridges and Tunnels Really Targets? Encyclopedia of Afghan Resistance “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.” Pressure point #2 Pressure point #1 Pressure point #3

Terrorist Tactics Possible 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 Source: FM5-250 and ConWep 5' 2.5' Center of mass: x lb Contact, elevated, un-tamped: 34x lb 6' Standoff of 6': 267x lb Required C-4 Charge Size for Breaching of Concrete

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

What We’re Trying to Prevent

Contact Information Shay K. Burrows, P.E. FHWA- Resource Center 10. S. Howard Street Suite 4000 Baltimore, MD (410)