This project involved vessel collision risk assessments of bridges owned by the Louisiana Department of Transportation and Development, including seven steel cantilever thru-truss structures crossing the Mississippi River and one girder structure over the Inner Harbor Navigational Canal. The following bridges were included in the study:

• Baton Rouge Interstate 10 Bridge, Baton Rouge, Louisiana
• Crescent City Connection Bridge No. 1, New Orleans, Louisiana
• Crescent City Connection Bridge No. 2, New Orleans, Louisiana
• Gramercy Bridge, Gramercy, Louisiana • Huey P. Long Bridge, New Orleans, Louisiana
• Sunshine Bridge, Donaldsonville, Louisiana • Vicksburg Bridge, Vicksburg, Mississippi
• Inner Harbor Navigation Canal Bridge, New Orleans, Louisiana

Modjeski and Masters, Inc. conducted an evaluation of the vulnerability of the bridges to vessel collision, and made recommendations to reduce the risk and consequences of vessel collisions. Several factors affecting the risk and consequences of vessel collisions were investigated including bridge characteristics, waterway characteristics, history of vessel collisions with the bridge and analysis of the accidents, vessel traffic characteristics and navigation conditions, and marine terminals, wharves, and docks near the bridge and their impact on navigation. The risk analysis that considers all of these factors has been performed in accordance with Method II of the “AASHTO Guide Specification and Commentary for Vessel Collision Design of Highway Bridges.”

To evaluate the vulnerability of the superstructure, a procedure consistent with the substructure risk analysis was developed. Probability distributions for the vessel size, draft and height, and for river stage were determined so that a more detailed probability based risk assessment could be made. In addition, an investigation of the effects of ship size, speed and loading condition, and water level on the governing failure modes has been conducted not only for assessing the risk and consequences of vessel collision, but also for developing an effective pier protection or strengthening scheme, if required.