Sessions & Events

Vessel Collision Effects on Bridges

Tuesday, October 28, 2025  8:30 AM - 10:30 AM, H - Holiday 3

Vessel collision is an important consideration in the design of bridges over navigational waters. This topic became particularly visible after the recent fatal accident in Baltimore. There is a need to revisit the vulnerability of bridges with regard to vessel collision. The proposed session will include presentations on statistics of accidents involving vessels (ships and drifting barges), sensitivity of structural components of bridges, in particular piers and abutments. Special consideration is required by a simultaneous occurrence of a combination of scour and collision. An extreme scour and extreme vessel collision is unlikely. Therefore, there is a need to collect the available information about occurrences of load combinations, in region and elsewhere to determine the type of vessel, weather conditions, water level (flood?) and other factors. The collision forces depend on the vessel (ship under power, drifting ship or barge).

Learning Objectives:
Learning Objectives:
(1) Explain the principles and procedures for designing bridges to withstand vessel impacts;
(2) Apply statistical analysis methods to support vessel impact design decisions;
(3) Identify potential updates or revisions needed in the AASHTO LRFD vessel collision design provisions;
(4) Evaluate available data and resources to determine appropriate vessel collision loads and associated risks.

This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.

Ship & Barge Collision with Bridges – Overview of AASHTO Vessel Collision Criteria and Lessons Learned Since Its Original Adoption in 1991

Presented By: Michael Knott
Affiliation: Moffatt & NIchol Engineers
Description: The collapse of the Francis Scott Key Bridge on March 26, 2024, Baltimore has increased industry and public awareness of the potential for vessel collision in busy coastal and inland waterways. The presentation will include background on the development of the AASHTO vessel collision design provisions and examples of historic bridge collapses due to ship and barge impacts. A brief overview of the AASHTO risk analysis procedures will be provided and how the basic analysis principles in the Bridge Design Code can be modified to incorporate complex channel geometries and modern navigation systems (regulatory requirements and electronic navigation devices). An overview of alternative pier protection systems will be provided (physical structures and potential vessel operation procedures). The summary will include major lessons learned using the Bridge Code and observations

Risk Analysis for Vessel Collision with Bridges

Presented By: Andrzej Nowak
Affiliation: Auburn University
Description: The design and evaluation of bridges that are exposed to navigational waters requires consideration of vessel collision events. The objective of this paper is to present a calibration procedure for the limit state functions with vessel collision. The procedure includes selection of representative bridges over navigational channels, formulation of the limit state functions, development of load and resistance parameters, selection of the reliability analysis procedure, calculation of the reliability for representative bridges, selection of the target reliability index, and then calculation of the load and resistance factors. The latter depends on the consequences of failure and cost analysis. The review of the available failure records shows that the most frequent incidents have insignificant impact on bridges, such as a barge drifting out of control. However, a ship under power can cause a total collapse as was the case with Francis Scott Key Bridge. The paper will present reliability indices will be calculated for limit state functions with vessel collision for representative bridges, assuming they are designed using the current code provisions. The target reliability indices will be suggested depending on site conditions (channel, vessel and bridge).

A Framework for Assessing the Collapse Risk of Harbour Bridges Due to Ship Collision

Presented By: Fadi Oudah
Affiliation: Dalhousie University
Description: The collapse of the Francis Scott Key Bridge in Baltimore has underscored the need for a structured and practical approach to assessing the risk of harbour bridge collapse due to ship collisions. Many older long-span steel truss bridges, not originally designed for vessel impacts, are particularly vulnerable. This presentation focuses on the key elements that a risk assessment framework should include to evaluate the likelihood of structural collapse if a bridge is struck by a design ship impact. The framework emphasizes the interaction between the superstructure and substructure, ensuring both local and global structural responses are adequately considered. It incorporates stochastic nonlinear finite element simulation to account for uncertainties in bridge response and existing conditions, combined with reliability-based methods to provide a systematic approach to quantifying and interpreting collapse risk. The framework is designed to be practical and adaptable to project-specific constraints, ensuring that the assessment process yields cost-effective solutions if the risk of collapse is found to be unacceptable.

Vessel Collision Consideration in Bridge Design

Presented By: Emily Ullmer
Affiliation:
Description: Past and recent vessel collisions with bridges over navigable waterways have increased appreciation and concern about the safety of bridges crossing navigation channels in the United States. In 1991, the American Association of State Highway and Transportation Officials (AASHTO) adopted the Guide Specification and Commentary for Vessel Collision Design of Highway Bridges. The 1991 AASHTO Guide Specification served as a benchmark document for the design of new and evaluation of existing bridges that cross navigable waterways. At the time of the writing of the 2009 2nd Edition of the Guide Specification, there had been 17 major bridge collapses due to ship or barge collision in the United States (Guide Specification, 2009). Portions of the 2009 Guide Specification were subsequently adopted into the AASHTO LRFD Bridge Design Specifications, thereby requiring all new bridges crossing navigable waterways to meet the design requirements outlined in AASHTO LRFD. AASHTO LRFD requires the use of a statistical approach to vessel collision risk analysis. This approach considers several factors including the type, size, and frequency of vessels transiting the waterway to evaluate the exposure to risk of vessel collisions, and potential impact forces imparted on a bridge in the event of a vessel collision. The AASHTO probabilistic analysis procedures provide a means to evaluate risk in a systematic manner. The presentation will overview the importance of performing a vessel collision risk assessment, summarize the information needed for a risk assessment, and outline general procedures for consideration of vessel impact forces in bridge design.

Ship Impacts on Bridges: AASHTO Code and Research

Presented By: Thomas Murphy
Affiliation: Modjeski and Masters, Inc.
Description: This presentation touches on the history of vessel collision code development in the United States and highlights methodologies used in the current edition of AASHTO LRFD Bridge Design Specifications. It also describes the different factors that influence risk due to vessel collision and offers suggestions for future research.