A Study of U.S. Bridge Failures (1980-2012)

Keywords: earthquakes, bridges, Load and Resistance Factor Design (LRFD) factors, extreme hazard, multi-hazard, resilience

Abstract:
Designing bridges to resist extreme hazard load effects has always been a safety concern of AASHTO and the bridge engineering community. This concern has been elevated in recent years because of the perceived increased frequency and intensity of extreme hazards that affect bridges.  Some of these hazards have resulted in significant losses; for example, the 2005 Hurricane Katrina had damage exceeding $125 billion in addition to the loss of 1,833 lives. When a bridge failure occurs, the loss of the bridge structure is only one component of the total loss; its loss can result in much greater national economic consequences than the value of the asset itself. This has highlighted the need to intensify the exploration of design principles and methodologies for the optimal design of multiple hazard (MH) resilient bridges.  A research project at the Multidisciplinary Center for Earthquake Engineering Research (MCEER), supported by FHWA since 2008, has been dedicated for this purpose.  To pursue this task, it is essential to first establish reasonable bridge damage/failure models. Furthermore, most of the issues in developing or improving current bridge design specifications can be either addressed or improved by the collection and deep understanding of sufficient bridge damage information. Therefore, the initial task is to gather quantitative information of the hazard events and their damage effects on bridges through available bridge failure documentation. This report describes the information collected by the authors, with emphasis given to the data sources and an explanation on how the collected information is documented.  The objective of this report is to establish data sources for developing load distribution models and bridge damage models for reliability-based formulation of design limit states. For example, the results of statistical analyses can be used to calibrate and determine a reasonable probability of failure for bridge design under current Load and Resistance Factor Design (LRFD) framework. Data collected so far, however, are insufficient for accomplishing the intended objectives, due to the lack of specific information on the hazards, bridge design and resulting economic losses in quantitative terms. Gathering such data will require engineering forensic studies on previously damaged bridges. A national or international workshop should be organized to establish standard measures for different hazards, and their impact on bridge damage/failures. These standardized measures should be used to enter data into the database for future events as well as for the results of forensic studies of past failures, one bridge at a time. To re-examine past bridge failures is a tedious and challenging task, but its long-term pay-off can be significant from the viewpoints of bridge safety and reduced economic losses.