Simplified Uniform Hazard Liquefaction Analysis for Bridges

Abstract

Many bridge designers currently rely on the design specifications provided by AASHTO to evaluate liquefaction hazards for foundations and embankments. These guide specifications recommend a pseudo-probabilistic approach (i.e., an approach in which probabilistic estimates of seismic loading are incorporated into a deterministic liquefaction hazard analysis) for most conventional projects. A more consistent approach for the assessment of liquefaction hazards would involve a performance-based or uniform hazard evaluation of liquefaction potential. However, a performance-based liquefaction analysis is complex and difficult to implement in practice. This paper describes a simplified procedure for uniform hazard liquefaction analysis that uses the standard penetration test to closely approximate the results of a performance-based liquefaction analysis at a desired uniform hazard level. The simplified procedure is compatible with current AASHTO load and resistance factor bridge design specifications and is intended for use on bridges and other transportation-related structures. The procedure is summarized and shown to produce more consistent results for liquefaction hazards across different seismic environments than the existing AASHTO pseudo-probabilistic procedure. An example application of the simplified procedure is presented and discussed, and limitations for the procedure's proper use are provided.