Probabilistic Risk of Temporary Bridges in California High Seismic Zones

This study investigates the probabilistic risk of temporary bridges with a lightweight steel superstructure in the highly seismic zones of San Francisco and Los Angeles, CA. The primary objective is to offer insights into the performance of temporary bridges designed for a return period of 100 years (5% probability of occurrence in 5 years) to inform current design provisions. Detailed numerical models are developed using OpenSees to assess the bridges’ response under three hazard levels, namely 1.0%, 2.5%, and 5.0% probability of occurrence within their expected 5-year lifespan. Additionally, another set of models is created to meet the minimum design requirements mandated by AASHTO for ordinary bridges. Fragility functions are then developed to assess the probability of exceeding each damage state across all hazard levels and bridge designs. Using the probabilistic damage control application, the total risk of exceeding the target performance levels of repairable damage is calculated. Results indicate that bridges designed following hazard-consistent design approaches and not meeting the minimum requirements for ordinary bridges exhibit satisfactory performance.