Reliability-Based Calibration of Load and Resistance Factors for Design of RC Bridges under Multiple Extreme Events: Scour and Earthquake

Abstract

A multihazard reliability-based framework is developed through this study to evaluate the structural response of RC bridges under the combined effects of pier scour and earthquake events. This framework is used to calibrate the scour load-modification factors for the design of bridges located in high seismic areas. Toward this goal, a series of case study bridges are investigated. For each bridge case, the joint probability of failure owing to scour and earthquake hazards is determined for a range of expected combinations of these two extreme events. The occurrence probability of each scour-earthquake scenario is identified by taking into account all of the major sources of load uncertainty through scour risk and seismic hazard curves. Furthermore, the uncertainties inherent in the structural response of bridges are included in the framework to improve the accuracy of estimated failure probabilities. The calculated probabilities are then compared with the maximum acceptable probability of failure (or its equivalent target reliability index) given by current design codes to obtain scour load-modification factors. The developed framework provides a reliable approach for the calibration of code specifications in the extreme event situations and can be extended to other combinations of natural hazards.