Direct Integration Algorithms for Efficient Nonlinear Seismic Response of Reinforced Concrete Highway Bridges

Abstract

Reinforced concrete (RC) highway bridges are essential lifeline structures, especially in California, which has numerous active faults at which earthquakes are common occurrences. Accurate seismic structural analysis is important to ensure their safety. The most suitable analytical simulation method for this purpose is nonlinear time-history analysis (NTHA). However, one of the main challenges for NTHA is related to the convergence of the numerical solution, which usually arises at high levels of nonlinearity. Inherent lack of high degrees of redundancy of the bridge systems and the need for their continuous functioning in the aftermath of an earthquake require accurate modeling and robust numerical solutions for the response investigation of these important structures. This paper presents solutions to the problems of convergence encountered in NTHA of RC highway bridges during the use of direct integration algorithms. The considered numerical integration algorithms include two that are explicit, namely, the Newmark and operator-splitting algorithms, and one that is implicit, namely, the TRBDF2 algorithm. Applicability of these integration algorithms, instead of the commonly used implicit Newmark, is explored for three representative RC highway bridges in California. Furthermore, the suitability of an adaptive switching among these integration algorithms during the NTHA is investigated. Finally, the efficacy of the solutions is demonstrated for a challenging performance-based earthquake engineering-related subject that involves a large number of NTHAs to identify the predominantly first-mode engineering demand parameters.