Optimal safety valuation of high-speed railway bridges based on reliability assessment and life-cycle cost concept

Abstract

This study was intended to evaluate the dynamic performance high-speed railway bridges (HSR bridges) of composite box girder type so as to propose the rational safety level and optimal design method using reliability assessment (RA) and expected life-cycle cost (LCC) concpet. To that end, a various design alternatives were created considering the variation of member section based on a standard design section (current Korean code) of HSR bridges and then the static analysis, natural frequency analysis and time history analysis using time series of traffic load were implemented on each design alternative. Based on finite element analysis (FEA) results, the dynamic amplification factor (DAF) of the standard design section was evaluated in a way of comparing with related alternatives. RA depending on design strength limit state function was carried out considering the effect of external uncertainty contained in FEA results by each design alternative. Furthermore, the expected LCC of HSR bridges was evaluated using RA results and the optimal design method was determined through the calculated minimum LCC. To review the effect of internal uncertainty included in the safety index, failure probability and minimum LCC of selected optimal design method, sensitivity assessment was implemented and, consequently, a frequency-histogram (cumulative-percentage) was illustrated. The outcomes of research, along with the dynamic performance assessment of HSR bridges, will be expected to provide the basic information in determining the structural safety and optimal design method.