Safety Assessment of Continuous Beam Bridges under Overloaded Customized Transport Vehicle Load

Abstract

This paper presents the safety assessment of prestressed concrete box-beam (PCB) bridges under customized transport vehicle (CTV) load. First, the recorded data of 81,616 CTVs were used in the investigation of load characteristics, in which five typical CTV types were extracted and the corresponding critical CTVs were determined. Second, the effects of PCB bridges under critical CTV loads were compared with the design load effect of AASHTO and the Ministry of Communications and Transportation (MOCAT). Third, the safety assessment of PCB bridges under critical CTV loads was accomplished with the presented reliability-based load rating method, in which the partial factor of CTV load effect is optimized by considering the benefit and failure cost upon the passing of CTVs. Adopting different partial factors for the CTV load effect according to the gross vehicle weight is proposed. The multilevel ratio of indirect cost to direct cost was adopted to investigate its influences on target reliability index, partial factor, and assessment results. The analysis results show that the ratio of indirect cost to direct cost has a greater influence on target reliability index rather than the partial factor of CTV load effect and the assessment results. For the PCB bridges under CTV load, the negative bending moment may control the structure safety instead of the positive bending moment in some load cases. The proposed analysis framework and the results can be used in the safety assessment of other bridge types under CTV load and traffic permitting.