Behavior of prestressed concrete box bridge girders under hydrocarbon fire condition

Currently, prestressed concrete (PC) bridges are often suffered from fire caused by oil tanker. However, there is very little research information and test data in the literature on the fire resistance of PC bridge girders. This paper presents an investigation into behavior of PC box bridge girder under hydrocarbon fire condition. A numerical model, in the form of the computer program ANSYS, for predicting the influence of a significantly critical factor, namely, prestress degree, on the performance of prestressed concrete bridge with box girder subjected to hydrocarbon fire is presented. The three stages associated with the numerical procedure, for evaluating fire resistance of PC box girders, namely, fire temperature calculation; cross-sectional thermal gradient evaluation and determination of mechanical response in box girders are elucidated. A simplified approach to account for thermal gradient distribution within girder section and deformations of PC box girder under hydrocarbon fire condition is incorporated into the FEM model. The applicability of the computer program for evaluating the fire resistance of PC box girder, resulting from combined effect of thermal and mechanical loading, is demonstrated through a case study. Through the numerical analysis results of case study, it is shown that different prestress degree adopted in girders has significant influence on the fire resistance of PC bridges.