Thermal Analysis of Concrete Box Girder Bridge Exposed to Interior Fire Using SAFIR

Box girder is a widely used bridge system and, consequently, quite common in Bangladesh. The structural capacity of such box girders can be significantly affected during fire exposure due to their thin webs and prestressing tendons. In this study, the thermal behavior of prestressed concrete (PC) box girder sections exposed to both standard and hydrocarbon fire within the interior hollow part has been investigated using the nonlinear FEM software SAFIR. The standard fire has been used to simulate any accidental fire that could occur during the construction or operation phase of a box girder structure. On the other hand, hydrocarbon fire has been applied to simulate an explosion of gas pipelines that could run through the interior of a box girder section. A parametric study has been conducted with varying web thickness and fire duration (ranging between 30 and 240 min) in order to observe the effect of such parameters on the structural capacity of fire-affected box girder section. It has been found that type and duration of fire could have significant impact on the structural capacity of the PC box girder. A preliminary understanding of the effectiveness of a box girder section after a fire event can also be obtained from the outcome of the study. For instance, a web thickness of 200 mm or higher for hollow PC box girder, have been found to be effective for fire exposure considered in the study. However, further investigation with representative fires and variable parameters will be required to develop a comprehensive guideline.