This paper presents a detailed investigation in to fire resistance along with failure mode in continuous steel-concrete composite twin I-shaped bridge girders under different localized fire through considering fire severity and fire exposure positions namely; mid-span zone in one of the two span, hogging moment zone and side-support zone. A 3-D finite element (FE) model, built utilizing the computer program ANSYS, is used to track structural fire performance in a typical two span of continuous composite twin I-shaped bridge girders (fabricated with twin I-shaped plates supporting a concrete slab) dependent on thermomechanical coupled analysis. The model validation is undertook through comparison of temperature and deflection response attained from a scaled composite single I-shaped girder tested exposed to ISO834 fire. The numerical analysis results show that the developed model can be favorably used to analyze the behavior and failure mode of continuous steel-concrete composite twin I-shaped bridge girders during entire range of fire exposure. Fire severity and fire exposure positions present critical influence in to the fire resistance of continuous composite bridge girders. Fire exposure prevention on hogging moment zone can significantly extend failure time of continuous girders, and further hold back progressive structural collapse. Web buckling based failure criterion can be applicable to calculate fire resistance of realistic continuous girders under simultaneous structural loading together with localized fire. Continuous composite bridge girders subjected to localized fire present highly significant local deformation response in the fire exposed bridge girder span.

通过考虑火灾的严重程度和受火位置，对连续钢-混凝土组合双工字形桥梁在不同局部火灾下的耐火性及破坏模式进行了详细的研究。跨度中段位于两个跨度之一，即弯矩区和侧支撑区。利用计算机程序ANSYS建立的3-D有限元（FE）模型用于跟踪典型的两跨连续复合双I形桥梁（由支撑混凝土的双I形板制成）的典型跨度中的结构防火性能平板）取决于热机械耦合分析。通过比较暴露于ISO834火中的按比例缩放的复合I形单梁获得的温度和挠度响应，进行模型验证。数值分析结果表明，所建立的模型可以很好地用于分析连续钢-混凝土组合双工字形桥梁在整个火灾过程中的行为和破坏模式。火灾的严重性和暴露的位置对连续复合材料桥梁的耐火性具有至关重要的影响。防止在起步力矩区域着火，可显着延长连续大梁的破坏时间，并进一步阻止结构性逐步倒塌。基于腹板屈曲的破坏准则可适用于同时承受结构荷载和局部火灾的真实连续梁的耐火性计算。