受火条件下整体结构中组合梁破坏形态研究

Study of the Composite Beam′s Failure Modes in Whole Structure under Fire

目的研究火灾作用下整体结构中组合梁的抗火性能和破坏形态.方法通过自行设计的火灾试验炉对整体结构中组合梁进行试验研究,试验区分组合梁拼接节点受火和不受火两种工况.测量炉温和组合梁截面沿高度温度场分布;描述了组合梁混凝土板面裂缝出现、开展情况及组合梁的破坏形态.结果火灾条件下整体结构中组合梁能很好地共同工作;火灾过程中组合梁混凝土板温度滞后钢梁温度而受拉产生复杂裂缝,而且组合梁受约束越强,裂缝开展越剧烈.结论组合梁拼接节点焊缝在降温阶段被拉裂,为防止火灾中组合梁混凝土板面产生复杂裂缝,建议混凝土板负弯矩钢筋不应按常温设计全部截断,应有部分钢筋贯通以承受火灾中产生的温度应力.

The special fire furnaces were designed to study the fire resistance and failure modes of composite beams in whole structure under fire.The behaviors of two composite beams with 2 types of fire conditions were studied.Also,the temperature distributions along composite beams and atmosphere were measured,as well as the detailed description of concrete slab surface cracks and the failure modes of composite beams during the experiments.The results showed that the composite beams in whole structure worked together well in fire;complex cracks of concrete slab surface generated on account of temperature below steel beams and composite beams suffered more restrictions,and the cracks became more complex.It came to the conclusion that the rupture of connection welds were emerged in the cooling phase,as well as the whole top bars should not be cut as routine design and some run-through top bars could withstand temperature stress.