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预应力钢结构是一种具有广泛应用前景的结构形式,但在火灾作用下,其整体性能将发生变化并引起整体结构破坏。在前期工作的基础上,从结构响应机理出发建立了平面预应力钢桁架结构火灾高温下的结构响应计算模型。该模型可任意设置多道折线钢索单元并多次张拉施加预应力。从方便应用的角度出发,对高温下钢材的EC3本构模型进行了简化,使其各阶段有了统一表达式。利用该计算模型分别对两种不同布索方案的预应力管桁架进行了火灾行为分析,讨论了不同参数变化对火灾作用下整体结构承载力的影响规律。结果表明,钢索的设置方案、预应力度、外荷载、材料等级等因素对于火灾下预应力钢结构的整体性能和承载力均产生一定影响,不同的布索方案将对应不同的临界温度,外荷载较大时临界温度较小,而预拉力的影响又与布索方案有关。此结论对于深入开展预应力钢结构火灾行为分析及其抗火设计具有重要的指导意义。
Prestressed steel structure is a widely used form of the structure, but under the fire, its overall performance will change and cause the overall structural damage. Based on the previous work, a structural response calculation model of the plane prestressed steel truss structure fire under high temperature was established from the structural response mechanism. The model can be arbitrarily set multi-lane wire unit and multiple tensioning prestress. From the point of view of convenience application, the EC3 constitutive model of steel under high temperature is simplified, and the unified expressions of all phases are obtained. The calculation model was used to analyze the fire behaviors of prestressed pipe trusses with two different cable layouts respectively. The influence of different parameters on the bearing capacity of the whole structure under fire was discussed. The results show that the setting of cable, prestressing force, external load, material grade and other factors have an impact on the overall performance and bearing capacity of prestressed steel structures under fire. Different cloths programs will correspond to different critical temperatures, When the external load is larger, the critical temperature is smaller, and the influence of pre-tension is related to the Boussoux solution. This conclusion has important guiding significance for the further analysis of fire behaviors of prestressed steel structures and their fire-resistant design.