基于平衡态和非平衡态传热分析半刚性连接受力机理及钢结构性能化抗火设计方法研究

In research of structural fire engineering, performance of bolted beam-to-column connections has been simplified in analysis of structural behavior, and these were assumed to possess sufficient mechanical properties for retaining their structural integrity and stability in a fire situation. In study of structural fire resistance, due to degradation of material properties at high temperatures, mechanical performance and interaction mechanism of structural members, including steel connections, are highly dependent on temperature variation. The proposed research scheme is dedicated to investigating variability of fire load density in an enclosure, in combination with energy and mass conservation, and proposing a mathematical model for representing temperature variation in a real fire in this enclosed space. In the standard and real fires, comparatively studying connection performance and interaction mechanism in a sub-framed structure should be beneficial. Adopting a coupled thermal-mechanical numerical model, a theoretical model for a simplified sub-framed structure and experiential testing (based on steady and non-steady heat transfer) is to in-depth investigate load transferring mechanisms between structural members and failure modes for bolted connections, and finally establishing a beam-connection-column interaction working theory for proposing a performance-based fire design method with consideration of semi-rigid connection performance for a real fire. Research findings would enrich the performance-based fire design approach and computational theory, which is of great importance for ensuring structural integrity and preventing the progressive collapse of a steel-framed building in a fire situation.

在钢结构抗火研究中，钢结构连接半刚性力学性能通常被简化或忽略，而假定连接拥有足够力学性能来保证结构整体稳定性。但是，由于高温中钢材材料力学性能的衰减，导致钢连接力学特性及钢构件间相互作用机理随温度的改变而发生变化。本项目通过对室内可变火灾荷载密度和火灾热释放率分析，结合空间内能量与质量守恒，提出可以描述室内温度场全过程变化的真实火灾燃烧数学模型。采用该火灾燃烧模型和标准火灾模型，对比分析钢连接在子框架结构中受力机制和构件相互作用机理的差异；同时采用热力流固耦合模型，子框架结构理论分析模型和结构抗火实验(稳态和非稳态传热)，对钢结构构件之间荷载传递机理和钢结构连接破坏模式和受力特性进行研究，建立梁-节点-柱空间作用理论，并以此为依据，提出一种新的钢结构性能化抗火设计方法。研究成果将有效地丰富钢结构性能化抗火设计与计算理论，对保证钢结构在火灾中的结构整体性和防止结构发生连续性倒塌具有重要意义。

在钢结构抗火研究中，钢结构连接半刚性力学性能通常被简化或忽略，而假定连接拥有足够力学性能来保证结构整体稳定性。其中，最关键因素之一是高温中高强螺栓材料力学性能比普通钢材的衰减得更快，导致钢连接力学性能及钢构件间相互作用机理随温度的改变而发生变化。本项目通过对高强螺栓的在高温和火灾后力学性能的研究，结合材料力学性能的可靠度分析，提出可以描述不同高强螺栓材料性能衰减数学模型以及本构模型。采用相应的本构模型和火灾模型，分析钢连接在子框架结构中受力机制和构件相互作用机理的差异；同时采用热力流固耦合模型，子框架结构理论分析模型和结构抗火实验(稳态和非稳态传热)，对钢结构构件之间荷载传递机理和钢结构连接破坏模式和受力特性进行研究，建立梁-节点-柱空间作用理论，并以此为依据，提出一种新的钢结构性能化抗火设计方法。研究成果将有效地丰富钢结构性能化抗火设计与计算理论，对保证钢结构在火灾中的结构整体性和防止结构发生连续性倒塌具有重要意义。