大空间建筑火灾下弦支穹顶结构的力学行为及抗火设计理论研究

Suspension domes have been widely used as large-span roofs. Due to the introduction of flexible pre-stressed steel cables, the fire performance of Suspension domes is deemed to be different from that of conventional rigid steel structures. Set against this background, it is significant to identify the uncertainties on its fire behaviours, technically from the level of materials to the levels of isolated components and sub-assemblies. Mechanical properties of the pre-tensioned steel cable at elevated temperatures will be firstly updated by adopting a novel non-contact video gauge system which is different from conventional way using extensometer. This is to improve accuracy of the measurements. Then, heat transfer analyses will be carried out to determine temperature distribution in the pre-tensioned cable by using lumped-parameter method and considering the cavity radiation effect. The main aim is to investigate the fire performance and failure modes of the suspension domes exposed to localized fires. In general, the pre-stressed cable is subject to a friction force at joint of the cable and vertical strut. With regard to this point and for better simulating cable relaxation, a mechanical model of cable-strut joint will be developed and numerical simulation considering both of material and geometrical nonlinearities will be carried out to trace the failure modes of the suspension dome under localized fires. Consequently parametric equations will be provided for the deflection of top single layer grid structure and the cable tension force based on a vivid parametric analysis. The behaviours of the joint and global pre-tensioned cable at elevated temperature will be further demonstrated by fire tests. Based on the analytic and experimental studies, practical fire resistant design theory for the suspension dome will be provided at cable relaxation state and progressive buckling state, respectively, and the research outcomes are expected to provide basis for establishing relevant fire safety design codes.

在刚性网壳下部引入柔性预应力索撑体系所形成的新型预应力弦支穹顶结构，较多应用于大跨度公共建筑屋盖，其受火力学反应区别于刚性结构，亟待对其开展从材料到构件直至结构层次的抗火研究。本项目采用非接触式应变视频测试技术，进一步完善钢索体高温力学性能指标体系；建立考虑空腔辐射效应的索体升温模式及简化计算方法；完善大空间建筑火灾非均匀升温下弦支穹顶结构力学响应全过程数值追踪方法；其中，针对环索在非均匀升温下的应力重分布现象，重点开展索撑节点的界限滑移单元研究；从而探明非均匀升温下连续环索松弛机制及索系失效路径，对弦支穹顶结构抗火性能的影响；建立多参数影响下，上部网壳结构的瞬态几何位形函数及下部索系的瞬态索力函数；开展索撑节点模型及弦支穹顶结构模型的非均匀受火试验。基于试验和理论研究，最终凝练出遵循性能化抗火设计思想的弦支穹顶结构受火失效判别准则及抗火设计理论，为相关防火设计标准的编制提供理论依据。

在刚性网壳下部引入柔性预应力索撑体系所形成的新型预应力弦支穹顶结构，较多应用于大跨度公共建筑屋盖，其受火力学反应区别于刚性结构，亟待对其开展从材料到构件直至结构层次的抗火研究。本项目采用非接触式应变视频测试技术，进一步完善钢索体高温力学性能指标体系；建立考虑空腔辐射效应的索体升温模式及简化计算方法；完善大空间建筑火灾非均匀升温下弦支穹顶结构力学响应全过程数值追踪方法；其中，针对环索在非均匀升温下的应力重分布现象，重点开展索撑节点的界限滑移单元研究；从而探明非均匀升温下连续环索松弛机制及索系失效路径，对弦支穹顶结构抗火性能的影响；建立多参数影响下，上部网壳结构的瞬态几何位形函数及下部索系的瞬态索力函数；开展索撑节点模型及弦支穹顶结构模型的非均匀受火试验。基于试验和理论研究，最终凝练出遵循性能化抗火设计思想的弦支穹顶结构受火失效判别准则及抗火设计理论，为相关防火设计标准的编制提供理论依据。