火灾后焊接空心球空间网格结构残余力学性能研究

As the space lattice structures have been widely used in various fields, the number of their fire accidents shows an increasing trend. Generally, entire structural collapse will not happen to most of the space lattice structures in the fire, and usually they will be reused after reinforcement. However, most of the reinforcement scheme ignores the deterioration of mechanical properties of the materials, the joints, and the members; moreover, the influence of the internal force redistribution and the residual deformation after fire is rarely considered. It is the common practice to only reinforce the parts which have obviously deformed and been completely destroyed. Thus a fair number of weak areas may be neglected, which will give rise to potential safety risks. .In this project, based on the finished study on the post-fire mechanical properties of structural materials, experiments and theoretical analysis will be conducted on the welds, welded hollow spherical joints, and steel tube members after exposure to fire temperatures under constant load. The effects of factors such as material strength, specimen dimension, stress state during high temperatures, exposure temperatures and cooling methods on the residual bearing capacity of the specimens are studied and the degradation mechanism of the mechanical properties are obtained. Then the computing methods of post-fire residual bearing capacity of welded hollow spherical joints and steel tube members are expected to be established combined with parametric finite element analysis and theoretical derivation. Subsequently, the distribution law of the internal force redistribution and residual deformation of the structure after fire will be analyzed through the full-process simulation of the fire hazards, and then the post-fire residual static and dynamic performances as well as the wind, seismic ability of the structure will be studied. The results are expected to lay a scientific foundation for the safety assessment and reinforcement of space lattice structures after fire exposure.

随着空间网格结构在各领域的广泛使用，其火灾事故逐年上升，大量火灾后的结构未发生整体破坏，通常对其加固后投入使用。但是，目前多数加固方案忽略了火灾后材料、节点和杆件的力学性能退化，未考虑火灾后结构内力重分布和残余变形的影响，通常只对明显变形和破坏部位补强，可能使得薄弱区域疏于加固，埋下安全隐患。本项目在已完成的材料高温后力学性能研究的基础上，继续开展焊缝、焊接空心球节点和圆管杆件在恒载高温处理后的力学性能试验，研究应力状态、过火温度、冷却方式、构件尺寸等参数对高温后残余承载力的影响规律，得到节点与杆件的力学性能退化机理，结合有限元参数分析和理论推导，建立火灾后焊接空心球节点和钢管构件的残余承载力计算方法；通过火灾全过程模拟，分析火灾后焊接空心球空间网格结构内力重分布、残余变形的分布规律，研究火灾后结构残余静动力性能和抗风、抗震能力，为火灾后空间网格结构安全评估与修复加固提供科学依据。

火灾后焊接空心球空间网格结构安全评估与加固方案设计过程中，多忽略了火灾高温后材料、节点和杆件的力学性能退化，以及内力重分布和残余变形的影响，可能使得薄弱区域疏于加固诱发结构安全的问题。针对此问题，本项目采用理论分析、数值模拟和试验研究相结合的方法，研究了火灾后对接焊缝、焊接空心球节点和圆管构件力学性能的退化机理，揭示了负载状态、材料强度、试件尺寸、过火温度和冷却方式等参数对剩余承载力的影响规律，提出了火灾后对接焊缝、焊接空心球节点和圆管构件剩余承载力计算方法。通过火灾全过程分析，揭示了火灾后空间网格结构内力重分布和残余热变形分布的规律，分析了火灾后结构的稳定性能、抗风性能和抗震性能。发表高水平学术论文13篇，申请发明专利1项；培养博士生1名，硕士生7名。成果编入中国工程建设标准化协会标准《火灾后钢结构损伤检测鉴定技术规程》，为火灾后钢结构性能评估提供了科学依据。