震损后钢管混凝土组合框架耐火性能评估与功能恢复策略研究

The earthquake is one of the most serious natural disasters, and the fire following earthquake (FFE) usually occurred as a type of secondary disasters. The mechanical behavior and capacity of structures is a key issue and significant project when the earthquake and FFE are considered as a combination, and it also is a advanced multi-disaster coupling research. This project will study systematically the significant technological issues on the mechanical mechanism and performance evaluation of composite frames with concrete-filled steel tubular (CFST) members under earthquake and FFE combination. The key scientific issues will be resolved based on a series of experiments and theory researches, including the reasonable earthquake damage of the CFST columns, composite beams and joints, the typical fire scenes, the analysis approach of the CFST members and structures under earthquake and FFE, the residual capacity of structures, the evaluation and assessment after earthquake and FFE, and the repair and strengthening of the members and structures. The typical experiments will be performed on the members and joints. The 3-D finite element analysis (FEA) model, micro elements model and multi-scale model will be developed to simulated the performance of the tested specimens. The test results are used to verify the FEA model. A micro detailed analysis should be performed to reveal the mechanism of accumulative damage, mechanical behavior, deformations and typical failure modes of the composite members. The performance assessment and restore strengthening approaches will be achieved to perfect the design theory and practical engineering for this type of structures.

地震作为最严重的自然灾害之一，往往伴随着震后次生火灾。考虑地震及其次生火灾共同作用下结构的力学行为及承载性能，属于多灾种耦合研究的课题，具有重要意义。本课题以钢管混凝土组合框架在遭受地震损伤后又受到次生火灾作用下的受力性能分析及评估为目标，对该类结构体系先后遭受地震作用和火灾共同作用下力学性能的关键技术问题进行系统研究，包括确定合理钢管混凝土柱、梁及节点等部件的地震损伤程度、震后次生火灾场景的确定、震损及火灾联合作用下钢管混凝土柱及组合框架结构体系受力性能分析方法、结构剩余承载能力评估、震后鉴定评估与修复加固措施建议等一系列关键科学问题的试验研究及理论模拟。通过典型构件或连接节点的地震及火灾耦合试验、三维单元与宏观单元混合建模及多尺度建模等多种数值模拟策略的联合应用，以期最终明晰其损伤累积机理、破坏机制和工作机理，为此类结构合理进行地震及火灾联合作用下的性能评估、鉴定及修复加固提供依据.

地震是最严重的自然灾害之一，且多伴随着次生火灾的发生，考虑地震和火灾先后作用下结构的力学行为，对提高城市防灾减灾水平具有重要意义。本课题完成了16根经历震损后的钢管混凝土柱耐火性能试验，试验工况包括2种轴压比和4种震损程度（无震损、轻度震损、中度震损、严重震损），通过试验明晰了震损对耐火性能的影响机理。此外，设计并制作了12个钢管混凝土柱-钢梁组合节点试件，其中方形柱截面节点试件5个，圆形柱截面节点试件7个，主要试验参数包括3种震损程度和2种受火工况。基于ABAQUS有限元分析软件，建立了震损后ISO-834标准火灾作用下钢管混凝土柱热-力耦合分析模型，对损伤后钢管混凝土柱进行了温度场和耐火性能分析。探讨了震损程度、轴压比、火灾荷载比、截面形式和含钢率对耐火极限和破坏模式的影响。引入基于刚度退化和滞回耗能的双参数损伤指数，以定量评估震损程度。对不同损伤指数的钢管混凝土柱高温下的受力机理、截面内力重分布以及破坏机制进行了对比分析。并进行了钢管混凝土柱-外环板式组合梁节点震损后火灾下的数值分析，对经历震损后的节点在高温下的柱轴向变形-时间关系曲线、梁竖向变形-时间关系曲线以及柱在高温下的膨胀变形进行了对比，详细考察了震损程度、梁柱线刚度比、材料强度、受火工况、柱火灾荷载比、梁火灾荷载比、防火保护层厚度等参数对该类节点震损后耐火极限和破坏模态的影响，并给出了构造措施建议。在此基础上，采用多尺度建模方法，对钢管混凝土组合框架进行了震损后火灾下的数值分析，剖析了震损后局部火灾作用下钢管混凝土组合框架的失效和倒塌机理。研究结果表明，地震引起的框架刚度降低的残余变形加速了火灾下结构的失效。本课题的研究结果可为此类结构合理进行地震及火灾联合作用下的性能评估、鉴定及修复加固提供依据。