震后火灾作用下导管钢框架失效机理及灾变过程研究

At present, the tube steel frame is mainly focused on the research of the mechanical behavior and the design method under earthquake and fire. At home and abroad, the research of the tube steel frame under post-earthquake fire is in the initial stage, and the corresponding research work needs to be improved. Therefore, the study mainly includes the following three aspects of research content: (1) Using the combine method of hybrid test simulation technology, numerical simulation and actual test, the initial damage of the tube steel frame and T type tubular joints caused by earthquake is accurately obtained, the main mechanical behaviors of the tube steel frame and T type tubular joints is obtained, including failure process, the damage evolution law, failure mode, failure mechanism and limit temperature.(2) The multi objective design theory of the tube steel frame under post-earthquake fire is put forward. The method lays the foundation for the the mechanical performance design of the main component of the tube steel frame under post-earthquake fire, and it provides a new idea for the design of the tube steel frame under post-earthquake fire.(3) Based on the comprehensive consideration of brittle damage, ductile damage and creep damage, the damage coupling model of multi mechanism is established to illustrate the interaction mechanism of brittle damage, ductile damage and creep damage.The research has important theoretical value and practical significance for exploring the damage evolution law and the failure criterion of the multiple damage mechanisms.

目前，对导管钢框架主要集中在单独考虑地震和火灾作用下力学行为及设计方法进行研究，国内外对震后火灾作用下导管钢框架研究处在起步阶段，相应研究工作尚需完善。鉴于此，本课题主要从以下三个方面开展研究工作：（1）采用混合试验模拟技术和试验相结合方法，准确引入地震引起初始损伤，探索震后火灾作用下导管钢框架和T型节点失效问题，对阐明震后火灾作用下导管钢框架和T型节点失效机制，揭示震后火灾作用下导管钢框架和T型节点损伤演化规律具有重要意义。（2）提出震后火灾作用下导管钢框架多目标设计理论，为震后火灾作用下导管钢框架重要构件综合考虑抗震抗火性能设计奠定基础，也为震后火灾作用下导管钢框架设计提供新思路。（3）定义新的损伤变量，建立综合考虑脆性损伤、延性损伤和蠕变损伤多机制损伤耦合模型，阐明复杂工况下多机制损伤耦合相互作用机理，揭示多种损伤机制相互作用破坏准则及损伤演化规律具有重要理论研究价值和实际意义。

由于油气泄露、电路短路及操作不当等原因，导管钢框架在地震后诱发次生火灾的概率极高。目前，对导管钢框架研究主要集中在单独考虑地震和火灾作用下力学行为和破坏机理，通常地震后造成导管钢框架损伤，严重影响导管钢框架抗火性能，降低导管钢框架抗火能力。因此，对地震频发区域导管钢框架进行震后火灾下力学性能、反应规律、设计方法和失效机理研究显得尤为重要，也可为导管钢框架结构重大灾害事故形成、扩展、控制与评估研究，都具有重要理论价值和广泛应用前景。该项目积极跟踪国内外相关研究动态，开展试验和参数分析研究，主要针对震后火灾作用下未加强T型相贯节点、单环加强T型相贯节点、两环加强T型相贯节点、三环加强T型相贯节点及导管钢框架结构的全过程反应、临界温度、失效机理和损伤演化规律进行深入分析研究，研究发现：（1）由于残余变形和残余应力的影响，损伤变量对未加强和加强型T型节点的耐火性能影响较大，随着损伤变量的增大节点的抗火性能降低；（2）对未加强T型节点而言，当损伤变量保持不变时，随着直径比β的减小和径厚比γ的增大，节点的临界温度最大可提高10%左右；（3）对内置加强环T型节点而言，当损伤变量保持不变时，随着参数β和η的增大加强T型节点的临界温度最大可降低15%，随着参数γ的增大加强T型节点临界温度会升高8%左右；壁厚比对两种T型节点的耐火性能影响不明显。（4）当火灾发生在甲板的两端时，导管钢框架的水平位移在整个升温阶段随着温度上升而逐渐增大；当火灾发生在甲板的中部时，导管钢框架在整个升温阶段水平位移随着温度的上升先减小后增大，且三种受火区域的水平位移都随着损伤变量的增大而增大，水平位移最大可以达到500mm。当火灾发生在甲板的中部时，导管钢框架的耐火性能最差，此时导管钢框架的临界温度为504℃，耐火时间为180s。