【作者】 李凤武；

【导师】 肖岩；

【作者基本信息】 湖南大学 ， 结构工程， 2014， 博士

【摘要】 近几十年,随着工程技术水平的不断提高,建筑结构向大型化、复杂化方向发展。与此同时,结构安全性要求也不断提高。自从“9.11”事件之后,结构的抗连续倒塌研究日益引起人们重视。在工程结构漫长的使用寿命里,可能遭遇各种偶然突发灾害事件(偶然作用),如爆炸、冲击、火灾等,不可避免地会导致结构局部破坏或损伤,如果剩余结构不能有效地承担结构初始破坏和损伤造成的不平衡荷载或内力变化,剩余结构就会进一步发生破坏,这种破坏可能引起多米诺骨牌式的连锁反应,导致破坏在结构系统内不断发展,从而造成结构的大范围内严重破坏甚至整个结构的倒塌,也就是连续性倒塌。本文在“985”工程专项经费(编号：531106004003)、“千人计划”专项经费(编号：531106004009)、教育部“建筑安全与节能”重点试验室的资助下进行了大比例框架的竖向构件突然失效倒塌试验研究工作,并结合有限元和数值分析的方法进行专项研究,主要研究内容如下：1.在大比例结构抗连续倒塌试验中,利用氢气冲击炮实现了竖向构件快速失效,该方法设备简单,安全可靠,对试验数据的采集干扰小,并通过试验验证了这个方法的可行性。2.对试验构件的拆除顺序和位置、试验构件的拆除方法、试验的加载方法以及试验数据的采集方法进行了专项研究,以保证试验取得预期的成果。3.为研究框架结构在边柱、中柱突然失效瞬间结构的动力反应、内力重分布和破坏形态,进行了1/2比例三层三跨钢筋混凝土框架的倒塌试验。通过研究破坏瞬间结构的位移反应、加速度反应、钢筋应变和裂缝分布情况,揭示了结构在竖向构件失效时的抗倒塌性能。试验结果表明按照抗震规范进行设计的框架结构在底层单个边柱或单个中柱突然失效时具有较好的抗连续倒塌性能；在底层两个边柱突然失效时将产生较大的变形,结构产生严重破坏,并导致局部倒塌。同时试验发现结构的后期变形在倒塌过程中具有重要意义。4.采用SAP2000有限元程序进行了线性动力分析,对结构在试验瞬间的受力状态进行了模拟,分析结果与试验结果吻合良好；同时采用SAP2000有限元程序进行了非线性静力分析,用于分析结构在竖向构件失效后塑性铰产生的顺序,从而揭示结构内力变化的过程；并根据悬链效应计算出了结构的极限荷载。5.通过数值分析与试验相结合的方法重点研究了结构在竖向构件失效时产生的动力效应问题,研究表明因结构材料在快速荷载作用下强度提高、变形滞后的原因,动力效应对结构的影响并不显著。6、根据试验过程中观测到的结构变形和试验现象,阐述了结构在竖向构件突然失效后的倒塌过程,并将倒塌过程分为四个阶段,对各个阶段结构变形特点、内力变化规律进行了细致的分析。7、总结了各次试验中出现的裂缝分布规律、结构薄弱部位并相应提出了抗连续倒塌设计建议,用于指导抗连续倒塌设计工作。更多还原

【Abstract】 With the improvement of engineering technology in recent decades, building structures develop in the direction of large-scale and complex. In the meantime, since "911" event, research on progressive collapse have been paid close attention. During the long service life, when suffering from the casual extreme load caused all of a sudden by the events such as explosion, impact and fire, engineering structure will take on local damage. If the rest of structure can not undertake the unbalanced load or internal force changes caused by initial damage, further damage will be happened which may trigger dominoes effect and chain reactions.The reactions will make local damage continue to develop in structural system, resulting in large-scale serious damage and even collapse which called progressive collapse.Under the support of985Projects (531106004003), the One-thousand Talent Programs (531106004009), Key Laboratory of Buliding Safety and Energy Efficiency of the Ministry of Education, experimental study on sudden vertical member removal of a large-scale frame has been carried out and customized researches combined finite element method with numerical analysis have been done. The main researches as follows:1. The problem how to make vertical member failure suddenly has been solved with the use of hydrogen gas gun during the experiment of progressive collapse of large-scale frames. The feasibility of this method which has the advantages of low-cost equipment, security and reliability, and low interference effect on collecting experimental data has been verified.2. Customized researches on the removal sequence and location, removal method of specimen, load method and collection method of experimental data have been carried out to make sure the expected results.3. Collapse tests of a1/2scale3-bay and3-story space reinforced concrete frame model with sudden side and middle columns removal have been carried out to study the dynamic response, internal force redistribution, and failure model of frame. The displacement response, acceleration response, reinforcement strain and crack distribution during the collapse of the frame are studied to reveal the progressive collapse resistance with sudden vertical element removal. Testing results show that the RC frame designed according to Chinese Seismic Code has good behavior against progressive collapse caused by sudden loss of a first floor side or middle column, while has large deformation, serious damage and lead to collapse caused by sudden loss of two first floor side columns.4. Linear dynamic analysis is carried out using the finite element software SAP2000and numerical simulation on the stress state of RC frame is performed. It is found the analysis results agree well with the test results. Nonlinear static analysis is also carried out using SAP2000to analyze the sequence of plastic hinge after vertical element loss in order to reveal the internal force change progress of structure. Furthermore, the ultimate load is calculated according to catenary action.5. The dynamic effect problem which is caused by failure of vertical element is studied combined numerical simulation with experiment method. It is indicated that dynamic effect is not significant to structures due to the reason of strength enhancement and deformation hysteresis of material under fast loading.6. The collapse process of RC frame with sudden column removal is presented according to the observed deformation and phenomenon during the testing which is divided into four stages. Detailed analysis on deformation characteristics and the law of internal force changes of each stage is performed.7. The crack distribution and part of weakness during each test are summarized and some suggestions on the resistance of progressive collapse are put forward for guidance of progressive-collapse resistance design.更多还原