【作者】 祁佳睿；

【导师】 苏幼坡；

【作者基本信息】 河北理工大学 ， 结构工程， 2007， 硕士

【摘要】 防止框架结构连续倒塌的关键在于当某一竖向支撑失效后,其上的框架梁是否具有足够的延性和“搭桥”能力形成新的传力途径,在形成新的传力途径时框架梁的跨度成倍增加,其内力将大大超过原由按一般荷载组合的设计内力。若按此内力设计框架梁,必然使梁的截面和配筋很大,这样做一方面不经济,同时会使框架成为强梁弱柱结构,不利于抗震。因此,钢筋混凝土的拱效应和索效应的分析,对防止钢筋混凝土梁发生竖向连续倒塌的产生有重要的意义。本文以钢筋混凝土框架梁为研究对象,应用ADINA大型有限元软件,考虑材料非线性和几何大变形建立框架梁抗倒塌性能分析模型,分析拱效应、索效应对钢筋混凝土框架梁承载力的提高,探讨了配筋率、跨高比和支座约束对框架梁抗倒塌能力的影响,并通过试验验证了模型的正确性,论文主要完成了一下三个方面的内容:首先,利用ADINA软件对钢筋混凝土框架梁进行了有限元分析,从网格划分、单元类型、收敛准则、收敛精度四方面进行计算,得出比较精确的分析模型。其次,按照有限元分析模型,对钢筋混凝土框架梁进行破坏数值模拟,并通过建立生死单元的方式模拟混凝土退出工作后承载力变化,分析拱效应索效应对钢筋混凝土框架梁抗倒塌能力的影响。分析结果表明:由于轴力的存在使混凝土梁形成了比较明显的拱效应,以及当混凝土退出工作后,钢筋形成“索”继续承担荷载的索效应,使得钢筋混凝土框架梁承载力较设计值有较大幅度的增长,进而提高钢筋混凝土梁的抗倒塌能力。最后,探讨了跨高比、配筋率、支座约束等控制因素的改变对钢筋混凝土框架抗倒塌能力的影响,根据前期试验结果建立了23个计算模型,其中配筋率8个,跨高比7个,支座约束8个。分析表明,随着跨高比、配筋率的增加,拱效应呈明显的减小趋势,而索效应随着跨高比的增加而减小,随着配筋率的增加而增大。支座约束刚度也对钢筋混凝土框架梁拱效应的提高有一定的影响,水平约束刚度越小,承载力提高系数越不明显。更多还原

【Abstract】 The key of resisting progressive collapse of frames is that when the vertical loading invalidated the frame beams has sufficient ductility and "bypass" to form new internal force or not. Transmission paths in the new fram beams has increased which greatly exceeding its internal force which is formed by the combination of design loads. If frame beam design with the internal force which make the section and the reinforcement ratios too large,so this is not one economy. And it has very important significance of compressive and tensile membrane action analysis of reinforce-concrete frame’s beam to resist progressive collapse.This paper use nonlinear finite element analysis with Automatic Dynamic Incremental Nonlinear Analysis (ADINA) software for the prevention of progressive cpllapse of the reinforced concrete frame’s beam. The finite element model has been founded accuratelily contrast by the test in this project. It shows that the infection of compressive and tensile membrane action to the beam. Through the model it is also discussed the effect factors such as steel ratio,span-depth ration and boundary condition.Reinforced concrete frame’s beam is analyzed through matrial nonlinear and large displament method on the basis of ADINA .The computation for mesh plot, element type, iteration method and iteration tolerances shows a accurate model.According to the finite element model, the beam is numerical damage simulated through founding brith-death element. The method can simulatae the beam’s loading capacity after some out-worked concrete. Then it can educe the effect of tensile membance action for resisting progressive collapse. It shows obvious compressive membrane action because of the exit of axial force. And after concrete out-worked the steel formed“cable”takes on the loading.Thanks to the membrane action the loading capacity is larger than the design value which advanced the beam’s capacity of progressive collapse.It is also discuss the effect factor of the beam’s progressive collapse such as steel ratio,span-depth ration and boundary condition. According to prophase test result it is based 23 computative models,including 8 steel ratios,7 span-depth rations and 8 boundary conditions.It shows that alone with the steel ratio and span-depth ratio the compressive membrane action trend to decreasing obviously and tensile membrane action decreasing with the span-depth ratio and increasing with the steel ratio. Otherwise the stiffness of boundary condition effected the capacity of reinforced-concrete frame’s beam prevention of progressive collapse. Larger level stiffness larger compressive membranaction.更多还原