考虑楼板组合效应的多层钢框架抗连续倒塌性能分析

Behavior of multi-story steel frame considering influence of composite slab to resist progressive collapse

为了研究考虑楼板组合效应的多层钢框架抗连续倒塌性能,制作了1个两层两跨1/2缩尺的中柱失效工况的钢框架梁-柱子结构模型试件。对试件进行竖向推倒(Pushdown)加载,研究其在倒塌过程中的抗力曲线、内力变化以及破坏模式。试验结果表明:钢框架结构主要依靠钢梁发展的弯曲机制和悬链线机制抵抗外加荷载,且悬链线机制具有一定滞后性。通过有限元分析软件ANSYS/LS-DYNA对试件进行数值模拟,建立带板框架模型,并进行抗力分析,研究楼板组合效应对多层钢框架抗连续倒塌性能的影响;同时,开展拓展参数分析,通过抗力分析研究混凝土强度等级、楼板厚度和不同去柱工况对带板框架抗连续倒塌性能的影响。有限元分析结果表明:带板框架的抗连续倒塌能力远大于不考虑楼板组合效应的钢框架。考虑楼板组合效应后,钢框架的边柱梁端焊缝由受拉破坏转变为受压屈曲破坏。增大楼板厚度,能够提高带板框架弯曲机制抗力,但削弱了悬链线机制抗力并降低了结构的变形能力。由于边柱失效工况的带板框架缺乏有效水平约束,其承载力较中柱失效工况的降低了39.9%,但变形能力提高了30.6%。

In order to study the behavior of multi-story steel frame considering the influence of composite slab to resist progressive collapse,a two-story by two-bay half-scale steel subassembly specimen under the loss of middle column scenario was fabricated.The specimen was tested subjected to pushdown loading.The load-displacement responses,load resisting mechanism as well as the failure mode among structural components during the collapse process were obtained and discussed in detail.The test results show that flexural action and catenary action worked together to help redistribute the applied load,and the catenary mechanism has a certain hysteresis.The numerical simulation was carried out by using finite element analysis software ANSYS/LS-DYNA.Subsequently,the finite element mode of frame with slabs was established to analysis the influence of slab to multi-story steel frame through the load-displacement responses.At the same time,extended parameter analysis was carried out to quantify the effects of concrete strength,concrete slab thickness and different column removal scenarios on the behavior of composite subassemblies to resist progressive collapse by load resisting mechanism.The finite element analysis results show that the resist progressive collapse capacity of the frame with slab is much greater than the steel frame without considering the influence of composite slab.After considering the influence of composite slab,the tensile failure of steel frame changes to the compressive buckling failureat the beam end of edge column.As the thickness of the concrete slab increases,the resistance of the flexural mechanism increases significantly,but it will weaken the resistance of the catenary mechanism and reduce the deformation ability of the structure.For the scenario of loss edge column,due to the lack of effective horizontal restraint,the bearing capacity of specimen is reduced by 39.9%compared with the scenario of loss middle column,the deformation capacity is increased by 30.6%.