全装配式混凝土框架结构抗连续倒塌破坏机理研究

Failure mode research of fully assembled precast concrete frame structure under progressive collapse test

现有的建筑结构抗连续倒塌研究主要针对现浇结构展开,对装配式结构讨论的相对较少。为研究全装配式混凝土框架结构在中柱失效情况下的抗连续倒塌性能,从某四跨七层空间框架结构底部提取出一榀单层两跨的框架子结构,按照1/2缩尺比例分别设计了一个现浇(RC)试件和两个全装配式(PC)试件,其中PC试件在梁柱节点处分别采用明(暗)牛腿-插梢杆-角型钢板的连接方式。对上述试件分别开展了中柱移除状态下的静力试验,并对加载过程中测试所得的结构持荷能力、构件应变响应及失效破坏模式依次进行了分析。试验结果表明,RC试件在加载过程中先后产生了压拱效应和悬链线效应,而PC1试件只出现了压拱效应阶段,PC2试件也仅发展了短暂的悬链线效应,均表明该类型全装配式结构的二次抗倒塌能力相对不足。试验过程中,RC试件梁端部及跨中截面处纵筋应变响应均达至屈服状态,而PC试件的受力及变形区域则主要集中在节点连接处,表明其构件的材料利用率不如现浇结构充分。同时,PC1和PC2试件的极限承载力分别为RC试件在压拱效应阶段峰值荷载的76%和81%,相应极限位移仅为RC试件的72%和77%,表明该全装配式结构与现浇结构相比承载力和延性均相对有限。结构失效模式方面,RC试件最终由于梁端纵筋被拉断而发生破坏,PC1及PC2试件则分别因节点处插销杆被剪断及梁端混凝土被压溃而丧失承载力,表明插销杆抗剪强度和节点区域混凝土抗压强度为该类型全装配式结构抗连续倒塌设计的关键参数。

The existed architecture progressive collapse research are mainly focused on the cast-in-place concrete structures,which is less discussed around the prefabricated structures.To explore the performance of the fully assembled concrete frame structure under the mid-column loss scenario,a two-span single-story sub-structure was selected from a four-span seven-story frame structure,and a reinforced concrete(RC)concrete specimen and two precast concrete(PC)concrete specimens were built with the 1/2 reduced scale,respectively,where the exposed/hided corbel with dowel rob and angel cleat joint connections was employed in the PC specimens,respectively.The static load tests were conducted for the specimens under mid-column loss scenario to discuss the structural loading capacity,reinforcement strain responses and failure patterns.The experimental results has revealed that both of the compressive arch action(CAA)and catenary action(CTA)has formed during the loading process of RC specimen,while only the CAA was occurred in PC1 and the temporary CTA was formed in PC2,showing that a lack of structural secondary progressive collapse performance for this type of fully assembled PC structure.During the loading tests,the reinforcements at the beam-end and mid-span section of RC specimen has both reached into the yield state,while the deformation of PC specimens were mainly concentrated on the beam-column joint connections,showing that a lower material performance utilization ratio in this type of assembled structures.Meanwhile,the ultimate loading capacity of PC1 and PC2 specimen was only 76%and 81%times of the peak load of RC specimen at CAA stage,and the ultimate displacement was only 72%and 77%times of RC specimen,correspondingly,indicating that the loading and ductility capacity of the PC structure was relatively lower than the RC structure.As for the structural failure patterns,the RC specimen was damaged by the tensile failure of longitudinal reinforcements in beam-end,while the PC specimens were damaged by the shear failure of dowel rob and the crush of concrete at beam-end,respectively,indicating that the shear capacity of dowel rob and the compressive capacity of concrete in joint area plays an important in the progressive collapse behavior of this type of fully assembled structures.