钢筋混凝土框架结构层间位移与构件变形关系研究

基于课题组已完成的钢筋混凝土3层3跨平面框架低周反复加载试验,以边(中)节点区域作为重点研究对象,分析了梁柱组合体中各种非线性局部变形引起的侧移在结构总层间变形中所占比例的变化规律。在此基础上,建立了构件局部变形与结构层间位移的转换关系。研究结果表明:对于发生"梁铰"破坏机制的框架结构,梁端转动对节点剪切变形的影响大于柱端转动,梁柱组合体作为整体共同承担结构的塑性变形;当结构整体位移角满足相应性能水平限值时,局部构件的变形仍有可能超限,简单利用单个构件的变形代表结构整体的变形是不合理的;对于破坏形式为"梁端弯曲破坏"的框架子结构,随着损伤加剧结构进入非弹性阶段后,梁变形成为层间位移的主要成分,柱变形引起的层间位移所占比例次之,节点剪切变形引起的层间位移所占比例最小;通过弹性理论分析,在塑性阶段引入塑性折减系数,推导建立的构件局部变形与结构层间位移转换关系式具有相对较高的精度,计算结果与试验实测数据基本吻合。

Relationship between inter-story drift of RC frame structures and deformation of members

The proportion of the lateral displacements arised from individual nonlinear deformations in beam-column subassemblage to the structural inter-layer displacements was analyzed based on the exterior-joints and interior-joints of three-story, three-span reinforced concrete plane frames under low cyclic loading. Besides, the transformational relationship between the inter-story drift of RC frame and the deformation of local components was established. The results show that the influence of beam-end rotation on the shear deformation of joint is greater than that of column in the frame structure characterized by ‘beam-hinge’ failure mechanism, and the beam-column subassemblage takes on the structural plastic deformation as a whole. The deformation of local components may exceed the limiting values of performance levels even the inter-story drift angle of the structure meets the requirements, so it is improper to use the deformation of single member instead of the whole structural displacement as the collapse criterion. For the substructure with the ‘beam-end bending’ failure mode, the deformation of beams takes up the largest part of inter-story drift, the deformation of columns takes the second and the shear deformation of joints takes the smallest. Based on the elastic theory analysis, a plasticity reduction coefficient was proposed during the plastic stage and a high precision conversion formula between the inter-story drift of structure and local deformation of components is established. The calculated results are in agreement with the test results basically.