柱支承双向板及板柱节点的设计与研究

Study and design of column-supported slab and its connection

冲切面斜裂缝过早发生和最终的冲切破坏严重地影响着板柱节点的延性,制约着整个结构的抗震性能。在已有研究成果和板柱节点破坏机理的基础上,提出了柱支承双向板小震不裂、中震弹性、大震仍能继续承受竖向荷载作用效应和地震作用效应,保持结构完整性的抗震设防目标。建立了实现抗震设防目标的正截面和斜截面计算的应力表达式。将小震的最大主剪应力不大于混凝土轴心抗拉强度标准值作为控制板厚的指标。正截面极限状态承载力计算中,计入了斜裂缝发生后的剪力补偿。工程实例表明,按照现行规范的构造要求和中震弹性的抗震设防目标设计的柱支承双向板及板柱节点,没有发生塑性铰,符合强节点的抗震设计原则。

Shear stresses caused by unbalanced moment at slab-column connection may result in diagonally cracking earlier in concrete core and consequently punching failure,which has great influences on ductility of the structure.Following the failure mechanism revealed by experiments,seismic performance objective is proposed for two way column-supported slab with respect to three seismic design target levels.The slab shall be designed to be not cracked in concrete core for small earthquake,to be elastic for moderate earthquake and to keep capability to transfer both vertical and horizontal forces for severe earthquake.The minimum slab thickness is required for that diagonal shear stress at the critical section shall be no more than characteristic tensile strength of concrete,ftk,during small earthquake.Shear compensation shall be included in ultimate state design of flexural strength,as the core is diagonally cracked during severe earthquake.A design illustration shows that slab-column connection,designed in accordance with the presented objectives,does not yield in push-over analysis.