Nonlinear finite element analysis of non-symmetrical punching shear of rectangular flat slabs supported on square columns

Abstract

Different tests and calculation methods for determining the punching shear of flat slabs are based on symmetrical punching shear. However, in practical engineering, most flat slabs are not subjected to symmetrical punching shear due to the differences of two orthogonal directions in load, slabs reinforcement, column section size and slabs plane dimensions. The calibrated nonlinear finite element model (FEM) effectively expands the test database, performs variable parameter analysis, and verifies the calculation method. In this paper, the FEM of isolated slab-column connections is developed using ABAQUS and calibrated based on 14 test results from the literature. The simulation of punching behavior of 49 slab-column connections is carried out, the corresponding effects of the shear span ratio and the slab aspect ratio are evaluated. The results indicate that the shear span ratio and the slab aspect ratio significantly affect the crack development, reinforcement stress, stiffness, and punching shear strength. Furthermore, the slab aspect ratio influences the symmetry of the response. With the increase in the slab aspect ratio, the failure mode changes from symmetrical punching shear failure to non-symmetrical punching shear failure and flexural punching failure. The finite element analysis (FEA) prediction results of the ultimate load are compared with the calculation results of four equations of ACI, EC2, CSCT-simplified, and CSCT (ψX − ψY). The results confirm that the prediction using equations of CSCT (ψX − ψY) is reasonable, ACI method gives conservative results, whereas the safety factor of EC2 and CSCT-simplified is less than 1.0.