Seismic vulnerability of flat plate column joint

A brittle punching shear failure can arise in flat plate-column connections during an earthquake because of poor transfer capacity of shearing forces and unbalanced moments. To increase the shear capacity of the slab therefore, various types of shear reinforcement are used around such connections. This paper presents the response of slab column connections containing various types of slab shear reinforcement when subjected to combined gravity and cyclic lateral loading predicted by a Finite Element analysis program MASA. First, a calibration model was developed in MASA to simulate the tested flat plate-column joint. Then, finite element models of a flat plate-column joint with various types of slab shear reinforcement were developed. The presence of shear reinforcement significantly improves ductility, energy dissipation and drift capacity of the connection under the applied lateral cyclic loading. As a result, slab shear reinforcement, in the form of lacing bars is proposed in this paper. The simplicity of placement of this type reinforcement makes it an attractive alternative to single-leg and stud shear reinforcement.