Pre-cast Concrete Slab/Column Joints: Experiments and Design Models

The applications of pre-cast concrete in flat-slabs are mainly controlled by the construction joint between the slab elements and columns in order to satisfy monolithic action. This paper introduces a conceptual approach for the construction detail of such joints. An experimental program was conducted for testing the joints between two pre-cast cantilever slabs and a rectangular column. At the cast-in-situ joints, the slabs' and columns' loop reinforcement were arranged in a staggered overlapped manner. The tested specimens were loaded asymmetrically under bending, in order to study the moment transfer efficiency and the rotational stiffness of the joint from zero load up to failure. Several variables were studied; the slab reinforcement ratio and distribution, the curvature shape of the column loop reinforcement and the arrangement of shear studs. The behaviour of those construction joints was compared to that of ordinary monolithic flat slab/column joint to evaluate cracking and deformational behaviour at service as well as their ultimate capacities. Additionally, the structural behaviour of those joints was discussed using Strut and Tie Method (STM). Design Models using STM are introduced, which can be adopted in the design of such joints.