Mechanical Model for flexural behaviour of slab-column connections under seismically induced deformations

Reinforced concrete (RC) flat slabs supported on columns are one of the most widely used structural systems for office and industrial buildings. In regions of medium to high seismic risk RC walls are typically added as lateral force resisting system and to increase the lateral stiffness and strength. Although slab-column systems are not expected to contribute to the lateral resistance of the structure due to their low stiffness, the slab-column connection have to have the capacity to follow the seismically induced lateral displacements of the building while maintaining the capacity to transfer the vertical loads from the slab to the columns. Otherwise, brittle punching failure of the slab occurs and the deformation capacity of the entire building is limited by the deformation capacity of the connection. The present paper presents a model for predicting the flexural behaviour of slab-column connections without transverse reinforcement when subjected to earthquake-induced deformations, considering both the load and the deformation of the slab. The model is based on the Critical Shear Crack Theory (CSCT) and presents a rational approach for predicting the transferred moment-rotation relationship of slab-column connections as well as the contribution of all resistance-providing mechanisms respecting equilibrium principles in both local and global level. The model proved to be accurate enough when compared with tests (monotonic and cyclic) found in the literature.