Lateral force resisting mechanisms in slab-column connections: An analytical approach

In many countries reinforced concrete (RC) flat slabs supported on columns is one of the most commonly used structural systems for office and industrial buildings. To increase the lateral stiffness and strength of the structure, RC walls are typically added and carry the largest portion of the horizontal loads generated during earthquakes. While the slab-column system is typically not relevant with regard to the lateral stiffness and strength of the structure, each slab-column connection has to have the capacity to follow the seismically induced lateral displacements of the building while maintaining its capacity to transfer vertical loads from the slab to the columns. If this is not the case, brittle punching failure of the slab occurs and the deformation capacity of the entire building is limited by the deformation capacity of the slab-column connection. This article presents an analytical approach for predicting the moment resistance of all mechanisms that contribute to the strength of the slab-column connection when subjected to earthquake-induced drifts. The approach is based on the Critical Shear Crack Theory (CSCT). The performance of the model is verified comparing the analytical predictions with experiments from the literature. The influence of gravity induced loads on the flexural behaviour of slab-column connections under seismic loading as well as the contribution of the various resistance-providing mechanisms for increasing drifts are discussed.