Developing the Mechanical Model of Muttoni to Predict the Rotational Capacity of Flat Slabs

Applying gravity loads on unequal spans, or lateral loads usually produce moment transfer between slab and column. The moment increases the shear stress of concrete in the vicinity of columns and reduces the punching capacity of slab. In the cases in which the estimation of unbalanced moment is laborious or when the ductility of slab-column connection is assessed, it is suggested to control the rotational capacity of connection instead of its unbalanced moment capacity. Existing mechanical models, except the Broms [1] model, are not able to predict the rotational capacity of the connections. The mechanical model of Muttoni [2] which was proposed for the estimation of punching capacity of centrically loaded slabs is developed to calculate the rotational capacity of the connection. The effect of eccentricity of loads on the ultimate punching resistance of slabs, and the rotational capacity of slabs with respect to column, is studied numerically performing non-linear finite element analyses using ATENA. Three experimentally tested slab-column connections by Krueger [3, 4] are selected for simulation and verifying the numerical models. The results of the analyses are compared with ACI [5] and EC2 [6] codes predictions and with the mechanical model of Broms [1] and the developed model of Muttoni. The rotational capacities predicted by the developed model are in better agreement with the test or analyses results in comparing with same values calculated by Broms [1] model.