Finite-element simulations of the punching tests on shear-retrofitted slab-column connections

A new type of shear reinforcement, shear bolts, are used for retrofit and strengthening of existing previously built concrete slabs to increase the punching capacity. The bolts are installed in holes drilled in a slab in concentric perimeters around the column. The test results showed a load increase up to flexural failure of the slabs and a significantly improved ductility when using shear bolts. The punching tests were investigated using the 3D nonlinear finite-element code MASA which was developed at the Institute of Construction Materials of the Universitaet Stuttgart. The paper discusses the modeling of slabs with shear reinforcement. A proper idealization of the shear reinforcement is essential for the accuracy of the finite-element simulations. The finite-element simulations show good agreement with the test results and give a more detailed insight in the failure mechanism. The models build the basis for an extensive parametric study on the punching behavior of flat slabs.