Punching shear behavior of reinforced concrete slabs using steel fibers in the mix

Abstract

One of the major problems of flat slab is the punching shear failure of slab-column connection. This form of failure must be avoided.Fourteen slab-column connections are tested to failure and categorized in two phases. The first “Phase I” consisted of testing ten interior square slabs axially loaded. The second “Phase II” consisted of testing four specimens under eccentric loading to study the influence of moment transfer at the slab-column connection on the punching shear failure of the slabs. The main parameters evaluated were, fiber volume ratio which was 0.5%, 1.0% and 1.5% and, punching area as dimensions of the square portion of the slab having steel fibers at the column vicinity of lengths d + 200 mm, 2d + 200 mm and 3d + 200 mm. All slabs have same dimensions of 1700 mm × 1700 mm with thickness 150 mm and reinforcement ratio of 1.2%. All tested specimens were loaded incrementally up to failure. However using steel fiber increased both the failure load and energy absorbing capacity. Summarily, it was found that slabs with a 1.5% steel fiber ratio led to high failure load capacity. Results showed that using steel fiber only in a portion of slab that is equal to slab thickness from column face was sufficient to give the optimum enhancement in both failure load and ductility behavior. Three-dimensional finite element model was created to using ANSYS R14.5 ANSYS (2012) program to simulate the behavior of the tested specimens. Crack pattern, mode of failure and energy absorption were analyzed here in this study. Keywords: Flat slab, Steel fiber, Punching shear, Failure load