Shear stress distribution of flat-plate using Finite Element Analysis

Abstract

ABSTRACT The development of a linear numerical model of flat-plate to predict shear stress distribution around slab column connection is presented in this paper. An attempt is made to model the slab, flexural reinforcement and shear reinforcement using three dimensional solid elements. The proposed finite element model has been proved to be capable of simulating the shear behavior of slab-column connection and to be suitable for analysis of structural performance of flat plate structures. Numerical results obtained from this model have good agreement with the available results of other researcher’s numerical model with one dimensional rebar element. Keywords: Flat plate, ABAQUS, shear reinforcement, slab-column connection. 1. Introduction Flat-plate slab system is widely adopted by engineers as it provides many advantages such as reduction of floor height, more spatial planning due to no beams present. These advantages further results in reduction in material cost. In the flat plate slab-column connection is always subjected to combination of high bending moments and shear stresses, which develop a punching, shear failure. This failure is undesirable as it occurs without warning and may lead to progressive collapse of slab. Due to large tensile stresses, the potential diagonal crack in the form of truncated cone or pyramid is formed around the column. The failure surface extends from bottom of the slab at the support, diagonally upward up to the top surface. The angle of inclination with the horizontal depends on slab reinforcement. Hence, designing of flat-plate requires a special attention for both strength and ductility when punching shear being consider. The punching shear capacity of the slab-column connection is affected by the size of the column, the depth of slab, flexural reinforcement and compressive strength of slab etc. The punching shear capacity can be increased by using a larger column diameter, larger effective depth, more flexural reinforcement, higher concrete compressive strength or by shear reinforcement. Among these methods, the most effective way to enhance the slab-column connection is to use shear reinforcement at the punching shear zone (ACI 421 R-99), which is permitted by most of the building codes. The provision of punching shear reinforcement in various forms help in increasing the shear and ductility of the concrete. The various forms of shear reinforcements include stirrups, shear studs, bend up bars, shear heads (placed above the column), etc. According to ACI 318-05, the shear strength is a function of compressive strength of concrete and geometrical condition. The provision given in EC2 also includes the size effect and the effect of the flexural reinforcement ratio. Allowable shear strength of concrete with shear reinforcement is calculated as 0.125 √f