A Simplified Method of Analysis and Design of Reinforced Concrete Free- Standing Stairs

Abstract

Straight free standing staircases have come into fairly wide use now-a-days. Its attractiveness coupled with the elimination of obstructing columns under the landing which enables designers to maximize the utilization of the floor area have encouraged its use in many modern buildings. Its use, however, has been restricted due to the lack of an adequate & simple method of analysis. Fuchssteiner has proposed the simplification of the basic structure by substituting a space frame composed of linear bar elements, the frame consisting of two cantilever joined by a bow girder. Analysis of free standing stair has also been studied by A.C. Liebenberg, A.R. Cusens & J.G.Kuang, Sauter & A. Siev, et al. Analysis of free standing stair requires long and complex equations. The aim of present study is to develop a simplified method for analysis of free standing stair. Normally, free standing stair is an indeterminate to the six degree but in this study a simplification for symmetrical loading condition is made in such a way that it reduces to two degree of freedom. It is further assumed that torsional modulus by neglecting poisson’s ratio of the material & Ix/Iy(Ratio of moment of inertia about X axis & Y axis) is neglected due to stair slab width is very wide as compare to its thickness. Based on above assumption for a stair with equal flight subjected to symmetrical loading, displacement is calculated using virtual work method. Analysis and design of free standing stair is carried out using simplified method and A.Siev, W. Fuchssteiner and A.R. Cusens-J.G. Kuang. The comparison of simplified method with other methods is also presented. Design example is presented & structural detailing is provided.