FINITE ELEMENT ANALYSIS OF SLABLESS TREAD RISER STAIRS

Abstract

The Slabless tread riser stairs,'due to their application in the construction of modern commercial and residential building, has had a wide acceptance. The construction of some stairwayt this type with approximately plane orthopolygonal axes, has generated the interest of many architects and engineert. In this dissertatton, the Finite ElementAethod has been used to analyse the Slabless tread riser stairs with extraordinary architectural possibilities. The Slabless tread riser stairs has been analysed by the finite eleMent method to study the state of strest.in the structure for different parametric cases. 7 The problem has been analysed as a two dimensional, plane strain case using the parabolic quadrilateral isoparametric .element f serendipity family. This study showt the presence of axial stresses, horizontal displacement§ which are completely being ignored in coventional study. This study also thoWt that 'the fixed end moments are less than those obtained froM conventional: methods and vertical reactions are unequal at two ends contrary to conventional method of analysit. The variation of axial force, thear force. and bending moments are plotted. The resultt for BM are compared with the conventional analysis. TheJT software named PSPSAS has been used for finite element analysis that runs_ on HP . Syttem 9000 series in UNIX. Pre-proce§sor has: the capability of automatic generation of. FE. meshet and.pott processor offers graphic modules to interpret the analysis results. Post processor can produce methet, deformed shape, stress vector; stress contours and stress resultant variations. At the junction of tread and riser, a detailed stress distribution is obtained by finite element analysis. In addition to these, conventional analysis of these stairs is performed for three different support condition cases and the present analysis technique has been critically examined. A modified analysis method is also suggested to incorporate the effect axial deformation whiCh introduces the horizontal thrust. The detailed analysis thus reveals'that the stairs are folded plate like structure and membrane action causes tens.lon. The horizontal displacement of structure plays a vital role in its . structural behaviour.