COMPARATIVE STUDY OF FLOORS AND ROOFS FOR POLYGONAL PLANS

Abstract

The form of building is caused by functional, behavioral, economical and aesthetically enclosed spaces and by the shapes of its solid components (walls, floors, etc.). Most interesting to the field of construction are polygons, with or without opening, which can accommodate larger space without disturbance and are open in the character. Increasing use of polygonal shapes by architects necessitates the use of a rational method for their design. It is, therefore, propbsed to investigate this problem by the more accurate method "Finite Element Analysis" and come out with design aids for the use of the profession. The objective of the work is to develop design aids in the form of tables of maximum bending moment coefficients for design of regular pentagonal, hexagonal, and octagonal shaped plates with or without openings for different edge support conditions. Commercially available finite element computer software has been used. The tables of design bending moment coefficients for simply supported regular pentagonal, hexagonal, and octagonal plates have been developed. The magnitude of negative bending moment coefficients are reduced by providing beams on the edges. The size of edge beams has been varied to find its effect on the moment in the slabs. The width to depth ratio has been kept constant as 0.7. In computing the flexural rigidity of the edge beam, the effect of interacting effective flange width has been considered. Openings are some times unavoidable for functional needs. In this study the effect of centrally located openings have been considered. Regular polygons of sizes 3, 4.5 and 6 meters with centrally located openings of 5% and 7.5% of the area of iii the respective polygon with edge beams all along the opening sides have been analyzed. Further, bending moment coefficients have also been given for a concentrated loads of 1kN acting on all the opening corners to facilitate design of the slab for skylight loads if any. An effort has been made to analysis the sloping polygonal roof slabs with slope 10° and 20°. Stresses and bending moments are tabulated and it is found that bending moments are significantly lower than that in the solid slab of the same size as load is transferred primarily by inplane action as the slope increases. Lastly the general design guidelines have been given for the design and the detailing of the polygonal floor slabs.