Membrane Action in Orthotropically R.C. Rectangular Slabs Supported on Three Edges Only with Variable Axial Restraints


In this paper, large deformation analysis is carried out on uniformly loadedorthotropically reinforced concrete rectangular slabs that have one free edge anddifferent restraints on the other edges. For the purpose of such analysis, the slabsare assumed to behave in a rigid-perfectly plastic manner and to yield under thecombined effect of bending and membrane action. Two cases are analysed; thecase of a slab having two adjacent edges fixed- one edge simply supported and oneedge free, and the case of a slab having two adjacent edges simply supported- oneedge fixed and one edge free.Results of the analysis indicate considerable enhancements in the load carryingcapacity of such slabs above those predicted by Johanson's simple yield linetheory(1).The amount of the load enhancement in a particular slab is found todepend on many parameters such as the steel ratio rx+, orthotropy ratio g,compressive strength of concrete fʹc , yield stress of steel fy , and the slab aspectratio Ly/Lx, such that a higher enhancement in load is achieved for a slab having ahigher value of fʹc but lower values of Ly/Lx , rx+ , g and fy .