The ultimate strength and long-term behaviour of uniformly loaded, two-way concrete slabs with partial lateral restraint at all edges

Abstract

Summary A theory for the ultimate flexural strength of uniformly loaded, laterally restrained two-way concrete slabs (reinforced or unreinforced) is extended to include the effect on the compressive membrane action of partial restraint against lateral displacement at all the edges and axial strains in the plane of the slab. The edges of the slab are considered to be fixed against rotation and vertical translation, and a strip approximation is used with an empirical value for the deflexion at ultimate load. The theory is applicable to the interior panels of slab-and-beam floors under short-term or sustained uniform loading. It is shown that partial lateral restraint and axial strains can reduce the compressive membrane action significantly, especially in the case of thin slabs. The theory is compared with the results obtained from eight unreinforced slabs tested under sustained uniform loading and is shown to give a conservative indication of the ultimate flexural strength in most cases.