Flexural behaviour of reinforced concrete slabs with generalized edge conditions

Abstract

Slab is the most widely used structural element. It is used almost in every type of structural system to build and/or enclose the space along with some other structural elements such as walls, columns etc. However, unlike other structural elements, a slab is highly redundant in nature due to the coupling of the internal stress resultants and consequently offers multiple load paths to the applied loading. Because of coupling of internal force-resultants, the structural behavior of the slabs is highly sensitive to the type, layout of the supporting system and/or stiffness of the supporting structural member(s). Any change in the physical parameters of the supporting systems will cause a considerable change in the moment-field induced in the slab under given loading conditions. The moment coefficients recommended by the design code [IS 456 (2000) and BS EN 1992-1 (1994)] are applicable only for the rectangular slabs with various end-restraints and supported over the non-yielding edges on the outer four edges. But in routine design practice, number of case are encountered by the designers whereby the beam-drop and the beam-spans are restricted by architects to a level that are not sufficient to provide a non-yielding edge at the outer boundary of the slab and as such, these coefficients predict the moment-field highly on the unsafe side and produce a structurally deficient slab section. In the present thesis, an analytical model has been developed for a rectangular slab-system resting over the non-yielding edges at its outer boundary and cast monolithic along with equally spaced internal shallow beams using the principle of the limit analysis. It can also be used for predicting the collapse load of skew slabs, design of multi-panel slabs but it must be supported over the equally spaced shallow beams along one direction and non-shallow beams at regular intervals along the other direction of the slab.