OPTIMUM DESIGN, OF REINFORCED CONCRETE SLABS

Abstract

The most popular and widely used flooring system presen-tly in practice consists of reinforced concrete slabs. These are used in reinforced concrete framed construction as well as with load bearing walls. Even where brick or stone masonry walls are used it is more preferred to construct the slab of reinforced concrete. Also a major portion of the construction cost goes into the slab. Hence it is most desirable that an optimum design solu-tion be found for the design of most commonly used reinforced conc-rete rectangular slabs. The present study is a. stepin that direction. It is aimed at facilitating the designer in selecting the optimum conc-rete section and reinforcement arrangement which would lead to minimum cost. Yield line analysis of slabs coupled with results of elastic analysis have been used to analyse and modify slab design such as to arrive at an optimal solution. The limit state method of design as per IS 456-1978 is used. Together with the results thus obtained is given for comparision the results using the (IS 456-1978) Code method. Separate design tables are given for the slabs having a short span ranging from 2.50 to 4.50 metres, span ratios varying between 1 and 2. The generally used grades of concrete (Ml) and steel (Fe-415) are adopted for this study and the loading class taken are 200, 300 and 500 from IS 875-1964. Also all the nine different cases of edge conditions given in Table 22 of IS 456~-1978 are covered. The study, hence gives design of a wide variety of rectangular slabs covering most of the cases enco1in:'"-er~d in the field. The design tables in the present work are prepared on the basis of numerical results by developing a computer .program for optimal analysis and design of slabs and running the same on the central digital computer facility, DEC 2050, located in the Roorkee University campus.. It is hoped that the present study will facilitate the optimum design of slabs in the minimum time and effort.