Analysis and Design of Flat Slabs using Various Codes

"Flat Slab" is better understood as the slab without beams directly resting the slab on the column and load from the slab is directly transferred to the columns. To support heavy loads the thickness of slab near the support with the column is increased and these are called drops and that large bending moment &shear forces are developed close to the column. These stresses brings about the cracks in concrete & may produce the failure of slab, thus there is a need to provide a larger area at the top of column called as column head/ capital. Absence of beam gives a plain ceiling, thus giving better architectural appearance and also less vulnerability in case of fire than in usual cases where beams are used. Plain ceiling diffuses light better, easier to construct and requires cheaper form work. As per local conditions and availability of materials different countries have adopted different methods for design of flat slabs and given their guidelines in their respective codes. The aim of this project is to try and illustrate the methods used for flat slab design using ACI -318, Eurocode2 and IS: 456 design codes.For carrying out this project an interior panel of a flat slab with dimensions 6.6 m x 5.6 m and super imposed load 7.75 KN / m2 was designed using the codes given above. A flat slab consists of a reinforced concrete slab that is directly supported by concrete columns without the use of intermediate beams. C.A.P. Turner constructed flat slabs in U.S.A. in 1906 mainly using intuitive and conceptual ideas, which was start of this type of construction. Many slabs were load-tested between 1910- 20 in U.S.A. It was only in 1914 that Nicholas proposed a method of analysis of flat slabs based on simple statics. This method is used even today for the design of flat slabs and flat plates and is known as the direct design method. Structural engineers commonly use the equivalent frame method with equivalent beams such as the one proposed by Jacob S. Grossman in practical engineering for the analysis of flat plate structures. Floor systems consisting of flat slabs are very popular in countries where cast-in place construction is predominant form of construction because of many advantages in terms of architectural flexibility, use of space, easier formwork, and shorter construction time. Flat slabs are being used mainly in office buildings due to reduced formwork cost, fast excavation, and easy installation.