Software for Analysis and Design of Flat Slab

Abstract

Girder less floor directly resting on support (column and/ wall) is known as flat slab. Because of this, large bending moment and shear force is developed at / near the column head hence there is a need to increase the area at top of column to withstand the stresses. This enlarged truncated portion at the top of column is known as column head/ column capital.

Flat slabs are subjected to gravity and lateral loads. Gravity load analysis of flat slab is carried out by Direct Design Method (DDM) and Equivalent Frame Method (EFM) as prescribed by different standards, however three dimensional finite element analysis of flat slab is carried out for gravity and lateral loads using software SAFE.

I.S.456-2000, ACI 318-02 prescribed the fixed coefficients for analysis of flat slab as per DDM. Three dimensional analysis of flat slab is carried out to compare the coefficients prescribed by different standards and by three dimensional finite element analysis using software for distribution of moments along longitudinal and transverse direction, when it is subjected to gravity and lateral loading.

Slab is divided into column strip and middle strip. I.S.456-2000 specifies the fixed value of column strip and middle strip irrespective of interior span and mid span, the present study also incorporates the comparison of distribution of width of column strip and middle strip as per I.S. 456 and as per 3D finite element analysis.

Software is prepared for analysis and design of flat slab as per DDM and EFM. DDM includes analysis as per I.S.456, ACI-318 and using the distribution coefficients along longitudinal and transverse direction calculated by the 3D analysis.

From the analysis results it is found that the distribution of negative moment at support is more as compared to distribution prescribed by I.S.456 and ACI 318 and B.S.8110, also it is observed that the width of column strip in end span is smaller than the interior span.