Effect of non-uniform height of building on mat design

Abstract

The present study was carried out to investigate the effect of subgrade modulus and mat thickness on design of mat foundation. The Mat of beam-slab system and uniform thickness system were analyzed with loads from 25 story reinforced concrete building with uniform and non-uniform height. The mat subjected to gravity load was modeled in SAFE 12. The edges of mat were restrained by roller support. That means the mat was restrained in all edges horizontally. Vertically there was soil support under the mat. A comparative study has been made among some critical positions of the mat foundation in order to perceive the influence of soil subgrade modulus and mat thickness on mat design. Effect of Subgrade modulus was found as (i) The value of negative bending moments (midpoint of panel) decreases with soil subgrade modulus, and positive bending moments (beneath of columns) increases with soil subgrade modulus for all cases; (ii) Mat deflection decreases exponentially with increasing modulus of sub-grade reaction at all positions; and (iii) At positions beneath the columns, the contact pressure increases with increase of subgrade modulus. Effect of mat thickness was found as (i) The value of shear (both positive and negative) increases with the increase of mat thickness for all cases. But the change is not significant; (ii) The value of negative moment (mid panel) increases with the increase of mat thickness. The positive moments (under column) decreases with mat thickness; (iii) At all points deflection increases with the increase of mat thickness. However, differential settlement decreases with the increase of mat thickness; and (iv) The value of contact pressure increases with the increase of mat thickness for all cases.