Effect of Floor Rigidity on Contact Stress and Differential Settlement

This paper presents the effect of soil, foundation, and superstructure interaction on the contact stress and differential settlement. In recent design, designers have tried to resist the differential settlement by tie beams that connect the foundations. It is a complicated problem to calculate the differential settlement under the foundations taking into consideration the effect of the soil structure interaction. In addition, design of the tie beams that can resist the differential settlement by rigidity only result in a huge beam section with a huge reinforcement. Usually the tie beams are constructed as flexible rigidity due to the thickness-length ratio. Therefore, the tie beams cannot resist the differential settlement alone, and the superstructure members also shall work together with the tie beams. This paper presents the effect of the superstructure floor only without tie beams on the contact stress and differential settlement. Floor rigidity has a significant effect on the contact stress that increases the outer footing contact stress and decreases the contact stress under inner footing. This interaction leads to dampen the differential settlement under foundations. The floor rigidity affects the differential settlement, and the differential settlement affects the straining actions acting on the floor. In addition, the straining actions affect the design of the floor sections that affect the floor rigidity. This closed form solution still is in need of more research to simplify the solution. Curerntly it can be solved usinggeotechnical finite element (FE) programs that can simulate the superstructure members. Therefore, calculation of the secondary stresses on the floors concerning differential settlement calculated without soil structure interaction is wrong.