Effect of differential settlement on seismic response of building structures

Abstract

Differential settlement of footings of reinforced-concrete buildings is expected to have a considerable effect on design forces in various structural components depending on the characteristics of the soil. The differential settlement combined with the soil–structure interaction (SSI) effect during earthquakes may be a significant factor in deciding the structural response especially for structures that have already undergone differential settlement. This is generally ignored in conventional design practice. A four-storeyed building structure is considered for the study. A typical layered soil profile similar to the profile observed in the Ganges basin, India has been considered for investigation. The SSI effect under dynamic conditions has been considered by adopting Gazetas springs at the support of buildings. Twelve earthquake time histories have been considered for bedrock motion. Convoluted bedrock motions considering the soil profile have been adopted as the input motion for the structure. Effects of various earthquake parameters on the seismic response of buildings, considering the differential settlement and the SSI effect under dynamic conditions, have been investigated and presented in dimensionless terms. The results indicate that the differential settlements along with the SSI consideration may be critical in deciding the structural response. This may even render the structure unsafe during earthquakes.