Effect of Soil Modelling on Structural Response

Abstract

The mechanical properties and characteristics of the ground on which the structure is based can remarkably influence the structural response. However, in current general design office practice, the effect of soil is neglected in structural modelling and response of structure is evaluated against an idealized structural model having a fixed or hinge base. But, in some cases, this effect may significantly modify the response of super-structure The present study aims to assess the effect of soil modelling by comparing the local and global responses of case study building models (with and without modelling the effects of foundation and local soil) under gravitational load analysis and seismic Analysis. For this we selected two case study buildings (4-Story Luxury Residence and 7-Story Commercial Building). These buildings are Frame Structures with RCC Walls to resist lateral loads and are representative of other buildings in our scope of work. Then we created models of selected buildings in ETABS. 3 different models for each building were created. 1. Baseline model (No foundation + No soil effect) 2. Model with actual geometry of foundations (No soil effect) 3. Model with actual geometry of foundations + Soil effect using modelling approach. For modelling soil, we used Winkler soil modelling Approach. For each model created, we preformed modal analysis, Gravitational load analysis and seismic analysis (ELF procedure). We extracted Global and local responses of every model of each building. When we compared these responses, we observed that the responses for both buildings, the base model results and plots differ significantly from either the foundation model, soil model or both. Hence, it can be safely concluded that the inclusion of foundation and soil modelling into the basic design approach is important to obtain a better and improved design.