A Study On P-Δ Effects For Buildings With Varying Soft Storey Considering Soil Structure Interaction
In the conventional method of analysis, usually effect of secondary forces and effect of soil system on
foundation and super structure are generally ignored, which are likely to affect the performance of the structure. In the
present work, the P-Δ effects on soft storey buildings by considering effect of soil structure interaction have been studied.
For this purpose 3-D models of structure with soft storey are developed using ETABS® software. Soft storey levels are
varied based on relative position ratios (H/h), where ‘H’ is total height of the building and ‘h’ is height from the top most
edge of the building to the upper edge of the soft storey level. To account the effect of soil system, the soil underneath the
footing is for modelled by Winkler’s approach (spring model) in which hard, medium and soft soil are modelled as springs.
Equivalent static earthquake analysis is carried out. Models are analysed also by considering P-Δ effect. Results obtained
with and without P-Δ effect are compared in terms of roof displacement, storey drift and column moments. Results indicate a
substantial increase in response of the structure, when P-Δ effect is considered.
Keywords— Soft storey, Relative response ratio, P-Δ effect, Winkler modeling.