Effect of Soil Flexibility on Building Frame Analysis and Practice in Bangladesh

Abstract

To analyze and design multi-story building frames, it is a conventional practice that the foundation is fixed but in actuality, the structure is ultimately supported on soil that has a flexible characteristic. Typically, during the design of the structure, the impact of soil-structure interaction (SSI) is disregarded in Bangladesh. This soil's flexibility may vary according to its characteristics of settling loads, variations in the soil strata below the foundation, etc. When earthquake loads come, the soil's flexibility causes at varying rates, which influences the design and distribution of the structural forces. The current study makes an effort to acknowledge the effect of soil flexibility on the analysis and design of moment frame building, especially for earthquake load. To conduct this study, structures are modeled using two different approaches: (A) frame without soil effect and (B) frame with SSI into account. With the aid of the ETABS program, 6-storied, 9-storied & 12-storied RCC special moment frame building located in seismic zone IV as per BNBC20 is analyzed for different approaches. To assess the influence of various characteristics on the behavior of the structure, parametric studies are carried out. The system's natural periods are increased due to the soil's flexibility, which reduces the total stiffness of the building frames under the foundation. Also, according to the study, the soil's flexibility affected the structural stresses and impacted the structural analysis, which must be considered in the design.