Design Comparison Of Integrated And Discrete Super And Substructure Building Systems Under Seismic Loading

Abstract

With the availability of digital computers and Finite Element Analysis (FEA) programs, super and substructure modeling as a combined entity is not a difficult task. Accurate judgment of available capacity of structure and foundation require the integrated modeling of structure-foundation system. To make the structure economical and safe, it is necessary that the interaction between super and substructure should be taken into consideration in the engineering design. However, structural engineers even to date model the structure with fixed base, and there is no representation of the foundation and soil strata underneath. This research compares the performance of integrated structure foundation models and discrete models by using general purpose FEA program. Analysis and design of reinforced concrete moment resistant multistory frame buildings have been carried out by integrated and discrete modeling approach. Linear static and linear dynamic analyses are performed on the hypothetical building models with integrated individual, strip and raft footings. Response is compared with the corresponding discrete building models. Effect of pad thickness and soil spring stiffness is also studied. In integrated modeling; it is observed that the stress in the superstructure is increased. However, buildings when modeled with fixed supports result in reduction of stresses in the superstructure because fixity in this case is not actual response by the foundation. Result of integrated models show close similarity with discrete models when the pad thickness and the soil spring stiffness are increased