Two diffirent approaches are generally used for the desing of reinforced concrete structures. In one of these approaches, the columns at the base are considered as fixed with the assumption of the foundation stratum to be rigid neglecting the soil effect which exposes to the stresses transferred from the superstructure and which creates the reaction against these stresses. Soil effects are only taken into account in the design of foundation. It can be said that design of the superstructure without considering the soil effects will be incomplete. In the other approach, the soil-structure interaction is incorporated using Winkler model in which soil tratum is represented by infinitely close springs. However, in the Winkler model, which is the simplest of the foundation models, the interaction between the springs are ignored and therefore the shear deformation of the subsoil is neglected. Whereas, accurate and realistic representation of the soil-structure interaction is crucial for a reliable desing of an engineering structure. In this study, the effect of soil-structure interaction on the design of reinforced concrete structures is investigated by using the Modified Vlasov model which is described as a more realistic subsoil model in the literature. For this purpose, a solution technique has been developed by using SAP2000 software and a computer program coded in MATLAB simultaneously.
The soil model used in the soil structure interaction and especially the developed Modified Vlasov model used in this study are summarized and then the developed solution technique is explained in detail and the flow diagram is presented. In order to demonstrate the performance of the technique used, a raft foundation exapmle from the literature is studied. Then; the effects of soil models, soil properties, earthquake zone and number of floors on the results are investigated. Natural vibration periods, column axial forces, column bending moments and longitudinal reinforcement ratios of the columns is compared for each subsoil model. At the end of the study, it is seen that the effect of the soil-structure interaction on the design of reinforced concrete structures has an significant role that can not be neglected.
Key Words: Soil-structure interection, OAPI, Elastic foundation, Design of reinforced concrete structures, Sap 2000