Abstract
The present study is aimed at determining the effect of variability in soil type and structure height on soil-structure system responses. In order to explore this innovative idea, a wide range of soil types and structure heights are assumed, and the responses are analyzed with respect to changes in soil type and structure height. It is intended to address the three-fold problem of determining under what circumstances soil-structure interaction (SSI) exerts significant effects on the results, on what condition it could be ignored, and whether taking account of SSI leads to conservative results. To verify the numerical models, the results are compared with those derived from the NEHRP method. Five planar concrete frames are examined under the action of thirty earthquake records. Seven types of soil are considered. For modeling the soil-structure system, the direct method is employed. The plastic behavior of the soil is formulated based on the multi-surface (nested surfaces) concept; the yield surfaces of sand are of the Drucker-Prager type, and those of clay are of the Von Mises type. The exact Incremental Dynamic Analysis (IDA) is adopted for analyzing the soil-structure system. The results indicate that, for sandy soils, the SSI impact is greater for looser sub-soils. For clayey soils, the medium clay has the most powerful SSI effect. For low and medium rise buildings, the SSI effect is more profound as the structure becomes taller, but for high rise buildings, the SSI effect wears off with increasing height.
Highlights
Seismic waves travel mainly through rock in their course to the ground surface, the last portion of that propagation is often through soil, and the characteristics of the soil can greatly influence the nature of shaking at the ground surface [1]
It is obvious that the most dramatic effect of soil-structure interaction (SSI) is produced for medium rise structures. in the case of very tall buildings, drift lengthening caused by SSI approaches zero, meaning that, for such buildings, considering SSI doesn’t affect the drift of the structure
Seven soil types and five frames are considered in order to investigate the seismic behavior of various soil-structure systems. the innovative idea explored in the present paper is to consider a wide range of soil types and structure heights for examining the structural response trend under the effect of the changes in soil type and structure height. the base and roof displacements and the pushover and Incremental Dynamic Analysis (IDA) curves of each soil-structure system are derived and evaluated. a comparison was made between the responses of the soil in the time and frequency domains
Summary
Seismic waves travel mainly through rock in their course to the ground surface, the last portion of that propagation is often through soil, and the characteristics of the soil can greatly influence the nature of shaking at the ground surface [1]. Chopra and Yim [7], modeled the behavior of shallow foundations using Winkler springs They concluded that taking the SSI effect into account causes a reduction in the moment demand of the structures. All of them have argued for the strong effect of SSI on the behavior of structures, but arrived at different conclusions about the variations in the structural behavior These investigations fail to provide any conclusive evidence on the way the structural responses are affected by the soil type. This discrepancy in the conclusions is very likely due to the fact that the structures and soil types studied were all different. The 2D nonlinear analytical models of soil-structure systems were developed for the nonlinear dynamic analysis with OpenSEES software [27]
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