Abstract
Recent studies show that the effects of Soil Structure Interaction (SSI) may be detrimental to the seismic response of structure and neglecting SSI in analysis may lead to un-conservative design. Despite this, the conventional design procedure usually involves assumption of fixity at the base of foundation neglecting the flexibility of the foundation, the compressibility of soil mass and consequently the effect of foundation settlement on further redistribution of bending moment and shear force demands. The effects of SSI are analyzed for typical multi-story building resting on raft foundation. Three methods of analysis are used for seismic demands evaluation of the target moment resistant frame buildings: equivalent static load (ESL); response spectrum (RS) methods and nonlinear time history (TH) analysis with suit of nine time history records. Three-dimensional Finite Element (FE) model is constructed to analyze the effects of different soil conditions and number of stories on the vibration characteristics and seismic response demands of building structures. Numerical results obtained using soil structure interaction model conditions are compared to those corresponding to fixed-base support conditions. The peak responses of story shear, story moment, story displacement, story drift, moments at beam ends, as well as force of inner columns are analyzed.
Highlights
Over the past 40 years considerable progress has been made in understanding the nature of earthquakes and how they damage structures, and in improving the seismic performance of the built environment
This study aims to study the soil-structure-interaction for multi-story buildings on raft foundation; evaluate the approach of Egyptian Code seismic provisions for analysis methods during the seismic design of buildings; to discuss the alternative solutions for cases wherein existing provisions do not lead to satisfactory results and to quantify the effect soil-structure interaction (SSI) on the structural response so that designers can be aware of the likely impact of their decisions
The study as a whole may prove useful in formulating design guidelines for seismic design of building frames incorporating the effect of soil-flexibility
Summary
Over the past 40 years considerable progress has been made in understanding the nature of earthquakes and how they damage structures, and in improving the seismic performance of the built environment. During past and recent earthquakes, it is realized that the soil-structure interaction (SSI) effects play an important role in determining the behavior of building structures. This study aims to study the soil-structure-interaction for multi-story buildings on raft foundation; evaluate the approach of Egyptian Code seismic provisions for analysis methods during the seismic design of buildings; to discuss the alternative solutions for cases wherein existing provisions do not lead to satisfactory results and to quantify the effect SSI on the structural response so that designers can be aware of the likely impact of their decisions. A parametric study with different approaches of analysis methods; design parameters of the underneath soil condition and number of stories is carried out to evaluate on the building vibration characteristics and seismic demands including the fundamental period, total base shear, story displacements, story drifts, moment at beams ends and force of inner columns. The results show that SSI has a significant influence on the seismic response demands
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