Abstract
Soil conditions have a great deal to do with damage to structures during earthquakes. Hence the investigation on the energy transfer mechanism from soils to buildings during earthquakes is critical for the seismic design of multi-story buildings and for upgrading existing structures. Thus, the need for research into soil–structure interaction (SSI) problems is greater than ever. Moreover, recent studies show that the effects of 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 the underneath soil and, consequently, the effect of foundation settlement on further redistribution of bending moment and shear force demands. Hence the SSI analysis of multi-story buildings is the main focus of this research; 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; response spectrum methods and nonlinear time history analysis with suit of nine time history records. Three-dimensional FE model is constructed to investigate 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 SSI model with different soil conditions are compared to those corresponding to fixed-base support modeling assumption. 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. The results of different analysis approaches are used to evaluate the advantages, limitations, and ease of application of each approach for seismic analysis.
Highlights
Over the past 40 years, considerable progress has been made in understanding the nature of earthquakes and how they could cause structure damages, and in improving the seismic performance of the built environment
The results show that soil–structure interaction (SSI) has a significant influence on the seismic response demands
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 could cause structure damages, and in improving the seismic performance of the built environment. A parametric study with different approaches of analysis, design parameters of the underneath soil conditions and number of stories is carried out to evaluate the SSI effects 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 seismicity especially at the zones of high activity is investigated and the soil condition, soil amplification, soil structure interaction, liquefaction and seismic hazard are carried out, in particular, the urbanized areas All these parameters are integrated to obtain the Egyptian building code which is valid to construct buildings resist damages and, mitigate the earthquake disasters. Utilization of the findings of these research efforts in national and international design codes and in routine design calculations is still very rare if not absent
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