Abstract
The present paper investigates the coupled effect of the supporting soil flexibility and pounding between neighbouring, insufficiently separated equal height buildings under earthquake excitation. Two adjacent three-storey structures, modelled as inelastic lumped mass systems with different structural characteristics, have been considered in the study. The models have been excited using a suit of ground motions with different peak ground accelerations and recorded at different soil types. A nonlinear viscoelastic pounding force model has been employed in order to effectively capture impact forces during collisions. Spring-dashpot elements have been incorporated to simulate the horizontal and rotational movements of the supporting soil. The results of the numerical simulations, in the form of the structural nonlinear responses as well as the time-histories of energy dissipated during pounding-involved vibrations, are presented in the paper. In addition, the variation in storeys peak responses and peak dissipated energies for different gap sizes are also shown and comparisons are made with the results obtained for colliding buildings with fixed-base supports. Observations regarding the incorporation of the soil-structure interaction and its effect on the responses obtained are discussed. The results of the study indicate that the soil-structure interaction significantly influences the pounding-involved responses of equal height buildings during earthquakes, especially the response of the lighter and more flexible structure. It has been found that the soil flexibility decreases storey peak displacements, peak impact forces and peak energies dissipated during vibrations, whereas it usually leads to the increases in the peak accelerations at each storey level.
Highlights
In conventional design, buildings are generally considered to be fixed at their bases
The results show an increase in the peak displacement up to a certain maximum level, which is followed by a decrease trend to a certain minimum value and peak values are kept constant for wider gap sizes
The results indicate that the consideration of base soil flexibility results in nearly constant values of peak energy dissipated by yielding for different seismic gaps
Summary
Buildings are generally considered to be fixed at their bases. The assumption of fixed-base supports has been proved to be valid only for structures founded on rock or soil of high stiffness. Flexibility of supporting soil medium results in movements of the foundation leading to the decrease in global stiffness of a structural system (Wakabayashi 1985; Wolf 1987; Stewart et al 1999a). Soil-structure interaction (SSI) has captured the interest of many researchers who studied the issues concerning the applications of SSI to buildings through analytical and empirical procedures (see, for example, Stewart et al 1999a,b; Bhattacharya et al 2004; Fariborz and Ali 2012; Halabian and Erfani 2013; Spyrakos et al 2009a,b; Dutta and Rana 2010). The use of energy concepts in the analysis of structures subjected to earthquake motions in the time domain and frequency domain was investigated in several studies (see, Austin and Lin 2004; Takewaki and Fujita 2009; Yamamoto et al 2011)
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