Behavior of Common-Base Multiple Seismically Isolated Buildings Under Near-Fault Earthquakes

DOI: 10.5176/2301-394X_ACE14.23

Authors: Hatice GAZİ, Cenk ALHAN, Muharrem SELEK

Abstract:

Seismic isolation is based on shifting the fundamental frequency of a structure out of the resonance range by means of isolation system elements enabling the structure to move flexibly in the lateral direction and meeting energy dissipation demands at the isolation level. A typical seismically isolated building has its own isolation system allowing the structure to move laterally within the boundaries of seismic gap around its own base-mat. Although this configuration is preferable, there may be cases where placing multiple buildings on a common isolation base-mat with a common seismic isolation system is unavoidable. It has been previously pointed out that in such cases, superstructures exhibit independent dynamic behaviors and dynamic interaction under earthquake loads, which may result in amplified seismic responses. However, the significance of this phenomena and thus the significance of comprehensive multiple-building modeling may vary depending on the earthquake characteristics. In particular, seismically isolated structures are known to be challenged by near-fault earthquakes. Additionally, noting the possible amplification in the seismic responses due to the dynamic interaction between the superstructures, the level of the success of seismic isolation in such cases also needs to be evaluated. Therefore in this study, (i) the significance of comprehensive multiple-building modeling of seismically isolated buildings with a common isolation base-mat and the significance of dynamic interaction between superstructures and (ii) the performances of seismically isolated multiple buildings with a common isolation base-mat in comparison to the performances of fixed-base buildings under bi-directional near-fault earthquake loadings are investigated. It is shown here that the significance of the comprehensive multiple-building modeling and dynamic interaction depends on the earthquake loading characteristics and on the response parameter in question and despite the possible response amplifications, a seismically isolated building placed on a common isolation base-mat still outperforms its fixed-base counterpart.

Keywords: Seismic isolation; Common isolation base-mat; Multiple buildings; Near-fault earthquakes