Acceleration - displacement response spectra (ADRS) for design of seismic isolation systems in Turkey

Abstract

Nonlinear Response History Analyses (NLRHA) have been frequently used in seismic isolation system design since the displacement at long period end of the codebased spectra is limited to a certain value and may not accommodate larger displacement demands. The NLRHA is a practical tool to determine the maximum displacement of the system based on prede ned values of e ective period, e ective damping and base shear transmitted to superstructure which are internally connected and requires an iterative process. In order to reduce the process, the methodology which is called as Acceleration-displacement response spectra (ADRS) approach is proposed by Whittaker and Jones (2013, 2014). In this study, ADRS approach is extended considering the new Turkish Building Seismic Design Code (TBSDC, 2018) that will come into force in 2018. Series of nonlinear response history analyses are performed for several isolation system parameters and seismic hazard levels. Displacement spectra are obtained by using bi-linear hysteresis curve model. E ective and robust ADRS graphs which facilitate the preliminary design stage of the seismic isolation systems are obtained in terms of acceleration and displacement demands of earthquakes. The e ects of di erences in fundamental seismic isolation system parameters and ground motion selection criteria on the preliminary design of seismic isolation systems are examined and represented in graphical forms. ADRS graphs provide the base shear and displacement limits of seismic isolation systems in the region under maximum considered earthquake (DD1) and design basis earthquake (DD2) design levels. Shaking levels are obtained from New Probabilistic Seismic Hazard Map of Turkey (TDTH, 2016). The design spectra composition is formed using two site categories (NEHRP C and NEHRP D) and two hazard zones (high and moderate hazard) at each design level. For each design spectra, eleven horizontal ground motion pairs are selected and linearly scaled using the geomean spectral ordinates. Analyses are performed using a combination of eight site-speci c design spectra in total, six e ective isolation system periods and ve yield levels. Evaluation and discussion of the ADRS graphs are provided to develop an overall understanding about the base shear and displacement limits of a seismic isolation systems in the region.