Equivalent linear computation of response spectra for liquefiable sites: The spectral interpolation method: Fid-Bau Portal

Equivalent linear computation of response spectra for liquefiable sites: The spectral interpolation method

Tsiapas, Yannis Z. / Bouckovalas, George D.

Abstract A simplified methodology is presented for the computation of elastic response spectra at liquefiable sites, based on the widely used equivalent linear site response analysis method. The target response spectrum is obtained by frequency dependent interpolation between the response spectra for “non-liquefied” and for “liquefied” ground, the former computed for the native soil properties, without excess pore pressure buildup, and the latter for the properties of the liquefied soil. Apart from the structural frequency, the interpolation coefficient is also related to the factor of safety against liquefaction. In this way, the proposed methodology takes indirectly into account the initial segment of the seismic excitation time-history, until the onset of liquefaction, which is of cornerstone importance for the overall ground response at sites with low and moderate liquefaction potential. Results of parametric nonlinear numerical analyses and three field case studies are used to calibrate the methodology and evaluate its accuracy. In addition, the potential of the proposed methodology for defining code-oriented design spectra for liquefiable sites is examined.

Highlights • A simplified method is presented for the response spectra computation of liquefiable sites. • The method is based on interpolation, between the spectra for non-liquefied and for liquefied sites. • The interpolation scheme is related to structural frequency and liquefaction factor of safety FS L. • Potential amplification effects due to pre-liquefaction shaking are consistently accounted for. • As a proof of concept, the method is used to define code-oriented design spectra for liquefiable sites.