Importance of Implied Strength Correction for 1D Site Response at Shallow Sites at a Moderate to Low Seismicity Region

Abstract

Hyperbolic type nonlinear models used in 1D site response analysis are reported to predict favorably the nonlinear soil response at small strains, but may provide poor fits at large strains. It has been shown to result in unrealistic site response for deep and soft sites particularly in regions of high seismicity, where implied strength correction is demonstrated to be important. In this study, the importance of the implied strength correction for shallow sites at a region of moderate to low seismicity is investigated. This paper uses a quadratic/hyperbolic model that can capture the stress-strain response at large strains in addition to the small strain stiffness dependence. A total of fifteen measured site profiles are used and a suite of 1D site response analyses are performed using a range of input motions. The strength correction is shown to be relevant even for shallow sites and moderate intensity ground motions. The difference between non-corrected and corrected analyses is conditional on the site period. The overall difference is demonstrated to be more prominent in soft sites. A quantitative estimate of the difference between two types of analyses is presented.