Estimation of Vs30 Bounds from Limited Soil Data Considering Uncertainty - A Practical Approach

Abstract

According to design standards, uncertainty of dynamic foundation parameters are accounted in soil structure interaction (SSI) analysis by considering best estimate, upper and lower bounds. Site specific variability (coefficient of variation: Cv) cannot be directly established from limited site measurements. Codes prescribe a value of unity for such cases, which results in wide and often unrealistic range of foundation parameters for SSI. A Monte Carlo (MC) simulation based approach is proposed for calculation of site specific Cv from limited measurements. Along with 12% reduction of mean value, Cv could be reduced to 0.5, thereby enabling reduction of the aforementioned range. Adoption of code specified minimum Cv could accommodate 50% inaccuracy of input shear wave velocity, which justifies use of correlation equations (with inaccuracies reported between 20% and 35%) for generation of synthetic shear wave velocity profiles as substitute for or augmentation of site measurements.