Evaluating the Effect of Uncertainty of Soil Parameters in the Modeling of Soil-Structure Interaction on the Collapse Responses of the Structure

In current research, structure collapse of fourstore concrete bending frame on sand soil was considered with noting uncertainty of soil parameters. The structure was lumped using plastic hinge and soil and structure interaction was modeled using BNWF method. First, structure was reviewed with or without soil and structure interaction using nonlinear static analyses and incremental dynamic analyses (IDA). Then uncertainty of soil parameters in soil and structure interaction was considered. Cohesion, internal friction angle, unit weight, shear modulus, and soil Poisson ratio was noted with considering probable distribution and considering consistence between these as uncertainty of soil parameters. Latin Hypercube Sampling (LHS) method and Choleski decomposition were used to manufacture and simulate dependent random variables and manufacture random variables. After manufacturing 26 structure samples for uncertainty of soil parameters, fragility curve in sample collapse level was compared with base fragility curve. 20 far-field records were used for incremental dynamic analyses and obtaining the fragility curve. Screening method was used to define participation percentage of uncertainty of soil parameters in collapse response and structure natural periods. Then, response surface method was used to predict structure response functions. At ultimate, the result presented that considering soil and structure interaction increases the natural periods of structure first mode. Noting the nonlinear static analyses, considering soil and structure interaction decreases the structure base hardness and shear and increases the roof relative displacement. All statistic percentiles of structure IDA curves are lower than fixed base mode with considering soil and structure interaction and present that soil and structure interaction causes structure to collapse in lower spectral acceleration. Comparison of fragility curve in two cases presented soil and structure interaction increases collapse probable. All fragility curves of samples manufactured in investigating uncertainty of soil parameters effect on structure collapse are higher than fragility curve of the case in which structure is modeled hinged at base. This presents that uncertainty of soil parameters increases structure collapse. Also, sample fragility curves are 10.2% and 8.6% greater than fixed base mode at probable collapse of statistic percentiles 16% and 84%. Comparing statistic features of 26 manufactured sample responses for uncertain soil parameters with the case in which structure is fixed at base presents that all manufactured samples presented an increase in structure first mode periodic time and maximum drift between stores and a decrease in structure collapse capacitance and structure collapse drift is more sensitive to soil parameter changes. After orienting structure responses in 26 manufactured samples for uncertainties based on incremental structure first mode periodic time, structure collapse drift increased, and structure capacitance decreased in an increase on structure periodic time. Soil shear modulus has the highest and soil cohesion has the lowest participation percentage of uncertainty of soil parameters in structure first mode periodic time. Soil internal friction angle and soil shear modulus have the lowest participation percentage of uncertainty of soil parameters in responding to structure collapse drift. Soil shear modulus has the largest and soil cohesion and soil Poisson ratio have the lowest participation percentage of uncertainty of soil parameters in structure collapse capacitance response.