Authors: Lisa Anderson, Tarek Elkhoraibi

Current industry codes, such as ASCE 4-98 recommend consideration of Structure-to-Soil-Structure Interaction (SSSI) only when it is determined to have a significant effect on local results. In some cases, it is not computationally feasible, or too costly, to analyze an explicit model including a complex of all contributing structures. The significance of SSSI is dependent upon several variables, namely the characteristics of the soil, structures, and ground motion, as well as the spatial distance between structures. The SSSI effect is most significant for lighter structures adjacent to more massive structures that are founded on soil sites. The Hanford Waste Treatment Plant Pretreatment Facility Complex is comprised of two small surface-founded structures adjacent to one large embedded structure, separated by a seismic gap of less than one foot. The effects of SSSI are evaluated using explicit modeling of each building on the Complex. A case study, showing the importance of explicit modeling for SSSI analysis of the Hanford Waste Treatment Plant Pretreatment Facility Complex, is presented in this paper. The SSSI effect is illustrated through comparison of seismic member forces and acceleration response spectra. Overall observations are summarized and recommendations for future research are presented.

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