2-D soil-structure interaction in time domain by the SBFEM and two non-linear soil models. Issue 88 (September 2016) - Rahnema, Hossein
Abstract: Effects of soil-structure interaction (SSI) have proven to be of more importance than to be ignored. Quite a few methods of modeling and analysis exist to anticipate the real behavior of the structure when placed on flexible soil rather than on rigid ground surface. Yet, how to model the soil needs to be inspected carefully since probable deformations of soil may be at times far from predicted. In this study a newly formed approach is inspected to suggest possible solutions to shortcomings of conventional ones, compare two non-linear soil models, and implement strengths of newer methods. The soil-structure system is modeled and analyzed once directly with the UCSD soil model and then compared with non-linear sub-structuring method with the UCD model. Analyzes are performed in the time domain for both cases. The soil is supposed to be comprised of sands with various density values. The Loma-Prieta earthquake record (Loma-Prieta, 1989) is used to carry out time domain analyzes and capture structural responses. The interactional forces exerted to the near-field soil, which account for the interaction between these two media as well as the radiation damping of the infinite half-space, have replaced the earthquake motion and the far-field has accordingly been truncated out. The non-linear near-field soil-structure system has then been dynamically analyzed. Force outputs reveal a decrease when elastoplastic SSI is considered; while displacement amplitudes are found to be greater for cases not involving SSI, or involving elastic SSI. Changing the applied constitutive model for the soil as well as sand density from loose to dense manifests changes in responses. As the soil gets denser, the SSI behavior gets closer to that of the elastic case. Contrary to the sub-structuring method which usually, and conventionally, assumes linear elastic behavior for the soil-structure system, direct modeling may predict non-linear responses of the system and effects of the structure′s being placed upon an inelastic environment. Graphical abstract: Highlights: An SSI analysis approach is discussed covering possible shortcomings in far-field. The near-field soil of the system is modeled twice with UCSD and UCD soil models. SBFEM is used to model the effects of far-field on the fictitious boundary. An RC frame is modeled on the soil, responding to the input seismic motion. Effective input motion is calculated using dynamic stiffness matrices of the system.