Interface boundary technique of hybrid test for seismic ground response analysis

Abstract

Seismic ground response analysis is critical in predicting ground surface motions and estimating earthquake-induced forces that triggers geologic hazards, such as liquefaction and landslide. Due to the lack of a rational and general interactive framework, hybrid tests for seismic ground response analysis have very limited progress. In this study, an interactive framework for general geotechnical models with an interface boundary technique is proposed to facilitate such hybrid tests. According to the geometry feature of the interface between physical and numerical subdomains in a ground model, the experimental control nodes are determined and the corresponding interface initial stiffness matrix is estimated using the displacement-based method and incorporated in the numerical model of the physical subdomain. Subsequently, the hybrid testing framework is built in the FEM program OpenSees and the associated middleware OpenFresco. To validate the proposed interface boundary method, hybrid test rehearsals, i.e. virtual hybrid tests were performed on a typical ground model with medium sand and stiff clay subjected to different earthquake motions. Compared with the numerical simulation, the results obtained from the hybrid test rehearsals show that the vertical stress and deformation of the ground were adequately captured by the interface boundary technique. To further illustrate the reliability of the interface boundary technique, the effects induced by the deviation of initial stiffness matrix estimation and the height of the physical subdomain are discussed with recommendations of future implementation of the hybrid tests for seismic ground response analysis.