Estimation of inelastic displacement demands of flexible-based structures on soft soils

Abstract

This study aims to develop efficient tools for performance-based seismic design of soil-structure interaction (SSI) systems on soft soils. To simulate the SSI effects, linear and nonlinear 'equivalent fixed-base single-degree-of-freedom' (EFSDOF) oscillators as well as a sway-rocking SSI model were adopted. The nonlinear dynamic response of around 10,000 SSI models and EFSDOF oscillators having a wide range of fundamental periods, target ductility demands, and damping ratios were obtained under a total of 20 seismic records on soft soil sites. Based on the results of this study, a practical method is developed for estimating the base shear and maximum displacement demands of a nonlinear single-degree-of-freedom structure on soft soil deposits. In the proposed procedure, the effect of frequency content of ground motions is considered by normalising the period of vibration by the spectral predominant periods, while the nonlinear EFSDOF models are used to improve the computational efficiency.Keywords: soil-structure interaction; soft soil; displacement demands; response-history analysis; frequency content. Biographical notes:Yang Lu is a graduate student in the Department of Civil Engineering at the University of Nottingham. His work focuses on numerical and analytical modelling of dynamic soil structure interaction. He is currently working on implementation of soil-structure interaction into performance-based seismic design of building structures. His research interests include soilstructure interaction modelling, response spectrum analysis for near-fault and far-field earthquake motions, and displacement-based design. 82 Y. Lu et al.Iman Hajirasouliha is a Senior Lecturer (Associate Professor) in the Department of Civil and Structural Engineering at the University of Sheffield, UK. He has over 15 years of research experience in the field of earthquake engineering, optimisation, seismic risk assessment, and performance-based seismic design and strengthening of buildings and infrastructure. He has authored a book chapter and over 100 papers in refereed journals and international conferences. He has ten years consultancy experience in the structural design and strengthening of buildings and industrial structures. He is currently the Leader of the Earthquake Engineering Group (EEG) at The University of Sheffield.