Assessment and retrofitting of reinforced concrete buildings with shear walls subject to earthquake loading

Abstract

A large number of reinforced concrete (RC) buildings not designed to resist seismic loading are located in earthquake prone regions. If these structures are not assessed and eventually strengthened, in the near future they will potentially suffer significant damage due to the effects of earthquakes causing casualties and economic disruption. Thus at present, seismic assessment and retrofitting of existing RC buildings is a major challenge which requires the use of realistic structural analysis techniques and practical and effective strengthening solutions. In this research, the use of RC walls as a global strengthening measure to enhance to seismic performance of existing framed buildings is considered. The study commences with a critical appraisal of existing modelling strategies for RC walls subjected to in-plane loading. The wide-column approach, the use of 2D detailed FE descriptions and macro-elements with nonlinear springs and rigid links are considered, and models based upon these alternative strategies are implemented in ADAPTIC, an advanced finite element code for nonlinear analysis of structures under extreme loading. A parametric study allowed identifying the most effective modelling strategy to be used within detailed nonlinear representations for RC buildings subjected to earthquake loading, and potential enhancements for existing models to be implemented to achieve a better representation of the response of RC walls subjected to in-plane loading. In the second part of the research an enhanced description using macro-elements to describe RC wall units is developed. It employs novel coupled nonlinear springs to describe wall portions modelled as RC panels subjected to biaxial stress/strain states. Model accuracy and efficiency is shown in numerical examples on slender and short walls. In the final part of the research, an advanced 3D modelling strategy for representing the nonlinear dynamic response of RC buildings with shear walls is presented and used in accurate simulations. The seismic assessment of a realistic RC building is carried out and the effectiveness of using RC walls as global strengthening measure is shown comparing the seismic performance of the original structure against that of the retrofitted building.