Investigating the behaviour factor and seismic response of structural wall systems in low- to medium-rise buildings when soil-structure interaction is considered

Practicing engineers typically follow linear methods for seismic design and assessment, confining their approach to the requirements of SANS 10160-4 (SANS 2017). This generally leads to a conservative design, leaving little space to apply additional tools for design refinement. Soil-structure interaction has beneficial effects for most building structures under seismic action. However, incorporating soil-structure interaction in the analysis influences the fundamental period, damping and ductility, and will therefore influence the behaviour factor prescribed by design codes. The behaviour factor is necessary for linear methods (force-based methods) to predict the nonlinear behaviour of the structure. This investigation assessed the current behaviour factor for reinforced concrete walls in low- to medium-rise buildings, as prescribed by SANS 10160-4 (SANS 2017), when soil-structure interaction is incorporated in the analysis. The buildings were initially designed and detailed using linear methods, with the prescribed behaviour factor, and then tested using nonlinear methods that do not require the use of a behaviour factor.