Effect of in-plane/out-of-plane interaction in infill walls on the floor spectra of reinforced concrete buildings

Currently, in the framework of performance-based earthquake engineering, the seismic assessment of buildings should be performed by considering the safety of non-structural components. This is necessary to protect human life safety from their collapse, as well as to limit the economic losses associated with their damage. Typically, the safety assessment of non-structural components is performed with a force-based approach, i.e., by comparing their force/acceleration capacity with the expected force/acceleration demand under the design earthquake scenario, i.e., with reference to different limit states. Different acceleration demand models, i.e., floor response spectra, exist, but relatively few of them were defined by considering the influence on the structural response of the in-plane response of infill walls, and none of them by considering the so-called “in-plane/out-of-plane interaction” effects. In other words, it is nowadays well known that the out-of-plane damage of unreinforced masonry infills affects their in-plane response, thus influencing the seismic response (and the floor response spectra) of the supporting structure. In this paper, non-linear time-history analyses are performed on reinforced concrete framed buildings with different number of storeys, design level, and infill wall layout. The analyses are performed on the bare structure as well as on the infilled structure by considering and by not considering the in-plane/out-of-plane interaction effects in the infill wall model. The acceleration floor spectra derived from the analyses are compared, thus investigating the potential effect of the in-plane/out-of-plane interaction effect on the expected acceleration demand acting on infill walls.