Preliminary Numerical Investigation of the Effects of Staircases on the Seismic Behaviour of Existing Pre-code RC Framed Buildings

This study investigates the seismic response of Reinforced Concrete (RC) framed buildings designed for gravity loads only, as very common in the Italian residential building stock before 1970. In particular, starting from the same building configuration (both in plan and elevation), the attention is mainly focused on the evaluation of the role of staircases on the global seismic behaviour, considering three possible cases: neglecting the presence of staircases, with the staircase substructure realised with cantilevered steps from knee beams, and with the staircase substructure realised with cantilevered steps from RC walls. The seismic response is investigated by nonlinear pushover analysis, and the results obtained from two different modelling approaches are discussed and compared. Even though staircases are considered as secondary structural elements and often calculated separately from the main structure, they can be elements of potential damage in buildings. The results obtained, although preliminary, highlight the non-negligible effect of the staircase typology on the seismic response, in terms of period of vibration, lateral stiffness, maximum base shear and ductility. Moreover, the presence of stairs can also give raise to torsional effects.