Effects of Staircase Modeling on Assessing the Seismic Response of Gravitational RC Building

This study investigates the seismic response of an existing reinforced concrete (RC) building designed for gravity loads only. The paper focuses on the effects of explicitly modeling the staircase with knee beams on the seismic response of the RC building 3D model. The case study is a rectangular 6-story RC building representative of the Italian 1970s design and construction practices for gravity loads only. Three model variations are considered: a) the base model without the staircase; b) the model with the staircase in a central position (eccentricity in one direction only); c) the model with the staircase at a building corner (eccentricities in both directions). The results of nonlinear static and dynamic analyses are presented and fragility curves are derived. The results show that the presence of the staircase significantly affects the response of th RC building. The staircase changes the modal parameters, the lateral stiffness and the collapse mechanism that tends to become more brittle with increasing eccentricity.