Simplified modelling and seismic retrofitting of a flat-slab RC structure

The construction of reinforced concrete (RC) buildings with flat-slab systems has become widely used in some high seismicity European countries. This type of structure is particularly common both for office and residentialbuildings, taking advantage of the reduced floor height to meet economical and architectural demands. Even though some national codes may include rules for the design of these structures, the provisions of Eurocode 8 don’t cover flatslab frames used as part of the lateral load resisting system. The behaviour of this type of structural systems with slabframes used as seismic resistant elements shows important drawbacks, such as the essentially non-dissipative featuresof their seismic response. Main results of seismic analyses performed on a six-story RC building structure are reportedin this study. The building was modelled according to a simplified approach based on the effective beam width method,which allowed to change the original flat-slab structure into a frame system consisting of beams and columns. The structural response was predicted using nonlinear static and dynamic analyses with artificial ground motion records with increasing intensity. Different seismic retrofit techniques were applied to enhance the seismic performance of the structure including: 1) the insertion of shear wall; 2) the addition of RC column jackets; 3) confinement of the column plastic hinge regions using FRP wrapping. A mixed retrofitting intervention was also considered to allow the structure to withstand stronger seismic excitations. The predicted seismic performance of the retrofitted models was compared to that of the unretrofitted counterpart. Numerical investigations provide information about the seismic performance of a common type of RC structure not covered by the provisions of Eurocode 8 as well as the potential to mitigate the damage for varying earthquake intensities through different retrofit techniques.