Nonlinear behavior of reinforced concrete slabs of tall buildings

Due to land scarcity in urban areas, the construction of tall buildings has been increasing. In structural design of reinforced concrete tall buildings, performance-based design approach has gained particular importance in regions with high seismic activity. In this approach, preliminary sizing and reinforcing of structural members are done with respect to design earthquake level and performance of structural members is investigated through the comparison of nonlinear deformation demands obtained for maximum credible earthquake level with respect to limits defined in seismic code. However, such comparison of nonlinear deformation demands is generally limited to walls, columns and beams having primary importance. In parallel with modern architectural requirements, flat slab structural systems with only beams at perimeter frames have become widely preferred for tall buildings. In these structural systems, flat slabs function for distribution of inertia forces as well as coupling between perimeter frames and central core wall system. Therefore, flat slabs of such structural systems would be considered as critical members for lateral force resisting mechanism and their nonlinear behavior should be investigated performance-based design procedure. In this study, a typical reinforced concrete tall building composed of central coupled core wall system, perimeter frames and flat slab is designed. The nonlinear behavior of slab is investigated through nonlinear response history analysis for maximum credible earthquake level considering different modeling techniques. According to analyses results, the nonlinear deformation demands at the supports of flat slab could reach to significant levels not only causing the failure of slabs as components of structural system but also affecting the performance of coupled core wall system by altering the nonlinear deformation demands. Finally, it is shown that determination of nonlinear deformation demands of slabs as part of performance-based design procedure and keeping them below conservative limits to be defined in seismic codes are crucial.