Earthquake behavior of reinforced concrete flat slab buildings according to shear wall ratio - TBEC 2018 innovative 2-stage solution

The enactment of the Turkish Building Earthquake Code (TBEC 2018) has prompted a number of significant developments in the analysis and design of structures. In particular, the procedures for determining the earthquake load differ significantly from those set forth in the TBEC-2007 regulation, which it replaced. One such distinction is the two-stage analysis methodology that has been introduced for the analysis of beamless slab systems. In this method, the column connections are modelled as monolithic in the initial stage of the calculation. Subsequently, in the second stage of the calculation, the column frames are modelled with bottom and top hinges, and the resulting structure is analysed. After the analysis, the internal forces in the columns, shear walls and slabs will be considered as the unfavourable one of the results obtained in the two stages, while the relative story drifts will be taken from the first stage, i.e., monolithic modeling. In this way, it is aimed to make a safe design even in the worst case scenario by taking into account the changes that may occur in the behavior of the structure and the cross-sectional effects of the load-bearing elements at the design stage. In this study, a building with a symmetrical flat slab system is modelled in accordance with the 2018 TBEC standard, and the behaviour of the structure is investigated by considering different shear wall ratios and thicknesses. For this purpose, a structure with 4 differently placed shear walls with thicknesses of 40 cm and 50 cm, was modeled using the Etabs program which analyses according to the finite element method. Shear wall lengths were calculated according to the determined shear wall ratios and analysed by modeling as pinned and monolithic as specified in the regulation. The period values, shear forces and displacements of the structure for 48 models obtained as a result are explained in detail with graphs and the behavior of the structure and the results of the 2-stage analysis method are evaluated.