Numerical investigation of reinforced concrete structures with vertical element discontinuities within the framework of nonlinear theory

Vertical irregularities in structural systems, such as the discontinuity of columns, walls, or beams, can occur in various configurations depending on the layout of structural members. These irregularities introduce discontinuities in the transmission path of seismic forces from the superstructure to the foundation, creating uncertainties in seismic demand and structural response. This thesis aims to investigate the seismic behavior of reinforced concrete building systems exhibiting vertical column discontinuity, categorized as a Type B3 vertical irregularity in the Turkish Building Earthquake Code 2018 (TBDY-2018), under Design Basis Earthquake (DD-2) level ground motions using nonlinear inelastic analysis methods. The study assesses how well these systems, designed according to code provisions, can meet the intended performance objectives through a detailed parametric investigation. In the study, frame systems with four spans and three different heights (3, 5, and 7 stories) are modeled with varying lengths for the two middle spans (L = 2m, 3m and 4m). Vertical discontinuity is introduced by removing the mid-axis column at the ground story. The structural designs of the buildings comply with the relevant provisions of TBDY-2018. Since the structural systems lack any irregularities in plan, the analysis focuses on the critical elevation frame where the discontinuity occurs, resulting in nine distinct structural models. Nonlinear time history analyses are conducted under the horizontal and vertical components of 11 real ground motion records scaled to the DD-2 hazard level. Displacement-based response parameters and brittle behavior demands are obtained. The mean demand values for both element-level and global response quantities—including story displacements, interstory drift ratios, plastic rotations in beams and columns, and the distribution of plastic hinges—are evaluated against the performance limits specified in TBDY-2018. The parametric evaluation reveals that the vertically irregular reinforced concrete systems, despite the column discontinuity at the ground level, generally meet the target damage limits (performance objectives) under combined horizontal and vertical seismic demands when designed according to the code. It is concluded that the use of vertical design spectra and the application of capacity design principles significantly enhance the favorable seismic performance of these systems.