Assessment of double story single bar RC frame through FEM modelling

This study explores various reinforcement detailing strategies for Double-Story-Single-Bay (DSSB) reinforced concrete (RC) frames, using SAP 2000 for design and ABAQUS for nonlinear finite element analysis (NLFEA). A finite element analysis (FEA) model of the DSSB was developed in ABAQUS, calibrated to incorporate diverse materials and geometric parameters based on experimental data from previous tests on the specimen. The Concrete Damaged Plasticity (CDP) model was employed to simulate the behavior of the concrete matrix, while steel reinforcement bars were modeled as bilinear elastoplastic materials to accurately capture their yielding and hardening characteristics. Upon calibration, the peak lateral load and peak displacement values from the FEA models closely aligned with experimental results, demonstrating stress values in line with the empirical data. The calibrated Control Model (CM) served as a foundation for examining three additional FEA models: (a) Half-Diameter Stirrups in the Beam (HDB), (b) Half-Diameter Stirrups in both Beam and Columns (HDBC), and (c) Double Spacing of Stirrups in Beam and Columns (DSBC). This evaluation focused on assessing the impact of critical design parameters, such as the transverse reinforcement ratio (ρt), on the load-carrying capacity of the DSSB, particularly with respect to brittle failure modes. The results indicated that all the modified FEA models exhibited lower lateral load capacities than the CM, with reductions of 4.45%, 13.8%, and 5.2% for HDB, HDBC, and DSBC, respectively.