Comparison of modified precast concrete corbel and nib connections under cyclic loading: numerical assessment

This study presents a comparative numerical investigation of two widely used precast connection types: corbels and nibs, subjected to displacement-controlled cyclic loading. The configurations of the connections were specifically designed and modified to enhance seismic performance. Three-dimensional finite element (FE) models were developed to simulate nonlinear concrete behavior, bond-slip mechanisms, and interface interactions between precast elements. The models were calibrated and validated using experimental results, ensuring accurate simulation of crack propagation, energy dissipation, and moment-rotation behavior. The simulation results revealed that the nib connection achieved a 51% higher ultimate load capacity (178.5 kN) compared to the corbel connection (118.3 kN), indicating superior load resistance. However, the corbel connection demonstrated a slightly greater displacement capacity, with 9.7% higher ultimate displacement. Both connections showed higher energy dissipation in the numerical models than in experiments, with differences of 42% and 40% for the nib and corbel connections, respectively attributable to damping calibration and bond/interface idealizations. Stress distribution analysis indicated that the corbel joint concentrated stress in localized areas, whereas the nib connection facilitated more even stress distribution.