Numerical Investigation of Cyclic Flexural Behavior and Hysteretic Degradation in Reinforced Concrete Beams

Understanding the cyclic flexural response of reinforced concrete (RC) beams is essential for evaluating and improving the seismic performance of infrastructure subjected to earthquake loading. This study numerically investigates the cyclic flexural behavior of RC beams, with particular emphasis on the effects of compressive strength (fc) and longitudinal reinforcement ratio (ρsl) on hysteretic performance. A three-dimensional nonlinear finite element model was developed in LS-DYNA using advanced constitutive formulations for concrete and steel; then validated against published experimental data on full-scale beams subjected to displacement-controlled cyclic four-point bending. The numerical model accurately reproduces the experimental hysteretic response, with deviations in dissipated energy of approximately ۱.۸% and ۲.۵% for the first and third loading cycles, respectively; while a larger deviation in the second cycle is mainly attributed to localized damage evolution and crack coalescence at higher deformation levels. The simulations capture the evolution of flexural cracking with good agreement during the early loading cycles, whereas minor discrepancies in later cycles are attributed to idealized material homogeneity and limitations in representing cumulative damage effects. Parametric analyses indicate that increasing f_c from ۲۴ to ۳۰ MPa enhances the peak load capacity by ۱.۷% and ۳.۱% for reinforcement ratios of ۰.۶% and ۱%, respectively. The results further showed that higher ρsl leads to a reduction in the equivalent viscous damping ratio (βeq) because of the associated increase in effective stiffness, whereas higher fc enhances damping capacity.

کلیدواژه ها:

Reinforced concrete beams ، Cyclic Flexural Behavior ، Nonlinear Finite Element Analysis ، Hysteretic Energy Dissipation ، Reinforcement Ratio ، equivalent viscous damping