| Description |
An improved rapid seismic rehabilitation method for reinforced concrete (RC) columns was implemented for two severely damaged cast-in-place (CIP) concrete columns and two severely damaged precast concrete columns. The CIP columns had severe damage including concrete crushing, and longitudinal steel bar fracture and buckling. The improved method utilizes epoxy-anchored headed steel bars and a carbon fiber reinforced polymer (CFRP) cylindrical shell with unidirectional CFRP layers in both the hoop and longitudinal directions for relocating the damaged end-region. For one precast specimen, cracks epoxy injection was implemented for the column above the CFRP shell. For the other precast specimen, a steel collar with shear studs was developed around the column within the repair region to improve the bond between the column and repair concrete. The experiments showed that the structural performance of the repaired specimens in terms of strength, displacement capacity, and stiffness was successfully restored. Two numerical models, Model Fiber and Model Rotational Spring (RS), simulating the seismic performance of the repaired specimens were proposed. In Model Fiber, distributed plasticity was assumed over a plastic hinge length of the nonlinear beam-column element. In Model RS, concentrated plasticity was considered using a nonlinear moment rotational spring located at the repaired cross-section. Previous concrete damage and low-cycle fatigue of longitudinal steel bars, and bond-slip between iv the damaged steel bars and surrounding concrete were included. Simulations show that the numerical results are in good agreement with the experimental results in terms of hysteretic response and moment-rotation capacity. Seismic performance evaluation of a structurally deficient RC bridge bent was conducted numerically. Detailed design guidelines of the CFRP donut using a simplified strut-and-tie model (STM) were developed. Soil-structure interaction (SSI) was considered using simplified springs and the model was validated using previous experimental results. A comparison of the as-built and retrofitted bridge bents under nonlinear static and dynamic analysis showed that the rehabilitation method improved the seismic performance in terms of load capacity and structural stiffness. The rehabilitation method could be used not only in repairing severely damaged concrete columns after an earthquake, but also for retrofitting structurally deficient bridges before an earthquake. |
