Experimental and Numerical Studies of Reinforced Concrete Columns with Openings Strengthened Using High-Performance Concrete Jackets and Near-Surface-Mounted Reinforcing Bars
Abstract
In practice, openings in reinforced concrete (RC) members may be introduced to accommodate mechanical/electrical services or may be created accidentally during renovation, compromising structural integrity. This paper proposes integrated strengthening method for RC columns with a circular opening at mid-height using engineered cementitious composites (ECC) or ultra-high-performance fiber-reinforced concrete (UHPFRC) jacketing reinforced with glass fiber mesh, and near-surface mounted (NSM) steel or glass fiber-reinforced polymer (GFRP) bars bonded with epoxy adhesive. To facilitate, experimental and numerical investigations into the behavior of the proposed strengthened RC columns under axial compression are carried out and reported in this study. A total of nine RC columns with and without a circular opening at mid-height are tested and analyzed. A 3-dimensional finite element model is developed using ABAQUS to simulate the responses of strengthened RC columns with defects. The validated model is employed to investigate the effects of NSM reinforcing bar diameter and jacket thickness on the behavior of RC columns with openings. It is shown that the strengthening techniques improve the stiffness, strength, and energy dissipation of RC columns with openings, restoring them to up to 1.79 times that of the unstrengthened column. The use of NSM reinforcing bars can improve the capacity of RC columns but cannot prevent them from brittle failure. Increasing the diameter of NSM bars considerably increases the ultimate loads of the strengthened columns, whereas increasing the thickness of concrete jackets improves their ultimate loads. The results emphasize how defect-prone RC columns may be considerably changed into ductile, high-resistance columns using such advanced materials, offering durable and useful outcomes for increasing the lifespan of RC structures.