Confinement of High-Strength Concrete with Welded Wire Reinforcement

Today, more and more structures are constructed with high-strength concrete (HSC) because it provides a number of advantages in strength and mechanical properties over normal-strength concrete at a reasonable cost. The gain in strength, however, is achieved at the cost of a loss in concrete ductility. The requirements for transverse steel reinforcement in HSC columns located in high seismic regions, where ductility demand is large, result in high volumetric ratios, that lead to the use of large tie sizes, close tie spacing, overlapping of hoops, bends, and bend extensions. This usually causes reinforcement congestion within the column. An experimental study involving the testing of 14 full-size HSC columns in axial compression was undertaken to determine the effectiveness of using two-dimensional welded wire reinforcement (WWR) grids as transverse reinforcement in the columns. The performance of columns laterally reinforced with WWR was compared with that of columns laterally reinforced with conventional ties. Axial stress-strain diagrams of the concrete core from the experimental tests showed that substantial gains in strength and ductility of columns laterally reinforced with WWR can be achieved if the volumetric ratio of transverse steel was above 3.5%. Strength increases of at least 15% were observed, while ductility increases of 250% and more were recorded in the specimens with WWR when compared with the corresponding specimens with conventional ties.