Flexural Behavior of Concrete Beams Reinforced for Shear with Steel Welded Wire Fabric

Abstract

Past studies have shown that welded wire fabric (WWF) can be used as an effective alternative to stirrups in resisting shear in reinforced concrete (RC) beams. Such a form of reinforcement reduces the time required to assemble the steel cage and eliminates anomalies in the fabrication and placement of the stirrups. In this study, the flexural behavior of RC beams transversely reinforced with closed steel cages made by cold-forming WWF sheets is investigated. To accomplish the goals of the study, twenty-three 2000 mm long beams with 200 mm x 300 mm cross-section are tested under two-point load configuration with consideration of different wire diameters (4, 6, and 8 mm), grid openings (25, 50, and 100 mm), concrete compressive strengths (30 and 35 MPa), and longitudinal steel reinforcement ratios (about 0.77% and 1.92%). The specimens are provided with linear variable differential transformers and strain gauges and tested inside a universal test machine. A comparison between the test results of WWF reinforced beams and their equivalent stirrup reinforced beams is carried out for benchmarking purposes. The experimental study was accompanied by a theoretical component utilizing the flexural design provisions in ACI 318 concrete design code. In general, findings of the study demonstrated that WWF reinforced beams possess on average 2% higher stiffness at service load level, 18 % more bending moment capacity, 19% lower ductility, and 4% extra residual capacity than corresponding stirrups reinforced beams having the same volumetric ratio of transverse steel. The use of WWF with a small grid opening is not essential because reasonable confinement can be obtained by WWF with a grid opening as large as 100 mm, which will ease any concerns about concrete infiltration between the wire reinforcement of the WWF. The average experimental-to-predicted flexural capacity of concrete beams enclosed with WWF is equal to 1.0 when calculated using the actual (not nominal) material properties; thus, the ACI 318 code can be reliably used to predict the bending moment capacity of such beams. The study recommends providing longitudinal reinforcement in the form of rebars in concrete beams containing WWF in order to maintain a reasonable level of flexural ductility.