Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Ductility of Concrete Members Reinforced with Welded Wire Reinforcement (WWR) Mohamed Shwani a , Raed Tawadrous b, ⁎ , Marc Maguire c a The American University of Iraq, Sulaimani, Sulaimani – Kirkuk Main Road, Raparin, Sulaimani, KRG, Iraq b EConstruct, Florida, 3452 Lake Lynda Drive Suite 350, Orlando, FL 32817, United States c Department of Civil and Environmental Engineering, Utah State University, Logan, UT 84322, United States ARTICLE INFO Keywords: Welded wire reinforcement Ductility Strain localization Failure mode Reinforced concrete ABSTRACT Past research studies have been conducted on the ductility of concrete members reinforced with welded wire reinforcement (WWR) and determined a new phenomenon called strain localization reduces member ductility due to superior bond between WWR and concrete. Such studies have concluded that strain localization adversely affects the ductility of members reinforced with WWR and it is unsafe to use WWR as tension reinforcement. In this study, 50 simply-supported, concrete slabs with a representative slab width of 2 ft (610 mm), thickness of 7 in. (180 mm), and total length of 21 ft (6.4 m) were tested to further examine the strain localization phenomenon on global deformations. Two major parameters were investigated, cross-weld spacing and wire diameter. The impact of these two parameters on strength, ductility, and mode of failure of concrete members reinforced with WWR was also studied. Moment curvature analysis was used to estimate inelastic deflections and ductility to investigate the effect of the reinforcement total elongation at failure of the wire material on the overall member ductility. It was observed that members reinforced with WWR with cross-weld spacing of 14 in. (355 mm) or more had similar ductility as members reinforced with loose wires (without cross-weld). Members reinforced with WWR with closely spaced cross-weld (i.e., 3 or 7 in. (75 or 180 mm)) showed erratic and often less ductility, however, the wire itself was shown to have low ductility. Failure of members reinforced with WWR provided sufficient warning prior to failure as evidenced by the ductility ratios in excess of 2.5. Additionally, a moment- curvature analysis based parametric study showed that an acceptable level of ductility can be achieved with a minimum total elongation of wire reinforcement of 3% at failure. 1. Introduction Welded wire reinforcement (WWR) was first used in 1908 in road pavement construction [1]. After World War II, WWR was extensively used in building construction in Europe because it required less labor and time to place compared to conventional reinforcing bars. Currently, WWR is being widely used in various types of structures such as com- mercial and residential buildings, parking structures, highways, bridges, airports, walls and barriers, and tunnels due to its cost effec- tiveness and short placement time [2–4]. The yield strength of WWR is usually higher than that of conven- tional bars (usable up to 80 ksi (550 MPa)), which reduces the required amount of steel by approximately 30%. However, wire reinforcement in general has lower ductility than conventional bars due to the cold- drawing process [5]. Additionally, welding of the wires to make WWR further reduces the ductility and tensile strength of the wires. The primary reason for the reduced ductility is the changed material properties caused by the welding process [6]. Mo and Kuo [7] reported that heat from the welding process creates a metallurgical notch and re- crystallization of the microstructure of steel particles that result in de- creasing the failure strain after the yield point. Therefore, the plastic range in the stress-strain curve is decreased and sudden/brittle failure of WWR will take place. Annealing, the process of reheating steel to approximately 650 °C (1200 °F) and slowly cooling it down, helps to mitigate the effect of the weld and increase the ductility by approxi- mately 35–45% [7]. The American Concrete Institute, Committee 318, (ACI 318-14 [8]) allows the use of WWR in members resisting flexure, axial, shear, and torsion forces in all structural applications except members constituting special seismic resisting systems (ACI 318-14 Sec. 20.2.2.4). For the latter, ACI 318-14 allows only the use of low-alloy Grade 60 steel due to its high ductility. Safety concerns about the use of WWR as tension https://doi.org/10.1016/j.engstruct.2019.04.081 Received 7 November 2018; Received in revised form 4 April 2019; Accepted 26 April 2019 ⁎ Corresponding author. E-mail addresses: Mohamed.shwani@auis.edu.krd (M. Shwani), raed.tawadrous@gmail.com (R. Tawadrous), m.maguire@usu.edu (M. Maguire). Engineering Structures 191 (2019) 711–723 0141-0296/ © 2019 Elsevier Ltd. All rights reserved. T