Group Behavior and Concrete Breakout Strength of 16 MM Deformed Wire Anchors in Tension

Due to lower carbon equivalents than those in steel reinforcing bars, deformed wires are easy to weld. Embedment steel plates welded with a straight deformed wire anchor (DWA) are commonly used to connect steel structural members to concrete members. Because there is no anchor plate at the end of the DWA, the failures of concrete breakout and side-face blowout usually caused by the anchor plate have not been considered. Only the development length of deformed bars governs the anchorage design of the DWA. However, a concrete breakout is thought to be a possible failure. To investigate the failure modes and anchorage strength of DWAs under tension, 13 pullout tests of DWAs embedded in concrete of [f.sub.ck] = 42 MPa (6000 psi) were performed. In each specimen, 25 DWAs of [f.sub.y] = 515 MPa (75 ksi) were placed in a 5 x 5 form. The experimental variables included the embedment depth and spacing of the DWAs and the absence of cracking across the DWAs. Failure modes and maximum loads were investigated and compared to predictions by the concrete capacity design (CCD) method (Fuchs et al. 1995). All specimens failed due to concrete breakout. Evaluating the experimental results with a 5% fractile safety factor (Fuchs et al. 1995; Natrella 1966) shows that the concrete breakout strength of the DWAs is equivalent to the strength of a headed anchor and can be safely designed according to Chapter 17 of ACI 318-19. Keywords: anchorage; bond; concrete breakout failure; deformed wire anchors.