Mechanical Properties of Welded Splices on Cold-Bent Reinforcing Steel

Welded splices on cold-bent reinforcing steel hoops and spiral bars are commonly used for bridge construction as confinement in the concrete-filled steel pipe pile system. In seismic regions, ASTM A706 Grade 60 reinforcing steel is often specified for bridge members expected to form plastic hinges. Structural adequacy of the pipe pile system is essential for seismic performance. However, welding on cold-bent reinforcing steel hoops and spiral bars is not in compliance with AWS D1.4 Structural Welding Code – Steel Reinforcing Bars. The code prohibits welding within two bar diameters of the bent portion of the steel. This paper evaluates the effect of welding on cold-bent ASTM A706 Grade 60 reinforcing steel. Changes in microstructure and microhardness in the heat-affected zone (HAZ) of welded lap splices were characterized as a function of amount of cold-work, bar diameter and heat input. The effect on weld strength and ductility is currently determined using guided bend testing of welded lab splices and tensile testing of indirect butt welds. Gleeble simulation of HAZ microstructures for subsequent tensile testing is planned to obtain the monotonic stress-strain behavior locally in the HAZ of welded cold-bent reinforcing steel.