Welding of Reinforcing Steel Between Precast Concrete Units
J. Neils Thompson, Hudson Matlock, and A. Anthony Toprac
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It has been establish ed that damage to welded splices between unrestrained precast concrete units consisted primarily of cracking due’to differential thermal expansions. This study was intended to establish the effects of the controlling variables and to evaluate the damage. Specimens consisted of pairs of concrete blocks cast with a deformed reinforcing bar protecting from the end of each block. The bars were connected with 60 deg V-butt welds, performed at a reasonably rapid rate. Temperatures were measured with thermocouples along the steel bars and output voltages of the thermocouples were repeatedly scanned. Crack lengths were measured immediately after welding. Temperature distributions were found to be primaily functions of the bar protection (distance of weld from face of concrete). They were not affected much by bar size, thickness of cover, or welding procedure. Higher temperatures obtained with bare bars indicated a considerable amount of conduction of heat to the concrete in the regular units. Bond tests did not show that any significant decrease in strength was due to the cracks formed by welding. Apparently, with the specimens and procedures used, it made little difference whether the initial crack was formed during welding or later by initial loading in the pull-out test.