Study of tack welding of reinforcing steel

Tack welding can improve the accuracy of positioning reinforcing steel and lead to cost savings, particularly in the manufacture of precast beams. There is concern however that tack welds present a fatigue risk in structures subjected to dynamic loading, and it is only permitted by the Department of Transport's Specification for Highway Works (see IRRD 803111) where it can be shown that there is no fatigue risk. A study has therefore been carried out of tack welding of reinforcing steel in prestressed and reinforced concrete beams. The report provides guidance on the use of tack welding in bridge beams, and methods of assessment for fatigue. The conclusions of the study are presented in the form of a draft Note for Guidance, with an extensive commentary which explains the background to the items within it, and refers to other documents and to supporting information in the report. It is suggested that tack welding should be permitted subject to certain limitations, for example it should not be used for bars subject to stress from concentrated wheel loads such as in deck slabs. (A)