View Q&A

Could you give me MwRSF's opinion on the contractor's proposed substitution for the smooth A706 Gr 60 bar (see below)?

"Do you think that we would be able to use A709 Grade 50W in place of the A706 Grade 60 for the loop bars?"

This issue has come up in the past. We have given the following recommendation:

The loop bar steel is the A706 spec because we have found that the small bend diameter can cause reduced ductility and toughness in some grades of steel which compromises the impact strength of the loop. As such, we current specify that the loop steel must have a minimum yield strength of 60ksi, a minimum tensile strength of 80 ksi or 1.25 times the yield strength " whichever is higher, and a minimum % elongation of 14%. A706 and A709 steel can both meet that spec with the correct grade. Others may as well. The bars can be deformed or smooth as long as the steel is within spec. Some of our states prefer smooth, so it is on the drawings that way.

Note that A709 Grade 50 steel will not meet the minimum yield strength given above.