backing bar welds

Date 01-14-2010 16:32

I have a situation on a Fracture Critical joint that I havent run into before and I need advice. Its a full pen weld with a backing bar and no access to the opposite side of the joint. How do I tell the fabricator that the backing bar must be welded on both sides full length. One side can be welded during assembly but one side will have no access. I cant find anything in the code that addresses this issue. Anyone else ever run across this?
Dave

By trapdoor (**)

Date 01-14-2010 21:35

If it is impossible to make a weld per the drawing and or the code then you have to kick it up to the design engineer to make a decision on the course of action that needs to be taken. At least that's what I would do.

By eekpod

Date 01-18-2010 17:39

Any special notes I have our detailer put it in plain english in the tail of the weld symbol.

By brrrrp Date 02-03-2010 12:06

David,

Sorry for the late post, but new to the forum. Paragraph 3.3.7.6 of AWS D1.5, Bridge Welding Code provides you with your answer. The backing bar only has to be welded full length if there is any attachment weld external to the joint on a given side. They just want to make certain that for a cyclically loaded joint, there are no intermittent welds present. So, a continuous weld on one side, and no external welds on the other side of the backing bar is acceptable. As an alternative, Paragraph 3.3.7.5 allows tack welding within the joint on the side where there are no external welds holding the backing in contact with the base metal.

Regards,

brrrrp