Weld a piece along an existing welding

By Dalcabej Date 09-25-2017 13:50

Hi!

In a beam of a bridge, is permitted weld a stiffener over and along an existing welding in the web?
I need join two pieces of 6000 mm length to form a web with 3000 mm height. But according to the design drawing, over that welding is neccesary to weld a stiffener. I do not know well the codes D1.1 and D1.5, please do you know if there is any prohibition or recommendation about this welding?

https://ibb.co/iofXZQ

By Joey

Date 09-26-2017 03:56

I don't see why not allowed if the drawing permitted. But NDT if required on longitudinal seam must be completed first on the portion where stiffener plate will be welded.

By Dalcabej Date 09-26-2017 12:19

Thank you!

By 803056

Date 09-26-2017 05:20 Edited 09-26-2017 05:24

Not sure exactly what you are describing, but if you are talking about intersecting welds this may help. Generally the codes discourage intersecting welds. One can analyze the residual stresses as vectors. Two welds intersecting at 90 degrees can produce a resultant that exceeds the tensile strength of the weld or base metal. That can cause a crack to form with an orientation perpendicular to the vector representing resultant. This becomes more problematic for the higher strength steels because the ratio of YS over TS approaches unity and high strength steels typically have reduced elongation properties, thus are more prone to cracking because they cannot dissipate the forces by plastic deformation.

The work around is to trim the corners of stiffeners for example so the welds cannot intersect.

A diagram is probably easier to understand. So, look at the attached sketch that only considers the longitudinal residual stress to simplify the problem.

Al

ResidualStressforTwoIntersectionWeldsA99.jpg (50k)

By Dalcabej Date 09-26-2017 12:18

Thank you!

Your post help me to understand better the intersection in welds

By Joey

Date 09-27-2017 05:18

Good points Al. True that there are codes that prohibit the splice welds from intersecting. If I remember there is an offset of min 5t. The photo shown in OP is fillet welding on stiffener plate crossing the longitudinal weld (splice joint). Circular hollow sections formed by spiral welding or longitudinal welding are very common, it is also common to see the fillet welding on stiffener ring that crossed this splice joint.

By Dalcabej Date 09-28-2017 12:54

I have seen the requirement of an offset of min 5t in the BPVC S.VIII, but permits lesser distance or inclusive the intersection as long as a radiography test be performed in 4 inches each side from welding.
In the case that are in the original post, there is not a intersection in welds. Is one weld over another weld in all distance.

Sample image in https://ibb.co/h2POTk

By welderbrent (*****)

Date 09-28-2017 13:27

Last I checked, the Bridge Code and Section 8 were totally different in application.

By 803056

Date 10-01-2017 13:47

I would expect the groove weld would have to be examined and accepted before installing and welding the stiffener. As for the code, I can't say either way unless I was to research it first. To do that, one would have to identify exactly what code they are working with.

Nice sketch by the way. That really does a fine job of showing us the situation. A picture is worth a thousand words!

Al