Repair of defective weld 1

[mike80]

I am looking for advice on a weld repair. The fabricator is fabricating a fracture critical steel girder with butt welds in the flanges. During the inspection of one of the bottom flange butt welds, a slag inclusion was found. The fabricator proposed a repair to remove the slag inclusion and re-weld. The concept was proper and the repair was made and the weld tested again. Now the repaired weld has a slag inclusion which the fabricator is proposing to repair by the same procedure, except being more careful. Is it acceptable to remove and re-weld this splice again?

 

[Ron]

It is acceptable to do so, but a couple of precautions should be taken. Depending upon the thickness of the flange, you might consider both pre-heat and post-heat conditioning, even though it might not be mandated by the code for your thickness. This can help moderate the effects of additional repair work to the same heat affected zone.

 

[JAE]

Would continued heating/cooling/heating with the weld repairs cause some increase in steel brittleness? Anyone out there have thoughts on this? After all, he stated that this is a fracture critical member - no redundancy means be very sure there is no fatigue.

 

[ishvaaag]

My only comment to this is that if the situation is as dire as JAE puts, and it is because of no redundancy, some statements in the codes on what is allowed and not in the process of fabrication wouldn't be to ask much.

Other than that, what but methods that simply produce the intended member in best individual designer knowledge and insight can the user have?

 

[Ron]

JAE...that's the reason for the suggestion to pre-heat and post-heat. In fracture critical members, it is important that the heat affected zone be moderated as this is where many cracks occur. Without pre-heat and post-heat treatment, you can end up with three distinctly different metallurgical zones which will act independently to stress, thus creating a greater propensity for cracking, whether induced by residual stresses or by fatigue.

 

[JAE]

Merci

 

I want to choose consulting engineer for retrofiting of steel structures.Please, guide me which characteristics they should have?
Best Regards
Ali Tabaar

 

[Ron]

The engineer should be experience in constructability evaluation as well as being a structural engineer with steel design experience. Ask for evidence of similar experience and interview references, particularly if the project is large or especially complex.