Adding cover plates - weld under tension
Adding cover plates - weld under tension
(OP)
We are adding cover plates to an existing continuous steel girder bridge as part of a strengthening rehabilitation, and are trying to give the contractor as much flexibility as possible by allowing both field welded (with bolted end connections) and field bolting options. Some of the flange areas will be in tension at the time the cover plates are added.
Are there any guidelines for field welding on a member under tension?
I've looked in Blodgett, AWS D1.5, and every other reference I have, but no joy. I've found plenty of information for members that WILL BE under tension in service, but nothing useful for welding under tension. Shoring is not a practical option (over water), but we can somewhat modulate the tension and compression zones to some degree through adjusting the areas and sequence of the deck removal. Most of the weight will be off the areas to be cover plated, and the stress at that time will be less than 0.1fy.
Thanks.
Are there any guidelines for field welding on a member under tension?
I've looked in Blodgett, AWS D1.5, and every other reference I have, but no joy. I've found plenty of information for members that WILL BE under tension in service, but nothing useful for welding under tension. Shoring is not a practical option (over water), but we can somewhat modulate the tension and compression zones to some degree through adjusting the areas and sequence of the deck removal. Most of the weight will be off the areas to be cover plated, and the stress at that time will be less than 0.1fy.
Thanks.





RE: Adding cover plates - weld under tension
This seems to be on point:
ht
Mike Halloran
Pembroke Pines, FL, USA
RE: Adding cover plates - weld under tension
The stress on the member is expected to be low compared to its capacity, so I don't anticipate issues with a reduction of member size due to molten areas of steel.
RE: Adding cover plates - weld under tension
RE: Adding cover plates - weld under tension
RE: Adding cover plates - weld under tension
RE: Adding cover plates - weld under tension
RE: Adding cover plates - weld under tension
That said and the note you made about the deck being removed in places, is it possible then to set up a strong back beam with a hoist system? THe hoist would be connected to the girder and the strongback. This will pull the beam up and remove tension. This way the tension or most of it can be removed and the loads moved back to other parts of the beam under question. Now, if the tension is near the pier.....well, good luck.
Regards,
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RE: Adding cover plates - weld under tension
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RE: Adding cover plates - weld under tension
We've eliminated need to weld in areas under tension, so this is pretty much an academic question at this point.
Field welding is another issue and the DOT feels they can adequately control the quality.
RE: Adding cover plates - weld under tension
When you weld on stressed member of a structure you are dividing in phases the construction. First stage, the stressed member and the reinforcement doing nothing. Second stage, when additional loads come in there is a stress variation on member and its reinforcement. To make it more complicated there is other factor and is the stress relieve due temperature.
So if a structure is being reinforced with service loads on it, there is going to be stages, and every stage have to be verified.
RE: Adding cover plates - weld under tension
It's an academic question now, but it lead me to wonder about the general statement of "no welding on the tension flange" that is prevalent in bridge construction.
RE: Adding cover plates - weld under tension