Full Penetration Weld at Bearing Stiffeners?
Full Penetration Weld at Bearing Stiffeners?
(OP)
The client wants to do full pen welds for bearing stiffeners on a plate girder instead of mill to bear with fillet welds. My understanding is fabricators don't like it because it causes distortion to the flanges. It also adds NDT testing cost and is a more expensive weld. I would tend to agree since there are 40 stiffeners times 2 welds (top and bottom) for a total of 80 full pen welds.
The client says full pen welding provides better bearing and there shouldn't be any distortion with 1" thick flanges. I am not sure how he arrives at his conclusions.
This would seem to confirm my thoughts as well.
http://www.highsteel.com/technical_resources/faqs/...
I am curious what other engineer's experiences are?
Thanks
The client says full pen welding provides better bearing and there shouldn't be any distortion with 1" thick flanges. I am not sure how he arrives at his conclusions.
This would seem to confirm my thoughts as well.
http://www.highsteel.com/technical_resources/faqs/...
I am curious what other engineer's experiences are?
Thanks





RE: Full Penetration Weld at Bearing Stiffeners?
Mike McCann
MMC Engineering
RE: Full Penetration Weld at Bearing Stiffeners?
RE: Full Penetration Weld at Bearing Stiffeners?
Maybe this would be the case where the lesser of two weevils would govern the detaining. Or hire an Architect to provide a better cladding detail...
Mike McCann
MMC Engineering
RE: Full Penetration Weld at Bearing Stiffeners?
RE: Full Penetration Weld at Bearing Stiffeners?
Don't worry about the cost, the client is willing to pay.
RE: Full Penetration Weld at Bearing Stiffeners?
RE: Full Penetration Weld at Bearing Stiffeners?
Bridgebuster I assume you mean don't worry about cost IF the client is willing to pay? I don't like wasting taxpayer dollars on stuff like this. I just don't see the reasoning for full pen welds. I always think of full pen welds for moment connections or where you need that kind of a strength in a weld. That kind of strength simply isn't needed and I don't see the reason to take the risk of screwing up 900,000 lbs of plate girders.
Oh well screw it. It's their bridge they can take the blame for their decisions.
RE: Full Penetration Weld at Bearing Stiffeners?
RE: Full Penetration Weld at Bearing Stiffeners?
RE: Full Penetration Weld at Bearing Stiffeners?
Additionally it states "However, it is advantageous to avoid a full penetration butt weld, because shrinkage strains (vertically) will distort the transverse profile of the flange and cause misfit of the bearing." This is also the recommendation of AISC's National Steel Bridge Alliance.
Like I said previously, it's an invitation to warp the flange and hence an unnecessary risk and adds fabrication cost. We are spending other people's money here, why waste it?
Bridgebuster - The full pen weld between to flange plates is necessary to develop the full strength of the steel on either side of the weld. There is no such requirement for a bearing stiffener in compression.
Every full pen weld has to be inspected. Why add an additional 80 weld inspections when there is simply no justifiable engineering reason to do so? The decision is being made out of ignorance. As engineers we should be able to justify every decision we make with a better reason than "because I say so".
However, I have no choice but to obey the client's decision.
RE: Full Penetration Weld at Bearing Stiffeners?
BTW - Don't try to justify every decision by citing a code or theory. There will be times when all you have to go on is your gut feeling. [smile]
RE: Full Penetration Weld at Bearing Stiffeners?
There have/will be plenty of times in my career where citing my gut as a reason for doing something will never cut it when asked by a superior to justify my reasoning. The lack of curiosity by some engineers is frankly disturbing.
You are correct though, I'm going to comply with their desires.
RE: Full Penetration Weld at Bearing Stiffeners?
Fabricators have their preferences. DOTs have theirs and they usually consult industry people so as not to create undue burdens. Why not ask your client the reason for the change in policy? The guys at High Steel are smart but you're also implying your client is stupid, no less smart.
I've worked both sides of the fence - design & construction - no one knows everything. And sometimes we just have to wing it - gut instinct.
RE: Full Penetration Weld at Bearing Stiffeners?
You probably can squeeze more material out of the girders to offset the cost of the welds. Like bridge buster said, one fabricator won't mind doing it while others will.
RE: Full Penetration Weld at Bearing Stiffeners?
The client's justification was that this is how it's shown on their bridge standards for rolled beams and you get better bearing with CJP welds. I have no idea if this is a change in policy as they have no written policy, no design manual or anything. They change things frequently, but those emails are not circulated to the consultants. Generally the only way you know of changes is after a plan review.
So yes I get bent out of shape because things change arbitrarily. Then I ask questions and I get responses like that's why we have the AASHTO bridge code. However, they don't always follow the code. Now do you understand my frustration?
The owner at my first job out of school taught me something I'll never forget. When being deposed by a lawyer it's best to have a reason why you did something.
RE: Full Penetration Weld at Bearing Stiffeners?
Here's something to think about....
"Structural engineering is the art of molding materials we don't wholly understand, into shapes we can't fully analyze, so as to withstand forces we can't really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." ...Jim Amrhein