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Up Topic Welding Industry / Technical Discussions / Question about mixing welding and bolting
- - By jwright650 (*****) Date 10-24-2013 15:00
I've seen this on at least two large structural jobs this past year as they went through our shop. I've asked questions about this joint each time and have been brushed off due to the fact that by the time these drawings making it out to the shop they have to be fabricated and loaded to be erected in sequence.

What I have are moment arms(WF outriggers) welded full pen at the flanges only, then the web is trimmed back about 1" and holes are punched in the beam web, A shear tab is punched with horz short slots and fillet welded to the main member and bolts fully tensioned to the web of the outrigger.

What is the advantage of fabricating this way with a short shear tab and bolts in the slotted connection that is fully tensioned vs leaving the web long and welded with a fillet weld to BS of the web?

I see no purpose in all of that extra work to connect the web of the O/R to the main member.
Parent - By jwright650 (*****) Date 10-24-2013 15:02
If my description isn't clear...I will try to upload a drawing in a few minutes. I have to go UT some other crazy looking connection right now and people are waiting on me.
Parent - - By welderbrent (*****) Date 10-24-2013 15:06
John,

Normally the bolting is done first to locate the stub beam and then when all dimensions have been verified the moment welds are done.  It is a quick way for the shop to do the fabrication that will set up the connection for the field erection.  This hole process is easier for the shop to accomplish than for the field to do it. 

The strength is in the moments with the bolting really being more of a fitters aid.

Have a Great Day,  Brent
Parent - - By jwright650 (*****) Date 10-24-2013 15:49
Brent,
See that would be great(speaking of the fit-up for the erector), "IF" this was a field welded moment, but this is all done in the shop and in my opinion it wastes alot of time.

There is alot of time invested preparing the ourigger and shear tabs (sometimes double angle knife connx) and providing slots/torquing bolts and all that jazz.  I can't see how it adds any value to the structure when all this is done inside our shop and I'm keeping an eye on the fitup for the moment welds and all of that. All it does is eat up man hours and waste plate material/bolts.

If we leave the web of the O/R long and run it into the web of the main member, fillet weld the web on both sides, the piece is locked into position, the fit up for the full pen is verified and the moment welds are placed. I come along and UT those flanges and make sure all is well, it gets cleaned up and off to paint it goes and then loaded.
ie. clean up = cutting off the run-off tabs, grinding up the ends to providing the proper contour, etc.
Parent - - By SCOTTN (***) Date 10-24-2013 17:27
John, I agree.  I don’t see any advantage to bolting and welding this moment connection in the shop.  I see it running up the shop's MH's for the project, as you've said.  I agree that the advantage for this type of connection would be in the field, but definitely not in the shop.  Maybe this was just something your detailer decided to do without consulting your shop as to their preference, or, when his/her detailing program encounters the need for a moment detail to a supporting member's web, the detailing program automatically defaults to a bolted connection to the supported member's web and CJP welds to the supported member's flanges.  Just a thought.
Parent - - By jwright650 (*****) Date 10-24-2013 18:12
New detailer(to us). So this outfit is still figuring us out and what we need. So I'll give them that and cut them some slack. The other prject had the same issue, but it was with column moment arms and they had double angle knife connections at every full pen outrigger. I'm familiar with Texas T's but never seen all of this work done to bolt the web first and then weld the flanges.
I'm on my 29th year with this company and never seen this before until this year..different projects, different detailers, different EORs. The head guy back in estimating was out in the shop yesterday looking around after the shop had gone home and I was still here doing paperwork...he asked why did we(as a company) let the detailer do this? I shook me head and reminded him of the other job that recently went through with similar connections.
Parent - By SCOTTN (***) Date 10-24-2013 18:33
The problem I see with computer generated drawings is that jobs are being detailed by some people who have more computer experience and knowledge than they have steel experience and knowledge.  To further complicate things, as you know, all fabricators basically have to adhere to the same codes and specifications, but each fabricator has their own preferences for the way their shops are set up, and how they want to see things on drawings, so detailers have to alter their program to match those needs.
Parent - - By welderbrent (*****) Date 10-24-2013 19:45
I agree with several points that both you and Scott are making. 

The main thing I see, I can prep and place with fillet welds a connection plate faster than most can do an additional CJP, UT it, and possibly repair it or at least a percentage of them. 

But, you are correct in that it is usually a judgement call for what the fabricator prefers and the EOR is going to let them do it however they want to.  In the last 5 years I have seen them done both ways.  In the past year, I saw them done both ways on the same job.  It all depended on the location, angle of the stub beam, type of connection/incoming beam purpose, size of the stub beam (obviously, the heavier the beam, the thicker the web and more time for welding and more risk involved for UT), and many other factors.

If your company didn't like it and feels that way is slower, change it.  Should not be a problem.

Have a Great Day,  Brent
Parent - - By jwright650 (*****) Date 10-24-2013 20:41
No full pen at the web(at least in this case), just a double sided fillet weld is all that would be required.....so no UT of the web. These are only transmitting moment through the flanges. So all of this extra work to fab plates up, fit them, bolt them and torque is pure wasted time and effort. They even put slots in the tab plate for adjustment...what the heck is going to be adjusted? It just doesn't make any sense to me.

My fitter gets the overall length of the o/r from the centerline of the main member off the drawing out to the end of the o/r...subtracts the half web of the main member off the web of the o/r, subtracts half flange off of flanges of the o/r and bam...you're done... fit/tack together, verify the over all is correct, verify the root is tight and weld the double sided fillet weld at the web, weld/back gouge, re-weld flanges and it's completed and waiting for me to UT the flanges.
Parent - By Lawrence (*****) Date 10-24-2013 21:39
John,,

I have an article entitled: Strength of Joints that Combine Bolts and Welds;  by GEOFFREY L. KULAK and GILBERT Y. GRONDIN

Published by the Engineering Journal.... Its over my head with the equations... But maybe you will find it interesting..

PM your email...  I lost yours during my late transition.

Lar
Parent - - By welderbrent (*****) Date 10-25-2013 13:10
What I have often seen in similar cases is that that was intended to be a full beam connected in the field.  For whatever reason, the detailer, with or without consulting the fabricator, makes it a stub beam thinking it will be easier to connect to out a couple of feet from the Column, or primary beam, and place the remaining part of the beam in the field and welding the full pens at the shop where there are a good many factors that are easier to control than in the field.

Is it?  Sometimes yes, sometimes no.  It all depends upon so many variables.  I don't think any one can make a definitive statement either way. 

But, there needs to be good communication between fabricator, detailer, engineer, and erector in order to make a job flow as easy as possible for all parties. 

Remember also, when some changes occur that may take the shop longer, they need to say so at the beginning and get more money if it is to be left that way.  If it was bid one way per the original engineer submittal package, additional costs may be added if the engineer and detailer change things that cause more work on your behalf.  If there is good reason for it they will accept that and still proceed.  If they don't, it will revert back to the original submittal details. 

Either way, you have it in writing as to what they want and why.

Have a Great Day,  Brent
Parent - By jwright650 (*****) Date 10-25-2013 13:28
Brent you hit the nail on the head when you mention communication between all of the parties involved. That becomes a problem often times due to the EOR is on to bigger and better things by the time these pieces travel through the shop and it's tough for them to recall projects that they worked on several months to a year ago. I liked it when we utilized local sub contract detailers and our own in-house detailers because we could get answers within minutes of discovering a problem vs days later. Communication is a problem and tough to get everyone involved in the same room to discuss these things. We have a detailing manual that the detailer is supposed to use, but I often hear that they don't have money in for redoing their software setup to accomadate our standards. Another problem when accepting the lowest bid....
- - By 803056 (*****) Date 10-24-2013 22:30 Edited 10-25-2013 02:53
If I understand the details of the connection being described, it looks seething like the embedded sketch. The sketch only shows the column flange (to the left) and the lower flange and lower half of the beam web connection (to the right). I would not be surprised to learn there are web stiffeners opposite the beam flanges.

The moment connections consisting of the top and bottom flanges transfer the load into the column flange. Stiffeners, if used,  would provide stiffness to the column web to prevent crippling and provided continuity to more effectively transfer load to the opposite column flange.

The problem arises from the complete joint penetration groove welds in the top and bottom flanges of the beam to column flange. Te stresses that develop as the CJP groove welds cool would be maximized if the beam web butted tight against the column flange. The presence of a gap between the end of the beam and the column flange and the short slot holes allow the welds to cool and contract without producing high residual stresses in the through thickness direction through the column flange.

The potential for lamellar tearing in the column flange is reduced by minimizing restraint in the through thickness direction. The short slotted holes accommodates some movement as the CJP groove flange welds cool to ambient temperature. Shear loads are transmit by the web connection. Whether the web is bolted or welded makes little difference relative to the sear capacity of the web. However, if the beam web butted tight to the column flange it would result in a substantial increase in the residual stress developed by the connection. Consider for a moment that the potential stress in the through thickness direction could potentially be increased by an amount equal to the cross section of the beam web times the base metal yield strength in the region most susceptible to lamellar tear, i.e., the region where the column web and column flange join.  

I am not saying that is what the detailer was thinking of when detailing the connection, but it is something I would consider. My level of concern would increase exponentially  as the size and thickness of the members (column and beam) increased. Greater cross sectional area means higher degree of restraint and increased potential for lamellar tearing where the column web and column flange join just opposite the CJP flange to column welds. The potential, due to increased restraint if web stiffeners are present, for lamellar tearing increases.

Best regards - Al
Attachment: AccessHoleswBacking19-Sept-2013.dwg (25k)
Parent - - By 99205 (***) Date 10-25-2013 02:04
Is this D1.8 work?
Parent - By jwright650 (*****) Date 10-25-2013 11:15
Hi Doug,
No, this is all D1.1 work.
Parent - By jwright650 (*****) Date 10-25-2013 11:28 Edited 10-25-2013 11:30
Al, this is similar but we don't use backing bars in the shop unless it is requested by the EOR, if we have access to the backside, it gets back gouged and rewelded. That allows us to use a zero - 1/8" root to keep the shrinkage to a min vs a 1/4" wide root to allow access to the root and backing bar. Al, your sketch is very similar to the columns I saw a few weeks ago where they used double angles(knife connx), but these current situations are beam to WF o/r welds and they use a shear tab fillet welded in the web and bolted. No opposing stiffeners, or anything else....just a moment arm sticking out off the flange or out of the web of the main member. Most of these are less than 3 feet long, W18x35's and W24x55's so it isn't anything heavy, no jumbo sections or anything out of the ordinary. Most of the o/r's are the same section size as the main member, a few of them are shorter in depth than the main member so the bottom flange of the outrigger gets full pen to the web in those cases. Even in those cases, there aren't any opposing stiffeners in the far side of the main member.

Here's a crude sketch, top is what is detailed, bottom is what I am used to seeing.
Attachment: 20131025072208.pdf (32k)
Parent - - By jwright650 (*****) Date 10-25-2013 11:45
Hi Al, I guess the whole thing that had me scratching me head about this is the fact that the shear tab is fillet welded to the web.....so it doesn't seem like there is any difference in welding a shear tab, prepping for a bolted connx, vs just welding the web to web via a fillet weld...either way the forces are transmitted/resisted by the fillet weld into the web whether it's a shear tab or an o/r web.
Parent - - By SCOTTN (***) Date 10-25-2013 12:09
The only difference to me would be the cost of making the shear tab, the cost of the fasteners, someone gathering the bolts and the shear tab, and the full tensioning of the bolts.  The fitting of the shear tab to the main member vs the fitting of the outrigger to the main member should offset each other, unless I'm missing something.
Parent - - By jwright650 (*****) Date 10-25-2013 12:30
....and another small difference is that the fillet weld is now off center in the web by half web of the o/r vs centered in the web....LOL
Parent - - By SCOTTN (***) Date 10-25-2013 12:54
You might want to re-think this John.  Being that FAR off center, and considering the static equilibrium of the balanced force imposed on the outrigger, it will most definitely negate the assumed load transfer for a symmetrical pattern where the instantaneous center line will now be located on the X – axis.  When the applied load passes through the center of gravity of the connection, the load can only then be assumed to be distributed equally. More importantly, while the vector analysis is based on elastic theory, the factor of safety with respect to the ultimate load capacity is still quite variable, rendering the outrigger essentially useless and serving no useful purpose.  I would highly recommend omitting it entirely.  There's a 50-50 chance that they won't even realize it's missing in the field. Now if you’ll excuse me, I’m going to get back to reading The Attention Deficit Disorder Association's Book of Wild Animals of North Amer-Hey! Let's Go Ride Our Big Wheels!"
Parent - - By jwright650 (*****) Date 10-25-2013 13:00
:lol: :lol: :lol: :lol: ...Here, ....hold my Pepsi and watch this!
Parent - By 803056 (*****) Date 10-25-2013 22:44
Your sketch shows the stubs welded to the flanges of a beam.  Lamellar tearing is not a serious concern, so your guess is as good as anyone's guess.

Al
Parent - By ssbn727 (*****) Date 10-29-2013 06:23
BEAM ME UP SCOTTY!!!:yell::lol::yell::grin::twisted::wink::cool:

Long time no read! You've been that busy eh?

I'm glad to see you posting again, and you will definitely bring back the happy humor you always seemed to share with us again and again!!!
WELDCOME BACK SCOTTY!!!

Respectfully,
Henry
Up Topic Welding Industry / Technical Discussions / Question about mixing welding and bolting

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