Loose gusset plates...

[lovethecold]

A supervisor just informed me that one of our techs was in the field checking on the torque of some bolts. The tech noted at some of the connections the gusset plate did not but up tight against the member being connected to. He said at some of these connections only a couple threads of the nut were holding the beam up. Apparently the construction company was going to get longer bolts. This is for a prefabricated metal building.

I adamantly disagreed with this and told the supervisor that these connections should not be allowed to pass. He seemed to think that the longer bolts would be acceptable. He figured the gusset plate could be 'bent' into place. As a former structural welder we periodically had to make field repairs when a gusset plate did not but up tight against the other member. Such an incident as noted above would never have been tolerated.

Would any of you find this acceptable? If not, can you explain the how much the allowable load may be reduced by?

What might be some acceptable alternatives (aside from the obvious - call the structural engineer of record)? The building is a prefabricated metal building. It sounds like this is a small construction outfit in which I doubt they have the competent field personal to cut the existing gusset plate off and reweld a new one on properly.

Nobody at my firm are structural engineers. The closest we have is a materials engineer.

Thanks for any input.

 

[paddingtongreen]

I would call the Prefab company that supplied the building. You are correct in that it should not be accepted, bolts are not supposed to carry bending moments.

Timing has a lot to do with the outcome of a rain dance.

 

[kelowna]

Not acceptable.

A filler plate could be installed between the gusset plate and the member to close the gap and subject to the engineer's approval.

 

[JAE]

I would get the question put to the engineer of record (the building mfr's engineer most likely).

I'm surprised that you were checking torque on bolts on a pre-engineered metal building as I would have thought that all the connections would be bearing type connections only. But even with bearing connections, the plys of connecting surfaces should be in contact. With the longer bolts, perhaps they can snug them up tight.

 

[Ron]

Fit-up is an important parameter. This is not acceptable.

As JAE noted, they might be able to pull the space out by tightening longer bolts, though if they can get the threads started on the bolts they have, they should be able to do the same.

Not sure of this case, but I know of counties and municipalities that require bolt torque on "pre-engineered" metal buildings.

Don't ya just love that term..."pre-engineered" as if other buildings were not "pre-engineered"!!

 

[msquared48]

JAE:

I have had to check bolt torque on these buildings too, both turn of the nut, and to a specified torque with a calibrated wrench.

Mike McCann
MMC Engineering

 

[audeuce02]

Unless it is in SDC D or there are dynamic loads such as cranes, I would expect either snug tight or turn of the nut method for bolt tightening. Calibrated wrench is a touchy subject, because most PEMB connections do not require washers and the bolt/endplate configurations do not work out for the skidmore.

 

[Stillerz]

Get some longer bolts and crank 'em down.
You're not building a piano here.

 

[JLNJ]

Is this a girder splice? It seems a little tenuous if all that is keeping the roof in place is "a couple of threads" on the bolts. I would also like to see the members supported rather than simply drawn together if the gap is large.

 

[paddingtongreen]

The code does allow for a little "inelastic" fit-up of clip angles, in fact, it relies on them for beam end rotation.

If these are A325 bolts, the longer bolts may not have enough thread when the clips are pulled up. But the gap must be closed.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Tomfh]

How big is the gap?

 

[lovethecold]

Sounds like a gap of 3/4" to 1". The crew could only get a couple threads before they couldn't tighten the bolt down any more.

 

[paddingtongreen]

That's way too much to accept in my opinion.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[dicksewerrat]

They probably cross-threaded the nut too.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[youngstructural]

I was reading through all the posts, with exactly dicksewerrat's thought in mind: These bolts were almost certainly not installed correctly.... IF you can get a nut properly onto the end in this situation you can normally slowly bring the plates together simply by tightening each bolt fractionally in succession.

I agree with the voice of the (great) majority: Cannot accept as is, but likely can "fix" by bringing the plates together under longer threads... But watch out for more significant problems this may be symptomatic of! You really need to ensure you're not causing a problem with secondary stresses by forcing this tolerance to be "fixed" by pulling the plates together.

Cheers,

YS

B.Eng (Carleton), P.Eng (Ontario), MIPENZ (Structural-New Zealand)
Working in Canada, and missing my adoptive New Zealand family... at least I brought the little Kiwi with me!

 

[lovethecold]

I hadn't thought of the threads being crossed, which could explain the problem. After several responses I learned the contractor beleived they could snug the gusset plate in tight with longer bolts. As to the type of bolt, this I am unaware of.

youngstructural, you summed up the repsonses nicely.

Thanks all.

 

[zcp]

Any chance you could post a picture? It would be a great example for all coming behind.

ZCP

http://www.phoenix-engineer.com

 

[youngstructural]

I would really like to see photos as well, if at all possible...

Cheers,

YS

B.Eng (Carleton), P.Eng (Ontario), MIPENZ (Structural-New Zealand)
Working in Canada, and missing my adoptive New Zealand family... at least I brought the little Kiwi with me!