Long-slotted and short-slotted?

[ForrestLowell]

AISC 13th edition (Black book) pages 16.2-21 states that short slotted holes can be used in both plys of a SC connection. it also states that a long-slotted hole can only be used in one ply of the SC connection. My question is, can I use a long-slotted hole in one ply and a short-slotted hole in the other ply of a SC connection? Anybody with experience in this?

Thanks for the help,

Forrest

 

[Stillerz]

Is there some extenuating circumstance requiring the use of long slots in each ply in your case.
I am mostly just curious.

 

[ForrestLowell]

Kind of, bolt spacing is such that I can only slot 1.5 inches in one ply which is greater than the short slot distance for the 7/8" bolt so I have to classify it as a long-slot. The tolerance on my girt lines are tighter than my column tolerances, and there are few places where it needs to be moved more than my 1.5" slot will allow. up around elevation 70' or so.

 

[Stillerz]

I guess it might help to fully explain where the connection is and what it is for exactly.
I am having a difficult time understanding the situation.

 

[paddingtongreen]

Question: why are you classifying a girt connection as slip critical? The connection is secondary, you can require the bolts to be fully torqued without declaring it an SC connection. Use plate washers over the slots.

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

 

[cntw1953]

forrest:

Regardless of your application, this is an interesting question worth to understand. Can you post a sketch with space constraints and direction of intend member movement.

I doubt the code would permit it, but maybe there are other alternatives.

 

[Stillerz]

I was just short of saying what Paddington said here. I dont see the need for SC connections on girts....unless for some reason the owner wanted them.
I would also think that if the SC is specified here it would be for servicability, not strength.

 

[ForrestLowell]

The Facility is a process building for certain hazardous materials which due to certain requirements imposed by the government client has the need for a very beefed up siding material which must withstand seismic and wind events in the elastic stress range. So for this problem the strength of the connection is a calculated and required. The basic issue is if you were to be bolting two plates together could you put a long slot in one plate and a short slot in the other plate, both in the same direction and in the direction of loading. A similar question would be, what type of hole is required in the other plate if a long slotted hole is used in one plate? Could you even use a oversized hole? Or would you have to use a standard hole? In general I am using 7/8" A325 high strengh bolts, but there are locations where I am using 1-1/8" A490 bolts. Thanks for the ideas!

Forrest

 

[iponom]

No long slots in the direction of loading! (16.2-21)
What is the purpose of both of your long slots, does that have anything to do with erection? Can't you get away with one ply STD and the other LSL?

 

[iponom]

Sorry did not realize the seismic/wind part. so never-mind the comment about the direction of loading..

 

[Stillerz]

Well, in reading 3.3.4 on page 16.2-21 of AISC 13, it looks liked for SC connections, a long slotted hole is only allowed in one ply.
For a 7/8" dia bolt I believe a long slotted hole is
2 3/16" long. That should allow for a considerable amount of play. Again, a sketch might be some help.

 

[Stillerz]

iponom-
I do think you can use Long slots on SC joints regardless of direction of loading, no?

 

[iponom]

Stillerz

Yes. You are right!

Why would anyone need two long slots, or one SSL and one LSL? I am mean what kind of application would that be? In what I've dealt with there would always be a combination of STD and SSL/LSL.

 

[Stillerz]

Must need a lot of room for adjustment.

 

[ForrestLowell]

A single long slotted hole would work for me. But have 4 bolts arranged in a square only 2.5" between all bolts. Which means I cannot make a full long slot (cannot make a 2-3/16" slot with center to center bolt spaceing of 2.5") and keep the required clear distance to the next hole in the pattern. The maximum I can slot the hole is 1.5" to keep the required clear distance. That 1.5" is greater than a SSL so it has to be classified as a LSL. Slotting the hole in one direction 1.5" allows me to move the member about 9/16", I need a total movement of 3/4" to be in alignment so if I could SSL the other plate I would able to move it the additional 3/16" need for fit up. I will work on a sketch to upload to clarify, but it might be tomorrow.

 

[iponom]

Stillerz

How much room is that? I mean, ~2 in. for every connection in the siding... sounds a little bit crazy, but what do I know...

 

[Stillerz]

well, with a 2 3/16" slot with a 7/8 bolt buried to one side of the long slot you'd have 1 5/16" of play (the bolt could slide back and forth 1 5/16")
No doubt it is a lot. Sounds like he has a connection that requires a lot of capicity but with limited room to work.

 

[iponom]

So why are the bolts spaced at 2.5"? couldn't you be the normal guy and space them at 3? I figure they are already fabricated eh?

 

[ForrestLowell]

That is a correct assumption. I am in resident engineering group which addresses construction problems, our building is the size of several football fields so they have quite a few of these girts that need to be adjusted. and they really don't want to abandon the holes and weld them where needed, that costs a lot more money. Reeming out the holes and put plate washers in place is relatively simple and quick. Most of the girts can be adjusted using the 1.5" hole, but there are few that I just go word they are going to abandon the holes and weld it where required.

 

[iponom]

Could you perhaps increase/reduce the bolt size, and use more/less bolts respectively, and use the full LSL for their respective bolt size?