Hollow Structural Sections used as a girder 1

[polskadan]

Hello all,

I am currently reviewing connections for a fabricator and have a unique connection that I have never run into before. Although I have some avenues of thought of how to analyze this connection I want to see what others think are the controlling local issues that should be checked/analyzed (I cannot find any literature on my specific type of connection argh!)

I have an HSS rectangular tube that is being used as a girder. This means that I have: (1) several shear tabs going into the side of the HSS tube walls throughout the length of the member and (2) a double angle connection at the end of this girder that will attach to another girder (not HSS). This connection consists of two through bolts that that go through the HSS to connect both angles. The top of the girder at the connection points is also coped meaning there is not top flange at the shear connection. One equation that I must use for certain is Bolt Bearing on HSS for through bolts which can be found in AISC pg 7-13. Besides this however these connections are unique in the sense that the shear force does not go parrallel to the axis.

I would appreciate any input on the matter! Thank you in advance!

 

[hokie66]

I don't like the sound of through bolts for a shear connection, especially with the HSS coped at that point. Sounds like the connection should be welded to the HSS, possibly make it an end plate. A sketch with sizes and forces would help.

 

[paddingtongreen]

I agree with hokie66, but if you must go ahead with it, put pipe spacers between the walls of the HSS.

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

 

[SAIL3]

can not tell from your post wheather it is a bm or a girder....if designed as a girder..check h/t value for the need of web stiffeners..this is one of the problems in using closed sections as girders..may end up putting stiffeners on the outside and extending the flanges...

 

[BAretired]

When using a shear tab, do the supported beams require lateral bracing at the support point by code? I think there was something about that in a recent thread but I can't remember where I saw it. If that is the case, maybe an angle would be better than a shear tab.

BA

 

[connectegr]

Not a very good selection for a beam/girder but I see it frequently. Where beams are connected to the side of the HSS girder, are connections located on both sides? Connection eccentricity must be considered. Also consideration of torsion in the girder end connection, may be necessary. As mentioned above, I too don't like through bolts for structural connections. This is not allowed per RCSC. For HSS end connections, I usually provide and endplate with vertical shear plate. If torsion is an issue, the double angles may be required. I would shop weld them to the HSS, and field weld to the support or "hollow-bolt".

http://www.FerrellEngineering.com

 

[polskadan]

Thanks all for your help, definitely got the ball rolling on some avenues of thought. However bizarre the connection may be, by AISC standards through bolting is permitted in shear connections if the connections does not require a fully tensioned installation (aka slip critical). It's for this reason I did not want to completely disregard the shop drawings for this connection that I have received to review. I appreciate all the help and now believe I have all the 'local' issues covered!

 

[connectegr]

Where in AISC is through bolting allowed, other than as an erection aid? RCSC does not allow for any non-steel fills, within the plys of a connection. The air within the HSS walls would definitely be non-steel. This requirement apply for snug-tight or pretensioned bolted joints. Non-steel fills can result in bending or moment on the bolt, for which it is not designed.

http://www.FerrellEngineering.com

 

[polskadan]

AISC 7-13. For this type of connection it is typical to put a pipe or sleeve in between the walls of the HSS to prevent flexing of the HSS walls. This should alleviate concerns about bolt bending, however this might not be necessary provided you do a local check on the bolt

 

[connectegr]

Thanks for the reference. After your post I contacted with Dr. Packer, Design Guide 24. He confirmed that through bolts are acceptable for these shear connections. I have avoided them in the past, but apparently the concern has been difficulty installing the bolts. Sorry for the confusion, I was mistakened. 8

http://www.FerrellEngineering.com

 

[Ron]

I was mistakened.

connectegr,
This is rare! Not that you admit it, but that you were mistaken. You give some of the better connection advice I see in here.

Ron

 

[BAretired]

Yes indeed, Ron.

BA

 

[connectegr]

It is hard to argue with Dr. Packer regarding HSS connections. So I differ to those much more wise than myself. He says he does not like this connection detail and that it is not allowed by CISC. But, as mentioned AISC 7-13 does allow the use of through bolts for shear connections. And the same reference is given in Design Guide 24.

Ron & BA
I appreciate the vote of confidence.

http://www.FerrellEngineering.com

 

[hokie66]

I would dare to say that AISC is wrong. But then I don't have to deal with them, and at any rate, I design my own connections, so don't have to argue with a connection detailer.

 

[connectegr]

Hokie
I think you Australians (if I recall) also prohibit through bolts. And I still have hope for you delegating connection design someday.

http://www.FerrellEngineering.com