UNISTRUT Knee Bracket Design

[cgstrucg]

Hello,

I have to design a 4ft long unistrut bracket for very small loading (50 lbs). I have previously never worked with unistruts so please excuse this stupid question. I see that unistrut website has predefined brackets but none are as long as 4ft. So I have to use 2 unistruts - One horizontal and one diagonal to complete the bracket. I see that this small load is nothing for a unistrut (P1000) but what about the lateral load. This bracket is going to support an air duct and I want to check brackets lateral load capacity for load as small as 5psf. Is there a way I can cross-check it?

Thanks

 

[Agent666]

Just put another strut in horizontally on the diagonal for the lateral load (on the assumption the bracket is attached to a wall), without a sketch of the bracket, unistrut orientation, what it's attached to, its hard to say exactly.

If another strut to deal with lateral loads isn't an option just take the section properties and check it by hand to whatever code applies in your location. I've always found the unistrut guys pretty good, they'll design something for you if you simply give them the loads in this part of the world. If required they can also weld something up, so you aren't limited to their connection hardware.

 

[cgstrucg]

I am located in Philadeplhia. I can't use any other lateral unistrut because of location. The sketch is attached. I am still not sure as to how I can check it's lateral capacity as I don't think standard AISC codes apply for them and I can't locate any Unistrut design guideline.

 

[cgstrucg]

Can I simply use 2 P-1000 (

https://www.unistrut.us/product-details/p1000

as a knee bracket connection?

 

[KootK]

Can I simply use 2 P-1000 (

https://www.unistrut.us/product-details/p1000

as a knee bracket connection?

Sure, you just need to find a convenient way to connect everything.

I am still not sure as to how I can check it's lateral capacity as I don't think standard AISC codes apply for them and I can't locate any Unistrut design guideline.

Short of welding the unistruts to the supports, I'm not sure that you'll be able to have any real lateral capacity (perpendicular to bracket). And it will be about your connections rather than the unistrut pieces themselves. I don't know of any conventional uni-strut connections that would get you strut fixity out of plane at the supports (I'm no unistrut expert though).

just put another strut in horizontally on the diagonal for the lateral load (on the assumption the bracket is attached to a wall)

This would be best were it not for this if I'm interpreting it correctly...

I can't use any other lateral unistrut because of location.

Some questions:

1) Are you sure that there really is a meaningful lateral load on this? If not, perhaps the duct itself could be the bracing.

2) Is there room to attach things to the sides/flanges of the channel?

3) Is there a run of brackets such that you could run some struts perpendicular to the bracket and get your bracing further down the run where there might be space for such bracing?

I do have one idea for nominal moment capacity that might not be too bad...

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[cgstrucg]

Hey Kootk,

I am doing a hybrid of what you mentioned above. See attached.

Unistrtut has clips which can connect these struts together. I added that add. strut at top so that I can get a bit of lateral restraint. Lateral load is not at all high. It's just for caution. Also, there is going to be a saddle strap (for duct) attached to the top of that add. strut.

I think this will work perfect.

 

[CrabbyT]

The Unistrut General Engineering Catalog has section properties for each strut section. See pages 24 and 25 for the orientation of the axes and the properties listed below.

P1000
A = 0.555 in²

I_1-1 = 0.185 in⁴
S_1-1 = 0.202 in³
r_1-1 = 0.577 in

I_2-2 = 0.236 in⁴
S_2-2 = 0.290 in³
r_2-2 = 0.651 in

P1001
A = 1.111 in²

I_1-1 = 0.928 in⁴
S_1-1 = 0.571 in³
r_1-1 = 0.914 in

I_2-2 = 0.471 in⁴
S_2-2 = 0.580 in³
r_2-2 = 0.651 in