What is the load on this cantilevered channel?
What is the load on this cantilevered channel?
(OP)
Based on my sketch at the top of the attached page and the data given on the Vendor's chart....What is the MAXIMUM weight that can be supported by the channel? What would you do make this installation stronger?
I'm not a structural engineer or designer.
I'm not a structural engineer or designer.






RE: What is the load on this cantilevered channel?
RE: What is the load on this cantilevered channel?
RE: What is the load on this cantilevered channel?
Simple, hire a structural engineer.
Maine EIT, Civil/Structural.
RE: What is the load on this cantilevered channel?
how'd you make it stronger ? it's impossible to answer sensibly without knowing the constraints. another fastener into the 10" I-beam might help (if this attachment is critical), another supporting brkt from the cable trays, a support on the LH side of the cable trays would be great, change on material on the channels, ... depends on what is the critical loadpath.
also, it's much better to ask can this support X lbs. the best way to determine "maximum" is to test the final installation, but analysis for X lbs would be very straight forward.
Quando Omni Flunkus Moritati
RE: What is the load on this cantilevered channel?
I thought, actually hoped this would be a straightforward calculation. And one of you structurals could knock out in second. It is obviously basic statics that every engineering student had his 2nd year of college.
More information....there is one of these double trapeze supports every 8 ft. Each level supports a 12" aluminum cable tray that weighs about 65lbs per 20' piece. And each tray has two #4/0 triplexed cables that weigh about 3.5lbs per foot.
So for a 20' section, there would be 2 supports, and the weight would be (2 X 65lbs) + (4 X 3.5lbs/ft X 20ft) = 410lbs/20'
RE: What is the load on this cantilevered channel?
RE: What is the load on this cantilevered channel?
RE: What is the load on this cantilevered channel?
Don't come here with a poorly worded question with a shoddy sketch and expect reasonable answers. Had you worded your original post with the information that you included in your second post you probably wouldn't have gotten as many smart ass remarks.
RE: What is the load on this cantilevered channel?
What worries me a little bit is that these supports are done all over the country every day but not by iron workers but by electricians. And they aren't hiring structural engineers, they are slapping them into place. They usually have a "standard" detail to work from that was probably originally prepared by a structural engineer, but not all real situations fit that "standard" detail. The electricians make the call on where and how to do the support. A little background on how this calculation is done would help give some assurance that what they are doing is right.
Ok I'm done now.
RE: What is the load on this cantilevered channel?
1) how many of these 20' sectiona are there ? is it a one off or a continuous tray ??
2) but the double trapeze are 8' apart ... does that mean that 1 20' cable tray is support by two supports 8' apart ?
3) if so, then if 20' weighs 410 lbs, then each support is carrying 205 lbs.
4) based on your sketch, 75% of the load goes to the LH support, and 25% to the RH one
5) 5/8" threaded rod is good for this load
6) the upper beam (B22A section ??) is taking this load into the I-beam. it sees two loads, 42" apart, and reacts them where it connects with te I-beam (not well defined). the maximum moment in the channel beam is at the LH support. since it's about 6' long, you should include the weight of the channel, about 24 lbs, as a distributed load.
7) how do the attachments to the I-beam feel about the load applied ? probably not a problem, but a question that needs answering.
8) how will the I-beam feel about he loads applied ? again, probably not a problem, but ...
9) this response started when you wee able to define a load requirement, rather than asking what the maximum is.
10) if you don't like our free answers, you're welcome to ask someone else ...
Quando Omni Flunkus Moritati
RE: What is the load on this cantilevered channel?
rb1957 gave a good idea of some of the devils in the details. You're right that giving a load capacity for the horizontal "trapezes" is simple if all you're worried about is its plastic bending capacity, if we have the steel yield strength (which isn't on the sketch.) Other concerns are connection details (top trapeze to bottom trapeze, connection to top channel, connection to I-Beam), etc. Connection design isn't quite so back-of-envelope. Neither are local-buckling conditions for that shape.
RE: What is the load on this cantilevered channel?
The cantilever length is reduced to 32", so the moment is 32P"# where P is the hanger load in pounds at the end of the beam.
The section modulus S is 0.5989 in3 and the working stress is f = M/S. Assuming a working stress of 20,000 psi, B22A would be capable of taking a moment of M = f*S = 20,000*0.5989 = 11,978"# provided it didn't buckle before that. Recalling that the moment arm is 32", this means that it could carry a force of M/32 = 374# by that calculation.
It would be necessary to consider the buckling capacity of member B22A which I do not have at my fingertips. Maybe the best way to determine that is to load it to failure and see.
BA
RE: What is the load on this cantilevered channel?
RE: What is the load on this cantilevered channel?
BA
RE: What is the load on this cantilevered channel?
For what it's worth, Unistrut offers a similar shape with much better design information.
The closest equivalent is a P1001, good for 14360 inlb. This is based on a 42ksi steel member with 2.0 FS.
It's interesting to me that nobody has mentioned deflection, especially when the question was well defined. When asking, "How much can it hold" deflection may be the governing factor. I`m guessing it doesn't matter in this case.
To BDN: If an electrician installed one of these and then overloaded it, I believe the response would be, "eh, he guessed at the wrong size". You asked a group of professional engineers who could be accepting some liability simply by answering a vaguely worded question on the internet.
If I needed to re-wire my house and asked my neighbor to help and my house burned down, it would be my fault.
If I asked a professional electrician to help and my house burned down, I`m not sure I'd accept that same responsibility.
RE: What is the load on this cantilevered channel?
but you probably wouldn't do it unless you thought there were going to be problems.
i guess this is typical of "build first, analyze second" projects.
looking quickly at things, i'd suggest testing ... easy enough to do, test to load*safety factor. rough numbers say it's unlikely to have a SF = 2.
Quando Omni Flunkus Moritati
RE: What is the load on this cantilevered channel?
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: What is the load on this cantilevered channel?