Trapeze problem

[EEC]

I am on a project where the contractor installed a trapeze strut rack for conduit. The rack is made from 3/8 inch all-tread, 3/8 inch mallable iron beam clamp, 108 inch piece of 1-5/8 by 1-5/8 inch 14 gauge slotted strut bolted in two places to a 108 inch 7/8 by 1-5/8 inch 14 gauge slotted strut. The rack is carrying 4-3 inch emt, 1-4 inch emt, 5-2 inch emt, 3-1-1/4 emt and 12 3/4 inch emt. The rack is already bowing in the middle without cable. What are the problems with this trapeze?

 

[Cow]

There are some weight and load specs in here:

http://www.power-strut.com/DB/PDF1/Power-Strut-Catalog_2008.pdf

 

[infinity]

Obviously if it's bowing you need larger strut or you need to add at least one rod in the middle. 108" is a very long span for 1 5/8" strut even with minimum loading.

 

[CONTROL FREQ]

Obviously if it's bowing you need larger strut or you need to add at least one rod in the middle. 108" is a very long span for 1 5/8" strut even with minimum loading.

ABSOLUTELY 100% CORRECT(imo).

 

[ACE1970]

Best thing to do is add rod to ceiling if possible, if not, Add larger strut but leave an over hang on opposite side of beam so it keeps it from bending or bowing idiots never think for future installations always do have some consideration plan for the future.

 

[iMuse97]

Best thing to do is add rod to ceiling if possible, if not, Add larger strut but leave an over hang on opposite side of beam so it keeps it from bending or bowing idiots never think for future installations always do have some consideration plan for the future.

These guys didn't plan for the present... as it appears to the OP.

Agreed, at a very minimum they should install two more allthreads if possible. However, I cannot understand why they did not use back-to-back or double strut (3 1/4"), and think that should probably be added now. Also, why not use 1/2" allthread? And what about those beam clamps? I'd think about 1/2" malleable iron or possibly another method of fastening to the ceiling.

 

[BJ Conner]

BLine catalog.

BLine catalog.

The Bline catalog has a good section on application. Starts at page 224.
I went through it quick and got a load of 750 lbs, The max load for 2 3/8" all thread rods is 850 lbs. To close for numbers from a cookbook.
The general rule for deflection is 1/360 of the span. 108/360= 0.3"
There might be a code violation but I have haven't had time to look it up. Out here we have inspectors who want to see seismic hangers done by a structural engineer or installations done with standarized (cook book) hangers.

http://www.cooperindustries.com/con...atalogs/bolted_framing/strut_systems/SS10.pdf