HI everyone. I'm a grip in the film industry in NY. My Union exam only comes up once every three years and it's at the end of the month now. I have been studying for years and done a ton of research and but I can't find the answers to these two questions... Maybe someone can help?

1. If a truss has a UDL of 2000 lbs, and there is a 1000 lb load on it, how much weight can be added before it makes out the CPL?

(It's my understanding that the CPL is just under the UDL, but that they are roughly the same. So <1000 lbs. Pass or fail?)

This one is really difficult...

2. How much weight can be cantilevered 8' on a 10' truss?

(I looked everywhere for the answer to this and found something in the Arena Riggers Handbook which said this: . But that makes little sense. A span 4x greater than 8' would be the CPL of a truss that is 32'. Does that make sense? I will probably take a class in this eventually but for now I could just use the answer.)

A truss or any beam has a maximum allowable stress. The stress = bending moment / section modulus of the beam or truss.

The section modulus is a fix value for a particular truss section being bent around a particular axis.

So in all of these cases you can just look at the bending moment equations to see how they are related.

UDL Moment = (Length of truss x the total distributed load)/8

CPL Moment = (Length of truss x centre load)/4

Counter Leaver moment = Length of truss x load

There is also a maximum load the truss can take no matter show short it is - the max load will be the same for all of these if its a

**very short** truss. (think 5 feet or less)

If the truss is long

*"the rule is that you use the CPL of a span that is 4x the span of the cantilever"* is correct.

... and the CPL is half the UDL - so the answer is 500lbs in your case.

* (technically its the sum of the moments i.e. 2000 lb UDL moment = 1000 lb UDL Moment + 500 lb CLP moment)*you can see how some of this works in these tables

https://www.xsftruss.com/load-table-and-ratings-guide/#center-point-load