All trussed up and nowhere to go!

[Robert]

Some company hired to build truss spans to cover a road race. Did they get it right? Heavy duty box truss with double truss legs for ground support on each side. See the mistakes?

 

[DuckJordan]

Who manufactures the truss? It could ever well be exactly right

Sent from my XT1060 using Tapatalk

 

[ScottT]

It's blocking the road!

*ducks*

 

[Robert]

Who manufactures the truss? It could ever well be exactly right



Sure Heavy Duty box truss probably fine for the span. Didn't see the manufacturer. Look closer.

 

[Scarrgo]

If you are talking about the way the truss laying across the street, than its needs to be turned so the correct side is facing the ground...once it is standing up...

Sean...

 

[Robert]

Yep, they mounted the top truss sideways. It was already bolted up and that's how they ran with it.
I would like to see some guy wires and some ballast. While no equipment was hung on the truss, it did have two large banners on the span and two more on the vertical legs. I'm thinking wind load and rain as forces not considered.

 

[DuckJordan]

Actually with tower truss orientation doesn't matter

Sent from my XT1060 using Tapatalk

 

[Robert]

Actually with tower truss orientation doesn't matter

Sent from my XT1060 using Tapatalk

Wow, even for the horizontal?

 

[DuckJordan]

Even for horizontal, The way that there are cross braces in the center of the truss The (diagonal webbing) makes orientation for anything other than ease of use irrelevant. I'm talking about the interior cross pieces. the ones if you had the truss on end such as
The orange and red cross braces

 

[Robert]

I would love to read up on this. I can't find any sources except one that identifies the top. bottom and sides of a truss for proper orientation.

http://www.tomcatglobal.com/Training/Instructional-Videos/

 

[DuckJordan]

Its not something you will learn online, Tomcat says it in their one on one training when getting a new roof

 

[Robert]

Okay, thanks I'll email them next week.

 

[porkchop]

Actually with tower truss orientation doesn't matter

Sent from my XT1060 using Tapatalk

If you're talking about the truss sections that are running vertically I'll agree with you that some manufacturers design truss towers that orientation doesn't matter on, but for any sections running horizontally orientation matters.

 

[DuckJordan]

If you're talking about the truss sections that are running vertically I'll agree with you that some manufacturers design truss towers that orientation doesn't matter on, but for any sections running horizontally orientation matters.

Not with tower truss as pictured here. Its the same vertically as horizontally

Sent from my XT1060 using Tapatalk

 

[robartsd]

For the loads these saw (minimal equipment attached), I highly doubt the orientation is important in this case. Normally truss would be used to support quite a bit of weight betweens supports and correctly orienting the truss provides the best strength for this use.

 

[Robert]

So I'm coming back to this after talking to two different truss manufacturers. Consensus being:

You are right, just judging on how the truss is oriented in the photo, it would be on its side when stood up. This would be incorrect, as we want the diagonals to be in the load path.

When questioned further about any truss they manufacture that does not have a top or side he responds:

Well, 12” truss does not have a specific top or bottom. Some companies may flip the truss depending on how loads are being applied to the span, but the diagonals should always be in the load path and the diagonal pattern should be consistent throughout the span.

Point being diagonals should always be in the load path. While this does not exclude a situation where a truss could be mounted sideways, I would consider that very rare.

 

[What Rigger?]

Oh Lorde, please don't let this be the Long Beach GP...I think I get to go this year.

 

[Robert]

No, smaller event and small company. 26,000 people went under it though.

 

[egilson1]

Point being diagonals should always be in the load path. While this does not exclude a situation where a truss could be mounted sideways, I would consider that very rare.

Good opportunity for some more education here.

What are possible rare situations when you would want to have a horizontal truss with the diagonals on the top and bottom?

 

[Robert]

My rigging is based on lifting lighting, audio, and set pieces in theatrical and corporate/concert type events. My guess would be that there are some instances where a side load is applied to a structure and you would want to rotate the truss to support that. My feeling is this would be more likely to happen where wind loads could react to static loads attached to a structure.