Suspension bridge for piping? 3

[Thoughtclaw]

Hey folks, I've been asked to design a bridge structure that will carry some piping across a parking lot, a span of 70 feet. The client was thinking a suspension bridge might make the most sense, given the long span, but we're only talking about a load of 2.9 pounds per lineal foot, and the pipe is only 2" in diameter. Obviously the concern with just using a channel or I-beam or what have you is that it would have to be far heavier, but a suspension bridge would require an awful lot of labor. Does anyone have some advice for me?

 

[human909]

Suspension bridge!? Do you realise how complicated that would get. This is only 70 feet!

A lightweight truss is the obvious answer. I've even done this before with aluminium:

https://www.itsctruss.com/500mm-entertainment-black-lighting-truss-beam-alu_p347.html

(Though depending on your deflection requirements you might need something deeper than 500mm)

 

[LittleInch]

Why is my first thought.

You're going to spend a fortune to carry one 2 inch diameter pipe at ? high 20 odd m across a parking lot. Difficult to believe there isn't an alternative.

What's at the edge of the parking lot? Anything to hang anything off. A sketch or picture would help a lot.

Suspension of something like this can be done but need a lot of lateral support to stop it turning into a modern day tacoma narrows...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[phamENG]

Yeah, but a suspension bridge sure would look cool.

This does seem odd. Just get a direction driller to run it under without trenching. As long as you don't have a bunch of other utilities running under there, it's not that hard. If it absolutely must go over, then a truss would be a good option. A pair of 36" LH series open web joists with a bunch of x-bracing might get you there.

 

[JStephen]

https://panethos.wordpress.com/2021/04/02/the-nutty-squirrel-bridges-of-longview-washington/

 

[LittleInch]

A hybrid suspension and structure. Never seen that before but could work.

I'll have to remember that.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Tomfh]

Box truss

 

[Thoughtclaw]

Thanks so much, guys. I'm going to explore the truss idea. I feel silly for not thinking of it myself.

 

[dvd]

Alyeska pipeline

also

Images of Pipeline and Industrial Suspension Bridges

 

[CrabbyT]

A suspension bridge seems like the wrong answer, or maybe it's possible that they're just using the wrong terminology.

What you want is a box truss. Aside from dead and wind/seismic loads, make sure it's designed for ice loads in accordance with your latest adopted building code. Ice is heavy.

You should assume they'll want to install more pipes/conduits in the future. Maybe make a judgement call based on your experience with the client. For instance, maybe assume that they'll want to run (20) 3" pipes across this thing, ask the client if that's a reasonable assumption, and then design it accordingly. Make sure you list how many pipes it was designed for on your drawing.

 

[jhnblgr]

Why not just attach the water line to a cable and run it across? Maple syrup industry has been doing this for decades for sap collection.

 

[1503-44]

Make one of those squiril bridges.
They will come and take selfies.

Jhnblgr. "Sling it from a cable."

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."