Prolyte Campus blog: Just one single round tube

 “What is the capacity of just a single round tube?” This question is generally ignored by truss manufacturers, as it has little to do with their business. And it’s too vague for a structural engineer to answer just like that. If he answers the question as it is asked, the invoice could become quite high when all the possibilities are tackled…

The issue: Many rental companies have a range of additional single round tubes that are used in an endless amount of variations. Crossing between two trusses, short outriggers, boom arms, vertical extenders up or down etc etc. So any of these particular situations can only be answered after some counter-questioning.

1) What type of metal? Both steel and aluminium can have tensile strength qualities that range from “toilet-to-top”. [Or “sh@t-to-summit” as others might say].  
2) What is the alloy, the tensile and/or yield strength or that round tube material?
3) Is they’re welding done to that tube? A lug or an eye-plate perhaps, or a ‘splice butt-weld’?
4) What outer diameter (OD)? Trusses and truss clamps range in OD of 48 to 51mm, and that can already mean some difference.
5) And what wall thickness (t). This ranges from only 1,6mm up to 10mm.
6) What is the round tube orientation?
6a) Is it used horizontal in a simply supported span, or as an outrigger?
     6b) Can the support point rotate, or is it fully restrained?
     6c) Or is the tube orientation perhaps vertical?
     6d) Is the tube used upright on a single small base plate, or on a heavy big one?
     6e) Or is it fully restrained + clamped to a truss perhaps?
     6f) Or is the round tube used ‘hanging’ down vertically, like an ‘extender’?
7) What kind of loading is to be applied? UDL? CPL?  
8) Is the applied load static or dynamic?

And whatever more variations one could think of for one single tube only. A lot of questions…

The answer: Let’s at least pick out one of all those questions to be answered.   

CPL in static loading on a simply supported single round tube 48x3mm without any welding area (alloy EN AW 6082T6).

   Blog Single tube loading.png

Span â–²---â–²  (m)

CPL â–¼  (kg) 

0,5

300

1

150

1,5

95

2

75

2,5

60

3

50

The verdict:  Everything in rigging and staging structures shall be adequately safe. Make sure you know that all components and details are safe as well. Consult the manufacturer, a qualified engineer or otherwise competent person to remove any uncertainty. Maybe this also explains that no truss table in the world can ever be covering all types and variations of the structures that users of the truss might think of assembling and loading. 

 

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