Cantilevered Truss Design

[tristan861]

Hi all,
I'm about to design a cantilevered truss ( for the first time) as an openable curved roof with around 30m span, My question is:

- How could this act like a truss since its only one supported; there will be bending moments near the support. Am I right?
- What is the best idea for such a truss?. To be done as a space truss or regular Pratt truss?
- What is the Max allowable Deflection would be like for such a structure?

Guys your Help Would be much much appreciated )))

 

[dik]

Can you attach a drawing or sketch? Openable roofs often have a fixed portion and the part that opens is on a track that 'rolls' underneath the fixed part. No cantilever.

Dik

 

[BAretired]

With only one support, the top chord would have to be in tension and the bottom chord in compression under gravity loads. The single support would need to be capable of resisting the resulting bending moment. It could be Pratt, Warren or Space truss but it may be preferable to remove the cantilever feature by providing suitable framing to accommodate the openable roof as suggested by Dik.

BA

 

[dik]

I checked the wierd and wonderful connections for the Toronto Sky Dome... and have a bit of an idea for moveable roofs.

Dik

 

[tristan861]

This is a sketch for the cantilevered truss per Dik request.

this span is around 85 ft. the bottom chord is failing under bending near the support and huge deflection is occurring to the chords.

 

[dik]

I cannot tell from the sketch what is cantilevered. Is the truss supported at each end? If supported and fixed only on the left side and the whole thing is likely too large to cantilever.

Dik

 

[BAretired]

It cannot work as shown. A single column cannot support an 85 ft. cantilever.

BA

 

[kipfoot]

I've marked up your sketch to show my opinion of what might work as a starting point.

 

[rb1957]

possibly it's too complicated, but why not retract the arm with the panel? ... I see the arm segments stacking vertically in the retracted position, with tracks to guide them to horizontal. arm segments would be telescoping. Cover would have it own retracted problems to solve.

another day in paradise, or is paradise one day closer ?

 

[dik]

With the weight going to the free end of the cantilever, increasing the deflection...

Dik

 

[tristan861]

Hey Guys..
Its not going to be cantilevered anymore, I attached trusses in the transverse direction as main trusses.
Here is a sketch of what I did.
Please advice for any notes
Thank you