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Re: Commercial Sign structure

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All the replies to the query about designing and analysing a tower space
have talked about computer solutions. Is the current crop of engineers
really that dependent on computer analysis programs?

Why not just design a regular statically determinate frame - it doesn't have
to be two dimensional -  and use statics and a calculator? Start with the
loads at the source and follow them through to the foundation, resolving the
components at each joint and making sure the sum of all forces and moments
anywhere is zero.

Or don't they teach that anymore?

Jim Warne
Vancouver, BC

> I am designing a  commercial sign where  a steel open frame tower
> 10'x10' with four legs and 90' tall supports a 30' high x 50'wide
> billboard  like a cantilever beam.  The billboard  is framed with
> several horizontal trusses connected to the four legs
> of the tower. The wind load on the  billboard  produces  a large
> torsional force on the tower.
> I am using RISA 2D only.  How do you create a 2D model for the open
> frame tower taking into account the torsional forces from the billboard?
> Is it possible to do this or do you need 3D analysis?