Dimensioning of hollow square and circular rod

[JohnnyR]

Hi

Can someone tell me how to determine dimensions for a square hollow rod and circular hollow rod when the material and maximum load is known?

 

[Baluncore]

This will depend on the way the load is applied to the hollow member.
Is it axial compression or tension, torque or a sideways deflection ?
There is also a trade-off between outer dimension and wall thickness.

 

[JohnnyR]

The applied load is compression and there is also bending.
It´s a telescopic rod with the circular rod inside the square rod and it´s standing vertically with an angle. The rod has to support a boat standing in a boat rack so it has to support the weight of the boat and the force from wind gust. The material is set to be S235JR Low Carbon Steel.
I hope you can help. Thanks.

http://imagizer.imageshack.us/v2/1024x768q90/833/drpm.jpg

 

[nvn]

JohnnyR: If the length of your telescopic rod assembly is 2,26 m, and if your member forces in post 3 are correct, then it currently appears the round tube would need to have cross-sectional dimensions (outside diameter by wall thickness) as listed in any of the following options.

(1) 216 x 5 mm
(2) 197 x 6
(3) 182 x 7
(4) 171 x 8
(5) 155 x 10​