engineering/physics teaser..

[artyb]

anyone have any experience with steel beams/basic physics.....

i would like to use a 4x4 steel box section to support a plastic roof over a workshop im building,

the box section is 6m long and has around 1.5mm thick steel walls,

im assuming it will sag slightly under its own weight,...although it barely moved when we put my chunky 16 stone mate on it.. :party:

if i was to set the box section diagonally [looking at a section view..] rather than flat, would it be more ridged.....im assuming it would... :wha:

im not sure ive made this crystal clear ... :?

 

[Runwell-Steve]

It will be stronger square, rather than at an angle.

The strength to stop it bending is in the vertical sides of the box.

Make yourself a small piece of box tubing out of paper, try bending it when you have it flat, it's doesn't want to bend, however when you twist it by 45 degrees and then bend it its easy as it flattens at the point where it bends.

 

[Dog Breath]

A box beam on the diagonal will definately be weaker than if you had it square as your support will only be as strong as the joints where it is welded because it won't offer any real support compared to fitting it square. The force of the load pushing down on it will cause it to buckle sooner. I'd have said something like an "I" beam would be the best option. How much weight overall are you looking to support?

Edit: What Steve said :thumb:

 

[artyb]

cheers guys that all makes sense... :clap:

i only have corugated polycarb sheets [which weigh nowt] on it, with some 2x2 supports, but it will have to cope with the snow when we have some... :?

 

[artyb]

im also making some I beams, from osb and 2x1 glued together.... :party: