Lateral load on a bridge crane.

[ntattose]

I am looking at a single girder bridge crane. The hoist runs along the bottom flange of a W section. When considering lateral load I have always assumed that the load is resisted by the bottom flange only. So I use Iy/2 for deflection and Sy/2 for stress. Is this too conservative? Does anyone have a better approach?

 

[canwesteng]

you can also resolve the lateral load into a weak axis moment and torsion on the girder. with the bi moment method this is essentially equivalent to what you are doing though.

 

[ntattose]

Thanks for the response CANWEST

 

[NS4U]

I agree with your approach.

I think canwest assumption is only valid if your web so stiff enough so that you engage the whole cross section by dragging the load from the bot flange to the top. I don't think the web is in most cases and I just rely on the bottom flange to do the work like you noted.