horizontal diaphragm 1

[struengineer]

I am designing a 2-story building (30’x60’x16’(h)) with big windows at all sides. Building has to stand for a heavy wind load and there is no any shear wall can be constructed for the layout. I therefore chose the following system:

Framing: made of steel beam and post
Roof and floor: made of timber joists and plywood panel

My questions are:

If I consider roof and floor as a horizontal diaphragm to minimized steel member sizes, what should I do at the connection between steel beam and timber joist to ensure timber and steel work together? Can I find this kind of detail on any web site?

Please help!

( Thanks for MeggieM DaveAtkins UcfSE and MeggieM’s advice for my previous question. I talked Simpson’s engineer, they don’t recommend that using timber joist with Simpson connection as lateral supports.)

 

[Taro]

You could add a wood nailer plate to the top of the steel beams. Weld threaded studs can be used to bolt the nailer to the steel beam. Then nail your plywood diaphragms to the nailer plate.

 

[DaveAtkins]

If you have no shear walls, the beams and posts will need to be rigidly connected to become moment frames. This will not minimize the steel sizes; it will make them heavier.

DaveAtkins

 

[struengineer]

Thanks for response. guys.

To Taro,

In order to make the horizontal diaphragms and steel beams work together, Do timber joists also need to be somehow attached to steel beams? only nailing plywood panel to nailer is good enough?

To DaveAtkins
Yes, I use all moment connection for all beams and columns. However, if the beams can be horizontally supported by the diaphragms, they will be smaller because the horizontal moment and deflection will be partially handled by the diaphragms. Am I right?

 

[DaveAtkins]

You are not correct. The moment frames support the diaphragms; the diaphragms do not support the moment frames. The load path is as follows: Walls carry lateral loads to diaphragm, which carries lateral load to moment frames, which carry lateral load to foundations.

DaveAtkins

 

[jen4950]

NOO!! Load paths as Dave said-

What columns did you have in mind? A quick and dirty hand calc on a napkin without my steel manual or software came up with a W12x58 minimum. I'd recommend consulting a registered P.E.