braced frame

[nitnelion]

Hi. I am designing a fairly large elevated platform to support heavy mechanical equipment. The platform falls into design category D. Because the platform is less than 35' tall, I am using ordinary concentrically braced frames for vertical bracing. However, the platform does not really have a diaphragm - just open bar grating. So I need to provide some horizontal bracing to get the forces from the units to the vertical bracing frames. Does this horizontal bracing also need to meet OCBF requirements.... seismically compact, connections designed for RyFyAg, etc... Normally, I've seen angles welded to the beams under the grating. Thanks.

 

[haynewp]

I would not think it would have to meet the requirements for vertical braced frames. The seismic provisions are developed based on vertical ordinary braced frames, not horizontal ones. I think of what you have as a horizontal truss resisting seismic, but I do not think the whole thing needs to be detailed like a vertical OCBF.