Roof Cross Bracing

[pureyber]

Hi fellows.

What are your parameters in considering the roof cross bracing? My roof support is a rafter type with one slope only and a 12 storey building.
Anyone have a reference book for it?

 

[hokie66]

Diagonal bracing in the plane of a roof is designed like any other truss. The only difference is you generally need to support the braces to prevent excessive sagging.

 

[KootK]

Is this corrugated metal deck over steel beam? What part of the world are you in? The photo below is an example that I encountered over the weekend.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jike]

Bracing is normally provided by the deck if it can act as a diaphragm. I only consider the use of roof bracing if the deck cannot function as an adequate diaphragm to carry loads over to vertical bracing or shear walls.

 

[pureyber]

Did you not consider Cross Bracing as a lateral support of your roof truss or rafter? I have a wind velocity of 200Kph, I am confused if I consider cross bracing or not, hence I only consider one span in my analysis.

 

[hokie66]

The cross bracing may or may not occur where you want to brace the rafters. Rafters are braced at the top flange by the purlin connections, and the normal way of bracing the bottom flange is with fly bracing (diagonal braces to the purlins).