Angle braces or rods for industrial roof bracing? 3

[IJR]

Have a fresh week full of enthusiasm

When we design small span (say 60ft) industrial buildings we prefer to brace roofs with rods forming X braces.

Whenever we deal with a giant like say 150ft we have a habit of using single angle X braces

Single angles tend to sag.

Can I go back to my X-rods, choose heavier angles(A WASTE) or detail so that angles dont sag(EXPENSIVE)

Any comment from the experienced ones is most welcome

Regards

IJR

 

[dik]

Not quite sure I understand the structure...

150' span for the primary structure? are you using a rigid frame, or fabricated truss, or something of that ilk?

Are secondary members, joists, beams, etc? spanning 20-30' between the primary structure?

Not often that I've used bracing in the plane of the roof, but any projects I've done this for have had the angles supported by the secondary structure so sag doesn't become an issue. When bracing member hits a truss or frame member, a tab welded to each side of the member is used to transfer the cross-bracing force through it. I've not used rod (bar) for roof, although I often use it for walls but there's no reason not to use it in the roof plane (any pre-eng bldgs I've encountered use it all the time).

 

[Ron]

IJR...I agree with dik...also not sure why the need for X-bracing in the roof plane. Are you in an area with inordinate wind loads that might produce wracking of the entire structure?

Congrats on the Tipmaster of the Week last week. Your Monday morning enthusiasm is contagious! Thanks.

Ron

 

[IJR]

Thanks Dik, Thanks Ron

Dik, thanks for visiting this forum. Ron is always here providing the best I have ever had from steel designers.

Dik: They are the usual long span rigid frames spaced 18ft apart and connected to each other by wall braces. Being too long and in windy area there is a need to connect at least a few rafters in the plane of the roof by some X braces. It is the usual configuration you are quite familiar.

Ron: Yes the area exposed to wind is large enough.

Ron: The Tipmaster stuff came as a surprise-I still assume there was some error in some voting software they use at eng-tips. But the forum has been great with good friends like you.

THX
IJR

 

[breaks]

IJR -

I've had dealings with a couple of large warehouse-type structures on the east coast (hurricane coastline). In one project, I was working on incorporating a new cruise terminal into an existing warehouse.

The existing warehouse was at least 200' x 1000' and incorporated various rows of columns and moment frames. The roof utilized tensions rods, not angles, for cross-bracing.

Not sure if that helped, but I thought I'd include it anyway.

Matt

 

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