Metal Building Frame Spacing

[abusementpark]

Does anyone have a good rule of thumb for a practical maximum spacing of metal building frames?

We usually have to set the spacing prior to a metal building supplier's involvement in the project. Ideally, we like to maximize the spacing within practical limitations.

 

[msquared48]

Larger buildings - 20 to 25 feet

Smaller ones - 8 to 12 feet



Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[jimstructures]

If you will have continuous purlins and to a lesser degree continuous girts make your first and last bays shorter than average and your second and next to last longer than average and then make all the other bays approximately equal.

Make your bays about 25' long or say 23' to 28' long. If you are paying for erection by the piece make them longer, say 30', or if you are paying for erection by the square foot make them all close to the average, say 25'.

This all refers to primary and secondary framing. Paneling is all by sq ft any way so it does not make a lot of difference about bay length.

Jim,

10 years with a major mfg and 7 years with a builder.

 

[ajh1]

Depends a lot on what the gravity load requirements are. Most manufacturers' purlins will span 30' under reasonable loads. For loads in excess of 30 psf snow, shorten the bays down. With most layouts, the most cost effective tends to be something that will equally divide the overall length, .i.e., 30' bays don't make sense on a 100' long building, but would be logical on a 120' building with appropriate loadings. For buildings with top-running cranes, 25' bays is a logical maximum. For buildings other than clearspans, layout is driven heavily by what is going on inside the building, equipment layout, etc.

 

[JAE]

Some building manufacturers will go to 30 feet between main bents but 20 and 25 feet is more typical.

 

[Ron]

I'm with the others here who note common spacings. I would not try to match spacings with some design expectation of a particular manufacturer, since that won't be known at the design stage. Besides, this is a delegated engineering function for which you, as the EOR, do not want to do their engineering for them and absorb their liability as well as your own.

Give them guidelines (20,25,30 feet)and let them return with sufficient engineering, upon which you should be able to reasonably rely.

 

[abusementpark]

So it sounds like 30 feet spacing is a good practical limit? I'd like to have a good answer for when the time comes when an architect wants to push metal building spacing to the limit.

I'm assuming that it is the girts or purlins that become uneconomical or not viable when you get into frame spacings that are much greater than 30 feet?

 

[civeng80]

abusementpark!

That would be a fair statement !

A portal I designed about 3 years ago was 100 ft span with a bay spacing of 30 ft and this had 8 inch purlins.
The purlins were just on the point of working for the wind conditions. I think I took the bay spacings to the maximum.