Sprinkler Dead Load

[Lutfi]

I have been using, for office type buildings, a uniform dead load of 4.0 PSF for sprinklers.

Lately, I think this is a conservative load. Does anyone agree of has more definite dead load value.

I contacted a fire protection engineer that my firm works with and he did not have an answer. He and I are working on a real project to compute actual pipe and water weights for a recent project. I will share what we come up with all.




Regards,
Lutfi

 

[miecz]

Search for previous discussions on this topic. Four psf may not always be conservative. I use 6 psf.

 

[Lutfi]

jmiec,

I agree with you and I used 7 psf before. However, it does not make it right!

To complicate things, structural engineers evaluate these loads way in advance of the sprinklers being designed and laid out. May be this is the driving force to be conservative.

On the first calculation with the fire protection engineer, we came with 0.288 PSF!!!!!

Judgment should be used on project-by-project basis. However, we need to utilize valid loads while maintain safe conditions.


Regards,
Lutfi

 

[UcfSE]

That 0.288 psf gets spread across the entire floor area, correct? That distributes loads and dilutes the local effects of the true loads. That seems good enough reason to overestimate the sprinkler load, and any other for that matter. Using 6 or 7 psf does seem a bit too high IMO unless you have very large pipes.

 

[whyun]

When estimating a seismic contribution from a sprinkler system, I've used 2 psf in the past.

Gravity design is different. Depending on the size of the feed and cross mains, actual calculated point load from hanger reaction may control the member design, especially if the member is a wood joist.

 

[JAE]

I'm with whyun - I've used 2.5 psf. Basically I assumed a wet-pipe system - usually they are 2" lines or so - and with the spacing and pipe weight you get a pretty low number.

The trunk lines do tend to be heavier so sometimes I treate them separate from the uniform psf.

 

[miecz]

I once had a building where the overall load was well under 2 psf, but some areas were over 5 psf. Of course, I found this out after the design was finished.

 

[Lutfi]

Whyun and JAE have good points. I also require joists to be capable of supporting point loads from hanger when the feeder pips sizes get large.

UcfSE, It does sound small. However, this is real number and the result of doing actual take off on a completed project. I plan on calculating more.

It sounds like the load that I have been using is not all that far.


Regards,
Lutfi

 

[dik]

Unless you have some really big local conditions, you'll be hard pressed to exceed 3 psf...

Dik