uniform load 1

[5747hazel]

how much dead load in psf do you guys consider for mechanical duct allowance and sprinklers in an apartment building? also out of the 40psf floor live load in residential how much do you consider as sustained. I read somewhere online saying 40 psf is way conservative recently but couldn't find it anymore.

 

[dik]

Depending on the type of building, I often use 15 psf for MECS... (my term for Mechanical, Electrical, Ceiling, and Sprinklers)


Dik

 

[JAE]

Mechanical piping, ductwork, lighting - 5 psf
Sprinklers - depends on whether it is a wet or dry system.
Usually between 1.5 to 3 psf
Special allowance for larger trunk lines - such as 8" diameter type filled piping or standpipes.

 

[JoshPlumSE]

JAE -

Is that locally where you know the piping corridor is? Or, is that uniform over the whole floor?

 

[JAE]

For the overall sprinkler weight (usually around 2.5 psf) that is over the whole area where sprinkler piping coverage occurs.
For special piping - we would use a line load or a series of designated point loads for the hangers.
The problem usually is that you don't always know exactly where the trunk lines will be located and also don't always know the spacing of hangers.

 

[5747hazel]

thanks everybody. it is an apartment building and I basically want to get an overall psf but not local load to size my foundation. 15psf sounds like too high. it is a three storied apartment building.

 

[dik]

15 psf is too high for apartment bldg... maybe 5 psf...


Dik

 

[msquared48]

For an apartment, I have used 2 psf for Mech/Elect, and 2 psf for Sprinklers.

None have fallen down yet!

Mike McCann, PE, SE (WA, HI)

 

[r13]

Whether it is 5 psf, or 15 psf, is it included in the 40 psf design load, or to be allotted for? All of above mentioned is considered sustained load, how about furniture, ceiling and partitions?

 

[dik]

Usually on top of... and treated as DL so no live load reduction.


Dik

 

[JAE]

Whether it is 5 psf, or 15 psf, is it included in the 40 psf design load, or to be allotted for?

All this discussion is about supplemental (or collateral) DEAD LOAD.
It has nothing to do with the live load (40 psf or otherwise).

 

[5747hazel]

Mechanical/sprinkler should be part of the dead load. I think partitions, kitchen and bathroom stuff should be considered as sustained part of live load. But how much are they? 10psf?

 

[JAE]

I think any determination of how much live load is "sustained" is at best a guess.
Depends on the type of live load and probably has more variability than the live load itself as percentages that are sustained probably are of all sorts of values depending on the actual building.

Perhaps guess at 15% of live load? 25%?

 

[r13]

JAE,

I want to give you a star, but I didn't. Because you haven't answered the full question set, which somehow relate to the 40 psf live load. Let me ask simply - is the 40 psf consisted of human weight/activity only? If so, what is sustained, and what is not? THis is part of the OP's question too.

 

[JAE]

Just read my post directly above yours.

 

[r13]

JAE,

Still considered incomplete I know the line is very difficult to drawn, always depends some factors, and how conservative/liberal one wants to be...

 

[JAE]

I'm not sure why my statement saying there isn't any direct guidance on the percent of LL that is sustained can be any more complete.

And after all these years designing buildings, the percent of LL sustained doesn't matter all that much.

 

[5747hazel]

I read a similar post done many years ago here regarding this issue. the soil report gave us two allowables. one is net which should be used to check against dead plus sustained live. and the other one should be used to check the total load. we can do a live load reduction for multiple stories. after that even the total load only has say 50% of the total live load. but the sustained part of the live load should be the "dead" part of the live load which should remain constant within that 50% left. if you consider 25% live to be sustained now it becomes 50% which would make checking the net allowable critical. now we need to have a better guesimate of the sustain part.