15 PSF Partition Load - Part of Lo In Live Load Reduction...?

[walterbrennan]

It seems clear that the 15 psf partition load, as required in IBC 2015 section 1607.5 is considered a live load... at least, the commentary appears to present it that way, when it states, "This partition allowance is included under live loads..."

--- What's less clear is whether or not this live load should be lumped together with the ordinary occupancy live load (e.g. office) BEFORE the live load reduction factor is applied, or AFTERWARD.

A quick look at the live load reduction provisions in section 1607.10 yields the following: "Except for uniform live loads at roofs, all other minimum uniformly distributed live loads, Lo, in Table 1607.1 are permitted to be reduced..."

--- Without seeking to be legalistic, it is probably worth noting that the partition load is not, in fact listed "in Table 1607.1"

I'm not seeking to instigate an argument, based strictly on logic, opinion, dogmatic past experience, etc. Rather, what I'm seeking is an actual published opinion, from a trustworthy source (e.g. ICC, ASCE, etc.) which might provide clear direction on whether or not the 15 psf partition load was ever intended to be included in Lo.

Can anyone offer any such reference...?

 

[JAE]

We don't reduce that live load typically.

The original "partition" load from years past (20 psf) was originally devised as a way to account for the fact that in an office environment, with walls that could be relocated in the future, there was the problem of dealing with the fact that some of the floor would be office (50 psf) with some added weight for partitions; and some of the floor would be egress hallways between strictly office areas with the code mandated 100 psf live load. The use of the 20 psf in addition to the 50 psf was an attempt to bridge that situation.

In recent years, the partition allowance was reduced to 15 psf but I view the concept as the same, just a little less conservative.

With that in mind, the idea of reducing dead weight of partitions and/or 100 psf egress load doesn't seem to fall into the concept of a statistical reduction of a variable floor loading - so we don't reduce that part of the loading.



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[rapt]

Partition load has a variable load factor, the same as a Live Load. That is because its value and positioning is variable so needs a higher factor to account for this. But it is not a live load.

 

[JAE]

In ASCE 7-10, Section 4.3.2 (the live load chapter) requires "Partition Loads" of 15 psf. So obviously considered a Live Load per ASCE 7.
Similar in the IBC Section 1607.5.

rapt, can you explain a bit more about a "variable load factor" for partition loads? I've not seen that in the ASCE 7 or IBC.

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[walterbrennan]

rapt:

If it is not a live load, how come IBC 2015 clearly states,"This partition allowance is included under live loads..." in the commentary of 1607.5...?

 

[walterbrennan]

JAE,

Everything you've stated can be found in the commentaries of both IBC and ASCE 7; but neither of them explicitly addresses the question of inclusion in, or exclusion from the live load reduction calculation...

So that's a "no" on having access to any sort of published opinion, article, continuing education excerpt or the like, from ICC (or, even the old ICBO), ASCE, or anyone like that...?

 

[JoshPlumSE]

Walter -

Thanks for the great question / post. This is one of the reasons why I really love Eng-Tips. To answer your question, I don't know of any published article on the subject. I did find some published commentary on the subject from the EuroCode guys. Not sure that helps you much.

The key to me is that it's not in Table 4.3-1. And, only LL from table 4.3.1 may be reduced (except for roof live load where partitions don't apply). Therefore, per a strict interpretation of code, it should NOT be reduced. At least not how I read ASCE-7.

One can certainly make an argument that it is variable in area and members supporting large areas are unlikely to have 15psf of partitions (because that's pretty densely spaced) over large areas of the building. Therefore, I'm not going to rake anyone over the coals who thinks it should be reduced. In fact, on a conceptual basis, I would agree with their argument. However, if a plan checker tells you to justify it legally per the language of the code, I don't think you can.

 

[JoshPlumSE]

I should point out that the EuroCode article seems to be saying that if the partition load is generous (which 15psf does seem pretty generous per the ASCE commentary on the subject) that LL Reduction is justified, especially considering the higher load factor it has already been subject to.

Again, that's an argument on conceptually what should be done. Unfortunately, I don't believe you can interpret the current US codes that way if you strictly follow the code as written.

 

[JAE]

WalterBrennan

I’m fairly certain there’s an article “out there somewhere” that talks about what I wrote above on the origination of this partition load. Whether it is accessible online I’m not sure.

By plain code language:
1. It is a live load
2. It can’t be reduced as the reduction language only refers to the tabulated live loads and not the special partition load




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[slickdeals]

I don't find a reference but I recall from an AISC seminar where the presenter had recommended to use 80 psf LL and reduce it instead of using 50 psf reducible in combination with 15 psf unreducible.

 

[dik]

It seems clear that the 15 psf partition load, as required in IBC 2015 section 1607.5 is considered a live load... at least, the commentary appears to present it that way, when it states, "This partition allowance is included under live loads..."

How are partitions stipulated in the IBC. The national building code of Canada stipulates for partitions OTHER than permanent partitions to require the partition dead load to be included... My drawing notes stipulate that the partitions shown are permanent and that they can only be revised by an engineer. I typically calculate a partition load based on the height of the partiton less the liveload taken up by the footprint to give me the partition load.

Partitions are treated as dead load, and is only a fraction of the stipulated partition loading.

The above approach has not been challenged, yet...

Dik

 

[rapt]

JAE,

Variable loads (loads that change in value and position over time)have a higher multiplying factor in ultimate strength calculations than permanent loads( loads that are essentially fixed in location and value over time). IN ACI terms, variable loads have a factor of 1.5 and permanent loads have an ultimate factor of 1.2. Fixed partitions are normally consisdered to be permanent as are tiles etc. Moveable partitions are considered to be variable for ultimate load factors.

But LL reductions normally only apply to Live Loads, not all variable loads.

A similar problem comes up with codes like BS8110, AS3600 and Eurocode in serviceability calculations and where the LL factor for serviceability is < 1.0 depending on the building type. But Moveable Partitions have a factor of 1.0.

RE LL reduction, I have commented before that I doubt its financial benefit for floor system design (not columns and walls) especially in multi-storey construction when construction costs are included. If you have a 10" slab which I think in US units works out to about 200psf with a LL of 60psf, then back-propping would have to be at least 3 floors and probably more. If you can reduce that LL with LL reduction to 30psf, then you have to back-prop twice as many floors.

 

[walterbrennan]

JAE:

Was there a particular policy you had in mind that I needed to check out... or was that just an automatic pop-up...?

 

[walterbrennan]

All:

After a little (well, a lot of) digging, I found a thread that does seem to address this, directly.

https://www.eng-tips.com/viewthread.cfm?qid=161349

I note WillisV's response, about a dozen down in that thread, where he quotes an ICC opinion that he solicited; which seems to imply that inclusion of the 15 psf in Lo is acceptable... or at least, not flatly rejected by IBC in any overt way.

If, in the way of partitions, we're talking about stud and gypsum board wall construction, I think I have to agree with WillisV's findings; and ICC's opinion...

Although, after so many years, it would be good if they would simply eliminate the mystery and state it explicitly; one way or the other.

 

[WillisV]

You’re welcome.

 

[JAE]

walterbrennan
Not sure what you mean by “pop up”?

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[JAE]

rapt
Thank you

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[walterbrennan]

That's what Willis was talkin' 'bout... ;-)

 

[JAE]

All,
After reading through WillisV's post back in August 2006, which walterbrennan linked to above, I still feel that partition loads are not reduceable.

I understand that flow of logic in the ICC response that WillisV got from them. I just disagree with that ICC person's take.

The logic from ICC was something like this:
1. The LL reduction allowed by the code SPECIFICALLY refers only to the loads listed in the LL table.
2. However, section 1607.3 states that despite the LL table, you should use higher live loads if they might occur.
3. THEREFORE, if you use higher live loads than in the table, technically you can't reduce them because the LL reduction is ONLY allowed for loads in the table.
4. THEREFORE, if these other, higher live loads should be reduced, so should partition live loads.

This is pretty awkward reasoning and I don't buy it.
(Keep in mind that the best sources of loading criteria are from the ASCE 7 committee and not ICC personnel).

Because of the original historical source of the partition loading I posted above - that it was an attempt to include the additional floor loading that would occur via partitions [red]AND[/red] egress live loads of 100 psf in variable locations - the partition live load doesn't really fall into the same statistical category of the primary floor live load.

Neither of these two "reasons" for the partition live load fall under the concept of lower statistical risks of full load over larger areas - which is the true rationale for LL reduction in the first place.







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[walterbrennan]

JAE,

Thank you for your diligent responses. I think it's fair to say that until the code-writing body puts this to bed one day (assuming they ever will), this will probably continue to be a hotly debated issue of principle. Also, while I agree with you that ASCE's committee on loads is the appropriate source of all things live load, they don't seem to have done any better job of saying it out loud one way or the other.

As to the ICC personnel opinions... it might be worth remembering that ASCE 7 doesn't even become code, until it is adopted (with or without modification) into a model code, like the IBC. On that basis, alone, I have known many building officials over the years who take the opinion of the ICC very seriously, in the absence of a clear counter-opinion from ASCE.

Again, thanks for your sharing your knowledge on this topic. I've enjoyed reading your stuff over the years. ;o)