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Re: How Do You Interpret 1997 UBC Paragraph 1607.1?

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Bill,

See response below:

> This came up in a discussion with an attorney today.
>
> The referenced paragraph states:
>
> "Live loads shall be the maximum loads expected by the intended use or
> occupancy but in no case shall be less than the loads required by this
> section."
>
> Now, in the case that I'm consulting on, the EOR has repeatedly denied all
> responsibility from problems with a parking deck structure based on the
fact
> that "they used the loads prescribed by the building code."
>
> However, one line of inquiry has been that the loads applied by
> "pleasure-type vehicles" possibly exceed those prescribed in 1997 UBC
Table
> 16-A and in 1607.3.3 "Concentrated Loads".
>
> This leads to two questions that I'd like to be able to answer succinctly
> for my client the shyster:
>
> 1) How does one determine if "the maximum loads expected by the use"
exceed
> and should take the place of "loads required by this Section [i.e. UBC
> Section 1607 "Live Loads"]?

The engineer should ask about the intended use and possible access in
determining the loading criteria, however this works both ways and the owner
/ architect should inform regarding non-conventional use requirements.

We recently completed a design for a parking structure where the owner of
the resort likes to hold events on the upper deck and required 100 psf live
load.

Another issue is what you deem a pleasure type vehicle.  In the code
pleasure vehicles are intended to be regular cars.  RV access can be a real
nightmare.  On a recent project where RV access was possible on the upper
deck we arrived at equivalent loading similar to H-15 highway loads.  Some
of these RV buses and tour Buses are LARGE.

Fire Truck access is another issue.




> 2) Assuming that such a determination must be made, how have such loads
been
> arrived at?
>
> Regarding the second question in particular I have noticed that ASCE
> publishes a "Design Live Loads for Parking Garages." I have ordered this
> publication, but in the meantime the abstract published on the ASCE
website
> mentions that the publication (which appears to be a monograph) concludes
> that the 50 psf prescribed in UBC could rationally be reduced to about 40
> psf, but that in many (most?) cases the standard reductions allowed by the
> Code should not be taken. Anyone have any comments on this?
>

We tend to be a little conservative in taking reductions, but the reductions
are permissible and many structures designed this way have performed well
for many years.  The loading is arrived at the same as for any other
structure, comparing load vs. area of application with consideration for
point loading.  The big issue with larger vehicle access becomes the wheel
loading which will control over any rationale of distributed loading.

Paul Feather


>
> William L. Polhemus, Jr. P.E.
> Polhemus Engineering Company
> Katy, TX, USA
> Phone (281) 492-2251
> FAX (281) 492-8203
> email bill(--nospam--at)polhemus.cc
>
>
>
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