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Adding a bit to the comments already made - and giving the disclosure  
that I am neither an architect nor an engineer....

The distribution of the weight becomes critical and most of the dead  
load issues (this is what is referred to as a dead load as opposed to  
a live load) relate not only to the load on a square foot basis but  
on the overall load that the structure can handle. For example - even  
with 150 pounds per square foot does not assume that EVERY square  
foot of the structure will be loaded to capacity. Further there are  
other dead loads involved - such as the weight of the structure itself.

Another really important issue is that while the structure may have  
been designed for a certain load - that does not necessarily mean  
that the "as built" will meet that precise load  - unless it was  
specifically built and tested to meet that spec. after construction -  
there is a long list of shortcuts that can be made during  
construction that can severely reduce the designed load - that is why  
architects frequently design to a much higher spec. then a building  
will normally require for its intended use - because sometimes things  
happen - like the concrete not being exactly what was specified or  
there being issues with some of the rebar that was sitting in the  
rain a bit too long - and so forth.

Also - as a building ages the load handling capacity can change very  
dramatically - for example concrete spall is very common in older  
buildings and can have a very dramatic impact on the floor load.  
Buildings that may have been subjected to previous stress for any  
number of reasons may have  experienced settling or structural shift  
or changes that can cause a big change in load capacity as well. In  
the not too distant past a building that I was involved with did a  
series of core tests on the roof to determine load capacity and we  
were shocked at the results - it seemed that years of water  
penetration had caused the concrete to change. The proposed addition  
of a patio was out of the question and further work needed to be done  
to verify that it would be safe just doing what it was doing as a  
regular roof.

When walking around Manhattan these days many of the buildings have  
scaffolding up - that is to comply with "local law 10"  (http:// 
query.nytimes.com/gst/fullpage.html? 
res=9D04E6D6163DF931A1575AC0A960958260) that relates to masonry  
pointing - seems that there are many buildings that need work just  
because of exposure over time to the elements and pollution.... there  
are many factors that can change the actual load capacity of a  
building. Total catastrophic collapse of buildings is very rare these  
days due to modern structural design - where the load is distributed  
throughout the structure. The idea is not to have just a few points  
of failure, but that does not mean that damage does not occur. Beams  
can shift and bend, and the damage is not necessarily visible.

There is a very interesting book on this subject - Why Buildings Fall  
Down: Why Structures Fail by Levy, Salvadori and Woest

So - I wanted to underscore the comments made and suggest that you  
really speak to an engineer and do some tests on the structure and  
get an idea of what the real issues are on this specific structure in  
the specific condition it is in at this time, and that you seriously  
examine this issue.

jim



Jim Lindner

Email: [log in to unmask]

   Media Matters LLC.
   SAMMA Systems LLC.
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On Dec 20, 2006, at 2:52 PM, Richard L. Hess wrote:

> Hello, Nicole,
>
> this is always a difficult question.
>
> Are you using stationary or moving-aisle shelving?
>
> This should never be done on this scale without consultation with a  
> structural engineer.
>
> The basic figuring is fairly easy to get close, but the calculation  
> details should be reviewed with the structural engineer.
>
> First order approximation for fixed-aisle shelving.
>
> Take the linear footage weight of the records (assuming that the  
> shelves will all be 12" deep and you won't make 10" deep shelves  
> for the 10" records), multiply the weight per linear foot by the  
> number of shelves high you plan to stack them.
>
> For moving aisle shelving, you're essentially done as the full load  
> per square foot is what is required.
>
> You should also have a count of how many records per linear foot.  
> For fixed-aisle shelving, you'll need to figure out the ratio of  
> square footage of shelving to aisles and then apply that so you  
> effectively spread the weight across the whole room, but beware  
> that the structural engineer will also want to know point loads as  
> for moving aisle shelving.
>
> 150 pounds per square foot is low for moving aisle shelving for  
> videotape storage, so I suspect it's even less adequate for moving  
> aisle storage for vinyl/shellac.
>
> Cheers,
>
> Richard
>
> At 01:43 PM 2006-12-20, Nicole Blain wrote:
>> Hello all,
>>
>> Does anyone know what the standards are for floor load capacity  
>> for stacks of 12" vinyl and 10" shellac discs.
>>
>> The standard for library book stacks is ~150 pounds psf.  I tried  
>> and failed to find anything on the internet that specifies vinyl  
>> and/or shellac.  I imagine it would be higher for the latter.  If  
>> there's an official document or study out there too, it would help  
>> convince the architects/engineers that this is an important issue.
>>
>> I found an article in the Fall 1993 ARSC Journal: Storage of Sound  
>> Recordings by Richard Warren Jr.  He has weight per linear foot,  
>> but not floor load capacity.
>>
>> Our collection houses ~175,000 12" vinyl and ~30,000 10" shellac  
>> discs.
>>
>
> Richard L. Hess                   email: [log in to unmask]
> Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
> Detailed contact information: http://www.richardhess.com/tape/ 
> contact.htm
> Quality tape transfers -- even from hard-to-play tapes.