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Re: SIP spec

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I agree that the NTA "SIP Engineering Design" guide is the closest thing to a full rational engineering design process for SIPs that there is (at least that I am aware of).  It extends what was started with APA's Supplement #4.  I did not mention it before, however, because it is a design/analysis document, not really a specification type document.

And while it certainly can be used to in a general sense for SIPs NOT listed under the SIPA code report or any other NTA code report from some specific SIP manufacturer, you do need to keep in mind a few things.  

First, the "Design Guide" does specifically outline a "limits of use".  It says:

"This document applies to NTA, Inc. listed SIP panels only and shall not be used with unlisted SIPs or SIPs listed/evaluated by other agencies. The design shall be limited to the specific panel thicknesses described in the listing report. This document shall not be applied to spans, heights, or aspect ratios not bounded by the limits of the listing report—extrapolation is not permitted."

While that does not mean the principles do not apply to SIPs in general and could not be used at an engineer's discretion for design, it does technically preclude its use in an "official" type sense.

The second issue is that design is only one side of the issue.  You also need to have some sort of quality assurance/assessment process for any SIP that might be used.  This still usually means testing of some sort, both initially and on going.  This is kind of along the lines of concrete.  Just having the proper materials and supposedly assembling those materials in a proper manner does not ensure that the concrete will behave as intended.  That is why we typically have various concrete testing done to ensure that we are getting proper concrete strengths and such.  The same is true of SIPs.  Since they are a composite product, the final product needs to be tested to ensure that the intended behavior results.  In addition, the process of manufacturing of those SIPs needs to be monitored to ensure that a consistent product is being produced that matches what was initially tested...this is done by reviews of the production facility as well as periodic testing.  

So, the point is that while the Design Guide is great, it is only one part of the process.  You still need to have something that verifies that the SIPs were properly manufactured and that they meet the intended behavior.  This is usually done by way of a code/evaluation report process.  So, while this Design Guide can be used beyond a "listing report", it is not wise to use it with some SIPs that do not have some sort of "listing report" or some other method of verifying that the SIPs are being manufactured properly and behaving as intended on a consistent basis.

As to NTA reports vs. ICC-ES reports, I will be the first to agree that in an ideal world they would be interchangeable, assuming all other things equal.  After all, the "alternative materials" provisions in the code only call for "third-party evaluation", not "ICC-ES evaluation".  But, the reality is that this it not always the case.  Just like Coke and Pepsi are not considered interchangeable by some people even though they are both "colas", there will be some code officials that view an ICC-ES report as the only acceptable option for an evaluation report just as some people only consider Coke as the only acceptable cola.  I am not saying this is right, but merely pointing it out.  In such cases, you likely will have an uphill fight with such a code official.  Hopefully, this will change over time...either that, or we finally get SIPs directly in the code and get away from the BS of having to deal with evaluation reports altogether (NTA's Design Guide could be the "seed" for getting SIPs in the code if NTA is willing to allow a Standards committee to make use of that document in the development of a consensus Standard).  After all that, I will definitely say that while the "system" might be stupidly biased in favor of an ICC-ES report, any report is better than no report.

Regards,

Scott

On Mar 20, 2010, at 12:36 PM, Eric Tompos wrote:

Regarding engineered design of SIPs, the SIPA code report is
fundamentally different from all other reports--it is currently the only
code report that provides engineering properties for SIP panels. And,
unlike all other reports, the load tables in this report are based
entirely on engineering mechanics--not a summary of a single test.

To complement the SIPA report is a design guide (also on SIPAs web site)
which provides detailed information with respect to SIP behavior, such
as limits states and conditions effecting strength.  More importantly,
the design guide provides continuous functions which can be used to
determine the strength of a SIP for particular applications.

If you are designing a SIP project I recommend you check it out.  Even
if the SIP supplier isn't on the SIPA report, the behavioral information
can be very valuable.  Also, if you need help with engineered design
using the design guide, a manual of design examples also exists.  This
manual addresses typical design situations and provides step-by-step
calculations with commentary.  The guide of design examples does not
appear to be on SIPAs site, but you can contact me directly if you would
like a copy.

If you obtain a copy of the design guide and have any questions or
suggestions for improvement please contact me directly.

Regards,

Eric Tompos, P.E.
NTA, Inc.





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