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Number of Load Tests Required for Structural Significance

Number of Load Tests Required for Structural Significance

Number of Load Tests Required for Structural Significance

(OP)
I'm helping a client come up with bending capacities for a new curtain wall system split vertical mullion. It's sketchy stuff so I'm recommending some testing. I'll have to come up with a testing program though and that's currently where I'm stuck. I would have thought that there would be a standard out there for testing structural things. You know, this many tests if you want to be at this confidence level. Does anybody know of such a standard? Or is time to bust out stats for engineers and go first principles on it? The blurb below comes from Canada's aluminum standard.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Number of Load Tests Required for Structural Significance

Are your mullions aluminum? Why not just use that standard you posted?

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RE: Number of Load Tests Required for Structural Significance

(OP)
They are aluminum. Aluminum separated by a structural composite thermal break. And yeah, I will go with that if I can't find anything more definitive. There's also:

- ASTM E529 - Standard Guide for Conducting Flexural Tests on Beam and Girders for Building Construction. All they say is at least two tests and it depends how much confidence you want to have.

- ASTM E330 - Standard Test Method for Structural Performance of Exterior Window... I believe that this is the most common testing but I'm unclear if it's appropriate for product development or is meant only for project specific verification. This test would have the the mullions LTB braced by the glass. I'm not sure that's appropriate for this kind of investigation.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Number of Load Tests Required for Structural Significance

Have you ever practiced in South Florida? In Miami Dade County there is a local requirement for a "NOA" or Notice of Approval which constitutes a testing process for enclosure elements. I am not particularly familiar with the required testing processes, however, Miami Dade county lists the approved laboratories for performing the required testing. Although a number of them are located in Florida, there are a number throughout the U.S. If I was in your position I would randomly call some of these guys and pick their brain. I'm sure potential testing of your system is enough "carrot at the end of the stick" for you to get an idea of what is industry standard.

https://www.miamidade.gov/building/library/guideli...

RE: Number of Load Tests Required for Structural Significance

Is this that deal you posted some months back that had the thingy that had to button together to work? If so, you couldn't test that thing enough for me!

You may want to try searching ASCE's archives (in their Journals and the Structures Congress). Seems to me like I've seen some testing done on mullions over the years. It might get you close to a standard if they establish (with confidence) a limit.

RE: Number of Load Tests Required for Structural Significance

Somewhat unrelated .... the newish CSA-A500-16 standard for Building Guards (i.e. a life safety component) has a section on load testing. If you can get your hands on the standard, I would recommend reviewing it. In the past, pre A500 standard, I would often see balcony guard systems (typically aluminum post/picket layouts) tested only once in the lab and an engineered certification report produced. I will look more closely tomorrow, however, I believe the A500 standard is suggesting testing 2 of each main component. Generally the components of a balcony guard such as a post are stand alone and don't require lateral support from glazing and are not complicated by thermal breaks. It sounds to me that the curtain wall system is more complex and thus might require more testing than a balcony guard.

RE: Number of Load Tests Required for Structural Significance

Side question: Does A500 cover industrial guard rails and similar?

RE: Number of Load Tests Required for Structural Significance

(OP)
Thank you all for the help so far.

Quote (EZ)

Have you ever practiced in South Florida?

Haven't but you're right, the FL example may yield some good parallels.

Quote (WARose)

Is this that deal you posted some months back that had the thingy that had to button together to work?

The very same. Link

Quote (Canuck)

If you can get your hands on the standard

I've got one. I'll scan it for potential usefulness.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Number of Load Tests Required for Structural Significance

ASCE 41-13 has some guidance for material testing. Not component like it looks like you're trying to do, but may provide some guidance. Have copied screenshots for steel below since that's the one I've used recently and know where it is.



RE: Number of Load Tests Required for Structural Significance

FYI, there are a bunch of ASTM standards for wall panel testing ( http://www.fetlabs.com/testing-services-2/wall-pan... ). Take a look through and see if any of them are applicable. They won't tell you what you need to be statistically significant, but it will give you a recognized testing methodology.

See if any of your client's competitors have ICC reports, and take a look at what evidence they submitted. That might give you an idea of the standard of care.

You could also call up some labs that do the ASTM tests and ask what other people may have done.

It looks like wall assemblies might just see proof loading as standard practice?

If you want to go with a formalized analysis, S136-16 Chapter K has a simplified method of determining resistance factors that are compatible with US LRFD and Canadian LSD load factors. It's still a bit involved, but easier than starting from scratch on the statistics. Read the commentary for that section as well. It's obviously geared towards cold formed steel, but I've thought about using it before and the method is pretty well generalized. It takes the number of tests into account as well as the variability. My only worry is that their assumptions are based on the load variation for a Live+Dead combination, whereas you might be designing this based on a Wind case. There are some references in the commentary though that it says might be useful for getting revised simplified assumptions for different load conditions.

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