I'm curious about some developments with STD's (not what you think... Shrinkage Take-up Devices)...
My recent 3-story project has shop dwgs from Cummins, and there are take-up devices located at each level. This seems like a lot of devices... my first thought is that the supplier is flagrantly selling his products at the expense of our project and client - since we could probably easily manage the holdowns with only 2 STDs.
Looking through the calc pack that accompanied the shops however, I notice a reference to a 0.2" deflection limitation, that I had vaguely heard about in our office before, but have no direct knowledge of.
Looking through the IBC and NDS - there are no clues about limitations that potentially could affect the design of the building structure.
Looking through the ESR-1344 report, we find this nugget:
It talks about a 0.2" limit, but gives no clear rationale for why this is so - merely pointing to IBC 1604.4 which generically talks about analysis and a rational approach etc...
It is only when we look into the acceptance criteria (AC316), that we start getting some illumination. First thing we notice is the cover letter by G Nichols - indicating in item 3 that the .. errr ... "limit"... may be exceeded.... WTH!!@?!
Indeed, reading further we note in section 6 that:
So apparently the 0.2" limitation may be exceeded... you "just" have to demonstrate deformation compatibility requirements... huh?
I thought that the codes we use direct our design actions and approaches? Now we have to look at acceptance criteria for individual construction elements... for design direction...? Am I missing something...? I suppose we could motivate for the exceedance of the 0.2", but who would pay for our services for same, and do we really have enough time for yet another "meaningless" calc.
This would not be the first time we have come across something like this: recall that the stud-rail issue was also "governed by the wrong branch of government"... dictated by the acceptance criteria for stud-rails, and not code or other publications.
Seems to me like every "official" document source is vying for pole position in order to have "first crack" at directing our design... Its just becoming increasingly difficult to keep up with all the competing interests and sources...
As a personal curiosity, I'm increasingly more curious about who directs for the adoption of these " limiting " or "additional" criteria, and how it comes to influence our design world without having been through the rigors of code review and committees?
Does anyone have any light to shed on this subject?
My recent 3-story project has shop dwgs from Cummins, and there are take-up devices located at each level. This seems like a lot of devices... my first thought is that the supplier is flagrantly selling his products at the expense of our project and client - since we could probably easily manage the holdowns with only 2 STDs.
Looking through the calc pack that accompanied the shops however, I notice a reference to a 0.2" deflection limitation, that I had vaguely heard about in our office before, but have no direct knowledge of.
Looking through the IBC and NDS - there are no clues about limitations that potentially could affect the design of the building structure.
Looking through the ESR-1344 report, we find this nugget:
It talks about a 0.2" limit, but gives no clear rationale for why this is so - merely pointing to IBC 1604.4 which generically talks about analysis and a rational approach etc...
It is only when we look into the acceptance criteria (AC316), that we start getting some illumination. First thing we notice is the cover letter by G Nichols - indicating in item 3 that the .. errr ... "limit"... may be exceeded.... WTH!!@?!
Indeed, reading further we note in section 6 that:
So apparently the 0.2" limitation may be exceeded... you "just" have to demonstrate deformation compatibility requirements... huh?
I thought that the codes we use direct our design actions and approaches? Now we have to look at acceptance criteria for individual construction elements... for design direction...? Am I missing something...? I suppose we could motivate for the exceedance of the 0.2", but who would pay for our services for same, and do we really have enough time for yet another "meaningless" calc.
This would not be the first time we have come across something like this: recall that the stud-rail issue was also "governed by the wrong branch of government"... dictated by the acceptance criteria for stud-rails, and not code or other publications.
Seems to me like every "official" document source is vying for pole position in order to have "first crack" at directing our design... Its just becoming increasingly difficult to keep up with all the competing interests and sources...
As a personal curiosity, I'm increasingly more curious about who directs for the adoption of these " limiting " or "additional" criteria, and how it comes to influence our design world without having been through the rigors of code review and committees?
Does anyone have any light to shed on this subject?
1 comment:
Rob,
Thanks for bringing up the topic and putting forth your findings.
To add to the research, here is what I have found:
The background of the Acceptance Criteria:
http://www.icc-es.org/News/Articles/AcceptanceCriteria-SafelyBringingInnovative.pdf)
Discussion on the 0.200" testing requirement in the AC316:
http://www.autotighttiedowns.com/Website%202011%20Documents/2011%20COLA%20Report%2025480%20with%20requested%20revisions%20Rev%203.pdf
and...
http://www.hardyframe.com/downloads/TechBulletins/Z4-Technical_Bulletin_AC-316_11-01-13.pdf
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