Robertson Section 3 Roof Deck Diaphragm Shear Capacity

[DannyVang]

I am reviewing a set of old drawings (September 1973) and wanted to see if anyone has any information to determine the allowable diaphragm shear capacity for a 1 ½” Robertson “Q” No. 3 metal deck with welds per the attached; metal deck spans 7.5 feet maximum. I have a 1975 Robertson catalog but it refers to a Robertson representative for the diaphragm capacity.

Any input is appreciated.

Thanks.

 

[JAE]

Go to slideruleera's website - there are some Robertson deck catalogs there:

http://www.slideruleera.net

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[DannyVang]

I tried slideruleera's website, and that's where I downloaded the 1975 catalog but it doesn't contain the information I am looking for.

 

[KootK]

Perhaps you can find a modern deck profile that's close enough for you to assume that the capacities would be close. I believe that the only non-fastener deck related failure mode is panel shear buckling. And, for that, you only need similar EI values. 7'-6" is a pretty good span for 1.5 inch deck. Shear buckling may well govern.

I kinda dig detail H as a deck edge collector/chord strategy. No field welding and no seat roll over. Maybe I'll try and bring that back.

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.

 

[DannyVang]

I thought about doing that and looked at ASC B-36 and Verco Type PLB-36/HSB-36 roof decks but their width is 36" instead of Robertson's which is 24". Also the weld patterns for ASC and Verco's deck are different than what's specified on Robertson's.

I like to avoid extensive calculations due to budget constraints.

 

[KootK]

I hear 'ya. With respect to shear buckling, I'm not sure that deck width matters much so long as the Ix/ft is on target. And, if you look at values for short deck spans where shear buckling won't govern, you should be able to come up with lb/fastener capacities.

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.

 

[msquared48]

If you do a "search" in this forum using "ROBERTSON Deck", there are many threads that will come up. Maybe one has the information you need.

Mike McCann, PE, SE (WA)

 

[DannyVang]

At msquare48 - I tried that already with no success. Thanks for your suggestion though.

At KootK - I haven't had to revert to providing the calc's you suggested; had always been able to rely on the published values from the catalogs. I am curious now as to how they obtain the shear capacity values they published in their catalogs. I know someone who works for ASC and will contact him for additional recommendations.

 

[KootK]

Any chance you have access to SDI's Diaphragm Design Manual? It's all in there. Of course, it's expensive and not exactly a page turner.

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.

 

[DannyVang]

No, I don't have SDI's manual, probably because I never need to...thanks for your input.

 

[JAE]

Slideruleera's site did have a Robertson No. 3 - 1 1/2" deck. I didn't see the "Q" you refer to though.



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[wannabeSE]

DannyVang
The alternative on the drawings is Inland B deck. Previously, JedClampett uploaded an Inland-Ryerson ICBO ER that includes the B-Deck shear capacity. See JedClampett's post here:

http://www.eng-tips.com/viewthread.cfm?qid=281493

 

[DannyVang]

JAE - I didn't see the "Q" as shown in the As-Built drawing also in the 1975 Robertson catalog.

wannabeSE - At a glance, I think this may be what I am looking for. Thanks!!!