Historic Steel Deck Institute Design Information 1

[zurch1818]

I am in the process of analyzing an existing composite deck building from 1973. In the plans, it is called out to have a design roof live load of 30psf and doesn't say anything about snow load. This site is in the UP right on Lake Superior, so the ground snow load is 70psf and the balance snow load is closer to 50psf, so I am a little concerned for how the decking is going to perform. The decking also spans 10', which seems far without actually crunching any numbers. I do have good information for what the decking is, I just don't have an easy way to calculate its capacity.

For steel joists, there is a 75 year catalog that has all of the historical joist information and span tables. However, I cannot seem to find something equivalent for the steel decking. If it helps, in one of our old projects, I was able to find this page from an old decking catalog, but it is too new for my building. The part that is highlighted is not what I have on my building. Can someone point my in a direction to find the right catalog that would have been current in 1973?

I'm guessing that I'm going to have to hand calc the deck's capacity because the span isn't even on the table below. Seeing that my building is only a few years older than the catalog's date, I'm anticipating that the design assumptions/material strengths that are made on page 4 above were the standard for my building. Can someone confirm if this is a reasonable assumption? If not, what should be considered instead?

Thanks for the help!

 

[Guastavino]

Hi,

So Email Bob Paul at the SDI (steel deck institute). Tell him what you've got and he will help you. He stock piled all the old catalogs of that. He only shares them on a case by case basis. I've told him I would buy them from him and he said for liability reasons the SDI won't publish everything (or at least I think that was his reason. It made sense). With that said, he doesn't mind sharing them at no cost. He just doesn't want to upload all of them to the internet without discretion.

Best,

Nick

 

[JAE]

You said "composite deck". But what you show in that catalog image is roof deck. I'm presuming you are talking about roof deck and not composite deck correct?

I have a copy of the SDI 1984 catalog, a Wheeling Roof Deck catalog from 1982, and a copy of a Vulcraft 1980 but nothing back to 1973. Not sure the numbers have changed all that much over that time period.



Check out Eng-Tips Forum's Policies here:
faq731-376

 

[JAE]

slideruleera.net has a Robertson Catalog from 1975 found HERE


Check out Eng-Tips Forum's Policies here:
faq731-376

 

[zurch1818]

Thanks for the replies. Yes, I am talking about a composite beam and I am checking the decking for a fairly large point load. I already determined that the beams are strong enough but wanted to verify the capacity of the roof decking. It is a very odd design where the CMU block penthouse wall bears down directly in the midspan of a 35' long composite beam. I can see why they did it, but it definitely isn't the most efficient design.

 

[JAE]

zurch1818 - pardon me here but I'm still not clear on what you are dealing with.

Your first post said "composite deck". Your image is of non-composite roof decking (narrow, intermediate, and wide rib).
You then state you are looking at a composite beam with a CMU wall load on the beam - but then you say you are checking the decking for a point load - on the roof deck?

Perhaps a more comprehensive description would help me understand what you are asking.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[zurch1818]

I have W18x77 (which isn't even a current size W shape in today's AISC manual) partially composite beams with 58 total studs (29 on each half). I verified that the composite beam with steel and concrete is sufficient to carry the additional loads associated with my project. Now I just wanted to verify that the decking has enough capacity to carry the proposed loads. The beams are spaced at 10' O.C., so I am verifying that the deck can carry the load. It acts perpendicular to the composite beam. I am going to conservatively assume it is simply supported initially and then move on to determining if it will work as a 2 span or 3 span condition. If the decking cant carry the load, I will have to propose some sort of sleeper beam to span between the composite beams. The concrete that is on the decking only has enough steel in it for temperature and shrinkage, so the decking must have to carry the proposed loads.

I only brought up the CMU wall just to describe the situation. I I didn't have any questions on that. I just thought it was interesting. On the floor below, there are less columns than on the penthouse level, so the original design increased the size of the composite beams to carry the point loads from the penthouse to the columns on the floor below. It just so happens that the CMU wall just happens to come down in the midspan of the composite beam...which is probably the worst place to have a point load come down on a beam that is being controlled by flexure.

My question was just on what historic information was available for the decking because I couldn't find anything that went far enough back in the past for the age of my structure. I know how decking is constructed today, but I didn't have a clue for what was standard for in the 1970's. I got some great information from the replies that I received and I consider my question resolved and I appreciate the promptness of the responses. This site is such an awesome resource! Thanks again!

 

[JAE]

The concrete that is on the decking only has enough steel in it for temperature and shrinkage, so the decking must have to carry the proposed loads.

So there's concrete on the decking - if the deck is the type you posted above, it is NOT composite decking but roof decking with concrete on it.
Roof decking does not have deformations on the deck sides so there is questionable bond between the concrete and roof deck.
That would mean that your deck is supporting all the dead weight of the concrete and the applied supplemental dead loads as well as live loads as you suggest.

If the decking is a composite type - with deformations or ripples on the sides, then the deck itself is the reinforcement for the deck-concrete system and the temperature/shrinkage reinforcement is only that - just T&S steel. The deck would have significantly more strength than just a smooth roof deck with concrete on it.





Check out Eng-Tips Forum's Policies here:
faq731-376

 

[txeng91]

It’s typical for composite decks to be designed as simply supported so the number of spans may not matter. I’ve analyzed a couple of structures from around the same timeframe and they both had 2” Robertson deck. What everyone is asking is if the decking itself is composite or not, not just the beams. Composite decks have embossments on top of the deck to tie into the concrete, so you can get greater capacities and span lengths than what’s shown on the page you posted with non-composite decking. At a 10’ span it’s probably 18 gauge, but maybe lighter if it’s a roof.

 

[wannabeSE]

zurch1818,

Do you have any information on the deck? Sometimes, old manufactures catalogs can be found that have deck's capacity. I think some early composite deck capacities were determined by manufacture's testing. I second njlutzwe suggestion to contact the SDI. They have helped me in the past.

 

[zurch1818]

Sorry I didn't make it clear enough what I had. Here is a screenshot from the slab notes. On the roof level, I have 20 gage composite deck. The general notes also say that it is a composite deck for everything above ground level. I don't have any specs on the building. I am going to reach out to SDI about the decking tomorrow when I get back into the office. It is good to know they will be helpful. I know ACI has a reduction lambda for using lightweight concrete...however, I don't recall seeing a similar provision in AISC. Is this something that I should account for? Thanks again.