Historical NBCC Parking Structure Live Loads (Canada)

[KootK]

I need to know the code specified live loads for parking structures according to the 1977 and 1980 versions of the National Building Code of Canada. I've been led to believe that, at some point in time, the loading dropped from 3.6 kPa to 2.4 kPa. If anyone has some dusty NBCC's on their bookshelf, it would be a great help.

Thanks,

KootK

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[jayrod12]

I looked for those specific years. Didn't find them. The only one I could see was '85 and it said 2.4kPa for passenger cars

 

[ajk1]

According to my 1980 NBC, Table 4.1.6.A. the specified live load was
2.4 kN/m2 for garages used by passenger cars,
6.0 for garages for unloaded buses and light trucks,
12.0 for loaded buses and trucks and all other trucking spaces.

I don't immediately see the 1977 NBC, but both my 1965 and my 1970 NBC both gave 50 psf, 125 psf and 250 psf for the above 3 categories, which us the same loading as listed above. So I would think the 1977 NBC is the same.

However, my 1960 NBC gave 75 psf for passenger car garages.

The 1968 City of Toronto Building by-law (which we used to call the Toronto Building Code) specified 75 psf for garages for passenger cars (75 psf = 3.6 kPa). My recollection is that for buildings in Toronto we used the Toronto Building Code until 1975 when the Ontario Building Code took over.

I think though that you should check your provincial Code to be absolutely sure, because it may be that the provincial Code did not necessarily follow the NBC.

 

[KootK]

That's just what I needed. Thank you gentlemen.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[BAretired]

Garages for passenger cars:

NBC 1970------- 50 psf​

NBC 1977------- 2.4 kPa​

BA

 

[KootK]

@ BA: do you know if the ABC might have differed from the NBCC during the period in question?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[BAretired]

@KootK,
Prior to 1974, there was no Alberta Building Code. The City of Edmonton followed the Uniform Building Code as far as I can remember. I can't be certain about the design load for parking structures at that time but I would be surprised to learn that it differed from the current value of 50 psf (2.4 kPa).

In all editions of the Alberta Building Code, the structural aspects of the code, including loads for various uses and occupancies, have been taken directly from the NBC.

BA

 

[KootK]

Thanks BA. By Uniform Building Code, do you mean the old US code?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[ajk1]

The 1979 and 1985 Uniform Building Codes both gave the live load for "General storage and/or repair" as 100 psf, and for "Private pleasure car storage" as 50 psf.

Why do you ask the question? If you are reviewing an old garage, there may be some reduction in strength if it has not been kept in good repair, or if the repairs have not been carried out properly.

There is of course the requirement to resist concentrated loads as well - these are most likely critical for relatively short spans.

Interestingly, but not really relevant to your question, the 1949 NBC gave the loading as 100 psf!

 

[ajk1]

I need to make a correction to my comment about the 1949 National Building Code. Looking at the front cover, I see that was an American publication called National Building Code, and not the National Building Code of Canada. Sorry.

 

[KootK]

Thanks for the clarification ajk1. The context for my question is that we're looking to place a new asphalt surface over an existing, indoor, precast hollow core parking deck. Just trying to find some extra capacity.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[BAretired]

The UBC was used by some states in the USA prior to 2000, I believe primarily in the western USA according to the attached Wikipedia article.

If I remember correctly, Harold Collins, Chief Building Inspector for the City of Edmonton in the 1970's held the view that Alberta should adopt the UBC in preference to the NBCC because he believed it dealt more thoroughly with most issues and was easier for plan checkers to interpret than the NBC. I hope I am not misquoting him as he died quite a few years ago and is unable to refute or clarify my comment.

http://en.wikipedia.org/wiki/Uniform_Building_Code

BA

 

[KootK]

Thanks BA, that's a good tale. It would take some gumption to specify a foreign code when there's a local one available. I must admit, however, that I'd be quite pleased if Canada and the US came up with unified codes across the board, similar to S136.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[ajk1]

I realize that I may be a off the thrust of your question, but the Algo Mall collapse was a precast hollow core slab on steel beams, and a corroded weld on one of the steel angles supporting a beam was attributed as the main cause of the collapse. So you will want to conduct a very thorough investigation of the current condition of the garage before accepting any additional loading. Likely you already know that.

 

[KootK]

I'm always grateful for a tip from a knowledgeable colleague AJK. For this project, I'm acting as a sub to my company's restoration group. They've got the durability and condition assessment aspects well in hand. As long as I've got your attention, there's a supplemental question that I'd like to put forward. The only way that I can make the existing system work with the new load applied is as follows:

1) Use the NBCC commentary appendix L to lower my load factors. Gamma_LL = 1.20; Gamma_DL_1.08. It's not ideal but it's easily justified based on the code provisions.

2) Lower my live load from 50 psf to 30 psf. In several parking industry design references, I've seen statements saying that, statistically, a fully loaded parking structure is only subjected to a live load of 25-30 psf. I feel that this will be particularly true for my underground residential parking facility as it's unlikely that there will be heavy trucks down there.

Obviously, employing both of these strategies simultaneously makes for a very aggressive analysis. At the same time, my gut feel is that the existing structure will be fine. But, then, what does my gut know really?

The question: how crazy do you think this is? Be merciless...

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.