Wind Loading 3

[sniper98]

I was looking through the OBC, and realized that values for q, Cp and Cg were not given. After getting the NBCC, I found the q value, but the Cp and Cg values were still missing. I realized now the values I need are in the NBCC Part 4 Structural Commentaries. Does anyone have the wind section that they can share as an attachment; or knows a link to where it can be downloaded?

 

[woodman88]

I do not know if the IBC values match the OBC.

From the following government website I found the Cg factor.

http://www.e-laws.gov.on.ca/html/regs/english/elaws_regs_060350_e.htm

Which gives the following statements (Though I wonder why it gives no guidance for Cp)
"Section 4.1.7. Wind Load
4.1.7.1. Specified Wind Load
(1) The specified external pressure or suction due to wind on part or all of a surface of a building shall be calculated using the following formula:

p = IwqCeCgCp

where,

p = the specified external pressure acting statically and in a direction normal to the surface, either as a pressure directed towards the surface or as a suction directed away from the surface,

Iw = importance factor for wind load, as provided in Table 4.1.7.1.

q = the reference velocity pressure as provided for in Sentence (4),

Ce = the exposure factor as provided for in Sentence (5),

Cg = the gust effect factor, as provided for in Sentence (6), and

Cp = the external pressure coefficient averaged over the area of the surface considered.
..."
and "...
(6) The gust effect factor, Cg, shall be one of the following values:
(a) for the building as a whole and main structural members, Cg = 2.0,
(b) for external pressures and suctions on small elements including cladding, Cg = 2.5,
(c) for internal pressures, Cgi = 2.0 or a value determined by detailed calculation that takes into account the sizes of the openings in the building envelope, the internal volume and the flexibility of the building envelope, or
(d) if a dynamic approach to wind action is used, Cg is a value that is appropriate for the turbulence of the wind and the size and natural frequency of the structure."

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[BAretired]

Personally, I would prefer that all codes and standards be available on the internet at no cost to the user, completely free of charge. After all, Canada and each of the provinces would like folks to be aware of the latest codes when designing buildings, wouldn't they?

Unfortunately, that is not how the system works today. There was a time in Canada when codes were free to any and all users. That was because codes were subsidized by the cement companies, steel companies and other affected industries. But it got too expensive, so they stopped doing it a number of years ago.

The document you require is available at a price (I don't remember what I paid, but it was not very much). I don't know of any way of obtaining the document other than buying it.



BA

 

[CRG]

Sniper98,

You must be new to the internet and the related search engines associated with the internet because I found the file you wanted in less than a minute. I buy my codes and standards because I need a legal hard copy in case there is ever a legal dispute over one of my designs where I referenced the code. In my neighborhood the going rate for an engineer is between $80 to $150 USD per hour. It sounds like you could have purchased the documents you wanted to steal several times over for the effort you are expending.

 

[Elite7]

In India, the code writing is done by Government bodies with consultation from academia and industry. I happen to be a member of one of the committees for such a code, and I do believe that the codes should be made freely available for all to use. This will ensure that everyone is able to use the latest and best available information for their design. The cost of producing the codes is a very small one that can be supported by taxes.

(By the way, I don't receive ANY fees for my work on the code, which is all pro bono. I even have to pay my own air fare and hotel bills when attending meetings out of town.)

However, at present, the codes have to be paid for. Deal with it. If you download and use something for private study or a hobby project, that is one thing. If you use it for designing something that you get fees for, that's a different thing entirely.

How difficult is it to add the cost of a code to your fees?

 

[woodman88]

The law and codes of the government should be made available to the people for free. The users of the building code (that is, the owners building the buildings) should pay a code tax of .5%, 1%, 2% , etc. of the building cost to pay for development/use of the codes. This way the codes would be updated when needed and not every three to five years just to generate money for the publishers.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[sniper98]

SkiisAndBikes....I didn't know they put the q values in the OBC compendium, but it's not a publication that I need, because the q values in the NBCC are just as good since they cover all cities.

woodman88...That's an interesting link. It appears to be the same as the OBC clauses. As you mentioned, it doesn't tell you the Cp values; and many other values are missing. In fact, the User Guide that I am looking for tells you the CpCg values together, so I have no idea how someone is suppose to use the OBC information on it's own with all the missing information.

CRG...Can you tell me the search method you used, or share the link?

 

[CRG]

sniper98,

I won't help you break copyright laws. I would hope the moderators on the site would kick anyone off if they did. In fact, I am a little surprised that this thread hasn't been red flagged because you are asking for folks to break copyright laws and ignore basic ethical principles.

 

[sniper98]

CRG....I have already gone through a long discussion on this topic already in this thread, which was not even the intention of this thread. Please note the subject of this thread is "Wind Loading" and the query is stated below. You are entitled to your opinion, but if you want to discuss this matter, then please start a new thread under engineering ethics or legal advice, so that others can participate in this thread if they choose too.

 

[vshep]

As someone who uses the commentaries often, I suggest you bite the bullet and buy them. I am not sure how you would do any sort of wind or snow drift analysis without them. The new 2010 commentaries are now out and are well worth the cost.

 

[woodman88]

One problem I have with commentaries is that they are not usually referenced in the code as adopted by the local jurisdiction. So in reality, they have no legal validity in regard to the local building code unless the building official wants to agree with them. Using them might not be a good defense in a court situation given the argument that if that interpretation was pertinent to the code why wasn't it included in a reference document.
For this reason I feel that the commentaries are deliberately left out of the document so they can double charge you for the information they should be giving you in the first book.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[sniper98]

vshep...if nobody knows of a filesharing link, then I may just need to get it the old fashioned way. Almost everything else imaginable is online, except this NBCC Part 4 Structural Commentaries user guide, which is a surprise to me.

woodman88...I agree with you, the commentaries are only a guide that you use at your own risk. But I don't know of a better resource to use, so I think everybody is stuck in using it.

 

[BAretired]

Actually, the commentaries are referenced in Appendix A of the NBC. They are more than a guide, they are official.

BA

 

[vshep]

sniper98, I could not find a link online at all. Buy it now and claim it on your taxes as a business expense for 2011. I personally think it's ridiculous it's not included in the NBCC code, its essential!

 

[sniper98]

vshep...Thanks for the effort. You are right, I couldn't find it anywhere either.

BAretired...Good point, they are referenced; but unfortunately they don't provide the CpCg values in the same place.