Return to index: [Subject] [Thread] [Date] [Author]

[Fwd: Wind Load on Parapets]

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Fellow engineers.

	I sent the attached to the list but the scanned attachment made it too
long so I sent it direct to Reza.  I have now detached the scanned
attachment so the rest of you can see the text of what I sent.

				Regards,

				H. Daryl Richardson
--- Begin Message ---
Daryl Richardson wrote:
>
> This message is too long to be posted to this list.
> Please contact seaint-ad(--nospam--at)seaint.org if you have any problems.
>
> The original message follows:
>
> This is a multi-part message in MIME format.
>
>   ------------------------------------------------------------------------
> Reza,
>
>         The information you need to do this using Canadian NBC 1995 is
> contained in User's Guide - NBC 1995, Structural Commentaries (Part 4).
> I've scanned in the appropriate page, page 36, which applies to free
> standing walls.
>
>         For the benefit of non Canadians who may be interested I'll briefly
> describe the Canadian wind loading procedures.  In organization they are
> quite similar to the American procedures; but there are some critical
> differences.
>
> Basically,
>         f = q*Ce*Cg*Cp
>
> where   f = the wind pressure applied to the surface under consideration.
>
>         q = the reference wind pressure determined for the location.  Note: in
> Canada these vary from town to town and they are published as part of
> the building code.  The National Building Code contains the values for
> all of Canada.
> CRITICAL: ** THESE ARE BASED ON AVERAGE HOURLY WIND SPEEDS. **
> determined from the formula q = 0.000050*V^2 where V is in
> kilometers/hour with the usual 10, 30, or 100 year recurrence as
> appropriate for the subject design.
>
>         Cg = gust factor.  For simplified procedures use 2.0 for structure and
> 2.5 for cladding.  Using detailed procedures it's a rather complicated
> function of q, the natural frequency of the structure, the dimensions
> and the exposure factor (a spread sheet is very helpful for determining
> this).  Note: for wind critical structures like stacks Cg often exceeds
> 3.0 and occasionally even exceeds 4.0 when determined by the detailed
> procedure.
>
>         Ce = exposure factor.
> Exposure A, Ce = (h/10)^0.28 (open exposure).
> Exposure B, Ce = 0.5*(h/12.7)^0.5 (wooded areas or centers of large
> towns).
> Exposure C, Ce = 0.4*(h/30)^0.72 (centers of cities with many tall
> buildings).
> Note: h is in meters and the quantities inside the brackets above are
> not less than 1.0.
>
>         Cp = shape factor.  These shape factors are very much like the shape
> factors I've used in U.S. codes.  The attachment uses the designation Cf
> for the shape factor.
>
>         As a Canadian, you may find this is more than you require.  I included
> it because I thought our American friends might be interested in seeing
> an alternate procedure.  I remember Bill Polhemus in particular asking
> about the use of pressures rather than wind speeds in determining wind
> loading several months ago; this is one example of how it can be done.
>
>                                 Regards,
>
>                                 H. Daryl Richardson
>                                 Calgary
>
>   ------------------------------------------------------------------------
>
>                       Name: ~MAP0000.PDF
>    ~MAP0000.PDF       Type: Acrobat (application/pdf)
>                   Encoding: base64

--- End Message ---