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RE: FW: ASCE wind on parapets

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We don’t add them for each parapet, sorry if I confused you.  Windward is on the ‘front’ parapet, and leeward is on the ‘back’ parapet.  We add them only as the front and back loads.

 

Jason

 

WCA Structural Engineering, Inc.

 

From: Michael Liew [mailto:michaelliew4(--nospam--at)gmail.com]
Sent: Monday, December 08, 2008 5:29 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: FW: ASCE wind on parapets

 

The 1.5 for windward parapet and the 1.0 for leeward parapet, each one of these coefficients, has already accounted for the "front and back effect of a single parapet's wind pressure on MWFRS".  ASCE 7-05 commentary page 301 has addressed this.

 

Michael.

On Mon, Dec 8, 2008 at 3:32 PM, Jason Christensen <jason(--nospam--at)wcaeng.com> wrote:

 

Just a note, adding them is for the MFWRS.  When designing for C&C they would be separated.

 

Jason

 

WCA Structural Engineering, Inc.

 

From: Jason Christensen [mailto:jason(--nospam--at)wcaeng.com]
Sent: Monday, December 08, 2008 4:05 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: ASCE wind on parapets

 

We used to hold them separate, but we were called on it on a couple of peer reviews.  We now add the two loads.

 

Looking at example 3 of the "Guide to the Use of the Wind Load Provisions of ASCE 7-02" (granted old code, but it is still the same provisions) the two loads appear to be combined.  As I was taught, windward = pressure, leeward = suction, in the end they act in the same direction.

 

 

Jason Christensen, S.E.

 

Project Engineer

WCA Structural Engineering, Inc.

 

From: Michael Liew [mailto:michaelliew4(--nospam--at)gmail.com]
Sent: Monday, December 08, 2008 3:32 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: ASCE wind on parapets

 

Joe,

 

I use 1.5 for the windward parapet and 1.0 for the leeward parapet.  I don't combine them.

 

Michael Liew

 


 

On Mon, Dec 8, 2008 at 1:35 PM, Joe Goldbronn <jgoldbronn(--nospam--at)barrish.com> wrote:

How are the wind forces on parapets to be applied to the MWFRS (section 6.5.12.2.4)?  Are you to apply both the +1.5*q windward and the -1.0*q leeward pressures onto the same parapet?  This would in essence create a 2.5*q total force on each parapet of a structure.  This seems to be a larger force than I would expect for the parapets which makes me wonder if I am interpreting the code correctly.

 

Joe Goldbronn, PE