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# RE: Wind Load Topographic Effects

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• To: seaint(--nospam--at)seaint.org
• Subject: RE: Wind Load Topographic Effects
• From: "Conrad Harrison" <metamorphs96(--nospam--at)gmail.com>
• Date: Fri, 2 Jan 2009 17:36:29 +1030

Jeff, Joe,

Tell me you are not using trig.

The pressure coefficients for building shapes are worked out on the basis of the extreme value within a quadrant, to give the worst case for bending moment, shear etc...

For the site, there are 8 compass directions for the wind, each of these can have different kz, kzt etc.., using AS1170.2 I can also effectively have different Vb. The rectangular building has two orthogonal axes. The building is located correctly with respect to the compass directions. The maximum wind speed (Vz for AS1170.2 users, ASCE7-05 users have to calculate qz) from the compass/cardinal direction within the quadrant for the orthogonal axis becomes the wind speed (or qz) for that direction. Thus only have winds along orthogonal axes normal to faces of the building for design purposes.

Once got the the values of (Vz or qz as the case may be), then loads are simply based on winds along orthogonal axes normal or parallel to faces of building. So far I have never loaded the building at 45 degrees to the axis of the building: drag forces on open frames being an exception.

{And just recieved SRSS}  I don't believe that is necessary. And for a rectangle isn't that the length of the diagonal, so what is Joe doing for the short side: taking half the length of the long side?

regards

Conrad