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Repost: Main Wind Force Resisting System: IBC table 1609.6.2.1(1)/ASCE 7-98

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Title: Main Wind Force Resisting System: IBC table 1609.6.2.1(1)/ASCE 7-98

This is a repost. It looks like the original message may not have gone through.

Any comments would be appreciated

 

Thanks,

-Matt

 

-----Original Message-----
From:
Schwan, Martin K.
Sent:
Tuesday, May 18, 2004 4:43 PM
To: seaint(--nospam--at)seaint.org
Subject: Main Wind Force Resisting System: IBC table 1609.6.2.1(1)/ASCE 7-98

 

Dear Seaint:  I welcome your comments on why the transverse horizontal wind pressures on walls for MWFRS in the 2000 IBC table 1609.6.2.1(1) increase from roof angles (0 - 5) degrees to 20 degrees and then decrease from 20 degrees to (30< angle <= 45) degrees. For example:  110 mph, transverse horizontal pressures on wall at the end zone and the interior zone are:

 

 

Degree  EZ wall (psf)   IZ wall (psf)  
0 – 5 deg       19.2    12.7   
20 deg  26.6    17.7   
30 < angle <= 40 deg    21.6    17.2   

Similar trends are observed for vertical loads as well.  Is this an effect of the leeward pressure?  Is there any data available for review regarding a model showing how the pressures behave at different wind velocities with various roof angles? 

In the ASCE 7-98, figure 6-4, CASE A loading has a similar trend for the external pressure coefficients.  While the interior zone external pressure coefficients (GCsub pf) trend increases in building surface 1 (windward side), it decreases and then increases in building surface 4 (leeward side).  But it doesn’t appear to be the case at the end zone (see 1E and 4E for case A loading), however. 

Thank you in advance for any comments…Martin up in Anchorage…have a great evening!