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 ASCE 7-22 Overhang Internal Pressure GCPi

  • ASCE Standards
  • ASCE7-22
Chris Rosencutter's profile image
Chris Rosencutter posted 11-01-2022 08:48 AM
ASCE 7-22 has the following formula for calculating Overhang Pressures:



The GCp is the addition of the applicable Roof GCp on the top and the applicable Wall GCp on the bottom.  It would seem to me that any internal pressure would be cancelled out, since we are adding pressures from the top and bottom surfaces to get GCp, and so why does GCpi appear in equation 30.7-1?  


James Williams's profile image
James Williams posted 11-02-2022 10:39 AM
Hopefully I am reading the question correctly. In my experience, the overhang may consist of an assembly of structural components like a roof rafter and soffit support in addition to cladding. In fact, some overhangs are significantly larger and consisting of trusses or truss-like structures. Disclaimer: I have not graduated to ASCE 7-22 yet.
Christian Parker's profile image
Christian Parker posted 11-07-2022 04:35 PM
I second Mr. William's comments.  As I see it, it's similar to the code equations including GCpi for MWFRS: for most buildings this will zero out between windward and leeward surfaces, but the onus is on the engineer to convince herself that the diaphragm(s) can be relied upon to balance internal pressures.  A chord of an overhanging truss could experience combined internal and external pressure even if the web members are zeroing out internal in the overall truss flexural design.

As for 7-22 updates, it appears that the change from 7-16 is more organizational than substantive for overhangs.  This article is helpful:
https://www.structuremag.org/?p=21612