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Building corner wind effect - when is a corner a corner?
- To: seaint(--nospam--at)seaint.org
- Subject: Building corner wind effect - when is a corner a corner?
- From: Jim Wilson <wilsonengineers(--nospam--at)yahoo.com>
- Date: Fri, 10 Sep 2004 11:04:33 -0700 (PDT)
ASCE 7-02 Figures 6-3 and 6-17 illustrate that the end zone of a wall receives a higher negative wind loading for components and cladding. But there is no end zone treatment along the leeward edge of the roof.
BOCA Figure 1609.8.2, on the other hand, does treat the roof edge as a building corner for components and cladding. My intuition tells me that BOCA is right on this, but I would otherwise prefer to follow the more current recommendations in ASCE.
To complicate my interpretation more, I am designing to the Mass Building Code which is modeled on BOCA 1993. They provide tabulated wind pressures by elevation, zone (location within the state) and exposure. Corner type areas are defined as "The salient corner shall be defined as the vertical surface located within a distance of 1/10 the least width of the structure, but not more than ten feet, from a prominent (salient) corner." A "prominent (salient) corner "sounds like it should include the roof edge.
Thus my question - When is the roof edge considered a "corner" for increased wind loads on components and cladding? I have already concluded and designed my system for corners at the roof. But now that the contractor did not install the roof edge as if it were a "corner".....
Jim Wilson, PE
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