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RE: ASCE wind on parapets

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Your code seemed fairly explicit: Windward parapet and Leeward parapet. Not
the windward and leeward sides of the same parapet. To check stability of
the whole building then need to load the windward (+1.5) and leeward
parapets(-1.0) at the same time.

As I indicated the windward parapet is loaded by the windward exterior wall
pressure coefficient (say +0.7 towards) and the interior face by pressure
equivalent to that on the roof surface (say -0.9 away), to get a net
coefficient of (1.6 towards roof. Cf. +1.5).

The leeward wall pressure coefficient given in ASCE7 indicates some positive
wall pressure on the interior face plus the suction on the exterior face.
The exterior leeward wall would vary from say -0.2 to -0.5, combined with
+0.7 for wall on interior face: then average to give a general value. This
indicates that the pressure on the roof in the immediate vicinity of the
parapet is likely to be positive pressure not the suction experienced by the
rest of the surface. The effects of turbulence produced coming from the roof
and hitting the wall is thus different than that produced when it leaves the
edge of wall and hits the roof.

I haven't time to do so at present, but check shapes for saw tooth and
multi-span roofs. The saw tooth should give a down slope to vertical wall
coefficient; it should be comparable with the parapet.


Regards
Conrad Harrison
B.Tech (mfg & mech), MIIE, gradTIEAust
mailto:sch.tectonic(--nospam--at)bigpond.com
Adelaide
South Australia



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