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ASCE 7-98 Wind Pressure Questions
- To: <seaint(--nospam--at)seaint.org>
- Subject: ASCE 7-98 Wind Pressure Questions
- From: "Dickey, David" <David.Dickey(--nospam--at)mhgrp.com>
- Date: Tue, 22 Oct 2002 17:00:09 -0400
In C6.5.5 of ASCE
7-98, it states that design for applications of serviceability, design using maximum likely events, or other
applications, wind speeds associated with the mean recurrence intervals
other than 50 years may be used by multiplying the design pressures by the
factors in Table C6-3. Has anyone used this clause to justify using
smaller (or larger) pressures?
Because ASCE 7
doesn't specify serviceability requirements, it is common to adjust levels of
acceptability. For deflection, L/360 may be changed to L/240,
or H/500 changed to H/250...for vibration, a reduced acceleration,
etc... But, what situations would warrant a change in the Return
Another question, in
ASCE 7-98, the directionality factor has been separated from the load factor and
is now included in the equation for velocity pressure. Consequently, the
velocity pressure is reduced by 0.85 while the new load factor is increased
from 1.3 (in ASCE 7-95) to 1.6. My question is why weren't the ASD
load combinations affected? Are the wind pressures now lower for ASD
combos with 7-98 than with 7-95?
that wind speeds were adjusted in the hurricane zones because of new data,
hurricane importance factors, etc..., but what about inland areas where the
90mph wind speeds stayed the same from 7-95 to