# RE: Wind Loads-UBC vs. ASCE

• To: seaint(--nospam--at)seaint.org
• Subject: RE: Wind Loads-UBC vs. ASCE
• From: Steve Bigham <SBIGHAM(--nospam--at)braden.com>
• Date: Wed, 7 Mar 2001 10:29:20 -0600
```The IBC 2000 has a table with equivalent speeds (Table 1609.3.1)
Fastest Mile(mph)===> 3 sec Gust(mph)
70                  85
75                  90
80                  100
85                  105
90                  110
100                 120
105                 125
110                 130
120                 140
125                 145
130                 150
140                 160
150                 170
Linear interpolation is permitted

-----Original Message-----
From: Padmanabhan Rajendran [mailto:rakamaka(--nospam--at)yahoo.com]
Sent: Wednesday, March 07, 2001 8:16 AM
To: seaint(--nospam--at)seaint.org
Subject: Wind Loads-UBC vs. ASCE

ASCE 7-98 wind map shows maximum "3 sec. gust wind
speed" of 150 mph, whereas according to UBC 97, the
maximum "Basic Wind Speed" is limited to 130 mph. Is
there any correlation between the two terms? If not,
is there any formula for extrapolating wind stagnation
pressure for basic wind speed in excess of 130 mph,
while using UBC 97?

2. ASCE 7-88 showed the gust factors, gz, as a
function of the height 'z' along the height of the
structure.  However, ASCE 7-98 gives a single value
for gz (Sec. 6.5.8). Quick calculation indicates that
the force due to wind would be less, if calculated
with 7-98 provisions. The reduction is not
insignificant. Were the provisions of 7-88 overly
conservative or is there something in error in 7-98?

Rajendran

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```