Criteria for Site-Specific Probabilistic Wind Hazard Assessment

DOE-STD-1023-95

The results of the probabilistic wind hazard assessment includes a mean wind hazard curve and other

information regarding the uncertainty in the hazard assessment. The wind hazard curve represents

the annual probability of exceedance as a function of wind speed at the site.

There are three types of winds: extreme (straight) wind, hurricane, and tornado. Extreme winds are

non-rotating, such as those found in a thunderstorm gust front. Tornadoes and hurricanes both are

rotating winds. The potential for all three types of winds shall be determined in the site wind hazard

assessment.

For practical purposes, the effects of hurricanes are treated the same as those of straight winds in

accordance with DOE-STD-1020-2002. As a result, both hurricane winds and straight winds will be

represented by a single straight wind hazard curve although different wind hazard models are used

for straight winds and hurricanes.

The site-specific probabilistic wind hazard assessment is characterized by the following traits:

(1)

Probabilistic wind hazard assessments shall be performed for straight winds, hurricanes, and

tornadoes.

(2)

The wind hazard assessments for straight winds and hurricanes shall be combined to produce a

single straight wind hazard curve by assuming the two types of winds are mutually exclusive

events. A composite probability distribution may be used to assess probability of exceedance

of wind speeds (Changery, 1985). It is recommended to use a Gumbel distribution (Coats and

Murray, 1985) to model straight wind hazards and a Weibull distribution (Simiu and Scanlan,

1986) to model hurricane wind hazards.

(3)

The wind hazard assessment for tornadoes shall be conducted in a manner consistent with the

methodology described in Section A3.2.2.3.

(4)

A transition wind speed is defined by the intersection point of the combined straight wind

hazard curve and the tornado wind hazard curve.

(5)

The combined straight wind hazard curve is used as the actual wind hazard curve for wind

speed up to the transition wind speed while the tornado hazard curve is used as the actual wind

hazard curve for wind speed above the transition wind speed.

(6)

The transition wind speed also determines if other tornado effects (e.g., atmospheric pressure

change (APC) and tornado missiles) need to be considered based on criteria specified in

DOE-STD-1020-2002.