Figure D-1 Straight Wind and Tornado Regions of Wind Hazard Curves

DOE-STD-1020-2002

required in the design to achieve the performance goal. The ratio is largest for SSC Performance

Categories 1 and 2, and is progressively smaller for Performance Categories 3 and 4 for winds

and tornadoes. The trend is just the opposite from earthquake design. The reason for the

decreasing trend in wind is because we use smaller hazard probabilities and thus need a lessor

degree of conservatism in Performance Categories 3 and 4.

Conservatism can be achieved in design by specifying factors of safety for Allowable

Stress Design (ASD) and load factors for Strength Design (SD). These factors for straight wind

should be obtained from applicable material design standards. Consistent with the ratios in

Table D-2, the loading combinations recommended for tornado design and evaluation of DOE

SSCs are given in Table D-3.

Figure D-1 Straight Wind and Tornado Regions of Wind Hazard Curves

D-4