Chapter 3. Wind Design and Evaluation Criteria

DOE-STD-1020-2002

Chapter 3

Wind Design and Evaluation Criteria

3.1

Introduction

This chapter presents a uniform approach to wind load determination that is applicable to

the design of new and evaluation of existing structures, systems and components (SSCs). For

existing SSCs, Figure B-2 (in Appendix B) may be utilized appropriately and judiciously. As

discussed in Appendix D.1, a uniform treatment of wind loads is recommended to accommodate

straight, hurricane, and tornado winds. SSCs are first assigned to appropriate Performance

Categories by application of DOE-STD-1021. Criteria are recommended such that the target

performance goal for each category can be achieved. Procedures according to the wind load

provisions of current version of ASCE 7 (Ref. 3-1) are recommended for determining wind loads

produced by straight, hurricane and tornado winds. The straight wind design basis is derived

from the national wind map in Figure 6-1 of Reference 3-1 except in few cases where hazard

models for DOE sites published in Reference 3-2 are used to establish site-specific criteria for

these few DOE sites. For other sites, the wind/tornado hazard data shall be determined in

accordance with DOE-STD-1023. Tornado hazard is based on recent studies conducted for

various NNSA sites (Reference 3-14). Use of the same methodology is recommended for use by

sites other than NNSA sites, and the tornado hazard curves should be developed for sites with

tornado hazard (Reference Table 3-2).

The performance goals established for Performance Categories 1 and 2 are met by model

codes or national standards (see discussion in Appendix B). These criteria do not account for the

possibility of tornado winds because wind speeds associated with straight winds typically are

greater than tornado winds at annual exceedance probabilities greater than approximately 1x10-4.

Since model codes specify winds at probabilities greater than or equal to 1x10-2, tornado design

criteria are specified only for SSCs in Performance Categories 3 and higher, where hazard

exceedance probabilities are less than 1x10-2.

In determining wind design criteria for Performance Categories 3 and higher, the first

step is to determine if tornadoes should be included in the criteria. The decision logically can be

made on the basis of geographical location, using historical tornado occurrence records.

However, since site specific hazard assessments are available for the DOE sites, a more

quantitative approach can be taken. Details of the approach are presented in Appendix D. The

annual exceedance probability at the intersection of the straight wind and tornado hazard curves

is used to determine if tornadoes should be a part of the design criteria. If the exceedance

probability at the intersection of the curves is greater than or equal to 2x10-5, then tornado design

criteria are specified. By these criteria, tornado wind speeds are determined at 2x10-5 for PC-3

and 2x10-6 for PC-4. If the exceedance probability is greater than 2x10-5 only the effects of

straight winds or hurricanes need be considered. For straight winds and hurricanes, wind speeds

are determined at 1x10-3 for PC-3 and 1x10-4 for PC-4.

3-1