Design Guidelines

DOE-STD-1020-2002

3.2.5 Design Guidelines

Reference 3-12 provides guidelines and details for achieving acceptable wind resistance

of SSCs. Seven principles should be followed in developing a design that meets the

performance goals:

(a)

Provide a continuous and traceable load path from surface to

foundation

(b)

Account for all viable loads and load combinations

(c)

Provide a redundant structure that can redistribute loads when one

structural element is overloaded

(d)

Provide ductile elements and connections that can undergo

deformations without sudden and catastrophic collapse

(e)

Provide missile resistant wall and roof elements

(f)

Anchor mechanical equipment on roofs to resist specified wind and

missile loads

(g)

Minimize or eliminate the potential for windborne missiles

3.3

Evaluation of Existing SSCs

The objective of the evaluation process is to determine if an existing SSC meets the

performance goals of a particular Performance Category.

The key to the evaluation of existing SSCs is to identify potential failure modes and to

calculate the wind speed to cause the postulated failure. A critical failure mechanism could

be the failure of the main wind-force resisting system of a structure or a breach of the

structure envelope that allows release of toxic materials to the environment or results in wind

and water damage to the building contents. The structural system of many old facilities (25

to 40 years old) have considerable reserve strength because of conservatism used in the

design, which may have included a design to resist abnormal effects. However, the facility

could still fail to meet performance goals if breach of the building envelope is not acceptable.

The weakest link in the load path of an SSC generally determines the adequacy or

inadequacy of the performance of the SSC under wind load. Thus, evaluation of existing

SSCs normally should focus on the strengths of connections and anchorages and the ability

of the wind loads to find a continuous path to the foundation or support system.

Experience from windstorm damage investigations provides the best guidelines for

anticipating the potential performance of existing SSCs under wind loads. Reference 3-13

provides a methodology for estimating the performance of existing SSCs. The approach is

directed primarily to structures, but can be adapted to systems and components as well. The

methodology described in Reference 3-13 involves two levels of evaluation. Level I is

essentially a screening process and should normally be performed before proceeding to Level

3-13