Performance Category 1

DOE-STD-1020-2002

3.2.1 Performance Category 1

The performance goals for Performance Category 1 SSCs are consistent with objectives

of ASCE 7 Building Category II, Ordinary Structures. Similar criteria in model building

codes such as the current International Building Code, IBC 2000 (Ref. 3-3) are also

consistent with the performance goal and may be used as an alternative criteria. The wind-

force resisting system of structures should not collapse under design load. Survival without

collapse implies that occupants should be able to find an area of relative safety inside the

structure during an extreme wind event. Breach of structure envelope is acceptable, since

confinement is not essential. Flow of wind through the structure and water damage are

acceptable. Severe loss, including total loss, is acceptable, so long as the structure does not

collapse and occupants can find safe areas within the building.

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In ASCE 7, wind design criteria is based on an exceedance probability of 2x10

per year.

The importance factor is 1.0.

Distinctions are made in ASCE 7 between buildings and other structures and between main

wind-force resisting systems and components and cladding. In the case of components and

cladding, a further distinction is made between buildings less than or equal to 60 ft and

those greater than 60 ft in height.

Terrain surrounding SSCs should be classified as Exposure B, C, or D as defined in ASCE

7. Gust effect factors (G) and velocity pressure exposure coefficients (K) should be used

according to the rules of the ASCE 7 procedures.

Wind pressures are calculated on walls and roofs of enclosed structures by using appropriate

pressure coefficients specified in ASCE 7. Internal pressures on components and cladding

develop as a result of unprotected openings, or openings created by wind forces or missiles.

The worst cases of combined internal and external pressures should be considered in wind

design as required by ASCE 7.

SSCs in Performance Category 1 may be designed by either allowable stress design (ASD)

or strength design (SD). Load combinations shall be considered to determine the most

unfavorable effect on the SSC being considered. When using ASD methods, customary

allowable stresses appropriate for the material shall be used as given in the applicable

material design standard (e.g. see Reference 3-4 for steel).

The SD method requires that the nominal strength provided be greater than or equal to the

strength required to carry the factored loads. Appropriate material strength reduction factors

should be applied to the nominal strength of the material being used. See Reference 3-5 for

concrete or Reference 3-6 for steel for appropriate load combinations and strength reduction

factors.

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