Seismic Design Criteria for Structures, Systems, and Components in Nuclear Facilities
|Publication Date:||1 January 2005|
OVERVIEW OF THE SEISMIC DESIGN CRITERIA
This Standard provides criteria for seismic design of safety-related Structures, Systems, and Components (SSCs) in a broad spectrum of nuclear facilities. Notation, definitions, guidelines, and commentary material are included.
A graded approach is used in developing the seismic design criteria presented in this Standard. The intent is to control the design process such that the performance of the SSC related to safety and environmental protection is acceptable.
To implement the graded approach for seismic design, 20 Seismic Design Bases (SDBs) have been defined as specified in ANS 2.26 and as shown in Table 1-1. SDBs have a quantitative probabilistic Target Performance Goal, PF, defined for each Seismic Design Category (SDC)* and a qualitative goal defined for each Limit State (LS) or level of acceptable structural behavior. SDBs defined by SDC 1 and 2 are covered by the approach presented in the International Building Code (IBC). In the future, the IBC will use ASCE 7 for its seismic criteria. This Standard, ASCE/SEI 43-05, presents design and analysis requirements for SDBs defined by SDC 3,4, and 5 and all Limit States.
Target quantitative performance goals decrease in annual probability of exceeding acceptable behavior limits as the SDC increases from 1 to 5. Decreasing quantitative Target Performance Goals are achieved in this Standard by increasing seismic demand associated with the Design Basis Earthquake (DBE). The DBE is defined by Uniform Hazard Response Spectra (UHRS) determined at a specified annual probability of exceedance, HD, multiplied by a Design Factor (DF). The UHRS annual probability of exceedance and the Design Factor are defined for each SDC in Section 2.0 of this Standard.
An SSC, when subjected to the DBE, has the greatest level of structural damage at Limit State A and the least level of structural damage at Limit State D. At Limit State A, large deformation and significant structural damage are acceptable. At Limit State D, no damage and essentially elastic behavior are the goal. Limit States B and C are at intermediate levels of acceptable structural damage. The levels of acceptable structural damage defined for each Limit State are achieved in this Standard by applying the appropriate inelastic energy absorption factor, Fμ, or the deformation limits as specified in Sections 5.0 and 8.0. These design provisions include specified levels of inelastic energy absorption, structural damping, structural capacity, and material strength. These design provisions also specify that seismic analyses are to conform to ASCE 4 and provide requirements for ductile detailing.
An integral part of the seismic design criteria given in the Standard are Quality Assurance (QA) measures and independent peer review. QA measures and the involvement of peer review are expected to take place throughout the design process, beginning with establishment of the DBE and continuing through the seismic analysis and the design and detailing tasks associated with final seismic design. QA measures and peer review, as addressed in Section 9.0 of this Standard, shall follow a graded approach with increasing rigor ranging from IBC Seismic Use Group III requirements for SDC-3 to nuclear power plant requirements for SDC-5.
The overall Seismic Design Procedure for SDC 3, 4, and 5 SSCs is shown in Figure 1-1. Table 1-2 summarizes recommended earthquake design provisions for these SDCs. Specific provisions are described in detail in Sections 2.0 through 9.0 of this Standard.
Design procedures specified in this Standard conform closely to common practices. The intended users of this Standard are the civil, mechanical, and structural engineers conducting the design of nuclear facilities.
* In this Standard, the term "Seismic Design Category" has a different meaning than in the International Building Code and ASCE 7.