C-A1A1 Scope

The scope of this Specification is essentially the same as the 2016 Specification for Structural Steel Buildings (AISC, 2016) that it replaces.

The basic purpose of the provisions in this Specification is the determination of the nominal and available strengths of the members, connections, and other components of steel building structures.

This Specification provides two methods of design:

• (a) Load and resistance factor design (LRFD): The nominal strength is multiplied by a resistance factor, $\phi$, resulting in the design strength, which is then required to equal or exceed the required strength determined by structural analysis for the appropriate LRFD load combinations specified by the applicable building code.
• (b) Allowable strength design (ASD): The nominal strength is divided by a safety factor, Ω, resulting in the allowable strength, which is then required to equal or exceed the required strength determined by structural analysis for the appropriate ASD load combinations specified by the applicable building code.

This Specification gives provisions for determining the values of the nominal strengths according to the applicable limit states and lists the corresponding values of the resistance factor, $\phi$, and the safety factor, $\Omega$. Nominal strength is usually defined in terms of resistance to a load effect, such as axial force, bending moment, shear, or torque, but in some instances it is expressed in terms of a stress. The ASD safety factors are calibrated to give the same structural reliability and the same component

size as the LRFD method at a live-to-dead load ratio of 3. The term “available strength” is used throughout the Specification to denote design strength and allow- able strength, as applicable.

This Specification is applicable to both buildings and other structures. Many structures found in petrochemical plants, power plants, and other industrial applications are designed, fabricated, and erected in a manner similar to buildings. It is not intended that this Specification address steel structures with vertical and lateral force-resisting systems that are not similar to buildings, nor those constructed of shells or catenary cables.

The Specification may be used for the design of structural steel elements, as defined in the AISC Code of Standard Practice for Steel Buildings and Bridges (AISC, 2022a), hereafter referred to as the Code of Standard Practice, when used as components of nonbuilding structures or other structures. Engineering judgment must be applied to the Specification requirements when the structural steel elements are exposed to environmental or service conditions and loads not usually applicable to building structures.

The Code of Standard Practice defines the practices that are the commonly accepted standards of custom and usage for structural steel fabrication and erection. As such, the Code of Standard Practice is primarily intended to serve as a contractual document to be incorporated into the contract between the buyer and seller of fabricated structural steel. Some parts of the Code of Standard Practice, however, form the basis for some of the provisions in this Specification. Therefore, the Code of Standard Practice is referenced in selected locations in this Specification to maintain the ties between these documents, where appropriate.

The Specification disallows seismic design of buildings and other structures using the provisions of Appendix 1, Section 1.3. The R-factor specified in ASCE/SEI 7-22 (ASCE, 2022) used to determine the seismic loads is based on a nominal value of system overstrength and ductility that is inherent in steel structures designed by elastic analysis using this Specification. Therefore, it would be inappropriate to take advantage of the additional strength afforded by the inelastic design approach presented in Appendix 1, Section 1.3, while simultaneously using the code specified R-factor. In addition, the provisions for ductility in Appendix 1, Section 1.3.2, are not fully consistent with the intended levels for seismic design.

In the Specification, which is used in general commercial applications, the quality assurance (QA) and quality control (QC) terms primarily refer to fabrication and erection procedures, qualifications, documents, and inspection, and they distinguish between responsibilities of the representatives of the owner and the authority having jurisdiction and the responsibilities of the steel contractor. In the AISC Specification for Safety-Related Steel Structures for Nuclear Facilities (AISC, 2018b), QA refers to evaluation of all parts of the process that have an effect on the final product, including structural analysis and design, as well as fabrication and erection, and QC refers to inspection and testing performed during the steel fabrication and erection process. The elements of QA in the nuclear industry are based on the U.S. Code of Federal Regulations.