A3Materials

A3.1 Material Specifications

Structural steel used in the seismic force-resisting system (SFRS) shall satisfy the requirements of Specification Section A3.1, except as modified in these Provisions. Unless a material is determined suitable by testing or other rational criteria to exceed the specified yield stresses described herein, the specified minimum yield stress of structural steel to be used for members in which inelastic behavior is expected shall not exceed 50 ksi (345 MPa) for systems defined in Chapters E, F, G, and H, with the following exceptions:

• (a) For systems defined in Sections E1 (Ordinary Moment Frames), F1 (Ordinary Concentrically Braced Frames), G1 (Composite Ordinary Moment Frames), H1 (Composite Ordinary Braced Frames), and H4 (Composite Ordinary Shear Walls), this limit shall not exceed 55 ksi (380 MPa), except for columns in the system defined by Section H1, for which the limit of 70 ksi (485 MPa) applies, and except as allowed in exception (b).
• (b) For columns in systems defined in Chapter F and Section E3 (Special Moment Frames), E4 (Special Truss Moment Frames), G3 (Composite Special Moment Frames), H2 (Composite Special Concentrically Braced Frames), and H3 (Composite Eccentrically Braced Frames), this limit shall not exceed 70 ksi (485 MPa).

The ASTM materials shown in Table A3.1 are permitted to be used in the SFRS described in Chapters E, F, G, and H.

The structural steel used for column base plates shall meet one of the ASTM specifications in Table A3.1 or ASTM A283/A283M Grade D. Other steels and nonsteel materials in buckling-restrained braced frames are permitted to be used subject to the requirements of Sections F4 and K3.

User Note: This section only covers material properties for structural steel used in the SFRS and included in the definition of structural steel given in Section 2.1 of the AISC Code of Standard Practice. Other steel, such as cables for permanent bracing, is not covered. Steel reinforcement used in components in composite SFRS is covered in Section A3.5.

A3.2 Expected Material Strength

When required in these Provisions, the required strength of an element (a member or a connection of a member) shall be determined from the expected yield stress, $R_{y} F_{y}$, of the member or an adjoining member, as applicable, where $F_{y}$ is the specified minimum yield stress of the steel to be used in the member and $R_{y}$ is the ratio of the expected yield stress to the specified minimum yield stress, $F_{y}$, of that material. For composite members or adjoining members, as applicable, whose nominal strength is a function of the specified concrete compressive strength, $f_{c}^{\prime}$, the expected strength of an element shall be determined from the expected concrete compressive strength, $R_{c} f_{c}^{\prime} . R_{c}$ is the factor to account for the expected strength of concrete. The value of $R_{c}$ shall be taken as 1.3 .

When required to determine the nominal strength, $R_{n}$, for limit states within the same member from which the required strength is determined, the expected yield stress, $R_{y} F_{y}$, and the expected tensile strength, $R_{t} F_{u}$, are permitted to be used in lieu of $F_{y}$ and $F_{u}$, respectively, where $F_{u}$ is the specified minimum tensile strength and $R_{t}$ is the ratio of the expected tensile strength to the specified minimum tensile strength, $F_{u}$, of that material. When $R_{n}$ is a function of $f_{c}^{\prime}, R_{c} f_{c}^{\prime}$ is permitted to be used in lieu of $f_{c}^{\prime}$.

User Note: In several instances, a member, or a connection limit state within that member, is required to be designed for forces corresponding to the expected strength of the member itself. Such cases include determination of the nominal strength, $R_{n}$, of the beam outside of the link in eccentrically braced frames, diagonal brace rupture limit states (block shear rupture and net section rupture in the diagonal brace in SCBF), etc. In such cases, it is permitted to use the expected material strength in the determination of available member strength. For connecting elements and for other members, specified material strength should be used.

The values of $R_{y}$ and $R_{t}$ for various steel and steel reinforcement materials are given in Table A3.2. Other values of $R_{y}$ and $R_{t}$ are permitted if the values are determined by testing of specimens, similar in size and source to the materials to be used, conducted in accordance with the testing requirements per the ASTM specifications for the specified grade of steel.

A3.3 Heavy Sections

For structural steel in the SFRS, in addition to the requirements of Specification Section A3.1d, hot rolled shapes with flange thickness equal to or greater than 1½ in. (38 mm) shall have a minimum Charpy V-notch (CVN) toughness of 20 ft-lbf (27 J) at 70°F (21°C), tested in the alternate core location as described in ASTM A6/A6M, Supplementary Requirement S30. Plates with thickness equal to or greater than 2 in. (50 mm) shall have a minimum Charpy V-notch toughness of 20 ft-lbf (27 J) at 70°F (21°C), measured at any location permitted by ASTM A673/A673M, Frequency P, where the plate is used for the following:

• (a) Members built up from plate
• (b) Connection plates where inelastic strain under seismic loading is expected
• (c) The steel core of buckling-restrained braces

A3.4 Consumables for Welding

A3.5 Concrete and Steel Reinforcement

Concrete and steel reinforcement used in composite components in composite intermediate or special SFRS of Sections G2, G3, G4, H2, H3, H5, H6, and H7 shall satisfy the requirements of ACI 318, Chapters 18 and 20. Concrete and steel reinforcement used in composite components in composite ordinary SFRS of Sections G1, H1, and H4 shall satisfy the requirements of ACI 318, Section 18.2.1.4, and Chapter 20.