ASTM A992 — The Standard W-Shape Grade

Yield strength: Fy = 50 ksi (all shapes, all flange thicknesses) Tensile strength: Fu = 65 ksi Maximum Fy/Fu ratio: 0.85

ASTM A992 was introduced in 1998 and has been the standard specification for wide-flange (W) shapes in US building construction since 2001, replacing A572 Gr. 50 for this application. The specification mandates a maximum yield-to-tensile ratio of 0.85, which ensures adequate inelastic deformation capacity for seismic and wind applications. All US domestic W-shapes are dual-certified to A992 and A572 Gr. 50.

Key advantages of A992 over its predecessors include lower carbon equivalent (improved weldability without preheat for standard procedures), tighter controls on yield strength (reducing the probability of under-strength material reaching the jobsite), and mandatory Charpy V-notch toughness at 70 degrees F for Group 4 and 5 shapes (W14x426 and heavier).

For connection design, the 65 ksi tensile strength governs plate tear-out and block shear checks. The 50 ksi yield governs gross section yielding. This combination of controlled yield and adequate tensile strength makes A992 the optimal grade for the majority of US steel building frames.

ASTM A572 — High-Strength Low-Alloy Plate and Bar

Available grades: 42, 50, 55, 60, 65 (ksi yield)

A572 Gr. 50 is the default US steel grade for plates, angles, channels, and non-W-shapes. It is the plate counterpart to A992 for W-shapes, and the two are often used together in a single project. Critical connection plates (shear tabs, end plates, base plates, gusset plates) are typically specified as A572 Gr. 50.

For Group 4 and 5 heavy shapes (W14x426 and heavier), A572 Gr. 50 is specified instead of A992 because the Charpy V-notch requirement of A992 may not be achievable for all heavy sections from all mills. The project specification should be consulted for any supplemental toughness requirements.

ASTM A36 — Carbon Structural Steel

Yield strength: Fy = 36 ksi (up to 8 in. thickness; 32 ksi for t > 8 in.) Tensile strength: Fu = 58 ksi (up to 8 in.; 58 ksi for all thicknesses)

A36 is the original US structural steel grade, dating from ASTM standardisation in 1960. While superseded by A992 and A572 Gr. 50 for primary structural members, A36 remains in common use for:

1. Base plates and bearing plates — The lower yield strength of A36 (36 ksi vs 50 ksi) increases the required plate thickness by approximately 18% (sqrt(50/36) = 1.18), which can be acceptable for lightly loaded base plates where the plate thickness is governed by minimum practical thickness rather than bending capacity.
2. Embedded plates and anchor plates — Lower strength simplifies design checks and provides reserve capacity.
3. Miscellaneous steel — Stair stringers, handrail posts, lintels, and secondary framing.
4. Angles and channels — Many standard angle and channel sizes are available in A36 from stockholding service centres.
5. Legacy renovations — Extending or modifying existing A36-framed buildings may specify A36 for compatibility.

A36 is NOT acceptable for laminar-tearing-prone details (e.g., welded moment connections with through-thickness loading) unless supplementary ultrasonic testing (UT) is specified per ASTM A898.

ASTM A913 — High-Strength Quenched and Tempered Shapes

Available grades: 50, 60, 65, 70 (ksi yield)

ASTM A913 covers quenched and tempered (Q&T) structural shapes, produced by a thermo-mechanical controlled process (TMCP) that achieves high strength with lower carbon content than traditional alloying approaches. This results in excellent weldability (lower carbon equivalent) and superior toughness properties at the higher strength levels.

A913 Grade 65 is the standard specification for jumbo shapes (Group 4 and 5, W14x426 through W14x730) where A992 is not available. The 65 ksi yield provides a 30% strength increase over A992, reducing member weight and cost for heavily loaded columns in high-rise construction. The Q&T process also produces more uniform through-thickness properties, reducing the risk of laminar defects in thick flanges.

ASTM A514 — High-Yield Quenched and Tempered Plate

Yield strength: Fy = 100 ksi (t <= 2.5 in.), 90 ksi (2.5 < t <= 6 in.) Tensile strength: Fu = 110 ksi (t <= 2.5 in.), 100 ksi (t > 2.5 in.)

A514 (also known as T-1 steel, the trade name from US Steel) is a high-strength quenched and tempered alloy steel plate used where weight reduction justifies the premium cost (typically 3-4x A572 Gr. 50 plate cost). Typical applications include long-span bridge girders, heavy crane runway girders, mobile equipment booms, and blast-resistant structural elements.

Due to the high strength and lower ductility compared to A572/A992, A514 requires careful detailing to avoid stress concentrations. Welding procedures must follow AWS D1.1 prequalified procedures specific to quenched and tempered steels, with controlled heat input to prevent softening of the heat-affected zone (HAZ). Pre-qualified filler metals are typically AWS E11018-M or equivalent.

ASTM A709 — Bridge Steel

Available grades: 36, 50, 50W, 50S, HPS 50W, HPS 70W, HPS 100W

A709 covers structural steel for bridges and is the governing specification for AASHTO LRFD bridge design. Grades 36 and 50 correspond to A36 and A572 Gr. 50, respectively, with the addition of mandatory Charpy V-notch toughness testing per AASHTO temperature zones. The "W" suffix denotes weathering steel (atmospheric corrosion-resistant, typically ASTM A588 composition), which develops a protective patina and can be used without paint in most environments. The "S" suffix denotes non-fracture-critical members. The HPS (High-Performance Steel) grades (50W, 70W, 100W) provide a combination of high strength, excellent weldability, and superior toughness developed through the AASHTO/FHWA HPS research program.

For building applications requiring enhanced toughness (enclosed parking structures, cold-service warehouses, Seismic Design Categories D/E/F), A709 Grade 50 is sometimes specified to obtain guaranteed Charpy values that are not required by A992.

Grade Selection Decision Matrix

Frequently Asked Questions

Why is A992 the standard for W-shapes instead of A572 Gr. 50?

ASTM A992 was specifically developed to address the yield-to-tensile ratio and toughness requirements for seismic design after the 1994 Northridge earthquake. The maximum Fy/Fu ratio of 0.85 ensures plastic hinge rotation capacity in moment frames without premature fracture. A572 Gr. 50 does not enforce this limit. Additionally, A992 mandates CVN testing for heavy shapes, which A572 Gr. 50 does not. While all domestic W-shapes are dual-certified A992/A572, specifying A992 guarantees the enhanced properties.

When should I specify A913 instead of A992?

Use A913 when you need yield strength higher than 50 ksi in a rolled shape (Grades 60, 65, 70). The primary application is jumbo columns (W14x426 and heavier) where A992 is not available and A913 Grade 65 fills the gap. The Q&T process of A913 also produces more uniform material properties through the thickness of heavy flanges, reducing the risk of laminar defects. For standard W-shapes up to W14x398, A992 is sufficient and more economical.

Is A36 still relevant for modern steel construction?

A36 remains relevant for specific applications where its lower yield strength does not penalize the design or where availability and simplicity outweigh the strength advantage of A572 Gr. 50. Base plates, miscellaneous steel, angles, and channels are often most economical in A36 from service centre stock. However, for primary structural members (beams, columns, braces), A992 and A572 Gr. 50 are the default choices. Specifying A36 for a W-shape beam today would increase the required section weight by approximately 39% compared to A992, making it uneconomical.

What steel grade should I specify for column base plates?

Base plates are typically A36 or A572 Gr. 50. The choice depends on whether the plate thickness is governed by the bending capacity (which scales approximately with sqrt(Fy)) or by minimum practical thickness (typically 3/4 in. for lightly loaded columns). For a base plate governed by bending: a 1.5 in. A572 Gr. 50 plate has equivalent bending strength to a 1.77 in. A36 plate (threshold = 1.5 x sqrt(50/36) = 1.77 in.). If the A36 thickness would be <= 2 in., A36 is often preferred for economy. If the required A36 thickness exceeds 2 in., switching to A572 Gr. 50 and reducing the thickness becomes economical and practical.

Educational reference only. All design values are per AISC 360-22, ASTM A6/A6M, and the AISC Steel Construction Manual 16th Edition. Verify steel grade availability with local service centres before specifying uncommon grades. Designs must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE). Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent professional verification.