Steel Fy & Fu Table — ASTM Yield and Tensile Strength Reference

Every steel connection and member design starts with two numbers: Fy (yield strength) and Fu (tensile strength). This page provides a comparison table of Fy and Fu values by ASTM grade, thickness ranges, and code references from AISC 360, EN 10025, and AS/NZS standards.

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Complete ASTM Steel Fy/Fu Table

The table below covers all structural steel grades commonly specified in US practice. Values are minimums per ASTM specification unless noted as a range. All data from AISC 360-22 Table 2.3 and ASTM standards.

Thickness-Dependent Fy Reductions

Several ASTM specifications reduce Fy for thicker plates where uniform through-thickness properties are harder to achieve:

Design implication: Specifying a 6-inch thick A588 plate and assuming Fy = 50 ksi overestimates capacity by 19%. Always verify Fy at the actual plate thickness.

AISC 360 Material Selection Table (Table 2.3)

AISC 360-22 Table 2.3 maps each structural shape type to its preferred ASTM grade. This is the primary reference for material selection in US building design:

EN 10025 Metric Fy/Fu Table (European Practice)

For projects using Eurocode 3 (EN 1993), EN 10025 specifies yield and tensile values in MPa. Values shown are for t ≤ 16 mm:

EN 10025 requires Fy/Fu ≤ 0.91 for all grades. S355 (Fy = 355 MPa) is the workhorse of European structural steel, comparable to A572 Grade 50 in US practice.

AS/NZS Fy/Fu Table (Australian Practice)

For AS 4100 design, AS/NZS 3678 and 3679 specify material properties:

How Fy and Fu Are Used in Design

Structural design uses separate limit states for each material property:

Yielding limit states (governed by Fy, phi = 0.90):

• Flexural strength: Mn = Fy × Zx (plastic moment)
• Compression: Pn = Fcr × Ag (Euler buckling + inelastic buckling)
• Tension yielding: Pn = Fy × Ag
• Shear yielding: Vn = 0.60 × Fy × Aw × Cv

Fracture limit states (governed by Fu, phi = 0.75):

• Net section rupture: Pn = Fu × Ae
• Bolt bearing: Rn = 2.4 × d × t × Fu (deformation limit)
• Block shear: combination of tension rupture + shear yielding/fracture
• Weld base metal: Rn = 0.60 × Fu × t (shear rupture of base metal)

The governing strength is always the lower of the applicable limit states for a given component.

Fy/Fu Ratio as a Ductility Indicator

Codes enforce maximum Fy/Fu ratios to ensure adequate ductility:

• A992: Fy/Fu ≤ 0.85 (required for seismic W-shapes)
• EN 10025: Fy/Fu ≤ 0.91
• AS/NZS 1163 C450L0: Fy/Fu = 0.90 (approaches limit)

When Fy/Fu exceeds 0.85, the steel has less capacity for plastic redistribution. This matters in seismic moment frames (AISC 341 Section A3.1b) and connections requiring ductile behavior.

Worked Example — Designing with A992 Steel

Problem: A W18x50 beam in A992 steel (Fy = 50 ksi, Fu = 65 ksi) must resist a factored moment Mu = 300 kip-ft. Check the beam for compact section flexure per AISC 360.

Step 1: Section properties Zx = 101 in³ (from AISC Manual Table 3-2)

Step 2: Nominal flexural strength Mn = Fy × Zx = 50 ksi × 101 in³ = 5,050 kip-in = 420.8 kip-ft

Step 3: Design flexural strength (LRFD) phi_b × Mn = 0.90 × 420.8 = 378.7 kip-ft

Step 4: Check 378.7 kip-ft ≥ 300 kip-ft — OK

The beam's flexural strength is governed by Fy (yielding limit state). If the same beam had a net-section tension connection, Fu would govern the net area rupture check.

Quick Fy/Fu Lookup by Application

Frequently Asked Questions

What is the difference between Fy and Fu in structural steel? Fy (yield strength) is the stress at which steel begins to deform permanently. Fu (tensile strength) is the maximum stress before fracture. Fy governs ductile limit states like flexure and compression; Fu governs brittle limit states like net section rupture and bolt bearing.

What is A36 steel Fy and Fu? A36 steel has a minimum Fy of 36 ksi (250 MPa) and Fu of 58–80 ksi (400–550 MPa). It was the standard structural steel for decades but has been largely replaced by A572 Grade 50 and A992 for modern W-shapes.

What is the strongest common structural steel grade? A514 (T-1) with Fy = 100 ksi and Fu = 110–130 ksi is the strongest commonly available structural plate grade. For W-shapes, A913 Grade 65 (Fy = 65 ksi, Fu = 80 ksi) is the highest strength standard section.

Can I substitute S355 for A572 Grade 50? S355 (fy = 355 MPa) is approximately equivalent to A572 Grade 50 (Fy = 345 MPa / 50 ksi), but they are not directly interchangeable. EN 10025 and ASTM have different toughness subgrades, thickness limits, and chemical composition requirements. Verify mill certificates and project specifications before substituting across codes.

What is the Fy/Fu requirement for A992 seismic steel? AISC 341 requires A992 steel used in seismic force-resisting systems to have Fy/Fu ≤ 0.85 and a maximum Fy of 65 ksi. This ensures adequate ductility for earthquake energy dissipation through plastic hinging.

Related Pages

• AISC Steel Grades Reference
• ASTM A36 Steel Properties
• Structural Steel Properties Database
• Beam Capacity Calculator
• Column Capacity Calculator
• Bolted Connections Calculator
• Welded Connections Calculator
• Steel Weight Calculator
• Base Plate & Anchors Calculator

Educational reference only. Verify material properties from mill certificates and governing standard for your jurisdiction.