----------------------------- | ---- | ------------------ | --------- | ------------------------ | | Fracture-critical members (tension) | 1 | 25 | 70°F | Non-critical temperature | | Fracture-critical members (tension) | 2 | 25 | 40°F | Moderate temperature | | Fracture-critical members (tension) | 3 | 25 | 10°F | Cold temperature | | Fracture-critical members (tension) | 4 | 25 | -10°F | Very cold | | Fracture-critical members (tension) | 5 | 25 | -30°F | Extreme cold |

Zone determined by lowest anticipated service temperature (LAST) per AISC Specification Appendix A.

ASTM A709 (Bridge Steel) CVN Requirements

Grade Zone 1 (70°F) Zone 2 (40°F) Zone 3 (10°F) Zone 4 (-10°F)
36 15 ft-lb 15 ft-lb at 40°F 15 ft-lb at 10°F 15 ft-lb at -10°F
50 15 ft-lb 15 ft-lb at 40°F 15 ft-lb at 10°F 15 ft-lb at -10°F
50W 15 ft-lb 15 ft-lb at 40°F 15 ft-lb at 10°F 15 ft-lb at -10°F
HPS 50W 25 ft-lb 25 ft-lb at 40°F 25 ft-lb at 10°F 25 ft-lb at -10°F
HPS 70W 25 ft-lb 25 ft-lb at 40°F 25 ft-lb at 10°F 25 ft-lb at -10°F

HPS = High Performance Steel. Higher toughness requirements than standard grades.

A1085 (HSS) CVN Requirements

Requirement Value
Test temperature -20°F (-29°C)
Minimum energy (full size) 25 ft-lb (34 J)
Subsize specimens Proportionally reduced
Frequency Per heat, per size

This is one of the key advantages of A1085 over A500, which has no CVN requirement.

Typical CVN Values by Steel Grade

At Room Temperature (70°F / 21°C)

Steel Grade Typical CVN (ft-lb) Range (ft-lb) Notes
A36 60-100 30-150 Very ductile, high toughness
A992 50-90 25-150 Good toughness standard
A572 Gr 50 50-90 25-140 Similar to A992
A572 Gr 65 35-70 15-100 Lower than Gr 50
A588 40-80 20-120 Good toughness for weathering
A514 20-50 10-80 Lower due to high strength
A913 Gr 50 80-150+ 50-200+ Excellent, SEISMIC grade
A500 Gr B 15-40 5-60 Variable, no spec minimum
A500 Gr C 15-40 5-60 Variable, no spec minimum
A1085 40-80 25 min guaranteed Minimum 25 ft-lb at -20°F

At Low Temperature (-20°F / -29°C)

Steel Grade Typical CVN (ft-lb) Range (ft-lb) Notes
A36 20-60 10-80 Moderate drop from RT
A992 20-50 10-70 Moderate drop
A572 Gr 50 20-50 10-70 Moderate drop
A572 Gr 65 10-30 5-50 Significant drop
A588 15-40 8-60 Moderate drop
A514 10-25 5-40 Low toughness at cold temps
A913 Gr 50 50-120+ 30-150+ Excellent cold-weather toughness

At Very Low Temperature (-40°F / -40°C)

Steel Grade Typical CVN (ft-lb) Ductile-Brittle Transition?
A36 10-40 Many heats show transition
A992 10-35 Transition zone for some heats
A572 Gr 50 10-35 Transition possible
A514 5-15 Likely brittle
A913 Gr 50 30-80+ Remains tough

Factors Affecting Toughness

Factor Effect on Toughness Design Implication
Temperature Decreases as temperature drops Specify CVN at service temperature
Loading rate Impact loading reduces toughness Fatigue and seismic checks consider this
Thickness Thicker material has lower toughness Constraint effect, triaxial stress state
Notch severity Sharper notches = lower toughness Detailing avoids notches and re-entrant corners
Grain size Finer grains = higher toughness Normalizing refines grain structure
Carbon content Higher carbon = lower toughness High-strength steels may have lower CVN
Rolling direction Lower across rolling direction CVN specimens oriented perpendicular to rolling

Temperature Transition Behavior

Structural steel exhibits a ductile-to-brittle transition temperature (DBTT). Above the DBTT, fracture is ductile (high energy, shear fracture appearance). Below the DBTT, fracture is brittle (low energy, cleavage fracture appearance).

Transition Indicator Value Description
Upper shelf energy 60-150 ft-lb Fully ductile fracture (shear)
Transition temperature -20°F to +40°F 50% shear fracture appearance
Lower shelf energy 5-15 ft-lb Fully brittle fracture (cleavage)

The transition temperature varies significantly by heat, thickness, and composition. Specification minimums ensure the steel is above its transition temperature at the specified test temperature.

Frequently Asked Questions

What is a good Charpy value for structural steel? For buildings, CVN values of 25+ ft-lb at the minimum service temperature are typical minimums. For bridges, 15-25 ft-lb depending on grade and zone. Values above 40 ft-lb indicate excellent toughness.

Does every steel project need Charpy testing? No. AISC requires CVN testing only for fracture-critical members (primary tension members whose failure would cause collapse). Most building members do not require testing. Bridge projects always require it.

What is the difference between A500 and A1085 HSS? A500 has no Charpy requirement and highly variable toughness (5-60 ft-lb). A1085 requires minimum 25 ft-lb at -20°F, making it suitable for fracture-critical and seismic applications.

How does thickness affect toughness? Thicker sections have more constraint (triaxial stress state) at the notch, which reduces the apparent toughness. AISC and ASTM have different CVN requirements for different thickness ranges to account for this.

Can I use A992 without CVN testing? Yes, for non-fracture-critical building members. A992 shapes are routinely used without CVN testing. If the member is fracture-critical (primary tension), testing is required per AISC Appendix A.

Try it now: Check your Charpy values with our free Steel Grade Selection calculator →

Related Pages

Disclaimer

This is a calculation tool, not a substitute for professional engineering certification. All results must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in construction, fabrication, or permit documents. The user is responsible for the accuracy of all inputs and the verification of all outputs. [object Object]

[object Object]

Frequently Asked Questions

What is the recommended design procedure for this structural element?

The standard design procedure follows: (1) establish design criteria including applicable code, material grade, and loading; (2) determine loads and applicable load combinations; (3) analyze the structure for internal forces; (4) check member strength for all applicable limit states; (5) verify serviceability requirements; and (6) detail connections. Computer analysis is recommended for complex structures, but hand calculations should be used for verification of critical elements.

How do different design codes compare for this calculation?

AISC 360 (US), EN 1993 (Eurocode), AS 4100 (Australia), and CSA S16 (Canada) follow similar limit states design philosophy but differ in specific resistance factors, slenderness limits, and partial safety factors. Generally, EN 1993 uses partial factors on both load and resistance sides (γM0 = 1.0, γM1 = 1.0, γM2 = 1.25), while AISC 360 uses a single resistance factor (φ). Engineers should verify which code is adopted in their jurisdiction.

Design Resources

Calculator tools