ASTM F1554 GRADE 55 STRUCTURAL ANCHOR RODS — TECHNICAL DATASHEET
ASTM F1554 Grade 55 is a high-strength structural anchor rod specification designed for critical foundation anchorage in infrastructure, highway signage, and heavy machinery. It serves as a mechanical bridge between lower-strength mild steel (Grade 36) and high-strength alloy steels (Grade 105), offering a balance of yield strength (55 ksi), ductile performance, and weldability.
Grade 55 rods are manufactured from high-strength, low-alloy or modified mild carbon steel. This grade is specifically preferred in seismic design and dynamic loading environments where high ductility and predictable yield behavior are required by ACI 318 standards.
■ Chemical Composition (wt%)
The chemistry is regulated to optimize strength and weldability. Phosphorus and sulfur are strictly minimized to eliminate hot shortness and grain boundary embrittlement.
| Element | Sizes ≤ 3/4" | Sizes > 3/4" to 1-1/2" | Sizes > 1-1/2" to 4" |
|---|---|---|---|
| Carbon (C) max | 0.25% | 0.25% | 0.25% |
| Manganese (Mn) | Optional | 0.60 – 0.90% | 0.60 – 0.90% |
| Phosphorus (P) max | 0.040% | 0.040% | 0.040% |
| Sulfur (S) max | 0.050% | 0.050% | 0.050% |
| Copper (Cu) min* | 0.20% | 0.20% | 0.20% |
■ Mechanical Properties
Grade 55 guarantees ductile behavior, ensuring the steel yields before concrete breakout occurs. Elongation and reduction of area are mandatory.
| Property | Specified Limit |
|---|---|
| Tensile Strength | 75 – 95 ksi (517 – 655 MPa) |
| Yield Strength (0.2% offset) | 55 ksi (380 MPa) min |
| Elongation in 2" (min) | 21% |
| Reduction of Area (min) | 30% |
| Hardness (Core) | ~80 – 101 HRB |
■ Structural Load Capacities (UNC)
Minimum load limits for standard structural anchor rod configurations.
| Nominal Dia. | Stress Area (in²) | Min Yield Load (lbs) | Min Tensile Load (lbs) |
|---|---|---|---|
| 1/2" | 0.1419 | 7,810 | 10,650 |
| 3/4" | 0.3340 | 18,370 | 25,050 |
| 1" | 0.6060 | 33,330 | 45,450 |
| 1-1/4" | 0.9690 | 53,295 | 72,675 |
| 1-1/2" | 1.4050 | 77,275 | 105,375 |
■ Fabrication and Tolerances
ASTM F1554 rods must adhere to strict geometric controls to ensure predictable structural behavior.
| Dimension | Tolerance |
|---|---|
| Length (≤ 24") | ± 1/2 inch |
| Length (> 24") | ± 1 inch |
| Thread Length | +1 inch / -0 inch |
| Bend Angle (Hook) | ± 5° |
■ Engineering FAQs
-
1. Is welding permitted on Grade 55?
Only if Supplementary Requirement S1 is specified. S1 mandates carbon equivalent limits (CE ≤ 0.45%) to prevent heat-affected zone (HAZ) embrittlement. Standard rods without S1 are not certified as weldable. -
2. Can Grade 55 be used as a substitute for Grade 36?
Yes, at the manufacturer's discretion, provided the supplied Grade 55 meets S1 weldability requirements. This is common when stocking pre-headed blanks. -
3. What torque values should be used?
ASTM F1554 does not provide torque values. Anchor bolts are tension/shear members, not friction-grip joints. Installation torque must be calculated by the Engineer of Record based on foundation design, lubrication, and rod geometry.
