1. High-Strength vs Ordinary Bolts

High-strength bolts clamp connected plates together through pretension and transfer load by friction or bearing, making them a primary method for field connections in steel structures. Ordinary bolts mainly carry shear and bearing without relying on pretension. Besides size, the property class and installation method matter most.

2. What 8.8 and 10.9 Mean

The property class is shown as tensile strength/yield ratio: 8.8 means a nominal tensile strength of 800 MPa with a yield ratio of 0.8, and 10.9 means 1000 MPa with a ratio of 0.9. Grade 10.9 heavy hex or tension control bolts are common for structural field connections, while 8.8 is used for general connections. Higher grades give more capacity and pretension but cost more, so follow the structural design.

3. Heavy Hex vs Tension Control (TC)

Heavy hex high-strength bolts are installed by the torque or turn-of-nut method with a torque wrench; tension control (TC) bolts control pretension by snapping off the splined tail, making field quality easier to verify. Both can be supplied to GB/T or ASTM systems; the choice depends on the drawings and site practice.

4. ASTM A325 / A490 / F3125 Compared

Overseas projects commonly use the ASTM system: A325 corresponds roughly to grade 8.8 high-strength bolts, A490 is stronger and roughly matches grade 10.9, and F3125 consolidates A325/A490 and related specifications. When asking for quotes, state the standard, grade and finish so the supplier matches nuts and inspection documents correctly.

5. What to Prepare When Enquiring

  • Size and quantity: diameter x length, and sets including nuts and washers;
  • Property class: 8.8 / 10.9 or a specified standard (GB/T 1228-1231, GB/T 3632, ASTM A325/A490/F3125, etc.);
  • Surface finish: blackened, hot-dip galvanized, etc.;
  • Accessories: whether washers, shear studs, stud bolts and so on are needed;
  • Inspection: material certificates, third-party inspection, etc.

To see what we supply, see our high-strength bolts and shear studs page and embedded parts and anchor bolts page; for coordinated members, see our steel fabrication service. Send us your list for a supply assessment and quotation.