Fastener & Anchor Bolt Specifications — The Smallest Parts Carry the Biggest Loads
A steel structure is only as connected as its bolts and anchors. The base plate sits on anchor bolts; the columns splice on high-strength bolts; portal frames, trusses and crane runways all transfer their forces through fasteners whose failure is instant and total. We specify, procure and quality-check every bolt to the reference standard — GB/T 1228 for domestic projects, EN 1090-2 and the ISO fastening standards for export — so the connection performs exactly as the calculation assumed, with the torque values and inspection records to prove it.
Choosing the Right Fastener for the Connection
High-strength friction-grip (HSFG) bolts are the backbone of primary structural connections — beam-to-column, column splices and truss joints. Designed as slip-critical at ultimate load, they transfer force by the friction between the faying surfaces under clamping pressure, not by the bolt shank bearing. The design model requires controlled preload — achieved by torque tightening per GB/T 1231 or by turn-of-nut / Direct Tension Indicator methods per EN 1090-2 — and the faying surfaces are prepared (shot-blasted, or painted to a friction-coefficient class) to the design's slip factor.
Ordinary (bearing-type) bolts carry the connection by shank bearing and shear, and are used where loads are moderate or where the connection is not subject to reversal — cleat connections, purlin/z-purlins fastening, bracing-to-frame ties. Grade 8.8 is the common specification.
Anchor bolts are the structural interface between steel and concrete: they transfer the column base reactions — axial, shear and moment induced forces — into the foundation. They are not structural-grade bolts in the frame sense; they are threaded bars embedded in concrete, and their design covers pull-out (bond and cone), edge distance and the base-plate-to-anchor interaction. We supply them shop-fabricated with templates to guarantee the group geometry the base plate was detailed to.
Stainless fasteners (A4-80) are specified for exposed connections in coastal, marine and chemical environments — where the ISO 12944 corrosivity zone is C4-C5 or the client's specification demands it — avoiding the galvanic corrosion that a galvanized bolt can suffer in aggressive chloride atmospheres.
High-Strength Bolt — Standard Parameters
| Parameter | Typical Range | Standard / Note |
|---|---|---|
| Diameter range | M12 – M64 (M16-M36 common) | Metric coarse thread per ISO 68 / GB/T 193 |
| Bolt grade | 8.8 / 10.9 high-strength | fub: 800 / 1000 MPa; yield 640 / 900 MPa |
| Nut & washer | Same grade as bolt; hardened flat washer pair | Washer under nut & head; oversize holes need hardened plate washer |
| Preload method | Torque control (domestic) / Turn-of-nut or DTI (EN 1090-2) | Calibrated wrench verification, torque chart per size |
| Slip factor design | Class A (0.30) unfettled to Class B/C (0.48-0.52) | Faying surface preparation per GB 50017 / EN 1993-1-8 |
| Hole preparation | Drilled or sub-punched & reamed; no hot punching | Fatigue-sensitive steel reamed to Class B clearance |
| Lot testing | Hardness, wedge tensile, load proof per lot | Mill certs with heat numbers on every delivery |
| Corrosion protection | Blue/grey zinc (domestic), HDG, or A4 stainless (coastal) | Galvanized bolts: thread tension check after coating |
Design per GB 50017 Chapter 11 (bolted connections) or EN 1993-1-8 Chapter 3; execution per EN 1090-2 for export projects including the preload verification record.
Anchor Bolt — Standard Parameters
| Parameter | Typical Range | Standard / Note |
|---|---|---|
| Bar diameter | M16 – M64 (M20-M42 common) | Threaded length per base plate thickness + nut/hardware |
| Anchor material | Q235B, Q355B bar; 35CrMo where high strength governs | Yield design per GB 50010 concrete-interface rules |
| Embedment | 25d – 40d (design pull-out governs) | Bond + cone failure checks both run per project |
| Anchorage type | Straight (bonded), hooked, or plate-ended | Plate-end anchor for high-tension base plates |
| Group geometry | Supplied on shop template to ±2 mm group tolerance | Template jig shipped with the bolts where specified |
| Base plate fitting | Grouted annulus; leveling via shim pack or grout screed | Non-shrink grout class C40-C80 per EN 1504-3 |
| Corrosion protection | HDG exposed length; epoxy or passive coating embedded portion | Coastal spec: A4 stainless anchors inside C5 zones |
Anchor design reviews both the steel side (anchor tension to bolt grade) and the concrete side (pull-out cone and bond) — the two failure modes are checked independently, and the governing one is documented.
From Bolt Lot to Torqued Connection
- Lot traceability: every bolt delivery carries mill certificates with heat numbers; the connection drawing references the lot, so a site inspector can trace any installed bolt to its test records.
- Preload verification: torque wrenches are calibrated, and the tightening torque for each size and grade is issued with the shop drawing — the site records the torquing sequence for slip-critical groups.
- Faying surface control: slip-critical surfaces are prepared to the design's slip factor class and protected until assembly; coating touch-up of the faying zone is forbidden without the designer's acceptance.
- Anchor templates: base plate hole positions are set from the concrete free of cast-in movement via template jigs — the group geometry the steel expects is fixed before the concrete sees it.
- Export packaging: fasteners ship in marked, corrosion-protected kits per connection type, with a bolting schedule — the erector's torque table travels in the same crate as the bolts.
Specify Your Fastening — We Supply the Proof
Send us your connection drawings or the bolt/anchor schedule. We return the grade selection, torque values, lot testing records and packaging plan — with documents your inspector can accept first time.
Email: market@permanentsteelstructure.com | WhatsApp: +86 18621689980 | Phone: +86 516-83269982