EN 14399-3 HR Hot-Dip Galvanizing Class 10.9 Hexagon Head Bolt for Preloaded Joints

CE-marked HR bolting assemblies per EN 14399-3 (System HR) for preloaded joints in steel structures to Eurocode 3 (EN 1993-1-8). Each assembly comprises: property class 10.9 hexagon head bolt (large widths across flats), property class 10 hexagon nut, and through-hardened washer to EN 14399-6. Sizes M12–M36. Preload achieved by bolt elongation, providing controlled ductility and tolerance to moderate overtightening.

Bolts threaded before galvanizing to tolerance class 6az (ISO 965-5), accommodating zinc coating of 40–80 μm. After galvanizing, external thread mates with internal thread 6H. Nuts (class 10) have 6H or 6AZ internal threads; proof load stress 1160 MPa.

Bolt: class 10.9 per EN ISO 898-1 (tensile strength ≥1000 MPa, yield ≥900 MPa). Nut: class 10 per EN ISO 898-2, style 1 normal height (EN ISO 4032). Thread length per ISO 888 (longer than standard) ensures preload ≥0.7 × fub × As. Ductility via plastic elongation of shank; bolt fracture during tensioning is the intended failure mode, indicating overtightening.

Washers (only under nut) per EN 14399-6: Vickers hardness 300–370 HV, through-hardened to distribute preload and prevent embedment. Complete hot-dip galvanized assembly complies with EN ISO 10684 and EN 1090-2. All components traceable with batch-specific inspection certificate 3.1 per EN 10204.