Hobson technical article
Changes to AS 4100 and AS/NZS 5131: What They Mean for Structural Bolting
A three-page Hobson technical article (2021, by Alexander Sharp) on the August 2020 revision of AS 4100 and amendment to AS/NZS 5131, the Australian standards for steel structure design, fabrication and erection. It explains what changed and what it means for structural bolting.
What this covers
- Context of the changes
- Related standards
- Revisions to AS 4100
- Amendments to AS/NZS 5131
- Implications for structural bolting
- Bolting categories table
Applies to Hex Bolts & Set Screws and TC Bolt (Tension Control).
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- AS 4100:2020 now references AS/NZS 5131 directly, so AS/NZS 5131 becomes mandatory for fabrication and erection, including bolt installation and tensioning.
- Construction categories CC1 (lowest risk, such as farm buildings, gates and handrails) to CC4 (extreme consequences of failure) now apply across steel design and fabrication, assessed from importance level, service category and fabrication category.
- EN 14399-3 8.8 HR assemblies are the alternative to AS/NZS 1252 assemblies; EN 14399-4 System HV assemblies are not to be used as alternatives. EN 14399-3 10.9 HR is the additional assembly type for 10.9.
- Bolting category 10.9/S (snug tight) must use AS/NZS 1252 (EN 14399) products. AS 1110 bolts are only for 4.6/S and 8.8/S and are not suitable for full tensioning.
- A new reduction factor krd = 0.83 applies to PC 10.9 bolts where the threads intercept the shear plane (1.0 otherwise and for 4.6 and 8.8), so 10.9 gives only a marginal gain over 8.8 in that case.
- Minimum tensile strength by bolting category: 4.6 400MPa, 8.8 830MPa, 10.9 1,040MPa (8.8 bolts under 16mm diameter 800MPa).
- Lot traceability is now the baseline for CC2, CC3 and CC4, with no specified requirement for CC1.
Who it helps: Structural engineers, steel fabricators and erectors specifying or installing high strength bolts.
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