AS/NZS 1554 is the Australian/New Zealand standard for welding structural steelwork. It's a multi-part standard. AS/NZS 1554.1 covers general structural welding (the part most relevant to gate fabrication). AS/NZS 1554.5 covers welding of structures subject to high-cycle loading. Other parts cover stainless, reinforcement, and weld certification.
Key concepts for gate work: 'SP' (structural purpose) and 'GP' (general purpose) weld categories. SP welds are inspected to higher standards and are required for primary structural members. GP welds are acceptable for secondary and decorative welds with less stringent inspection.
Most gate fabrication runs on GP welds because the loads are well within the capacity of standard fillet welds laid by experienced welders. SP becomes relevant for commercial projects with formal engineering certification.