GB 50205-2020 Annex J steel structure measurement: design-quantity rules (J.0.2), quantity = design quantity x wastage adjustment factor (J.0.3), and two-decimal rounding

Topic Positioning

The direct basis for measuring steel structures: the design-quantity rules (J.0.2), quantity = design quantity x wastage adjustment factor (J.0.3), and rounding of GB 50205-2020 "Standard for acceptance of construction quality of steel structures" Annex J — for budget/settlement takeoff.

Core Conclusions

1. Design quantity rules (J.0.2, verbatim):

1. Sections, pipes, tendons etc. classified by spec/shape/size: design length x unit mass per product standard;
2. Plates (steel plate/strip, profiled sheet) by spec/thickness: design area (or volume) x unit mass per product standard;
3. Fasteners (bolts), studs: per design documents, count (sets) by spec/shape/size, or converted mass (count x unit mass);
4. High-strength bolt assemblies by spec sets: hex assemblies = 1 bolt + 1 nut + 2 washers; torshear = 1 bolt + 1 nut + 1 washer;
5. Weld design quantities: deposited metal per the design weld sizes;
6. Gusset plates: area per design dimensions; irregular/polygonal plates by circumscribed rectangle;
7. No deduction for bolt holes, bevels, segmental notches, or beam-column connection gaps; equipment-pipe openings < 0.1 m2 also not deducted.

2. Quantity and wastage (J.0.3, verbatim):

• Steel quantities = design quantity x wastage adjustment factor per Table J.0.3 (values by member/fabrication class — consult the table);
• Wastage for complex structures may be negotiated by the parties per actual conditions;
• Values to two decimals; round by standard rounding.

3. Practice points: section design quantity = length x product-standard unit mass, consistent with delivery by theoretical mass — at 7.85 g/cm3 density (JG/T 581-2023, 5.3.1); budget/settlement takeoff multiplies the design quantity by the wastage factor — not by field cutting sizes.

Applicable Boundaries

• Applies to measurement of steel structures accepted under GB 50205-2020; design quantities from design documents/dimensions, not site measurement.
• Table J.0.3 factors by member class are not listed here — consult the standard table; negotiated factors for complex structures should be recorded in writing.
• Bolt holes, bevels, notches, and beam-column gaps never deducted; pipe openings judged by the 0.1 m2 threshold (below it, also not deducted).
• Contracts govern where they stipulate otherwise.

Further Reading

• GB 50205-2020 Annex J, J.0.2, J.0.3 and Table J.0.3.
• Unit-mass (theoretical mass) quick calculation and density: JG/T 581-2023, 5.3.1; GB/T 706; GB/T 11263 spec tables.