Cable-tray support (bearing frame) quantity calculation: measured in kg, count by support/hanger spacing, unit mass by section-steel theoretical mass

Topic Positioning

The general method for cable-tray support (bearing frame) quantities: split supports from the tray into separate items, then "spacing -> count x theoretical mass -> kg quantity" in three steps, with a compilation of spacing and measurement calibers — for electrical installation/tray budgeting, BOQ preparation, and takeoff review.

Core Conclusions

1. Itemization and measurement (why kg, why separate)

• GB/T 50856-2024, 3.0.10: "Equipment, pipe, and accessory installation items include support, hanger, and foundation-channel fabrication, installation, and painting; where specially designed, itemize under Annex N or Annex M."
• Tray items exclude supports (caliber reference): SJG 111.3-2022 cable-laying notes — "tray installation includes assembling, welding, hole cutting, divider/cover installation, earthing, accessories, repairs; excludes support-frame fabrication/installation"; Beijing DB11/T 2382-2024 steel tray items (e.g., C4-11-248) include "accessories and support/hanger installation, earthing" but carry no section-steel main material — fabrication and material are separate (cf. C4-13-1/C4-13-2 per kg).
• By design finished mass in kg: SJG 181.7-2024 "cable-support metal members fabricated/installed by design finished mass in kg"; SJG 111.4-2022 "support fabrication/installation by single-member mass in kg; single-member means one arm or one post."
• Factory supports (incl. seismic) count per piece/set per design, not converted to mass.

2. Count: spacing (design-silent defaults) and algorithm

• GB 50397-2007, 16.2.1: horizontal tray supports 1.5-3m, vertical <= 2m, uniform within a zone (deviation <= 100mm); add posts approx. 300mm before/after horizontal bends and at mid-bends, at level changes, and before/after expansion joints; post verticality <= 2 per mille of length; posts fixed with expansion bolts to brick walls forbidden.
• GB 50606-2010, 4.3.2: straight-run spacing preferably 1.5-2.0m, uniform; supports within 0.5m of tray ends, branches, bends; with round-rod hangers, anti-sway supports at bends and every 30m on straights.
• GB/T 51239-2017, 9.3.7: horizontal 1.5-3m, vertical <= 2m; expansion joints for steel trays > 30m, aluminum/GRP > 15m, and at building expansion joints.
• DB11/T 1832.17-2021, 9.4.2: fixing points <= 1.5-3m generally, vertical <= 2m; support points within 500mm of box/panel entries, corners, bends, expansion-joint ends, and T-joint three-ends; expansion bolts for supports forbidden in vibration locations like underground garages.
• DB11/T 1832.19-2023, 3.4.4: horizontal 1.5-3m, vertical <= 2m; hanger rods >= 8mm; metal fixing supports every 20-30m for hanger runs > 30m.
• T/JSTJXH 12-2022 Annex C.3.2: horizontal 1.5-3.0m, vertical preferably <= 2m.
• Algorithm: per straight run n approx. length/spacing + 1 (points at both ends, rounded up), plus densified supports at bends, branches, entries, and expansion joints; design spacing governs where set.

3. Unit mass and total (core formulas)

• Unit mass = sum(member net length x unit theoretical mass)
• Unit theoretical mass (kg/m) = section area (mm2) x 0.00785 (steel 7.85 g/cm3, delivery by theoretical mass)
• Example (30m horizontal at 2m, points at both ends): supports = 30/2 + 1 = 16; unit = [10# channel post 1.2m x 10.007] + [L50x5 arm 0.8m x 3.77] + [L40x4 brace 0.5m x 2.422] = 16.235 kg; total approx. 259.77 kg (excluding densified points).
• Railway differs: TB/T 10829-2024 Vol. 8 Section 15 — cable-tray supports (I/channel/angle) per "piece" by height bands (<= 800/1500/2500mm) in DY-433~DY-441; seismic supports per "piece" (DY-442). Convert units and calibers when borrowing across systems.

Applicable Boundaries

• Design spacing governs; standards differ (GB 50606-2010's 1.5-2.0m is stricter; most others 1.5-3m) — follow the project's system/region, no cross-system mixing.
• The kg caliber applies to site-fabricated section-steel supports; factory and seismic supports per piece/set; railway prices per "piece" — not convertible to kg items of other systems.
• The example is a framework: actual takeoff per support standard details, member by member, excluding densified points — omissions understate quantities.
• Complete itemization: tray per m, supports per kg — avoid double counting or omitting fabrication, painting, and anti-corrosion (special requirements under Annexes N/M).

Further Reading

• GB/T 50856-2024, 3.0.10 and Annexes N/M.
• GB 50397-2007, 16.2.1; GB 50606-2010, 4.3.2; GB/T 51239-2017, 9.3.7.
• DB11/T 1832.17-2021, 9.4.2; DB11/T 1832.19-2023, 3.4.4; T/JSTJXH 12-2022 Annex C.3.2.
• SJG 111.3-2022, 2.1.17; SJG 111.4-2022, 3.2.1; SJG 181.7-2024.
• DB11/T 2382-2024 Annex C: Table C.4.93-1 (C4-11-248), Table C.4.117-1 (C4-13-1/2).
• TB/T 10829-2024 Vol. 8 Chapter 2 Section 15 (DY-433~DY-442).
• Theoretical masses from rolled-section supply standards or material handbooks.