Spatial-volume calculation rules for full-framing steel-pipe falsework in municipal and bridge/culvert works: the formula, the datum surface, the beam-body deduction issue and a cross-standard comparison (Shenzhen SJG 181.2-2024, Hunan 2025 edition, railway TB/T 10823-2024, highway JTG/T 3832-2018, Beijing DB11/T 2382-2024)

Topic Positioning

Quantity calculation rules for the spatial volume of full-framing steel-pipe falsework (including assembled steel falsework) in municipal and bridge/culvert engineering: the formula and datum surface, the standard answer to the common question "is the beam volume deducted", and related measurements (rental fees, preloading), with a comparison of the Shenzhen, Hunan, railway, highway and Beijing bases and their differences.

Core Conclusions

1. Measurement basis: full-framing steel-pipe falsework and assembled steel falsework are calculated by spatial volume in cubic metres, with the formula "height x longitudinal distance x width"; the height is measured from the structure soffit (beam/slab soffit) to the supporting surface, taking the longitudinal average height:

• Shenzhen SJG 181.2-2024 "Municipal Engineering Consumption Standard, Volume 2 Bridge and Culvert Works" 8.2.2: the quantity of falsework for cast-in-place beams and slabs is calculated as height (the longitudinal average height from the structure soffit to the original ground) x longitudinal distance (the clear distance between bent caps) x width (bridge width + 1.5 m); for falsework over water, the height is measured from the top of the working platform.
• Hunan 2025 edition municipal engineering consumption standard: the bridge falsework volume is the average level from the structure soffit to the original ground (after ground hardening, the hardened ground; for over-water falsework, the top of the over-water falsework platform) x longitudinal distance x (bridge width + 2 m).
• Railway TB/T 10823-2024 "Railway Engineering Budget Quota, Volume 2 Bridge and Culvert Works", volume notes: full falsework spatial volume = average height from beam soffit to ground x [beam span (Lp) - 1.2 m] x (bridge deck width + 1.5 m).

2. Beam-body deduction: under all bases the height is capped at the structure soffit/beam soffit, and the beam body lies above the falsework space, so it is inherently excluded from the spatial volume; no standard contains any "deduct the beam volume" rule - there is no such basis as "measure up to the deck and then deduct the beam"; for variable-depth beams the longitudinal average height is taken. The only express deduction: falsework for cast-in-place bent caps is calculated as height (from the bent-cap soffit to the top of the pile cap) x length (bent-cap length + 0.9 m) x width (bent-cap width + 0.9 m), deducting the volume occupied by the columns.
3. Rental fees and associated measurement: the rental fee of full-framing steel-pipe falsework and assembled steel falsework is calculated in tonne-months as the weight per cubic metre of spatial volume multiplied by the rental time; where the design documents are silent and there is no approved construction method statement, the rental weight may be taken as 50 kg and 125 kg per cubic metre of spatial volume respectively (including couplers etc.). Cantilevered bracket falsework for anti-collision barriers is measured by the length of the barrier in metres. The lower part of steel-pipe falsework is measured in tonnes by the design-dimension mass of the columns (including horizontal and diagonal braces); the upper part is measured in square metres as length (the distance between the centre lines of the two steel pipes) x width (bridge width + 1.5 m); where there is no basis for the weight of the composite metal equipment rented for the upper part (Bailey beams, universal steel members etc.), 184 kg/m2 may be used. Erection and dismantling of temporary supports for steel box girders are measured in tonnes by the weight of the composite metal equipment; the sub-items cover erection/dismantling costs only, and usage fees are calculated separately as rental.
4. Preloading and cost boundaries: surcharge preloading of falsework is calculated separately - Shenzhen by the design volume of the beam carried by the falsework multiplied by a factor of 1.10, in cubic metres; railway by the design beam weight multiplied by a factor of 1.2. The falsework sub-items exclude soffit formwork and ground improvement; usage fees (rental) are calculated separately.
5. Other bases for comparison: in highway JTG/T 3832-2018, bridge falsework is measured by vertical area (bridge net span x height; for beam bridges, from the top of the pier/abutment caps to the ground, "ground" meaning the underside of the falsework sill beam); arch centering, timber falsework and simple falsework use an effective width of 8.5 m and steel falsework 12.0 m, converted proportionally where the actual width differs; cap beams and sill beams are included in the quota, while foundations below the sill beam are not. Beijing DB11/T 2382-2024 Table D.3.41 sets formwork-support-frame sub-items under bridge falsework: D3-7-1 (height within 6 m, m2), D3-7-2 (each additional 1 m, m2), D3-7-3 (height within 6 m, m3, i.e. the spatial-volume basis).

Applicable Boundaries

• Precondition: quantities of bridge full falsework are calculated under a local/industry consumption standard (quota); whichever standard applies governs its width value (bridge width + 1.5 m or +2 m) and longitudinal-distance deduction (clear distance between bent caps, or span - 1.2 m); parameters must not be mixed across standards.
• "No deduction of the beam" applies to full falsework under beams and slabs; falsework for cast-in-place bent caps must deduct the volume occupied by the columns; over-water falsework is measured from the top of the working platform, and the part below the platform is not counted in the falsework volume.
• The falsework spatial volume and the surcharge-preloading quantity are two separate quantities: preloading is calculated separately by the design volume of the beam (Shenzhen x 1.10) or the design beam weight (railway x 1.2); usage fees, soffit formwork and ground improvement are generally not included in the erection/dismantling sub-items.
• The highway basis of "vertical area" (m2) and the municipal basis of "spatial volume" (m3) are different measurement bases and must not be mixed.
• Local standards such as Shenzhen's, Hunan's and Beijing's apply within their own administrative regions; actual works are governed by the locally current edition, the design documents and the approved construction method statement.

Further Reading

• SJG 181.2-2024 "Municipal Engineering Consumption Standard, Volume 2 Bridge and Culvert Works", Chapter 8 Measures Items, 8.2.2 bridge falsework (bent-cap falsework deducting columns, rental weight 50/125 kg/m3, upper part 184 kg/m2, preloading factor 1.10).
• "Hunan Province Municipal Engineering Consumption Standard" (2025 edition), bridge falsework chapter: arch-centering volume = segmental side area above the springing line x (bridge width + 2 m); the falsework volume formula, the 50 kg/m3 rental weight and the separate usage-fee provisions.
• TB/T 10823-2024 "Railway Engineering Budget Quota, Volume 2 Bridge and Culvert Works", volume notes, item XIV "Quantity calculation rules" (full-falsework formula, preloading x 1.2, steel-structure erection/dismantling by weight).
• JTG/T 3832-2018 "Highway Engineering Budget Quota (Volume II)", bridge falsework chapter (vertical-area method, effective-width 8.5 m/12.0 m conversion, cap and sill beams included, foundations below the sill beam excluded).
• DB11/T 2382-2024 "Construction Consumption Standard", Appendix D, Table D.3.41 bridge falsework (sub-items D3-7-1/D3-7-2/D3-7-3).