# Ringlock Shoring Calculator (Slab Soffit)

Slab soffit shoring: standards, ledgers both ways, vertical braces and head jacks, in pieces and tonnes.

- Page: https://jianzhujisuan.com/en/ringlock-shoring
- Category: Temporary Works (https://jianzhujisuan.com/en/c/temporary-works)
- Chinese version: https://jianzhujisuan.com/zh/ringlock-shoring.md
- Data checked: 2026-10-25

## Quick result

With the default inputs (Shoring footprint, length 24 m, Shoring footprint, width 18 m, Shoring height (floor to soffit) 6 m, Standard spacing, length way 1.2 m, Standard spacing, width way 1.2 m, Lift height 1.5 m, Design axial force per standard 15 kN): **Total ringlock weight 27.11 t**

## Inputs

| Parameter | Type | Default | Unit | Note |
|---|---|---|---|---|
| Shoring footprint, length | number | 24 | m | Plan dimension along the main beam direction |
| Shoring footprint, width | number | 18 | m | The other plan dimension |
| Shoring height (floor to soffit) | number | 6 | m | Clear height to the soffit, including jacks, bearers and formwork — not the standard length |
| Standard spacing, length way | number | 1.2 | m | 0.9, 1.2 or 1.5 for slabs; multiples of 0.3 m only |
| Standard spacing, width way | number | 1.2 | m | Same as above; a square grid uses least material |
| Lift height | number | 1.5 | m | 1.5 or 2.0 only; Table 6.2.2 is written for a 1.5 m standard lift |
| Design axial force per standard | number | 15 | kN | Take the maximum within one independent frame from the shoring design; a 150 mm slab at 1.2 m spacing is about 12-15 kN |
| 3.0 m standard | select | In stock | — |  |
| 2.5 m standard | select | In stock | — |  |
| 2.0 m standard | select | In stock | — |  |
| 1.5 m standard | select | In stock | — |  |
| 1.0 m standard | select | In stock | — |  |
| 0.5 m standard | select | In stock | — |  |

## Formula

- **Bays, length way**: nx = ceil(footprint length ÷ standard spacing)
- **Bays, width way**: ny = ceil(footprint width ÷ transom spacing)
- **Standards**: N = (nx + 1) x (ny + 1)
- **Standard make-up**: Complete knapsack over the ticked lengths only (six stock sizes, each switchable), with total standard length constrained to [height - 0.85, height - 0.15]; the remainder is taken by head and base jacks
- **Ledger levels**: n = ceil(actual standard length ÷ lift) + 1; the closing length needs a ledger, otherwise the head jack projection exceeds 650 mm
- **Longitudinal ledgers**: N = levels x (ny + 1) x nx, each of bay length
- **Transverse ledgers**: N = levels x (nx + 1) x ny, each of transom spacing
- **Brace class k**: From Table 6.2.2-1 by axial force N and height H: N up to 25 gives 3 bays up to 16 m, 2 to 24 m, 1 above; 25 to 40 kN gives 2 up to 8 m, 1 above; above 40 kN gives every bay above 24 m, 1 otherwise
- **Braces per lift, length way**: (ny + 1) x [floor(nx ÷ k) + 1]; for every bay (k=0) use (ny + 1) x nx
- **Braces per lift, width way**: (nx + 1) x [floor(ny ÷ k) + 1]; for every bay (k=0) use (nx + 1) x ny
- **Top lift above 16 m**: Above 16 m the top lift is braced in every bay, and the normal arrangement counts only (lifts - 1)
- **Head jacks**: N = number of standards; every standard takes one
- **Base jacks**: N = number of standards
- **Horizontal bracing**: Courses = floor(lifts ÷ 6) + 1; coupler tube, excluded from ringlock weight
- **Structural ties**: Above 8 m, courses = floor(lifts ÷ 6) + 1
- **Footprint area**: S = total length x total width (m x m = m²)
- **Frame volume**: V = total length x total width x total height = footprint area x total height (m x m x m = m³)
- **Weight**: W = sum of quantity x unit mass from Table A.0.1
- **High-risk test**: High-risk if height >= 5 m or total load >= 10 kN/m²; expert review if height >= 8 m or load >= 15 kN/m². Span and concentrated line load are not tested here and must be checked separately

## Worked example

24 x 18 m slab shoring at 6 m clear height, 1.2 x 1.2 m standards, 1.5 m lifts and 15 kN per standard: 20 x 15 bays and 336 standards, made up to 5.50 m from a 3000 and a 2500, with the remaining 0.50 m taken by 350 mm of head jack and no base projection; five ledger levels giving 1,600 longitudinal and 1,575 transverse ledgers; a three-bay brace class from the table giving 336 braces along the length and 378 across, 714 in all; 336 head jacks and 336 base jacks — about 27.1 t, or 62.8 kg per m² of footprint and 10.5 kg per m³ of frame. At 6 m the work is high-risk and needs a method statement.

## Questions

### Why does shoring need so many more braces than a facade scaffold?

Because the two rules are not the same rule. For a working scaffold, clause 6.3.5 item 3 of JGJ/T 231-2021 requires vertical braces continuous from base to top between adjacent standards on the outer face only — the other face is the building, so it needs none. For shoring, clause 6.2.2 refers to Table 6.2.2-1 and the braces run in both plan directions, so every row and every column of standards gets a braced plane, only at a wider spacing. On the same 24 x 18 m frame, the facade rule gives 20 columns x 16 lifts = 320 braces, while the shoring rule gives 16 x 7 plus 21 x 6 = 238 braced planes x 3 lifts = 714. That is 2.2 times as many, and single-bay spacing widens the gap further. This quantity is what makes the frame geometrically stable, so it is not something to eyeball.

### Where does the design axial force N in Table 6.2.2 come from if I have no calculation?

N is the maximum axial force in any standard within one independent frame, taken from the shoring design. Without one, estimate from tributary area: N is roughly tributary area times the design load on the slab. At 1.2 x 1.2 m spacing on a 150 mm slab, with formwork and construction load at normal values, the design load is about 8 to 10 kN/m², so N lands at 11 to 14 kN and the frame sits in the up-to-25 kN band. That is an estimate, not a calculation: standards under beams, beside pour strips and at lift openings carry far more than the average, and those are exactly where failures start. So classify at 25 kN first, then re-run with the real N once the design arrives — crossing either boundary at 25 or 40 kN moves the frame up a whole brace class.

### Is the horizontal bracing in clause 6.2.7 a ringlock component? Should it be in the tonnage?

No, and this tool excludes it from the tonnage. Clause 6.2.7 requires a horizontal brace course every four to six standard lifts and refers explicitly to the steel-tube bracing provisions of JGJ 130, the coupler scaffold code — that is ordinary tube and couplers, not a ringlock horizontal brace. So the tool reports the number of courses so you know how many levels to brace, and the tube and couplers have to be taken off separately on the full-scaffold page. This is easy to miss: a ringlock quotation contains no such item, and the shortfall surfaces on site when the frame is up. Above 8 m the ties to the existing structure under clause 6.2.6 are likewise tube and couplers.

### Is it 5 m or 8 m that triggers expert review?

Five metres makes it high-risk; eight metres makes it above-scale. Both need a specific method statement, and the 8 m case also needs expert review. Under MOHURD circular No. 31 of 2018, annex 1 item 2 lists height 5 m or above, span 10 m or above, total design load 10 kN/m² or above, or line load 15 kN/m or above as high-risk; annex 2 item 2 lists 8 m, 18 m, 15 kN/m² and 20 kN/m or above as above-scale. The four conditions are alternatives, so any one is enough. Note also that a frame taller than its own plan width, standing free with no ties to an existing structure, is high-risk regardless of height. Since standards and ledgers only come in fixed sizes, what you actually tune is the density of the layout, not the size of the members.

### Why can the lift only be 1.5 or 2.0 m when our method statement says 1.8 m?

Because vertical braces are fixed-length components made only in 1500 and 2000 mm rises — the whole B-XG series in Table A.0.1 is ×1500 or ×2000. At a 1.8 m lift there is no brace that fits, and the only fallback on site is coupler tube, which clause 6.1.4 rules out for vertical bracing on scaffolds and which clause 6.2.2 rules out for shoring by directing you to the dedicated brace table. A ringlock shoring statement quoting a 1.8 m lift is either written for a different system, such as cuplock or coupler scaffold, or copied from another project. To genuinely use 1.8 m you would have to drop the ringlock braces and brace with coupler tube, at which point it is no longer a ringlock scheme. That is why this tool refuses the input rather than producing a list of B-XG-1800 that nobody can supply.

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