Introduction: Load Calculation – Not as Mysterious as It Seems
The load capacity of steel grating may sound like a complex problem best left to structural engineers. Support spacing, bearing bar height, load types – a string of numbers and formulas can easily intimidate non‑professionals.
However, under Singapore’s Factories (Scaffolds) Regulations, the design load for working platforms is clearly defined as 670 kilogram‑force per square metre (approximately 6.57 kN/m²) – a non‑negotiable safety baseline. Whether you are a procurement officer, site supervisor, or project manager, you need a quick way to judge: can this steel grating actually support the required load?
Based on China’s ferrous metallurgy industry standard YB/T 4001.1-2019 “Steel Grating Bars and Matching Parts” and Singapore SS 363:2014 “Specification for steel gratings for roads, drains and walkways”, this article presents the simplest method – one formula, one table, a few examples – to help you quickly estimate the load capacity of steel grating.
Chapter 1: The Core Load Formula – A Secret Engineers Won't Tell You
1.1 The Core Formula
The load capacity of steel grating mainly depends on three variables: bearing bar height, support spacing, and steel strength. The most commonly used simplified formula in engineering is:
Allowable uniformly distributed load q = (σ × W) / (α × L²)
Where:
q: allowable uniformly distributed load (kN/m²) – the result you need
σ: allowable stress of steel (MPa) – for Q235B, typically 165 MPa
W: section modulus per metre width of steel grating (cm³/m) – available from product catalogues or the table below
L: support spacing (m) – the value you must measure or decide
α: bending moment coefficient – for simply supported conditions, generally 1/8 = 0.125
1.2 The Engineer's "Secret" – Quick Lookup Table for Section Modulus W
Section modulus W is the key to the calculation, but you don’t need to calculate it yourself. The table below gives the W values for common types:
| Steel Grating Type | Bar Size (mm) | Bar Spacing (mm) | Section Modulus W (cm³/m) | Self‑weight (kg/m²) |
|---|---|---|---|---|
| G253/30/100 | 25×3 | 30 | 6.2 | 18.5 |
| G255/30/100 | 25×5 | 30 | 10.4 | 25.0 |
| G323/30/100 | 32×3 | 30 | 14.5 | 22.1 |
| G325/30/100 | 32×5 | 30 | 17.5 | 29.3 |
| G405/40/150 | 40×5 | 40 | 24.0 | 29.8 |
| G505/40/150 | 50×5 | 40 | 37.5 | 37.2 |
| G605/60/150 | 60×6 | 40 | 52.0 | 48.6 |
Data source: YB/T 4001.1-2019 load tables and commonly used industry data.
1.3 Simplified Estimation Formula (For Quick Use by Non‑Engineers)
After simplification, the formula becomes a very practical “rule of thumb”:
Uniformly distributed load q (kN/m²) ≈ bar height (mm) × coefficient K / (support spacing²)
For the most common case (Q235B steel, 30mm bar spacing, simply supported), coefficient K ≈ 0.8.
Example:
Use G325 steel grating (bar height 32mm), support spacing 1.2m
q ≈ 32 × 0.8 / (1.2²) = 25.6 / 1.44 ≈ 17.8 kN/m²
This is far above the 6.57 kN/m² required by Singapore’s Factories Regulations, providing ample safety margin.
Warning: This simplified formula is for quick estimation only. Formal selection must rely on supplier load tables or structural engineer calculations.
Chapter 2: Quick Reference Table – Load Capacity at Different Support Spacings
2.1 Uniformly Distributed Load for Common Types at Different Spans (kN/m²)
The table below is based on Q235B steel, simply supported conditions, and a safety factor of 1.8. Data from YB/T 4001.1 load tables.
| Type | Bar (mm) | Support spacing L (metres) |
|——|———-|—–|—–|—–|—–|—–|
| | | 0.8 | 1.0 | 1.2 | 1.5 | 1.8 |
| G253/30/100 | 25×3 | 5.5 | 3.5 | 2.4 | 1.5 | 1.1 |
| G255/30/100 | 25×5 | 9.5 | 6.0 | 4.2 | 2.7 | 1.9 |
| G323/30/100 | 32×3 | 13.0 | 8.3 | 5.8 | 3.7 | 2.6 |
| G325/30/100 | 32×5 | 21.5 | 13.8 | 9.6 | 6.1 | 4.3 |
| G405/40/150 | 40×5 | 29.0 | 18.5 | 12.9 | 8.3 | 5.8 |
| G505/40/150 | 50×5 | 45.0 | 28.8 | 20.0 | 12.8 | 8.9 |
How to use:
Find the type you plan to use, then read horizontally to your support spacing.
The value is the uniformly distributed load capacity (kN/m²) at that span.
This value must be ≥ 6.57 kN/m² (670 kgf/m²) required by Singapore’s Factories Regulations.
2.2 Singapore Load Regulation Reference
Regulation 11 of Singapore’s Factories (Scaffolds) Regulations requires that planks sustain a load of 670 kgf/m² having regard to support spacing.
Conversion: 670 kgf/m² = 6.57 kN/m²
Therefore, values in the table ≥6.57 kN/m² meet the minimum Singapore requirement.
Quick checks:
G325/30/100 at 1.2m span: 9.6 ≥ 6.57 ✅
G325/30/100 at 1.5m span: 6.1 < 6.57 ❌ (slightly below, not recommended)
G405/40/150 at 1.5m span: 8.3 ≥ 6.57 ✅
G505/40/150 at 1.8m span: 8.9 ≥ 6.57 ✅
Chapter 3: Estimating Concentrated Loads
3.1 Concentrated Load Formula
When there is a single point load on the platform (e.g., equipment leg, forklift wheel), use the concentrated load formula:
Allowable concentrated load P = (σ × W × 4) / L
Where L is support spacing (m), and other symbols are as above.
3.2 Concentrated Load for Common Types at Different Spans (kN)
| Type | Bar | Support spacing L (metres) |
|——|—–|—–|—–|—–|—–|—–|
| | | 0.8 | 1.0 | 1.2 | 1.5 | 1.8 |
| G325/30/100 | 32×5 | 14.0 | 11.2 | 9.3 | 7.5 | 6.2 |
| G405/40/150 | 40×5 | 19.2 | 15.4 | 12.8 | 10.2 | 8.5 |
| G505/40/150 | 50×5 | 30.0 | 24.0 | 20.0 | 16.0 | 13.3 |
Interpretation:
Concentrated load is a single‑point force, e.g., equipment leg or single forklift wheel.
Singapore’s Factories Regulations do not specify a minimum concentrated load, but typically ≥1.5 kN is required for single‑person maintenance.
All values above are far above 1.5 kN, satisfying normal requirements.
Chapter 4: Three Key Principles of Load Calculation
4.1 Principle 1: Shorter Support Spacing = Higher Load Capacity
As seen in the table: for the same G325/30/100, at 1.0m spacing the capacity is 13.8 kN/m², while at 1.5m spacing it drops to 6.1 kN/m² – a reduction of 56%. When designing, prioritise reducing support spacing rather than blindly increasing bar height.
4.2 Principle 2: Concentrated Load and Uniformly Distributed Load Cannot Be Directly Converted
Many people mistakenly think “1.5 kN concentrated load ≈ 3.0 kN/m² uniformly distributed load”. This is only an approximation for a specific span and is not universal. Under a concentrated load, local stresses can be much higher than under a uniformly distributed load. Correct practice: calculate both load cases separately and use the larger bending moment as the design basis.
4.3 Principle 3: Dynamic Loads Require an Amplification Factor
Singapore’s Workplace Safety and Health Act requires consideration of dynamic loads. For forklift aisles and vibrating equipment areas, the design load must be multiplied by an impact factor of 1.2‑1.5. For example, if a forklift wheel load is 20 kN, the design value should be 24‑30 kN.
Chapter 5: Q&A – Common Questions on Load Calculation
Q1: I only know the total weight of the forklift. How do I convert that to wheel load?
A: Wheel load = (forklift self‑weight + load, rear axle weight) / number of wheels. A simple estimate: single wheel load ≈ (total forklift weight × 0.7) / number of wheels (the rear axle carries about 70% of the weight). For more accurate data, consult the forklift nameplate or technical manual.
Q2: Is the 670 kgf/m² required by Singapore's Factories Regulations a uniformly distributed load or a concentrated load?
A: The requirement is for a uniformly distributed load. The regulation says “sustain a load of 670 kgf/m²”, clearly indicating load per square metre. Concentrated loads must be checked separately.
Q3: My platform design load is 5.0 kN/m². Which type should I choose?
A: Check the table at 1.2m support spacing:
G325/30/100 (9.6 kN/m²) ✅ ample safety margin
If support spacing is 1.5m, G405/40/150 (8.3 kN/m²) ✅ still meets requirement.
It is recommended to keep a 20% safety margin, so target value ≥6.0 kN/m².
Q4: How can I verify that a supplier's load data is reliable?
A: Three steps:
Check the standard: Confirm that the type designation complies with YB/T 4001.1-2019.
Request a report: Ask for third‑party load test reports covering at least three different spans.
Look for certification: Does the product have SS 363:2014 or EAC certification? Does it include a load calculation sheet?
Q5: What safety factor should I use with the simplified formula?
A: Working platform design in Singapore typically uses a safety factor of 1.8‑2.0. The tables in this article already incorporate a safety factor of 1.8. If you calculate yourself, we recommend:
Pedestrian platforms: 1.8
Equipment platforms / forklift aisles: 2.0
Dynamic load areas: multiply by impact factor 1.2‑1.5 first, then by 1.8.
Chapter 6: Quick Selection Table for Singapore Projects
| Project Type | Recommended Type | Support Spacing | UDL Capacity | Meets 670 kgf/m²? | Typical Scenario |
|---|---|---|---|---|---|
| Indoor pedestrian walkway | G255/30/100 | 1.2m | 4.2 kN/m² | ✅ Yes | Workshop aisle |
| Outdoor pedestrian walkway | G325/30/100S | 1.2m | 9.6 kN/m² | ✅ Yes | Open‑air footpath, slip‑resistant |
| Light maintenance platform | G325/30/100S | 1.2m | 9.6 kN/m² | ✅ Yes | Equipment access area |
| Heavy equipment platform | G405/40/150S | 1.5m | 8.3 kN/m² | ✅ Yes | Compressor, pump area |
| Forklift aisle (2‑tonne) | G505/40/150S | 1.2m | 20.0 kN/m² | ✅ Yes | Warehouse logistics |
| Drainage cover (B125) | G325/30/100S | span 1.0m | 13.8 kN/m² | ✅ Yes | Sidewalk drain |
| Drainage cover (D400) | G505/40/150S | span 0.8m | 45.0 kN/m² | ✅ Yes | Vehicular road drain |
Chapter 7: Conclusion and bangtu Company's Technical Commitment
Steel grating load calculation is essentially a three‑way trade‑off between bar height, support spacing, and load type. With the core formula and quick‑reference tables, you don’t need to be a structural engineer to make correct decisions during procurement and construction.
Remember three numbers:
Singapore regulatory baseline: 6.57 kN/m² (670 kgf/m²)
Common safety factor: 1.8
Load capacity of G325/30/100 at 1.2m span: 9.6 kN/m²
Golden rules for selection:
Decide the support spacing first, then look up the appropriate type in the table.
For dynamic load areas, use a factor of 1.2‑1.5.
If slip resistance is required, add “S” to the type (load capacity unchanged, safety improved).
For coastal environments, choose galvanized coating ≥100μm or 316L stainless steel.
About bangtu Company
Bangtu Company has specialized in the steel grating field for over two decades. Our products are widely used in industrial platforms, petrochemical facilities, marine engineering, and municipal infrastructure in Singapore and globally. We commit to:
All load data is traceable; each batch comes with a load calculation sheet conforming to YB/T 4001.1-2019.
Singapore‑specific products meet the Factories Regulations 670 kgf/m² requirement; third‑party load test reports are available.
Free selection calculation service: just tell us your support spacing and application scenario, and we recommend the optimal type.
All products are supplied with bilingual (Chinese/English) load calculation sheets to meet Singapore BCA certification and project acceptance requirements.
Serrated anti‑slip steel grating is standard with “S” type – same load capacity, better safety performance.
Whether you are an engineer, procurement officer, or project manager, if you have questions about load calculation or need an accurate calculation for your project, please feel free to contact us.
Tel/Whatsapp: +8613363180165
Email: james@bangtuwiremesh.com
Website: www.bangtusteelgrating.com | www.chinawiremesh.ru
Appendix: Referenced Standards and Literature
YB/T 4001.1-2019 “Steel Grating Bars and Matching Parts Part 1: Steel Grating Bars” , Ministry of Industry and Information Technology, Issued 27 August 2019, Implemented 1 January 2020.
[Link: https://std.samr.gov.cn/hb/search/stdHBDetailedCNF?id=957D1F57029A8C7BE05397BE0A0A3C89]
Reference: Load tables, section modulus formulas, support spacing provisionsSingapore Factories (Scaffolds) Regulations 2004 , Singapore Statutes Online, Published 14 January 2004.
[Link: https://sso.agc.gov.sg//SL-Supp/S19-2004/Published?DocDate=20040114&ProvIds=pr11-]
*Reference: Regulation 11 – working platform load requirement 670 kgf/m²*GB 50017-2017 “Standard for Design of Steel Structures” , Ministry of Housing and Urban‑Rural Development, China, 2017.
Reference: Allowable stress values for steel, safety factor provisionsSS 363:2014 “Specification for steel gratings for roads, drains and walkways” , Enterprise Singapore, Published 2014.
Reference: Load classes for steel gratings (B125, C250, D400, etc.)Singapore Workplace Safety and Health Act (WSHA) 2006 , Ministry of Manpower, Singapore.
Reference: Requirement to consider dynamic loads
