Tool
Preliminary Beam Sizing
Simply supported beam. Enter characteristic loads (Gk, Qk); the tool applies the ULS combination 1.35 Gk + 1.5 Qk (EN 1990, eq. 6.10), checks bending, shear and deflection to BS EN 1993-1-1, and includes a simplified lateral-torsional buckling check for open sections using Mcr for uniform moment with kz = kw = 1 and C1 = 1.0.
Preliminary assessment assumption: for open sections (UB, UC, PFC) the compression flange is treated conservatively as unrestrained over the full span unless changed above. The effective unrestrained length L_LT used in the check is shown in the results.
Section data source: Section properties compiled from SCI publication P363 (Blue Book), Eurocode edition, and BS EN 10210 for hot-finished hollow sections. Values are nominal and provided for preliminary sizing only.
Output
Enter inputs and press Calculate to see results.
Tool version 1.0 · Last reviewed March 2026
Method and assumptions
- · Simply supported beam; characteristic loads are combined at ULS as 1.35 Gk + 1.5 Qk (EN 1990, expression 6.10).
- · Bending resistance uses the plastic modulus, Mpl,Rd = Wpl,y fy / γM0, assuming Class 1 or 2 sections (class must be verified in detailed design).
- · Shear resistance Vpl,Rd = Av fy / (√3 γM0), with Av ≈ h·tw for open sections and Av = A h / (h + b) for RHS/SHS (EN 1993-1-1 cl. 6.2.6).
- · Lateral-torsional buckling for open sections uses Mcr for uniform moment with kz = kw = 1, C1 = 1.0, load at shear centre, and the EN 1993-1-1 rolled-section buckling curves.
- · Deflection is calculated from the unfactored (SLS) loads and compared with L divided by the selected limit.
- · γM0 = γM1 = 1.0; E = 210 000 N/mm², G = 81 000 N/mm².
- · Section property data: Section properties compiled from SCI publication P363 (Blue Book), Eurocode edition, and BS EN 10210 for hot-finished hollow sections. Values are nominal and provided for preliminary sizing only..
Worked example
- UB, span 6.0 m, Gk = 10 kN/m, Qk = 5 kN/m, S275, compression flange unrestrained, deflection limit L/360.
- ULS UDL = 1.35 × 10 + 1.5 × 5 = 21.0 kN/m, so MEd = 21.0 × 6.0² / 8 = 94.5 kNm and VEd = 63.0 kN.
- The tool checks each section in the family in turn and reports the first that satisfies bending, lateral-torsional buckling, shear and deflection.
Disclaimer
Indicative result only. The calculation depends on the assumptions and information entered and does not constitute structural design or professional advice. Do not use the result for construction, procurement, Building Regulations submissions or safety-critical decisions. All results must be independently verified by a suitably qualified structural engineer before being used for design, construction or regulatory purposes. Bebbington Engineering Studio Ltd accepts no responsibility for reliance placed on unverified results.