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.
Calculations follow the stated design basis and the UK National Annex unless otherwise indicated.
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
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Tool version 1.0 · Last reviewed Not yet recorded — pending engineering validation
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.
Engineering basis & limitations — Preliminary Beam Sizingv1.0 · reviewed Not yet recorded — pending engineering validation
Design standard
- · BS EN 1990 — Basis of structural design.
- · BS EN 1993-1-1 — Design of steel structures: general rules.
National Annex
- · UK National Annex values are adopted for partial factors (γM0 = γM1 = 1.0).
Analysis and design method
- · Simply supported single span; no continuity, cantilever or moment connection is considered.
- · Bending resistance from the plastic modulus, Mc,Rd = Wpl,y · fy / γM0, assuming a Class 1 or 2 cross-section.
- · Shear resistance Vpl,Rd = Av · fy / (√3 · γM0), with Av taken conservatively as h · tw for rolled I sections and channels, and A · h / (h + b) for hollow sections.
- · Lateral-torsional buckling for open sections from the elastic critical moment Mcr for uniform moment with kz = kw = 1.0, C1 = 1.0, load applied at the shear centre, then the EN 1993-1-1 rolled-section buckling curves.
Load combination basis
- · ULS: 1.35 Gk + 1.5 Qk (BS EN 1990 expression 6.10).
- · SLS deflection assessed under the characteristic combination Gk + Qk.
Material assumptions
- · S275 or S355 hot-rolled steel; E = 210,000 N/mm², G = 81,000 N/mm².
- · Section properties from published UK section data (SCI P363 dimensions and properties).
Restraint assumptions
- · The compression flange is treated as unrestrained over the full span unless the user states otherwise.
- · Restraint at supports is assumed to prevent lateral displacement and twist.
Effective length assumptions
- · L_LT defaults to the full span. Where the user enters a shorter value it is applied directly with kz = kw = 1.0 — no destabilising load factor is applied.
Serviceability criteria
- · Elastic deflection compared with the user-selected limit of L/250, L/360 or L/500.
- · Pre-camber, creep, settlement of supports and deflection of supporting members are not considered.
Not checked by this tool
- · Cross-section classification — Class 3 and Class 4 behaviour is not verified.
- · Web bearing, web buckling and local effects at load or support positions.
- · Torsion, combined bending and torsion, and mono-symmetric channel effects.
- · Combined axial force and bending (beam-column interaction).
- · Connections, bearings, fixings and their detailing.
- · Fire resistance, corrosion protection and durability requirements.
- · Overall structural stability, robustness and disproportionate collapse.
- · Vibration, dynamic response and fatigue.
- · Temporary works, construction sequence and buildability.
Where this tool does not apply
- · Continuous, cantilevered, curved, tapered, castellated, cellular or plated members.
- · Members carrying significant axial load.
- · Sections outside the published UK section range implemented in the tool.
Preliminary / informational calculation — not a BES project-specific structural design. Within the checks and assumptions listed above, only the stated utilisations have been assessed; a satisfactory utilisation does not confirm overall structural adequacy.
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.