B12 · Advanced · 1–2 hours
BS 8110 — slender and biaxial column
Rectangular column: effective lengths (Tables 3.19–3.20), additional moments with K iteration (3.8.3), biaxial enhancement (3.8.4.5) and steel by strain compatibility.
Tool: Education preview · Lesson: In preparation · Example: Built awaiting check · Workbook: Not applicable · Assessment: Not started
Outstanding before release: Engineering checker to verify clause mapping against BS 8110-1 and sign off v0.1.0. Cross-checked against TCC RCC53 Columns (see evidence).
Sources
| Role | Source | Note |
|---|---|---|
| Primary | BS 8110-1:1997 (+A1–A3): 3.8.1.3 (short/slender), 3.8.1.5–3.8.1.7 (effective length, limits), 3.8.2.4 (minimum eccentricity), 3.8.3.1–3.8.3.2, 3.8.3.7 (additional and design moments), 3.8.4.5 (biaxial), 3.12.5.3, 3.12.6.2 | Withdrawn standard — education and legacy checks only (mapping awaiting checker verification) |
| Supporting | Cross-check reference: The Concrete Centre RCC53 Columns (external tool; not used in the implementation) | Comparison evidence only (mapping awaiting checker verification) |
"Primary" marks the governing clause for this exercise; "contextual" marks related clauses; "supporting" marks the design-method or data source outside the CDC. A CDC chapter mapping does not mean the CDC contains the equation used.
Prerequisites: B05 BS 8110 — short column (N + M) · Topics: Reinforced concrete
Lesson
Lesson in preparation. No content is published until it has been written and reviewed.
Calculator
Purpose: Effective lengths, slenderness, additional moments and biaxial design moment; section designed by strain compatibility.
Model: Effective length le = β·lo (3.8.1.6 factors). Additional moment Madd = N·au, au = βa K h, βa = (le/b′)²/2000. Biaxial: Mx′ = Mx + β(h′/b′)My (or vice versa).
Units: N, mm, kN, kNm; stresses in N/mm² Ranges: fcu 25–50 N/mm²; fy 250 / 460 / 500; βb 0.7–1.0
Equations: K = (Nuz − N)/(Nuz − Nbal) ≤ 1; Nuz = 0.45fcu Ac + 0.87fy Asc; Nbal = 0.25fcu b d ; Braced: Mi = 0.4M1 + 0.6M2 ≥ 0.4M2; M = max(M2, Mi + Madd, M1 + Madd/2, N emin) ; Unbraced: M = M2 + Madd ; β for biaxial from N/(b h fcu): 0 → 1.00 … ≥ 0.6 → 0.30
Clauses: 3.8.1.3 (short/slender), 3.8.1.5–3.8.1.7 (effective length, limits), 3.8.2.4 (minimum eccentricity), 3.8.3.1–3.8.3.2, 3.8.3.7 (additional and design moments), 3.8.4.5 (biaxial), 3.12.5.3, 3.12.6.2
© 2026 QP Academy. Original calculation software implementing BS 8110-1:1997 (+A1, A2, A3). BS 8110 is WITHDRAWN (superseded by BS EN 1992-1-1 and, in Singapore, SS EN 1992-1-1). For education and for checking legacy designs only — not for new design submissions.
Not covered: Circular sections; unsymmetric reinforcement; Columns exceeding the 3.8.1.7–3.8.1.8 height limits; Shear in columns
Version 0.1.0 Draft
EDUCATION PREVIEW — NOT YET INDEPENDENTLY CHECKED. Education preview: this calculator has not yet been independently checked by an engineer. Use for learning only — not for engineering use. Outputs are stamped and must not be used for engineering work.
Excel workbook
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Exercises
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