Bamboo Structural Design Toolkit

Based on IStructE Manual for ISO 22156:2021 · v2.2

A hands-on design tool for architects, designers and students working with structural bamboo. Navigate the modules on the left to access span tables, calculators, checklists and decision guides.

Modules

Span Tables

Floor & roof beam span lookup with load interpolation. Tables 4.1 & 4.2.

Column Capacity

Column load capacity lookup by diameter and effective length. Table 4.3.

Material Properties

Characteristic strengths vs C24 softwood and D50 hardwood. Table 4.4.

Compression

Ylinen column capacity with redundancy factors. ISO 22156 Cl. 9.3.

Flexure

Bending capacity and deflection checks for single and multi-culm beams.

Shear

Shear capacity check for bamboo in flexure. Eq. 6.13/6.14.

End Bearing

Bearing capacity for straight cuts and fish-mouth joints. Cl. 10.10.

Dowel Connections

Dowel bearing modes A, B, C per ISO 22156 Cl. 10.12.

Durability & Fire

Treatment, service class selection, and fire resistance. Chapter 5.

CBSW Shear Walls

Composite Bamboo Shear Wall panel design. Chapter 8.

⚠ Disclaimer

This tool is for preliminary design and educational purposes only. All values must be verified by a qualified structural engineer. The tool does not replace the IStructE Manual or ISO 22156:2021. National building codes take precedence.

Toolkit by Superuse with Anthropic Claude

Visual Atlas

Structural typologies, proportions & design process

Visual reference for architects and designers. Structural forms, human-scale proportions, and the step-by-step design workflow for bamboo structures.

Design Process

❧

Species & Supply

Ch. 2

⊘

Grading & Testing

Ch. 3

◈

Scheme Design

Ch. 4

⛨

Durability Strategy

Ch. 5

↕

Member Design

Ch. 6

●

Connection Design

Ch. 7

⊞

Lateral System

Ch. 8

♨

Fire & Verify

Ch. 4.6

Structural Typologies

Portal Frame

Simple post-and-beam with pitched roof. Most common typology. Statically determinate if pin-based.

Simple load path Easy to build Needs lateral bracing

Truss Structure

Triangulated system enabling longer spans. Bamboo excels in tension members (f_tk = 40 MPa). Connections critical.

Long spans possible Bamboo strong in tension Complex joints

Composite Bamboo Shear Wall

Bamboo studs + mortar render + mesh. Excellent lateral resistance. Tested for seismic (R=2.0) and cyclone zones.

Seismic resistant 60-min fire rating Norma Andina

Curved / Arch Structures

Bamboo's natural flexibility allows curved forms. Efficient in compression. Requires careful lateral restraint and foundation design for thrust.

Efficient form Architecturally expressive Thrust at base

Culm Anatomy & Proportions

Quick Reference Rules

Span ≤ 27 × D

Initial beam size estimate. 100mm culm → max ~2.7m span.

D/t < 12

Wall slenderness limit to prevent local buckling. Typical bamboo: D/t = 6–10.

b₀ ≤ L/100

Maximum initial bow (curvature). Straighter culms → higher compression capacity.

D_dowel ≤ D/8

Maximum dowel diameter relative to culm. Prevents splitting at connections.

Stitch ≤ 10D

Maximum spacing of stitch connectors in multi-culm members.

4+ culms → C_R = 1.1

Redundant members allow 10% capacity increase and enable culm replacement.

Span Tables

Manual Ch. 4, Tables 4.1 & 4.2 · ISO 22156 Cl. 8

Achievable spans for single-culm bamboo floor joists and roof beams/rafters. Simply-supported members with UDL. Service Class 2, long-term deflection limit L/150.

Floor Beams — Achievable Spans

Orange = likely governed by shear · Bold = governed by L/150 deflection limit · Plain = transition zone

D_mean (mm)	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00	2.25	2.50	2.75
	Total uniformly-distributed load (dead + live) in kN/m → span in mm

Roof Beams — Achievable Spans

Total vertical load = dead + wind (vertical component)

D_mean (mm)	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00	2.25	2.50	2.75

Quick Estimator

Member type

Mean culm diameter mm

Areal load kN/m²

Joist/rafter spacing mm

Rule of thumb — initial size estimate

Span ≤ 27 × D_mean

Manual §4.8.1

Column Capacity Tables

Manual Ch. 4, Table 4.3 · ISO 22156 Cl. 9

Maximum unfactored axial loads for single bamboo culm columns. Service Class 2, bow b₀ = L/100. Interpolation is NOT permitted.

1-culm
C_R = 0.9

2-culm
C_R = 0.9

3-culm (Δ)
C_R = 0.9

4-culm (■)
C_R = 1.1

6-culm
C_R = 1.1

D_b (mm)	1500	2000	2500	3000	3500	4000	4500	5000	5500	6000
	Effective length KL (mm) → max unfactored load (kN)

Column Sizing Tool

Total unfactored load kN

Column effective length KL mm

Number of culms in column

Material Properties for Scheme Design

Manual Ch. 4, Table 4.4 · Lower-bound characteristic values

Conservative lower-bound strengths for any dry, mature bamboo species free of visual defects. For scheme/initial design only — not for detailed design. Compared with C24 softwood and D50 hardwood per BS EN 338:2016.

Property	Unit	Bamboo	C24 Softwood	D50 Hardwood
Mean density	kg/m³	700	420	740
Compression, f_ck	MPa	35	21	30
Tension, f_tk	MPa	40	14.5	30
Modulus of rupture, f_mk	MPa	40	24	50
Shear, f_vk	MPa	3	4	4.5
Modulus of elasticity, E_k	GPa	10 / 15*	11	14

* Tropical bamboos with D/t ≥ 10: use E_k = 15 GPa. All other species: 10 GPa. E_k is mean value with 75% confidence.

Visual Comparison

Bamboo C24 Softwood D50 Hardwood

Key observations

Bamboo has notably low shear strength (3 MPa vs 4–4.5 for timber) — this governs many design scenarios and explains why short-span, heavily-loaded beams are inefficient. However, tension strength (40 MPa) significantly exceeds both timber classes, making bamboo excellent for tension members and truss ties.

Structural Design Principles

Manual Ch. 4 · ISO 22156 Cl. 5–6

Key principles and checklist for structural bamboo design.

Design philosophy checklist

Aim for simple, statically-determinate structures with clear load paths§4.1
Incorporate ductility into joints, not members — bamboo is brittle§4.1, Ch.7
Use redundant members (≥4 culms) where possible for C_R = 1.1ISO 22156 Cl. 5.4
Design for replacement — consider future culm replacementISO 22156 Cl. 5.9
Model bamboo as linear elastic, joints as true pins§4.3
Account for real eccentricities at connections in analysis§4.3
Consider second-order effects (P-Δ) — all culms have inherent bow§4.3
Define a clear lateral load-resisting system§4.1
Address durability from the outset — not as an afterthoughtCh. 5
Minimise building mass in seismic zones — avoid heavy roof materials§4.4

Seismic Design — R/q Factor Selection

Bamboo is brittle — most failure modes cannot provide energy dissipation. ISO 22156 upper-bound: R ≤ 2.5, q ≤ 2.5 (only with test data).

Structural system

R (ASCE 7): 1.5

q (Eurocode 8): 1.5

Ductility μ: 1.0–1.3

Design to remain elastic. Joints must have minimum ductility per ISO 22156 Cl. 10.6.

Wind Design Checklist

Continuous vertical load path from roof to foundations (tension ties)§4.5
Robust lateral load-resisting system defined (CBSW, bracing, or diaphragm)§4.5
Uplift check: roof connections resist net upward wind pressureTable 4.2
Caution: heavy roofs improve wind resistance but increase seismic demand§4.4–4.5

Compression Member Design

Manual Ch. 6.4 · ISO 22156 Cl. 9.3 · Ylinen Equation

Calculate allowable column capacity using the Ylinen approach. Accounts for crushing, buckling, initial bow and redundancy.

Compression — Input

Outer diameter D mm

Wall thickness t mm

Effective length KL mm

Initial bow b₀ fraction of L

f_c,k MPa ?

E_k,mean GPa

Number of culms

Factor of safety FS_m

Column Diagram

Elevation

Section stress

Buckling mode

Ylinen Column Capacity — Eq. 6.1

N_cr,k = (P_c,k + P_e,k) / 2c − √[ ((P_c,k + P_e,k) / 2c)² − P_c,k·P_e,k / c ]

P_c,k = f_c,k × ΣA | P_e,k = n·π²·E_k·I·C_bow / (KL)²

C_bow = 1 − b₀ / 0.02 | c = 0.8

Manual Eq. 6.1–6.5 · ISO 22156 Cl. 9.3

Flexural Member Design

Manual Ch. 6.7 · ISO 22156 Cl. 8.3

Bending capacity and deflection checks for single and multiple-culm beams. No composite action assumed.

Flexure — Input

Outer diameter D mm

Wall thickness t mm

Span L mm

Number of culms n

f_m,k MPa ?

E_k GPa

f_v,k (shear) MPa

FS_m

Beam Diagrams

Moment & shear diagrams

Stress distribution

Flexural capacity — Eq. 6.6

M_r = f_m × Σ S_i where S = π/32 × [D⁴ − (D−2t)⁴] / D

Shear modification: C_v = 0.50 + 0.05 × (a/D) ≤ 1.0 (a = L/2 for simple span + UDL)

Manual Eq. 6.6–6.8 · ISO 22156 Cl. 8.3

Shear Capacity

Manual Ch. 6.9 · ISO 22156 Cl. 8.3.2

Shear capacity of bamboo members based on fundamental cross-section mechanics.

Input parameters

Outer diameter D mm

Wall thickness t mm

f_v,k MPa

Number of culms n

FS_m (shear)

Shear Stress Distribution

Parabolic shear stress — max at neutral axis

Shear capacity — Eq. 6.14 (simplified)

V_r = f_v × 0.5 × Σ A = f_v × Σ π/8 × [D² − (D−2t)²]

Manual Eq. 6.14 · ISO 22156 Cl. 8.3.2 · Conservative approximation (A_v ≈ A/2)

Combined Axial & Flexural Loads

Manual Ch. 6.8 · ISO 22156 Cl. 9.5

Linear interaction check for members under combined compression/tension and bending.

Interaction equation — Eq. 6.10

N_d/N_r + B·M_d/M_r ≤ 1.0

B = 1 / (1 − N_d/N_cr,k) for compression
B = 1.0 for tension

Manual Eq. 6.10–6.12

Interaction Check

D mm

t mm

L mm

n culms

N_d axial kN

M_d moment kNm

Load type

f_c,k MPa

f_m,k MPa

E_k MPa

N_r: — kN

M_r: — kNm

B: —

Unity: —

End Bearing Capacity

Manual Ch. 7.3.1 · ISO 22156 Cl. 10.10

Bearing capacity for straight-cut and fish-mouth bamboo joints.

Straight cut

Fish-mouth

Dowel (through)

Input parameters

Outer diameter D mm

Wall thickness t mm

Joint type

f_c (allowable) MPa

Joint Detail

Elevation — force transfer

Section at bearing

End bearing — Eq. 7.1

P_b = C_EB × f_c × A

C_EB = 0.8 (straight cut) | C_EB = 0.4 (fish-mouth)

Manual Eq. 7.1 · ISO 22156 Cl. 10.10

Dowel Connection Capacity

Manual Ch. 7.4 · ISO 22156 Cl. 10.12

Bearing capacity of dowel-type connections. Capacity governed by the lesser of modes A, B, and C.

Input parameters

Culm diameter D mm

Wall thickness t mm

Dowel diameter D_dowel mm

Load angle θ to fibre axis

Loading type

Dowel spacing s mm

f_c (allowable) MPa

f_v (allowable shear) MPa

Connection Selection Guide

Manual Ch. 7 · ISO 22156 Cl. 10

Select appropriate bamboo joint types based on load transfer, fabrication complexity, and structural performance.

Joint Classification

End Bearing

Axial load via direct contact. Straight cut (C_EB=0.8) or fish-mouth (C_EB=0.4). Simple but compression-only.

Compression only Simple

Dowel-type

Bolts/screws through culm wall. Transfers shear, tension, compression. D_dowel ≤ D/8. Min. edge distance = 5D_dowel.

Versatile Splitting risk

Lashing / Strap

Non-penetrating binding. Good for stitch connections (≤10D spacing). Min. 1,500 N/m force transfer between culms.

No splitting Limited capacity

Mortar-filled

Cavity filled with cement mortar + dowel. Increases bearing area and splitting resistance. Required for many column bases.

High capacity Irreversible

Decision Logic

Primary load transfer

Reversibility needed?

Seismic zone?

Recommended: End bearing (straight cut)

For simple compression transfer at column bases. Ensure perpendicular cut and full contact.

Species Database & Grading

Manual Ch. 2–3 · ISO 19624 · Appendix A3.8

Properties of common structural species and visual grading workflow per ISO 19624.

Common Structural Species

Species	Region	D mm	t mm	f_c,k	f_m,k	f_v,k	E_k GPa	ρ kg/m³
Guadua angustifolia	S. America	100–130	10–18	28–42	35–55	3–5	12–17	600–800
P. edulis (Moso)	China, Japan	80–120	6–12	40–60	50–80	5–8	10–18	600–900
B. stenostachya	SE Asia	70–100	8–14	30–45	40–60	3–5	10–15	550–750
D. asper (Giant)	SE Asia	100–180	10–20	25–35	30–50	2–4	8–14	500–700
B. blumeana	Philippines	80–140	8–15	25–40	30–50	3–5	8–12	500–700
Scheme design (any)	—	—	—	35	40	3	10–15	700

Manual Table 4.4 & Appendix A3.8. Ranges are indicative — testing per ISO 19624 required for detailed design. Tropical bamboos with D/t ≥ 10: use E_k = 15 GPa.

Visual Grading Steps — ISO 19624

Initial evaluation — confirm species, maturity (3–6 yr), treatment. Reject immature, decayed, or untreated culms.
Geometric characterisation — measure D_b, D_t, t_b, L. Calculate taper, ovality, D/t. Confirm D/t < 12.
Bow measurement — max lateral deviation b₀. Reject if b₀ > L/100. Straighter culms preferred for compression.
Visual defects — splits (>3mm or >200mm), bore holes, fungal staining, node damage.
Target sizes — group by diameter class (75, 100, 125 mm) ± 10%. Define grade limits.
Mechanical testing — ISO 22157 tests for f_c, f_m, f_v, E. Minimum 30 specimens per grade.
Characteristic values — 5th percentile, 75% confidence. Parametric (lognormal) or non-parametric per ISO 12122-1.

Quick Reject Criteria

b₀ > L/100

Excessive bow — reject for compression.

D/t > 12

Local wall buckling risk.

Splits > 200mm

Compromises shear & connection capacity.

Bore holes

Active insect attack — reject.

Durability, Treatment & Fire

Manual Ch. 5, §4.6 · ISO 22156 Cl. 5.5–5.7 · Appendix A4.1

Design for a 50+ year service life through treatment, design detailing, and fire protection.

Service Class & Treatment Selector

Per BS EN 350: all bamboo = DC 5 (not durable) for fungi, DC S (susceptible) for beetles/termites/marine borers.

Exposure condition

Insect risk zone

Required treatment: Boron (BAE ≥ 0.2% w/w)

CDF: 0.56 (SC 2)

Modified Boucherie or soaking. Target BAE ≥ 0.2% w/w. Keep bamboo dry.

Durability Checklist

Chemical treatment applied (boron preferred)§5.3, A5.7
Protected from direct rain (overhangs, render, upstands)§5.4
Ground contact avoided — min 300mm upstand§5.4
Adequate ventilation, no moisture traps§5.4
Metal connectors: galvanised/stainless for 50-year life§5.1
Design for replacement — redundant membersISO 22156 Cl. 5.9

Fire Resistance

Bamboo ≈ softwood timber chemically. Pilot-flame combustion ~230°C; charring at ~280°C. Thin-walled hollow section = inner + outer surfaces both exposed → more vulnerable than solid timber.

Exposed bamboo

No certified FRR. ISO 22156 limits to 2 storeys.

≤ 15 min

CBSW panels

Mortar render protection. Tested 60-min FRR per ISO 834.

60 min FRR

Protected bamboo

Plasterboard/intumescent: 30–60 min depending on system.

System-dependent

Fire testing: ISO 834, ASTM E119, UL 263. FRR is system-specific. Ref. Manual §4.6, A4.1.

Composite Bamboo Shear Walls

Manual Ch. 8 · Norma Andina · ISO 22156 Cl. 11

CBSW panels: bamboo frame + structural mortar render for seismic and wind resistance.

Panel Requirements

Component	Requirement	Ref.
Panel height	≤ 2.8m, max 2 storeys	A8.1
Panel width	≥ 1.2m structural	A8.1
Stud spacing	≤ 600mm c/c	A8.1.4
Stud diameter	≥ 60mm, pref. ≥ 80mm	A8.1.4
Diagonal bracing	≥ 1 per face, both directions	A8.1.5
Mortar render	Both faces, ≥ 15mm, ≥ 5 MPa	A8.1.3
Reinforcement	Wire mesh or bamboo mat, both faces	A8.1.2
Head/sole plates	Continuous, bolted to studs	A8.1.6
Treatment	All bamboo treated before assembly	Ch. 5

Panel Estimator

Panel width m

Panel height m

Stud Ø mm

Stud spacing mm

Render thickness mm

Render f'_c MPa

Number of panels

Tested shear capacity kN/m

Aspect ratio H/W: 1.0

Studs per panel: —

R / q: 2.0 (Norma Andina)

Panel V_r: — kN

Total wall V_r: — kN

Render area (2 faces): — m²

Panel mass (render): — kg

Panel mass (total): — kg

Fire rating: —

V_r based on tested shear capacity × panel width. Actual capacity requires full-scale testing per Manual A8.2. Panel mass assumes ρ_render ≈ 2000 kg/m³, ρ_bamboo ≈ 700 kg/m³.

CBSW Checklist

All bamboo treated before assemblyCh. 5
Diagonal bracing both directionsA8.1.5
Render both faces ≥ 15mm ≥ 5 MPaA8.1.3
Continuous head & sole platesA8.1.6
Panels verified by full-scale testingA8.2
Maximum 2 storeysISO 22156