Bamboo Culm Sizer

Tool Scope

Bamboo Culm Sizer is a member-level structural design tool for bamboo culms. Checks bending, shear, axial, and combined loading to ISO 22156 (2021) and the IStructE Manual (2025), and assesses durability by assigning a Use Class and evaluating proposed measures against the intended design life. Results must be reviewed by a qualified structural engineer.

Feedback & Bugs

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Design actions

Bending Moment	$M$	kNm
Shear Force	$V$	kN
Compression	$P_{c}$	kN
Tension	$P_{t}$	kN

Material properties

Strength & Stiffness Data	-
Bending Strength	$f_{m, k}$	MPa
Compression Strength	$f_{c, 0, k}$	MPa
Tension Strength	$f_{t, 0, k}$	MPa
Shear Strength	$f_{v, k}$	MPa
Mean characteristic modulus	$E_{k, m e an}$	MPa

Note

IStructE Manual (2025) Table 4.4, scheme-design material properties are being used. For detailed design, confirm project-specific material properties from graded culms, supplier data, or test results.

Service conditions

Service Class	SC
Load Duration	-
Service Temperature	$T_{s}$	°C

Redundancy class

Redundancy Class

Longitudinal imperfections

Bow

b_{0}

mm/mm

Member boundary conditions

Member Length	$L$	m
Effective Length Factor	$K$
Axial Eccentricity	$e$	mm

Single culm, Ø 80 × 15.0 (mm)

Sizing parameters

Outer Diameter	$D$	mm
Wall Thickness	$t$	mm
Number of Culms	$n_{c u l m s}$

Note

Per ISO 22156 (2021), Clause 6.4.1, select design diameter and wall thickness from field measurements. If variation is 10% or less, use the average end measurements. If it exceeds 10%, use the minimum diameter along the culm and the minimum end wall thickness.

Max Utilisation

76.2%

Governing:Combined Compression + Bending

Combined Compression + Bending0.762

Combined Tension + Bending0.690

Bending0.451

Shear0.335

Compression (buckling)0.267

Tension0.239

Compression (crushing)0.072

Durability by Design

Bamboo durability depends not only on preservative treatment, but also on how each element is exposed, detailed, protected, maintained, and replaced.

This module assesses the durability strategy for a bamboo member over its intended design life. It assigns a Use Class based on the member's exposure to moisture, weathering, ground or water contact, and biological attack, then evaluates whether that challenge has been adequately addressed through treatment, moisture control, drainage, ventilation, weather protection, joint and end protection, corrosion-resistant components, and maintenance and replacement provisions. Conditions outside the permitted applications of ISO 22156 are flagged for redesign or review.

Reassess whenever the design life, treatment specification, detailing, maintenance strategy, or service environment changes.

Step 1/2

What is the severity of exposure of this member? Is that level of exposure permitted for the intended design life?

1a) Exclude unacceptable exposure

Marine or brackish water, including splash zone?	Required
In fresh water or aggressive in-ground conditions?	Required
In contact with soil, ground, or standing water?	Required
Bamboo cast into concrete?	Required

1b) Establish exposure condition / Use Class

Primary location	Required
Water traps, upward-facing openings or exposed culm ends?	Required
Bamboo-to-foundation / masonry / concrete interface	Required

Use Class verdict

Use Class unresolved

Confirm prohibited exposure answers before relying on the Use Class.

1c) Intended design life

Intended design life

Required

Design life verdict

NOT ESTABLISHED

Resolve the exposure classification, then check whether that Use Class is permitted for the intended design life.

Step 2/2

Are the proposed design decisions suitable for the established level of exposure, and the required design life?

2a) Control moisture and Service Class

Mechanical Service Class
Measured / specified moisture content	% Required
Only seasoned bamboo at local EMC used?	Required
Can the bamboo ventilate and dry after temporary wetting?	Required
Roof / cavity moisture management
HVAC negative-pressure water ingress risk

2b) Provide biological protection

Mature structural bamboo selected?	Required
Appropriate local harvesting practice followed?
Engineering judgement required Record the supplier's harvesting and quality-control basis where available. Reference: IStructE Manual Sec. 5.4 and Appendix A5.5.2-A5.5.3
Preservative system	Required
Wood-boring beetle risk
Engineering judgement required Ensure the preservative specification protects against local wood-boring beetles. Reference: ISO 22156 Annex B.1; Table 2
Subterranean termite risk
Engineering judgement required Ensure treatment and detailing address subterranean termites. Reference: ISO 22156 Annex B.1-B.2; Table 2
Termite path disrupted and inspectable?	Required

2c) Protect metallic connections

Metal fasteners / plates present?

Required

2d) Plan inspection and maintenance

Part of non-redundant load path?
Load-bearing bamboo accessible for inspection?	Required
Future replacement considered?	Required
Maintenance plan for leaks, drainage and finishes?	Required

Designer notes