ISO 22156:2021

Bamboo structures - Bamboo culms - Structural design

This document applies to the design of bamboo structures whose primary load bearing structure is made of round bamboo or shear panel systems in which the framing members are made from round bamboo. Except as indicated in Clause 12, this document applies to one- and two-storey residential, small commercial or institutional and light industrial buildings not exceeding 7 m in height. This document is concerned only with requirements for mechanical resistance, serviceability and durability of bamboo structures. This document permits an allowable load-bearing capacity design (ACD) and/or allowable stress design (ASD) approach for the design of bamboo structures. Allowable load-bearing capacity and allowable stress approaches may be used in combination in the same structure. This document additionally recognises design approaches based on partial safety factor design (PSFD) and/or load and resistance factor design (LRFD) methods (5.11.1), previous established experience (5.11.2), or documented ‘design by testing’ approaches (5.11.3). Other requirements, such as those concerning thermal or sound insulation, are not considered. Bamboo structures may require consideration of additional requirements beyond the scope of this document. Execution is covered to the extent that it impacts the quality of construction materials and products required to comply with the design requirements contained herein. This document provides a number of modification factors, designated Ci. These are empirically derived factors, based on best available engineering judgement, that are believed to be universally applicable to bamboo materials that are appropriate for building construction. Parameters affecting bamboo material performance are many and are addressed explicitly through the use of experimentally determined characteristic values of strength and stiffness. Annex A provides a summary of the bases upon which the provisions of this document were developed. This document does not apply to - structures made of engineered bamboo products such as glue-laminated bamboo, cross-laminated bamboo, oriented strand, or densified bamboo materials, - bamboo-reinforced materials where bamboo is not the primary load-bearing constituent. This includes bamboo-reinforced concrete, masonry and soil, or, - scaffold structures constructed with bamboo.

Structures en bambou — Tiges de bambou — Conception des structures

General Information

• Status: Published
• Publication Date: 02-Jun-2021
• ICS: 91.080.20 - Timber structures
• Technical Committee: ISO/TC 165 - Timber structures
• Drafting Committee: ISO/TC 165/WG 12 - Structural use of bamboo
• Current Stage: 6060 - International Standard published
• Start Date: 03-Jun-2021
• Due Date: 25-Jul-2021
• Completion Date: 03-Jun-2021

Relations

• Revises: ISO 22156:2004 - Bamboo - Structural design
• Effective Date: 27-May-2017

Overview

ISO 22156:2021 - "Bamboo structures - Bamboo culms - Structural design" is an international standard that sets out structural design requirements for buildings whose primary load-bearing elements are made from round bamboo culms or shear-panel systems framed with round bamboo. It addresses mechanical resistance, serviceability and durability for mainly low-rise construction (one- and two-storey residential, small commercial/institutional and light industrial buildings not exceeding 7 m in height). The standard focuses on design approaches and performance requirements; non-structural topics such as thermal or sound insulation are outside its scope.

Key topics and technical requirements

• Scope and limits: Applicable to round bamboo culms and shear panels; excludes engineered bamboo products (glue‑laminated, cross‑laminated, oriented strand, densified materials), bamboo‑reinforced non-bamboo primary systems, and scaffolding.
• Design methodologies permitted: Allows Allowable Load-bearing Capacity Design (ACD) and Allowable Stress Design (ASD) approaches, and recognises Partial Safety Factor Design (PSFD)/ Load and Resistance Factor Design (LRFD), documented design-by-testing, and established practice from previous generations.
• Material properties and modification factors: Provides characteristic strength and stiffness values and empirically derived modification factors (designated Ci) to account for bamboo variability.
• Member and system guidance: Detailed coverage of flexural members (beams), axial (compression and tension) members, combined loading, trusses, shear panels (walls), and serviceability (deflection, long‑term behaviour).
• Joints and splices: Requirements for joint capacity, stiffness, ductility, radial clamping to resist splitting, dowel behaviour, metallic and grouted components, and lashing/mechanical systems.
• Durability and service classes: Service class definitions, use classes and guidance on durability, corrosion of metallic elements and maintenance/inspectability.
• Seismic and fire considerations: Seismic force reduction factors and basic fire‑resistance aspects are addressed (see informative annexes for examples).
• Quality control: Structural grading, quality assessment and execution practices are covered as they affect design compliance.

Practical applications and users

ISO 22156 is intended for:

• Structural engineers and designers developing bamboo-framed low-rise buildings
• Architects and builders specifying bamboo culms and shear-panel systems
• Material testers and fabricators establishing characteristic values and joint test data
• Regulators and standards bodies referencing safe design methods for bamboo construction

Use cases include low-rise housing, community buildings, light commercial structures and experimental or sustainable construction projects that use round bamboo culms as the primary load-bearing system.

Related standards (if applicable)

Project teams should combine ISO 22156 with relevant regional building codes, materials testing standards and other ISO/EN standards on structural design, timber engineering and fire safety to ensure comprehensive compliance and performance verification.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 22156
Second edition
2021-06
Bamboo structures — Bamboo culms
— Structural design
Structures en bambou — Tiges de bambou — Conception des
structures
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms . 4
5 Basic requirements of design . 6
5.1 General . 6
5.2 Design methodology. 7
5.3 Susceptibility to splitting . 7
5.4 Redundancy . 7
5.4.1 Non-redundant structural members . 7
5.4.2 Redundant structural members . 7
5.5 Serviceability considerations . 8
5.6 Service classes . 8
5.6.1 Service class 1 . 8
5.6.2 Service class 2 . 8
5.6.3 Service class 3 . 8
5.7 Durability . 8
5.7.1 Use classes . 9
5.7.2 Resistance to corrosion of metallic elements .10
5.8 Effects of elevated temperature .10
5.9 Maintenance, inspectability and replacement considerations .10
5.10 Seismic force reduction factor for bamboo structures .10
5.11 Alternate design methodologies .10
5.11.1 Partial safety factor design (PSFD) or load and resistance factor design
(LRFD) methodology .10
5.11.2 Experience from Previous Generations .10
5.11.3 Design by testing .11
6 Member component and material properties .11
6.1 General .11
6.2 Characteristic material and component properties .12
6.3 Allowable member design capacity .12
6.4 Allowable design strength .13
6.4.1 Culm geometry for use with allowable design strength .14
6.5 Component flexural stiffness .15
6.6 Modulus of elasticity .15
7 Structural modelling bamboo structures .15
8 Flexural members (beams) .16
8.1 General .16
8.2 Multiple culm flexural members .16
8.2.1 Bracing requirements for multiple culm flexural members .17
8.3 Flexural member capacity .17
8.3.1 Flexural capacity determined from component capacity .17
8.3.2 Flexural capacity determined from bending strength .18
8.4 Calculation of deflection .18
8.4.1 Flexural stiffness determined from component properties .19
8.4.2 Flexural stiffness determined from material and geometric properties .19
8.4.3 Long term deflections .19
9 Axial load carrying members .19
9.1 General .19
9.2 Compression member effective length.20
9.2.1 Lateral restraint of compression members .20
9.3 Compression capacity .21
9.3.1 Compression capacity from geometric and material properties .21
9.3.2 Crushing capacity .21
9.3.3 Buckling capacity . .22
9.4 Tension capacity .22
9.4.1 Tension capacity from component capacity .22
9.4.2 Tension capacity from geometric and material properties .23
9.5 Combined axial and flexural loads .23
10 Joints and splices .23
10.1 General .23
10.2 Design properties by complete joint testing .24
10.3 Design properties by component capacities .24
10.4 Allowable joint design capacity .24
10.5 Joint stiffness .25
10.6 Ductility of joints .25
10.7 Robustness against culm splitting .25
10.7.1 Radial clamping to resist splitting .26
10.8 Splices joints .26
10.9 Requirements for non-bamboo components of joints .26
10.9.1 Metallic components of joints .26
10.9.2 Joints utilising flowable infill material (grouted joints) .26
10.9.3 Lashing .27
10.9.4 Mechanical and proprietary joint systems .27
10.10 End bearing capacity of bamboo culms .27
10.11 Circumferential bearing capacity of bamboo culms .27
10.12 Joints having through culm wall dowels .29
10.12.1 Capacity of single dowel .29
10.12.2 Requirements for dowels .31
10.12.3 Tension forces on dowel joints .31
11 Trusses .31
12 Shear panels (walls) .32
12.1 General .32
12.1.1 Openings in panels .32
12.2 Loads . .33
12.2.1 Out-of-plane loads .33
12.2.2 In-plane loads .34
12.2.3 Gravity loads .35
12.3 Determination of design strengths .35
13 Fire resistance .36
14 Structural grading .36
15 Quality assessment and control.36
Annex A (informative) Bases of provisions in this document.37
Annex B (informative) Durability and preservation recommendations .38
Annex C (informative) Examples of seismic and alternative design factors .40
Annex D (informative) Examples and classification of bamboo connections and joints .41
Annex E (informative) Design of LCBF components to satisfy requirements of 12 .45
Bibliography .48
iv © ISO 2021 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 165, Timber structures
This second edition cancels and replaces the first edition (ISO 22156:2004), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— adoption of design equations for material or component capacities for both members and joints;
— adoption of service classes and specific consideration of susceptibility to splitting;
— addition of Light Cement Bamboo Frame (LCBF) construction;
— addition of informative annexes addressing durability and representative details for connections
and LCBF construction;
— removal of use of bamboo for reinforcing concrete or soil.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
This document provides a means of structural design for one- and two-storey building structures using
full-culm round bamboo poles as the primary vertical and horizontal structural load resisting systems.
This document addresses connection design, light cement bamboo frame shear panel design, and
addresses issues of durability. Informative annexes provide means of achieving design and performance
goals in these areas.
vi © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 22156:2021(E)
Bamboo structures — Bamboo culms — Structural design
1 Scope
This document applies to the design of bamboo structures whose primary load bearing structure is
made of round bamboo or shear panel systems in which the framing members are made from round
bamboo.
Except as indicated in Clause 12, this document applies to one- and two-storey residential, small
commercial or institutional and light industrial buildings not exceeding 7 m in height.
This document is concerned only with requirements for mechanical resistance, serviceability and
durability of bamboo structures.
This document permits an allowable load-bearing capacity design (ACD) and/or allowable stress design
(ASD) approach for the design of bamboo structures. Allowable load-bearing capacity and allowable
stress approaches may be used in combination in the same structure.
This document additionally recognises design approaches based on partial safety factor design (PSFD)
and/or load and resistance factor design (LRFD) methods (5.11.1), previous established experience
(5.11.2), or documented ‘design by testing’ approaches (5.11.3).
Other requirements, such as those concerning thermal or sound insulation, are not considered. Bamboo
structures may require consideration of additional requirements beyond the scope of this document.
Execution is covered to the extent that it impacts the quality of construction materials and products
required to comply with the design requirements contained herein.
This document provides a number of modification factors, designated C . These are empirically derived
i
factors, based on best available engineering judgement, that are believed to be universally applicable
to bamboo materials that are appropriate for building construction. Parameters affecting bamboo
material performance are many and are addressed explicitly through the use of experimentally
determined characteristic values of strength and stiffness. Annex A provides a summary of the bases
upon which the provisions of this document were developed.
This document does not apply to
— structures made of engineered bamboo products such as glue-laminated bamboo, cross-laminated
bamboo, oriented strand, or densified bamboo materials,
— bamboo-reinforced materials where bamboo is not the primary load-bearing constituent. This
includes bamboo-reinforced concrete, masonry and soil, or,
— scaffold structures constructed with bamboo.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 12122-1, Timber structures — Determination of characteristic values — Part 1: Basic requirements
ISO 12122-5, Timber structures — Determination of characteristic values — Part 5: Mechanical connections
ISO 12122-6, Timber structures — Determination of characteristic values — Part 6: Large components
and assemblies
ISO 16670, Timber structures — Joints made with mechanical fasteners — Quasi-static reversed-cyclic test
method
ISO 19624, Bamboo structures — Grading of bamboo culms — Basic principles and procedures
ISO 21581:2010, Timber structures - Static and cyclic lateral load test methods for shear walls
ISO 21887, Durability of wood and wood-based products — Use classes
ISO 22157, Bamboo structures — Determination of physical and mechanical properties of bamboo culms —
Test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
assembly
multiple-culm assembly
structural member comprised of more than one bamboo culm constructed in such a fashion that the
multiple culms together serve as a single structural member
3.2
bamboo culm
bamboo pole
single shoot of bamboo
Note 1 to entry: A culm is comprised of the entire unaltered bamboo cross section and is usually a hollow cylinder
except at nodes.
3.3
cross sectional area
A
area of the section perpendicular to the direction of the longitudinal axis of the culm
3.4
ductility
μ
ratio of the experimentally determined ultimate displacement to the yield displacement
1)
Note 1 to entry: The ratio is determined according to ISO/CD TR 21141 for joints.
3.5
equilibrium moisture content
w
EMC
moisture content at which bamboo is neither gaining moisture from, nor losing moisture to, the
environment
3.6
fibre saturation point
w
FSP
moisture content below which only water bound in the cell walls remains; i.e., condition in which there
is no free water in the cell cavities
1)  In preparation. Stage at the time of publication ISO/CD TR 21141:2021.
2 © ISO 2021 – All rights reserved

3.7
flattened bamboo
element obtained by opening the bamboo culm and making longitudinal cuts (scores) partially through
the culm wall to make a flat member
Note 1 to entry: Flattened bamboo is often referred to as “esterilla”.
3.8
internode
typically hollow region of bamboo culm between two nodes
3.9
joint
connection of two or more bamboo members
3.10
lashing
means of connecting bamboo culms by continuous wrapping of material around culm and joint region
3.11
light cement bamboo frame
LCBF
improved vernacular construction technique originating in Latin America utilising shear walls
constituted from a cement mortar render applied onto strip, flattened or small diameter bamboo, which
are fixed onto bamboo and/or timber studs or framing
Note 1 to entry: The cement mortar render is reinforced by a small-gauge metal mesh such as “chicken wire”. An
alternative technique in which the cement mortar render is applied directly onto expanded metal lath sheets,
which are in turn fixed onto the frame, is also accepted. The system is also known as "bahareque encementado"
and composite bamboo shear walls.
3.12
moisture content
w
portion of culm weight consisting of water expressed as percentage of oven-dry weight
3.13
node
transverse diaphragm region located along length of culm separating adjacent internodes
3.14
non-redundant
structural member is non-redundant if there is no alternative and sufficient load path in the structure
to transmit the load carried by the member in the event of its removal (member failure) from the load
path
Note 1 to entry: Failure of a non-redundant member leads to failure of the load path in which it is a part.
3.15
outer diameter
D
diameter of the cross section of a piece of bamboo, typically made near the centre of an internode, taken
as the average of two perpendicular measurements made across opposite points on the outer surface or
calculated from a measurement of the perimeter
3.16
point of contraflexure
point of inflection
location of zero moment where the curvature of the member is zero
3.17
shear span
distance between the maximum moment and the nearest point of contraflexure
(3.16)
Note 1 to entry: Shear span is conventionally assumed to be equal to half the span for a uniformly loaded simple
beam and half the column height for a column resisting lateral load.
3.18
splice
connection of two bamboo culms along their common longitudinal axis; used to extend the length of a
structural member beyond the length of an individual culm
3.19
bamboo strip
bamboo piece with outer and inner layers intact, made by cutting bamboo culm in longitudinal direction
3.20
[culm] wall thickness
δ
thickness of wall of bamboo culm, typically made near the centre of an internode, taken as the average
of four measurements taken around the circumference of the culm at angular spacings of 90°
3.21
working point
location where the resultants of axial loads carried by
connecting members intersect
4 Symbols and abbreviated terms
A cross sectional area of a single culm
A minimum cross sectional area of the individual culms comprising the member
min
a length of the shear span of a member
B moment amplification factor
b length of LCBF panel
b maximum perpendicular distance from the centre of the culm cross section to the chord
max
drawn from the centres of the ends of the piece of bamboo
b maximum measured bow at midheight of culm comprising compression member
o
C compression force in end member of LCBF resisting overturning moment
C reduction factor to account for an initial bow in culms comprising a compression member
bow
C modification factor for Service Class and load duration for modulus
DE
C modification factor for Service Class and load duration for capacity and strength
DF
C modification factor for end bearing condition
EB
C member redundancy factor
R
C modification factor for elevated temperature
T
C modification factor accounting for shear deformations
v
C correction factor accounting for the angle of loading relative to the longitudinal axis of
θ
the culm
c calibration parameter for column interaction equation
D nominal culm diameter
D diameter of dowel
dowel
d overall depth of a flexural member
4 © ISO 2021 – All rights reserved

Δ ultimate joint displacement
u
Δ yield joint displacement
y
E modulus of elasticity used in design
d
E mean characteristic compressive modulus of elasticity with 75 % confidence determined
k
from ISO 22157
(EI) component flexural stiffness used in design
d
(EI) mean characteristic component flexural stiffness with 75 % confidence
k
F applied horizontal force (from wind or seismic analysis) to LCBF
F allowable bearing stress under a dowel
b
F restraint force oriented perpendicular to the principal axis of an axial load carrying or
resf
flexural member
FS component factor of safety
c
FS joint factor of safety
j
FS material factor of safety
m
F joint capacity
y
th
F 5 percentile characteristic capacity of joint with 75 % confidence
yk
f compression strength parallel to fibres determined from ISO 22157
c
f generic nomenclature indicating allowable design strength of bamboo
i
th
f 5 percentile characteristic strength with 75 % confidence
ik
f bending strength parallel to fibres determined from ISO 22157
m
f bending strength perpendicular to fibres determined from ISO 22157
m90
f tension strength parallel to fibres determined from ISO 22157
t
f tension strength perpendicular to fibres determined from ISO 22157
t90
f shear strength determined from ISO 22157
v
h height of LCBF panel
I moment of inertia of a single culm
I minimum moment of inertia of the individual culms comprising a member
min
K effective length coefficient
K stiffness of joint
e
K mean characteristic joint stiffness with 75 % confidence
ek
K factor used in circumferential bearing calculation
M
KL effective compression member length
L length along the culm of the region of circumferential bearing
cir
L length of member
L working length of axial load carrying member between points of lateral restraint
LCBF light cement bamboo frame
M bending capacity of a single culm or a multiple culm component bent about its principal axis
M design moment
cd
M moment capacity of a single or multiple culm member
r
M maximum moment resisted by a flexural member
u
w moisture content of bamboo
w equilibrium moisture content
EMC
w moisture content of bamboo at fibre saturation point
FSP
w moisture content at the time of testing
M
N compression capacity parallel to the fibres of a single culm or a multiple culm component
c
N design compression force
cd
N compressive load applied to an axial load carrying member
cr
N tension capacity parallel to the fibres of a single culm
t
N design tensile force
td
N tensile load applied to an axial load carrying member
tr
n number of culms comprising a member
P end bearing capacity of unfilled bamboo culms
b
P crushing strength of a compression member
c
P circumferential bearing capacity of an unfilled bamboo culm
cir
P buckling capacity of a compression member
e
P maximum axial load resisted by a compression member
u
p circumferential bearing pressure;
cir
S elastic section modulus of a single culm
s least spacing between adjacent dowels located along the same longitudinal gauge line, or the
distance from the dowel to the nearest node or end of the culm in the direction of loading
T tensile force in end member of LCBF resisting overturning moment
V shear capacity of a single culm or a multiple culm component subject to flexure about its
principal axis
V base shear force resisting applied horizontal force in LCBF
b
V shear capacity of a single or multiple culm member
r
X generic nomenclature indicating allowable design capacity of bamboo member
i
th
X 5 percentile characteristic component capacity with 75 % confidence
ik
β central angle describing portion of circumference over which bearing pressure is applied
δ nominal [culm] wall thickness
θ angle of load applied to dowel connector relative the longitudinal axis of the culm
μ joint ductility
ψ central angle between adjacent gauge lines of dowel connectors
5 Basic requirements of design
5.1 General
This document is based on an allowable load-bearing capacity design (ACD) or allowable stress design
(ASD) approach to ensure the safety and performance of the structure.
A structure shall be designed and constructed such that
— with acceptable probability, it will remain fit for its intended use, having due regard to its intended
life and costs,
— with appropriate reliability, it will resist all actions and influences likely to occur resulting from
its intended use over its intended life, and have adequate durability in relation to maintenance
requirements, and
— it will not represent a hazard to human life by exceptional events such as explosion, impact or
consequence of human error, to an extent disproportional to the magnitude of the exceptional event.
6 © ISO 2021 – All rights reserved

5.2 Design methodology
Bamboo structures shall be designed based on calculations, verifying that no relevant allowable load-
bearing capacity or stress is exceeded. The following are assumed:
— structures are designed by appropriately qualified and experienced design professionals;
— structures are constructed by personnel having appropriate skills and experience;
— adequate supervision and quality control are provided in factories, plants and on site;
— construction materials and products are used as specified in this document or in the relevant
material or product specifications;
— structures are adequately maintained;
— structures will be used in accordance with their intended occupancy and design.
5.3 Susceptibility to splitting
Bamboo culms are susceptible to longitudinal splitting. Splitting is commonly related to changes
in moisture content of the culm in service. The susceptibility to splitting can lead to non-redundant
members (5.4.1) and may necessitate replacement of culms in a member or structure (5.9).
The effects of splitting in design may be investigated using a notional approach in which a single
notional split is assumed to occur at the least favourable location in a member or joint. In this state, the
member or joint shall be shown to retain at least 75 % of its capacity. If at least 75 % of the capacity is
not retained, the member or joint shall be designed assuming that the notional split will occur and a
reduced capacity shall be used in design.
The effects of splitting may be partially mitigated using radial clamping described in 10.7.1.
5.4 Redundancy
To the extent possible, non-redundant structures and/or structural members or components should not
be used.
The member redundancy factor, C , shall be defined by Table 1.
R
Table 1 — Member redundancy factor, C
R
redundancy of member in structure C
R
non-redundant as defined in 5.4.1 0,90
redundant as defined in 5.4.2 1,10
all other structures 1,00
5.4.1 Non-redundant structural members
Non-redundant structural members shall be those satisfying the following criteria.
— load-bearing members whose removal from the structure or load path result in failure of the
structure, or
— load-bearing members made of multiple culms for which the removal of any single culm from the
multiple culm assembly results in failure of the member.
5.4.2 Redundant structural members
Redundant structural members shall be those satisfying the following criteria.
Where four or more structural members of the same stiffness are connected to a continuous load
distribution path (such as may be the case with floor joists, rafters, purlins and trusses) and, in addition,
either
— the continuous load distribution path is capable of redistribution of loads, or
— the structural members are no more than 600 mm apart, the load distribution members are
continuous over at least two spans, and any joints in the load distribution members are staggered.
5.5 Serviceability considerations
Deflections of the structure or its components likely to affect use or occupancy of the structure or
damage finishes or non-structural components shall be considered.
5.6 Service classes
Members in a bamboo structure shall be assigned to one of the service classes given by 5.6.1, 5.6.2, or
5.6.3 based on the environment to which the bamboo is exposed. These service classes are related to
the mechanical performance of the bamboo. Use classes associated with durability performance are
prescribed in 5.7.1. Different elements or members in the same structure may have different service
classes.
5.6.1 Service class 1
Service Class 1 is characterised by an equilibrium moisture content in the bamboo not exceeding 12 %.
NOTE Service Class 1 is representative of indoor air-conditioned or heated environments in which relative
humidity is maintained below 65 % and will generally correspond to ISO 21887 Use Class 1 (see 5.7.1).
5.6.2 Service class 2
Service class 2 is characterised by an equilibrium moisture content in the bamboo not exceeding 20 %.
NOTE Service Class 2 is representative of indoor unheated or uncooled environments in most locations
except those with relative humidity regularly or for prolonged periods exceeding 85 % and will generally
correspond to ISO 21887 use class 2 or 3.1 (see 5.7.1).
5.6.3 Service class 3
Service class 3 is characterised by ambient or climatic conditions leading to higher moisture content in
the bamboo than experienced in Service Class 2.
Load duration factors (C and C ) and elevated service temperature factor (C ) for Service Class 3
DF DE T
shall be determined experimentally (5.11.3)
5.7 Durability
Provision shall be made in the design of bamboo structures to ensure durability of the structure.
Durability is the ability of bamboo to resist degradation of geometric, physical or mechanical properties
when subject to an intended service environment for an intended service life. Effects of fire are
addressed in Clause 13.
No species of bamboo is known to have significant natural resistance to biological attack. Bamboo shall
be considered “non-durable”, requiring preservation, in terms of its resistance to the following:
— fungal attack;
— attack by wood boring insects and termites; and,
8 © ISO 2021 – All rights reserved

— marine borers for bamboo exposed to a marine environment.
Treatment shall be either demonstrated to not affect bamboo mechanical properties (strength and
stiffness) or, more typically, mechanical properties defined in Clause 6 shall be determined for treated
bamboo.
The following general considerations for durable structures are required:
— construct only with bamboo that has achieved its equilibrium moisture content, w , for the
EMC
location of the building. Moisture content, w, shall never exceed the fibre saturation point, w ,
FSP
which, if unknown may be assumed to be w = 30 %;
FSP
— building details shall be such that the bamboo shall remain air-dry by ventilation and ensure that if
the bamboo does become temporarily wet, it will dry before material deterioration can occur; and,
— building envelope permeability shall be such that negative pressure resulting from heating,
ventilation and/or air conditioning, likely to draw water or moisture into the bamboo, is mitigated.
Annex B provides additional recommendations for designing durable bamboo structures.
5.7.1 Use classes
Bamboo within a structure shall be assigned to one of the use classes defined by ISO 21887 based on
the environment to which the bamboo is exposed. Table 2 summarises Use classes and basic durability
considerations.
Bamboo should not be used in use class 3.2 except for structures having a design life of less than 5 years.
Bamboo shall not be used in use classes 4 or 5.
Table 2 — Use classes, durability considerations and appropriate preservation techniques
Protection against biological
Use
agents
service conditions typical uses
class
fungal insects termites
framing, pitched roof mem-
1 interior, dry - yes yes
bers
interior, occasional framing, roof members,
2 damp (possibility of ground floor joists, framing yes yes yes
condensation) built into exterior walls
exterior, above ground
protected exterior joinery
3.1 protected from driving yes yes yes
and framing
rain and UV radiation
unprotected exterior fram-
exterior, above ground ing and joinery including
a
3.2 not protected from cladding, vertical load yes yes yes
weathering bearing members, exposed
unprotected culm ends
in contact with ground
sole plates or columns at
or
b
4.1 ground, columns built into yes yes yes
ground, piles
in-ground
in-ground severe, fresh
b
4.2 piles yes yes yes
water
marine or brackish marine piles including splash
b
5 yes
water zone
a
Bamboo should not be used in use class 3.2 except for structures
...