ISO 5257:2023

INTERNATIONAL ISO
STANDARD 5257
First edition
2023-12
Bamboo structures — Engineered
bamboo products — Test methods
for determination of mechanical
properties using small size specimens
Structures en bambou — Produits en bambou reconstitués —
Méthodes d'essai pour la détermination des propriétés mécaniques à
partir d'éprouvettes de petites tailles
Reference number
© ISO 2023
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Reference population .4
6 Sampling . 4
7 Conditioning of test specimens . 4
8 Test conditions .5
9 Density and moisture content . 5
9.1 Density . 5
9.2 Moisture content . 5
10 Measurement of mechanical properties. 5
10.1 Tensile properties parallel-to-fibre. 6
10.1.1 Preparation of test specimens . 6
10.1.2 Test procedure. 6
10.1.3 Expression of results . 7
10.2 Compressive properties parallel-to-fibre . 7
10.2.1 Preparation of test specimens . 7
10.2.2 Test procedure. 7
10.2.3 Expression of results . 8
10.3 Shear strength and modulus . 8
10.3.1 Preparation of test specimens . 8
10.3.2 Test procedure. 9
10.3.3 Expression of results . 9
10.4 Tension properties perpendicular-to-fibre . 10
10.4.1 Preparation of test specimens . 10
10.4.2 Test procedures . 11
10.4.3 Expression of results .12
10.5 Compression properties perpendicular-to-fibre .12
10.5.1 Preparation of test specimens .12
10.5.2 Test procedure.13
10.5.3 Expression of results . 13
11 Test report .13
Annex A (informative)  .15
Bibliography .18
iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
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.
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.
iv
Introduction
Engineered bamboo products are processed bamboo-based composites designed for structural
applications, including bamboo scrimber and glued laminated bamboo. For each type of engineered
bamboo product, it is necessary to measure mechanical properties. This document is intended to
provide manufacturers, regulatory agencies, and end-users with a means to evaluate the mechanical
properties of engineered bamboo products intended for structural applications using small size
specimens.
This document is an internationally agreed reference standard for the measurement of mechanical
properties of engineered bamboo products as defined in 3.1 and 3.2. Other standards related to the
measurement of material properties may be deemed to comply with this document, provided that
the adjustments necessary to establish equivalency between this and other standards are applied
appropriately.
v
INTERNATIONAL STANDARD ISO 5257:2023(E)
Bamboo structures — Engineered bamboo products — Test
methods for determination of mechanical properties using
small size specimens
1 Scope
This document specifies test methods, using small size specimens, suitable for determining the
following mechanical properties of engineered bamboo products: tensile strength parallel-to-
fibre; tensile modulus parallel-to-fibre; compressive strength parallel-to-fibre; tensile strength
perpendicular-to-fibre; tensile modulus perpendicular-to-fibre; compressive strength perpendicular-
to-fibre; compressive modulus perpendicular-to-fibre; shear strength parallel-to-fibre and shear
modulus parallel-to-fibre.
NOTE This document provides an alternative test method to ISO 23478.
This document specifies test procedures for currently manufactured products as defined in 3.1 and 3.2
to evaluate material properties. The methods specified in this document are applicable to small size
test specimens. The methods required to determine characteristic values, design values, or allowable
values of the mechanical properties for a population are out of the scope of this document. Materials
that do not conform to the definitions of bamboo scrimber or glued-laminated bamboo are beyond the
scope of this specification.
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 23478, Bamboo structures — Engineered bamboo products — Test methods for determination of
physical and mechanical properties
ASTM D2915, Sampling and data-analysis for structural wood and wood-based products
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
bamboo scrimber
panel or lumber made of compressed bamboo fibre bundle strips or compressed bamboo fibre bundle
sheet which has three mutually perpendicular axes
Note 1 to entry: The three axes are shown in Figure 1.
Note 2 to entry: Bamboo scrimber can be approximately deemed as orthotropic material; hence it has two
mutually orthogonal minor axes in the plane perpendicular to the major axis. Unless otherwise stated, the
properties of two minor axes can be ideally considered to have same properties because the differences between
them are trivial for structural use.
Key
1 along the direction of the bamboo fibres
2, 3 two mutually orthogonal directions in a plane that is perpendicular to axis-1
Figure 1 — Example of bamboo scrimber
Key
1 along the direction of the bamboo fibres
2, 3 two mutually orthogonal directions in a plane that is perpendicular to axis-1
Figure 2 — Example of glued laminated bamboo
3.2
glued laminated bamboo
structural member formed by bonding together bamboo strips with their fibre orientation essentially
parallel which has three mutually perpendicular axes
Note 1 to entry: The three axes are shown in Figure 2.
3.3
grade
population of engineered bamboo products with defined design properties
4 Symbols
A
area of the cross section of the compressive specimen, in mm
c
b width of critical section located at the reduced cross section, in mm
d
coupon width between notches of the V-notched rail shear test specimen, in mm
E
modulus of elasticity parallel to the fibre, in N/mm
E
modulus of elasticity in compression parallel to the fibre, in N/mm
c,0
E
modulus of elasticity in tension parallel to the fibre, in N/mm
t,0
Et,90 modulus of elasticity in tension perpendicular to the fibre, in N/mm
F load, in N
F
compressive load parallel to the fibre at failure, in N
cu,,0
F
compressive load perpendicular to the fibre at failure, in N
cu,,90
F
shear load at failure, in N
su,
F
tensile load parallel to the fibre at failure, in N
tu,,0
F
tensile load perpendicular to the fibre at failure, in N
tu,,90
f
compressive strength parallel to the fibre, in N/mm
c,0
f
shear strength parallel to the fibre, in N/mm
s,0
f
tensile strength parallel to the fibre, in N/mm
t,0
f
tensile strength perpendicular to the fibre, in N/mm
t,90
f
shear strength perpendicular to the fibre, in N/mm
s,90
G shear modulus, in N/mm
G
shear modulus parallel to the fibre, in N/mm
G
shear modulus perpendicular to the fibre, in N/mm
h overall coupon thickness of the V-notched rail shear test specimen, in mm
t thickness of critical section located at the reduced cross section, in mm
ΔF
incremental compressive load parallel to the fibre, in N
c,0
ΔF
incremental tensile load parallel to the fibre, in N
t,0
ΔF
incremental tensile load perpendicular to the fibre, in N
t,90
ΔF
incremental shear load parallel to the fibre, in N
s,0
ΔF
incremental shear load perpendicular to the fibre, in N
s,90
Δσ
incremental stress, in MPa
Δσ ΔΔσ = Fb/ t , incremental compressive stress parallel to the fibre, in MPa
c,0 cc,,00
Δσ ΔΔσ = Fb/ t , incremental tensile stress parallel to the fibre, in MPa
t,0 tt,,00
Δσ ΔΔσ = Fb/ t , incremental tensile stress perpendicular to the fibre, in MPa
t,90 tt,,90 90
Δε
incremental strain
Δε
incremental compressive strain parallel to the fibre
c,0
Δε
incremental tensile stain parallel to the fibre
t,0
Δε
incremental tensile stain perpendicular to the fibre
t,90
Δε
incremental stain over a gauge length at +45 direction
+45
Δε
incremental stain over a gauge length at -45 direction
−45
5 Reference population
The population from which the test sample was obtained shall be fully described. The description shall
reference all of the attributes that may affect evaluated properties or restrict constituent materials to
the grouping. The description shall include but is not limited to:
a) species or species grouping, population boundary;
b) age of the bamboo feedstock when harvested;
c) designation of the product;
d) size or size range of the product;
e) moisture condition of the product;
f) preservative treatment of the product;
j) period in which the product was manufactured.
The reference population shall be a grouping from which a representative sample can be drawn to test
specimens to characterize the required properties.
6 Sampling
The sampling shall be appropriate to the purpose
...