ISO 19624:2018

INTERNATIONAL ISO
STANDARD 19624
First edition
2018-09
Bamboo structures — Grading of
bamboo culms — Basic principles and
procedures
Structures en bambou — Classement des tiges de bambou
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 4
5 General . 4
5.1 Grading. 4
5.2 Grades . 4
5.3 Graded bamboo culms . 5
5.4 Grading operations . 5
5.5 Secondary properties . 5
6 Visual grading . 5
6.1 General . 5
6.2 Visual grading requirements . 5
6.2.1 General. 5
6.2.2 Condition properties . 6
6.2.3 Geometric properties . 7
6.3 Other requirements for visual grading .10
6.3.1 Moisture content .10
6.3.2 Age at harvesting .10
6.4 Check on visual grading process .11
7 Machine grading.11
7.1 General .11
7.2 Machine grading process requirements .11
7.3 Indicating properties .11
7.4 Grade-determining properties .12
7.5 Visual override .12
7.6 Hybrid grading methods .12
8 Structural properties of graded bamboo .12
8.1 General .12
8.2 Initial evaluation .12
8.2.1 Developing visual grading rules .13
8.2.2 Developing grading settings for machine grading .13
8.2.3 Sampling.13
8.2.4 Sample size for initial evaluation .14
8.2.5 Other considerations during initial evaluation testing .14
8.3 Periodic evaluation .14
8.4 Reduced test programmes and secondary properties .15
9 Product identification .15
10 Documentation .15
Annex A (informative) Example of application of clauses in this document to a visual
grading standard for bamboo culms based on external diameter and flexural properties 16
Bibliography .22
Foreword
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This document was prepared by ISO Technical Committee 165, Timber structures.
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iv © ISO 2018 – All rights reserved

Introduction
The general principle of this document is that any type of grading procedure is acceptable, provided it is
defined, controlled, and documented to the extent required to achieve the degree of reliability intended
for the structural application of the product. This document specifies procedures that conform to
this principle. The grading procedures outlined in this document require visual, dimensional and
mechanical stages to ensure conformity.
Annex A provides an example conformance standard reflecting the requirements of this document.
INTERNATIONAL STANDARD ISO 19624:2018(E)
Bamboo structures — Grading of bamboo culms — Basic
principles and procedures
1 Scope
This document specifies grading procedures for visually and mechanically sorting round, or pole,
bamboo for structural applications using such fundamental elements. Visual sorting is based on
observable characteristics of the piece(s). Mechanical sorting is based on non-destructive measurement
of properties known to correlate to characteristic values defining a grade.
The grading procedures in this document can be used in a quality acceptance regime, although this
document does not define or address acceptance criteria.
This document is applicable only for bamboo that is graded in the seasoned state.
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 22156, Bamboo — Structural design
ISO 22157-1, Bamboo — Determination of physical and mechanical properties — Part 1: Requirements
ISO 12122-1, Timber structures — Determination of characteristic values — Part 1: Basic requirements
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
bamboo culm
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.
3.2
bow
measure of variation of culm from straight condition, reported as the ratio of greatest transverse
variation to reference length of culm
3.3
dry bamboo
seasoned bamboo
bamboo that has been subjected to a drying process and with moisture content of 19 % or less
3.4
fissure
longitudinally oriented separation or split of the bamboo wall running parallel to the fibres at the end of
a culm or at any internode of the piece that may or may not penetrate through the entire wall thickness
Note 1 to entry: An example of a fissure is shown in Figure 1.
3.5
geometric property
measurable dimensional property of bamboo piece, generally used in reference to diameter, wall
thickness, length and internode length
3.6
grade-determining property
GDP
mechanical, geometric or physical property for which a particular value should be achieved for the
material to be assigned to that grade
3.7
indicating property
IP
measurement or combination of measurements made during grading, which are related to one or more
of the grade-determining properties
3.8
initial evaluation
process prior to grading during which the geometric, physical and mechanical properties for bamboo
originating from a source region will be assessed with the aim of developing reliable selection criteria
3.9
internode
usually hollow region of bamboo culm between two nodes at which diameter and wall thickness
are defined
3.10
longitudinal indentation
longitudinal depression running parallel to the fibres that may indicate the presence of an internal
fissure that is not visible externally
Note 1 to entry: An example of a longitudinal indentation is shown in Figure 2.
3.11
mechanical property
measurable property of bamboo associated with both culm geometry and bamboo material properties
that describes behaviour under the effects of applied load or stress, generally used in reference to
member or section strength or stiffness
3.12
moisture content
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
Note 1 to entry: The separation between nodes varies along the culm. When alive, nodes are locations of leaf and
branch growth.
2 © ISO 2018 – All rights reserved

3.14
ovality
degree of variation of culm cross section from circular, reported as the ratio of the greatest to least
diametric measurement at a specific location
3.15
physical property
measureable or observable property of bamboo that describes its behaviour to external influences
other than stress or strain, generally used in reference to density, moisture content, etc.
3.16
producer
supplier
organization responsible for the grading process, which usually would be the same organization
responsible for drying and preserving the bamboo culms
3.17
proof testing
non-destructive structural testing protocol involving loading the culm (or structural assembly) to a
predetermined value to assess its ability to carry this load
Note 1 to entry: Not addressed by this document.
3.18
source region
geographical location from which the bamboo resource originates
3.19
structural capacity
load carrying capacity of a culm which is a function of mechanical, geometric and physical properties of
the culm
Note 1 to entry: Usually expressed in kiloNewtons (force) or kiloNewtons-metre (moment).
3.20
taper
degree of change of outer diameter (external taper), internal diameter (internal taper), section area
(areal taper) or other geometric property along length of culm, expressed as percentage of the length of
the culm
3.22
unseasoned bamboo
bamboo with moisture content greater than 19 %
3.23
grading rules
visual set of criteria used to sort bamboo pieces during visual grading
Note 1 to entry: Grading rules should have a demonstrated link to the grades sought.
3.24
visual override
process by which bamboo pieces are excluded from machine grading, because they do not meet criteria
known to be important to grading and that cannot be sensed by the machine
4 Symbols
b maximum perpendicular distance from the centre of the culm section to the chord drawn from
max
the centres of either end of the piece of bamboo, expressed in millimetres
b bow of a piece of bamboo
o
D external diameter of the bamboo culm, expressed in millimetres
D external diameter at the base of a piece of bamboo
b
D maximum external diameter at a given location on a piece of bamboo
max
D minimum external diameter at a given location on a piece of bamboo
min
D external diameter at the top of a piece of bamboo
t
L length of a piece of bamboo, expressed in millimetres
L internode length, expressed in millimetres
in
L reference length of a piece over which the bow of a piece of bamboo is assessed, expressed in
ref
millimetres
δ culm wall thickness, expressed in millimetres
α external taper, expressed as a percentage
e
α internal taper, expressed as a percentage
i
5 General
5.1 Grading
Grading is the process of sorting every piece of bamboo in a sample into grades according to defined
selection criteria. The criteria identify dimensional, visual, geometric, mechanical and/or physical
properties that reflect the bamboo’s mechanical strength or structural capacity and may affect the
utility of the product.
Each grade is associated with a range of mechanical, geometric, physical and/or structural properties
derived from testing. The selection criteria are based on non-destructive observations and
measurements that have been established to be useful to the grading process.
Grading provides a statistically significant prediction of the mechanical, geometric and/or physical
properties of the population within a grade, but does not provide the properties of each individual piece.
Grading is not proof testing. Proof testing can be carried out to increase confidence in selected material,
if desired. Proof testing is beyond the scope of this document.
5.2 Grades
The sorting criteria for a given grade should reliably infer the properties selected as the basis of the
grading process. A grade can be set to correspond to a particular bamboo resource in order to make
optimum use of the resource. Alternatively, a grade can be set to meet the requirements of a particular
end use or specification.
4 © ISO 2018 – All rights reserved

5.3 Graded bamboo culms
Graded bamboo culms are dry (or seasoned) lengths of bamboo in their round form that have been
subjected to a grading process. It should not be assumed that products derived from graded bamboo
culms, such as strips or laminates, are also graded; such products would need to be subjected to a
separate grading process beyond the scope of this document.
5.4 Grading operations
Bamboo shall be visually graded according to Clause 6, and/or machine-graded according to Clause 7.
The grading operation shall be comprised of a visual grader and/or machine(s) sorting an input resource
into output grades. If some of the bamboo does not meet the requirements of the minimum grade, it is
rejected.
5.5 Secondary properties
Secondary properties are physical or mechanical properties for a given grade that are neither measured
nor inferred directly from the grading process. Secondary properties should not be critical to the end
application of the culms. These properties are usually estimated from the grade-determining properties
on the basis of previously derived correlations that are valid for the specific species.
6 Visual grading
6.1 General
Visual grading is understood to be the process of sorting material according to visually measureable
characteristics known to affect the mechanical or structural properties of bamboo culms. Visual
grading can be assisted by machines.
Visual grading operations shall be carried out by a grader that has received appropriate training to
perform this task.
The sorting criteria for visual grading shall be referred to as grading rules, and based on characteristics
known to affect the strength or structural capacity of bamboo culms. These characteristics can be
divided into:
— condition properties;
— geometric properties.
It is permissible to verify the visual grade of a piece by applying the same grading rules.
Re-grading with different grading rules, or visually grading bamboo rejected by machine grading, is
not permitted.
It is possible to supplement the visual grading process by non-destructively assessing properties that
are known to correlate to strength or structural capacity.
6.2 Visual grading requirements
6.2.1 General
Most grading rules can be adapted to suit a particular species and source region, provided they are
developed in accordance with 8.2. The following requirements shall be observed when setting grading
rules or visual override criteria.
6.2.2 Condition properties
Condition properties refer to the state of the material in terms of insect and/or fungal damage, and
defects such as fissures and longitudinal indentation. Visual grading rules shall be based on any
combination of the following observable condition requirements.
6.2.2.1 Insect and fungal damage
Pieces showing evidence of rot or insect damage should normally be rejected.
6.2.2.2 Fissures and longitudinal indentation
Fissures present at the outer surface of any internode, shall be reported and considered in the grading
process. Grading rules should consider the depth, length, location and number of fissures on a given
piece. Figure 1 provides an example of a fissure.
Key
1 fissure
2 node
3 internode
Figure 1 — Manifestation of fissure on surface of culm and cross-section through fissure
Longitudinal indentations present at any internode, shall be reported and considered in the grading
process. Longitudinal indentations can result from internal fissures (Figure 2) or be a natural
manifestation of culm growth. It is permissible to assess the source of the indentations; only
manifestations of internal fissures are reported as condition requirements. Grading rules should
consider the depth, length, location and number of longitudinal indentations.
6 © ISO 2018 – All rights reserved

Key
1 longitudinal indentation
2 internal fissure
3 node
4 internode
Figure 2 — Manifestation of longitudinal indentation and cross-section through internal fissure
and associated indentation
6.2.3 Geometric properties
Geometric properties refers to the directly measurable dimensions of a piece, such as diameter, wall
thickness, internodal length and culm length; as well as properties that represent a deviation from
a straight, hollow cylinder and that require some calculation, such as bow, taper and ovality. Visual
grading shall be made based on any combination of the following measurable dimensional requirements.
6.2.3.1 Diameter
Diameter, D, should normally be considered as a visual grading criteria, as it is significantly affects the
structural capacity of a section.
The diameter is measured at the centre of an internode region.
The diameter can be controlled during grading by any of the following methods:
6.2.3.1.1 Average diameter over culm length
The average of perpendicular measurements made across opposite points on the outer surface at both
ends of the piece. Only this method should be used for initial evaluation.
6.2.3.1.2 Smallest average diameter
The smallest average diameter is the average value of two perpendicular measurements made across
opposite points on the outer surface at the narrowest internode on the piece.
6.2.3.1.3 Smallest absolute diameter
The smallest absolute diameter is the smallest measurement made across opposite points on the outer
surface at the narrowest internode on the piece.
6.2.3.2 Wall thickness
The wall thickness, δ, should normally be considered as a visual grading criteria, but may be inferred
if species-specific diameter-to-thickness relationships are known, or calculated from the mass of the
piece and density of the material.
The wall thickness is usually measured at the centre of an internode region.
When directly measured, the wall thickness can be controlled during grading by any of the following
methods.
6.2.3.2.1 Average wall thickness over culm length
The average wall thickness over culm length is the average value of four measurements taken around
the circumference of the culm, at angular spacings of 90° at both ends of the piece. Only this method
should be used for initial evaluation.
6.2.3.2.2 Smallest average wall thickness
The smallest average wall thickness is the average value of four measurements taken around the
circumference of the culm at angular spacings of 90° at the internode with the thinnest walls on the piece.
6.2.3.3 Internode length
For some applications and for some species, it can be desirable to consider internode lengths, L , during
in
grading.
When directly measured, the internode length can be controlled during grading by any of the following
methods.
6.2.3.3.1 Average of all internode lengths
The average of all internode lengths is the average value of all internode lengths along the piece.
6.2.3.3.2 Average of top and bottom internode lengths
It is the average of the internode lengths of the top- and bottom-most internodes of the piece.
6.2.3.4 Length
Since bamboo properties vary along the culm, the length, L, of pieces during grading should be
consistent with the lengths studied during the initial evaluation.
8 © ISO 2018 – All rights reserved

6.2.3.5 External taper
The external taper can significantly reduce the bending and compression capacity of a culm. The
external taper should be reported and considered in the grading process.
Key
D diameter at the base of the piece
b
D diameter at the top of the piece
t
L length of the piece
δ wall thickness at the base of the piece
b
δ wall thickness at the top of the piece
t
Fig
...