ISO 22389-1:2010

INTERNATIONAL ISO
STANDARD 22389-1
First edition
2010-05-15

Timber structures — Bending strength of
I-beams —
Part 1:
Testing, evaluation and characterization
Structures en bois — Résistance à la flexion des poutres en I —
Partie 1: Essais, évaluation et caractérisation



Reference number
ISO 22389-1:2010(E)
©
ISO 2010

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ISO 22389-1:2010(E)
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ISO 22389-1:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Materials .2
4.1 Flange stock.2
4.2 Web material .2
4.3 Adhesives.3
5 Product evaluation .3
5.1 General .3
5.2 Characteristic shear capacity .4
5.3 Characteristic bearing capacity .6
5.4 Characteristic bending capacity .12
5.5 Characteristic bending stiffness and creep.14
5.6 Web openings and other considerations.15
5.7 Flange tension tests.15
5.8 End joint tension tests.16
Annex A (informative) Analytical method for I-beam bending capacities .17
Annex B (informative) Failure coding in tests of prefabricated wood-based I-beams.20
Bibliography.23

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ISO 22389-1:2010(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for
voting. Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
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.
ISO 22389-1 was prepared by Technical Committee ISO/TC165, Timber structures.
ISO 22389 consists of the following part, under the general title Timber structures — Bending strength of
I-beams:
⎯ Part 1: Testing, evaluation and characterization
Component performance and manufacturing requirements is to form the subject of a part 2.
This part of ISO 22389 is based, with permission of ASTM International, on ASTM D 5055, Standard
Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-Joists, copyright
ASTM International.
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ISO 22389-1:2010(E)
Introduction
Prefabricated wood-based I-beams are being produced in many countries under different national standards
and these products are being exported from one country to another. While the national standards have many
similarities, there are also many areas of dissimilarity. Consequently, there is need for the development of an
International Standard to establish consistency between these standards to ensure the suitability of
prefabricated wood-based I-beams for structural end-use applications regardless of country of manufacture or
country of end use. It is intended that the development of this part of ISO 22389 will have value to industry,
consumers, governments and distributors.

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INTERNATIONAL STANDARD ISO 22389-1:2010(E)

Timber structures — Bending strength of I-beams —
Part 1:
Testing, evaluation and characterization
1 Scope
This part of ISO 22389 specifies the requirements for prefabricated wood-based I-beams used as structural
members in bending applications.
It gives procedures for establishing and evaluating structural capacities of prefabricated wood-based I-beams.
The capacities considered are shear, moment, stiffness, bearing, and flange tension and compression.
Procedures for establishing common details are given and certain end-use considerations specific to wood-
based I-beams are itemized.
Wood-based I-beams tested according to this part of ISO 22389 are intended for use under covered
conditions and utilize components that are able to resist the effects of moisture on structural performance due
to construction delays or other conditions of similar severity, but are not intended to be permanently exposed
to the weather.
This part of ISO 22389 is not applicable to fire performance, formaldehyde requirements and biological
durability. It does not cover manufacturing requirements for prefabricated wood-based I-beams.
NOTE Procedures set out in this part of ISO 22389 are applicable to I-beams defined by a standard or a
manufacturer's specification that includes requirements for the flanges, webs and bonding, and production controls,
including ongoing conformity assessment.
This part of ISO 22389 does not purport to address all of the safety concerns, if any, associated with its use. It
is the responsibility of the user of this part of ISO 22389 to establish appropriate safety and health practices
and determine the applicability of regulatory limitations prior to use. A specific precautionary statement is
given in 5.1.5.
2 Normative references
The following referenced documents are indispensable for the application 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 20152-1, Timber structures — Bond performance of adhesives — Part 1: Basic requirements
EN 789, Timber structures — Test methods — Determination of mechanical properties of wood based panels
ASTM D2915, Standard Practice for Evaluating Allowable Properties for Grades of Structural Lumber
ASTM D5456, Standard Specification for Evaluation of Structural Composite Lumber Products
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ISO 22389-1:2010(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
prefabricated wood-based I-beam
structural member manufactured using sawn or structural composite lumber flanges and structural panel webs,
forming an “I” cross-sectional shape, bonded together with a structural wood adhesive that possesses the
moisture resistance suitable for the conditions specified
NOTE 1 These members are primarily used as joists in floor and roof construction.
NOTE 2 Suitable moisture resistance means resistance under covered conditions and possible exposure to moisture
due to construction delays or other conditions of similar severity, but not permanent exposure to the weather.
3.2
characteristic strength and stiffness
population 5th percentile strength value at a 75 % confidence level or the 50th percentile (mean) for bending
stiffness value when determined using the test specified in this part of ISO 22389
3.3
structural composite lumber
composite of wood elements bonded with a structural wood adhesive that possesses the moisture resistance
suitable for the conditions specified and intended for structural use in dry service conditions
NOTE 1 Examples of wood elements include wood strands, strips, veneer sheets or a combination thereof.
NOTE 2 Suitable moisture resistance means resistance under covered conditions and possible exposure to moisture
due to construction delays or other conditions of similar severity, but not permanent exposure to the weather.
4 Materials
4.1 Flange stock
When the flange material is structural composite lumber, the following properties shall be determined in
accordance with ASTM D5456 or EN 789:
a) modulus of elasticity;
b) tension parallel to grain;
c) compression parallel to grain;
d) compression perpendicular to grain.
NOTE National standards or governing codes can be applicable to all flange material.
End joints in purchased flange stock are permitted, provided such joints conform to the general intent and 5.8.
4.2 Web material
Web materials covered by this part of ISO 22389 are intended for end-use conditions specified in the Scope
(third paragraph) and 3.1, Note 2.
NOTE Manufacturing or performance standards of wood-based panels recognized by national standards or
governing codes can be applicable to web materials.
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ISO 22389-1:2010(E)
4.3 Adhesives
Adhesives used to fabricate components as well as the finished products shall conform to ISO 20152-1.
NOTE National standards or governing codes can be applicable.
5 Product evaluation
5.1 General
Product evaluation shall be conducted for establishing the characteristic capacities of prefabricated
wood-based I-beams for use in building design. In addition, product evaluation shall be conducted for certain
common I-beam details since they often influence the I-beam characteristic capacities.
5.1.1 Sample size
The number of specimens specified in this part of ISO 22389 is a minimum. The use of a larger number of
1)
samples may be evaluated using ASTM D2915 or an applicable International Standard .
5.1.2 Specimens
Materials and fabrication procedures of specimens shall be as typical of intended production as can be
obtained at the time of manufacturing the specimens. Specimens shall be tested at indoor ambient laboratory
conditions, which shall be reported.
It is recommended that preliminary tests be conducted to aid the selection of representative specimens.
5.1.3 Test accuracy
Tests in accordance with this part of ISO 22389 shall be conducted in a machine or apparatus calibrated to an
error not exceeding ±2,0 %.
5.1.4 Test methods
Methods generally applicable to the full-size I-beam tests required in this part of ISO 22389 shall consider the
following:
a) the methods are applicable to both product evaluation and quality control;
b) load rate shall be as specified in the following subclauses;
c) delays between load increments are not required.
5.1.5 Test safety
All full-scale mechanical tests are potentially hazardous and appropriate safety precautions shall be observed
at all times. Appropriate lateral restraint shall be provided at all times during full-size I-beam tests to prevent
lateral buckling.

1) It is intended to develop an International Standard on the evaluation of characteristic values for structural timber.
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ISO 22389-1:2010(E)
5.2 Characteristic shear capacity
5.2.1 Characteristic shear capacity shall be established from test results obtained in accordance with this
part of ISO 22389.
5.2.2 Web factors that influence characteristic shear capacities and include web type, thickness, orientation,
grade, web to flange joint and joint type in web (machined, butted, glued or not, reinforced), shall be tested in
accordance with this subclause.
5.2.2.1 Each combination of these web factors shall be tested separately, unless the critical combination
in a proposed grouping is first established by test. Flange stiffness influences characteristic shear capacities.
5.2.2.2 If a range of flange sizes is intended to be used with a given combination of web factors, all sizes
shall be tested unless all values are intended to be based on tests with the least stiff flange.
5.2.2.3 When it is intended to group a range of species or grades of either sawn or structural composite
lumber flanges, preliminary tests shall be conducted to determine which is critical to the performance of the I-
beam.
5.2.2.4 I-beams with structural composite lumber flanges shall be tested separately from joists with sawn
lumber flanges.
5.2.3 For each web factor combination identified in 5.2.2, a minimum of 10 specimens shall be tested for
each critical joist depth. Critical joist depths are minimum and maximum product depths with approximate
102 mm depth increments in between. If the installation of specific reinforcement, as defined in the
manufacturer's handbook, is required at a certain depth to maintain product performance in the progression of
a series of depths within a combination, the product shall be tested at this depth plus the adjacent depth,
which does not require specific reinforcement.
5.2.4 Specimen length shall be that which usually produces failures in shear and shall not extend past each
bearing support by more than 6,4 mm. The bearing length shall be adequate to usually produce shear failure
instead of a bearing failure, but shall not exceed 102 mm, unless justified. There shall be a minimum
horizontal distance of 1 1/2 times the joist depth between the face of the support and the edge of the load pad.
NOTE Typical I-beam failure modes are shown in Annex B.
5.2.5 On one end of the specimen, a vertical web joint, if used, shall be located approximately 305 mm from
the face of the support or half the distance between the support and the load pad.
5.2.6 The load shall be applied to the top flange either as a single-point load at centre span or as two-point
loads of equal distance from the centre span. Load pads shall have a sufficient length to prevent local failure.
5.2.7 The load shall be applied at a uniform rate, such that anticipated failure occurs in not less than 1 min.
5.2.8 Any required web reinforcements shall be installed at supports. When required to prevent failure at a
load point, additional reinforcement shall be installed, provided such reinforcement is not wider than the load
pad.
5.2.9 Ultimate load and mode of failure shall be recorded in addition to product and test set-up descriptions.
If any specimen fails in bending, the data shall be excluded. However, for purposes of evaluating
characteristic shear capacities, bearing failure may be considered a mode of shear failure.
5.2.10 The dead load of the specimen shall be included in the ultimate load calculation, when specified by
the producer.
5.2.11 Mean ultimate shear capacities of an I-beam series or selected grouping of series shall show a linear
increase with increasing I-beam depth. A linear regression analysis of the mean values shall have a
2
coefficient of determination, r , of at least 0,9, or the specified tests of 5.2.3 shall be repeated. If the second
test set fails to meet the criteria, all depths which have been skipped shall also be tested.
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ISO 22389-1:2010(E)
5.2.11.1 Data from joist depths where failure is web buckling shall be excluded from the regression
analysis, if
a) including the results causes failure to meet the criteria of 5.2.11, or
b) the producer determines the reduction in regression line slope to be unacceptable.
In either case, all depths greater than the shallowest excluded shall be tested.
Depending on joist details and material, there is some depth where web buckling appears as a mode of failure.
Further increases in depth will result in consistent web buckling, and at some point, the ultimate shear
capacities will be reduced compared to shallower joists.
5.2.11.2 When it is intended to evaluate no more than three depths, the regression analysis is not
necessary; nevertheless, each depth shall be tested.
5.2.12 Characteristic shear capacity of the product shall be limited to that calculated by taking into account
sample size, test result variability and reduction factors. Data from tests at different joist depths included in the
regression analysis are permitted to be combined to obtain a pooled estimate of variability.
5.2.12.1 When combining data, the mean shear capacity, P , for depth, d, shall be calculated using
e i
Equation (1):
PA=+Bd (1)
ei
where A and B are intercept and slope of Equation (1), respectively.
5.2.12.2 Where too few depths are involved for correlation in 5.2.11, the tests fail the regression criteria, or
depths are excluded from the correlation, test data shall not be combined and each such depth shall be
evaluated separately.
5.2.12.3 The coefficient of variation, C , of each individual depth tested shall be calculated using
V,i
Equation (2):
S
i
C = (2)
V,i
P
i
where P and S are the mean and standard deviation of the data from each depth tested, respectively.
i
i
The coefficient of variation of the combined data sets, C , shall be calculated using Equation (3):
V
J
2
[(nC−1) ]
∑ i
,
V i
i=1
C = (3)
V
J
nJ−
∑ i
i=1
where
n is the number of tests for each depth, d , tested and included in the regression analysis;
i i
J is the number of depths included in the regression analysis.
Also, the summation is from i = 1 to J.
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ISO 22389-1:2010(E)
5.2.12.4 The characteristic shear capacity, P , shall be calculated using Equation (4):
s
P=−PK×C×P (4)
se e
V
where
K is the factor for 5th percentile with 75 % confidence for a normal distribution [from ASTM D2915 or
1)
an applicable International Standard ];
P is the ultimate mean shear capacity from Equation (1) or the mean of any depth in accordance with
e
5.2.12.2;
C is the coefficient of variation of combined data from Equation (3) or Equation (2), when any depth is
V
evaluated alone.
J
5.2.12.5 When data are combined, the factor, K, shall be based on a sample size N = nJ− . When the
∑ i
i=1
criteria of 5.2.11 are not met and for depths excluded from the regression analysis, the characteristic shear
capacity, P , shall be computed separately for each such depth using Equation (5):
s
P=−()PK×C ×P (5)
ii
s ,
V i
where the factor K shall be based on a sample size of n .
i
5.3 Characteristic bearing capacity
5.3.1 General
5.3.1.1 This subclause provides procedures for establishing the characteristic bearing capacities of
prefabricated wood-based I-beams. This subclause does not preclude the development of alternative
characteristic bearing capacity evaluation procedures meeting the intent of this part of ISO 22389. If required
by national standards or governing codes, documentation showing equivalency to each of the evaluation
requirements in this subclause shall be provided.
NOTE This subclause was developed in the light of manufactured products, produced from materials defined in
Clause 4. New materials can require new or revised procedures to provide comparable levels of safety and performance.
5.3.1.2 Factors that influence characteristic I-beam bearing capacities, including bearing length, web
(type, orientation, thickness and grade), rout geometry, adhesive type, joist depth, flange (type, size, species
and grade), and web stiffeners (see 5.3.7), shall be tested in accordance with this subclause.
5.3.1.2.1 Each combination of these factors shall be tested separately according to 5.3.1.4, unless the
critical combination is first established by test.
5.3.1.2.2 Joists with structural composite lumber flanges shall be tested and analysed separately from
joists with sawn lumber flanges.
5.3.1.3 Testing for both end and intermediate bearing capacities shall be undertaken and analysed as
independent test programmes.
5.3.1.4 The minimum sample size for either an end or intermediate bearing capacity evaluation
programme shall be 40 for a series of I-beams with the same materials except for the joist depth. The test
specimens shall be evenly divided into groups which represent the extremes of bearing length and joist depth
for evaluation. Extrapolation beyond the tested extremes of bearing length and joist depth shall not be
permitted. Bearing lengths less than 38 mm are not recommended due to concerns regarding construction
tolerances and building code requirements.
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ISO 22389-1:2010(E)
5.3.1.5 End and intermediate bearing capacity evaluations shall follow either the “default” or
“regression-based” procedures. Any data set that does not support the minimum coefficient of determination,
2
r , requirement for a “regression-based” evaluation shall be re-analysed as a “default” evaluation.
5.3.1.5.1 A “default” evaluation shall be conducted by testing independent groups at the extremes of
bearing length and joist depth intended to be evaluated. Additional test groups may be added to the
programme, provided the minimum sample size in each additional group is 10 and the minimum sample size
for the entire I-beam series is 40. Each group shall be analysed independently to determine a characteristic
value using the procedures of 5.3.4.
NOTE The following represent typical default test programmes that would meet the minimum sampling criteria to
evaluate a joist series for end or intermediate bearing capacities:
a) four test groups with n = 10 at the extremes of bearing length and depth to evaluate a range for both variables;
b) two test groups with n = 20, when one bearing length is evaluated for a range of depths;
c) one test group with n = 40, when only a single bearing length and depth are evaluated.
5.3.1.5.2 In a “regression-based” evaluation, the characteristic I-beam bearing capacity shall be a linear
function of bearing length. As a minimum, the test programme shall include the shallowest and deepest joist
depths that can be evaluated. At least three evenly spaced increments of bearing length shall be evaluated for
2
each joist depth tested. Provided the resulting regressions maintain a minimum coefficient of determination, r ,
of 0,9 for each joist depth, they may be reduced to a characteristic value using the procedures of 5.3.5. If
the regressions do not comply with this requirement, a “default” evaluation shall be conducted in accordance
with 5.3.4.
A typical regression-based test programme to establish end or intermediate bearing capacity shall consist of
six groups with n = 7 for each group. A minimum of three bearing lengths shall be tested at the maximum and
minimum joist depths that can be evaluated. The data for each depth shall be combined using a linear
regression to define the bearing strength as a function of bearing length at the extreme depths.
5.3.2 Test methods
5.3.2.1 End bearing
For end bearing, specimens shall be tested according to either Figure 1 or 2. The test span shall be that which
usually produces end bearing failures. In Figure 1, a single concentrated load shall be placed off-centre
toward the test bearing. In Figure 2, the load shall be applied at the centre of the test span as either a single
concentrated load, as shown, or as two-point loads placed symmetrically about the centre of the test span. For
both Figures 1 and 2, the applied load shall have a clear distance of at least 1 1/2 times the joist depth, d,
between the inside face of bearing and the edge of the load pad. The load shall be applied via a steel load
pad at a uniform rate, such that anticipated failure does not occur in less than 1 min. Bearings shall consist of
steel blocks representing the tested end bearing length. The load pad shall be of sufficient length to prevent
local failure under the load point. Additional reinforcement may be installed, when required, to prevent failure
at a load point or non-test bearing. Such reinforcement shall not be wider than the length of the load pad or
bearing surface. Load cells shall record the test bearing, but half the total applied load shall be appropriate for
the set-up shown in Figure 2. Perforated knockouts (38 mm maximum diameter) shall be randomly located
within the joist specimen, as they would occur in application. Web-to-web joints may be randomly located
when characteristic shear capacity is evaluated using an independent test programme. Otherwise, a web joint
shall be positioned at the mid-point between the edge of the load and bearing plates.
NOTE Figure 1 allows for one overhang no longer than half of the test span. This set-up allows the joist to be turned
end-for-end to perform a second test, with the failed end as the overhang for the second test. Figure 2 allows for only one
test per specimen.
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ISO 22389-1:2010(E)

Key
d I-joist depth
F applied load
a
Test reaction.
b
Non-test reaction.
NOTE Non-symmetric set-up allows for two end bearing tests per specimen.
Figure 1 — End bearing test set-up

Key
d I-joist depth
F applied load
a
Test reaction.
NOTE Symmetric set-up allows for one end bearing test per specimen.
Figure 2 — End bearing test set-up
5.3.2.2 Intermediate bearing
Specimens shall be tested according to either Figure 3 or 4. The test span(s) shall be that which usually
produces intermediate bearing failures. In Figure 3, the load shall be applied at the centre of the test span
through a steel load pad representing the tested intermediate bearing length. In Figure 4, the loads shall be
applied symmetrically about the test bearing through steel load pads of sufficient length to prevent local failure
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ISO 22389-1:2010(E)
under load points. For both Figures 3 and 4, the applied load(s) shall have a clear distance
...