Bsi bs en 00408 2010 + a1 2012

BS EN 408:2010+A1:2012
BS EN 408:2010

BSI Standards Publication

Timber structures — Structural
timber and glued laminated
timber — Determination of
some physical and mechanical
properties

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BS EN 408:2010+A1:2012

BRITISH STANDARD


Text affected
30 September 2012

Implementation of CEN amendment A1:2012


EN 408:2010+A1

EUROPEAN STANDARD
NORME EUROPÉENNE

EUROPÄISCHE NORM

July 2012

ICS 91.080.20; 79.040; 79.060.99

English Version

Timber structures - Structural timber and glued laminated timber
- Determination of some physical and mechanical properties
Structures en bois - Bois de structure et bois lamellé-collé Détermination de certaines propriétés physiques et
mécaniques

Holzbauwerke - Bauholz für tragende Zwecke und
Brettschichtholz - Bestimmung einiger physikalischer und
mechanischer Eigenschaften

This European Standard was approved by CEN on 16 June 2012.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION

COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2012 CEN

All rights of exploitation in any form and by any means reserved
worldwide for CEN national Members.

Ref. No. EN 408:2010+A1:2012: E


BS EN 408:2010:+A1:2012
EN 408:2010+A1:2012
EN
408:2010+A1:2012 (E)
(E)

Contents

Page

Foreword ..............................................................................................................................................................4 
Introduction .........................................................................................................................................................5
1

Scope ......................................................................................................................................................6 

2

Normative references ............................................................................................................................6 

3

Terms and definitions ...........................................................................................................................6

4

Symbols and abbreviations ..................................................................................................................6

5

Determination of dimensions of test pieces .......................................................................................8

6

Determination of moisture content of test pieces ..............................................................................8

7

Determination of density of test pieces ..............................................................................................8

8

Conditioning of test pieces ...................................................................................................................8

9
9.1
9.2

9.3

Determination of local modulus of elasticity in bending ...................................................................9
Test piece ...............................................................................................................................................9 
Procedure ...............................................................................................................................................9 
Expression of results ......................................................................................................................... 10

10
10.1
10.2
10.3

Determination of global modulus of elasticity in bending ............................................................. 11
Test piece ............................................................................................................................................ 11 
Procedure ............................................................................................................................................ 11 
Expression of results ......................................................................................................................... 12 

11
11.1
11.1.1
11.1.2
11.1.3
11.2
11.2.1
11.2.2
11.2.3

Determination of the shear modulus ................................................................................................ 13
Torsion method ................................................................................................................................... 13
Test piece ............................................................................................................................................ 13 

Procedure ............................................................................................................................................ 13 
Expression of results ......................................................................................................................... 16 
Shear field test method ...................................................................................................................... 17
Test piece ............................................................................................................................................ 17 
Procedure ............................................................................................................................................ 17 
Expression of results ......................................................................................................................... 19 

12
12.1
12.2
12.3

Determination of modulus of elasticity in tension parallel to the grain ........................................ 19 
Test piece ............................................................................................................................................ 19 
Procedure ............................................................................................................................................ 19 
Expression of results ......................................................................................................................... 20 

13
13.1
13.2
13.3

Determination of tension strength parallel to the grain.................................................................. 20
Test piece ............................................................................................................................................ 20 
Procedure ............................................................................................................................................ 21 
Expression of results ......................................................................................................................... 21 

14
14.1
14.2

14.3

Determination of modulus of elasticity in compression parallel to the grain .............................. 21 
Test piece ............................................................................................................................................ 21 
Procedure ............................................................................................................................................ 22 
Expression of results ......................................................................................................................... 22 

15
15.1
15.2
15.3

Determination of compression strength parallel to grain .............................................................. 22
Test piece ............................................................................................................................................ 22 
Procedure ............................................................................................................................................ 22 
Expression of results ......................................................................................................................... 23 

16
16.1

Determination of tension and compression strengths perpendicular to the grain ..................... 23
Requirements for test pieces ............................................................................................................ 23

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16.1.1
16.1.2
16.2
16.3
16.3.1
16.3.2

Fabrication ........................................................................................................................................... 23 
Surface preparation............................................................................................................................. 23 
Procedure ............................................................................................................................................. 24 
Expression of results .......................................................................................................................... 27 
Compression perpendicular to the grain .......................................................................................... 27
Tension perpendicular to the grain ................................................................................................... 27

17
17.1
17.2
17.3
17.3.1
17.3.2

Determination of modulus of elasticity perpendicular to the grain ............................................... 27
Requirements for test pieces ............................................................................................................. 27
Procedure ............................................................................................................................................. 27 
Expression of results .......................................................................................................................... 28 
Compression perpendicular to the grain .......................................................................................... 28
Tension perpendicular to the grain ................................................................................................... 28

18
18.1
18.1.1
18.1.2
18.2
18.3

Determination of shear strength parallel to the grain ..................................................................... 29
Requirements for test pieces ............................................................................................................. 29
Fabrication ........................................................................................................................................... 29 
Surface preparation............................................................................................................................. 29 
Procedure ............................................................................................................................................. 30 
Expression of results .......................................................................................................................... 31 

19
19.1
19.2
19.3

Bending strength parallel to grain ..................................................................................................... 32
Test piece ............................................................................................................................................. 32 
Procedure ............................................................................................................................................. 32 
Expression of results .......................................................................................................................... 33 

20
20.1
20.2
20.3
20.4

Test report ............................................................................................................................................ 34 
General ................................................................................................................................................. 34 
Test piece ............................................................................................................................................. 34 
Test method ......................................................................................................................................... 34
Test results .......................................................................................................................................... 34 

Annex A (informative) Example of compression perpendicular to grain test arrangement .................... 35 
Annex B (informative) Example of tension perpendicular to grain test arrangement with rigid
fixings ................................................................................................................................................... 37 
Bibliography ...................................................................................................................................................... 38 

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BS EN 408:2010:+A1:2012
EN 408:2010+A1:2012
EN
408:2010+A1:2012 (E)
(E)

Foreword
This document (EN 408:2010+A1:2012) has been prepared by Technical Committee CEN/TC 124 “Timber
structures”, the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by January 2013, and conflicting national standards shall be withdrawn at
the latest by January 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document includes Amendment 1 approved by CEN on 16 June 2012.
The start and finish of text introduced or altered by amendment is indicated in the text by tags !".

This document supersedes !EN 408:2010."
In this revised standard a new test is added for the determination of the shear modulus.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

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BS EN 408:2010:+A1:2012
EN
EN 408:2010+A1:2012
408:2010+A1:2012 (E)
(E)

Introduction
This 2010 revision replaces the test for the determination of the shear strength parallel to grain.
The revised edition of 2003 added a global bending modulus of elasticity, whilst renaming the existing test as
the local modulus of elasticity. It also includes the methods for determination of shear strength and
mechanical properties perpendicular to the grain, previously given in EN 1193, which has now been withdrawn.
The values obtained in any determination of the properties of timber depend upon the test methods used. It is
therefore desirable that these methods be standardized so that results from different test centres can be
correlated. Moreover, with the adoption of limit state design and with the development of both visual and
machine stress grading, attention will be increasingly centred on the determination and monitoring of the
strength properties and variability of timber in structural sizes. Again, this can be more effectively undertaken if
the basic data are defined and obtained under the same conditions.
This European Standard, which is based originally on ISO 8375, specifies laboratory methods for the
determination of some physical and mechanical properties of timber in structural sizes. The methods are not

intended for the grading of timber or for quality control.
For the determination of shear modulus, alternative methods have been specified. The choice of which to use
will depend upon the objective of the investigation and, to some extent, on the equipment available. Following
testing to this standard it is intended that the determination of characteristic values will normally be obtained
according to procedures specified in other European Standards.
Attention is drawn to the advantages that may be gained, often with little extra effort, in extending the
usefulness of test results by recording additional information on the growth characteristics of the pieces that
are tested, particularly at the fracture sections. Generally, such additional information should include gradedetermining features such as knots, slope of grain, rate of growth, wane, etc., on which visual grading rules
are based, and strength indicating parameters such as localized modulus of elasticity, on which some
machine stress grading is based.

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BS EN 408:2010:+A1:2012
EN 408:2010+A1:2012
EN
408:2010+A1:2012 (E)
(E)

1

Scope

This European Standard specifies test methods for determining the following properties of structural timber
and glued laminated timber: modulus of elasticity in bending; shear modulus; bending strength; modulus of
elasticity in tension parallel to the grain; tension strength parallel to the grain; modulus of elasticity in
compression parallel to the grain; compression strength parallel to the grain; modulus of elasticity in tension
perpendicular to the grain; tension strength perpendicular to the grain; modulus of elasticity in compression
perpendicular to the grain; compression strength perpendicular to the grain and shear strength.

In addition, the determination of dimensions, moisture content, and density of test pieces are specified.
The methods apply to rectangular and circular shapes (of substantially constant cross section) of solid
unjointed timber or finger-jointed timber and glued laminated timber unless stated otherwise.

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.
!EN 384:2010, Structural timber — Determination of characteristic values of mechanical properties and
density"
EN 13183-1, Moisture content of a piece of sawn timber ― Part 1: Determination by oven dry method

3

Terms and definitions

Not applicable.

4

Symbols and abbreviations

A

cross-sectional area, in square millimetres;

a

distance between a loading position and the nearest support in a bending test, in millimetres;

b

width of cross section in a bending test, or the smaller dimension of the cross section, in
millimetres;

Ec,0

modulus of elasticity in compression parallel to the grain, in newtons per square millimetre;

Ec,90

modulus of elasticity in compression perpendicular to the grain, in newtons per square millimetre;

Em,g

global modulus of elasticity in bending, in newtons per square millimetre;

Em,l

local modulus of elasticity in bending, in newtons per square millimetre;

Et,0

modulus of elasticity in tension parallel to the grain, in newtons per square millimetre;

Et,90

modulus of elasticity in tension perpendicular to the grain, in newtons per square millimetre;

F

load, in newtons;

Fc,90

compressive load perpendicular to the grain, in newtons;

Fc,90,max

maximum compressive load perpendicular to the grain, in newtons;

Fc,90,max,est

estimated maximum compressive load perpendicular to the grain, in newtons;

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EN 408:2010+A1:2012
408:2010+A1:2012 (E)
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Fmax

maximum load, in newtons;

Fmax,est

estimated maximum load, in newtons;

Ft,90

tensile load perpendicular to the grain, in newtons;

Ft,90,max

maximum tensile load perpendicular to the grain, in newtons;

G

shear modulus, in newtons per square millimetre;

S

first moment of area, in millimetres to the third power;

fc,0

compressive strength parallel to the grain, in newtons per square millimetre;

fc,90

compressive strength perpendicular to the grain, in newtons per square millimetre;

fm

bending strength, in newtons per square millimetre;

ft,0

tensile strength parallel to the grain, in newtons per square millimetre;

ft,90

tensile strength perpendicular to the grain, in newtons per square millimetre;

fv

shear strength parallel to the grain, in newtons per square millimetre;

fv,k

characteristic shear strength parallel to the grain, in newtons per square millimetre;

G

shear modulus, in newtons per square millimetre;

Gtor,t

shear modulus in torsion, in newtons per square millimetre;

Gtor,s

shear modulus in shear field, in newtons per square millimetre;

h

depth of cross section in a bending test, or the larger dimension of the cross section, or the test
piece height in perpendicular to grain and shear tests, in millimetres;

h0

gauge length, in millimetres;

I

second moment of area, in millimetres to the fourth power;

K, k

coefficients;

kG

coefficient for shear modulus;

ktor

torque stiffness, in newton metres per radian;

ks

shear stiffness;

l

span in bending, or length of test piece between the testing machine grips in compression and
tension, in millimetres;

l1

gauge length for the determination of modulus of elasticity or shear modulus, in millimetres;

l2

distance between the supports and gauge length in torsion, in millimetres;

t

plate thickness, in millimetres;

Tr

torque, in newton millimetres;

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408:2010+A1:2012 (E)
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Vs

shear force, in newtons;

W

section modulus, in millimetres to the third power;

w

deformation or displacement, in millimetres;

ϕ

rotation, in radians;

χ, η

shape factors.

Suffixes
1, 2

5

refer to loads or deformations or pieces at particular points of a test and are referred to as
necessary in the text.

Determination of dimensions of test pieces

The dimensions of the test piece shall be measured to an accuracy of 1 %. All measurements shall be made
when the test pieces are conditioned as specified in Clause 8. If the width or thickness varies within a test
piece, these dimensions should be recorded as the average of three separate measurements taken at
different positions on the length of each piece.
The measurements shall not be taken closer than 150 mm to the ends.
Specimens for perpendicular to grain tests shall be planed.

6

Determination of moisture content of test pieces

The moisture content of the test piece shall be determined in accordance with EN 13183-1 on a section taken
from the test piece. For structural timber the section shall be of full cross section, free from knots and resin
pockets. For perpendicular to grain test specimens the moisture content shall be determined from the whole
specimen.
In strength tests for bending and tension parallel to grain and compression parallel to grain, the section shall
be cut as close as possible to the fracture.

7

Determination of density of test pieces

The density of the whole cross section of the test piece shall be determined on a section taken from the test
piece. For structural timber the section shall be of full cross section, free from knots and resin pockets.
In strength tests, the section shall be cut as close as possible to the fracture.
For perpendicular to grain test specimens the density of the test pieces shall be determined prior to test after
conditioning from the measurements of mass and volume of the whole test piece.

8

Conditioning of test pieces

All tests shall be carried out on pieces, which are conditioned at the standard environment of (20 ± 2) °C and
(65 ± 5) % relative humidity. A test piece is conditioned when it attains constant mass. Constant mass is
considered to be attained when the results of two successive weightings, carried out at an interval of 6 h, do
not differ by more than 0,1 % of the mass of the test piece.
Where the timber to be tested is not readily conditioned to the above standard environment (e.g. for
hardwoods with high densities) that fact shall be reported.

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EN
EN 408:2010+A1:2012
408:2010+A1:2012 (E)
(E)

For small specimens, unless otherwise protected, test pieces shall not be removed from the conditioning
environment more than 1 h before testing.
Test pieces can be stored in the test area for up to 24 h provided they are close piled and wrapped in vapour
tight sheeting.

9

Determination of local modulus of elasticity in bending

9.1 Test piece
The test piece shall have a minimum length of 19 times the depth of the section. Where this is not possible,
the span of the beam shall be reported.

9.2 Procedure
The test piece shall be symmetrically loaded in bending at two points over a span of 18 times the depth as
shown in Figure 1. If the test piece and equipment do not permit these conditions to be achieved exactly, the
distance between the load points and the supports may be changed by an amount not greater than 1,5 times
the piece depth, and the span and test piece length may be changed by an amount not greater than three
times the piece depth, while maintaining the symmetry of the test.
The test piece shall be simply supported.
Small steel plates of length not greater than one-half of the depth of the test piece may be inserted between
the piece and the loading heads or supports to minimize local indentation.
Lateral restraint shall be provided as necessary to prevent lateral torsional buckling. This restraint shall permit
the piece to deflect without significant frictional resistance.
Load shall be applied at a constant rate. The rate of movement of the loading head shall be not greater than
(0,003 h) mm/s (see Figure 1).
The maximum load applied shall not exceed 0,4 Fmax,est.
The estimated maximum load, Fmax,est of the material under test shall be obtained either from tests on a least
ten pieces of the appropriate species, size and grade or from appropriate existing test data.

Figure 1 — Test arrangement for measuring local modulus of elasticity in bending

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The loading equipment used shall be capable of measuring the load to an accuracy of 1 % of the load applied

to the test piece or, for loads less than 10 % of the applied maximum load, with an accuracy of 0,1 % of the
maximum applied load.
The deformation w shall be taken as the average of measurements on both side faces at the neutral axis, and
shall be measured at the centre of a central gauge length of five times the depth of the section.
The measuring equipment used shall be capable of measuring deformation to an accuracy of 1 % or, for
deformations less than 2 mm, with an accuracy of 0,02 mm.

9.3 Expression of results
Using data obtained from the local modulus of elasticity test, plot the load/deformation graph.
Use that section of the graph between 0,1 Fmax,est and 0,4 Fmax,est for a regression analysis.
Find the longest portion of this section that gives a correlation coefficient of 0,99 or better. Provided that this
portion covers at least the range 0,2 Fmax,est to 0,3 Fmax,est calculate the local modulus of elasticity from the
following expression:

Em,l =

al12 (F2 − F1 )
16 I (w2 − w1 )

(1)

where
F2 − F1

is an increment of load in newtons on the regression line with a correlation coefficient of
0,99 or better; and

w2 − w1 is the increment of deformation in millimetres corresponding to F2 − F1 (see Figure 2).
The local modulus of elasticity, Em,l shall be calculated to an accuracy of 1 %.
If a portion of the graph cannot be found with a correlation coefficient of 0,99 or better covering the range

0,2 Fmax,est to 0,3 Fmax,est, check the test equipment and take measures to eradicate any errors caused by
distorted specimens. If 0,99 is still not achieved, discard the specimen.
The modulus of elasticity shall be calculated to an accuracy of 1 %.

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EN 408:2010+A1:2012
408:2010+A1:2012 (E)
(E)

Key
F

load

w

deformation
Figure 2 — Load-deformation graph within the range of elastic deformation

10 Determination of global modulus of elasticity in bending
10.1

Test piece

The test piece shall have a minimum length of 19 times the depth of the section. Where this is not possible,
the span of the beam shall be reported.

10.2

Procedure

The test piece shall be symmetrically loaded in bending at two points over a span of 18 times the depth as
shown in Figure 3. If the test piece and equipment do not permit these conditions to be achieved exactly, the
distance between the load points and the supports may be changed by an amount not greater than 1,5 times
the piece depth, and the span and test piece length may be changed by an amount not greater than three
times the piece depth, while maintaining the symmetry of the test.
The test piece shall be simply supported.
Small steel plates of length not greater than one-half of the depth of the test piece may be inserted between
the piece and the loading heads or supports to minimize local indentation.
Lateral restraint shall be provided as necessary to prevent lateral (torsional) buckling. This restraint shall
permit the piece to deflect without significant frictional resistance.

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EN 408:2010+A1:2012
EN
408:2010+A1:2012 (E)
(E)

Load shall be applied at a constant rate. The rate of movement of the loading head shall be not greater than
(0,003 h) mm/s (see Figure 3).
The maximum load applied shall not exceed 0,4 Fmax,est or cause damage to the piece unless this test is
carried out in conjunction with Clause 19.
The estimated maximum load, Fmax,est of the material under test shall be obtained either from tests on at least

ten pieces of the appropriate species, size and grade or from appropriate existing test data.

Figure 3 — Test arrangement for measuring global modulus of elasticity in bending
The loading equipment used shall be capable of measuring the load to an accuracy of 1 % of the load applied
to the test piece or, for loads less than 10 % of the applied maximum load, with an accuracy of 0,1 % of the
maximum applied load.
The deformation w shall be measured at the centre of the span and from the centre of the tension or
compression edge. When w is measured at the neutral axis it shall be the mean of measurements made on
both sides of the test piece.
Deformations shall be determined with an accuracy of 1 % or, for deformations less than 2 mm, with an
accuracy of 0,02 mm.
If the test configuration differs from the above in any way then these differences are recorded and adjustment
factors are determined.
NOTE
The deformation w includes any local indentations that might occur at the supports and loading points and
deformation of the supports themselves.

Alternative determination methods based on the dynamic modulus of elasticity are allowed provided the
correlation between the measured dynamic modulus of elasticity and the global modulus of elasticity is well
established and documented.

10.3

Expression of results

Use that section of the graph between 0,1 Fmax,est and 0,4 Fmax,est for a regression analysis.

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EN 408:2010+A1:2012
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Find the longest portion of this section that gives a correlation coefficient of 0,99 or better. Provided that this
portion covers at least the range 0,2 Fmax,est to 0,3 Fmax,est, calculate the global modulus of elasticity, Em,g from
the following expression:

E m,g =

3al 2 − 4a 3
3

w − w1
6a 

2bh  2 2
−
 F2 − F1 5Gbh 

(2)

where
!F2 - F1 is an increment of load in newtons on the regression line with a correlation coefficient of 0,99 or
better
and
w2 - w1 is the increment of deformation corresponding to F2 -F1, in millimetres (see Figure 2).
G

is the shear modulus determined either by the method given in 11.1 or 11.2.

The shear modulus G shall be taken as infinite when Equation (2) is used for the EN 384 strength class
allocation procedure.
NOTE
Equation (2) accounts for the influence of the shear deformation. The strength class allocation procedure in
EN 384:2010, 5.3.2 includes a normative transformation equation accounting implicitly for the shear deformation. For that
case the shear influence as given in Equation (2) can be ignored by taking G as infinitive. However, Equation (2) offers the
option to study and evaluate the shear influence for other purposes when the shear modulus is known. The mean shear
2
modulus of coniferous wood species can be taken as G = 650 N/mm . It is advised to report both results with and without
the shear deformation correction."

11 Determination of the shear modulus
11.1 Torsion method
11.1.1 Test piece
The test piece shall be of rectangular cross-section and have a testing length of at least 19 times the largest
cross-sectional dimension.
NOTE 1
The method also applies to test pieces with non-rectangular cross-section provided appropriate modified
equation coefficients are applied.
NOTE 2

This method is particularly suitable for sawn timber beams.

11.1.2 Procedure
The test piece is clamped at the supports, which are spaced more than 16 times the largest cross-sectional
dimension and subjected to torsion along the longitudinal axis by a relative rotation of the supports, see
Figure 4. The test piece shall be mounted such as to minimize the bending deflection caused by the self

weight. The centres of the supports are in line such that clamping the test piece will not cause any
deformation that could influence the torsion results. The torque is applied by rotation of one or both supports.
NOTE 1 In order to avoid additional bending stresses caused by the self weight especially when testing thin specimens,
the starting position of such specimens should be edge wise.
NOTE 2

The torque can be applied in different ways.

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408:2010+A1:2012 (E)
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The relative rotation of two cross-sections, 1 and 2 (see Figure 4) spaced within the free testing length, l1 is
measured in addition to the torque. The distance between the support and these cross-sections, l2 should be
at least two times and at maximum three times the thickness.
The torque is applied such that the relative rotation rate per time increment, dϕ/dt is:
f v,k χ  l1 
dϕ
=
 
dt 225Gη  h 

(3)

where

χ and η are given in Table 1.
Examples of the gauges that enable the rotation measurements are shown in Figure 5.
The relation between the applied torque,Tr and the relative rotation, ϕ represented by the torque stiffness, ktor
is determined using a linear regression equation as shown in Figure 6. A linear elastic portion of the graph is
taken for linear regression analyses. The correlation coefficient should be at least 0,98.

Figure 4 — Example of test setup with requirements of specific locations for the gauges

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Figure 5 — Example of test setup

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Key

Tr

torque

ϕi

rotation at cross-section i

k tor torque stiffness
Figure 6 — Torque versus relative rotation
The maximum torque applied should be reached within 150 s and shall not exceed the proportional limit or
cause damage to the piece between the cross-sections 1 and 2. For this reason the torque is limited to:
Tr =

2 2
b h f v ,k χ
3

(4)

where

χ is the value taken from Table 1.
The loading equipment used shall be capable of measuring the torque to an accuracy of 1 % of the torque
applied to the test piece or, for loads less than 10 % of the maximum applied torque, with an accuracy of
0,1 % of the maximum applied torque.
11.1.3 Expression of results
The shear modulus Gtor is given by the equation:
Gtor =

where

16

ktor

η h b3

l1

(5)


BS EN 408:2010:+A1:2012
EN
EN 408:2010+A1:2012
408:2010+A1:2012 (E)
(E)

η

is the shape factor according to Table 1.
Table 1 — Shape factor values for torsion test

h/b

1,0

1,2

1,5

2,0

2,5

3

4

5

10

η

0,140 6

0,166

0,196

0,229

0,249

0,263

0,281

0,291

0,312

χ

0,415 8

0,456 4

0,461 8

0,490 4

0,516 2

0,533 4

0,563 4

0,596 0

0,627 0

11.2 Shear field test method
11.2.1 Test piece
The test piece shall have a minimum length of 19 times the depth of the section. Where this is not possible,
the span of the beam shall be reported.
NOTE 1

This method is particularly suitable for laminated members.

NOTE 2 This method may be applied together with the determination of the bending strength and global modulus of
elasticity.

11.2.2 Procedure
The test piece shall be symmetrically loaded in bending at two points over a span of 18 times the depth as
shown in Figure 7. If the test piece and equipment do not permit these conditions to be achieved exactly, the
distance between the load points and the supports may be changed by an amount not greater than 1,5 times
the piece depth, and the span and test piece length may be changed by an amount not greater than three
times the piece depth, while maintaining the symmetry of the test.
The test piece shall be simply supported.
NOTE
Small steel plates of length not greater than one-half of the depth of the test piece may be inserted between
the piece and the loading heads or supports to minimize local indentation.

Figure 7 — Test arrangement for shear field test

17


BS EN 408:2010:+A1:2012
EN 408:2010+A1:2012
EN
408:2010+A1:2012 (E)
(E)

Lateral restraint shall be provided as necessary to prevent lateral (torsional) buckling. This restraint shall
permit the piece to deflect without significant frictional resistance.
Load shall be applied at a constant rate. The rate of movement of the loading head shall be not greater than

(0,003 h) mm/s.
The maximum load applied shall not exceed 0,4 Fmax,est or cause damage to the piece unless 11.2.1, Note 2
applies.
The estimated maximum load, Fmax,est of the material under test shall be obtained either from tests on at least
ten pieces of the appropriate species, size and grade or from appropriate existing test data.
The loading equipment requirements correspond with 10.2.
In the middle of the area under constant shear stress, a square is marked on both side faces, placed
symmetrically with respect to the height of the test piece. A device that measures the change of the square
diagonals is fixed to the test piece at the square corners, see Figure 8.

Figure 8 — Example of the shear field test apparatus fixed on one of both sides
Deformations shall be determined with an accuracy of 1 % or, for deformations less than 2 mm, with an
accuracy of 0,02 mm.
The shear force applied shall not exceed the proportional limit unless 11.2.1, Note 2 applies.
The loading equipment used shall be capable of measuring the shear force to an accuracy of 1 % of the shear
force applied to the test piece or, for loads less than 10 % of the maximum applied shear force, with an
accuracy of 0,1 % of the maximum applied shear force.
The shear deformation, ws is defined as the mean value of the summation of the absolute readings of both
diagonals at each side face of the cross-section, see Figure 9.

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BS EN 408:2010:+A1:2012
EN
EN 408:2010+A1:2012
408:2010+A1:2012 (E)
(E)

Figure 9 — Deformation of the square with diagonals

11.2.3 Expression of results
For beams with rectangular cross-section the shear modulus, Gtor,s is given by the equation:

G tor,s = α

h0 (Vs, 2 − Vs ,1 )
bh (w2 − w1 )

(6)

where

α=

2
3 h0
− 2
2 4h

wi =

(w

i ,1

(7)

+ wi ,2
2

)

with i = 1, 2

(8)

wi

is the mean deformation of both diagonals i on opposite side faces of the beam for a
given shear load Vs,i, in millimetres;

Vs,2 − Vs,1

is the shear load increment, in newtons.

For non rectangular cross-section structural engineering principles apply.

12 Determination of modulus of elasticity in tension parallel to the grain
12.1

Test piece

The test piece shall be of full structural cross section, and of sufficient length to provide a test length clear of
the testing machine grips of at least nine times the larger cross-sectional dimension.

12.2

Procedure

The test piece shall be loaded using gripping devices which will permit as far as possible the application of a

tensile load without inducing bending. The gripping devices and loading conditions actually used shall be
reported.
Load shall be applied at a constant rate. The rate of strain in the piece shall be not greater than 0,000 05/s.

19


BS EN 408:2010:+A1:2012
EN 408:2010+A1:2012
EN
408:2010+A1:2012 (E)
(E)

The maximum load applied shall not exceed the proportional limit load or cause damage to the test piece,
unless this test is carried out in conjunction with Clause 13. If significant movement occurs, for example with
wedge type grips, preliminary tests may be needed to establish a rate of movement of the machine crosshead.
The loading equipment used shall be capable of measuring the load to an accuracy of 1 % of the load applied
to the test piece or, for loads less than 10 % of the applied maximum load, with an accuracy of 0,1 % of the
maximum applied load.
Deformation shall be measured over a length of five times the width of the piece, located not closer to the
ends of the grips than twice this width. Two extensometers shall be used, and shall be positioned to minimize
the effects of distortion.
Deformations shall be determined with an accuracy of 1 % or for deformations less than 2 mm, with an
accuracy of 0,02 mm.

12.3

Expression of results

The modulus of elasticity in tension Et,0 is given by the equation

E t,0 =

l 1 (F2 − F1 )
A(w2 − w1 )

(9)

where
F2 - F1 is an increment of load on the straight line portion of the load deformation curve, in newtons
(see Figure 2);
w2 − w1 is the increment of deformation corresponding to F2 − F1, in millimetres (see Figure 2).
The other symbols are as given in Clause 4.
If E t ,0 is calculated from a load/deformation linear regression the correlation coefficient should be greater than
0,99.
The modulus of elasticity in tension shall be calculated to an accuracy of 1 %.

13 Determination of tension strength parallel to the grain
13.1

Test piece

The test piece shall be of full structural cross section, and of sufficient length to provide a test length clear of
the testing machine grips of at least nine times the larger cross-sectional dimension.
For tensile parallel top grain finger joint tests the joint shall be located at centre span. The test length clear of
machine grips is at least nine times the smallest cross-sectional dimension, see Figure 10.

20


BS EN 408:2010:+A1:2012

EN
EN 408:2010+A1:2012
408:2010+A1:2012 (E)
(E)

Figure 10 — Test setup tensile strength parallel to grain

13.2

Procedure

The test piece shall be loaded using gripping devices which will permit as far as possible the application of a
tensile load without inducing bending. The gripping devices and loading conditions actually used shall be
reported.
The loading equipment used shall be capable of measuring the load to an accuracy of 1 % of the load applied
to the test piece.
Load shall be applied at a constant loading-head movement so adjusted that maximum load is reached within
(300 ± 120) s.
NOTE
This rate should be determined from the results of preliminary tests. The objective is that the time to reach
Fmax for each piece is 300 s.

The time to failure for each test piece shall be recorded and its average reported. Any single piece diverging
more than 120 s from the target of 300 s shall be reported.

13.3

Expression of results

The tensile strength ft,0 is given by the equation

f t,o =

Fmax
A

(10)

The symbols are as given in Clause 4.
The tensile strength, ft,0 shall be calculated to an accuracy of 1 %.
The mode of fracture and growth characteristics at the fracture section of each test piece shall be recorded. If
failure is associated with the grips, this shall be reported.

14 Determination of modulus of elasticity in compression parallel to the grain
14.1

Test piece

The test piece shall be of full cross section, and shall have a length of six times the smaller cross-sectional
dimension. The end grain surfaces shall be accurately prepared to ensure that they are plane and parallel to
one another and perpendicular to the axis of the piece.

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BS EN 408:2010:+A1:2012
EN 408:2010+A1:2012
EN
408:2010+A1:2012 (E)
(E)

14.2

Procedure

The test piece shall be centre loaded using spherically seated loading-heads or other devices which permit
the application of a compressive load without inducing bending. After an initial load has been applied the
loading-heads shall be locked to prevent angular movement. The gripping devices and loading conditions
actually used shall be reported.
Load shall be applied at a constant rate. The rate of movement of the loading-head shall be not greater than
(0,000 05 l ) mm/s.
The loading equipment used shall be capable of measuring the load to an accuracy of 1 % of the load applied
to the test piece, or for loads less than 10 % of the applied maximum load, with an accuracy of 0,1 % of the
maximum applied load.
Deformation shall be measured over a central gauge length of four times the smaller cross-sectional
dimension of the piece. Two extensometers shall be used, and shall be positioned to minimize the effects of
distortion.
Deformations shall be determined with an accuracy of 1 % or, for deformations less than 2 mm, with an
accuracy of 0,02 mm.

14.3

Expression of results

The modulus of elasticity in compression Ec,0 is given by the equation:
E c,0 =

l 1 (F2 − F1 )
A(w2 − w1 )

(11)

where
F 2 - F1

is an increment of load on the straight line portion of the load deformation curve, in
newtons (see Figure 2);

w 2 - w1

is the increment of deformation corresponding to F2 − F1, in millimetres (see Figure 2).

The other symbols are as given in Clause 4.
If E c , 0 is calculated from a load/deformation linear regression the correlation coefficient should be greater
than 0,99.
The modulus of elasticity in compression shall be calculated to an accuracy of 1 %.

15 Determination of compression strength parallel to grain
15.1

Test piece

The test piece shall be of full cross section, and shall have a length of six times the smaller cross-sectional
dimension. The end grain surfaces shall be accurately prepared to ensure that they are plane and parallel to
one another and perpendicular to the axis of the piece.

15.2

Procedure

The test piece shall be loaded concentrically using spherically seated loading-heads or other devices, which

permit the application of a compressive load without inducing bending. After load pick up the loading-heads
shall be locked to prevent angular movement. The gripping devices and loading conditions actually used shall
be reported.

22


BS EN 408:2010:+A1:2012
EN
EN 408:2010+A1:2012
408:2010+A1:2012 (E)
(E)

The loading equipment used shall be capable of measuring the load to an accuracy of 1 % of the load applied
to the test piece.
Load shall be applied at a constant loading-head movement so adjusted that maximum load is reached within
(300 ± 120) s.
NOTE
This rate should be determined from the results of preliminary tests. The objective is that the time to reach
Fmax for each piece is 300 s.

The time to failure of each test piece shall be recorded and its average reported. Any single piece diverging
more than 120 s from the target of 300 s shall be reported.

15.3

Expression of results

The compressive strength fc,0 is given by the equation:
f c,o =

Fmax
A

(12)

The symbols are as given in Clause 4.
The compressive strength shall be calculated to an accuracy of 1 %.
The mode of fracture and growth characteristics at the fracture section of each test piece shall be reported.

16 Determination of tension and compression strengths perpendicular to the grain
16.1

Requirements for test pieces

16.1.1

Fabrication

The fabrication of the test pieces shall be such as to allow the application of the loads to the test piece.
NOTE 1

Suitable arrangements are shown in Annexes A and B.

For tension tests, the test piece shall be glued to steel plates or timber blocks. The gluing process shall be
capable of ensuring the specified position of the test piece during testing.
NOTE 2
A suitable adhesive for fixing the steel plates to the timber test piece is a two-part epoxy. Immediately prior to
gluing, the surfaces to be joined should be prepared by planing the timber test piece surfaces and sandblasting the steel
plates.

16.1.2
16.1.2.1

Surface preparation
General

The loaded surfaces shall be accurately prepared to ensure that they are plane and parallel to each other and
perpendicular to the test piece axis. This preparation shall be carried out after conditioning.
16.1.2.2

Structural timber

The test pieces shall have the dimensions given in Table 2 and be as shown in Figure 11.
16.1.2.3

Glued laminated timber
3

The test pieces shall have the dimensions given in Table 2, with the object of achieving a volume of 0,01 m
for tension test pieces, and be as shown in Figure 12.

23