TREEBREEDEX CONSORTIUM
ANNEXE B OF THE
ACTIVITY 5 DELIVERABLE 2 REPORT :
WOOD QUALITY ASSESSMENT : REVIEW IN TECHNICAL
PROCEDURES
Edited by
Date of edition
APR-EB-PM
20/08/2010
Revised by
Date of revision
REVIEW IN TECHNICAL PROCEDURES FOR WOOD QUALITY ASSESSMENT
TABLE OF CONTENTS
1.
THE NEED OF TIMBER CLASSIFICATION ................................................................................ 3
2.
THE TIMBER CLASSIFICATION ................................................................................................. 3
3.
DESTRUCTIVE TECHNIQUES .................................................................................................... 4
3.1. Mechanical tests ........................................................................................................................ 4
3.2. Chemical tests ........................................................................................................................... 4
3.3.Physical determinations: Density and Moisture. ........................................................................ 5
4.
NON DESTRUCTIVE TECHNIQUES ........................................................................................... 5
4.1. Mechanical tests. ....................................................................................................................... 6
4.2. Acoustical Tests. ....................................................................................................................... 6
4.3. Electromagnetic ......................................................................................................................... 7
4.4. Nuclear techniques.................................................................................................................... 8
5.
Norms and Standards ................................................................................................................... 9
5.1. ISO Timber standards ............................................................................................................... 9
5.2. EN Timber standards .............................................................................................................. 11
5.3. ASTM Timber standards ......................................................................................................... 11
5.4. National Standards .................................................................................................................. 12
6.
Bibliography ................................................................................................................................ 12
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ANNEXE B, ACTIVITY 5 DELIVERABLE 2.
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REVIEW IN TECHNICAL PROCEDURES FOR WOOD QUALITY ASSESSMENT
1. THE NEED OF TIMBER CLASSIFICATION
Owing to the publication of practice Codes, Directives and European Standards of obliged fulfilment
for the EU Schengen Countries (in order to assure the correct commercialisation of goods) the wood
quality assessment has reached a level in which all the European Woods can be compared in within.
This European Standard is based in the introduction of a grading system as it was previously done in
United Kingdom, New Zealand and Australia. Owing to this grading system a bigger competitively was
reached in between the timber producers, a reduction of market prices was also acquired but also a
bigger quality diversification was obtained. This European System of structural grading classes is
compiled in the EN338 which groups wood attending to several elastomechanical parameters (it also
makes a distinction in between coniferous and broadleaf (except for poplars which are compared to
coniferous).
So, attending the specifications of the EN 338 is possible to grade a timber in Sweden and
commercialise it in Spain without a decrease of quality or price. The next table shows an extract of the
grading classes.
Softwoods and Poplar
Res. Class (EN338)
C20
C22
C24
Resistance (N/mm²)
Bending
20
22
Parallel traction
12
13
Average MOE
MOE at 5° parallel.
9.5
6.4
Density
330
Hardwoods
D35
D40
24
35
40
14
21
24
11
7.4
10
8.7
11
9.4
Density (kg/m³)
340
350
560
590
Rigidity (kN/mm²)
10
6.7
Table 1 Extract of the EN338 (Resistance Classes).
But how wood is classified?
Traditionally, norms like the UNE 56546, the BS4978 and the DIN4074 has classify wood of conifers
or broadleaf’s into quality classes attending visual criteria. This visual criteria classification is a non
destructive method based in the observation of defects in wood logs, veneers or boards such as the
presence of knots, fractures gems… as those defects can affect the structural properties of wood.
Unfortunately, those criteria have remained national till the publication of the Standards EN 1912 and
EN 14081 that have harmonised the pass from one class to another and the interclassification of the
QC according the EN 338.
At the point 5 of this annex the national and international standards in terms of wood classification can
be observed.
2. THE TIMBER CLASSIFICATION
The estimation of the EN338 grading parameters can be done using three main techniques.
Destructive tests
Semidestructive tests
Non Destructive tests
The destruction or permanent
deformation of the sample is
necessary for the estimation.
Requires a minimal section of timber
to evaluate different parameters.
Estimates the timber parameters
without altering its capabilities.
Table 2 Definition of Test procedures.
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ANNEXE B, ACTIVITY 5 DELIVERABLE 2.
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REVIEW IN TECHNICAL PROCEDURES FOR WOOD QUALITY ASSESSMENT
In the Activity 5 Deliverable 2 Survey, the partners were asked to identify the defects that were the
most common for all their bred species, and in terms of wood quality to specify the criteria and the
measurement device and technique used for evaluate and grade the timber.
For all the tests in wood quality assessment the partners should take in account the EN 338, EN 336,
EN 384, EN 408, EN 844 and EN 1912 or their national standards (derived from the supranational
European Norms).
A classification attending the destructive or non destructive methods is done in the table below. From
148 tests, more than the half were classified as non destructive..
Destructive
67
Non destructive
76
Not specified
12
Total
148
Table 3 Classification of Survey answers (I).
3. DESTRUCTIVE TECHNIQUES
In this category the different techniques implying the deformation or destruction of the sample without
possibility of reutilisation of the sample are included. As it was shown on the table 4 most of all the
destructive techniques used were classified as quantitative.
The wood Quality assessment in destructive techniques evaluates the different parameters of the
wood resistance classess specified in the EN 338 using the specifications contained in EN 350, EN
384 and EN 408 (and the erratum EN 408 published in 2009).
The typical destructive techniques can be summarised as follows:
Mechanical
Proof loading
Chemical
Calorimetric
Compounds
Durability
Physical
Resistance
Density
Table 4 Destructive procedures
3.1. Mechanical tests
This term refers itself to all the tests concerning the calculation of MOE, MPR; strengths (tensile,
shears) and wood mechanical properties using a computerised test bench or similar and proceeding
according the specifications contained in the EN 384 and EN 408 norms. The tests normally implies
the rupture of the test sample
3.1.1. Proof loading
Main description: At proof loading, the behaviour of wood while a load is applied is tested. The rupture
or deformation (according to hooks law) allows the characterisation of wood main parameters and
through it the classification of wood according to the EN 338 grading classes.
Applications: MOE, MOR, Strength (shear, tensile or axial), impact resistances, hardness.
Equipment: Universal testing machines (Instron 5582 or similar).
3.2. Chemical tests
Chemical characterisation of wood allows the better understanding of physiological processes that can
affect the wood production; chemical test are divide into two kinds, the first is related to the amount of
energy contained in wood, the second is related to wood composites and wood compounds.
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REVIEW IN TECHNICAL PROCEDURES FOR WOOD QUALITY ASSESSMENT
3.2.1. Calorimetric tests.
Main description: All the reported tests have used the calorimetric bombs that are standard
instruments to measure the calorific values of wood samples by a substitution procedure in which the
heat obtained from the sample is compared with the heat obtained from combustion of a similar
amount of benzoic acid or other standardising material whose calorific value is known. To do so,
several norms are published such as the ISO 1928 and the DIN 51900.
Application: Moisture content, calorific value, combustion heat.
Equipment: Bomb calorimeter
3.2.2. Chemical analysis
Main description: The chemical composition of wood analyses the growth through the determination of
chemical compostion (lignins), the contain in hevay metals (can affect the growth or physiological
parameters) through ashes… Unfortunatelly, the partners did not specify which method did they use
for those criteria.
Application: Lignin, cellulosical compounds, inorganic matter.
Equipment: Combustion, HPLC, Gravimeters…
3.3.Physical determinations
Main description: All of them related to water content in wood sample. Denisty is the most evaluated
parameter using the EN408 prescriptions as well as EN 844. Gravimetries, mathemathical
modelisation and saturation methods are the most employed procedures. Shrinkage and water
movement in wood, properties related to the loss of water in the wood fibers can be done owing to
direct observation or callipers.
Application: Water content, density, shrinkage…
Equipment: Gravimeters, Callipers, Scales, Ovens (drying)…
4. NON DESTRUCTIVE TECHNIQUES
The aim of this paragraph is to summarise the different techniques in Non Destructive Evaluation
procedures for wood quality assessment independently from the answers obtained in the survey of the
activity to clarify and present the different methodologies.
As the Destructive techniques, the estimated parameters grades timber according the EN 338. And
they can be summarised as follows:
Mechanical
Proof loading
Drill resistance
Acoustic
Static bending
Pin penetration
Stress wave
Emitters
Electromagnetic
Moisture
Colour
Microwave
Light analysis
Termographies
Ultrasonic
Vibrations
Nuclear
Xray ionisation
Magnetic resonance
Gamma CT (Scattering/Backscattering).
Table 5. NDE Methodologies1
1
As it was presented in « Course in NDE Technologies », June 2008, ETSIM-Madrid.
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REVIEW IN TECHNICAL PROCEDURES FOR WOOD QUALITY ASSESSMENT
4.1. Mechanical tests.
This category refers itself to the measurement of shear, tensile, axial forces when applied to wood
samples and their effects such as bending, fracture, etc… Other mechanical tests are referred to the
penetration and drilling resistances.
Three different devices can be found to measure those effects, the mechanical computerised test
bench, which measures according to the EN 408 and ISO 3787 (or national norms like UNE 56535,
UNE 5636, UNE 56537, UNE 56542 and DIN 4074) parameters like Static Bending and Proof loading.
The resistograph which measures the resistance to drilling and the Pylodin which assess in terms of
penetration.
4.1.1. Static Bending
Main description: Defined as the action to constrain or strain to tension by curving the sample when it
supports a weight. Classifies the wood according to the EN 336 and 338. With the specifications
included in the EN 408.
Applications: Maximal curve, tensile or axial efforts, MOR, MOE.
Equipment: Computerised testing benches.
4.1.2. Proof loading:
Main description: Maximal load affordable by a wood product. It can be punctual or distributed among
the sample. Classifies the wood into one of the grading classes defined in EN 338. An experimental
device for proof loading and static bending consisting in attaching a load in the trunk to see the tree
response can be also used.
Parameter measured: tensile or axial efforts, MOR, MOE
Applications: Computerised testing benches
4.1.3. Pin penetration
Main description: The depth which a pin penetrates into timber when applying a fixed impact energy is
inversely proportional to the wood density.
Parameter measured: Density, Water Content, Hardness.
Equipment: Pylodin
4.1.4. Drill resistance
Main description: Given that healthy wood requires more energy to be drilled that decayed wood, while
voids require no energy at all. The controlled drilling applies a constant drilling speed and records the
drilling deepness along with the resistance or energy. The result is a map of the drill line in which
decayed wood can be identified drops of resistance are recorded.
Applications: Wood homogeneity, Density, Wood Water Content, Resistance.
Equipment: Resistographs
4.2. Acoustical Tests.
Main Description: Acoustic tools are a non-destructive method of predicting the physical and
mechanical properties of timber and wood-based materials through the measurement of the speed pf
a wave, vibration or sound when traversing the wood sample (standing tree, log, …).
The acoustical tests allows the forester to classify and grade the wood better than in the visual grading
due to the MOE, the decayment, the density and other properties measurement.
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REVIEW IN TECHNICAL PROCEDURES FOR WOOD QUALITY ASSESSMENT
The protocol to classify the wood according the grading kind is the EN 338.
4.2.1. Stress wave (Acoustical tools)
Definition: The application of a sound wave or stress wave in a point of the tree and the measurement
of the timing to reach the reception point gives the capacity to detect areas in which the speed varies
(higher elasticity due to lower density versus contourning owing to higher density, voids, decayments).
Applications: MOE, Density, Fungal or Bacterial Decayments (through the estimation of speed
variation via the density change of wood).
Equipment:
First generation
Second generation
Treesonic
Treetap
IML Hammer
Hitman HM200/ST300/PH330
Fakkopp 3D Ac. Tom.
IML ArboTOM
Picus Sonic Tom
Hitman LG640
4.2.2. Ultrasonic
Description: Ultrasonic emission through wood and reception to classify and detect density changes.
Applications: MOE, Density, Cracks.
Equipment: Sylvatest, Ultrasonic timers (Fakkopp), Grindosonic, Pundit.
4.2.3. Acoustic Emission
Description: Mainly used to control the drying process in final line products, this method uses a metal
stickers to monitor acoustic emission (AE) during drying, and provides means of measuring ultrasonic
transmission to determine the drying endpoint
Applications: Water content, monitorisation of drying processes, detection of cracks, shrinkages…
Equipment: Not described.
4.2.4 Vibrations
Description: The measurement of vibration frequency in wooden logs can be used to determine
material qualities. The log or standing tree is submitted to a vibration in one of the dimensional
directions, this vibration is propagated through itself and the speed recorded with the aid of a
datalogger, the vibration speed is related to the mechanical properties of the wood.
Applications: Sound velocity, modulus of elasticity or yield strength.
Equipment; Depending on the prospected vibration three machines/sensors available
Longitudinal
Transversal
Torsion
Dynagrader
Microtec Viscan
Portable Lumber Grader
Resonance Log Grader
Sawn Products
Wood Log
4.3. Electromagnetic
4.3.1. Moisture measurements
Main Description: Moisture is one of the factors affecting normally to end user products in timber (logs
or boards).
Applications: Detection of decay, distortion, shrinkage and swelling.
Equipment: Three kind of different equipment available: Pins, Capacitance and moisture sensors.
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Resistance type (Pins)
Capacitance type
Moisture sensors
Correlates the electric
resistance to moisture..
Correlation magnetic field with
moisture content.
Frequency depends on
moisture
Dependant on temperature
and species
Temperature dependant,
affected by drying or wetting
gradient
Applicable in logs
4.3.2. Microwaves
Main description: The use of this technique allows to measure the electromagnetic properties of wood
through the study of zones in which the moisture increases (normally wood is a rather good electric
insulator).
Applications : Compression wood, moisture content, density, fibre direction, knots detection,
decayment.
Equipment: Not described.
4.3.4. Thermograph techniques
Main description: Temperature of wood surface along a timber member varies depending on the
difference of diffusivity, heat conductivity and density. Knots, cracks, internal cavities and other defects
locally change the physical properties of timber and decayed wood has a loss of density, thus these
will origin local changes of temperature.
Applications: Fiber direction, Moisture content, Knots detection.
Equipment: Thermographical cameras, He-Ne Laser Machine Graders
4.4. Nuclear techniques
4.4.1. Xray CT
Main Description: The measurement of the Xray transmission-absorption in wood products (standing
tree, logs, boards,…) it is possible to separate the regions with denser wood like knots or compression
wood, as they display a higher rate of absorption than normal wood. The absorption of X-ray intensity
is completely independent of the surface quality so it is possible to use this process in sawing mills
with logs or boards presenting oil spills, dirtiness, etc...
Applications: Compression wood, decayment, density (absorption or attenuation), knots detection and
moisture content.
Equipment:
Linx systems
Wood X
Dendro ray X
Portascan
(Sawn and logs)
Wray CT for logs
Logs, boards…
(In situ & in vivo)
4.4.2. Gamma
Main Description: Gamma densitometries (Front or Backscattering) are based in the quantification of
the intensity when the probe is placed between an emitter and a receptor. The density of the probe is
measured detecting several wood changes.
Applications: Density, knots detection, fibre direction, compression or tension wood and moisture
content.
Equipment: Not described.
4.4.3. Magnetic Resonance
Main Description: The interaction in between the water content and the magnetic field created by the
scanner, makes possible the detection of zones in which the water content varies like fungal zones,
knots, cracks, splits…
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Applications: Decayment, Moisture content, knots detection….
Equipment: Magnetic CT scanners
5. Norms and Standards
The following paragraphs will indicate the norm relative to each test (ISO, EN and ASTM) the
measured parameter and the different equipment for wood assessment to complete the information
submitted by the Treebreedex Partners from 2007 till 2010.
5.1. ISO Timber standards
The following table summarises the different ISO (International Standard Organisation) norms and
references for Wood Quality Assessment as they are presented in the technical committee 218 for
timber.
Object
Sawn
timber
Norm
737:1975
738:1981
1029:1974
1030:1975
1031:1974
1032:1974
2299:1973
2300:1973
2301:1973
4470:1981
2457:1976
3130:1975
8903:1994
8904:1990
8905:1988
8906:1988
Description
Coniferous sawn timber - Sizes - Methods of measurement
Coniferous sawn timber - Sizes - Permissible deviations and
shrinkage
Coniferous sawn timber - Defects - Classification
Coniferous sawn timber - Defects - Measurement
Coniferous sawn timber - Defects - Terms and definitions
Coniferous sawn timber - Sizes - Terms and definitions
Sawn timber of broadleaved species - Defects - Classification
Sawn timber of broadleaved species - Defects - Terms and
definitions
Sawn timber of broadleaved species - Defects - Measurement
Sawn timber - Determination of the average moisture content of
a lot
Sampling methods and general requirements for physical and
mechanical tests
Determination of moisture content for physical and mechanical
tests
Broadleaved sawn timber - Nominal sizes
Broadleaved sawn timber - Sizes - Methods of measurement
Sawn timber - Test methods - Determination of ultimate strength
in shearing parallel to grain
Sawn timber - Test methods - Determination of resistance to
local transverse compression
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Standing 3132:1975
trees, wood 3133:1975
samples 3179:1974
3345:1975
3346:1975
3347:1975
3348:1975
3349:1975
3350:1975
3351:1975
4469:1981
4471:1982
4476:1983
Testing in compression perpendicular to grain
Determination of ultimate strength in static bending
Coniferous sawn timber - Nominal dimensions
Determination of ultimate tensile stress parallel to grain
Determination of ultimate tensile stress perpendicular to grain
Determination of ultimate shearing stress parallel to grain
Determination of impact bending strength
Determination of modulus of elasticity in static bending
Determination of static hardness
Determination of resistance to impact indentation
Determination of radial and tangential shrinkage
Sampling sample trees and logs for determination of
physical and mechanical properties of wood in homogeneous
stands
Determination of radial and tangential swelling
Determination of volumetric swelling
Methods of physical and mechanical testing -Vocabulary - Part
1: General concepts and macrostructure
Coniferous and broadleaved tree sawlogs - Visible defects Classification
Coniferous and broadleaved tree sawlogs - Visible defects Measurement
Coniferous and broadleaved sawlogs - Sizes - Vocabulary
8965:1987
Terminology- Technology
8966:1987
Terminology- Products
4859:1982
4860:1982
9086-1:1987
Sawlogs
4473:1988
4475:1989
Logging
industry
Table 6 ISO Timber Norms (TC218).
For the structural timber, ISO compiles also the following norms (Technical committee 165.
Object
Wood
Norm
9087:1998
Structural
Timber
9709:2005
13910:2005
Timber
structures
13912:2005
15206:2010
WD 12122
Description
Determination of nail and screw holding power under axial load
application
Visual strength grading -- Basic principles
Characteristic values of strength-graded timber -- Sampling, fullsize testing and evaluation
Machine strength grading -- Basic principles
Basic requirements and test methods in timber poles
Evaluation of characteristic values for structural timber
Table 7 ISO Timber Norms (TC165).
The TC165 has also several norms concerning the joints and fasteners that are commonly done in
timber structures.
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5.2. EN Timber standards
The following European Norms (EN) are the base standard to the national normes in Wood Quality
Assessment.
Object
Grading
Norm
EN 336
EN 1611
EN 1310
EN 1315
EN 338
Durability,
physical and
mechanical
Properties
EN 1912 +
A4:2010
EN TC 124.105
EN 1001
Calculation of
EN 384
physical and
mechanical values EN 408
for timber
ERR EN 408
EN 14251
General
Requirements for
Structural timber
EN 350
Qualitative
classification
EN 1316
EN 14081
EN 1927
Description
Sizes and permitted deviations
Appearance grading of softwoods.
Method of measurement of features in round
and sawn timber
Dimmensional clasification of round timber
Strength classes
Assignment of visual grades and species
Solid timber in structural sizes and glued
laminated timber: Probe characteristics
Durability of wood and wood-based products.
Determination of characteristic values of
mechanical properties and density
Structural timber and glued laminated timber Determination of some physical and
mechanical properties
Erratum 2009: Determination of some physical
and mechanical properties
Structural round timber.
Durability of wood and wood based products.
Natural Durability of solid wood.
Strength graded structural timber with
rectangular cross section
Qualitative classification of hardwoods round
timber.
Qualitative classification of softwoods round
timber.
Table 8 European Standards (CEN)
5.3. ASTM Timber standards
The American Standards defines timber grades and parameters as follows:
Norm
Description
D143 - 09
Standard Test Methods for Small Clear Specimens of Timber
D198 - 09
D1102 - 84(2007)
D1105 - 96(2007)
D1106 - 96(2007)
D1107 - 96(2007)
D1108 - 96(2007)
D1109 - 84(2007)
Standard Test Methods of Static Tests of Lumber in Structural Sizes
Standard Test Method for Ash in Wood
Standard Test Method for Preparation of Extractive-Free Wood
Standard Test Method for Acid-Insoluble Lignin in Wood
Standard Test Method for Ethanol-Toluene Solubility of Wood
Standard Test Method for Dichloromethane Solubles in Wood
Standard Test Method for 1% Sodium Hydroxide Solubility of Wood
D1110 - 84(2007) Standard Test Methods for Water Solubility of Wood
D1166 - 84(2007) Standard Test Method for Methoxyl Groups in Wood and Related Materials
D1666 - 87(2004) Standard Test Methods for Conducting Machining Tests of Wood and WoodBase Materials
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D1762 - 84(2007) Standard Test Method for Chemical Analysis of Wood Charcoal
D2394 - 05e1
Standard Test Methods for Simulated Service Testing of Wood and WoodBase Finish Flooring
D2395 - 07ae1
Standard Test Methods for Specific Gravity of Wood and Wood-Based
Materials
D2555 - 06
D4442 - 07
Standard Practice for Establishing Clear Wood Strength Values
Standard Test Methods for Direct Moisture Content Measurement of Wood and
Wood-Base Materials
D4444 - 08
Standard Test Method for Laboratory Standardization and Calibration of HandHeld Moisture Meters
D4761 - 05
Standard Test Methods for Mechanical Properties of Lumber and Wood-Base
Structural Material
D4933 - 99(2010) Standard Guide for Moisture Conditioning of Wood and Wood-Base Materials
D6782 - 05
Standard Test Methods for Standardization and Calibration of In-Line Dry
Lumber Moisture Meters
D6815 - 09
Standard Specification for Evaluation of Duration of Load and Creep Effects of
Wood and Wood-Based Products
D6874 03(2009)e1
Standard Test Methods for Nondestructive Evaluation of Wood-Based Flexural
Members Using Transverse Vibration
D6958 - 03(2009) Standard Test Methods for Evaluating Side-Bonding Potential of Wood
Coatings
D7438 - 08
Standard Practice for Field Calibration and Application of Hand-Held Moisture
Meters
D7469 - 09
Standard Test Methods for End-Joints in Structural Wood Products
Table 9 American Standards (ASTM)
5.4. National Standards
The following table shows up the most important national standards in Europe in terms of wood quality
assessment.
Country
France
Norm
NF 52001
Spain
UNE 56544
Description
Classement visuel pour l'emploi en structure des
principales essences résineuses et feuillues
Clasificación visual de madera aserrada. Coniferas
UNE 56546
DIN 4074
Bs 5756
Bs 4978
INSTA 142
Clasificación visual de madera aserrada. Frondosas
Sortierung von Holz nach der Tragfähigkeit
Specification for visual strength grading of hardwood
Specification for visual strength grading of softwood
Visual strength grading of Nordic T- and LT-timber
Germany
UK
Nordic
Standards
Table 10 National Standards
6. Bibliography
In the following table lies the specific bibliography with examples that can be useful in terms of
application for NDE or DE tests.
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TIMBER CLASSIFICATION
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DESTRUCTIVE TEST
BIBLIOGRAPHY
European Comission, 2003, Council Directive 68/89/EEC on the approximation of the laws of the Members States concerning the classification of
wood in the rough. Brussels 2003.
CTBA, 2007, Dictionnaire Trilingue des bois ronds et des bois sciés. Centre technique du bois et de l'ameublement. France
Alvarez R., Arriaga F.,1996, Estructuras de Madera, diseño y calculo, AITIM.
Alvarez R., Arriaga F.,1996, Estructuras de Madera, diseño y calculo, AITIM.
Beall F 1996 Future of nondestructive evaluation of wood and wood-based materials. Holzforschung und Holzverwert 5 : 73-75;
COST E53, 2010, Quality control for wood and wood products. www.coste53.net
GENERAL METHODOLOGY AND TESTS
Divos, F. . 2008, « Course in Non-Destructive Testing of Wood. Apuntes y presentaciones del curso », Madrid 13-16 junio 2008. ETS Ingenieros de
Montes - ETS Arquitectura, UPM, Madrid.
Esteban M., 2003. Determinación de la capacidad resistente de la madera estructural de gran escuadría y su aplicación en estructuras existentes de
madera de conífera. Tesis Doctoral. Escuela Técnica Superior de Ingenieros de Montes. Universidad Politécnica de Madrid.
Fernández Golfín, J.I.; Díez, M.R. y Hermoso, E., 2001. Análisis y estado del arte de la técnica de clasificación mecánica por máquina de la madera
aserrada estructural. Laboratorio de Estructuras. CIFOR-INIA. Madrid.
Galligan, W.L., Johnson R.A. Taylor J.R. 1981 Examination of the concomitant properties of lumber, Proc. of the Metal Plate Wood Truss Con&
(1979) Forest Products Laboratory, Madison, WI.
Hu L.J., 2010, Non-destructive Testing and Evaluation (NDT/E) Technique for Fingerjoint (FJ) Quality Control and Evaluation. In Research and
Development Summary, Can. Journ. Wood Scie.
IUFRO, 2010, Non-destructive evaluation on wood and wood-based materials. Reports of the technical Comittee.
4
NON DESTRUCTIVE TEST
Koizumi A., Studies on the estimation of the mechanical properties of standing trees by non-destructive bending test, Bulletin of the College
Experiment Forest, Faculty of Agriculture, Hokkaido University 44, 4 (1987) 1329-1415.
Martinis R. 2002 Non destructive techniques for decay diagnosis on standing trees . Thesis University of Florence, Italy;
Pellerin F., Ross R.J., 2002, Nondestructive Evaluation of Wood. Compiled and Edited by Roy F. Pellerin and Robert J. Ross; Forest Products
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