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Wood product test methods and stress class systems in the world Wang, Youhai 2004

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WOOD PRODUCT TEST METHODS AND STRESS CLASS SYSTEMS IN THE WORLD by YOUHAI WANG B.Sc, Harbin University of Civil Engineering and Architecture, 1983 M.Sc, Harbin University of Civil Engineering and Architecture, 1986 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRAD_UATE_STUDIES (FORESTRY) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA April 2004 ©Youhai Wang, 2004 JUBCI mm THE UNIVERSITY OF BRITISH COLUMBIA FACULTY OF GRADUATE STUDIES Library Authorization In p resen t ing th is thes is in part ia l fu l f i l lment of the r e q u i r e m e n t s fo r an a d v a n c e d d e g r e e at the Univers i ty of Bri t ish C o l u m b i a , I a g r e e that the L ibrary shal l m a k e it f ree ly ava i lab le for re fe rence a n d s tudy . I fu r ther ag ree that pe rm iss ion for ex tens ive c o p y i n g of th is thes is for scho la r l y p u r p o s e s m a y be g r a n t e d by the h e a d of m y d e p a r t m e n t or by h is or her represen ta t i ves . It is u n d e r s t o o d tha t c o p y i n g or pub l ica t ion of th is thes is fo r f inanc ia l ga in shal l not b e a l l o w e d w i thou t m y wr i t ten p e r m i s s i o n . o 5 / l 0 /3-004 N a m e of A u t h o r (please print) Date ( d d / m m / y y y y ) Ti t le of T h e s i s : W OO D P f i S O i i C T T E * T METHQJtt 5lHl$S> ClAS>S> < ^ T ^ S D e g r e e : M • A > Sen. Year : D e p a r t m e n t of W O 0 D S C . l E . t f C E T h e Univers i ty of Br i t ish C o l u m b i a V a n c o u v e r , B C C a n a d a g r a d . u b c . c a / f o r m s / ? f o r m l D = T H S p a g e 1 of 1 last updated: 5-Oct-04 ABSTRACT This thesis describes a study to review the standards for derivation of characteristic values of wood products and examines the equivalence issues amongst various testing procedures and methods for assigning stress graded lumber to various stress class systems. The study is based on reviews of international standards for wood products including the ISO standards (draft ISO CD 8872, ISO DIS 13910), Australia and New Zealand standard (AS/NZS 4603), European codes (EN 338, EN 384) and North American in-grade based procedures (ASTM series) and Canadian standard CSA 086-01. The study examines the property relationships adopted in the various stress class systems and provides adjustment models for comparing strength and stiffness test data derived according to North American in-grade based procedures, European, and Australian/New Zealand test methods. This work supports efforts directed to establishing an international protocol for establishing equivalencies among the various full-size timber testing procedures and methods for assigning stress grades to strength class systems ii TABLE OF CONTENTS ABSTRACT ii TABLE OF CONTENTS iii LIST OF TABLES v LIST OF FIGURES vi ACKNOWLEDGEMENTS vii 1.0 INTRODUCTION 1 1.1 Background 1 1.2 Research Objectives 3 2.0 REVIEW OF TEST STANDARDS 4 2.1 Testing Method Comparison 5 2.1.1 Bending Tests 5 2.1.2 Tension and Compression Tests 7 2.1.3 Other Tests 7 2.2 Stress Class Comparison 7 2.3 Chinese Standards 10 2.3.1 Test Methods 10 2.3.2 Stress Classes 10 2.3.3 Future Developments 10 3.0 SURVEY OF LITERATURE 12 3.1 Leicester Study 12 3.2 Isaksson-Thelandersson Study 13 3.3 Czmoch Study 15 3.4 Cheung Study 16 3.5 Comments on the Studies and Discussion for Effects to Strength Properties.. 18 3.5.1 Comments on the Studies 18 3.5.2 Discussion for Effects to Strength Properties 19 4.0 CANADIAN DATABASE FOR PROPERTIES OF SPRUCE-PINE-FIR 21 4.1 Introduction for CEN test 21 4.1.1 Sample Size and Grade 21 4.1.2 Moisture Conditioning and Moisture Content of Lumber 22 4.1.3 Sample Selection 23 4.1.4 Testing Methods 23 4.1.5 Determination of Modulus of Rupture and Modulus of Elasticity 24 4.2 Results of CEN Test 26 4.3 Comparison Analysis between CWC Test and CEN Test 28 4.3.1 MOR Comparison 28 4.3.2 MOE Comparison 28 4.3.3 Density Comparison 31 5.0 EQUIVALENCE OF DIFFERENT STANDARDS 32 5.1 Equivalence Model for MOR 32 5.2 Equivalence Model for MOE 33 5.3 Adjustment Factors 34 5.4 Equivalence Stress Classes for Canadian Dimension Lumber 34 5.4.1 Equivalence to CEN Grades 34 5.4.2 Equivalence to ISO Grades 38 6.0 CONCLUSIONS AND RECOMMENDATIONS 40 6.1 Conclusions 40 6.2 Recommendations 40 REFERENCES 41 Appendix A MOR Comparison 43 Appendix B MOR Difference 44 Appendix C M O E Comparison 45 Appendix D MOE Difference 46 Appendix E Adjustment Properties to ISO Standard for NLGA Lumber 47 LIST OF TABLES Table 2.1 Summary of Test Specimen Sizes and Defect Location Criteria for Different Standards 6 Table 2.2 Strength Classes in CEN/prEN 338 8 Table 2.3 Specified Strength and Modulus of Elasticity for Post and Timber Grades in CSA 086-01 (MPa) 9 Table 2.4 Summary of Specified Strength Design Values (N/mm2) in GB50005 - 2003 ... 11 Table 4.1 Size 2x4 Samples of Spruce-Pine-Fir 21 Table 4.2 Size 2x6 Samples of Spruce-Pine-Fir , 21 Table 4.3 Size 2x8 Samples of Spruce-Pine-Fir 22 Table 4.4 Size 2x10 Samples of Spruce-Pine-Fir 22 Table 4.5 Sample Fifth Percentile Strength Values (MPa) 26 Table 4.6 Sample Mean of Modulus of Elasticity Values (MPa) 27 Table 4.7 Sample Density Values (kg/m3) 27 Table 4.8 Characteristic Density for Canadian Lumber Spruce-Pine-Fir 31 Table 5.1 Comparison Ratios for Modulus of Rupture (MOR) 32 Table 5.2 Mean and 5-Percentile MOE Values (MPa) 33 Table 5.3 Adjustment Bending Strength for Canadian Douglas Fir-Larch (MPa) 34 Table 5.4 Adjustment Bending Strength for Canadian Hem-Fir (MPa) 35 Table 5.5 Adjustment Bending Strength for Canadian Spruce-Pine-Fir (MPa) 35 Table 5.6 Adjustment Bending Stiffness for Canadian Douglas Fir-Larch (MPa) 36 Table 5.7 Adjustment Bending Stiffness for Canadian Hem-Fir (MPa) 36 Table 5.8 Adjustment Bending Stiffness for Canadian Spruce-Pine-Fir (MPa) 37 Table 5.9 CEN Strength Classes for NLGA Lumber Using CWC Data 38 Table 5.10 ISO Strength Classes for NLGA Lumber Using CWC Data 39 Table E. l Adjustment Bending Strength for Canadian Douglas Fir-Larch (MPa) 47 Table E.2 Adjustment Bending Strength for Canadian Hem-Fir (MPa) 47 Table E.3 Adjustment Bending Strength for Canadian Spruce-Pine-Fir (MPa) 48 Table E.4 Adjustment Bending Stiffness for Canadian Douglas Fir-Larch (MPa) 48 Table E.5 Adjustment Bending Stiffness for Canadian Hem-Fir (MPa) 49 Table E.6 Adjustment Bending Stiffness for Canadian Spruce-Pine-Fir (MPa) 49 v LIST OF FIGURES Fig. 2.1 Third-point Loading System for Bending Test 5 Fig. 3.1 The Cumulative Probability Distribution of Bending Strength for Grades F5 and F8 Material 12 Fig. 3.2 The Cumulative Probability Distribution of Bending Stiffness for Grades F5 and F8 Material 13 Fig. 3.3 The Cumulative Probability Distribution for Bending Strength Simulated According to CEN, ASTM and AS/NZS Standards 14 Fig. 3.4 Simulated Timber Beam Strengths according to North American in-grad and EC-5 Testing Methods 16 Fig. 3.5 The Cumulative Probability Distribution of Bending Stiffness of Cheung Study . 17 Fig. 3.6 The Cumulative Probability Distribution of Bending Strength of Cheung Study.. 18 Fig. 4.1 Comparison of MOR between CEN and CWC Tests 29 Fig. 4.2 MOR Differences from 2.5 to 50 - Percentile Bending Strength 29 Fig. 4.3 Comparison of MOE between CEN and ASTM Tests 30 Fig. 4.4 MOE Differences from 2.5 to 50 - Percentile Stiffness 30 Fig. 5.1 Converted Factors 32 Fig. 5.2 Regression Relationship between M O E A S T M and M O E C E N 33 Fig. A. 1 Comparison of MOR between CEN and CWC Tests for 2x8 Lumber 43 Fig. A.2 Comparison of MOR between CEN and CWC tests for 2x10 Lumber 43 Fig. B . l MOR differences from 2.5 to 50 - percentile strength for 2x8 Lumber 44 Fig. B.2 MOR differences from 2.5 to 50 - percentile strength for 2x10 Lumber 44 Fig. C. l Comparison of MOE between CEN and ASTM Tests for 2x8 Lumber ...45 Fig. C.2 Comparison of MOE between CEN and ASTM Tests for 2x10 Lumber 45 Fig. D.l MOE Differences from 2.5 to 50 - Percentile Strength for 2x8 Lumber 46 Fig. D.2 MOE Differences from 2.5 to 50 - Percentile Strength for 2x10 Lumber 46 vi ACKNOWLEDGEMENTS I would like to express my profound gratitude to Dr. J.D. Barrett and Dr. F. Lam, my supervisors for accepting me as their graduate student. Their guidance, advice and criticisms as well as the financial support provided during my studies are highly appreciated. I would like to also thank my committee members-Dr. M.J. He from Tongji University, China and Dr. C. Ni from Forintek, Canada. Thanks are also due to George Lee, and Bob Myronuk of Wood Mechanics and Timber Engineering Laboratory, Department of Wood Science for their patience, sense of duty and work ethics during the laboratory testing exercises I did in the course of my program and Dr. Raymundo Davalos - a visiting professor for his valuable information of Mexican timber engineering. I would like to thank my colleagues, Alexander. Schreyer, Peggi Clouston, Jungpyo Hong, and Benjamin Zhuang and my friends Ye Zhou, Zhiming Fan, Yafang Yin, Junli Zhang and Derek Thompson for their continuous encouragement. Finally, truly unbounded thanks are due to my wife, Huijun and son, Franklin, who, with their love and their understanding of my efforts, supported me in my study. vii Chapter 1. Introduction 1.0 INTRODUCTION 1.1 Background Many people prefer to use wood products as a structural material. One of reason is that wood is the only natural renewable structural material in the world and structural wood products (stress graded) are generally available from many parts of the world. But these positive attributes of wood products may in fact create confusing issues for designers and consumers in countries that rely on the import of wood products especially for an emerging country such as China which has lost its tradition of using wood structurally but is poised to renew its use of wood construction (Lam, F. 2003). Because the strength properties of wood products are highly species dependent and therefore region (source) dependent and different regions in the world produce lumber of different sizes and have different methods of grading and assessing the quality and strength properties of material, the properties of lumber in various countries are significantly different. So, for an emerging country, acceptance of material from different regions in the world can be further hampered due to the lack of an international consistent protocol in testing and grading methods. Europe and Australia have created and developed strength class or structural class system to simplify the structural us of sawn lumber (In European EN 338 and Australia AS 1720.1). The strength class system groups different grades and species with similar properties together. As long as the material belongs to a particular strength class, material can be used interchangeably in terms of the structural performance no matter what its species, origin, and original grade is. The corresponding testing standards are EN384 and AS/NZS 4603 in these two countries. Based on the principles of EN 338 and EN 384, a draft ISO working document ISO CD 8972 "Structural timber - Structural classes" is being developed for structural timer species that have an associated set of defined design properties. The material can be defined by parameters such as species or species grouping, source and strength grade. It is proposed that timber can be allocated into a particular structural class based on the bending strength / m , k and modulus of elasticity Eo,m ean- Furthermore, ISO CD 8972 is linked with ISO/DIS 13910 "Structural timber - Sampling, full - size testing and 1 Chapter 1. Introduction evaluation of characteristic values of graded timber", which demonstrates all protocols to determine the strength properties of timber. There are obvious advantages to such systems: 1. Additional species/grades can be incorporated into the structural class system at any time without affecting the material design properties of an appropriate and specified strength class. 2. At the time of carrying out design calculations, a designer does not need to be aware of the costs and availability of alternative species/grade. The design can be developed by using the strength values of a specified strength class (or a higher strength class). Then, in the tendering process, the most suitable and economic species/grade available can be selected. 3. Suppliers can offer their material to meet more specifications than would be possible if specific species and non-strength class grades were specified. The strength class approach has not been adopted in North America. For example, the Canadian Code (CSA 086-01) and the U.S. Code (NDS 2001) published species or species group dependent design values. This is because the domestic supply of major species group of structural timber dominates the North American construction market; therefore, the species dependent design value system is very convenient for North American producers, users and designers. Engineering codes and standards organizations in many nations have adopted full-size member testing as the preferred basis for establishing short-term strength properties of structural timber products. Full-size testing offers the advantage of providing knowledge of member structural behavior under in-service load and climate conditions (Barrett, J.D. and F. Lam 1994). While the concept of full-size testing has been widely used, the specific test procedures adopted in national standards are sufficiently different that equivalencies between test results are difficult to establish in the absence of additional direct comparison tests of substantial scope. So it is important that concerted efforts are directed to establishing an equivalence among the various full-size timber testing standards and strength classes. 2 Chapter 1. Introduction 1.2 Research Objectives 1. Test method research Conduct a literature survey to gain an understanding of various international codes for wood products, which include the ISO standards (draft ISO CD 8872, ISO DIS 13910), Australian and New Zealand code (AS/NZS 4603), European codes (EN 338, EN 384), Japanese codes (JIS 2101, draft 1996), Chinese code (GB 50005-2003) and North American in-grade based procedures (ASTM series) to compare the different test methods. 2. Stress class research Understand the stress class systems used in the world and the North American species dependent grade systems, and the process of lumber grade classification in ISO, CEN, AS/NZS, USA/CAN, etc. 3. Equivalence principal research • Study the relationship of Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) collected by different test methods • Recommend equivalency rules and models for test values obtained by different test methods. • Establish corresponding strength grades for Canadian dimension lumber using the equivalency rules. 3 Chapter 2. Review of Test Standards 2.0 REVIEW OF TEST STANDARDS This review is based on an examination of the following international and national standards. International Organization for Standardization ISO: ISO DIS 13910 Structural timber- Sampling, full-size testing, and evaluation of the characteristic values of strength graded timber (draft) ISO CD 8972 Structural timber - Structural classes (draft) Australia/New Zealand Standard: AS/NZS 4603:1992 Timber-Stress Graded - In-grade strength and stiffness evaluation AS 1720.1-1997 Timber structures - Part 1: Design methods US/Canada Standards: American Society for Testing and Materials (ASTM) ASTM D 4761-96 Standard test methods for mechanical properties of lumber and Wood-base structural material ASTM D1990-97 Standard practice for establishing allowable properties for visually-graded dimension lumber from in-grade tests of full-size specimens Canadian Standards Association (CSA) CSA 086-01 Engineering design in wood European Committee on Standardization: CEN / prEN 384:2000 Structural timber - Determination of characteristic values of mechanical properties and density of timber CEN / prEN 338:2000 Structural timber - Strength classes Japanese Standards: JIS-Z 2101-1994 Methods of testing for wood Draft standard- Evaluation standard for design strength of lumber Chinese Standards: GB 50005-2003 - Code for design of timber structures GB 50329-2002 - Standard for testing methods of timber structures 4 Chapter 2. Review of Test Standards 2.1 Testing Method Comparison Test specimen size and defect location criteria for bending, tension and compression strength properties stipulated by the relevant Australia/New Zealand, European, USA/Canada, China, Japan and ISO standards are summarized in Table 2.1. With one exception, that is, random tension edge for bending tests, the test methods for all major structural properties differ between these standards. These differences include test specimen length and test zone selection could significantly affect the strength properties derived through an in-grade testing program. 2.1.1 Bending Tests A typical full size bending strength and stiffness test configuration stipulated in different standards is shown in Figure 2.1, which is often called a third-point loading system. The lack of consistency among the test procedures for bending strength (MOR) and stiffness (MOE) is potentially problematic (see Table 2.1). The AS/NZS standard allows a completely random selection of the test zone. The CEN standard adopts a defect-biased approach where the critical defects are located in the maximum moment zone. The ASTM standard allows the test zone selection procedure to be varied depending on the purpose of the test. In the Canadian and US coordinated in-grade testing program, a critical zone, containing the maximum strength reducing defect (MSRD), was located randomly in the bending test span. In a draft Japanese standard (1996), the distance between the supports is required to be at least 18 times longer than the depth of the test specimen. However, if it is impossible to prepare a test specimen, which is long enough to cover the stipulated distance between the supports, the span-to-depth ratio can be adjusted between 15 and 21. Furthermore, in the draft Japanese standard (1996), the largest defect, such as the largest knot, may be located anywhere between the supports. The ISO standard is based on the European standards (EN 384, EN 408, and EN 1193) but the critical location selection is identical with AS/NZS standard. L o a d = P/2 L o a d =P/2 1 1 ] 3> T d/2 L/3 L/3 L/3 d/2 Fig. 2.1 Third-point Loading System for Bending Test 5 Chapter 2. Review of Test Standards Table 2.1 Summary of Test Specimen Sizes and Defect Location Criteria for Different Standards Property Parameter Test Standards AS/NZS 4603 CEN-prEN 384 ASTM D4761 CHN-GB50005 JAPAN (1996) ISO DIS 13910 Bending Span/Depth1 18 18 17-212 Clear wood9 15-21 18 Tension Edge Random Random Random Random Random Test Zone Random Biased3 Optional4 Optional Random Tension Gauge Length L=2250+7.5W<30W >9W >12W N/A 8 2000 + 8W Compression Gauge Length Long: L=30W 6T >2.5W6 N/A 2000 + 8W 7 Short5: L<10T 1. L=Length=Span; W=Width=Depth; T= Thickness 2. Span/Depth optional. L/W =17 for in-grade programs. 3. Critical section located in the maximum moment region. Grade at critical section. 4. Critical section located randomly in test span for in-grade program. Grade full length. 5. Select 4 specimens containing worst defects at mid-height. Weakest zone is compression strength. 6. US in-grade program - two test zones selected, the lowest is member strength. 7. The specimen should be restrained against lateral buckling with the spacing of 10T for buckling about the minor axis and 10W for buckling about the major axis. 8. Tension and compression properties will be derived from bending properties based on established strength property relationship. 9. The small clear wood test is still used in China 6 Chapter 2. Review of Test Standards 2.1.2 Tension and Compression Tests Test methods adopted for full-size tension and compression tests differ in the test zone selection procedure and test gauge length. The AS/NZS and ISO random location procedure could yield higher short-term strength properties than the other standards where the critical section is located in the test zone. Table 2.1 shows that significant differences in specimen length are permitted in the various standards. For instance, the tension test gauge length for a member with width W=100 mm, can vary from 900 mm in the CEN procedure to 3000 mm in the AS/NZS standard. It is known that longer specimens tend to give lower strength properties. However, in this case, the comparisons are further complicated because the AS/NZS and ISO standards allow a random test zone while the CEN standard requires the critical defect to be located in the tested region and ASTM standard permits the critical section to be located randomly in the test span for in-grade program. The difference in AS/NZS, European, ASTM and ISO tension and compression test methods makes direct comparison of test data difficult. Studies of length effect in Canadian, US and European softwoods (Madsen 1992, Barrett and Fewell 1990, Green and Evans 1989, Barrett and Lau 1994, Rouger, and Barrett) provide a basis for estimating the effect of test specimen length on tension and compression properties. However, there are no published studies directly comparing the tension and compression strength results from the various test standards. 2.1.3 Other Tests Besides the test methods for the main bending properties (MOR, MOE), the test methods for other properties such as tension strength perpendicular to grain, compression strength perpendicular to grain and shear strength in various standards are also different. 2.2 Stress Class Comparison There are mainly two methods of assigning designing properties to stress graded lumber. One is called a stress or strength class system, which groups all species with similar strength properties together into one strength class (see Table 2.2). The other method classifies material in terms of species or species group and provides strength property information for special grades within a species group (Table 2.3). 7 Chapter 2. Review of Test Standards Table 2.2 Strength Classes in CEN/prEN 338 Strength classes-Characteristic values Poplar and soft species Hard wood species C14 C16 C18 C20 C22 C24 C27 C30 C35 C40 C45 C50 D30 D35 D40 D50 D60 D70 Strength properties (in N/mm2) Bending fm,k 14 16 18 20 22 24 27 30 35 40 45 50 30 35 40 50 60 70 Tension/Para. /t,0,k 8 8 11 12 13 14 16 18 21 24 27 30 18 21 24 30 36 42 Tension/Perp. /t,90,k 0.4 0.4 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Compress i on/Para. /c,0,k 16 16 18 19 20 21 22 23 25 26 27 29 23 26 26 29 32 34 Compression/Perp. /c,90,k 2.0 2.0 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.1 3.2 8.0 8.8 8.8 9.7 10.5 13.5 Shear /v,k 1.7 1.7 2.0 2.2 2.4 2.5 2.8 3.0 3.4 . 3.8 3.8 3.8 3.0 3.4 3.8 3.8 3.8 3.8 Stiffness properties (in kN/mm2) Mean modulus Eo,mean 7 8 9 9.5 10 11 11.5 12 13 14 15 16 10 10 11 14 17 20 of elasticity/Para. 5% modulus Eo, 05 4.7 5.4 6.0 6.4 6.7 7.4 7.7 8.0 8.7 9.4 10.0 10.7 8.0 8.7 9.4 11.8 14.3 16.8 of elasticity/Para. Mean modulus E90,mean .23 .27 .30 .32 .33 .37 .38 .40 .43 .47 .50 .53 .64 .69 .75 .93 1.13 1.33 of elasticity/Perp. Mean shear Gmean .44 .50 .56 .59 .63 .69 .72 .75 .81 .88 .94 1.0 .60 .65 .70 .88 1.06 1.25 modulus Density (in kg/m3) Density Pk 290 310 320 330 340 350 370 380 400 420 440 460 530 560 590 650 700 900 Mean density pmean 350 370 380 390 410 420 450 460 480 500 520 550 640 670 700 780 840 1080 8 Chapter 2. Review of Test Standards Table 2.3 Specified Strength and Modulus of Elasticity for Post and Timber Grades in CSA 086-01 (MPa) Species Grade Bending Longitudinal Compression Tension Modulus identification at shear Parallel Perpendicular parallel of extreme to to to elasticity fibre grain grain grain / b / v fc fcp ft E E05 D Fir-L SS 18.3 1.2 13.8 10.7 12 000 8 000 No.l 13.8 0.9 12.2 7.0 8.1 10 500 6 500 No.2 6.0 0.9 7.5 3.8 9 500 6 000 Hem-Fir SS 13.6 1.0 11.3 7.9 10 000 7 000 No.l 10.2 0.7 10.0 4.6 6.0 9 000 6 000 No.2 4.5 0.7 6.1 2.8 8 000 5 500 S-P-F SS 12.7 0.9 9.9 7.4 8 500 6 000 No.l 9.6 0.7 8.7 5.3 5.6 7 500 5 000 No.2 4.2 0.7 5.4 2.6 6 500 4 500 Northern SS 12.0 0.8 7.5 7.0 8 000 5 500 No.l 9.0 0.6 6.7 3.5 5.3 7 000 5 000 No.2 3.9 0.6 4.1 2.5 6 000 4 000 9 Chapter 2. Review of Test Standards 2.3 C h i n e s e S t a n d a r d s 2.3.1 Tes t M e t h o d s Design properties for structural timber in China are derived from tests on small clear wood samples according to the national standards GB 1927 - 1943 - 91 "Testing methods for physical and mechanical properties of wood". That testing system was based on the former Soviet Union's technical standards, which were established several decades ago. It is well recognized that full size in-grade testing provides the most reliable test results to define the strength properties of lumber and engineered wood product. Although a new testing standard GB/T 50329 - 2002 "Standard for testing methods of timber structures" was published on July 2002, it does not seem to be suitable for all properties of wood because it resembles a timber structural property checking standard rather than a testing standard for establishing timber property itself. So in-grade testing for Chinese wood products is needed urgently to derive engineering property data for derivation of design properties. 2.3.2 St ress C las ses China has a strength class approach to grading where materials are grouped together according to their strength properties as stipulated in GB 50005 - 2003 "Codes for design of timber structures". There are 8 strength classes for softwood and 4 strength classes for hardwood. For example, TC 17A means the design bending strength of this class is 17 MPa and there are an associated set of strength properties for this class which include several species such as Chinese Weeping Cypress, Western Larch, Longleaf Pine and Wet Land Pine. So there is only one property table (see Table 2.4) for all the softwood species, and the data shown in the table includes adjustments with hidden factors. Therefore, they are design values rather than characteristic values. For example, the resistance factor for reliability design has already been incorporated within the design values. 2.3.3 F u t u r e D e v e l o p m e n t s Some developments are needed for Chinese standards in terms of technical aspects, such as a procedure for in-grade lumber evaluation (sampling and test methods; establishing lumber properties and relationships) of new and existing commercial species 10 Chapter 2. Review of Test Standards combinations, development of an appropriate stress class system for structural lumber, and so on. Table 2.4 Summary of Specified Strength Design Values (N/mm2) in GB50005 - 2003 Strength Class Sub-division Bending strength / b Compression and bearing parallel to grain fc Tension parallel to grain/, Shear parallel to grain/ v Compression perpendicular to gra in / C t 9 0 Modulus of elasticity M O E Whole bearing Local and teeth bearing Bearing under washer of tension bolts TC17 A 17 16 10 1.7 2.3 3.5 4.6 10000 B 15 9.5 1.6 TC15 A 15 13 9 1.6 2.1 3.1 4.2 10000 B 12 9 1.5 TC13 A 13 12 8.5 1.5 1.9 2.9 3.8 10000 B 10 8 1.4 9000 TC11 A 11 10 7.5 1.4 1 0 2.7 3.6 9000 B 10 7 1.2 1 . 0 TB20 - 20 18 12 2.8 4.2 6.3 8.4 12000 TB17 - 17 16 11 2.4 3.8 5.7 7.6 11000 TB15 - 15 14 10 2 3.1 4.7 6.2 10000 TB13 - 13 12 9 1.4 2.4 3.6 4.8 8000 TB11 - 11 10 8 1.3 2.1 3.2 4.1 7000 11 Chapte r 3. S u r v e y o f Li te ra ture 3.0 SURVEY OF LITERATURE 3.1 Leicester Study Leicester, Breitinger and Fordham (1994) studied the equivalences among various in-grade test methods. The study examined the bending strength and stiffness of 90mm x 35mm F5 and F8 grades of mechanically stress graded Australia Radiata pine measured according to European, North American and Australian standards. Approximately 150 boards, each 4800 mm long, were tested according to the three in-grade standards. The data indicated small but significant differences of about 20% at both the mean and 5 t h -percentile strength and stiffness due to the test methods used (Leicester, 1994). As expected, the data based on the North American testing method (ASTM series) was somewhere between the C E N and the AS/NZS methods. Generally, the data for North American and AS/NZS were not far apart. However, at the 5 t h -percentile level the North American data was closer to the C E N data as compared with the AS/NZS data in the case of F5 grade material (see Figures 3.1 and 3.2). th Amer ca <1ZS £ 0 AO GO 30 lOO Ber> d i n g S t r e n g t h ( M P a ) ( a ) F6 G r a d e o OJB I 9 <3 North / .merica ^0 20 40 CO 80 100 120 B a n d i n g S t r e n g t h ( M P a ) (fc>) Fe G r a d e Fig. 3.1 The Cumulative Probability Distribution of Bending Strength for Grades F5 and F8 Material 12 Chapter 3. Survey of Literature so ' °4 » E N North America A S / N Z S Bending Stiffness (GPa) (a) FS Grade u. 1 ^ S/MZS H N a °~ North Ar -nerica • 8 12 18 Bending Stiffness {MPa) (b> F8 Grade Fig. 3.2 The Cumulative Probability Distribution of Bending Stiffness for Grades F5 and F8 Material 3.2 Isaksson - Thelandersson Study A paper on the effect of standard, length and load configuration on bending strength of structural timber by Isaksson and Thelandersson (1995) was published in the conference proceedings of CIB-W18 , Copenhagen, Denmark, Apr i l 1995. In their research, the within member variability of bending strength in structural timber was investigated in an experimental study of 133 boards of Norway spruce (Picea Abies). For each board the bending strength was determined in 4-7 of the weakest sections along the length. The choice of test sections was based on knot measurements and readings from two different types of machine grading. The results from the experimental investigation were used to compare three different standards (European, North American and Australian) for determining characteristic bending strength. These studies were made by direct simulation from the test data on 13 Chapter 3. Survey of Literature single sample. The critical section (grade determining defect) as referenced by the European and North American test standards was chosen on the basis of a machine stress grader, the Cook-Bolinders. The section with the lowest Cook-Bolinders reading (force necessary to give the board a specified flatwise deflection) was selected as the critical section. If it was impossible to test the section, because it was located near the end of the board, the section with the next lowest reading was chosen. This situation could occur when using the European standard since the test section is required to be in the maximum moment zone. In the simulation study according to the A S T M standard, the critical section is placed randomly between the supports. It was found that the difference between the three test standards was very small for the simulation material, as shown in Figure 3.3 (statistically not significantly different). On the other hand, the results from the simulated tests, according to all three standards were significantly higher than the strength of the weakest section within the board both for the 50 t h and the 5 t h percentile values of the distributions. The simulations also showed very small length effects for the sample investigated. The difference in strength distributions for lengths of 2 . 2 m and 4.2 m was not statistically significant, although both the mean and the 5 t h percentile for the longer beams were slightly lower than for the shorter ones. B e n d i n g S t r e n g t h [ M P a ] Fig . 3.3 The Cumulative Probability Distribution for Bending Strength Simulated According to C E N , A S T M and A S / N Z S Standards 14 Chapter 3. Survey of Literature 3.3 Czmoch Study Czmoch, Thelandersson and Larson (1991) established a simple model of the length -wise variation of strength to evaluate • the influence of length on the strength of timber members • the influence of load configurations deviating from the standard test configuration used for assigning characteristic strength values • the influence of different test procedures e.g. the difference between the North American practice (where the length to be tested is chosen randomly) and the European practice (where Eurocode 5* prescribes the tested length shall contain a grade determining defect) • the influence of the test procedure on the reliability parameters. A simulation based on the model for the comparison between EC-5 and North American in-grade test methods was done. It was found that the characteristic value obtained from the EC-5 method is significantly smaller (Figure 3.4). As expected, the North American in-grade method always gave higher strengths than the EC-5 method. The EC-5 characteristic value should be multiplied by a factor 1.10 - 1.25 to match the characteristic value from the North American in-grade tests. On the graph, E3 means Data Set No.3; NZDTL means the scale of fluctuation for distances between weak zone; and NZSTR means scale of fluctuation for strengths of weak zone. Actually, the real meanings of NZDTL and NZSTR are degree of correlation for strengths of weak zone and for distances of weak zone, and scale of fluctuation is a degree of correlation or correlation level in a Gaussian type correlation function that is assumed both for the stationary random series of strength of weak zones and the stationary random series of distances between weak zones. * prEN384 is one part of Eurocode 5 15 Chapter 3. Survey of Literature Bending Strength (MPa) Cumulative distribution Data set:E3 N2DLT=4 NZSTR=4 // / / t j / / l n grade EC-5 / / — y / / / I i / V ——i 1 1 " 0 25 50 75 100 125 Bending Strength (MPa) Fig. 3.4 Simulated Timber Beam Strengths according to North American in-grad and EC-5 Testing Methods 3.4 Cheung Study In research by Cheung (1991) on European CEN/US In-Grade Comparison Study, a total of 924 pieces of Douglas fir produced by two sawmills (Lot A and Lot B) were tested. They included four sizes of 38mm x 89mm or 2x4 (77 No.l, 77 No.2), 38mm x 140mm or 2x6 (77 No.l , 77 No.2), 38mm x 184mm or 2x8 (77 No.l, 77 No.2), and 38mm x 235mm or 2x10 (77 No.l). The placement of the principal strength-reducing characteristic was determined according to the protocol being used in ASTM or CEN standards. For specimens being tested according to the CEN standard, the grade-controlling characteristic was placed at midspan. For ASTM specimens, the grading 16 Chapter. 3. Survey of Literature controlling characteristic was located according to random charts on the board. Some test results are shown in Figures 3.5 and 3.6. From the graphs, we find that there is significant difference in both the MOE and MOR, i.e. the MOE or MOR by ASTM is significantly higher than that by CEN, except the MOE of 38mm x 184mm (2 x 8) No.l group. MOE, 2 x 8 No. 1 M o d u l u s o f Elast ici ty (MPa) (Thousands) MOE, 2 x 8 No. 2 M o d u l u s of Elast ic i ty (MPa) ( T h o u s a n d s ) Fig. 3.5 The Cumulative Probability Distribution of Bending Stiffness of Cheung Study 17 Chapter 3. Survey of Literature MOR, 2x8 No. 1 Modulus of Rupture (MPa) MOR, 2 x 8 No. 2 Modulus of Rupture (MPa) Fig. 3.6 The Cumulative Probability Distribution of Bending Strength of Cheung Study 3.5 Comments on the Studies and Discussion for Effects to Strength Properties 3.5.1 Comments on the Studies The Leicester, Czmoch and Cheung studies reach similar results although Leicester and Cheung used physical tests method and Czmoch used a simulation approach. However the Isaksson - Thelandersson study produced a different result. In the Cheung study, the 18 Chapter 3. Survey of Literature MOE of 38mm x 184mm No.l sample is not consistent with other results. The reason for the statistically in significant difference for the Isaksson - Thelandersson study could be that the investigation was made on timber with a fairly high bending strength (mean bending strength is 54.7 MPa) and the strength in weak sections of the boards did not show any strong variation within boards, so that the effect of the serious defect zone almost vanished. This might also be the reason that the length effect was very small. The explanation for the significantly larger simulated strength, compared to the measured minimum strength within the board could be, firstly, that the section with minimum strength could not be found with great precision using machine stress grading results, and secondly, that in cases where the weakest section was near the end of the board, it could not be tested due to geometrical constraints. 3.5.2 Discussion for Effects to Strength Properties Structural timber displays a considerable strength variability within members, which makes it difficult to evaluate its reliability and to design timber members in a rational way (Isaksson and Thelandersson 1996). Engineering design methods for timber, however are based on elementary theory of structures assuming homogeneous material. In reality, the strength is highly variable along a timber board, implying that the real strength depends on length, load configuration and other factors, which are not considered in elementary engineering design. For example, the results from testing of characteristic strength of timber can be expected to depend on the strategy used when selecting the test specimens and that part of a timber board to be placed in the region where the largest stresses occur during test. This strategy is interpreted quite differently as shown above. Furthermore, the apparent strength of a timber beam will also depend on the nature of the moment distribution along the beam. For instance, a beam with a point load at mid-span can be expected to have an apparent strength which is higher than a beam of the same length loaded with a constant bending moment along the entire length. This has also been proven by several investigators, such as Madsen 1992. For cases with narrow moment peaks, the load configuration effect may be very significant, since the probability of occurrence of the weakest section at the location of high moment is small (Czmoch et al 1991). 19 Chapter 3. Survey of Literature Generally speaking, there are mainly three factors, which affect test results of lumber strength properties - test zone selection, test span and the grade or quality of material. Therefore, these factors must be considered when comparing strength properties obtained from different test methods. Of the three factors, the most significant factor is the test zone selection, which is significantly different between CEN standard and other standards. It is therefore important to understand the effect of defect location on lumber strength properties. 20 Chapter 4. Database for Properties of Spruce-Pine-Fir 4.0 CANADIAN DATABASE FOR PROPERTIES OF SPRUCE-PINE-FIR Two databases on Canadian Spruce-Pine-Fir dimension lumber were considered in this research: The Canadian Wood Council (CWC) Lumber Properties program In-grade data (Barrett and Lau 1994) and a Council of Forest Industries of BC study on the acceptance of Canadian in-grade data for Europe (Barrett and Lau 1991, Stieda 1990). In the second database which is usually called the CEN test, nominal 38 mm x 89 mm (2x4), 38 mm x 140 mm (2x6), 38 mm x 184 mm (2x8) and 38 mm x 235 mm (2x10) and grade Select Structural (SS), No.l, No.2 and No.3 Canadian Spruce-Pine-Fir kiln dried dimension lumber was evaluated at Forintek Canada Corp. for bending strength and stiffness. 4.1 Introduction for CEN test 4.1.1 Sample Size and Grade The following tables summarize the sample sizes and grades of the lumber which was provided from two mills. Table 4.1 Size 2x4 Samples of Spruce-Pine-Fir Lot A+B SS No.l No.2 No.3 REJ Total Main Series 143 84 45 26 2 300 Augments 2 14 10 0 0 26 Total 145 98 55 26 2 326 Table 4.2 Size 2x6 Samples of Spruce-Pine-Fir Lot A+B SS No.l No.2 No.3 REJ Total Main Series 231 38 30 1 0 300 Augments 3 20 19 0 0 42 Total 234 58 49 1 0 342 21 Chapter 4. Database for Properties of Spruce-Pine-Fir Table 4.3 Size 2x8 Samples of Spruce-Pine-Fir LotA+B SS No.l No.2 No.3 REJ Total Main Series 182 41 63 11 3 300 Augments 32 15 8 0 0 55 Total 214 56 71 11 3 355 Table 4.4 Size 2x10 Samples of Spruce-Pine-Fir Lot A+B SS No.l No.2 No.3 REJ Total Main Series 190 36 56 18 0 300 Augments 11 20 27 0 0 55 Total 201 56 83 18 0 358 Species and grades of all test lumber had been determined, prior to their shipment to Forintek for each 6.1 m long board. This information had been written on each board. In addition, the location of the visually critical section (VCS) and the edge to be stressed in tension during bending had been marked. The visual grade (SS, No.l, No.2, or No.3) was evaluated according to NLGA grading rules. 4.1.2 Moisture Conditioning and Moisture Content of Lumber All lumber had been kiln dried prior to delivery to Forintek. Moisture content, measured with an electric resistance type moisture meter, was marked on the lumber. Some of these marked moisture contents were out of the range of moisture contents specified for the test material, i.e. below 10% or above 15%. The specimen with a moisture content that was too high was air-dried in the laboratory. Low moisture content pieces were conditioned up to the target moisture content range. The moisture content of these pieces, which originally was either too high or too wet, was remeasured with an electric resistance moisture meter prior to E-rating these pieces with the Cook-Bolinders grading machine. Final moisture contents at the time of modulus of rupture determination were obtained from samples cut near the failure region 22 Chapter 4. Database for Properties of Spruce-Pine-Fir 4.1.3 S a m p l e S e l e c t i o n Samples had the strength controlling characteristics be located within a specific portion of the length of the piece. The strength controlling characteristics were considered to be a knot, knot hole, slope of grain, grain deviation, shake or any other defects that would cause failure of this board under a third point bending load. For testing according to ASTM D4761, a span to depth ratio 17 was used, whereas this span ratio was 18 for testing according to CEN/prEN 384. The CEN test also requires that the grade-controlling defect to be evaluated be centered in the test span. In contrast, the ASTM procedure requires that the defect be placed randomly within the test span without bias. The procedure adopted in the test for achieving an unbiased positioning of the defect with respect to the center line of the span, was to displace the defect by a random distance from the center line. Random displacements were rounded to the nearest 3 in (76 mm). 4.1.4 T e s t i n g M e t h o d s The MORCEN and MOECEN were evaluated according to CEN/prEN 384 test procedures and MOEASTM according to ASTM D4761. The following detail methods or standards were used to evaluate the modulus of elasticity of each piece of lumber: 1. Machine stress rating using a Cook-Bolinders grading machine. 2. ASTM D4761. Standard Test Methods for Mechanical Properties of Lumber and Wood-Base Structural Material; Sections 6 to 11, Bending. 3. BS 5820:1979. Determination of Certain Physical and Mechanical Properties of Timber in Structural Sizes; Clause 12, Modulus of Elasticity in Bending. 4. CEN/prEN 384 Structural Timber - Determination of characteristic values of mechanical properties; Clause 5.3.2, Determination of sample mean modulus of elasticity. In addition to the modulus of elasticity, the modulus of rupture was also determined, using CEN/prEN 384; Clause 5.3.1, Determination of sample 5-percentile and Clause 5.4, Strength properties. Density and final moisture content of specimens were determined from a full cross-sectional piece after completion of testing for density determination and ISO 3130 for moisture content determination. 23 Chapter 4. Database for Properties of Spruce-Pine-Fir 4.1.5 Determination of Modulus of Rupture and Modulus of Elasticity CEN/prEN 384 "Structural timber-Determination of characteristic values of mechanical properties" shows the procedures for calculating the Modulus of Rupture (MOR) and Modulus of Elasticity (MOE). M O R Calculation A) . The characteristic value of strength/k (MOR) shall be calculated from the equation: fcflm*K*K (4-D where / 0 0 5 is the mean of the adjusted 5th-percentile values for each sample, weighted according to the number of pieces in each sample. If / 0 0 5 is greater than the lowest adjusted sample value of / 0 0 5 times 1.2 then either the reference population shall be redefined to eliminate the lowest value or / 0 0 5 shall be given the value of 1.2 times the extreme low value of / 0 0 5 ; ks is a factor to adjust for the number of samples and their size. For sample number equals to 3 with the least sample size (n) greater than 150, fcv=0.97 while the least size is greater than 75, ks =0.935; and ks =0.92 if n>50. kv is a factor to allow for the lower variability of / o o s values between samples for machine grade in comparison with visual grades. For all visual grades, kv=\.0. B) . Adjustment Procedure Each sample's fifth percentile strength shall be adjusted as follows: 1) The M O R values are adjusted to 12% M C level by using the 4-term Linear Surface Model (LSM) (J.D. Barrett and W. Lau 1991), and the procedure of doing that is as follows: p2= p,+ b(M 2 - MO b=D 0 +D 1 P 1 5 +D 2 P, 2 5+D 3 P,3S where Pi and P 2 are property values at moisture contents Mj and M 2 24 Chapter 4. Database for Properties of Spruce-Pine-Fir P15 is property value at moisture contents 15% D 0 , Di, D 2 and D 3 are constant terms which are obtained through tests. 2) Lower fifth percentiles of bending strength shall be adjusted to 150 mm depth by dividing by kh =(150/ h)°2 (4-2) where h (mm) is the specimen depth M O E Calcula t ion A) . Determination of the sample mean of modulus of elasticity The sample mean value of modulus of elasticity (E) is calculated from t - n t <«> where N is the number of specimens in the sample and Ei is the value in the i-th value of modulus of elasticity in the range 1 to N. B) . Adjustment Factors Adjustment factors for moisture content came from ASTM D1990 (ASTM 2000 Annual Book of Standards) C) . Determination of the characteristic values of modulus of elasticity After adjusting the value of E for each sample to the reference conditions the characteristic value Erj.mean is calculated from the equation En = J-—L (4-4) where /V. is the number of specimens in sample j ; E} is the mean value of modulus of elasticity for sample j (N/mm2) Determination of Characteristic Density CEN/prEN 384 "The Determination of Characteristic Values of Mechanical Properties and Density for Timber" shows that 25 Chapter 4 . Database for Properties of Spruce-Pine-Fir Po.os = ( p -1.65 »s)kg/m3 (4-5) p0 05 is the sample lower fifth percentile density and p and s are the mean and standard deviation of the densities of all specimens in the sample. Data should be adjusted to 12% moisture content. Characteristic density pk = p where p0 05 is the mean of the p00% values for all samples. 4.2 Results of CEN Test Data on measured and adjusted bending strength, modulus of elasticity and density of Spruce-Pine-Fir are summarized in Table 4.5, Table 4.6 and Table 4.7 Table 4.5 Sample Fifth Percentile Strength Values (MPa) Results: N L G A Grade [Data adjusted to 12% MC) Grade Size M C 'o.05 15%_LSM *0.0512%_LSM 1)+.05 12% n S S 2 x 4 2 8 . 7 8 1 3 . 7 1 2 8 . 2 2 2 8 . 9 5 1.11 2 6 . 0 8 1 4 5 2 x 6 2 5 . 0 9 1 4 . 6 2 2 4 . 9 6 2 5 . 8 4 1 . 0 1 4 2 5 . 4 8 2 3 4 2 x 8 2 1 . 6 5 1 4 . 9 8 2 1 . 6 4 2 2 . 3 8 0 . 9 6 2 3 . 3 2 2 1 4 2 x 1 0 2 1 . 7 5 1 4 . 6 9 2 1 . 6 7 2 2 . 3 4 0 . 9 1 4 2 4 . 4 5 2 0 1 No. 1 2 x 4 2 0 . 4 9 1 3 . 5 3 2 0 . 1 8 2 0 . 5 1 1.11 1 8 . 4 7 9 8 2 x 6 1 6 . 9 2 1 4 . 9 8 1 6 . 9 2 1 7 . 3 6 1 . 0 1 4 1 7 . 1 2 5 8 2 x 8 1 6 . 1 6 1 4 . 7 3 1 6 . 1 3 1 6 . 4 9 0 . 9 6 1 7 . 1 8 5 6 2 x 1 0 1 4 . 0 2 1 4 . 8 6 1 4 . 0 0 1 4 . 2 9 0 . 9 1 4 1 5 . 6 3 5 6 No.2 2 x 4 1 9 . 4 8 1 3 . 5 4 1 9 . 2 0 1 9 . 4 9 1.11 1 7 . 5 6 5 5 2 x 6 1 3 . 5 9 1 4 . 6 1 1 3 . 5 6 1 3 . 8 1 . 0 1 4 1 3 . 6 1 4 9 2 x 8 1 4 . 9 5 1 5 1 4 . 9 5 1 5 . 2 9 0 . 9 6 1 5 . 9 3 7 1 2 x 1 0 1 1 . 8 4 1 4 . 7 5 1 1 . 8 2 1 2 . 0 2 0 . 9 1 4 1 3 . 1 5 8 3 No.3 2 x 4 - 1 3 . 2 7 - - 1.11 - 2 6 2 x 6 - 1 2 . 9 - - 1 . 0 1 4 - 1 2 x 8 - 1 4 . 5 9 - - 0 . 9 6 - 11 2 x 1 0 - 1 4 . 3 8 - - 0 . 9 1 4 - 1 8 26 Chapter 4. Database for Properties of Spruce-Pine-Fir Table 4.6 Sample Mean of Modulus of Elasticity Values (MPa) Results: NLGA Grade (Data adjusted to 12% MC by ASTM 1990) Grade Size MC Emean (ASTM) Emean 12%(ASTM) Emean (CEN) Emean 12%(CEN) n SS 2x4 13.71 10534.8 10820.2 11481.4 11799.5 145 2x6 14.62 10377.9 10809.1 11313.2 11780.8 234 2x8 14.98 9913.0 10369.2 10509.6 10994.8 214 2x10 14.69 9603.9 9993.3 10407.9 10829.2 201 No. 1 2x4 13.53 9566.4 9799.0 8861.1 9078.3 98 2x6 14.98 9306.1 9748.9 • 8653.6 9065.9 58 2x8 14.73 8908.3 9299.8 8682.1 9066.9 56 2x10 14.86 8564.4 8966.5 8273.7 8654.1 56 No.2 2x4 13.54 9117.1 9333.1 7999.8 8187.7 55 2x6 14.61 9391.7 9779.3 9242.0 9626.9 49 2x8 15.00 9018.0 9451.6 9121.4 9561.8 71 2x10 14.75 8432.2 8801.0 8855.0 9234.5 83 No.3 2x4 13.27 8700.0 8889.1 6867.0 7027.2 26 2x6 12.90 5791.0 5870.6 5880.0 5960.9 1 2x8 14.59 8912.7 9287.2 9770.3 10175.4 11 2x10 14.38 7434.2 7692.1 7442.2 7734.4 18 Table 4.7 Sample Density Values (kg/m3) Results: NLGA Grade (Data adjusted to 12% MC) Grade Size P s.d. * Po.05 Po.05 n SS 2x4 477 43 403 406 142 2x6 460 44 393 387 234 2x8 442 46 368 366 214 2x10 433 44 364 360 202 No. 1 2x4 468 47 391 390 98 2x6 459 47 •377 381 58 2x8 444 44 372 371 56 2x10 433 49 347 352 44 No.2 2x4 457 44 390 384 55 . 2x6 469 55 369 378 49 2x8 454 49 372 373 71 2x10 432 40 367 366 85 No.3 2x4 476 52 - 390 26 2x6 428 - -- - 1 2x8 461 67 - 350 11 2x10 434 52 - 348 18 27 Chapter 4. Database for Properties of Spruce-Pine-Fir where /0.05 is the fifth percentile bending strength as measured. /0.05 1 5 % _ L S M is the fifth percentile bending strength adjusted to 15% MC. /0.05 ! 2 % _ L S M is the fifth percentile bending strength adjusted to 12% MC. /+o.o512% is the fifth percentile bending strength adjusted to 150 mm depth. Emean (ASTM) is the mean value of modulus of elasticity by ASTM test method as measured. Emean 12%(ASTM) is the mean value of modulus of elasticity by ASTM test method adjusted to 12% MC. Emean (CEN) is the mean value of modulus of elasticity by C E N test method as measured. Emean 12%(CEN) is the mean value of modulus of elasticity by CEN test method adjusted to 12% MC. p005 is sample density value derived by using equation (4-5) P005 is sample fifth percentile density. 4.3 Comparison Analysis between CWC Test and CEN Test In the following comparisons, the MOR data of the Spruce-Pine-Fir lumber tested according to the ASTM method are from the CWC test database (Barrett and Lau 1994) and all other properties such as MOR and MOE according to CEN testing procedures and MOE based on ASTM method are obtained from CEN test database (Barrett and Lau 1991,Stieda 1990). 4.3.1 MOR Comparison Figure 4.1 shows the MOR comparison between ASTM tests and CEN tests for 2x4 samples. The remainders of the figures for other samples are in Appendix A. Figure 4.2 shows the MOR differences from 2.5-percentile to 50-percentile bending strength for 2x4 samples. The remainders of the figures for other samples are in Appendix B. 4.3.2 MOE Comparison Figure 4.3 shows the MOE comparison between ASTM tests and CEN tests for 2x4 samples. The rest of the figures for other samples are illustrated in appendix C. Figure 4.4 28 Chapte r 4. Database for Proper t ies o f S p r u c e - P i n e - F i r shows the M O E differences from 2.5-percentile to 50-percentile strength for 2x4 samples. The figures for the other samples are illustrated in Appendix D. CWC vs CEN(4ALL_SS_12%MC) 40 60 80 MOR (MPa) 100 120 1.0 f 0.8 0 6 | 0.2 CWC vs CEN(4ALL_N1_12%MC) i C W C C E N 40 60 80 MOR (MPa) 100 120 1.0 0.8 0.6 0 4 0.2 0 0 CWC vs CEN(4ALL_N2_12%MC) & — » » 1 / / / « c w c » CEN 1 \ 40 60 80 MOR (MPa) 100 120 CWC vs CEN(4ALL_N3_12%MC) C W C C E N 40 60 80 MOR (MPa) 100 120 Fig. 4.1 Comparison of MOR between C E N and CWC Tests CWC vs CEN(4ALL_SS_12%MC) 0 5 10 15 20 25 30 35 40 45 50 Percenti le 50 45 IS 40 | 35 0C 30 O S 25 20 15 CWC vs CEN(4ALL_N1_12%MC) 1^ -*-cwc ~"—~i—\—i—i—i—i— — • — C E N 0 5 10 15 20 25 30 35 40 45 50 Percenti le 50 45 V 40 I 35 g 30 S 25 20 15 CWC vs CEN(4ALL_N2_12%MC) -CWC CEN 0 5 10 15 20 25 30 35 40 45 50 Percenti le CWC vs CEN (4ALL_N3_12%) 0 5 10 15 20 25 30 35 40 45 50 Percenti le Fig. 4.2 M O R Differences from 2.5 t h to 50 t h - Percentile Bending Strength 29 Chapte r 4. Database for Proper t ies o f S p r u c e - P i n e - F i r ASTM vs CEN(4ALL_SS_12°/cMC) J3 n JI o £ * 3 £ 3 u 0 8 0 6 0 2 0 5000 7000 9000 11000 13000 15000 17000 19000J MOE(MPa) ASTM vs CEN(4ALL_N1_12°/cMC) 7000 9000 11000 MOE(MPa) 13000 15000 1 0.8 0 6 ASTM vs CEN(4ALL_N2_12°/cMC) 3 CJ 0.2 4 ASTM CEN 3000 5000 7000 9000 11000 13000 15000 MOE(MPa) ASTM vs CEN(4ALL_N3_12°/cMC) 1 o <c -S 2 o o. u = o. a "3 E 0. 3 U a § c u a i i O A ~ ^ * ASTM . CEN , 0 A » 1000 3000 5000 7000 9000 11000 13000 15000| MOE(MPa) Fig. 4.3 Comparison of M O E between C E N and A S T M Tests 12000 _ 11000 | 10000 O 9000 E 8000 7000 ASTM vsCEN(4ALL_SS_12%MC) —*— ASTM j — • — C E N 0 5 10 15 20 25 30 35 40 45 50 Percentile ASTM vs CEN(4ALL_N1_12%MC) 0 5 10 15 20 25 30 35 40 45 50 Percentile ASTM vs CEN(4ALL_N2_12%MC) 10000 9000 --- 8000 5 7000 g" 6000 " 5000 4000 3000 —*—ASTM — CEN 0 5 10 15 20 25 30 35 40 45 50 Percentile Fig. 4.4 M O E Differences from 2.5 t h to 50 t h - Percentile Stiffness 30 Chapter 4. Database for Properties of Spruce-Pine-Fir 4.3.3 Density Comparison Density comparison for Canadian lumber Spruce-Pine-Fir between CWC tests and CEN tests can be seen in Table 4.8. Table 4.8 Characteristic Densities for Canadian Lumber Spruce-Pine-Fir Summary of Density for NLGA Lumbers (Data adjusted to 12% MC) Species Grade CWC Test Density pk CEN Test Density pk Identification (kg/m3) (kg/m3) S - P - F SS 358 377 No.1 372 377 No.2 361 374 No.3 N/A 368 31 Chapte r 5. E q u i v a l e n c e o f Dif ferent Standards 5.0 EQUIVALENCE OF DIFFERENT STANDARDS 5.1 Equivalence Model for MOR Two comparisons have been developed to obtain the equivalence model for MOR in this study. One is the comparison of the corresponding values from 2.5th-percentile strength to 50 th -percentile strength and the other is the comparison of the 5 t h -percentile strength only. In the first comparison, the ratios between the MOR data obtained by ASTM and CEN methods were first established at 20 different percentile levels between 2.5th and 50 th percentile for 4 grades (see Figure 4.2, Figure B . l and Figure B.2) and then mean ratios for each grade were calculated. In the second comparison, all calculations are only at the 5 t h percentile bending strength. For clear wood, the ratios should be taken as unity. The detailed comparisons are shown in Table 5.1 and Figure 5.1. In the second comparison, the CWC/CEN strength ratio 1.14 for No.2 samples does not follow the whole trend because the sample sizes for these samples are not big enough. Table 5.1 Comparison Ratios for Modulus of Rupture (MOR) Averaging ratios of 20 va ues from 2.5%tile - 50%tile Strength Grade (2x4) Samples (2x8) Samples (2x10) Samples Average Ratio (CEN/CWC) Inverse Ratio (CWC/CEN) N3 0.525 1.086 0.766 0.792 1.262 N2 0.736 0.804 0.921 0.820 1.219 N1 0.751 0.876 0.825 0.818 1.223 SS 0.862 0.912 0.953 0.909 1.100 CL 1.000 1.000 1.000 1.000 1.000 Averaging ratios of only 5 - percentile S t r e n g t h N3 0.407 0.618 0.838 0.621 1.611 N2 0.889 0.844 0.899 0.877 1.140 N1 0.714 0.909 0.838 0.820 1.219 SS 0.872 0 .913 1.057 0.948 1.055 CL 1.000 1.000 1.000 1.000 1.000 Strength Conversion Factors(12%MC) 1.0 0.9 o 5 0.8 o I 0.7 o 0.6 0.5 - ALL_Mean -5% only N3 N2 N1 Grade S S Strength Conversion Factors(12%MC) 1.7 Z 1.5 HI O 1.4 | 1.3 O 1.2 1.1 1.0 —*—ALL^Mean \ \ — * — 5 % only •\ \ V — ^ N3 M2 N1 Grade S S CL Fig. 5.1 Converted Factors 32 Chapter 5. Equivalence of Different Standards 5.2 Equivalence Model for MOE The mean and 5-percentile values are selected simultaneously for developing the equivalence model for M O E . All data are shown in Table 5.2 and the relationship between M O E A S T M and M O E C E N is shown in Figure 5.2 Table 5.2 Mean and 5-Percentile MOE Values (MPa) Results: C E N Test Data (Data adjusted to 12% M C ) Grade Size M O E A S T M S% MOEASTM Mean MOECEN S% MOECEN Mean n SS 2x4 8463.51 10820.17 8433.38 11799.48 145 2x6 8475.26 10809.15 8330.25 11780.82 234 2x8 7844.81 10369.21 7614.05 10994.78 214 2x10 7828.98 9993.32 7991.27 10829.17 201 No. 1 2x4 7675.50 9799.04 5792.33 9078.33 98 2x6 6771.53 9748.93 5764.82 9065.93 58 2x8 7386.54 9299.77 6680.57 9066.88 56 2x10 5958.87 8966.52 5836.78 8654.10 56 No.2 2x4 6937.27 9333.14 3987.82 8187.71 55 2x6 6666.86 9779.31 5423.08 9626.86 49 2x8 6717.70 9451.64 5155.53 9561.81 71 2x10 6654.58 8800.99 5792.12 9234.49 83 No.3 2x4 - 8889.07 - 7027.25 26 2x6 - 5870.63 - 5960.85 1 2x8 - 9287.23 - 10175.36 11 2x10 - 7692.11 - 7734.37 18 M O E ( C E N v s A S T M ) 13000 -] 3000 A , , 1 , 1 4000 6000 8000 10000 12000 M O E _ A S T M ( M P a ) Fig. 5.2 Regression Relationship between M O E A S T M and M O E C E N 33 Chapter 5. Equivalence of Different Standards 5.3 Adjustment Factors From above analysis, the adjustment factors as 1.05, 1.2, 1.2 and 1.25 at grade Select Structural, No.l , No.2 and No.3 are reasonable for the conversion from M O R A S T M to MORCEN- For example, one would reduce the M O R values tested according to the ASTM method by 1.2 to convert the data to CEN basis for NLGA grade No.2 lumber. As to MOE conversion, the following model should be used MOECEN=-3156.5+1.3287 M O E A S T M (5-1) 5.4 Equivalence Stress Classes for Canadian Dimension Lumber 5.4.1 Equivalence to CEN Grades To adjust the Canadian dimension lumber strength data for use in Europe, the bending strength and modulus of elasticity data for Douglus-fir, Hem-Fir and Spruce-Pine-Fir (es, 2x4, 2x8 and 2x10) was converted to a CEN basis.. The initial data such as bending strength ( f 0 . 0 5 15%. fo.05 12%) and stiffness (MOE15%) are based on the CWC database and the adjustment factors come from section 5.3. All adjustment results are shown in Table 5.3 to 5.8 Table 5.3 Adjustment Bending Strength for Canadian Douglas Fir-Larch (MPa) In-grade DF MOR (Data adjusted to 12% MC) Grade Size f<).05 15% fo.05 12% Adjustment Factor f<) .05 12% kn f<> .0512% /0.05 n SS 2x4 35.62 37.77 1.05 35.97 1.11 32.41 27.39 370 2x8 25.53 26.84 1.05 25.56 0.96 26.63 373 2x10 21.21 22.22 1.05 21.16 0.914 23.15 372 1+BTR 2x4 30.3 32.05 1.10 29.14 1.11 26.25 22.30 370 2x8 22.04 23.11 1.10 21.01 0.96 21.88 385 2x10 18.23 19.05 1.10 17.32 0.914 18.95 389 No.1 2x4 25.83 27.16 1.20 23.62 1.11 21.28 17.96 99 2x8 18.10 18.91 1.20 16.44 0.96 17.13 83 2x10 14.68 15.29 1.20 13.30 0.914 14.55 76 No.2 2x4 20.51 21.47 1.20 18.67 1.11 16.82 15.29 370 2x8 15.75 16.43 1.20 14.29 0.96 14.88 370 2x10 14.32 14.91 1.20 12.97 0.914 14.19 374 No.3 2x4 13.95 14.52 1.25 12.63 1.11 11.37 9.93 150 2x8 8.94 9.26 1.25 8.05 0.96 8.39 149 2x10 10.16 10.54 1.25 9.17 0.914 10.03 150 Note: an adjustment factor 1.1 is used for grade 1+Better lumber 34 Chapter 5. Equivalence of Different Standards Table 5.4 Adjustment Bending Strength for Canadian Hem-Fir (MPa) In-gradi 3 H F I WOR (Data adjusted to 12% MC) Grade Size f<).05 15% frj.05 12% Adjustment Factor •0 .05 12% k h '0 .05 12% /o.05 n S S 2x4 36.66 38.90 1.05 37.05 1.11 33.38 27.18 381 2x8 24.51 25.74 1.05 24.51 0.96 25.54 382 2x10 20.73 21.70 1.05 20.67 0.914 22.61 379 1+BTR 2x4 30.48 32.26 1.10 29.33 1.11 26.42 22.76 392 2x8 21.57 22.61 1.10 20.55 0.96 21.41 397 2x10 19.69 20.60 1.10 18.73 0.914 20.49 398 No.1 2x4 23.5 24.66 1.20 21.44 1.11 19.32 16.97 104 2x8 17.09 17.84 1.20 15.51 0.96 16.16 60 2x10 13.48 14.02 1.20 12.19 0.914 13.34 54 No.2 2x4 25.97 27.31 1.20 23.75 1.11 21.39 18.44 380 2x8 18.64 19.48 1.20 16.94 0.96 17.64 402 2x10 16.47 17.18 1.20 14.94 0.914 16.34 385 No.3 2x4 19.46 20.36 1.25 17.70 1.11 15.95 13.13 170 2x8 12.65 13.15 1.25 11.43 0.96 11.91 158 2x10 11.47 11.92 1.25 10.37 0.914 11.34 159 Table 5.5 Adjustment Bending Strength for Canadian Spruce-Pine-Fir (MPa) In-grade S P F M O R (Data adjusted to 12% MC) Grade Size •0.05 15% •0.05 12% Adjustment Factor fo .05 12% k h '0 .05 12% /o.05 n S S 2x4 31.6 33.41 1.05 31.82 1.11 28.67 24.84 441 2x8 22.72 23.83 1.05 22.70 0.96 23.64 444 2x10 20.38 21.33 1.05 20.31 0.914 22.23 440 1+BTR 2x4 29.5 31.11 1.10 28.28 1.11 25.48 22.18 458 2x8 21.15 22.11 1.10 20.10 0.96 20.94 454 2x10 19.26 20.15 1.10 18.32 0.914 20.04 440 No.1 2x4 27.81 29.29 1.20 25.47 1.11 22.95 19.52 123 2x8 17.38 18.14 1.20 15.77 0.96 16.43 84 2x10 17.06 17.81 1.20 15.49 0.914 16.94 63 No.2 2x4 21.55 22.57 1.20 19.63 1.11 17.68 16.07 440 2x8 17.24 17.80 1.20 15.48 0.96 16.12 986 2x10 14.46 15.06 1.20 13.10 0.914 14.33 441 No.3 2x4 16.2 16.90 1.25 14.70 1.11 13.24 11.41 180 2x8 12.84 13.35 1.25 11.61 0.96 12.09 200 2x10 9.31 9.65 1.25 8.39 0.914 9.18 210 35 Chap te r 5. E q u i v a l e n c e o f Dif ferent Standards Table 5.6 Adjustment Bending Stiffness for Canadian Douglas Fir-Larch (MPa) In-grade D F M O E (Data a d j u s t e d to 12% M C ) Grade Size M O E 1 5 % M O E 1 2 % MOEcONVERSION MOECEN n S S 2x4 12204 12783 13827 14808 370 2x8 13603 14247 15774 373 2 x 1 0 12914 13526 14815 372 1+BTR 2x4 11659 12211 13068 14305 370 2x8 13031 13648 14978 385 2 x 1 0 12914 13526 14815 3 8 9 No.1 2x4 10335 10824 11226 11410 99 2x8 10582 11083 11570 8 3 2 x 1 0 10514 11012 11475 76 No.2 2x4 10687 11193 11716 12176 370 2x8 11328 11864 12608 370 2 x 1 0 11038 11561 12204 374 No.3 2x4 9749 10211 10410 10983 150 2x8 10073 10550 10861 149 2 x 1 0 10659 11164 11677 150 Table 5.7 Adjustment Bending Stiffness for Canadian Hem-Fir (MPa) In-grade H F M O E (Data a d j u s t e d to 12% M C ) Grade Size M O E 1 5 % M O E ! 2 % MOEcONVERSION MOECEN n S S 2x4 11700 12247 13117 13408 381 2x8 12135 12703 13722 382 2x10 11893 12449 13385 3 7 9 1+BTR 2x4 11425 11960 12734 13116 392 2x8 11969 12529 13491 397 2 x 1 0 11700 12247 13117 398 No.1 2x4 10549 11043 11516 11510 104 2x8 10452 10941 11381 60 2 x 1 0 10639 11137 11641 54 No.2 2x4 10797 11302 11861 12177 380 2x8 11225 11750 12456 402 2x10 11039 11556 12197 3 8 5 No.3 2x4 9915 10379 10634 10659 170 2x8 9984 10451 10730 158 2x10 9901 10364 10615 159 Chapter 5. Equivalence of Different Standards Table 5.8 Adjustment Bending Stiffness for Canadian Spruce-Pine-Fir (MPa) In-grade S P F M O E (Data a d j u s t e d to 12% M C ) Grade Size M O E 1 5 % M O E 1 2 % MOEcoNVERSION M O E c E N n S S 2 x 4 1 0 7 3 0 1 1 2 3 2 1 1 7 6 8 11383 4 4 1 2 x 8 1 0 4 2 0 1 0 9 0 8 1 1 3 3 6 4 4 4 2 x 1 0 1 0 2 1 0 1 0 6 8 8 1 1 0 4 4 4 4 0 1+BTR 2 x 4 1 0 4 5 0 1 0 9 3 9 1 1 3 7 8 11074 4 5 8 2 x 8 1 0 2 2 0 1 0 6 9 8 1 1 0 5 8 4 5 4 2 x 1 0 1 0 0 2 0 1 0 4 8 9 1 0 7 8 0 4 4 9 No.1 2 x 4 9 7 0 0 1 0 1 5 4 1 0 3 3 5 10100 1 2 3 2 x 8 9 4 8 0 9 9 2 4 1 0 0 2 9 8 4 2 x 1 0 9 2 7 0 9 7 0 4 9 7 3 7 6 3 No.2 2 x 4 9 4 9 0 9 9 3 4 1 0 0 4 3 10175 4 4 0 2 x 8 9 7 5 0 1 0 2 0 6 1 0 4 0 5 9 8 6 2 x 1 0 9 3 1 0 9 7 4 6 9 7 9 3 4 4 1 No.3 2 x 4 9 3 2 0 9 7 5 6 9 8 0 6 9241 1 8 0 2 x 8 8 9 6 0 9 3 7 9 9 3 0 6 2 0 0 2 x 1 0 8 5 2 0 8 9 1 9 8 6 9 4 2 1 0 where f 0.05 12% is the sample fifth percentile bending strength after test method adjustment. f 0.05 12% is the sample fifth percentile bending strength after size adjustment. / 0 0 5 is the characteristic bending strength of that grade Table 5.9 shows the final converted strength and stiffness values and stress class grades for Canadian commercial lumber. The characteristic values of bending strength M O R C E N are calculated according to equation (4-1) and M O E C E N comes from equation (4-4). 37 Chapter 5. Equivalence of Different Standards Table 5.9 CEN Strength Classes for NLGA Lumber Using CWC Data Grade M O R c E N (MPa) MOECEN (MPa) Density p k (kg/m 3) Corresponding C E N Strength Class Douglas - Fir S S 26.56 14808 424 C27 1+BTR 21 .63 14305 N / A C20 No.1 16.79 11410 421 C16 No.2 14.83 12175 411 C14 No.3 9.64 10983 N / A < C14 Hem -•Fir S S 26 .37 13408 391 C27 1+BTR 22.07 13116 N / A C22 No.1 15.61 11510 382 C14 No.2 17.88 12177 388 C16 No.3 12.74 10659 N / A <C14 Spruce - Pine - Fir S S 24.10 11383 358 C24 1+BTR 21 .52 11074 N / A C20 No.1 17.96 10100 372 C16 No.2 15.58 10175 361 C14 No.3 11.06 9241 N / A < C14 5.4.2 Equivalence to ISO Grades A uniform adjustment factor l .0 is suitable for obtaining the corresponding ISO bending strength for Canadian dimension lumber except for grade No.3 samples. In that situation, a factor 1.15 is used, i.e., MOR 1 So is equal to MORASTM times 1.15. No adjustment is needed for the MOE equivalence The final converted strength and stiffness values and stress class grades for Canadian commercial lumber according to ISO standard are shown in Table 5.10. The initial data such as bending strength (f 0. 0 515%, f0.os 12%) and stiffness (MOEi5%) are based on the CWC database and all adjustment results are shown in Appendix Table E. I to E.6. 38 Chapter 5. E q u i v a l e n c e o f Dif ferent Standards Table 5.10 ISO Strength Classes for NLGA Lumber Using CWC Data Grade MOR l s o M O E i s o Density p k Corresponding ISO (MPa) (MPa) (kg/m3) Strength Class Douglas - Fir SS 28 .20 13520 424 S27 1+BTR 23 .95 13141 N / A S22 No.1 21 .33 10962 421 S20 No.2 17.09 11539 411 S16 No.3 12.73 10641 N / A S12 Hem -Fir SS 28.00 12466 391 S27 1+BTR 24.46 12246 N / A S24 No.1 19.02 11038 382 S18 No.2 20.68 11540 388 S20 No.3 17.06 10397 N / A S16 Spruce - Pine - Fir SS 25 .53 10942 358 S24 1+BTR 23.87 10710 N / A S22 No.1 21 .93 9977 372 S20 No.2 18.08 10033 361 S18 No.3 14.80 9330 N / A S14 39 Chapter 6. Conclusions and Recommendations 6.0 CONCLUSIONS AND RECOMMENDATIONS 6.1 Conclusions 1. International harmonization criteria are required for comparison of national standards for timber testing and stress class. Such criteria will allow materials property data collected using different test standards to be compared on a common basis. 2. Producers, users and specifies of wood based materials are becoming impatient with proliferation of uncoordinated national standards for testing, evaluation and design in wood products. So it is now incumbent on the wood engineering community to support the development of internationally acceptable criteria for testing and evaluation of wood products design properties. 3. Models of equivalence between CSA and CEN / ISO standards and the corresponding strength grades in the three standards have been developed for Canadian dimension lumber. 4 It is important to work with grade and code agencies in the timber importing regions to ensure all commercial species are treated in a technically equitable basis. 6.2 Recommendations 1 More detailed work is needed in the field of property relationship 2 More international standard equivalence work for testing method and stress class is needed in the near future such as the in-grade testing method for Chinese and Japanese wood industries. 3 Due to the limitation data of CEN test and the fact that the sample sizes of some test cells are very low, the interpretation of the statistical values must be taken with caution. 40 References REFERENCES 1. A S T M D 198 Standard Method of Static Tests of Lumber in Structural Sizes 2. A S T M D 1990 Standards Practice for Establishing Allowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-Size Specimens 3. A S T M D 2915 Standard Practice for Evaluation Allowable Properties for Grades of Structural Lumber 4. A S T M D 4761 Standard Test Methods for Mechanical Properties of Lumber and Wood-Base Structural Material 5. A S / N Z S 4603:1992 Timber-Stress Graded - In-grade Strength and Stiffness Evaluation 6. C E N / prEN384:2000 Structural Timber - Determination of Characteristic Values of Mechanical Properties and Density of Timber 7. C E N / prEN338:2000 Structural Timber - Strength Classes 8. C S A 086-01 Engineering Design in Wood 9. GB50005-2003 - Code for Design of Timber Structures 10. G B / T 50329 -2002 - Standard for Testing Methods of Timber Structures 11. JIS-Z2101 -1994 Methods of Testing for Wood 12. Japanese Draft Standard: Evaluation Standard for Design Strength of Lumber, 1996 13. Barrett, J .D. and F. Lam 1994 Factor Affecting the Strength of Structural Timber, Proceeding, Pacific Timber Eng. Conf , Cold coast, Australia, 14. Barrett, J .D. and W . Lau 1994 Canadian Lumber Properties, Canadian Wood Council , Ottawa, Canada 15. Barrett, J.D. and W . Lau 1991 Acceptance of In-grade Data in Europe, Research Report, University of British Columbia, Vancouver, Canada 16. Barrett, J.D. and Fewell, A .R . , "Size Factors for the Bending and Tension Strength of Structural Lumber", Proceeding of CIB-W18 - Timber Structure, Meeting 23, Paper 23-10-3, Lisbon, Portugal, 1990 17. Cheung, K . 1991 European C E N / U . S . In-grade Comparison Study, Research Report, Western Wood Products Association, Portland, U S A 41 References 18. Czmoch, I., S. Thelandersson and H.J. Larson 1991 Effect of Within Member Variability on Bending Strength of Structural Timber, Proceeding of the Conference of CIB-W18, Oxford, England 19. Green, D.W., and Evans, J.W., "Mechanical Properties of Visually Graded Lumber", Nat. Tech. Inform. Serv. Publ., Vol. 1, 1989, No. PB-88-159-389 20. Isaksson, T. and S: Thelandersson 1995 Effect of Standard, Length and Load Configuration on Bending Strength of Structural Timber, Proceeding of the Conference of CIB-W 18, Copenhagen, Denmark 21. Isaksson, T. and S. Thelandersson 1996 Variability and Prediction of Bending Strength of Timber, Proceedings of International Wood Engineering Conference, New Orleans, USA 22. Lam, F. 2003 Wood Products Stress Class System - Discussion Paper, University of British Columbia, Vancouver, Canada 23. Leicester, R., H . O. Breitinger and H. F. Fordham 1996 Equivalence of In-grade Testing Standards, Proceeding of the Conference of CIB-W 18, Bordeaux, France 24. Madsen, B. 1992 Structural Behavior of timber, Timber Engineering LTD, Vancouver, Canada 25. Rouger, F., and Barrett, J.D., "Size Effects in Timber", Grundlagen Entwicklungen Erganzungen, Step3, pp. 3/1-3/24, Diisseldorf, Germany, 1995 26. Stieda, C .K.A. 1990 Bending Strength and Stiffness of SPF Lumber in 2x4, 2x6, 2x8 and 2x10 Sizes Graded According to BSI and N L G A Grading Rules, Research Report, Forintek, Vancouver, Canada 42 Appendix Appendix A MOR Comparison CWC vs CEN(8ALL_SS 12°/<MC) CWC vs CEN(8ALL_N1_12%MC) Fig. A. I Comparison of MOR between CEN and CWC Tests for 2x8 Lumber 1 0 0.8 0.6 0.4 0 2 0 0 CWC vs CEN(10ALL^SS_12%MC) * CWC : CEN CWC vs CEN(10ALL_N1_12°/dVtC) 1.0 | | 0.8 0.6 0.4 40 60 MOR (MPa) i 0.2 U a / i f • M IF A CWC o CEN i 40 60 MOR (MPa) 80 1.0 0 8 0 6 0.4 0.2 0.0 CWC vs CEN(10ALL„N2 J2°/dvlC) L CWC = CEN —, 40 60 MOR (MPa) 80 I oc I 10 3 0.8 J9 _2 § 0.2 u CWC vs CEN(10ALL_N3_12%MC) l—* o f • / of A CWC = CEN 20 40 MOR (MPa) 80 Fig. A.2 Comparison of MOR between CEN and CWC tests for 2x10 Lumber 43 Appendix Appendix B MOR Difference 0 5 10 15 20 25 30 35 40 45 50 Percentile CWC vs CEN(8ALL_N2_12%MC) 0 5 10 15 20 25 30 35 40 45 50 Percentile 3b 30 I " O 2 0 s 15 CWC vs CEN(8ALL_N1 J2%MC) i CWC - — CEN 30 „ 25 to Q. cr O •o 0 5 10 15 20 25 30 35 40 45 50 Percentile CWC vs CEN (8ALL_N3_12%) - * — C W C - — C E N 0 5 10 15 20 25 30 35 40 45 50 Percentile Fig. B. 1 MOR differences from 2.5 to 50 - percentile strength for 2x8 Lumber CWC vs CEN(10ALL_SS_12%MC) 0 5 10 15 20 25 30 35 40 45 50 P e r c e n t i l e 35 CWC vs CEN(10ALL_N1_12%MC) a a x 0 5 10 15 20 25 30 35 40 45 50 P e r c e n t i l e 0 5 10 15 20 25 30 35 40 45 50 Percentile 5 10 15 20 25 30 35 40 45 50 Percentile Fig. B.2 MOR differences from 2.5 to 50 - percentile strength for 2x10 Lumber 44 Appendix Appendix C MOE Comparison ASTM vs CEN(8ALL_SS_12°/JV1C) • 1 i 0 8 rob 0 6 a > 0.4 — 3 1 0.2 u 0 jjfff——, , . _, 4 ASTM = CEN 5000 7000 9000 11000 13000 15000 17000 19000 MOE(MPa) ASTM vs CEN(8ALL_N2_12°/cMC) _j u.o j A 2 0.6 0. I 0.4 3 | 0.2 U -At . ASTM CEN 4000 6000 8000 MOE(MPa) l_ 10000 12000 14000 ASTM vs CEN(8ALL_N1_12°/dv1C) •£ O.i S ~ 0.4 • 3 E 0.2 3 U J r A ASTM o CEN 5000 7000 9000 11000 MOE(MPa) 13000 15000 ASTM vs CEN(8ALL_N3_12°/<MC) 0. ' (i •S 0.4 ™ 3 £ 0 2 3 u 0 6000 _ AASTM • CEN 10000 12000 14000 MOE(MPa) Fig. C. 1 Comparison of MOE between CEN and ASTM Tests for 2x8 Lumber ASTM vs CEN(10ALL_SS_12%MC) 1 0.8 0.6 0.4 0.2 0 M A ASTM « CEN / 6000 8000 10000 12000 14000 16000 18000 MOE(MPa) ASTM vs CEN(1 OALL N2 12°/tMC) ASTM CEN 4000 6000 8000 10000 12000 14000 16000 MOE(MPa) ASTM vs CEN(10ALL_N1_12°/<MC) A tP A ASTM » CEN 9000 11000 13000 MOE(MPa) ASTM vs CEN(10ALL_N3_12o/cMC) A o _ » A A J 0 A s A n A A ASTM o A o A a A » CEN 0.2 0 2000 4000 6000 8000 10000 12000 14000 16000 MOE(MPa) Fig. C.2 Comparison of MOE between CEN and ASTM Tests for 2x10 Lumber 45 Appendix Appendix D MOE Difference 11000 — 10000 CL | 9000 o s 8000 7000 ASTM vsCEN(8ALL_SS_12%MC) - * - A S T M ~~~CEN 0 5 10 15 20 25 30 35 40 45 50 Percentile ASTM vs CEN(8ALL_N2_12%MC) 10000 9000 Pa) 8000 us 7000 c 3 6000 5000 4000 0 5 10 15 20 25 30 35 40 45 50 Percentile ASTM vs CEN(8ALL_N1_12%MC) 9000 8000 re 0. | 7000 o —1— 5000 -CEN 0 5 10 15 20 25 30 35 40 45 50 Percentile Fig. D.l MOE Differences from 2.5 to 50 - Percentile Strength for 2x8 Lumber ASTM vs CEN(10ALL_SS_12%MC) 11000 0 5 10 15 20 25 30 35 40 45 50 Percentile ASTM vs CEN(10ALL_N1_12%MC) 9000 0 5 10 15 20 25 30 35 40 45 50 Percentile ASTM vs CEN(10ALL_N2_12%MC) 0 5 10 15 20 25 30 35 40 45 50 55 Percentile Fig. D.2 MOE Differences from 2.5 to 50 - Percentile Strength for 2x10 Lumber 46 Appendix Appendix E Adjustment Properties to ISO Standard for NLGA Lumber Table E.l Adjustment Bending Strength for Canadian Douglas Fir-Larch (MPa) In-grade DF MOR (Data adjusted to 12% MC) Grade Size f<>.05 15% f<).05 12% Adjustment Factor 0^ .05 12% kh fo .05 12% fo.as n SS 2x4 35.62 37.65 1.00 37.65 1.11 33.92 28.52 370 2x8 25.53 26.58 1.00 26.58 0.96 27.69 373 2x10 21.21 21.93 1.00 21.93 0.914 23.99 372 1+BTR 2x4 30.3 31.78 1.00 31.78 1.11 28.63 24.23 370 2x8 22.04 22.82 1.00 22.82 0.96 23.77 385 2x10 18.23 18.75 1.00 18.75 0.914 20.52 389 No.1 2x4 25.83 26.90 1.00 26.90 1.11 24.24 21.58 99 2x8 18.1 18.61 1.00 18.61 0.96 19.39 83 2x10 18.23 18.75 1.00 18.75 0.914 20.52 76 No.2 2x4 20.51 21.18 1.00 21.18 1.11 19.08 17.29 370 2x8 15.75 16.13 1.00 16.13 0.96 16.81 370 2x10 14.32 14.63 1.00 14.63 0.914 16.01 374 No.3 2x4 13.95 14.25 1.15 16.38 1.11 14.76 12.87 150 2x8 8.94 9.07 1.15 10.43 0.96 10.86 149 2x10 10.16 10.32 1.15 11.87 0.914 12.98 150 Table E.2 Adjustment Bending Strength for Canadian Hem-Fir (MPa' In-grade HF MOR (Data adjusted to 12% MC) Grade Size f<).05 15% fo.05 12% Adjustment Factor Io .05 12% kh fo .05 12% /(I.05 n SS 2x4 36.66 38.81 1.00 38.81 1.11 34.96 28.32 381 2x8 24.51 25.47 1.00 25.47 0.96 26.54 382 2x10 20.73 21.41 1.00 21.41 0.914 23.43 379 1+BTR 2x4 30.48 31.98 1.00 31.98 1.11 28.81 24.74 392 2x8 21.57 22.31 1.00 22.31 0.96 23.24 397 2x10 19.69 20.30 1.00 20.30 0.914 22.21 398 No.1 2x4 23.5 24.38 1.00 24.38 1.11 21.97 19.24 104 2x8 17.09 17.55 1.00 17.55 0.96 18.28 60 2x10 13.48 13.76 1.00 13.76 0.914 15.05 54 No.2 2x4 25.97 27.06 1.00 27.06 1.11 24.37 20.92 380 2x8 18.64 19.19 1.00 19.19 0.96 19.99 402 2x10 16.47 16.89 1.00 16.89 0.914 18.48 385 No.3 2x4 19.46 20.06 1.15 23.07 1.11 20.78 17.06 170 2x8 12.65 12.89 1.15 14.83 0.96 15.45 158 2x10 11.47 11.67 1.15 13.42 0.914 14.68 159 47 Appendix Table E.3 Adjustment Bending Strength for Canadian Spruce-Pine-Fir (MPa) In-grad e SPF M O R (Data adjusted to 1 2 % M C ) Grade Size fo.05 15% ^0.05 12% Adjustment Factor •0 .05 12% kh fo .05 12% /o.05 n SS 2 x 4 3 1 . 6 3 3 . 2 1 1 .00 3 3 . 2 1 1.11 2 9 . 9 2 25.82 4 4 1 2 x 8 2 2 . 7 2 2 3 . 5 5 1 .00 2 3 . 5 5 0 . 9 6 2 4 . 5 3 4 4 4 2 x 1 0 2 0 . 3 8 2 1 . 0 4 1 .00 2 1 . 0 4 0 . 9 1 4 2 3 . 0 2 4 4 0 1 + B T R 2 x 4 2 9 . 5 3 0 . 9 0 1 .00 3 0 . 9 0 1.11 2 7 . 8 4 24.14 4 5 8 2 x 8 2 1 . 1 5 2 1 . 8 6 1 .00 2 1 . 8 6 0 . 9 6 2 2 . 7 7 4 5 4 2 x 1 0 1 9 . 2 6 1 9 . 8 5 1 .00 • 1 9 . 8 5 0 . 9 1 4 2 1 . 7 1 4 4 0 No.1 2 x 4 2 7 . 8 1 2 9 . 0 6 1 .00 2 9 . 0 6 1.11 2 6 . 1 8 22.18 1 2 3 2 x 8 1 7 . 3 8 1 7 . 8 5 1 .00 1 7 . 8 5 0 . 9 6 1 8 . 6 0 8 4 2 x 1 0 1 7 . 0 6 1 7 . 5 1 1 .00 1 7 . 5 1 0 . 9 1 4 1 9 . 1 6 6 3 No.2 2 x 4 2 1 . 5 5 2 2 . 2 9 1 .00 2 2 . 2 9 1.11 2 0 . 0 8 18.29 4 4 0 2 x 8 1 7 , 2 4 1 7 . 7 0 1 .00 1 7 . 7 0 0 . 9 6 1 8 . 4 4 9 8 6 2 x 1 0 1 4 . 4 6 1 4 . 7 8 1 .00 1 4 . 7 8 0 . 9 1 4 1 6 . 1 7 4 4 1 No.3 2 x 4 1 6 . 2 1 6 . 6 1 1 .15 1 9 . 1 0 1.11 1 7 . 2 1 14.80 1 8 0 2 x 8 1 2 . 8 4 1 3 . 0 9 1 .15 1 5 . 0 5 0 . 9 6 1 5 . 6 8 2 0 0 2 x 1 0 9 . 3 1 9 . 4 5 1 .15 1 0 . 8 6 0 . 9 1 4 1 1 . 8 8 2 1 0 Table E.4 Adjustment Bending Stiffness for Canadian Douglas Fir-Larch (MPa) In-grade D = MOE (Data adjusted to 12% MC) Grade Size M O E 1 5 % M O E 1 2 % MOEcONVERSION M O E i s o n SS 2 x 4 1 2 2 0 4 1 2 7 8 3 1 2 7 8 3 13520.16 3 7 0 2 x 8 1 3 6 0 3 1 4 2 4 7 1 4 2 4 7 3 7 3 2 x 1 0 1 2 9 1 4 1 3 5 2 6 1 3 5 2 6 3 7 2 1 + B T R 2 x 4 1 1 6 5 9 1 2 2 1 1 1 2 2 1 1 13141.63 3 7 0 2 x 8 1 3 0 3 1 1 3 6 4 8 1 3 6 4 8 3 8 5 2 x 1 0 1 2 9 1 4 1 3 5 2 6 1 3 5 2 6 3 8 9 No.1 2 x 4 1 0 3 3 5 1 0 8 2 4 1 0 8 2 4 10962.84 9 9 2 x 8 1 0 5 8 2 1 1 0 8 3 1 1 0 8 3 8 3 2 x 1 0 1 0 5 1 4 1 1 0 1 2 1 1 0 1 2 7 6 No.2 2 x 4 1 0 6 8 7 1 1 1 9 3 1 1 1 9 3 11539.46 3 7 0 2 x 8 1 1 3 2 8 1 1 8 6 4 1 1 8 6 4 3 7 0 2 x 1 0 1 1 0 3 8 1 1 5 6 1 1 1 5 6 1 3 7 4 No.3 2 x 4 9 7 4 9 1 0 2 1 1 1 0 2 1 1 10641.66 1 5 0 2 x 8 1 0 0 7 3 1 0 5 5 0 1 0 5 5 0 1 4 9 2 x 1 0 1 0 6 5 9 1 1 1 6 4 1 1 1 6 4 1 5 0 48 Appendix Table E.5 Adjustment Bending Stiffness for Canadian Hem-Fir (MPa) In-grade H = M O E (Data a d j u s t e d to 12% M C ) Grade Size M O E 1 5 % M O E 1 2 » / o MOEcONVERSION M O E i s o n S S 2 x 4 1 1 7 0 0 1 2 2 4 7 1 2 2 4 7 12466.83 3 8 1 2 x 8 1 2 1 3 5 1 2 7 0 3 1 2 7 0 3 3 8 2 2 x 1 0 1 1 8 9 3 1 2 4 4 9 1 2 4 4 9 3 7 9 1+BTR 2 x 4 1 1 4 2 5 1 1 9 6 0 1 1 9 6 0 12246.57 3 9 2 2 x 8 1 1 9 6 9 1 2 5 2 9 1 2 5 2 9 3 9 7 2 x 1 0 1 1 7 0 0 1 2 2 4 7 1 2 2 4 7 3 9 8 No.1 2 x 4 1 0 5 4 9 1 1 0 4 3 1 1 0 4 3 11038.00 1 0 4 2 x 8 1 0 4 5 2 1 0 9 4 1 1 0 9 4 1 6 0 2 x 1 0 1 0 6 3 9 1 1 1 3 7 1 1 1 3 7 5 4 No.2 2 x 4 1 0 7 9 7 1 1 3 0 2 1 1 3 0 2 11540.12 3 8 0 2 x 8 1 1 2 2 5 1 1 7 5 0 1 1 7 5 0 4 0 2 2 x 1 0 1 1 0 3 9 1 1 5 5 6 1 1 5 5 6 3 8 5 No.3 2 x 4 9 9 1 5 1 0 3 7 9 1 0 3 7 9 10397.59 1 7 0 2 x 8 9 9 8 4 1 0 4 5 1 1 0 4 5 1 1 5 8 2 x 1 0 9 9 0 1 1 0 3 6 4 1 0 3 6 4 1 5 9 Table E.6 Adjustment Bending Stiffness for Canadian Spruce-Pine-Fir (MPa) In-grade S P F M O E (Data a d us t ed to 12% M C ) Grade Size M O E 1 5 % M O E 1 2 % MOEcONVERSION M O E i s o n S S 2 x 4 1 0 7 3 0 1 1 2 3 2 1 1 2 3 2 10942.58 4 4 1 2 x 8 1 0 4 2 0 1 0 9 0 8 1 0 9 0 8 4 4 4 2 x 1 0 1 0 2 1 0 1 0 6 8 8 1 0 6 8 8 4 4 0 1+BTR 2 x 4 1 0 4 5 0 1 0 9 3 9 1 0 9 3 9 10710.16 4 5 8 2 x 8 1 0 2 2 0 1 0 6 9 8 1 0 6 9 8 4 5 4 2 x 1 0 1 0 0 2 0 1 0 4 8 9 1 0 4 8 9 4 4 9 No.1 2 x 4 9 7 0 0 1 0 1 5 4 1 0 1 5 4 9977.20 1 2 3 2 x 8 9 4 8 0 9 9 2 4 9 9 2 4 8 4 2 x 1 0 9 2 7 0 9 7 0 4 9 7 0 4 6 3 No.2 2 x 4 9 4 9 0 9 9 3 4 9 9 3 4 10033.28 4 4 0 2 x 8 9 7 5 0 1 0 2 0 6 1 0 2 0 6 9 8 6 2 x 1 0 9 3 1 0 9 7 4 6 9 7 4 6 4 4 1 No.3 2 x 4 9 3 2 0 9 7 5 6 9 7 5 6 9330.29 1 8 0 2 x 8 8 9 6 0 9 3 7 9 9 3 7 9 2 0 0 2 x 1 0 8 5 2 0 8 9 1 9 8 9 1 9 2 1 0 49 

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