Moisture Meters for Structural Wood Damage Assessment
How experts assess the structural integrity of wood framing or wood timbers in-situ

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[1] Paul Probett, Clinton Craig, Blake Probett, "An Introduction to Micro-Drilling Technology for N. Z. Structural Timber Assessment", Incodo Ltd, 4/511 Cameron Rd, Tauranga NZ, article adapted by InspectAPedia with permission, August 2012. Contact the authors by Email: Paul Probett, mail2us@incodo.co.nz , Tel: 027 28 000 36 (Mobile) Website: https://www.incodo.co.nz/ [Copy of this article on file as Microdrilling_Assessment_Incodo.pdf]
Quoting from the Incodo website the company describes its services:

• Incodo Forensic Building Pathology:
  
  The Forensic Building Pathology division provides evidence in report form to government agencies, consultancy firms, lawyers and others, when truly independent analysis based on comprehensive testing is required. Incodo arguably has the largest, most up-to-date and comprehensive range of building investigation equipment available and has developed unique methodologies particularly in the field of non-destructive testing for leaking structures.


• Incodo In situ Timber Assessment:
  
  The in-situ Timber Assessment division provides a service whereby technicians use state-of-the-art timber resistance drill technology to profile variations in timber density associated with timber decay.
  
  The work is done on site and the results are instant.
  
  
  This technology is objective and evidential in nature and provides assessment as to whether wood is significantly decayed, suspect or suitable for retention. The technology has particular application in locating and assessing hidden decay.

[2] Thomas Tannert, Andreas Muller, Mareike Vogel, "Applications and limitations of NDT: a timber bridge case study", NDTCE’09, Non-Destructive Testing in Civil Engineering Nantes, France, June 30th – July 3rd, 2009, web search 8/3/2012, original source: http://www.ndt.net/article/ndtce2009/papers/144.pdf [copy on file as Tannert_Timber_Test_144.pdf]
Abstract
The applications and limitations of different non-destructive and semi-destructive techniques to evaluate the structural integrity of timber members in a pedestrian bridge are presented as a case study. Sophisticated assessment tools are required to detect hidden damages in timber structures: for example stress-wave techniques are used to evaluate the modulus of elasticity of bending members and resistance to drilling is used to gain knowledge of areas of changed density due to insect or moisture induced damages. Reliably relating the gathered data to the structural integrity of the structure is a complex issue. Bending members and connection details of a decommissioned timber bridge were evaluated using non destructive assessment tools. Eventually these parts were tested destructively to assess their remaining modulus of elasticity and load bearing capacity. The need for improvements in the current practice is highlighted by comparing the results from the non-destructive, semidestructive and destructive tests.

[3] Bohumil Kasal, Thomas Tannert, "RILEM Technical Committee on In Situ Assessment of Structural Timber", Bohumil Kasal et al., 2010, Advanced Materials Research, 133-134, 271, Abstract: Timber is an intriguing structural material and the only one that is truly renewable. Being biodegradable, hygroscopic and non-isotropic, it presents special challenges when assessing its integrity in structures. The presented paper outlines the major issues related to in-situ evaluation of structural timber and summarizes the work of the RILEM Technical Committee 215-AST “In-situ assessment of structural timber”. The committee was established in 2005 to bring together leading scientists and practitioners in the field of evaluation of timber in existing structures. Timber structures have been investigated for decades using numerous techniques that have been either developed specifically for the material or were transferred from other fields of investigation. A state-of-the-art report describing existing and emerging technologies and methods was prepared by the RILEM committee. The report describes the principles, the applications and the limitations of major evaluation techniques for in-situ assessment of timber. A brief discussion of codes standards and future research needs shows that much needs to be done in this area. As a present activity, harmonized test procedure recommendations are being prepared that will provide the engineering community with valuable guidance when evaluating timber structures.

[4] Bohumil Kasal & Thomas Tannert (Editors), In Situ Assessment of Structural Timber, ISBN 978-94-007-0559-3, Rilem 2010

[5] Bohumil Kasal, Tension Micro Specimens, In Situ Assessment of Structural Timber RILEM State of the Art Reports, 2011, Volume 7, 75-80, DOI: 10.1007/978-94-007-0560-9_8, [excepts chapter 7 on file: Tension Micro-Specimens, as Kasal_Testing.pdf]
Abstract The principle of this method is extracting triangular specimens (about 5 mm equal-sides triangle) along the length of the member. Small-kerf circular saw with a fixture attached to the surface of the member is used to extract the specimens. Specimens are then glued to the test blocks and tested in tension. The method gives direct values of tensile modulus of elasticity and strength for clear wood. The values are local and pertain to the tested area and surface.
[From chapter 7.1 Background: This method was developed by Kasal and is based on direct measurement of tension properties along fibers. Bending strength evaluation is an important aspect of in situ evaluation of timber members as it is one of the predominant modes of loading, but estimates of the bending properties in situ can present a challenge. With information on the member's tensile properties, bending strength estimates can be made; tensile strength has been related to bending strength and is considered to be approximately equal. Tensile properties have a poor correlation with compression properties therefore tensile strength can not be estimated using information attained with the core drilling technique. Specimens can however be extracted to evaluate the tensile properties of in situ members with the technique described in the following sections....']

[Also] Kasal B, Anthony R: Advances in in-situ evaluation of timber structures. Progress in Structural Eng and Materials. 6(2):94-103, 2004.

[6] Thomas Tannert, Andreas Müller, Mareike Vogel, "in-situ assessment, hot spots, moisture content, block-laminated timber", ICTB 2010, Bern University of Applied Sciences. ISBN 978 8251 926805, in-situ assessment, hot spots, moisture content, block laminated timber,
Abstract:
Timber has been a structural material for bridges for centuries and numerous examples throughout the world demonstrate its durability. But timber is biodegradable and hygroscopic and regular inspections are recommended to determine the condition of the structure. This paper reports on the structural health monitoring of timber bridges in general and the long term moisture measurement inside block-laminated timber elements of several traffic bridges in specific. Presently there is no reported scientific information available on the long-term moisture behaviour and the resulting moisture induced stresses and dimensional changes of block-laminated timber elements. The paper reports on the monitoring of the moisture content of a block-laminated timber bridge.
[References 7-13 below are cited from this document]

[7] Wilkinson K, Thambiratnam D, Ferreira L. Non Destructive Testing of Timber Bridge Girders. In Proceedings Int. Conf. on Structural Condition Assessment, Monitoring and Improvement, Perth, Australia, 2005.

[8] Kasal B, Anthony R: Advances in in-situ evaluation of timber structures. Progress in Structural Eng and Materials. 6(2):94-103, 2004.

[9] Gerold M. Bloc-Glued Laminated decks for timber bridges. Structural engineering international, 12(3): 214–217, 2002.

[10] Graham T. Overview of non-destructive evaluation technologies. In Proceedings of the Nondestructive Evaluation of Aging Bridges and Highways, Ed by S. Chose, 1995.

[11] Duwadi SR, Ritter MA. An Overview of the Wood in Transportation Program in the United States, In Proceedings 5th World Conference on Timber Engineering, Montreux, Switzerland, 1998.

[12] Rinn F, Schweingruber FH, Schär E. Resistograph and X-Ray Density Charts of Wood. Comparative Evaluation of Drill resistance Profiles and X-Ray Density Charts of Different Wood Species. Holzforschung 50:303-311, 1996.

[13] Brashaw B, Vatalaro RJ, Wacker JP and RJ Ross. Condition Assessment of Timber Bridges: 1. Evaluation of a Micro-Drilling Tool. Gen. Tech. Rep. FPL-GTR-159. Forest Products Laboratory Madison, WI. 2005.

[14 Simpson W. Drying and Control of Moisture Content and Dimensional Changes. Chapter 12, Wood handbook - wood as an engineering material. General Technical Report FPL–GTR– 113. Forest Products Laboratory, WI, 1999.

[15] "Fractometer Print Manual", IML Instrumenta Mechanik Labor System GmbH Großer Stadtacker 2 69168 Wiesloch • Germany, 02-2008, web search 8/4/12, original source: http://www.imlusa.com/Fractometer_Print_eng_web_A4.pdf [Copy on file as Fractometer_Print_eng.pdf]

[16] Bob Monk, "Evaluation of Decay Detection Equipment in Standing Trees", USDA Forest Service, web search 8/4/12, original source http://www.fs.fed.us/eng/techdev/IM/tree_decay/tree_decay_detect_equip.shtml [Copy on file as Monk_Tree_Deday_Detection.pdf] Introduction - quoting:
A project was proposed to test and compare several of the devices that are able, to some degree, to detect decay in trees. Decay in trees is directly related to the hazards that they present. However, detection of decay does not necessarily mean that a tree is hazardous. The identified devices can be used to determine what decay is present. It is still necessary to use professional experience and sound judgment to decide if a tree actually poses a hazard. General guides or "rules of thumb" can also be used, such as Guidance notes from the Minnesota Department of Natural Resources and the USDA Forest Service, 1996 that suggests a 25 mm ring of sound wood is required for every 150 mm of stem diameter at any point on the stem. If the proportion of decayed wood to sound wood exceeds this level then action may need to be taken to minimize the hazard posed by the tree (Lawday and Hodges, 2000). [Additional selected citations from this article are below]

• [16a] Larsson, B.; Bengtsson, B.; and Gustafsson, M. 2004. Nondestructive Detection of Decay in Living Trees. Tree Physiology. 24: 853-858
• [16b] Moore, W. 1999. The Combined Use of the Resistograph and the Shigometer for the Accurate Mapping and Diagnosis of the Internal Condition of woody Support Organs of Trees. Arboriculture Journal. 23: 273-287
• [16c] Nicolotti, G.; Socco, L.V.; Martinis, R.; Godio, A.; and Sambuelli, L. 2003. Application and Comparison of Three Tomographic Techniques for Detection of Decay in Trees. Journal of Arboriculture. 29(2): 66-77
• [16d] Seavey, R.; and Larson, T. 2002. Inspection of Timber Bridges. Minnesota Department of Transportation Technical Report MN/RC-2002-34. St. Paul, MN. 43 p.
• [16e] Wang, X.; Divos, F.; Pilon, C.; Brashaw, B.K.; Ross, R.J.; and Pellerin, R.F. 2004. Assessment of Decay in Standing Timber Using Stress Wave Timing Nondestructive Evaluation Tools: A Guide for Use and Interpretation. Gen. Tech. Rep. FPL-GTR-147. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 11 p.

[17] Pilodyn Wood Tester, USA / Canadian Source: Intech-NDE, 6211 Roper Road Edmonton, Alberta T6B 3G6, Tel: 1 888-576-7756 or Intech-NDE, 140 - 8851 Beckwith Road Richmond, B.C., Tel: 1 800-677-8884, or USA Tel: 800-297-3208, Website: http://www.intechnde.com, web search 8/4/12, original source: http://www.corvib.com/pilodyn/ Quoting:
Pilodyn is an easy-to-use wood testing instrument which is suitable for trees, railway ties and utility poles. The Pilodyn wood tester (Hylec Controls) is described by and currently available in North America from InTech/NDE U.S. Tel: 905-716-5604 / 800-297-3208, or Email: bnadeau@intechnde.com

[18] Pilodyn Wood Tester, Hylec Controls, available in Australia from Ferret http://www.ferret.com.au/n/Pilodyn-wood-density-meter-from-Hylec-n852069 - Quoting:
Pilodyn, available from Hylec Controls , was developed to determine the density and strength of dead and living wood. Invisible soft rot can be detected rapidly and objectively in an easy non-destructiveway and the reduction in strength associated with it can be determined. This can be of vital importance in the case of wooden playground structures,climbing frames and telephone masts.
With PILODYN 6J Forestversion the density of the wood is determined on living trees. The damage is so little that the tree suffers no harm and the testing method is regarded as non-destructive.
Testing procedure: The testing procedure is very simple: The tester is loaded with the ramrod and then pressed firmly onto the tet surface. The impact pin is shot into the wood by pressing the trigger cover. The depth of penetrationcan be read straightaway in mm on the scale mounted on the tester.
Typical applications of the Pilodon:
Testing the stability of wooden structures on playgrounds, detection of soft rot
Testing the strength on wooden telephone masts, detection of soft rot
When thinning out: sorting out trees with undesirable density of the wood
Early detection of diseases: periodic measurement detects unnatural changes in the wood density
Comparison of the location-dependent density to determine the optimal location for the respective tree species
Establishing productivity with respect to density for the same tree species and similar location properties for culture purposes Testing and sorting of cut wood into timber classes

[19] Hylec Controls, 8 Melissa Street AUBURN NSW 2144 AUSTRALIA, Tel: 1300 522 004, Email: sales@hyleccontrols.com.au, http://www.ferret.com.au/c/Hylec-Controls

[20] Brashaw, Brian K.; Vatalaro, Robert J.; Wacker, James P.; Ross, Robert J. 2005. "Condition Assessment of Timber Bridges: 1. Evaluation of a Micro-Drilling Resistance Tool" Gen. Tech. Rep. FPL-GTR-159. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 8 p., web search 8/5/2012, original source: http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr159.pdf [copy on file as Micro_Drill_Study_USDA_fpl_gtr159.pdf] This publication is also available from the U.S. FPL at www.fpl.fs.fed.us
Abstract:
The research presented in this report was conducted to evaluate the accuracy and reliability of a commercially available micro-drilling resistance device, the IML RESI F300-S (Instrument Mechanic Labor, Inc., Kennesaw, Georgia), in locating deteriorated areas in timber bridge members. The device records drilling resistance as a function of drilling depth, which allows the operator to assess the location of deterioration in the member cross section. Bridge components containing different levels of natural decay were used as test specimens in this study. The IML RESI F300-S was first used to assess decay in the timber bridge specimens. The specimens were then sawn along their length into slabs to expose their interior condition. The interior faces of these slabs were inspected visually and with a stress-wave probe to confirm if deterioration was present. On the basis of these tests, we conclude that this micro-drilling device accurately determines if deterioration is present at the point at which the test is performed. Keywords: timber, bridges, inspection, drilling resistance, nondestructive evaluation
Excerpt from the study's conclusions:
Based on our tests, we offer the following comments about the accuracy of using the IML RESI F300-S for locating deterioration in bridge timbers:
1. The tool is accurate at determining the presence of decay in timber bridge specimens. However, these data are limited to the drilling location.
2. The tool can precisely locate an internal defect (decay pocket, check, or split) within the member’s cross section. This can be advantageous for condition assessment and load rating purposes.
3. Decay indices were developed for Douglas-fir timbers as follows: sound, >25% resistance; moderate decay, 10–25%; and advanced or severe decay, 0–10%.
One drawback is that multiple, time-consuming drilling would be required to map the area and extent of the decay in the other plane. Another possible drawback is the potential to spread the decay to sound areas within a timber or to sound timbers by multiple use of a contaminated drill bit. Routine cleaning of drill bits, or replacement with a new one, would greatly reduce this potential drawback.
It is crucial to use this or any nondestructive testing tool or device as part of a comprehensive condition assessment. Such an assessment should incorporate an in-depth visual inspection, knowledge of prior use of the structure, and a working knowledge of fundamental engineering properties of structural wood products. This technique, when used in concert with visual and ultrasound techniques, would provide a very accurate description of the condition of timbers.

[21] Brashaw, B.K.; Vatalaro, R.J.; Erickson, J.R.; Forsman, J.W.; Ross, R.J. 2004. Final Report: A Study of Technologies to Locate Decayed Timber Bridge Members. Project No. 187-6456, NRRI/TR-2004-06. Duluth, MN: UM-Duluth, Natural Resources Research Institute.

[22] Brashaw, B.K.; Vatalaro, R.J.; Ross, R.J.; Wacker, J.P. 2005. Condition Assessment of Timber Bridges: 2. Evaluation of Several Commercially Available Stress Wave/Ultrasonic Tools. Gen. Tech. Rep. FPL-GTR-160. Madison, WI: USDA Forest Service, Forest Products Laboratory.

[23] Ross, R.J.; Brashaw, B.K.; Wang, X.; White, R.H.; Pellerin, R.F. 2004. Wood and Timber Condition Assessment Manual Madison, WI: Forest Products Society. 74 p.

[24] Troltech GMBH & Co. KG. Deutchland, Grebbener Str. 7, D-52525 Heinsberg, Deutchland, produces the Trotec T2000, Tel: 02452 962-450, International: +49 2452 962-450, Email: online@trotec.de, Website: http://www.trotec.de/, Web page for the Troltec T2000:  http://www.trotec.de/en/product-catalog/measuring-instruments/multi-function/t2000/

[25] Paul Probett, Incodo, Ltd., "Thermal Imaging and Building Surveying / Inspection" 2008, Incodo Ltd, 4/511 Cameron Rd, Tauranga NZ, article adapted by InspectAPedia with permission, August 2012. Contact the authors by Email: Paul Probett, mail2us@incodo.co.nz , Tel: 027 28 000 36 (Mobile) Website: https://www.incodo.co.nz/ [Copy of this article on file as Thermal Imaging NDT Presentation 2008.ppt ]

Allen, Edward and Joseph Iano. Fundamentals of Building Construction: Fourth Edition. Hoboken: John Wiley & Sons, 2004. pg. 91 [LVL lumber]

APA - The Engineered Wood Association [Website: www.pacificwoodlaminates.com ], 7011 So. 19th St., PO Box 11700, Tacoma WA 98411-0700, Tel: 253-565-7265. APA provides an HDO/MDO Plywood Product Guide that offers details about these products., provides an HDO/MDO Plywood Product Guide that offers details about these products. Product support help desk: 253-620-7400. Email the APA at help@apawood.org. Web search 09/13/2010, original source: http://www.pacificwoodlaminates.com/img/PDFs/PlywoodGuide.pdf

Building Failures, Diagnosis & Avoidance, 2d Ed., W.H. Ransom, E.& F. Spon, New York, 1987 ISBN 0-419-14270-3

Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728

R-Value of Wood, U.S. Department of Energy

Microllam Laminated Veneer Lumber (LVL) and/or Parallam Parallel Strand Lumber (PSL) MSDS Material Safety Data Sheet, courtesy of Weyerhaeuser Company, PO Box 9777, Federal Way, WA 98063-9777 Tel: 253-924-3865

Log Homes: Log Home Design, U.S. Department of Energy

• In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
  
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