Technology & Engineering
Timber Degradation
Timber degradation refers to the process of deterioration and damage that occurs in wood over time. This can be caused by various factors such as moisture, insects, fungi, and weathering. Degradation can weaken the structural integrity of timber, leading to potential safety hazards and reduced lifespan. Preventative measures such as proper storage, treatment, and maintenance can help mitigate timber degradation.
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4 Key excerpts on "Timber Degradation"
eBook - PDFTimber
Structure, Properties, Conversion and Use
- H.E. Desch, J.M. Dinwoodie(Authors)
- 2016(Publication Date)
- Red Globe Press(Publisher)
Part 5 TIMBER IN SERVICE -WHAT HAPPENS TO WOOD IN SERVICE? -HOW CAN ITS LIFE BE EXTENDED? 231 18 Degradation of Timber in Service 18.1 Introduction With the passage of time and the influence of the environment, all materials exhibit a loss in per-formance, a process which the materials scientist refers to under the all-embracing title of degrada-tion. Undesirable changes occur to the material which, at best, are restricted to its surface layers, but which usually permeate the whole of the material and have a most pronounced effect on its mechanical performance, especially in terms of strength and toughness. The rate of the degrada-tion is usually specific to a particular material and to specific environmental conditions. Some timbers display good resistance to many degrading processes, while others have little resistance. There are six groups of degrad-ing agencies -biological, chemical, photoche-mical, thermal, fire and mechanical -and these will be discussed in this and successive chapters. 18.2 Biological degradation Wood is an organic material and therefore it is not too surprising to find that it is subject to attack by a whole host of biological agencies. Because of the significance of biological degrada-tion to the performance of timber in service, and because of the variable and sometimes complex nature of the degradation, it has been decided to describe this form of attack in the following two chapters. Thus, readers are referred to • Chapter 19, for a comprehensive account of the attack of wood by wood destroying fungi, • Chapter 20, for a detailed description of the attack of wood by insects, • Chapter 21, for means to eradicate both fungal and insect attack, and • Chapter 22, for methods to prevent attack by fungi and insects.
- G Fu(Author)
- 2005(Publication Date)
- Woodhead Publishing(Publisher)
100 5 Detecting decay in wood components R.J. ROSS, USDA Forest Products Laboratory, USA and X. WANG and B.K. BRASHAW Natural Resources Research Institute, USA 5.1 Introduction Wood deterioration is one of the most common damage mechanisms in timber bridges and other wood structures and often inflicts damage internally. This may occur without visible signs appearing on the surface until a member’s load-bearing capacity has been largely destroyed. Determining an appropriate load rating for an existing timber structure and establishing rational rehabilitation, repair, or replacement decisions can be achieved only when an accurate assessment of its existing condition is made. Knowledge of the condition of the structure can lead to savings in repair and replacement costs by minimizing labor and materials and extending its life. In wood structures, the degradation of a load-bearing (in-service) member may be caused by any one of several organisms that derive their nourish-ment or shelter from the wood substrate in which they live. For example, several types of fungi attack wood. The hyphae of these fungi secrete enzymes that depolymerize the chemical components of wood, thereby lowering the density, strength, and hardness of a member. This results in a significant reduction in load-carrying capacity, which in turn may result in the member’s failure. Accurate detection of decay in wood structures is therefore critical to ensuring the safety of the public and extending the service life of the structures. Recently, we prepared a comprehensive manual on the inspection of wood structural elements titled Wood and Timber Condition Assessment Manual (Ross et al. 2004). It was prepared at the request of the American Forest and Paper Association to assist field engineers and other inspection professionals.
eBook - PDFDurability of Engineering Structures
Design, Repair and Maintenance
- J Bijen(Author)
- 2003(Publication Date)
- Woodhead Publishing(Publisher)
4.7 References 1 Ridout B, Timber Decay in Buildings , the Conservation Approach to Treatment , London, E & F N Spon, 1999. 2 Hendriks Ch F, Bijen J, et al., Durable and Sustainable Building Materials (in Dutch: Duurzame Bouwmaterialen ), Best, Aeneas, 1999. 3 Wood Vade-mecum ( Houtvademecum ), The Hague, Ten Hagen & Stam Pub-lishers, 2001. 4 Grosser D, Biological Deterioration of Wooden Building Materials (in German: Planzliche und tierische Bau-und Werkholzschädlinge ), Leinfelden-echterdin-gen, DRW-Verlag, 1985. 5 Schmidt O, Wood Fungi ; Biology , Damage , Preservation , Applications (in German: Holz-und Baumpilze , biologie , Schäden , Schutz , Nutzen , Berlin, Springer-Verlag, 1994. 6 Bridges , EGH , Bericht Entwicklungsgemeinschaft Holzbau , Brücken (in German), Düsseldorf, Arbeitsgemeinschaft Holz, 1988. 7 Fengel D, Wegener G, Wood; Chemistry , Ultrastructure , Reactions , Berlin and New York, Walter de Gruyter, 1989. 156 Durability of engineering structures 4.12 Example of repair of a deteriorated wooden beam section using new wood reinforced with glass fibre reinforced polyester rods. 11 8 Homan W J, Chemical Modification of Wood , Wageningen, SHR Timber Research, 1997. 9 Paul O, The Beta-method ; Applicability and Development (in German: Das Beta-Verfahren Bewährung und Neuentwicklung ), Bautenschutz & Bausanierung, 1996, 12 17–22. Wood 157
- C Sjostrom(Author)
- 2018(Publication Date)
- Routledge(Publisher)
The characteristic features of each decay type as well as possibilities to prevent degradation are presented. Durability of wood, treated or untreated, is studied in field tests and tests conducted in the laboratory. Advantages and disadvantages with different test methods are discussed in the paper. Keywords: Biological attack, decay, degradation, durability, wood 1 Introduction Wood is a surprisingly durable natural product. The durability against microbial degradation is mainly due to the high content of lignin, a substance very resistant to degradation, which embeds the cellulose fibrils and the hemicellulose. In addition, certain timbers have a heartwood rich in extractives that confer an increased durability. Only specialized microorganisms 'decay organisms' and certain insects are able to degrade wood in a terrestrial environment. Dry wood is not attacked by microorganisms and studies of archaeological wood show that in many cases only minor changes in the wood structure have occurred over a period of ca. 4500 years in situations where the wood has been dry and protected from insect attack. This demonstrates wood under such conditions can have an unlimited durability in practical terms. Durability of Building Materials and Components 7 (Volume One). Edited by C. Sjostrom . Published in 1996 by E & FN Spon, 2-6 Boundary Row, London SE1 8HN, UK. ISBN 0 419 20690 6. 754 Nilsson and Edlund Wood can be invaded by decay fungi, staining fungi, moulds and bacteria. Based on the mode of attack, decay fungi can be divided into three different categories: brown rot, white rot and soft rot. In addition, non-degrative moulds and staining fungi and bacterial species can be found inhabiting wood. 2.1 Brown rot fungi In building constructions decay is mainly caused by brown rot fungi, e.g.
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