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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Automatisk detektering av akustiska resonansfrekvenser i trästockar / Real time spectral analysis for acoustic resonance technique used in timber quality classification

Jonsson, David January 2012 (has links)
In order to measure the quality of the logs, one can with help of Fast Fourier Transform technique get the signals resonance peaks. With help of these peaks you can see whether the quality of a tree is good or bad. This report contains the work of a where a program has been developed to be able to process a vibration created by an automatic hammer hitting on a log of wood. From the processed signal the program should be able to show both the raw wavesignal and the processed measured data from the resonance peaks. Beyond the raw wavesignal and resonance peaks the program should also be able to control the automatic hammer. The goal with the project is to have a program that get the same measure results as an already functioning measuring equipment. The result was a success when with the help of the program you were both able to control the hammer, measure the results and save the data with an accurate results.
132

The Study of Marketing of Timber Industry Association

Tseng, Kuo-Yang 27 July 2010 (has links)
Abstract The importers of wood, sources from around the world through an exclusive of the way to import and export of wood materials to meet the needs of the Asian region, particularly in the domestic market. The wood materials used in public landscaping works are the most valuable and quantitative. Hence, many varieties of imported timbers which require the recommendation by the importer , and therefore the marketing strategy of timber importers often becomes the key decision to use wood materials, such as the United States imported Southern Yellow Pine and the Southeast Asia Pacific iron wood (Merbau), Borneo ironwood (Belian). However, due to the more mature trees being widely accepted by the users but some bad importers sell newly developed cheap replacement, resulting in shorter and the poor quality of life. And this resulted in lower market demand for timber, as a situation of economic theory, "bad money drives out good money". For these above reasons, there is a lack of coordinated organization to consolidate for such a long time in past one-stand-along critical competitive situation resulting in the decline of timber industry. Based on this, to integrate the business platform, the establishment of a national association should be implemented to avoid the price of damage a, build the coordination mechanism, and set up a set of standard testing procedures. Under the gradually declined timber industries, a strong sales promotion strategy should be developed to achieve the success in 1980s. The marketing promotion strategy of timber industry is developed and analyzed with marketing 4P tools. This study gathered the collective opinions of member companies towards the Association's recommendations and expectations. The survey was conducted collectively and analyzed. Finally, the conclusion and recommendations is proposed for guiding future marketing direction. Keywords: Timber Industry Association, marketing strategy, marketing communication
133

Strengthening of timber beams using externally-bonded sprayed fibre reinforced polymers

Talukdar, Sudip 05 1900 (has links)
The use of Fibre Reinforced Polymers (FRP) has grown in popularity in the construction industry. FRP has proven useful in the retrofit of various types of structural elements. It may be used for the strengthening of beams, the seismic upgrade of walls panels, as well as the jacketing of columns to provide confinement. There exist several methods of FRP application for the case of structural retrofits. These include the application of pre-prepared FRP mats, or application of FRP via the wet lay-up process. However, a new technique developed at the University of British Columbia allows for the application of FRP in the form of a spray. Externally bonded Sprayed FRP (SFRP) is known to increase strength and energy absorption capacity of a retrofitted member as well as, or better than, FRP sheets. However, tests have primarily been carried out on concrete members only. An area of interest, into which not much research has been conducted, is the application of SFRP to timber. Timber bridges are extensively used in many parts of the world. Often due to remoteness and practical constraints, it is impossible to apply FRP sheets to retrofit these bridges. SFRP would be a much easier method of FRP application. This study looked at the application of SFRP to Douglas Fir (D.Fir) Beam specimens subjected to 3-Point Flexural Loading only. The specimens were treated with either a water based (Borocol) or oil borne (Creosote) antifungal preservative prior to being sprayed with FRP. Different combinations of adhesives/bonding agents including Hydroxymethylated Resorcinol and Polymeric Isocyanates were used to try to develop a strong bond. When considering using only chemical adhesives to obtain a proper bond between the two constituents of the composite, use of HMR is recommended for timber which is untreated or has been treated with a water borne preservative such as Borocol, while a pMDI adhesive such as AtPrime 2 is recommended for timber treated with an oil borne preservative such as Creosote. For Non Creosoted beams, adhesives did not generate as significant of a strength gain. For Creosoted beams, adhesives may be sufficient to generate significant strength gain when SFRP is applied to a beam. Considering that most structures in use would probably have been treated with a preservative similar to Creosote, in practice, AtPrime 2 or some other some sort of pMDI would probably be the adhesive of choice. Based on the results of the study, it is possible to say that the application of SFRP to retrofit/rehabilitate timber structures shows considerable promise. If a decent bond is achieved between the composite constituents, it is possible to substantially increase the ultimate flexural strength of the member, as well as drastically increase its ductility and energy absorption capacity. It is recommended that further tests be carried out using different types of loading schemes, geometrical configurations of SFRP, other types of anchorage, and development of a proper analytical model before the method is adopted for widespread use.
134

Cross-Laminated Timber– En fallstudie av Hyttkammaren samt en jämförelse med prefabricerat betongelement ur platsomkostnadsperspektiv

Islamovic, Mirnes January 2013 (has links)
No description available.
135

STRUCTURAL BENEFITS OF HEMPCRETE INFILL IN TIMBER STUD WALLS

MUKHERJEE, AGNITA 31 January 2012 (has links)
Due to an increase in environmental consciousness in the construction industry there has been increasing interest in using natural building materials like rammed earth construction, straw bale construction and hempcrete construction. These materials have very small embodied energy and are carbon negative or carbon neutral. Hempcrete is a bio-composite mix made up of hemp shive, lime, cement and water. There has been extensive research undertaken on the thermal, acoustic, and mechanical properties of hempcrete. It has low density, good thermal and acoustic insulation properties, and can passively regulate humidity in a built environment. However it also has low compressive strength and modulus of elasticity. Thus hempcrete cannot be used as a direct load bearing material but can used as an infill material in timber stud walls. This thesis investigates how hempcrete can have beneficial structural effects by preventing buckling of timber (increasing the buckling load) columns when used as an infill in between columns in a timber stud wall. Eight timber walls were constructed (both half scale -1200mm high; and full scale – up to 2133mm high) with varying column dimensions. Six of the walls were infilled with hempcrete of varying density. Two walls were not infilled and were baseline tests. All walls were tested in compression. It was found that high density hempcrete (715 kg/m3) not only prevented weak axis buckling of columns but also carried some direct load. Low density hempcrete was also successful in preventing weak axis buckling of the infilled walls. In-filled walls failed in strong axis buckling at a load twice (for half scale walls with 38x89mm columns) or 4 times(full scale walls with 38x235mm columns) that of the unfilled walls. An analytical model based on buckling of a strut on an elastic foundation was proposed to predict the maximum strength hempcrete can add to a wall by preventing buckling. The timber column strength equations from CSA –O86-01 closely predicted the buckling load of the walls from the experiments. The results from the model were also put in design equations from CSA –O86-01 to predict practical failure loads if the walls failed by buckling into hempcrete. Although only a single test result was available, it was in good agreement with the model predictions. / Thesis (Master, Civil Engineering) -- Queen's University, 2012-01-30 21:18:13.842
136

Acoustic Inspection of Timber

Woods, Simon Nicholas January 2006 (has links)
The ability to determine wood quality using non-destructive tests has enormous potential for the forestry industry in both research and commercial applications. This thesis describes some of the theory of acoustic waves in wood and how wood stiffness can be estimated by measuring the velocity of acoustic waves. Attention is paid to both resonance and stress wave timer technologies and the benefits and problems with both. A detailed description is given of the design of a new tool (Treetap 5.0) to aid in future, acoustic based, timber inspection research.
137

Compression perpendicular to grain in timber – Bearing strength for a sill plate / Tryck vinkelrätt fibrerna hos trä – Sylltryck

Kathem, Ali, Hussain, Tajdar, Kamali, Arman January 2014 (has links)
Timber is widely used in the construction industry, because of its availability and good properties. The compressive strength perpendicular to grain (bearing strength) is one property of wood which is important for structural design. The bearing strength is important for the behavior of the structure in all contact points between wooden members. The calculations models for bearing strength have been a subject of discussion for many years and the different building codes in Europe has treated it differently during the years. The aim of this thesis was to compare different calculations models for bearing strength with the results of an experimental study. In this study the bearing strength for a fully supported beam loaded with a point load was studied. Two different loading lengths were studied as well as loading in a point in the middle of the beam, at the edge of the beam and at a distance of 10 mm between the edge and the loading point. The loading was made with a steel stud. Calculations were also performed according to the following standards; Eurocode 5 (EN1995-1-1:2004) before and after amendment, the German Code (DIN 1052:2004), the Italian Code (CNR-DT 206:2006) and two versions of the Swedish Code (BKR). The results showed that the results from the new version of Eurocode 5 agreed best with the experimental results. The tested results, however, were lower than the values calculated using Eurocode (and all the other codes); this might be explained by the hard loading conditions using a steel stud instead of a wood stud.
138

Strengthening of timber beams using externally-bonded sprayed fibre reinforced polymers

Talukdar, Sudip 05 1900 (has links)
The use of Fibre Reinforced Polymers (FRP) has grown in popularity in the construction industry. FRP has proven useful in the retrofit of various types of structural elements. It may be used for the strengthening of beams, the seismic upgrade of walls panels, as well as the jacketing of columns to provide confinement. There exist several methods of FRP application for the case of structural retrofits. These include the application of pre-prepared FRP mats, or application of FRP via the wet lay-up process. However, a new technique developed at the University of British Columbia allows for the application of FRP in the form of a spray. Externally bonded Sprayed FRP (SFRP) is known to increase strength and energy absorption capacity of a retrofitted member as well as, or better than, FRP sheets. However, tests have primarily been carried out on concrete members only. An area of interest, into which not much research has been conducted, is the application of SFRP to timber. Timber bridges are extensively used in many parts of the world. Often due to remoteness and practical constraints, it is impossible to apply FRP sheets to retrofit these bridges. SFRP would be a much easier method of FRP application. This study looked at the application of SFRP to Douglas Fir (D.Fir) Beam specimens subjected to 3-Point Flexural Loading only. The specimens were treated with either a water based (Borocol) or oil borne (Creosote) antifungal preservative prior to being sprayed with FRP. Different combinations of adhesives/bonding agents including Hydroxymethylated Resorcinol and Polymeric Isocyanates were used to try to develop a strong bond. When considering using only chemical adhesives to obtain a proper bond between the two constituents of the composite, use of HMR is recommended for timber which is untreated or has been treated with a water borne preservative such as Borocol, while a pMDI adhesive such as AtPrime 2 is recommended for timber treated with an oil borne preservative such as Creosote. For Non Creosoted beams, adhesives did not generate as significant of a strength gain. For Creosoted beams, adhesives may be sufficient to generate significant strength gain when SFRP is applied to a beam. Considering that most structures in use would probably have been treated with a preservative similar to Creosote, in practice, AtPrime 2 or some other some sort of pMDI would probably be the adhesive of choice. Based on the results of the study, it is possible to say that the application of SFRP to retrofit/rehabilitate timber structures shows considerable promise. If a decent bond is achieved between the composite constituents, it is possible to substantially increase the ultimate flexural strength of the member, as well as drastically increase its ductility and energy absorption capacity. It is recommended that further tests be carried out using different types of loading schemes, geometrical configurations of SFRP, other types of anchorage, and development of a proper analytical model before the method is adopted for widespread use.
139

Theoretical Aspects Of The Continuously Varying Schedule Process For Timber Drying

January 1984 (has links)
Drying of timber increases its durability and strength. Therefore, timber should be dried to a moisture content close to the equilibrium moisture content it will attain in service. The drying of timber from its natural green state to the required moisture content is thus an important part of the production cycle. Hardwood species, due to their macroscopic structures, are more difficult to dry as compared to softwood. A great deal of research has centred in recent years on developing a fast drying process for softwood; on the other hand, there is a need for a process to dry hardwood rapidly. A new drying technique, called Continuously Varying Schedule (CVS) was recently developed by the author for the purpose of rapidly drying the medium to high density hardwood. The investigation described herein was carried out to compare the CVS process with the conventional drying process. The factors compared were drying time, quality of timber produced and the energy consumed. It was found that the CVS process reduced the drying time by 34.5% and saved 30.7% of the energy. It produced also, a competitive dried timber quality. The process achieved highly efficient drying, as the rate of drying (MC%/h x 100) was 80.3% higher than the conventional process and also, the amount of water evaporated per unit of drying time (g/h) was 67.1% higher. The CVS drying performance has achieved a 71.9% increase in the amount of moisture content reduced per unit of energy (MC%/kWh x 100) and a 57.8% increase in the amount of water evaporated per unit of energy (g/kWh) as compared to the conventional process. Much emphasis was placed on energy saving in the drying plant and it was suggested that a heat exchanger be used to recover waste energy from the exhausted air of the kiln. A dehumidifier coupled to a solar-powered system, backed up with an electric or wood waste booster, was recommended as a low-cost energy drying plant. An alternative source to the petroleum-based energy was also discussed. The study of air flow through the timber stack in the kiln was a major part of this investigation as it is one of the principal features of the CVS process. A new technique was developed to measure the air velocity and the turbulence level %. The technique involves the integration of a hot wire anemometer, data logger, computer and computer peripherals. The air velocity profiles for twelve fan speeds, between 400 and 2200 rpm, were drawn by a computer graphical program, using data collected by the above circuit. It was obvious that the boundary layer which exists around the timber surface at the low air velocity protects the timber being processed against the high and continuously increasing temperature during the CVS drying process.
140

The effects of boron-treated timbers against coptotermes species in Australia

Ahmed, Berhan Mahmoud Unknown Date (has links) (PDF)
In Australia the protection of building timbers from termites relied for many years upon the application of persistent organochlorines as well as the organophosphate compound (chlorpyrifos) and the synthetic pyrethroid (bifenthrin) as soil chemical barriers (Lenz et al. 1990; Watson, 1990; NHMRC, 1992; AS 3660.1 1995). The persistent organochlorines have been banned since 1987 in the USA and from June 1995 in all Australian states except the Northern Territory. The study evaluated the life-cycle of boron as an alternative wood preservative, its toxicity to foraging populations of subterranean termites (‘termites’) over time were particularly referred to the influence of foraging space and determined a suitable loading of boron in timber for hazard class2 (H2) conditions as defined in Australian standard-1997. Preservative treatment of timber according to Australian Standard 1604 (1997) prevents attack and damage of wood and wood products from biodeteriogens (namely fungi and insects). Above-ground interior timber framings are not normally liable to decay but to damage by wood-destroying insects. The study examined the use of borates as wood preservatives to prevent attack and damage by subterranean termites (‘termites’) of the genus of Coptotermes. In addressing the aims of this study, several different avenues of approach were followed. The chapter sequence in this thesis follows the pattern of measuring the effects of borates on a wide range from 20 termites in laboratory bioassay to thousands of termites in natural colonies.

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