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This study describes the population genetic structure of Milicia species sampled from different provenances distributed over 5 countries (Sierra Leone, Cote d'Ivoire, Ghana, Cameroon and Tanzania). Random amplified polymorphic DNA (RAPD) and inter sample sequence repeats (ISSR) variation in 41 accessions from 5 different populations were consistent with each other. Analysis of molecular variance partitioned RAPD and ISSR variation into within- and between-population components. The between-population variation component was large, accounting for 62.2% and 71.5% for RAPD and ISSR respectively. Dendrogram analysis produced 2 major clusters separating dry zone accessions (mainly M. excelsa) from moist/wet zone accessions (mainly M. regia). Sub-clustering further separated accessions by forest type and/or geographic region. Phylogenetic analysis of chloroplast genes involved the use of nucleotide sequencing, restriction fragment length polymorphism (RFLP), and microsatellites. Only one region (5' to trnS) out of 6 regions analysed was polymorphic and revealed 3 different cytotypes. The distribution of the cytotypes matched with the 2 major clusters produced by the dominant markers. Wet/moist and dry zone bands were identified with little evidence of gene flow between populations. Seed mediated gene flow estimated from the chloroplast analysis was small (Nm = 0.23). To relate these molecular information with Phytolyma resistance, field provenance and progeny trials were conducted. Accessions from wet/moist zones were more tolerant to Phytolyma than accessions from dry zone. The data also suggest that accessions bearing the wet/moist zone specific markers have a high probability of being tolerant to Phytolyma. The approaches outlined and the results have general applicability in the sustainability of Milicia spp. and are discussed in relation to germplasm sampling, management and conservation of genetic recourses of Milicia species.

Reducing the amount of metal used within a timber structure has many advantages, particularly when dealing with connections. Fire resistance and durability are commonly cited benefits. In addition the use of alternative connector materials minimises thermal bridging and can also provide a lighter weight structural solution. Existing contemporary forms of non-metallic timber connections are commonly provided through the use of adhesives. However, these connections are reliant on a need for careful offsite, prefabricated construction. Traditional green oak carpentry connections provide a mechanically fastened non-metallic solution. However, carpentry connections are not widely compatible with contemporary architectural design or with the use of modern engineered timber products such as glulam. Building upon research completed at the University of Bath, the aim of this thesis was to develop a mechanical, non-metallic connection system suitable for contemporary applications. Specific objectives were to investigate the structural performance of a defined connection system and to develop analysis methods to facilitate design. A review of the literature demonstrated a lack of uptake and use of mechanical non-metallic connections. Guidance for the design of mechanical fasteners reflects the lack of innovation and research into the use of non-metallic materials. Following an initial experimental investigation of non-metallic materials, an experimental testing programme was completed to investigate the use of glass fibre reinforced plastic (GFRP) dowels in conjunction with densified veneer wood (DVW) plates. The findings of the experimental study demonstrate that the use of these materials can provide a robust connection system for contemporary applications. The results of the experimental work provide guidance on dowel spacing requirements, connection response to load and connection failure modes. The failure modes of the proposed connection system were shown to be unique to the materials used and specific strength analysis methods have been developed to predict connection yield and ultimate strength. A method for predicting initial connection stiffness was also developed through the use of a beam on elastic foundation model.

This thesis addresses various issues in connection with the measurement of moisture content in timber. The early parts include long term experimentally based studies which culminated in producing recommendations to existing British Standards for equilibrium moisture content (EMC) of timber in internal environments. Findings consistently showed lower EMCs than existing recommended values; these are believed to be caused by socio-economic factors. Intermediate sections of the thesis continue with tests on electrical methods of moisture content measurement to establish a basis for comparability and the claimed accuracy of currently available moisture meters in the market. To this end, the performance of a wide range of resistance-type moisture meters in worldwide use was critically investigated under laboratory conditions - it was established that even under the strict controlled conditions of the study, large discrepancies are not uncommon (as great as 13% moisture content difference was observed). While some instruments consistently underestimated, others overestimated under identical conditions. Lack of agreed standards for species corrections and temperature correction factors were found to be the main cause of disagreement between the meters. Further discussions include the layout for a proposed standard in which agreed values for species and temperature correction factors would be established. In the latter part of the thesis moisture gradients in timber, the causes and the current methods of assessment are discussed. In particular, the performance of a leading brand capacitance-type moisture meter was systematically investigated both in the absence and in the presence of predetermined moisture gradients. It was established that moisture gradients severely affect the measured moisture content. A computer controlled capacitance measurement system based on resonance detection was developed to initially replicate the behaviour of conventional capacitance-type moisture meters, and to further investigate possible moisture gradient detection protocols. Two electrode designs were used in order to investigate methods by which moisture gradients could be detected. It was shown that a multi-plate electrode can be used to detect moisture gradients in timber to depths of at least 10 mm.

Thesis (M.S.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1982. / Typescript (photocopy). Includes bibliographical references (leaves 76-79). Also available on the World Wide Web.

Key point to development of environmentally friendly timber structures, appropriate to urban ways of living, is the development of high-rise timber buildings. Comfort properties are nowadays one of the main limitations to tall timber buildings, and an enhanced knowledge on damping phenomena is therefore required, as well as improved prediction models for damping. The aim of this work has consequently been to estimate various damping quantities in timber structures. In particular, models have been derived for predicting material damping in timber members, beams or panels, or in more complex timber structures, such as floors. Material damping is defined as damping due to intrinsic material properties, and used to be referred to as internal friction. In addition, structural damping, defined as damping due to connections and friction in-between members, has been estimated for timber floors. The thesis consists of six main parts. The first part is entitled “Contexts”, and is composed of four chapters. A general overview of the wood material and its structural use in buildings is presented in Chapter 1. Chapter 2 gives a thorough literature review on comfort properties of (timber) floors. Chapter 1 and Chapter 2 serve as justifications for the motivation of this work, expressed in Chapter 3, and the aim of the work, expressed in Chapter 4. The next part “Backgrounds” briefly describes the basic theories used along the thesis, for the analytical studies (Chapter 5), the experimental studies (Chapter 6), and the numerical studies (Chapter 7). The part “State of the art” is a general literature review on damping (Chapter 8). A particular accent is set on the derivation of various damping prediction models. The “Research” part summarizes the original research work. Chapter 9 briefly presents the background and main findings for each study, and Chapter 10 concludes and proposes suggestions for further research. The studies are detailed in four journal papers, which are integrally reported in the “Publications” part. Paper I focuses on the evaluation of material damping in timber beam specimens with dimensions typical of common timber floor structures. Using the impact test method, 11 solid wood beams and 11 glulam beams made out of Norway Spruce (Picea Abies) were subjected to flexural vibrations. The tests involved different spans and orientations. A total of 420 material damping evaluations were performed, and the results are presented as mean values for each configuration along with important statistical indicators to quantify their reliability. The consistency of the experimental method was validated with respect to repeatability and reproducibility. General trends found an increasing damping ratio for higher modes, shorter spans, and edgewise orientations. It is concluded from the results that material damping is governed by shear deformation, which can be expressed more conveniently with respect to the specific mode shape and its derivatives. Paper II deals with the prediction of material damping in Timoshenko beams. Complex elastic moduli and complex stiffness are defined to derive an analytical model that predicts the hysteretic system damping for the whole member. The prediction model comprises two parts, the first related to bending, and the second related to shear. Selected experimental damping evaluations from Paper I are used to validate the model and obtain fitted values of loss factors for two types of wood. The good agreement of the derived model with experimental data reveals an efficient approach in the prediction of material damping. In Paper III, a semi-analytical prediction model of material damping in timber panels is described. The approach is derived from the strain energy method and input is based on loss factors, which are intrinsic properties of the considered materials, together with material properties and mode shape integrals, whose calculation can easily be implemented in most finite element codes. Experimental damping evaluations of three types of timber panels are performed. These are particleboards, oriented strand board panels and structural laminated veneer panels. Fair goodness-of-fit between the experimental results and the prediction models reveals an efficient approach for the prediction of material damping in timber panels with any boundary conditions, knowing only the loss factors and the mode shapes. In Paper IV, dynamic properties of two timber floors are experimentally evaluated by impact method. Each floor uses one specified type of connectors, either screws or nails. A numerical model is developed using constrained degrees-of-freedom for the modeling of connectors. Numerical analyses have been performed, and show good agreement with experimental results. A procedure is written using the commercial finite element software Abaqus to predict material damping from a strain energy approach. Estimation of structural damping is performed as the difference between the experimentally evaluated total damping and the predicted material damping. The contribution from floor members to material damping is extensively investigated, and the needs for better prediction of damping are discussed. Specific details of some aspects of the work are included in the “Appendix” part.

The objective of this thesis is to explore the possibility of a non-destructive method of improving the dependability and economy of timber railroad bridges that have been exposed to environmental and service conditions. With railway companies increasing the load of trains in return for larger profit, maintenance and replacement of timber bridges has risen throughout recent years. Once chosen for its low cost and ease of construction, timber bridges are being replaced by more efficient concrete and steel trestles. The load path of a passing train through the elements of a bridge pier can be affected for several reasons. One focus of this report is how the load is distributed among the piles or supporting elements. Through recent research at Texas A&M University (2003), a relationship between the ultimate test load, Pmax, and the strength parameter, Lambda, was derived from 33 destructively tested specimens. Piles used in the testing were accumulated from three different locations in the United States and subjected to uniaxial compression along the length of the pile in a steel test frame. Instrumentation along the length of the piles provided data for plots of load versus deflection. Analysis of the plots showed that the tendency of the strength parameter, Lambda, to predict the ultimate test load was consistent but a computer generated model representing a typical service train revealed significantly lower loads on the piles than those used in the destructive tests. Further analysis of the test specimens at lower load levels led to a service level strength parameter that was derived with levels comparable to typical train loads. Guidelines for the service strength parameter, Beta, were based upon hypothetical loads from the computer generated model and previous test data. Field testing involved consent from a railroad company to install load cells and string potentiometers on an in-situ timber bridge. While simultaneously taking load and deflection measurements for bridges under the dynamic load of a passing train, the axial stiffness of the piles was determined and used in the calculation of the service level strength parameter,Beta. Future research includes removing the piles that were tested in the field and assessing them in the original method of axial compression in the steel test frame. This method can be used universally in the field to examine load path of passing trains and assess the amount of remaining axial strength of in-situ piles without interrupting daily flow and traffic of the railroad bridge. Ultimately, this research could lead to the railroad industry saving money and time due to the quick and convenient installation process.

Thesis (doctoral)--Universität für Bodenkultur Wien, 2008. / Includes bibliographical references (p. 261-273).

XLam New Zealand Limited is the first company in New Zealand to manufacture Cross Laminated Timber (CLT); structural timber panels used for roof, floor and wall diaphragms in commercial and residential buildings. Commissioning of the factory began in April 2012, but it is not yet fully complete. The panels are currently being produced discretely rather than in a production line, and some plant is yet to be installed. It is important that procedures and control documents are implemented from the beginning in a new factory. This Project provides these, as well as recommendations to improve the long term production of CLT in New Zealand by developing: 1. A Quality Assurance (QA) Framework for the CLT manufacturing process. 2. A CLT Design Guide to aid engineers and architects in structural design using CLT. 3. A Health and Safety Framework to control hazards and develop a culture of health and safety within the factory. 4. A 10 year financial forecast model to analyse possible future expansion options for XLam. This Project has been prepared in partial fulfilment of the 2012 Master of Engineering Management (MEM) degree at the University of Canterbury – ENMG 606: Project.