The use of Cross-Laminated Timber products has increased in recent years with a range of structural applications including CLT tall buildings and folded structures. As CLT is used in more innovative structural applications the need for specific methods of design and analysis are apparent. A review of the literature demonstrates that despite the increasing popularity of CLT in construction there are limited methods for the design and analysis of CLT panels and structures that fully utilise its unique properties. Manufacturer data relating to the CLT material properties varies how the cross directional laminas are considered. Finally it was found that there is limited published knowledge regarding CLT material properties for panels loaded non-tangentially to the direction of the timber grain. A method for predicting failure loads and modes has been presented and compared with experimental test data. A Strut and Tie model is proposed for the analysis of CLT panels, a methodology originally developed to design of reinforced concrete deep beams. The Strut and Tie approach considers panel geometry, loads, supports, different properties in tension and compression and was adapted to consider anisotropic behaviour. The procedure, advantages and limitations have been presented and a model developed for an application in CLT. The use of this model is considered for the analysis of simple CLT panel loadings. The behaviour of CLT at different timber grain angles demonstrate a complex composite behaviour influencing the strut and tie capacities. The definition of node sizes was also found to be critical to the definitions of the struts and ties and hence the capacity of the sections. Comparison of experimental tests to the model demonstrates some application to using a Strut and Tie in CLT panels. It identifies where additional investigation is required to improve, develop and validate the model into a method that may be used for full-scale CLT panels and structures in design practice and consider a variety of geometries and loading arrangements.

This thesis tests the use of Welsh-grown timber in the building envelope, through the prototyping of a series of live design projects with a focus on species, technology and tectonic form. Projects are clustered under 4 headings identified as significant to the Welsh timber industry: hardwoods, engineered timber, timber board products and the complete timber envelope. The Welsh timber industry relies heavily on the importation of sawnwood, timber board products and innovative, engineered timber systems to meet an increasing demand to improve construction efficiency and the environmental performance of the building envelope. Compared to Northern and Central Europe and regions such as the Vorarlberg, Austria, Wales is perceived as having an underdeveloped and underperforming timber construction industry with only 15% forest cover to supply a variety of timber sectors. This thesis analyses the properties of Welsh-grown soft and hardwoods, the technical and skill limitations and opportunities of the industry and highlights the impact of the use of timber on the tectonic form of the building envelope. These evaluations inform the observations and reflections of 12 architectural prototype projects to demonstrate potential to exploit the Welsh-grown timber crop in the design and construction of the architectural building envelope. The research demonstrates that it is possible to use Welsh-grown timber for a variety of modular superstructure, cladding and external joinery systems. The conclusions identify limitations, such as a lack of research and development investment, from government and business, and a lack of knowledge and focused direction across the industry. However, the prototype projects show that the unique properties of timber, sustainably grown, managed and processed in Wales can be innovatively manufactured and assembled into prefabricated, components for the design and construction of the low-energy architectural building envelope. Furthermore, the properties, technology and skills available have informed an additive tectonic approach that is specific to Welsh-grown timber.

This thesis tests an approach to delivering affordable housing for rural Wales, through the design and development of a system of homegrown, re-engineered timber components for self build. Recent studies and policy have demonstrated an acute shortage of affordable housing in rural Wales. Consequently, the Welsh Assembly Government has committed to deliver an additional 6,500 homes in the period 2007 - 11. However, there remains significant concern regarding the long term, sustainable delivery of affordable rural housing. This dissertation proposes a solution to this need, based on the readily available resource of homegrown softwood. Sitka Spruce has become the primary production crop of the Welsh woodlands. It is rarely used in the construction industry due to its propensity to distort and instead is utilised in low value industries, including low grade carcassing timber. It is proposed that through an innovative and radical approach, homegrown timber resources can offer a high quality, locally sourced and sustainable modern method of construction. In this study, a system of engineered homegrown timber components is designed, prototyped and tested as a self build construction solution for affordable housing in the diverse physical, social and economic context of rural Wales. Design led studies, including a ‘Pattern Book’ of house types, and realised prototypical constructions are used to inform and interrogate the proposed components and construction methodology. The primary objective of these investigations is to examine the applicability and appropriateness for self build construction. Finally, through the construction of a whole house prototype, a system of homegrown timber components and an approach to its assembly is proposed. Although limitations remain with this proposal, it has been possible to demonstrate that there is significant opportunity for an innovative, self build construction system using homegrown timber resources, to offer an efficient and sustainable solution for affordable housing in rural Wales.

The use of glued laminated timber (glulam) in building and construction provides a designer with an attractive, environmentally friendly alternative to steel and concrete. However, along with other engineering materials, glulam is subject to creep and in order to use it efficiently without the risk of unacceptable long-term deflections occurring, a reliable method of estimating creep in glulam is desirable. With this mind, the Structural Timber Research Unit (STRU) at the University of Brighton embarked, in 1988, on an extensive glulam research programme. Since then, the deflection of prepared glulam specimens has been measured in the laboratory under controlled conditions and in 1992, the programme was broadened to include measurements to determine the behaviour of glulam in full-scale structures. A number of test sites have been established in a variety of buildings and the method chosen to monitor glulam beams in these is theodolite intersection using a Leica Electronic Coordinate Determination System (ECDS3). Borrowed from industrial and engineering surveying, the use of the theodolite intersection technique to monitor glulam is unique and it has, despite the practical difficulties and size of structure involved, enabled the movement of beams to be monitored with an accuracy of 0.1 mm. By processing three-dimensional intersection coordinates, vertical deflections and creep have been determined and results show that the creep response of the glulam beams monitored in full-scale structures can be represented by a seasonally modulated exponential function. This correlates well to results from the laboratory tests and demonstrates that measurements taken in the laboratory can predict the behaviour of glulam in-situ. The creep factors obtained also agree well with the values given for these in Eurocode 5: Design of Timber Structures.

This thesis is about late medieval carpenters, their techniques and their art, and about the structure that became the fusion of their technical virtuosity and artistic creativity: the hammer-beam roof. The structural nature and origin of the hammer-beam roof is discussed, and it is argued that, although invented in the late thirteenth century, during the fourteenth century the hammer-beam roof became a developmental dead-end. In the early fifteenth century the hammer-beam roof suddenly blossomed into hundreds of structures of great technical proficiency and aesthetic acumen. The thesis assesses the role of the hammer-beam roof of Westminster Hall as the catalyst to such renewed enthusiasm. This structure is analysed and discussed in detail. Its place in the milieu of late medieval architecture is assessed, and its influence evaluated. That influence took effect mainly in East Anglia. Thus, early fifteenth-century trends in hammer-beam carpentry in the region are isolated and analysed. A typology of is created, from which arise surprising conclusions regarding the differing priorities late-medieval carpenters ascribed to structure, form and ornament. A chapter is also devoted to a critical review of literature pertaining to the topic.

L'assemblage des éléments de structures en bois de dimensions standard comme des poutres massives ou composites s'effectue très fréquemment avec des ancrages métalliques cloués. Ces éléments en tôle pliée formés à froid peuvent être mis sur le marché Européens lorsqu'un ATE est obtenu à partir des recommandations de l'ETAG 015. Le développement ainsi que la caractérisation de la résistance de ces ancrages s'effectue jusqu'à présent dans la société CULLEN Building Products par des essais longs et coûteux. En alternative à cette démarche, ce travail présente une démarche permettant de modéliser le comportement de ces assemblages par la méthode des éléments finis. En premier lieu une étude est conduite sur les types d'aciers utilisés et sur l'influence de la phase de formage sur la résistance de l'ancrage. Il est alors montré qu'il n'est pas nécessaire d'intégrer l'état d'écrouissage produit par le pliage et que la modélisation peut débuter à partir de la géométrie finale à l'aide d'éléments coques. En second lieu une modélisation simplifiée du comportement des pointes est proposée. Les paramètres nécessaires à sa mise en oeuvre sont identifiés. Le modèle est mis en oeuvre pour simuler le comportement d'un assemblage tôle sur bois à une seule pointe. Les résultats sont confrontés à des résultats expérimentaux. La modélisation de l'ancrage étant forcément tridimensionnelle, une modélisation non linéaire du bois 3D est proposée en idéalisant le bois comme une structure. Cette structure est composée de cube de mousse (crushable foam) associé à des poutres élasto plastique qui donne à cet édifice son caractère fortement orthotrope. Ce modèle structurale du bois est mis en oeuvre pour modéliser le cisaillement de barreaux de bois, de la compression transversale sur appuis de poutre, des essais d'enfoncement de broches et un assemblage traditionnel par embrèvement. Ces modélisations permettent de montrer les capacités du modèle à décrire les comportements et de définir ses limites. Dans une dernière partie, l'ancrage, les pointes et le bois sont rassemblés pour constitué trois modèles d'ancrages caractéristiques les plus complexes de la production CULLEN. Les résultats obtenus sont confrontés à des résultats expérimentaux conduits en laboratoire. Enfin les modélisations sont utilisés pour expliquer le comportement interne des ancrages au cours du chargement jusqu'à l'atteinte de la rupture / The assembly of various elements of timber structures of standard dimensions such as timber beams or composite beams is often achieved by nailed steel connectors. These folded steel elements obtained by cold forming can be launched on the European market once an ETA is delivered regarding the recommendations of the ETAG 015. Up to now, the development and the characterisation of the strength of these connectors have been done within the company: CULLEN Building Products by lengthy and costly experimental tests. As an alternative to this procedure, this work presents an approach which enables modelling the behaviour of these connections by the finite element method. In the first place the influence of the type of steel used and the forming process on the strength of these hangers was studied. It is shown that it is not necessary to take into account the hardening produced by the forming of the steel so that the modelling can be achieved from the final geometry by shell elements. Secondly a simplified model of the behaviour of the nails is proposed. The parameters necessary for its implementation are identified. The model is then used to simulate the behaviour of the connection of a steel plate to timber by a single nail. These results are then confronted with the experimental results. As the model is necessarily 3 dimensional, a 3D non linear model is proposed for the timber by considering it as a structure. This structure is composed of cubes of crushable foam which are associated with elasto-plastic beams to give this structure its highly orthotropic behaviour. This structural model of wood is implemented to model the shear of timber bars, transversal compression where beams are supported, embedment tests of steel dowels and a traditional bird's mouth assembly. These various models show the capacities of this structural model to describe timber's complex behaviours; they also define the limits of this modelling. In the last section, the hanger, the nails and the timber are assembled in order to constitute the models for three characteristic and complex hangers of CULLEN's production. The results obtained are confronted with the experimental results. Finally, the models are used to explain the internal behaviour of these hangers at various loads up to their failure

The doctoral research revolves around a comparative study of timber modern methods of construction for low-rise, residential buildings in Scotland. The building techniques studied involve both timber-frame panel construction (open-panel and closed-panel systems and structural insulated panels) and massive-timber construction (cross-laminated and nail-laminated timber panels). A non-timber technique is also included in the study: more traditional, load-bearing masonry (blockwork). These different building techniques have been analysed from two complementary aspects: environmental impacts and thermal performance. The environmental study is based on the life-cycle assessment methodology and embraces various aspects: environmental impacts (e.g., climate change, acidification, eutrophication, ozone depletion, etc.), consumption of energy (renewable and non-renewable resources) and production of waste (from non-hazardous to radioactive). The assessment takes a cradle-to-gate approach and, in its structure and method, is informed by the current recommendations of the international standards in the field (i.e., ISO 14040 series). Various environmental trade-offs between construction methods have been identified. In terms of global-warming potential (excluding biogenic carbon sequestration), results suggest that timber-frame buildings show a better performance than masonry buildings; this is particularly true for the open-panel system, which emits about 10% less carbon than the masonry counterpart. Massive-timber buildings tend to cause more carbon emissions than masonry ones. In terms of consumption of non-renewable primary energy, timber buildings do not generally show significant advantages with respect to blockwork-based masonry. In particular, structural-insulated panel systems tend to show very high energy requirements. Timber-based buildings show a tendency to cause increased acidification, eutrophication and creation of low ozone than their masonry counterpart. The level of offsite fabrication that is employed for the erection of the buildings plays an important role in the magnitude of most environmental impacts, which show an average decrease between 5% and 10% when some of the operations are shifted from the construction site to the factory. v The thermal study investigates the performance of the building envelope, and, in particular, of external walls, by means of tests whereby the thermal behaviour of a sample of walls (of full-size section) has been observed and measured over time. On the outside, the walls were exposed to real, natural weather variations throughout the summer. The study especially focuses on the time-dependent response of three different walling systems (which results from their individual cross-sectional arrangements of building components and the associated combination of heat-storage capacity and thermal resistance): a timber-framed wall, a cross-laminated-timber wall and a masonry wall. Thus, the main goal of the study was to characterise the thermal-inertia parameters of these walls. This type of thermal behaviour is related to the repercussions of global climate change at UK level, especially in terms of increase in solar irradiance and temperature, which requires an adaptation of the building-envelope such that it can perform well both during wintertime and summertime, by providing maximum indoor comfort with minimum economic and environmental costs from the construction and operation of buildings. The timber-framed wall possesses the greatest capacity to slow down the propagation of temperature waves from the outer surface to the inner surface (time lag), whereas the masonry wall performs best with respect to reducing the amplitude of temperature oscillation on the inner surface (decrement factor). The cross-laminated-timber wall exhibits intermediate values of both time lag and decrement factor, relative to the other two walls. Both the thermal and life-cycle assessment of the construction alternatives aim at assisting the design and decision-making process in the residential field and at suggesting areas that need to be addressed and improved, towards a coherent evolution of the building techniques included in this study and a step forward in the realisation of sustainable, low-rise dwellings.

Im Rahmen holztechnologischer Prozesse wie dem Holzschutz, der Holzmodifizierung oder der Zellstoffherstellung sind die Eindringwege von Flüssigkeiten in das Holz von großem Interesse. Neben den Eigenschaften des Tränkmittels und der Gestaltung des Tränkprozesses stellt der Aufbau des Holzes einen der wesentlichen Einflussfaktoren hinsichtlich der Permeabilität des Holzes für Flüssigkeiten dar. Der Artikel gibt einen Überblick über den Einfluss mikrostruktureller Eigenschaften des Holzes auf dessen Tränkbarkeit.

Im Rahmen holztechnologischer Prozesse wie dem Holzschutz, der Holzmodifizierung oder der Zellstoffherstellung sind die Eindringwege von Flüssigkeiten in das Holz von großem Interesse. Neben den Eigenschaften des Tränkmittels und der Gestaltung des Tränkprozesses stellt der Aufbau des Holzes einen der wesentlichen Einflussfaktoren hinsichtlich der Permeabilität des Holzes für Flüssigkeiten dar. Der Artikel gibt einen Überblick über den Einfluss mikrostruktureller Eigenschaften des Holzes auf dessen Tränkbarkeit.

Die Anatomie des Holzes stellt eine entscheidende Einflussgröße bei einer Vielzahl holztechnologischer Prozesse dar. Der folgende Beitrag behandelt den Bau der verholzten Zellwand am Beispiel der Tracheiden des Nadelholzes.