Rozprawy doktorskie na temat „Timber”

From the inception of high rise construction concrete and steel have been the foundation both literally and figuratively of the construction process. As we, a society, become more aware and conscious of the environmental impacts of our built environment we must ask ourselves, are our current construction practices the best or are there ways that we can not only become more environmentally cognizant, but also more efficient in our construction of buildings. This project is an investigation of how a joint can help to improve the construction process and manifest itself into creating the tectonic nature of a project by using timber in high rise construction.
MARCH

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 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.

Dissertação para obtenção do Grau de Mestre em Engenharia Civil – Estruturas e Geotecnia
This dissertation covers the study of historic timber roof structures in Transylvania area - Romania, the structures type, its elements and connection variety between them. Procedures to study a structure of this category are approached. It is also referred semi and non-destructive tests that can be done to better understand the present wood characteristics, and potential reparation or strengthening solutions for the structure in case it is necessary. Ultimately a case study is analyzed and some intervention solutions are proposed for a gothic structure type in the nave of Huedin Reformed church.

How can we as design professionals contribute to increase the use of less carbon-intensive materials to build our growing cities? Cities are experiencing a resurgence in population growth and therefore the building industry ought to attend this demand with sustainable solutions. One way of responding to the growing urban population and increase demand for housing as well as to make efficient use of our limited resources is to increase the density in our cities. Since steel and concrete have high material strengths, we currently use either steel, concrete or composites of them to build skyscrapers. Unfortunately, both of these materials have a large carbon footprint. The design community has the challenge to achieve net-zero emissions buildings by the year 2030, and the efforts now should be focused on using less carbon intensive materials, such as timber. While cultures around the world have built with wood for centuries, recent technological innovations, such as Cross Laminated Timber (CLT), is allowing for new applications of wood as the main structural material and the potential to use it for large-scale projects. However, as expected with a new building material some constrains have still to be overcome. For my thesis, I desired to explore this issue through the design of a tall building using mass timber as its main structural material. Engineered timber is here, the future is bright!
Master of Architecture

This thesis project is an investigation of both heavy timber construction and a means to create a retreat away from the chaos of modern life. This culminated in a porch outside of downtown Austin, Texas. The program began with an entrance foyer, kitchen, wine cellar, a humidor, a library, a bar, a locker room, restrooms, and storage. The form became a long, gradually curving hallway responding to the shape of the island. Rooms expand off of the hallway at both the beginning and the end. A heavy timber truss was designed so that it could be adapted to accommodate expansion for rooms, site constraints, and programmatic needs. Special attention was paid to the details of the retreat such as the connections needed to assemble the heavy timber truss and the handrails. The project conveys a strong connection with the site it is situated on.
Master of Architecture

Thesis (MBA)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Northern Timbers Sawmill (NTS), a hardwood sawmill in Tzaneen and part of Merensky Timber (Pty) Ltd, wished to determine their customers’ expectations and perceptions of the products and services offered. In order to assist NTS with this it was decided to develop a customer satisfaction survey that would be a tool for NTS to use to accurately and consistently measure and monitor the satisfaction of their customers with their products and services over time. A thorough literature study was done followed by primary research that included semi-structured interviews and a quantitative survey. Semi-structured interviews were performed on a randomly selected sample of customers from two primary segments, namely wet-off-saw and kiln dried timber. Based on the feedback from the interviews it was decided that the standard SERVQUAL model was the most appropriate framework to use as part of the development of the survey. An additional product quality and related aspects section was also included. The Cronbach alpha results of the SERVQUAL survey was 0.75 and 0.87, for expectations and perceptions, respectively, indicating a high internal correlation and consistency and indicating that the survey provided reliable results. The internal consistency was also confirmed by high Cronbach alpha results for each individual dimension. The primary components of satisfaction that were measured were expectations and perceptions (or performance). The customer satisfaction index for NTS was 89.87 per cent, which was fairly similar to the product satisfaction of 91 per cent attained from the product quality related section. The most important priorities for improvement identified were “Employees in Northern Timbers tell you exactly when services will be performed”, “Employees in Northern Timbers give prompt service to you” and “When Northern Timbers promises to do something by a certain time, they do so.” The effort NTS has made in ensuring that they stack, wrap and paint the select grade timber bundles contributed to the visibility and one of the highest mean scores in the survey of 5.63 out of 6. The fact that customers can contact the production team at the sawmill directly holds advantages for the customers and this was also confirmed by the survey producing the joint highest mean score of 5.63. It is also clear that there is very little interest and value for NTS in selling the FSC timber at a premium or offering pre-planed timber at a premium. The survey will be done twice a year – once during May or June, and once during October or November.

The thesis addresses two main problems: 1) Probablistic modelling of lengthwise variability in structural timber, 2) Reliability and damage tolerance analysis of beams made of structural timber. Timber is considered as an elastic-brittle material. Dependence of timber properties on time and environment conditions is neglected. The presented statistical analysis of MOE is based on experimental data. An original method for determination of the MOE function on the basis of a measured deflection curve has been developed. The Log-normal, Gumbel or Normal distributions can be recommended as the probability distribution model of the homogeneous random field of MOE with the scale of fluctuation equal to 1.5-2.5 m. The variability of bending strength of timber beams has been studied with help of a weak-zone model. Assuming a marked Poisson random field as a probabilistic model of bending strength, analytical solutions have been derived for a number of particular problems. The influence of the correlation between strengths of weak zones has been studied with help of the Monte Carlo simulation. Time invariant reliability indices and damage tolerance indices have been computed for the weak-zone model and the corresponding homogeneous modelof a timber beam. The difference in reliability indices between the homogeneous and weak-zone models depends more on the probability model of the weak-zone strength than on the mean distance between the weak zones. There is no significant difference in the damage tolerance indices computed for the two considered models of a timber beam.
Godkänd; 1998; 20061122 (haneit)

This research aims to examine the applicability of conventional inspection methods for timber structures where structures have recognised heritage value. The research seeks to understand the appropriateness of inspection methodologies typically prescribed for timber in heritage applications. A literature review of current inspection methods utilised by engineers, architects and others within the heritage structures field has been undertaken, and the appropriateness of timber structural inspection methods used in practice (destructive testing, semi-destructive testing, and non-destructive testing methods) reviewed in light of heritage aims for Australian structures, and interviews conducted with practicing industry professionals to discuss uptake of these methods in practice. A review of current literature indicates that non-destructive technologies present significant potential for further analysis of timbers in-situ without damage to the fabric itself, and represent a particular opportunity for heritage sites, as analysis can be conducted with minimal invasiveness. Interviews with practicing professionals within this industry indicates that currently, such methods have been incorporated only minimally into standard professional practice methodologies. While a lack of familiarity with many available methods is evident, the reasons behind the limited uptake are complex, including but not limited to a lack of pre-defined Australian guidelines prescribing their use, a perception of high associated costs, and an unwillingness on the part of clients to request the use of these methods. It is found that significant opportunity exists for an improvement in the uptake of non-destructive methods as preferential over semi-destructive test methods. Indicative processes of example best-practice methods incorporating non-destructive testing into a typical assessment regime are presented.

Timber-concrete composite (HBV) floors are widely manufactured by many construction companies. Cross laminated timber (CLT) elements are an effective way to produce more homogenised timber building elements. In this thesis, the applicability of measurement-based prediction methods to calculate the apparent sound reduction index (R’) for these two types of elements was investigated. A prediction model using Statistical Energy Analysis (SEA) was developed and validated to calculate the airborne sound transmission of a HBV floor. There was additional complexity in modelling this floor system compared with other SEA models found in the literature therefore two types of model were compared. To determine the stiffness of the floor it was proposed that bending stiffness predicted using the theories of Huffington and Troitsky provide a more suitable and flexible approach than that of Kimura and Inoue. All SEA models predicted a weighted sound reduction index to within 2.0dB of the measurements. For CLT plates, an accurate measure of the elastic moduli was sought to determine direct sound transmission. A low-frequency stiffness can be determined by modal measurement and optimisation of the material constants (≤ 100Hz a thin plate model is adequate). At mid to high frequencies (>300Hz) sound transmission of CLT was predicted using a frequency-dependant modulus determined from directly measuring the bending wavespeed. Elastic moduli were extracted from wavespeed data (the Young’s modulus was measured to be approximately 50% less stiff than the low-frequency stiffness) and in the y-direction the value of the shear modulus Gyz determined that a thick plate model should be applied in this direction. Finite Element Method (FEM) models of CLT plates and junctions using the elastic moduli determined using the methods described above were validated using measurements of freely and simply supported plates and three simple junctions (L-junction, rotated L-junction and T-junction). The contribution of residual modes (higher than the frequency range of interest) to the calculated point mobility was assessed. The transition to thick plate theory occurs within the frequency range of interest (100-5000Hz). This resulted in a modal density which increases with frequency and some implications of this are discussed. The best agreement between FEM model and measured data was obtained for the simplest (unrotated) L-junction. Finally, measurement based prediction methods to assess the flanking performance of CLT combined with the HBV floor were investigated. Agreement was obtained between the structure-borne and airborne methodologies if a correction factor, which accounts both for the thick plate properties of the CLT and the fit of measured results to the HBV model, was used. The Df path was the strongest transmission path and the most accurately predicted and hence it was possible to predict the apparent sound reduction index (R’) by summing the paths.

Timber Tower: 10 20 30 offers a conceptual structural system for tall wooden buildings. The thesis has been a noumenal design process into the subject of timber towers, where the conceptual system is designed to work in accordance with engineering concepts for tall buildings. The system uses mass timber as the primary structural material supported by embedded steel plates. The introduced system plays to the strength and weaknesses of both corresponding materials. Mass timber is used as the primary material that is designed to take care of the dead & live loads, while steel is used as a secondary material to give additional support to the vertical loads. The structural system is interpolated to three different height categories; 10, 20 & 30. The timber & steel system is designed to be prefabricated in parts and assembled on site. Other considerations also addressed in the thesis has been fire-, weather- and soundproofing of the structure.

Alvsbacka Bridge was erected in the summer of 2011. During the planningof the construction researchers from LTU and SP Tr¨a designed ahealth monitoring system that constantly measures different parameterson the bridge. The motivation for health monitoring systems is several:Bridge safety, verification of the design and complement during inspections.Health monitoring of infrastructure is common, many bridges areequipped with health monitoring systems. Timber bridges are rarely monitored.This research project is looking to answer what type of sensorsis suitable for bridges in order to make them smart. The smartness ofthe bridge in this case is to help optimize bridge maintenance, assurethe service life and build knowledge about measurements on large timberconstructions. This thesis presents the monitoring system of the bridge,moisture content monitoring and studies the weather effects on the bridge.The monitoring system of ¨Alvsbacka Bridge consists of several differentsensor systems that continuously measure temperature, moisture content,movements, cable forces, wind velocity, wind direction. The monitoringsystem had some problems with sensors not communicating. Long termmoisture content monitoring show anticipated results and the bridge deckmovements are close to the theoretical values.
Godkänd; 2015; 20150126 (nicbjo)

Engineered timber products are becoming increasingly popular in the construction industry due to their attractive aesthetic and sustainability credentials. Cross-laminated timber (CLT) is one such engineered timber product, formed of multiple layers of timber planks glued together with adjacent layers perpendicular to each other. Unlike traditional building materials such as steel and concrete, the timber structural elements can ignite and burn when exposed to fire, and thus this risk must be explicitly addressed during design. Current design guidance focusses on the structural response of engineered timber, with the flammability risk typically addressed by encapsulation of any structural timber elements with the intention of preventing their involvement in a fire. Exposed structural timber elements may act as an additional fuel load, and this risk must be adequately quantified to satisfy the intent of the building regulations in that the structure does not continue burning. This can be achieved through timber’s natural capacity to auto-extinguish when the external heat source is removed or sufficiently reduced. To address these issues, a fundamental understanding of auto-extinction and the conditions necessary to achieve it in real fire scenarios is needed. Bench-scale flammability studies were undertaken in the Fire Propagation Apparatus to explore the conditions under which auto-extinction will occur. Critical conditions were determined experimentally as a mass loss rate of 3.48 ± 0.31 g/m2s, or an incident heat flux of ~30 kW/m2. Mass loss rate was identified as the better criterion, as critical heat flux was shown by comparison with literature data to be heavily dependent on apparatus. Subsequently, full-scale compartment fire experiments with exposed timber surfaces were performed to determine if auto-extinction could be achieved in real fire scenarios. It was demonstrated that auto-extinction could be achieved in a compartment fire scenario, but only if significant delamination of the engineered timber product could be prevented. A full-scale compartment fire experiment with an exposed back wall and ceiling achieved auto-extinction after around 21 minutes, at which point no significant delamination of the first lamella had been observed. Experiments with an exposed back and side wall, and experiments with an exposed back wall, side wall, and ceiling underwent sustained burning due to repeated delamination, and an increased quantity of exposed timber respectively. Firepoint theory was used to predict the mass loss rate as a function of external heat flux and heat losses, and was successfully applied to the bench-scale experiments. This approach was then extended to the full-scale compartment fire experiment which achieved auto-extinction. A simplified approach based on experimentally obtained internal temperature fields was able to predict auto-extinction if delamination had not occurred – predicting an extinction time of 20-21 minutes. This demonstrates that the critical mass loss rate of 3.48 ± 0.31 g/m2s determined from bench-scale experiments was valid for application to full-scale compartment fire experiments. This was further explored through a series of reduced-scale compartment fire experiments, demonstrating that auto-extinction can only reliably be achieved if burnout of the compartment fuel load is achieved before significant delamination of the outer lamella takes place. The quantification of the auto-extinction phenomena and their applicability to full-scale compartment fires explored herein thus allows greater understanding of the effects of exposed timber surfaces on compartment fire dynamics.

Increasing awareness of sustainable building materials has led to interest in enhancing the structural performance of engineered wood products. Wood is a sustainable, renewable material, and the increasing use of wood in construction contributes to its sustainability. Multi-layer wooden panels are one type of engineered wood product used in construction. There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. Assembly techniques considered in the earliest stages of this research work were laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. Cross-laminated timber (CLT) was found to offer some advantages over these other techniques. It is cost-effective, not patented, offers freedom of choice regarding the visibility of surfaces, provides the possibility of using different timber quality in the same panel at different points of its thickness, and is the most well-established assembly technique currently used in the industrial market. Building upon that foundational work, the operational capabilities of CLT were further evaluated by creating panels with different layer orientations. The mechanical properties of CLT panels constructed with layers angled in an alternative configuration produced on a modified industrial CLT production line were evaluated. Timber lamellae were adhesively bonded in a single-step press procedure to form CLT panels. Transverse layers were laid at a 45° angle instead of the conventional 90° angle with respect to the longitudinal layers’ 0° angle. Tests were carried out on 40 five-layered CLT panels, each with either a ±45° or a 90° configuration. Half of these panels were evaluated under bending: out-of-plane loading was applied in the principal orientation of the panels via four-point bending. The other twenty were evaluated under compression: an in-plane uniaxial compressive loading was applied in the principal orientation of the panels. Quasi-static loading conditions were used for both in- and out-of-plane testing to determine the extent to which the load-bearing capacity of such panels could be enhanced under the current load case. Modified CLT showed higher stiffness, strength, and fifth-percentile characteristics, values that indicate the load-bearing capacity of these panels as a construction material. Failure modes under in- and out-of-plane loading for each panel type were also assessed. Data from out-of-plane loading were further analysed. A non-contact full-field measurement and analysis technique based on digital image correlation (DIC) was utilised for analysis at global and local scales. DIC evaluation of 100 CLT layers showed that a considerable part of the stiffness of conventional CLT is reduced by the shear resistance of its transverse layers. The presence of heterogeneous features, such as knots, has the desirable effect of reducing the propagation of shear fraction along the layers. These results call into question the current grading criteria in the CLT standard. It is suggested that the lower timber grading limit be adjusted for increased value-yield. The overall experimental results suggest the use of CLT panels with a ±45°-layered configuration for construction. They also motivate the use of alternatively angled layered panels for more construction design freedom, especially in areas that demand shear resistance. In addition, the design possibility that such 45°-configured CLT can carry a given load while using less material than conventional CLT suggests the potential to use such panels in a wider range of structural applications. The results of test production revealed that 45°-configured CLT can be industrially produced without using more material than is required for construction of conventional 90°-configured panels. Based on these results, CLT should be further explored as a suitable product for use in more wooden-panel construction.

External cooperation: Martinson Group AB and Research Institutes of Sweden (RISE)

A problem has been observed by many researchers regarding the cracks caused mainly by moisture variation in timber structures. However, this effect has been neglected over the past decades. In addition, many design codes do not have a room for a realistic formulation of the moisture diffusion and its effect in causing internal stress, deformation, and cracks. Moreover, if this effect occurs in connection areas, usually the weakest structural section, it has and also had shown a devastating effect on the service life of many wooden structures. In the current work, a Fickian moisture diffusion model is implemented by use of finite element simulation with the help of the commercial software ABAQUS for a dowelled beam column connection. The results of such moisture diffusion were used to analyse the stress situation inside the timber section. Moreover, an extended finite element method was applied in ABAQUS to investigate how moisture induced crack develops into the timber section. Furthermore, a parametric study was performed by using Python scripting to investigate the effect of dowel spacing (horizontal and vertical) and critical energy release rate on the development of the moisture-induced crack. The results obtained revealed that for the same material property when the dowel spacing increases (either horizontal or vertical) the crack length increases significantly. Likewise, the crack length increases when the critical energy release rate requirement of the timber is decreasing.

This work presents a study of shipbuilding and timber management in the Royal Dockyards in the period 1750 – 1850, focusing on an archaeological investigation of ship timber marks. The first chapter outlines the concept of timber marking in shipbuilding contexts, stressing the multi-disciplinary approach to the study highlighted in the available archaeological and documentary evidence by which the practice of timber marking can be understood. Chapter two outlines the background to timber marking in the Georgian era and the development of the practice within the broader advances made in shipbuilding, technology and design prior to the end of the 17th century. Chapter three outlines the developments in shipbuilding and the introduction of systems to control and standardise the management of timber in the Royal Dockyards in the 18th century. In the latter half of the 18th century we will see the attempts of naval reformers to develop these systems of timber management and pave the way for the sweeping changes made at the beginning of the 19th century. Chapter four highlights these changes with the introduction of the Timber Masters and looks at the nature of timber management and the marking of timbers as identified in documentary sources. This evidence lays the foundation for the understanding of timber marking in the 19th century as witnessed in the archaeological record. The remaining chapters present the much more extensive archaeological evidence for timber marking among several high profile assemblages. The main assemblages presented in Chapters 5 to 9 show the diversity of timber marking practices and how they relate to the working processes of the Royal Dockyards. The research offers new insights into the understanding of shipbuilding and the management of timber in the Royal Dockyards between 1750 and 1850 and explores the possibilities for further avenues of study.

A fundamental requirement for efficient use of a glulam beam is an accurate knowledge of its mechanical behaviour and the material properties characterising that behaviour. It becomes extremely important to obtain accurate measurements of material properties ofglulam, but this can be challengeable, especially for commonly used properties, such as the modulus of elasticity and shear modulus. Experiment testing is the way to determine elastic properties, however, the problem of experimentally determining appropriatevalues of these properties for timber-based composite is not as simple and straightforward as in isotropic materials, and care must be taken in the experimental methods used in determining their values. There is a need to develop an appropriate method in order to evaluate these properties. Unlike the traditional methods in whichcontact devices such as inclinometers or linear variable differential transducers are used to identify the material properties of glulam by utilizing their measurements of displacements and rotations at specific points, the optical methods provide an efficient and accurate approach for measuring these properties at multi-location so that more regions of interest can be monitored simultaneously without contact. Moreover, the traditional devices are limited to give measurements in one or two dimensions whereas the optical methods can be used to gain measurements in three dimensions. Although the optical techniques were successfully applied to different structural applications, little work has been done on the area of evaluating material properties of timber, especially modulus of elasticity and shear modulus. Therefore, the primary motivation of this project will be allocated to evaluate those properties utilizing the stereo vision approach. This thesis describes the research work in which a stereo camera system combined with a photogrammetric approach was proposed to evaluate material properties of timber and timber-based composite joists. A series of experiments were conducted to investigate the applicability of the approach to evaluate different material properties of glulam beams under different types of tests, including the torsion and the compression. Remarkable findings were obtained which might help for developing an outline for a future research programme in the field of evaluating material properties of glulam, allowing investigating the relationship between these properties. The results also showed that the optical system not only allowed assessing performance and reliabilityof the traditional sensors, but also allowed monitoring the deformation of the samples at various locations by providing more information which would not be possible to obtain using the traditional techniques.

Fire retardant treated timber has been used in interior and exterior building structures to satisfy the legal flammability requirements. Dricon and NCX are two commercial phosphorus-based products sold by Arch Timber Protection. However, modifications to their formulation may be required due to their boron and formaldehyde contents, respectively. This research aimed to acquire an understanding of the effect of a number of phosphorus-based fire retardants on the decomposition, flammability and burning behaviour of timber, in order to aid their development. Materials have been investigated on a micro-, bench- and intermediate-scale, and evaluated for physical properties. Thermal decomposition has been studied using thermogravimetric analysis in both air and nitrogen, and simultaneous thermal analysis coupled with Fourier transform infrared spectroscopy. Flammability and burning behaviour has been studied using microscale combustion calorimetry and cone calorimetry. Residue analysis has been carried out using scanning electron microscopy coupled with electron dispersive x-ray analysis. Existing fire retardant timber treatments were applied to timber specimens. All three treatments operated in the condensed phase by reducing the onset temperature of timber pyrolysis, and promoting the formation of a stable char and water. Scanning electron microscopy revealed a barrier formation on the surface of Dricon treated char. All treatments increased the CO:CO2 ratio during burning in the cone calorimeter. This is attributed to reduced volatile gas production, enabling simultaneous glowing oxidation of the char surface. Depth of penetration studies showed that high concentrations of phosphorus on the surface of timber is sufficient to significantly reduce the fire growth rate index, but deeper penetration and increased overall phosphorus concentration is more effective at reducing the total heat released by the substrate. New phosphorus-based formulations were applied to timber and their effect on its flammability was assessed. All treatments reduced the total heat released, but not all were effective enough to be used commercially. Ammonium hypophosphite increased the residue yield of timber and was shown to operate via both condensed and gas phase fire retardancy mechanisms. A low melting glass formed a gel-like barrier on the surface of the char, but its melting point was too high to optimise the reduction in peak heat release rate. Both ammonium polyphosphate and guanidine/ammonium phosphate formulations promoted carbonisation of the timber structure. A coherent barrier layer was formed by the organoclay; however, the improvement was not effective enough to warrant further investigation. Combinations of nanometric oxides and phosphoric acid were effective. The oxides catalysed the phosphoric acid mechanism to promote the pyrolysis of timber and re-radiating mechanisms were proposed for the char. Further work is suggested to improve the effect. Layer by layer assembly does not provide a sufficient loading to effectively reduce the flammability of timber. Lastly, attempts were made to address the problems of scale-up between micro scale thermal decomposition, bench-scale burning and intermediate-scale regulatory fire tests. Three models for the prediction of Euroclass results have been compared and applied to the materials investigated within this thesis. A method is proposed for the prediction of the Euroclass of fire retarded timber products. Correlation coefficients between micro-, bench- and intermediate-scale flammability tests have been calculated and the results are discussed.

Increasingly complex architectural geometries present new challenges for structural engineers. Collaborative, digital workflows which integrate 3D parametric architectural models with Finite Element Modelling software grant structural engineers a higher degree of geometric versatility and influence during the preliminary design phase. Through integrated parametric design models – also labelled “co-rationalized” – structural engineers may not only easily respond to rapid model variations and unusual assemblies, but also inform the building design from inception. This thesis presents an example of a project executed in a co-rationalized manner through architectural and structural collaboration, using both digitally-integrated and analog models, for the design and construction of solid timber shells structures using Cross-Laminated Timber (CLT) panels. By exploring a co-rationalized design process, timber engineering details are identified and integrated into the architectural model, and the role of structural engineer takes an active rather than reactionary role in the preliminary design stages. The result of this process using integrated parametric models was the design, fabrication, and assembly of a folded plate wall prototype and three CLT panels with double curvature. This research demonstrates how collaboration and integrated modeling enables the realization of the architectural versatility that mass-timber has to offer, and the efficacy which co-rationalized design and integrated models can bring to orthodox and unusual structures alike. As a consequence, this research serves as a precedent for structural detailing-based generative architecture and collaborative work in the future.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

Bonded-in rod joints have several advantages over the conventional type of joints in terms of performance, cost and aesthetics. The use of basalt fibre reinforced polymer (BFRP) rods would result in lower weight of the joint and improved resistance to corrosion but there appears to be little or no investigation on the use of these rods in the bonded-in rod technique. The aim of this research was to examine the behaviour of bonded-in BFRP and steel rods and to propose design models to enhance current knowledge in bonded-in rod technology. The mechanical properties of the timber members were characterised so as to predict the behaviour of donor and spliced beams for the proposed stressed model. Pull-out tests of the rods were conducted to investigate some factors that affect joint capacity and based of the results bonded-in rod timber beams were fabricated and tested for ultimate capacity and flexural stiffness. An analytical model based on the interfacial tress-strain interaction of the BFRP rods with the adhesive layer and the timber members was developed to predict pull-out capacity of the samples. Average shear strength from steel pull-out tests was also used to propose a design equation for pull-out capacity of steel samples. In both the BFRP and steel samples, good agreement with the tests results was observed. A trapezoidal timber compressive stress model was developed to predict ultimate moment capacities of steel and BFRP timber beams. Good agreement was found between the theoretical and bonded-in steel rod beams whereas results form bonded-in BFRP rod beams were lower due to tensile splitting. Bonded-in steel beams recorded higher stiffness than the theoretical stiffness, whereas there was strong agreement between the theoretical predictions and BFRP beam tests. Thus, the presented models may serve as a useful reference for future design of bonded- in rod joints.

Timber gridshells are a very efficient way of covering large spaces while also providing a unique architectural and material quality. As this can still be considered an emergent technology, the design of such buildings has relied on a relatively substantial amount of experimental work. This thesis, upon reviewing the design and construction processes of previous timber gridshells, puts forward a structural model that aims to represent the true nature and specifics of single and double-layered timber gridshells. The parametrically determined geometry of a computational prototype is described and used as a basis for a non-linear elastic numerical analysis. Particular attention is given to modelling the connections between the timber laths that provide composite bending action in a double layer grid. The deformation behaviour and the imperfection sensitivity are assessed with a view to understanding how gridshells respond under different conditions. A new gridshell will inevitably be analysed with computer software, but the information presented in this dissertation will be useful for scheme design as well as the calibration of the computer analysis.

This project investigated the ignition properties of New Zealand Timbers and timber products. The ignition test on the wood was according to the British Standard BS 476: Part 13, 1987 using ISO ignitability apparatus. The ignition time for each sample was recorded and correlated by seven correlations. These seven correlations are: 1) Mikkola and Wichman 2) Tewarson 3) Quintiere and Harkleroad 4) Janssens 5) Toal, Silcock and Shields 6) Delichatsios, Panagiotou and Kiley 7) Spearpoint and Quintiere Six types of wood, Macrocarpa, Beech, Rimu, Radiata Pine, Plywood and medium density fiberboard (mdf) were tested at constant heat flux lower than 40 kW/m² until ignition did not occur within 20 minutes. Each type of wood was tested at two different thicknesses, 20 mm and 40 mm. The repeatability and reproducibility were also determined. It was found that the results such as critical heat flux, thermal inertia, ignition temperature, Thermal Response Parameter (TRP), Flux Time Product (FTP) and so on were different from one correlation to another. It is hard to say which one is the best technique in estimating the ignition properties ofNew Zealand wood, but one can get an idea of which methods will give higher or lower results. Another words: the tendency of each method to under-predict or over-predict the results. Both the 20-mm and 40-mm wood behaved as thermally thick (some thermally intermediate) solids and they have very close values of minimum heat flux and critical heat flux.

A timber-concrete composite (TCC) combines timber and concrete, utilising the complementary properties of each material. The composite is designed in such a way that the timber resists combined tension and bending, whilst the concrete resists combined compression and bending. This construction technique can be used either in new build construction, or in refurbishment, for upgrading existing timber structures. Its use is most prolific in continental Europe, Australasia, and the United States of America but has yet to be widely used in the United Kingdom. To date, the topping upgrades used have been 40mm thick or greater. Depending on the choice of shear connection, this can lead to a four-fold increase in strength and stiffness of the floor. However, in many practical refurbishment situations, such a large increase in stiffness is not required, therefore a thinner topping can suffice. The overarching aim of this study has been to develop a thin (20mm) topping timber-concrete composite upgrade with a view to improving the serviceability performance of existing timber floors. Particular emphasis was given to developing an understanding of how the upgrade changes the stiffness and transient vibration response of a timber floor. Initially, an analytical study was carried out to define an appropriate topping thickness. An experimental testing programme was then completed to: characterise suitable shear connectors under static and cyclic loads, assess the benefit of the upgrade to the short-term bending performance of panels and floors, and evaluate the influence of the upgrade on the transient vibration response of a floor. For refurbishing timber floors, a 20mm thick topping sufficiently increased the bending stiffness and improved the transient vibration response. The stiffness of the screw connectors was influenced by the thickness of the topping and the inclination of the screws. During the short-term bending tests, the gamma method provided a non-conservative prediction of composite bending stiffness. In the majority of cases the modal frequencies of the floors tested increased after upgrade, whilst the damping ratios decreased. The upgrade system was shown to be robust as cracking of the topping did not influence the short-term bending performance of panels. Thin topping TCC upgrades offer a practical and effective solution to building practitioners, for improving the serviceability performance of existing timber floors.

Given the neoclassical assumptions of optimizing economic agents, perfect information, perfect competition, and productive efficiency, timber supply is a dynamic process. Different discrete-time dynamic timber supply models and their solution methods are compared and their common elements derived. A continuous-time model is derived, but not solved. The discrete-time timber supply model is then incorporated into a dynamic multi-sector model and a dynamic general equilibrium model. In the multi-sector model, all household's utility functions are aggregated into a single community utility function which is maximized subject to the technology of the economy. The technology for the forest sector is the same as in the discrete-time dynamic timber supply models. Wood is treated as an intermediate input into the production of consumer goods. The technology of the consumer goods sectors is based on the technology used in computable general equilibrium models. The optimal steady state problem for this model is discussed, and the solution for an example problem is presented. Disaggregating the utility function is necessary for modeling true general equilibrium. This greatly complicates the problem of Ending numerical solutions, but enriches the model considerably. The formulation of the general equilibrium model as an optimization problem is described, but proved rather difficult to solve. The optimal steady state problem can be solved using an algorithm developed by Scarf (1967) for finding fixed points of continuous functions. The fixed-point approach provides a reliable solution method and appears to have more potential for modeling departures from perfect competition than the optimization approach. The equivalence of the two approaches is discussed.
Ph. D.

Twelve blocks of Cross Laminated Timber (CLT) were built, tested and simulated. Three types of blocks with different laminate directions in the middle/second layers were used: 0/30/0, 0/45/0 and 0/90/0. Simulations with three-dimensional quadratic orthotropic linear elastic finite elements were conducted. The goal was to compare tested in-plane shear stiffnesses for CLT blocks made from Norway Spruce (Picea abies) boards of C24 quality with a finite element (FEM) simulated block stiffness. Three-layer CLT were studied with block dimensions of 600 x 600 x 45 mm. The first and last layer laminate directions were assumed to be 0○. The middle layer laminate directions were 30○, 45○ and 90○. A 1 mm gap was assumed between the side edges. The glued contact surfaces were assumed to be perfectly glued with rigid glue in the simulations. In the practically tested blocks a PVAc D2 classified glue was used. All blocks were simulated and tested in the same loading arrangement as the practical test set-up. The blocks were compressed in the diagonal direction. Blocks of 0/30/0 and 0/45/0 were compressed twice, once over each diagonal. The 0/90/0 blocks were compressed over one diagonal. A total of 19 practical compression tests was performed; in all cases, the displacements were measured in the force- and orthogonal direction. The stiffest loading case, measured in the force direction, was the loading arrangement 0/45/0-A. The weakest loading case, measured in the force direction, was the loading arrangement 0/30/0-B. The same result could be concluded from the FEM simulations. The calculated stiffness in the loading direction was between 1.21 – 1.87 times larger than the measured stiffness. The models pressed in the “weakest” direction gave the largest difference between the simulated and measured stiffness.

These photographs offer illustrations of the people, places, and resources along the two prominent pilgrimage trails in the Timber Mountain Caldera region. These photographs were taken during the 2006 Timber Mountain Caldera Landscape Study, the 2001 Shoshone Mountain Wind Farm Environmental Assessment, and 1999 NTS Rock Art study.

Concerns about changes in the quality of the maturing British spruce resource (principally stiffness) have raised doubts about maintaining strength grading pass-rates. Acoustic (or stress wave) instruments provide a non-destructive measurement of stiffness and are increasingly used to classify/segregate forests, trees and logs. A fundamental assumption in the use of acoustic instruments is that of constant density, yet there is little understanding of density variation within the British spruce resource. Understanding this variation is essential for understanding the accuracy of acoustic instruments, which can affect how and when they should be used. The extent of variation in density was determined experimentally from a range of sites with contrasting silviculture and environments, and trees within-site were chosen to reflect the extremes of growth rate. Variation within tree (important for log resonance measurement) was found to depend both on dominance class (i.e. relative diameter) and height within the tree. The density in the outer part of a tree (important for standing tree time of flight measurement) was found to vary with dominance class, distance in from the bark and season. Mean green density profiles of the outer part of the tree show that density ceases to be constant between dominance classes after 10 mm in from the bark. The effect of this variation could not be quantified because the propagation behaviour of the stress wave within a tree is not fully understood. An examination of wave propagation showed that it did not conform to behaviour as described in the literature and interaction with both density variation within the tree and with the tree's boundaries is likely to affect the accuracy of this technique. The utilisation of these instruments was also examined within a sawmill simulation study, to provide an alternative to simply diverting low stiffness logs to lower value, non-structural products. Exploiting the predictable within-tree stiffness variation and adjusting cutting patterns to avoid the lower stiffness core of lower stiffness logs allowed production of consistently higher stiffness battens. A reduction in twist and knot severity was also observed, but not at significant levels until the juvenile zone (first ten years) was completely excluded. All batten properties improved with increasing cambial age (number of growth rings from the pith). Alternative cutting patterns had no effect on the recoverable batten volume from within a log and showed considerable potential to improve value to sawmills.

Timber platform frame has evolved as an efficient method of construction for domestic dwellings and is experiencing continual growth in the UK due to it lending itself to off-site modem methods of construction (MMC), being environmentally efficient and exhibiting structural robustness. The challenge faced by the industry in the UK is to continue the evolutionary process such that the future demands of off-site MMC and regulatory changes are met. By conducting a study of the development of timber platform frame construction and reviewing the current and future requirements of the domestic dwelling construction market the challenges for the industry were highlighted. The business drivers of a timber platform frame manufacturer were considered and in conjunction with the information from the review an agenda of research programmes was derived. The objective of the research, although primarily from a structural timber engineering perspective, was to address the challenges faced by the industry employing a holistic approach with a view to implementing applied research. The UK procurement process for domestic dwelling construction is such that building layout is determined by architectural requirements. Building layout can have an adverse effect on structural stability and result in an inefficient system. A design review was conducted to determine the influencing factors which impinge upon system stability as a result of which recommendations for improvements were made. From the investigation the transfer of shear from a wall diaphragm to the foundation was deemed critical. Therefore, an experimental study was carried out which has resulted in an optimised specification. Further to this mathematical modelling techniques were used to demonstrate the impact that architectural layout has on stability, quantifying the financial penalty of inefficient layout and making recommendations to improve current designs. One of major priorities of the UK Government is to reduce climate change by implementing a low carbon economy with sustainable production and consumption; all with duty of care towards natural resources. Improvements to the Building Regulations (2006), in conjunction with other requirements, will result in wall U-values in domestic dwellings to be between 0.27 to 0.30W/m2K. To determine an efficient method of meeting the new regulations an all encompassing research programme was conducted with the primary function being to develop a sustainable method of achieving thermal efficiency. Another method of wall construction is Structural Insulated Panels (SIPs) and this option was reviewed. Initial work by Kermani (2005) on the structural performance of SIPs was extended to examine their racking characterisitcs with comparative studies to European and British structural codes of practice carried out. One of the key industry drivers which the review highlighted was the need for the implementation of lean technologies. The fabrication of flitch beams (timber-steel-timber sandwich configuration), used in cases of onerous load span conditions and limited depth of section, was improved through the implementation of a shot fired dowel connection method. To optimise the method of fabrication and achieve implementation an extensive laboratory study was carried out the results of which are compared to European structural codes of practice with recommendations made for design. The implementation of off-site MMC methods results in a change in associated risk during construction from minor consequence and high risk to major consequence and low risk. The crane erect method of timber platform frame construction optimises on-site performance in terms of both time and cost and reduces the requirement of working at height, which on average causes almost one fatality every week. The biggest health and safety risk associated with the crane erect method is failure of the roof system when being lifted into position. Using an analytical model, verified by full scale laboratory testing, a range of lifting conditions were researched and a best practice lifting procedure was developed which allows the safe lifting of standard roof systems used in domestic dwelling construction.

Connections and fasteners play an essential role in the determination of strength and stability, ductility and robustness, i.e., the overall behaviour of timber structures. In particular, connections subjected to static loads are to be investigated in terms of strength and stiffness, whereas the ones designed to withstand cyclic (e.g., seismic) loads need also the definition of their complete hysteretic response. This Ph.D. dissertation focuses on the behaviour of modern connections being developed and employed in timber engineering. An initial overview on mechanical connections employed in timber structures and their evolution is reported in the introductive section of this thesis. Advantages as well as critical issues of traditional connections are the motivations for the evolution and the improvements brought by innovative connections. Two different applications of innovative timber connections are analysed and hereby discussed, each one facing different issues. The first one claims to give an insight into modern screws employed in Timber-concrete composite (TCC) structures, where the major objective is to achieve maximum strength and above all stiffness. The second is directly focused on the cyclic performance of modern connections employed in Cross Laminated Timber (CLT) structures where dissipative capacity and structural damping are of utmost importance. Consequently, the present manuscript is subdivided into two main parts. The first part deals with TCC joints realized with modern screws. The key-point to guarantee adequate mechanical performance to these composite structures is the use of connectors that demonstrate sufficient shear strength and stiffness at the interface between timber beam and concrete slab independently of the presence of an intermediate layer. Modern cylindrical connectors, such as self-tapping screws, are rising interest because they combine remarkable performance, when their withdrawal capacity is exploited, and quickness of execution especially in case of onsite installation. In this paper, a theoretical approach to calculate shear strength and stiffness of TCC joints made with inclined screws is discussed and compared to current design procedures. Furthermore, a report on short-term push-out tests of TCC joints realized with inclined self-tapping screws carried out varying fastener arrangement, diameter and concrete type is given. Consequently, a comparison between the results obtained with the theoretical method and experimental tests is reported and critically discussed in terms of both strength and stiffness. The last section of the first part present the design of an innovative connector that combines the use of self-tapping screws and a glass-fibre reinforced polymer (GFRP) element as components to realize structural TCC joints. FRP is being used in civil engineering since decades, but most of these applications utilize pre-impregnated thermosetting composites, the most common of which is carbon fibre-reinforced polymer (CFRP). On the contrary, injection moulded thermoplastic materials are relatively new and lack of history of their use in civil infrastructures. The aim is to develop a connection that solves typical installation issues of inclined screws and avoids stress concentration issues that may occur in the concrete layer. Numerical simulations, carried out to design this particular joint and exploiting a hybrid approach, are described in detail. Then, results from the experimental tests conducted to investigate the behaviour of the device subjected to shear loading conditions are compared with the analytical predictions valid for inclined screws previously described. The second part of this work focuses on the developing of an innovative earthquake-resistant connections employed for CLT structures. The seismic performance of CLT buildings is mainly related to the capability of joints to perform plastic work, since timber elements have limited capability to deform inelastically. Nowadays, the use of hold-down and angle bracket connections, which were originally developed for platform-frame constructions, has been extended also to CLT buildings. Nevertheless, the dissipative capacity of light-frame buildings is mainly diffused in nailing between frames and panels while, in CLT walls, the dissipative contribution is exclusively assured by ductile joints connecting the panels. The need of more reliable connections that provides well predictable and stable hysteretic behaviour, reduced pinching phenomenon (caused by the wood embedment) and strength degradation, justifies the continuous development of “innovative” connections. In this work, a newly developed connection element that overcomes the aforementioned issues and works for both tensile or shear loads is designed and assessed, and various significant aspects are discussed. Initially, the design procedure of the connection element and preliminary experimental tests that validates the numerical predictions are illustrated. Then, improved versions of the device are illustrated and their experimental results reported with particular attention in describing their hysteretic response and coupled shear-tension strength domain. In this work, an important role is also given to the application of the capacity design criteria applied at the joint level in order to guarantee the best exploitation of the connection’s dissipative capacity. Therefore, theoretical concepts, which describe the overstrength of traditional and innovative connections, confirmed by experimental tests of the brackets anchored to a CLT panel, are also given. In the last chapter is presented a numerical model that, following a macro-element approach, reproduces the actual cyclic response of the investigated device when subjected to combined shear-tension loads. Finally, the results of Non-Linear Dynamic Analyses of a case study CLT building realized which such model are reported and the seismic capacity of the case study building is evaluated. With these two examples, this thesis aims to give an original contribution in the evaluation of performance of innovative connection systems for timber structures, combining the use of theoretical, numerical and experimental models, and highlighting the emerging differences with respect to the use of traditional fasteners and connections.
Le connessioni e gli elementi di fissaggio svolgono un ruolo essenziale nella determinazione della resistenza, stabilità e solidità, ovvero nella risposta globale delle strutture del legno. In particolare, le connessioni soggette a carichi statici devono essere studiate in termini di resistenza e rigidezza, mentre quelle progettate per resistere a carichi ciclici (ad es. sismici), necessitano anche della completa definizione della loro risposta isteretica. Questa tesi si concentra sul comportamento dei collegamenti moderni sviluppati e impiegati nell'ingegneria del legno. Una prima panoramica sulle connessioni meccaniche impiegate nelle strutture del legno e la loro evoluzione è riportata nella sezione introduttiva di questa tesi. Vantaggi e criticità delle connessioni tradizionali sono le motivazioni dell’evoluzione e dei miglioramenti prodotti dalle connessioni innovative. Vengono analizzate e discusse due diverse applicazioni di connessioni per strutture in legno, ognuna delle quali espone aspetti e problematiche diverse. Il primo afferma di dare una panoramica delle moderne viti utilizzate nelle strutture composte legno-calcestruzzo (TCC), dove l'obiettivo principale è ottenere massima resistenza e ancor più rigidezza. Il secondo, è incentrato direttamente nell’analisi delle prestazioni cicliche delle connessioni moderne utilizzate nelle strutture in CrossLam (CLT) in cui la capacità dissipativa e lo smorzamento strutturale sono della massima importanza. Di conseguenza, il presente manoscritto è suddiviso in due parti principali. La prima parte riguarda le giunzioni legno-calcestruzzo realizzate con viti moderne. Il punto chiave per garantire prestazioni meccaniche adeguate a queste strutture composite è l'utilizzo di connettori caratterizzati da un'adeguata resistenza e rigidezza tra trave di legno e soletta di calcestruzzo, indipendentemente dalla presenza di uno strato intermedio. I connettori cilindrici moderni, come le viti autofilettanti, possiedono un crescente interesse perché combinano elevate prestazioni, se è sfruttata la loro elevata capacità ad estrazione, e rapidità di esecuzione. In questo lavoro viene proposto un approccio teorico semplificato per calcolare la resistenza al taglio e la rigidezza dei giunti TCC realizzati con viti inclinate e poi confrontato con le attuali procedure di progettazione. Inoltre, viene fornito un rapporto sulle prove di push-out a breve termine di giunti TCC realizzati con viti autofilettanti inclinate, effettuate con vari tipi di fissaggio, diametro e tipo di calcestruzzo. Di conseguenza, viene anche riportato un confronto tra i risultati ottenuti con il metodo teorico e le prove sperimentali e viene discusso criticamente in termini di forza e rigidezza. L'ultima sezione della prima parte comprende la progettazione di un connettore innovativo che combina l'utilizzo di viti autofilettanti e polimero termoplastico rinforzato con fibra di vetro (GFRP) per realizzare giunti TCC strutturali. Gli FRP vengono utilizzati nell’ingegneria civile da decenni, ma la maggior parte di queste applicazioni utilizza compositi termoindurenti pre-impregnati, il più comune dei quali è il polimero rinforzato in fibra di carbonio (CFRP). Al contrario, i materiali termoplastici sono relativamente nuovi e mancano di storia nell'utilizzo nell'infrastruttura civile. Le simulazioni numeriche, effettuate per progettare questo giunto, sono descritte in dettaglio. Quindi, i risultati delle prove sperimentali condotte per esaminare il comportamento del dispositivo sottoposto a condizioni di carico di taglio sono confrontati con le previsioni analitiche descritte. La seconda parte di questo lavoro si concentra sullo sviluppo di collegamenti innovativi impiegati per le strutture in CLT. La prestazione sismica degli edifici CLT è principalmente legata alla capacità dei collegamenti di plasticizzarsi, poiché gli elementi del legno hanno una capacità limitata di deformazione inelastica. Oggi, l'utilizzo di connessioni quali hold-down e angolari, originariamente sviluppati per costruzioni tipo platform-frame, è stato esteso anche agli edifici CLT. Tuttavia, la capacità di dissipazione degli edifici a telaio è diffusa soprattutto nella connessione telaio-pannello, mentre nelle strutture in CLT il contributo dissipativo è assicurato esclusivamente da connessioni duttili che collegano i pannelli. La necessità di una connessione più affidabile che fornisca un comportamento isteretico prevedibile ed affidabile, un fenomeno ridotto di “pinching” (causato dal rifollamento del legno) e una degrado di resistenza giustifica lo sviluppo continuo di connessioni "innovative". In questo lavoro è stato progettato e valutato un elemento di connessione che sormonti i problemi sopradescritti e che lavora sia per i carichi di trazione che per taglio, e ne vengono discussi gli aspetti più significativi. Inizialmente viene illustrata la procedura di progettazione dell'elemento di connessione e dei test sperimentali preliminari che convalidano le previsioni numeriche. Successivamente vengono descritte le fasi di progettazione e test di ulteriori versioni migliorate delle staffe dissipative e sono riportati i loro risultati sperimentali facendo particolare attenzione nel descrivere la loro risposta isteretica e il dominio di resistenza tensione-taglio. Un ruolo importante in questo lavoro è dato all'applicazione dei criteri di gerarchia delle resistenze (progettazione in capacità) a livello di connessione al fine di garantire il miglior sfruttamento della capacità dissipativa della connessione. Di conseguenza, vengono forniti concetti teorici che descrivono l’applicazione di tali concetti a connessioni tradizionali e innovative, e confermate da prove sperimentali delle staffe oggetto di studio ancorate a un pannello CLT. Infine, i risultati di simulazioni numeriche dettagliate e prove cicliche quasi-statiche sono state utilizzate per sviluppare un modello di macro-elemento implementato in un codice numerico che ha permesso di determinare le prestazioni sismiche di un edificio caso studio in CLT realizzato con tali connessioni. Con questi due esempi la presente tesi mira a definire un originale procedura di valutazione delle performance delle connessioni innovative per legno, combinando l'uso di modelli teorici, numerici ed analisi sperimentali e mettendone in evidenza le differenze emergenti rispetto all'impiego di sistemi di connessioni tradizionali.

The aim of this research work is to develop reliable strategies to assess the durability of timber structures investigating the natural hazards affecting the safety and the life-expectancy of timber buildings. From an all encompassing point of view, the life-expectancy of timber buildings was predicted considering the effects of a fungal attack on the durability of a timber structural element. The prediction of life-expectancy of timber buildings was set up through a risk-based approach consisting of (i) the analysis of the state of the art, (ii) the definition of risk classes and decision trees, (iii) the prediction of the decay. This approach was used for the structural elements of all critical points of a timber building (i.e.: the wall-foundation connections, the balconies, the openings, the wall and floor, and the roof). The analysis of the state of the art allowed to define the decision trees that address all the possible scenarios where water can intrude within the construction details that most affect the durability. Based on a thorough review of the major European standards addressing timber “use-classes”, five risk classes were defined associating the potential hazards to the possible moisture content. The decision trees can associate one of these risk classes to a detail under analysis providing a straightforward indication about the exposure of a timber structural element to decay due to fungal attack. The allocation to a risk class allows to evaluate the leading parameters of a decay prediction model based on suitable functions available in the literature. This procedure can apply directly to the design process of a timber building, while inspection procedures were defined to support the assessment of existing timber buildings. Selected case studies were analysed to compare the results of the risk-based procedure to the outcomes of the inspections. Eventually, a procedure updating of the decay prediction model based on experimental evidence is introduced, together with a software still under development named TSafe that facilitates the application of the methodology by the stakeholders involved in the project.

ABSTRACT THE PERFORMANCE OF MEDIUM AND LONG SPAN TIMBER ROOF STRUCTURES: A COMPARATIVE STUDY BETWEEN STRUCTURAL TIMBER AND STEEL ERTASTAN, Evren M.S, in Building Science, Department of Architecture Supervisor: Assoc. Prof. Dr. Ercü
ment ERMAN December 2005, 174 pages This thesis analyzes the performance of structural timber and steel in medium and long span roof structures. A technical background about roof structures including structural elements and roof structure types, span definitions, and classification of roof structures are discussed. Roof structures are detailed with traditional and the contemporary forms. The thesis comprises the comparison between structural timber and steel by using structural, constructional and material properties. Structural forms and the performance of timber and steel are discussed. The research also includes the roof structures built with structural timber in Turkey, application, marketing and examples in Turkey are indicated. In the conclusion part the performance criteria of timber and steel are summarized, the researcher has prepared a table to compare the performance of timber and steel. Keywords: Timber, Steel, Roof, Structure, Span

Huvudmålet med detta examensarbete var att undersöka om det för Södra timber är ekonomiskt hållbart att tillverka engångspallar till pelletsproduktionens tilltänkta säckningsanläggning i Långasjö, gentemot att köpa in engångspallar från en extern leverantör. Detta gäller då för 30 000 engångspallar om året. Intervjuer togs på Södra timber i Långasjö om vilket virke som var lämpligt från företagets sida att bli av med. Detta visade sig vara brädor av 19x75 mm och 75x75 mm. Dessutom beslutades i ett tidigt skede att en engångspall med måtten 1200x800 mm är en bra lösning då detta är europastandardens mått. Olika alternativ togs fram för hur man skulle kunna ta fram materialet och sänka produktionskostnaderna och avsåg då brädor 19x75 och klossvirke 75x75. Enligt beräkningar behövs virkesvolymerna 564 m3 för brädor och 125 m3 för klossvirke. Vid sågningen skall också tas fram 1,8 m och 2,1 m längder till de volymer som behövs för att sedan gå tillbaka till vanlig produktion. Vid undersökning gavs också 4 st lokaler som kan vara aktuella för produktion av pallar. Fingerskarvsanläggningen är den anläggning som är i bäst skick och är i lagom storlek för den tilltänkta produktionen och har dessutom lägst transportkostnader. Därför faller förslaget om produktion i denna. Olika förslag på maskinlayouter och maskintyper togs också fram i undersökningen. Dessa hittades via bl.a hemsidor på internet. De som är med i undersökningen är enkel maskin, enkel maskin + LB 3000, platon, begagnad robot och ny robot. En sammanställning av resultatet visar att enkel maskin + LB 3000 är den som har lägst kostnad men den begagnade roboten anses bättre lämpad då produktionen kan ökas om så önskas. Dessutom är den betydligt modernare och kräver inte samma fysiska arbete.

Plans for construction of the tallest residential timber building has driven the Technical Research Institute of Sweden (SP), Linnaeus University, Växjö and more than ten interested companies to determine an appropriate design for the structure. This thesis presents a part of ongoing research regarding wind-induced vibration control to meet serviceability limit state (SLS) requirements. A parametric study was conducted on a 22-storey timber building with a CLT shear wall system utilizing mass, stiffness and damping as the main parameters in the dynamic domain. Results were assessed according to the Swedish Annex EKS 10 and Eurocode against ISO 10137 and ISO 6897 requirements. Increasing mass, stiffness and/or damping has a favorable impact. Combination scenarios present potential solutions for suppressing wind-induced vibrations as a result of higher efficiency in low-increased levels of mass and damping.