Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 120-124). Also available on the Internet.

Timber has been a widely used construction material throughout the history of human development and it is still popular to this day. Timber frames are a common structural form used in historical and modern day structures. An effective means to connect timber members together is via bolts or dowels due to their high strength, ductile behaviour and flexibility in application. Such joints are, however, vulnerable and prone to damage especially during seismic attacks. In order to improve the performance and longevity of timber framed structures, it is necessary to develop simple but effective strengthening schemes for dowel-type timber joints. Additionally, strategies to repair and reinstate damaged joints are also required. The main objectives of this program of doctoral research are to (1) develop strengthening and repair schemes for bolted timber joints using advanced composite materials (i.e. carbon fibre reinforced polymer, CFRP) as well as traditional materials (i.e. steel plates, epoxies and mortars), and (2) investigate the effectiveness of the schemes in improving the seismic performance of timber frames. The strengthening and repair schemes are applied to single-bolt joints and tested under monotonic load. Optimal strengthening and repair schemes are then applied to moment resisting joints and the joints are subjected to monotonic and cyclic loading. Finite element models are then assembled for the latter joint tests. The calibrated joint models are then used in finite element models of timber frames with varying number of storeys and support conditions. The seismic performances of the timber frames are investigated by conducting both nonlinear static and nonlinear time history analyses. The results of the experimental investigations and the finite element analyses show that the strengthening schemes can enhance the strength and stiffness of joints. Optimum strengthening schemes can also improve the seismic performance of timber frames. Based on the work arising from the program of research, future research needs are finally identified. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Timber has been used as a construction material in civil infrastructure throughout the world for several millennia and it is still a popular construction material to this day. Degradation of timber due to mechanical and environmental actions, as well as possible higher loads, can necessitate the need for strengthening or repair. The external bonding of fibre-reinforced polymer (FRP) composites offers a viable solution. A lack of understanding of the strength and behaviour of FRP-to-timber bonded interfaces is, however, hindering the safe and rational design of FRP strengthening measures for timber structures. The aim of this research project is to enhance understanding of the strength and behaviour of the bonded interface between timber and FRP. Important tangible outcomes of the project include the development of effective bonding systems as well as bond stress-slip models and bond strength model which quantify the bonded interface. In order to achieve these outcomes, an extensive experimental and analytical investigation is conducted. Tests are performed and reported on FRP-to-timber joints as well as FRP-strengthened beams. For the former, softwood (Pine), hardwood (Camphorwood) and glulam timber products have been tested. Variables include (i) externally bonded (EB) plates and near-surface mounted (NSM) plates, (ii) FRP plates formed in a wet lay-up procedure and pultrusion, (iii) bonded length of FRP, (iv) adhesive type, (v) adhesive thickness, (vi) timber species, and (vii) natural growth characteristics of the timber such as annual growth rings and knots. The concept of an effective bond length has been verified from the tests as well as effective procedures and materials for bonding FRP to softwoods and hardwoods. Models are also proposed and validated to quantify the bond strength and bond stress-slip relationships of the joint tests. The strengthening methods are then applied to glulam beams in order to observe the behaviour and strength of the bonding systems on a larger scale as well as on a system that bends. The bond strength model proposed from the joint tests is then assessed against the beam tests. Finally, conclusions are made on the entire program of study. Then, recommendations for future research are proposed. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

The structural performance of Rounded Dovetail Connections (RDC) has been studied experimentally and numerically to provide information needed for connection structural design. RDC are mainly used to transfer vertical shear forces, but test results show that they can carry considerable load in tension and bending. Geometric parameters, such as dovetail flange angle and dovetail height are shown to significantly effect affect the structural performance of RDC. Results show that it is impractical to determine a set of empirical equations to describe the structural performance of RDC based on basic wood material properties. RDC manufactured and tested with low and constant moisture content outperformed those evaluated under other climatic conditions, and test results demonstrate that RDC should be produced at low machine speed and with minimal a gap between the connecting members. RDC in laminated strand lumber have higher capacity and fail under larger deformations compared to RDC in western hemlock. A three-dimensional finite element method model is presented and validated with experimental tests. Good agreement is achieved between the load deformation response predicted by the model and the experimentally observed load deformation response. Therefore the model is deemed suitable for estimating the stresses needed to develop failure criteria. A failure criterion for the analysis of RDC is presented taking into account size effect in the strength of wood. Based on the experimental and numerical studies, a design equation for RDC is presented that provides the engineering community with a new design tool. Finally, self tapping screws as reinforcement have been studied and are shown to significantly improve the structural performance of RDC under vertical shear loading.

Magistro darbe atliekama medienos tūrio nustatymo svėrimo būdu galimybių analizė. Darbo objektas – Apvalioji ir smulkintoji mediena naudojama medienos drožlių plokščių gamybai. Darbo tikslas - Ištirti apvaliosios ir smulkintos medienos, skirtos medžio drožlių plokštės gamybai, tankio kitimo dėsningumus ir jos svorio konvertavimo į tūrį ypatumus. Darbo metodai - Empirinio tyrimo metodas paremtas duomenų rinkimu medieną sveriant, atrenkant mėginius ir juos džiovinant. Kiekybinis palyginimas - statistinis duomenų apdorojimas paremtas dispersine ir regresine analize ir taikant koreliacinius ryšius. Visą empirinę medžiagą sudarė 180 medvežių imtis su spygliuočių, lapuočių ir smulkintoji mediena. Tiriama medienos tankio ir drėgnio koreliaciniai ryšiai, taip pat šių parametrų kintamumas nuo medžių rūšies, meteorologinių sąlygų: juos kertant ir sandėliuojant. Darbo rezultatai. Nustatyta, kad didžiausią įtaką medienos tankiui turi medienos drėgnis, o didžiausia drėgnos medienos masė yra žiemą. Pavasarį medienos masė mažėjo, o lengviausia buvo vasarą. Didėjant medienos santykiniam drėgniui, medienos tankis didėja nepriklausomai nuo medžių rūšies, tai rodo, kad medienos drėgnis ir jo kintamumas priklauso nuo metų laiko. Tiek lapuočių, tiek spygliuočių medienos masės priklausomybės nuo santykinio drėgnio kreivė žiemos metu yra aukščiausia, lyginat su pavasario ir vasaros kreivėmis. Tai dar kartą įrodo, kad mediena drėgniausia žiemos metu. Nustatytas drėgnio... [toliau žr. visą tekstą] / In this Master's paper an analysis is carried out to calculate the probability of estimating the volume of timber using the method of weighing. Work -study : Logs and flaked wood used for producing wood cutting panelling The aim of the work: Analysing the changes in thickness of logs and flaked wood used for producing wood cutting panelling and converting its weight into bulk. Methods of work: Empiric method based on weighing the timber, sorting out the samples and drying them. Quantitative analysis - processing the statistic data based on dispersive and regressive analysis and using correlation relations. The empiric analysis covered 180 trucks of softwood, deciduous wood and cutting.The correlation between the thickness and the humidity has been analysed. It has been also analysed how the thickness and humidity change in different species of trees, meteorological conditions, cutting down the trees and storing them. The results of the work: It has been decided that the greatest influence on the thickness of the wood has the density of the wood. The greater the relative density of the timber, the bigger the thickness of the timber. And it doesn't depend on the kind of the wood. It shows that the thickness of the wood and its changing depends on the season of the year. The curve of relative density in winter is the highest if ompared with the one in spring or in winter. The rate of the variation of density has been fixed from 11,5 to 32,2 %. As it is seen the range was great... [to full text]

Timber beams with end splits were investigated in this study to determine their shear strength. Two conditions were considered: a) Group 1 had supports located near the ends with the portion of the beam extending beyond the support, and b) Group 2 had supports located right at the end of the beam subjected to a horizontal split at approximately mid height. In Group 1, seventeen beams were tested under static loading and four were tested in fatigue. In Group 2, nineteen beams were tested under static loading and four under fatigue. In Group 1, eight beams under static loading failed in shear. In Group 2, all beams under static loading failed in shear. Group 1 and Group 2 beams under static load produced average shear strength values of 4.93 MPa and 4.49 MPa, respectively. During fatigue tests, Group 1 sustained more cycles than beams in Group 2.

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För att framföra en timmerlastbil med 74 tons bruttovikt i svensk trafik, krävs ett tillstånd från Trafikverket. Tillståndet består av ett dokument som visar vilka vägar och broar fordonet får trafikera och vilka regler som gäller när man kör lastbilen. Skogsbolaget Sveaskog startade ett examensarbete med syfte att skapa möjlighet att i realtid presentera för lastbilsföraren vilka vägar och broar som är en del av transportdispensen. Detta skulle ske genom att utveckla ett kartstöd för lastbilens fordonsdator med anslutning till GPS för att visualisera dispensdokumentet med de angivna vägsträckorna och broarna. Resultatet av examensarbetet är ett kartstöd som använder tjänster från ArcGIS Online för att presentera geografisk information för användaren. Bakgrundskartan består av en grundkarta från ArcGIS Online. Över grundkartan ligger ett GIS-skikt med vägar och ett annat skikt med broar. Information om huruvida fordonet för närvarande färdas på en väg som ingår i tillståndet eller inte, samt information om regler som gäller för broar på vägavsnittet, presenteras för föraren i realtid. Denna information uppdateras vid varje uppdatering av GPS-positionen. / In order to use a timber truck with 74 ton gross weight in Swedish traffic, a permit from the Swedish transport administration is required. A document shows which roads and bridges the vehicle is allowed to traffic and what rules applies when driving the vehicle. The forest company Sveaskog started a thesis with the aim to create the possibility to determine in real time, which roads and bridges that are part of the transport permit. This should be done by developing a map support for the truck's on-board computer with connection to GPS to visualise the permit of the specified road sections and bridges. The result of the thesis is a map support using services provided by ArcGIS Online to present geographic information to the user. The background map consist of a base map from ArcGIS Online. On top of the background map is a GIS layer with roads and another layer with bridges. Information about whether the vehicle currently is travelling on a road included in the permit or not, as well as information about rules that applies to bridges on the road section, is presented to the driver in real time. This information is updated at each update of the GPS position.

Timber-concrete composite floors are a combination of timber joists and concrete topping, creating a flooring system to best utilise the advantages each material has to offer. Timber is used as the main tensile load bearing material due to its high strength-to-weight ratio, while concrete is used in floor slabs for its advantages in stiffness and acoustic separation. The strength of the system is dependent on the connection between timber and concrete, thus the connection must be strong, stiff, and economical to manufacture, to ensure that the flooring system is economically viable. This research investigated the fire performance and failure behaviour of timber-concrete composite floor systems currently under development in New Zealand, resulting in a calculation method for evaluating the fire resistance of these floors. Furnace tests were performed on two full-size floor specimens at the Building Research Association of New Zealand (BRANZ). Both floor specimens were 4 m long and 3 m wide, consisting of 65 mm concrete topping on plywood formwork, connected to double LVL floor joists. They were tested over a 4 m span, subjected to a nominal design live load of 2.5 kPa. Both floors were subjected to the ISO 834 test fire for over 60 minutes. Two separate connection types were tested; concrete notches cut into the timber beams with an incorporated shear key, and metal toothed plates pressed between the double beams. It was found that the reduction in section size of the timber beams due to the fire governed the failure mode of the floors. Due to the composite action achieved by the connections, the floor units were able to withstand prolonged exposure to the test fire, well exceeding one hour. The test data and visual observations aided in the development of a numerical model for evaluating the fire resistance of the floors. This was developed in a spreadsheet that is able to predict the expected fire resistance of these floors, taking into account some major time dependent variable properties that can have an effect on the overall performance. Load-span tables have been produced to give the estimated fire resistance of floors with differing floor dimensions, span lengths and applied loads.

Birch is the dominant deciduous tree species in Sweden but only 16 % is found in pure birch stands. The majority of the birch (51 %) is to be found in conifer dominated stands. Swedish forest land comprises approximately of 23 % mixed stands and one problem is that for mixed stands there are few management recommendations. The underlying aim of this thesis was to study the management of mixed forest stands of spruce and birch to achieve good timber quality of birch. The study was based on a literature study and measurement in a field experiment launched in 1998 by the Swedish University of Agricultural Sciences (SLU). This study indicates that it is possible to achieve good timber quality of birch in mixed stands of birch and spruce. However, it requires that birch in mixed stands with spruce should be managed similar to management programs of pure birch stands.   Keywords: Birch, spruce, timber quality, mixed stands.