Thesis (M.E.F.E.)--University of Canterbury, 2006. / Typescript (photocopy). "January 2006." Includes bibliographical references (leaves 99-101).

To make low grade lumber into high-valued products, finger-jointing is a widely used method in the timber industry. In certain situations, chip-out occurs degrading the quality of the joint. To better understand the machining process, a beam-type dynamometer based on strain gages was designed to analyze the dynamic cutting forces parallel and vertical to the feeding direction. The test results indicate that the dynamometer design was sensitive enough to measure small force changes at relatively high frequencies during the cutting operation. The test conditions were set as close as possible to that in industry. Cutting force behavior of the rotating cutterhead was examined, and test samples with different fiber angles were used for inspecting the influences on the chip-out occurrence and cutting forces. The results show that cutting forces are determined by the density of the wood and the maximum chip thickness. Slight differences in tool shape and the balance of the cutterhead can vary the cutting force behavior. The occurrence of chip-out is dependent on the fiber angle and the chip thickness. No relationship between chip-out and cutting force was found, within the sensitivity of the dynamometer. Fiber angle has some effect on the cutting force, and also influences the cutting surface quality. A high speed video camera was also employed to visually observe the formation of chip-out. Frame by frame analysis showed that the chip-out occured when a knife passed through the trailing edge of the cut-block, and the failure developed in the sequel cuts. Cutting force and chip-out models were developed from the experiment results, and can be used to reduce chip-out and increase recovery during finger-jointing in ponderosa pine cut-stock operation. / Graduation date: 1993

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

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 105-113). Also available via the Internet.

Thesis (M.E.F.E.)--University of Canterbury, 2007. / Typescript (photocopy). "February 2007." Includes bibliographical references (p. 129-133). Also available via the World Wide Web.

This paper presents the results of testing to determine the appropriateness of the seismic load duration factor and to investigate the possible effect of previous load history from cyclic loading on connection reserve capacity and ductility. The single shear nail and bolt connection types tested represent common connection geometries used in wood construction in the United States. The results of two methods of fully reversing cyclic loading of connections are presented. The first method was a load-controlled test with the applied cyclic loads acting at specified percentages above current nominal design values. The sets of specimens were then ramped to failure and the results were compared to a monotonic control set of specimens to determine if any reduction in connection capacity or ductility had occurred as a result of the cyclic loading. From the load-controlled cyclic testing, it was found that previous cyclic loading at load levels as high as twice current nominal design loads did not adversely affect connection capacity. The second cyclic loading method was a displacement-controlled test that involved successive phases at increasing displacement levels. Each phase consisted of a peak displacement, followed by a series of three decay cycles, then by a series of three cycles at the original peak displacement, the third of which is used to determine the stabilized system. The process is repeated at increasing incremental levels of displacement. The phased displacement stabilized load-displacement curve was fit to an equivalent energy elastic-plastic system for determination of connection parameters. Results from the two cyclic test methods, and from monotonic testing, indicate that the current load duration factor for wind and seismic loading is justified. / Master of Science / incomplete_metadata

In this study, general models of the capacity of threaded fastener joints were developed from extensive experimental tests. One study objective was to develop a general model of threaded fastener withdrawal strength applicable to joints containing fasteners with widely varying thread geometries. A total of 419 tests of joints using six different fasteners and five species were tested. A multiplicative model containing wood specific gravity and the wood volume contained within the fastener threads provided very accurate predictions of withdrawal strength. A second study objective was to assess the accuracy of existing design criteria for threaded fastener joints subject to combined axial withdrawal and lateral shear loading. A total of 321 joints using 3 different fasteners and two species were tested at five angles between 0° and 90° to fastener axis. Little to no interaction was found between the lateral and withdrawal force components on joint capacity. Current design philosophy in the National Design Specification generally yielded conservative predictions of actual joint capacity. Improved design criteria suggested by experimental results were derived. A pilot study was also conducted to assess the influence of wood desorption on the withdrawal resistance of tapping screws. Forty joints of two moisture conditions, green and dry at insertion and two species were tested in withdrawal. In general, maximum and proportional limit loads were not affected by desorption whereas stiffness was significantly reduced for joints which desorbed after insertion. / Master of Science

Thesis (M.S.) -- Mississippi State University. Department of Forest Products. / Title from title screen. Includes bibliographical references.

På en byggarbetsplats kan man ibland behöva sammansätta två eller flera träkomponenter till en träkomponent med rätt dimension. Det sker oftast genom spikning men det finns också möjlighet att limma ihop träkomponenter ute på en byggarbetsplats. Limning är inte alls lika förekommande på grund av de krav som ställs på limning av bärande konstruktioner och kringliggande miljö varför limning i princip endast sker i fabriksmiljö. I denna studie utförs en jämförelse mellan sammansättning av träreglar till en träpelare med avseende på hållfasthet och ekonomi. Detta jämförs dessutom med att köpa in pelare av trä med rätt dimension. I studien behandlas dessutom möjligheten att limma ute på en byggarbetsplats och hur limningen ska utföras på ett korrekt sätt. Studien har genomförts med hjälp av de standarder som finns för beräkningsregler för dimensionering av bärverk, eurokoder. Kostnadsberäkningar har genomförts för material och utförandearbete med hjälp av marknadspriser för material och enkla beräkningar för utförandearbete. En intervju har genomförts för att besvara möjligheten att limma ute på en byggarbetsplats med lim för bärande konstruktioner. I studien har beräkningar utförts för två samt tre sammansatta träreglar och jämförts med enkla pelare i liknande dimensioner. Spikad pelare har en avsevärt lägre bärförmåga än limmad pelare som är utförd korrekt. Spikad pelare har beräknats med olika avstånd mellan spikar och limmad pelare är beräknad med två olika lim. Kostnaderna för material och utförandearbete är ganska generella men är bara en liten del av de totala kostnaderna. Vart byggarbetsplatsen är placerad, vilka verktyg och material som finns på plats och vilka förutsättningar för att utföra limningen korrekt är faktorer som är avgörande för den totala kostnaden. Ett limförband är känslig och viktigast är att applicera rätt mängd och jämnt utbrett över träytorna. Vad som dessutom ska tas till hänsyn är kringliggande miljö såsom smuts, damm, temperatur och fuktighet. För att uppfylla dessa krav ute på en byggarbetsplats måste en fabriksmiljö skapas i form av väderskydd, tält, arbetsbod eller liknande.

The mechanical behavior of timber beams with a slotted-in steel plate connection is studied by creating a numerical model that is able to simulate the global bending behavior, the global load carrying capacity and the nonlinear plastic fastener force distribution in the connection. Experimental results from Material Testing Institute (MPA), University of Stuttgart were used to verify the simulation results from this study. The modeling of both the timber beams and the mechanical connections is performed with shell, beam and nonlinear connector elements. Three models were created, where the first model was a single-dowel double shear joint model to study the ability to use structural elements in the modeling of the test beams. It was used to simulate some of the basic failure modes in Eurocode 5 (EC5). The second model was a beam model used to simulate the bending of a jointed timber beam with a slotted-in steel plate connection, where only two connector elements were used to model the joint behavior of each dowel group. It can be used to study the global deflection and the load carrying capacity of the jointed timber beams. The third model was a combined beam-shell model where the beam elements are used for the timber parts outside the connection area and the fasteners, while the shell elements are used for the slotted-in steel plate and the timber parts within the connection area. It uses two nonlinear connectors to connect each dowel to the wood and a pure coupling constraint to connect the dowels to the slotted-in steel plate. This model can simulate the same phenomena as model two and also the development of the elasto-plastic shear force distribution in all the dowels. All the models were created using parameterized Python scripts, which makes it possible to easily change different input parameters. Most of the modeling results show good agreement with both experimental results and with calculated load carrying capacity results for individual dowels according to EC5. The use of the structural elements (beam, shell, and connector elements) was found to result in much less computational time compared to the use of solid elements.