A Conceptual Study of Glulam Connections Using Threaded Rods and Connecting Circular Steel Profiles
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This Master thesis is a continuation of an ongoing study of connections in timber structures with the use of long threaded rods as fasteners. As a part of the research project Wood frame solutions for free space design in urban buildings, the main focus has been on developing a beam-to-column connection with moment resisting properties. A literature review on relevant theory and previous studies on the use of threaded rods in timber connections was performed. The findings gave useful knowledge for further work. A design-solution using circular steel elements to create a beam-to-beam connection between glued-laminated timber elements was developed further to create beam-to-column connections by applying the same concept. The finite element analysis software Abaqus/CAE was used for optimizing the design of the circular profiles. The aim was to achieve high initial stiffness, but also to hold the amount of strength which would allow for some yield to occur in the circular profiles before failure happened in the rods. Abaqus/CAE was also used for finding the most favorable rod-to-grain angle combination for the threaded rods installed in the connection, and for estimating the rotational stiffness. Further on, theoretical rotational stiffness was estimated with a model based on the component method established by Postdoctoral Fellow Haris Stamatopoulos. Four connections were built. Each connection consisted of a timber column and beam connected by using screwed-in threaded rods and circular profiles. The timber elements were of quality GL30c and dimensions of 140x450 mm. Two identical connections, test 1 and test 2, had two circular profiles in the upper part of the connection and one inclined threaded rod in the center of the lower part of the connection. Two connections, test 3 and test 4, had two circular profiles located in both the upper and lower part of the connection. The rod-to-grain angles and embedment lengths varied for test 3 and 4. A point load was applied on the beam surface with a moment arm of 2 meters. Test 1 and 2 did not experience failure before the tests were terminated due to limited range of the jack applying the point load. The connections sustained a maximum moment of 105 kNm and 104 kNm respectively. Test 3 sustained a maximum moment of 79 kNm and test 4 sustained a maximum moment of 133 kNm. The rotational stiffness achieved in each test was 6670 kNm/rad, 7308 kNm/rad, 8753 kNm/rad and 7769 kNm/rad for test 1, 2, 3 and 4, respectively. The design-solution showed large potential considering creating a connection with moment resisting properties, and further investigations of similar connections are desirable. The procedures of producing and mounting the connections presented few difficulties, and with some further improvements it has potential to become implementable to the building-industry. Calculations, production procedure and experimental data are included in the study, and can be used for further work with the design.