Theses and Dissertations at Montana State University (MSU)
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Item Pilot study of a high capacity ductile seismic holdown for cross laminated timber(Montana State University - Bozeman, College of Engineering, 2019) Nicholas, John Howison; Chairperson, Graduate Committee: Damon FickNew manufactured wood products referred to as mass timber have allowed for greater seismic load capacities than ever before for designing wood structures. The increased capacities could allow for taller wood structures; however, traditional wood connections do not meet the seismic performance needs for new manufactured wood products such as cross laminated timber (CLT). New connection methods must be investigated to allow for the growth of the CLT industry in mid- and high-rise structures. The objective of this research is to develop a wood connection to resist larger uplift forces experienced in CLT structures and provide energy dissipation in seismic events. The connection development was performed through fastener testing using self-drilling dowel fasteners for concealed connections with steel knife plates installed in a wood member. Finite element modeling and testing of reduced section steel plate to provide a ductile response to cyclic loading was performed to determine the feasibility of this connections style. The results of the investigation indicate that reduced section steel plates that limit the connection failure to a desired location in the steel plate could greatly increase the seismic performance of CLT seismic force resisting systems.Item An investigation of a prefabricated steel truss girder bridge with a composite concrete deck(Montana State University - Bozeman, College of Engineering, 2018) Kuehl, Tyler William; Chairperson, Graduate Committee: Damon FickSteel truss girder bridges are an efficient and aesthetic option for highway crossings. Their relatively light weight compared with steel plate girder systems make them a desirable alternative for both material savings and constructability. A prototype of a welded steel truss girder constructed with an integral concrete deck has been proposed as a potential alternative for accelerated bridge construction (ABC) projects in Montana. This system consists of a prefabricated welded steel truss girder topped with a concrete deck that can be cast at the fabrication facility (for ABC projects) or in the field after erection (for conventional projects). To investigate possible solutions to the fatigue limitations of certain welded member connections in these steel truss girders, bolted connections between the diagonal tension members and the top and bottom chords of the steel truss girders were evaluated. A 3D finite element model was used to more accurately represent the distribution of lane and truckloads to the individual steel truss girders. This distribution was compared to an approximate factor calculated using an equivalent moment of inertia with expressions for steel plate girders from AASHTO. A 2D analytical model was used to investigate the fatigue strength of the bolted and welded connections for both a conventional cast in place deck system and an accelerated bridge deck system (cast integral with the steel truss girder). Truss members and connections for both construction alternatives were designed using loads from AASHTO Strength I, Fatigue I, Fatigue II, and Service II load combinations. A comparison was made between the two steel truss girder configurations and 205 ft. steel plate girder used in a previously designed bridge over the Swan River. Material and fabrication estimates suggest the cost of the conventional and accelerated construction methods is 10% and 26% less, respectively, than the steel plate girder designed for the Swan River crossing.