Four plates with centrally located circular holes were manufactured using a fiber placement technique. With two plates the fibers were steered around the holes in curvilinear trajectories. With the two other plates the fibers were placed in the conventional straight line format. For the case of the curvilinear trajectories, the fibers were continuous from one end of the plate to the other, whereas for the straight trajectories the fibers were cut by the presence of the hole. Two plates, a curvilinear fiber plate and a straight fiber plate, were tested in tension. The two other plates were tested in compression. The straight fiber plates were considered as baseline cases. Since the plates were thin, compression testing resulted in buckling and post buckling. The current work focuses on the analysis of these four plates and a comparison between the analysis and experimental results. Because of a spatial dependence of the A and D stiffness matrices for the curvilinear fiber cases, the analyses were conducted using finite element methods, and included a failure criterion. A scheme to improve the plate design is also considered. / Master of Science

Advanced composites have become one of the most popular methods of repairing and/or strengthening civil infrastructure in the past couple of decades. While the use of Fiber Reinforced Polymer laminates and sheets for the repair and strengthening of reinforced concrete structures is well established, research on the application of FRP composites to steel structures has been limited. The use of FRP material for the repair and rehabilitation of steel members has numerous benefits over the traditional methods of bolting or welding of steel plates. Carbon FRPs (CFRPs) have been preferred over other FRP material for strengthening of steel structures since CFRPs tend to posses higher stiffness. The emergence of high modulus CFRP plates, with an elastic modulus higher than that of steel, enables researchers to achieve substantial load transfer in steel beams before the steel yields. This research investigates both analytically and experimentally, the bond characteristics between ultra high modulus CFRP strengthened steel members and the flexural behavior of these members. A series of double strap joint tests with two different CFRP strip widths are carried out to evaluate the development length of the bond. Both ultra high modulus and normal modulus CFRP laminates are used to compare strengthened member performance. Steel plates reinforced with CFRP laminates on both sides are loaded in tension to evaluate the load transfer characteristics. Debonding under flexural loads is also studied for ultra high modulus CFRP strengthened steel girders. Flexural tests are carried out under 4-point bending on several small scale wide flange beams. This study also introduces the novel ultra high modulus CFRP plate strip panels for strengthening of steel bridge girders. The first field application of ultra high modulus CFRP laminates in strengthening steel bridge girders in the United States is also carried out as part of the research. Full scale load tests carried out before and after the strengthening are utilized to measure the degree of strengthening achieved and checked against the expected results. A finite element model is developed and calibrated using data obtained from the field testing of the bridge. The model is then used to evaluate the behavior of the bridge under different conditions before and after the strengthening process.