Scour is the process of sediment erosion around bridge piers and abutments due to natural and man-made hydraulic activities. Excessive scour is a critical problem that is typically handled by enforcing design requirements that make the submerged structures more resilient. The purpose of this research is to demonstrate the feasibilities of the Optical- Based Green Laser Scanner and HydroLite Sonar in a laboratory setting to capture the 3D profile of simulated local scour holes. The Green Laser had successfully reconstructed a 3D point-cloud imaging of scour profiles under both dry and clear water conditions. The derived scour topography after applying water refraction correction was compared with the simulated scour hole, and was within 1% of the design dimensions. The elevations at the top and bottom surfaces of the 6.5-inch scour hole were -46.6 and -53.11 inches from the reference line at the origin (0,0,0) of the laser scanner. The HydroLite Sonar recorded hydrographical survey points of the scour’s interior surface. The survey points were then processed using MATLAB to obtain a 3D mesh triangulation. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Thesis (Ph. D.)--University of Nevada, Reno, 2006. / "May, 2006." Includes bibliographical references (leaves 105-107). Online version available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Identifying damage of a bridge from a vehicle moving over it is an attractive idea especially for those bridges without structural health monitoring systems as it is faster than putting sensors on the bridges. Many parts of highways and railways have been constructed on bridges and it is important to ensure that they are in good conditions. Therefore a large amount of bridges need to be monitored and for the sake of economy the monitoring should be efficient. If an instrumented vehicle can identify the occurrence and locations of damage by running over the bridges, it would save a lot of labor and time. As acceleration is easier to acquire, it is used as the main signal for damage detection. Research in this area is relatively little, not to mention the need to take into account road surface roughness and experimental verification. Frequencies can be conveniently extracted from the vehicle response. The damage can hence be identified based on the relationship between the change of frequencies and the fractional change of strain energy. A vehicle-bridge interaction system is used to simulate the process of a vehicle running over a bridge and obtain the vehicle response for investigation. The proposed method can identify damage of simply supported and multi-span continuous bridges taking into account road surface roughness and measurement noise. They are also validated in the laboratory where a simply supported bridge is modeled using an aluminum beam and the vehicle is modeled with aluminum vehicles. This method can limit the damage location to two potential locations. The multi-level multi-pass strategy makes use of the identification from the above method, applies genetic algorithm and lets the vehicle run over the bridge at various speeds. The unique damage location can then be identified. A numerical study for simply supported bridges and multi-span continuous bridges has verified its effectiveness. Continuous wavelet transform (CWT) can identify local changes in a signal as damage is assumed to cause local change to the vehicle response, which makes it suitable for damage detection from vehicle response. However, the road surface roughness and measurement noise often mask the information about damage. Smoothing technique and damage indicators are proposed to help with the identification. By validating the method with a numerical vehicle-bridge interaction system and model tests in the laboratory, the damage can be correctly identified. Additional masses and sinusoidal excitation force can help with the identification too. Repeated application of CWT involves applying the CWT to the coefficients of continuous wavelet again and again, which can also improve the results. If CWT is treated as a mathematical microscope, repeated application of CWT is like amplifying the signal several times. The effectiveness of the method has been verified numerically and experimentally. In summary, a convenient and efficient technique to test the conditions of bridges by putting sensors on a moving vehicle is proposed and the method is verified by numerical and experimental studies. It can provide an alternative or a useful complement to conventional structural health monitoring systems. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Structural reliability techniques can be employed to evaluate the fatigue performance of fracture-critical members in steel bridges. In this dissertation, two fatigue reliability formulations that can be applied for most details in steel bridges are developed. For details classified according to AASHTO fatigue categories, a limit state function related to the number of stress cycles leading to failure based on Miner’s rule is used; for details not classified according to AASHTO fatigue categories, a limit state function based on linear elastic fracture mechanics and expressed in terms of crack size and growth rate is employed. With the application of fatigue reliability analysis, a procedure for inspection scheduling of steel bridges is developed to yield the optimal (most economical) inspection strategy that meets an acceptable safety level through the planned service life. This inspection scheduling problem is modeled as an optimization problem with an objective function that includes the total expected cost of inspection, repair, and failure formulated using an event tree approach, with appropriate constraints on the interval between inspections, and a specified minimum acceptable (target) safety level. With the help of several illustrations, it is shown that an optimal inspection scheduling plan can thus be developed for any specified fatigue details or fracture-critical sections in steel bridges. A second optimal inspection scheduling procedure is formulated that takes into consideration crack detectability (or quality) of alternative nondestructive inspection techniques. This procedure based on Monte Carlo simulation of crack growth curves yields an optimal inspection technique and associated schedule for a given fracture-critical member in a steel bridge for minimum cost and a target safety level while also taking into account probability of detection (POD) data for candidate nondestructive inspection techniques. Comparisons between the reliability-based procedure and the POD-based procedure for optimal inspection scheduling are discussed. Both scheduling strategies, when contrasted with ad hoc periodic inspection programs for steel bridges, are recommended because they are rational approaches that consider the actual fatigue reliability of the bridge member and account for economy as well as safety. / text

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