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Publication informationJournal of Sound and Vibration, 332 (25): 6685-6702Publisher Elsevier Item record/more information http://hdl.handle.net/10197/6581 Publisher's statementThis is the author's version of a work that was accepted for publication in Journal of Sound and Vibration. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Sound and Vibration (VOL 332, ISSUE 25, (2013) AbstractScour around bridge foundations is one of the leading causes of bridge failure. Up until recently, the monitoring of this phenomenon was primarily based around using underwater instrumentation to monitor the progression of scour holes as they develop around foundation systems. Vibration-based damage detection techniques have been used to detect damage in bridge beams. The application of these vibration based methods to the detection of scour has come to the fore in research in recent years. This paper examines the effect that scour has on the frequency response of a driven pile foundation system, similar to those used to support road and rail bridges. The effect of scour on the vibration characteristics of the pile is examined using laboratory and field testing. It is clear that there is a very clear reduction in the natural frequency of the pile as the severity of scour increases. It is shown that by combining state-of-the-art geotechnical techniques with relatively simple finite element modelling approaches, it is possible to accurately predict the natural frequency of the pile for a given scour depth. Therefore, the paper proposes a method that would allow the estimation of scour depth for a given observed pile frequency. Scour Monitoring: The accurate assessment and monitoring of existing structures to progressive scour has come to the fore of research in recent years [7,8]. A myriad of current technology aims to detect the existence and severity of scour around the foundation systems of existing bridge structures. Most of these technologies comprise underwater instrumentation that aim to monitor the evolution of scour holes over time. A brief summary of available instrumentation is given herein. The use of float-out devices [9] and Tethered Buried Switches [10] positioned in the soil near a bridge pier can provide a simple method of scour monitoring. These devices float out when the scour depth reaches their position and are programmed to send a remote signal to provide a warning. However, they require reinstallation upon floating out, which is a distinct disadvantage. Time Domain Reflectometry (TDR) aims to detect changes in the dielectric permittivity constants between materials that would occur at a water-sediment interface and thus has been used to detect scour [10 -12]. Devices using this method work very well at detecting the depth of scour i...

Publication informationOcean Engineering, 101 (1): 1-11Publisher Elsevier Item record/more information

Abstract:This paper describes the use of project based learning to teach design skills to civil engineering students at University College Dublin (UCD). The paper first considers the development of problem based leaning (PBL) as a tool in higher education. The general issues to be considered in the design of the curriculum for an PBL module are reviewed. Consideration of the literature on the application of PBL in civil engineering suggests that because of the hierarchical nature of engineering education, PBL is best applied in a hybrid form known as Project Based Learning. A detailed description is given of how hybrid PBL was implemented in the final year of a civil engineering degree programme is then presented. In the final section, the results of an evaluation process designed to gain an insight into students' perceptions of the PBL process are reviewed. The module which was developed at UCD provided an excellent mechanism for developing many skills including, problem-solving, innovation, group-working and presentation skills desired by graduate employers. It was clear that the students enjoyed the peer to peer teaching and increased interaction with staff and external experts which the problem solving nature of the module facilitated.

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Improved design of laterally loaded monopiles is central to the development of current and future generation offshore wind farms. Previously established design methods have demonstrable shortcomings requiring new ideas and approaches to be developed, specific for the offshore wind turbine sector. The Pile Soil Analysis (PISA) Project, established in 2013, addresses this problem through a range of theoretical studies, numerical analysis and medium scale field testing. The project completed in 2016; this paper summarises the principal findings, illustrated through examples incorporating the Cowden stiff clay profile, which represents one of the two soil profiles targeted in the study. The implications for design are discussed.

Bridge scour is the number one cause of failure in bridges located over waterways. Scour leads to rapid losses in foundation stiffness and can cause sudden collapse. Previous research on bridge health monitoring has used changes in natural frequency to identify damage in bridge beams. The possibility of using a similar approach to identify scour is investigated in this paper. To assess if this approach is feasible, it is necessary to establish how scour affects the natural frequency of a bridge and is it possible to measure changes in frequency using the bridge dynamic response to a passing vehicle. To address these questions, a novel Vehicle-Bridge-Soil Interaction (VBSI) model is developed. By carrying out a modal study in this model, it is shown that for a wide range of possible soil states, there is a clear reduction in the natural frequency of the first mode of the bridge with scour. Moreover, it is shown that the response signals on the bridge from vehicular loading are sufficient to allow these changes in frequency to be detected.

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