Aerodynamic control of Long span Bridges

The research program will carry out CFD and wind tunnel tests of the stability and buffet response of flexibly-mounted bridge deck models. The bridge decks will be fitted with aerodynamic control surfaces of the oscillating flap type. A combination of sensors on the deck, a digital control system and electrical actuation of the flaps will be used to increase the bridge stability in the heave-torsion mode. Quasi-three-dimensional CFD will be used first to compute flutter boundaries. The critical wind speed for flutter onset will be evaluated from the responses at different subcritical wind speeds. The system response to indicial control-surface movement will also be computed and the results used to model bridges, first on a section of the deck and later on a three-dimensional model of a full bridge. Measurements will be made, for a range of bridge parameters including deck geometry and smooth/turbulent incident winds, to assess the effectiveness of the system in increasing critical flutter speeds and alleviating buffeting and vortex-induced-vibration for full scale suspension and cable-stayed bridges. These tests will also be used to validate the numerical results.

Introduction: Vortex shedding induced vibrations occur in many areas of civil engineering. The key purpose of this project is to produce new knowledge that will facilitate the mitigation of these difficulties in a reliable and economically efficient manner. Ultra-long suspended spans are currently of great interest and the world market for these bridges is considerable. With some exceptions this is mainly an export market for the UK, and the strong UK technical base is involved in this market predominantly from a consultancy perspective. It is vital to the UK economy that this leading position is maintained in the face of competition from others - primarily the Japanese. New Knowledge: The generation of new knowledge is the primary focus of this work and will be in the area of flow control in civil engineering. By concentrating on mechanical implementations of the control system, it is suggested that flow-control-related solutions to flutter instabilities will effective, reliable and cost effective. This new knowledge will be fed simultaneously into our expert communities and the consulting industry. The first will be achieved via conference publications, oral presentations and publications in learned society journals, while the second will be achieved via collaboration and industrial interaction. Training: It is vital that the UK's top universities continue to attract and train the world's most able research students. This is important for both the well being of the universities, and as a source of trained personal for the country's industries. Projects of the type acts as a fast conduit for knowledge exchange, training and the employment of the country's most talented young scientists and engineers. Communications and engagement: The civil engineering consultancy community is well aware of the flutter problems introduced in this proposal, and so there is little need for us to convince them of the importance of this research. That said, there is a challenge to be faced in gaining acceptance for flow-control-related solutions to these difficulties. We will focus attention on the problem of gaining acceptance for control-related solutions to structural instabilities, and our proposed passive-mechanical-component based approach is motivated in part by this objective. The internet and electronic publications are rapidly replacing conventional archival journals as a means of communicating new knowledge. This derives from both the speed and easy availability of the new electronic medium. With rapid communications in mind, we believe it important that a project-specific website is established that will act as a forum for the rapid publication of reports and new results. In principle, this medium makes new finding available immediately, while convention publications means can take two to three years. As an example of a project-specific website that was established by one of the investigators we refer the reader to: http://www3.imperial.ac.uk/controlandpower/research/motorcycles Imperial College Consultants have received five consultancy engagements, both here and in the United States, as a direct result of this website. Intellectual property: Imperial College has in place standard procedures for the protection of any intellectual property that might result from this research. Both investigators are mindful of the need to protect IP resulting from EPSRC funded research and we undertake to do that.