Assessing and improving the vibration and fatigue performance of aluminium pedestrian bridges

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The use of aluminum for pedestrian bridge construction can be advantageous due to its high corrosion resistance and strength-to-weight ratio in comparison with competing construction materials. For this reason, bridge designers are starting to consider aluminum in applications where its disadvantages (e.g. lower stiffness and higher initial cost) would have previously been considered prohibitive. Although low self-weight can be an advantage during construction, light weight pedestrian bridges are susceptible to vibrations from a variety of sources, including pedestrian loading. Connection fatigue resulting from excessive vibrations induced by the live loads is also a concern. In the current Canadian design code, pedestrian bridges are neither designed for crowd loads, nor for fatigue due to pedestrian traffic, even though these failure modes may be critical for light aluminum structures. Currently, there is a great deal of uncertainty surrounding the modelling of pedestrian loads. Specifically, there is no consensus on the models to be used to represent groups of pedestrians, or on how to expand an individual pedestrian model to crowds. Very few studies thus far have successfully attempted to verify observed responses in full-scale bridges to predictions using load models, and none for bridges constructed completely out of aluminum. In order to design optimal vibration alleviating solutions for aluminum pedestrian bridges and establish load models to facilitate fatigue verification, the current proposal outlines experimental and analytical research to be conducted within the scope of several graduate thesis projects. This research will include: the development of a new load model for flexible pedestrian bridges, the testing and analysis of a full-scale aluminum pedestrian bridge specimen, and the fatigue testing and analysis of aluminum pedestrian bridge joints. The knowledge obtained from this research will advance the state-of-the-art and enable the cost-effective design of aluminum pedestrian bridges with longer spans than are currently being constructed in practice.