Dynamic performance of bridges and vehicles under strong wind

Abstract

The record of span length for flexible bridges has been broken with the development of modern materials and construction techniques. With the increase of bridge span, the dynamic response of the bridge becomes more significant under external wind action and traffic loads. The present research targets specifically on dynamic performance of bridges as well as the transportation under strong wind. The dissertation studied the coupled vibration features of bridges under strong wind. The current research proposed the modal coupling assessment technique for bridges. A closed-form spectral solution and a practical methodology are provided to predict coupled multimode vibration without actually solving the coupled equations. The modal coupling effect was then quantified using a so-called modal coupling factor (MCF). Based on the modal coupling analysis techniques, the mechanism of transition from multi-frequency type of buffeting to single-frequency type of flutter was numerically demonstrated. As a result, the transition phenomena observed from wind tunnel tests can be better understood and some confusing concepts in flutter vibrations are clarified. The framework of vehicle-bridge-wind interaction analysis model was then built. With the interaction model, the dynamic performance of vehicles and bridges under wind and road roughness input can be assessed for different vehicle numbers and different vehicle types. Based on interaction analysis results, the framework of vehicle accident analysis model was introduced. As a result, the safer vehicle transportation under wind can be expected and the service capabilities of those transportation infrastructures can be maximized. Such result is especially important for evacuation planning to potentially save lives during evacuation in hurricane-prone area. The dissertation finally studied how to improve the dynamic performance of bridges under wind. The special features of structural control with Tuned Mass Dampers (TMD) on the buffeting response under strong wind were studied. It was found that TMD can also be very efficient when wind speed is high through attenuating modal coupling effects among modes. A 3-row TMD control strategy and a moveable control strategy under hurricane conditions were then proposed to achieve better control performance.