| The modern cable stayed bridge was developed as an economical bridge form capable of long spans. Currently, cable stayed spans of over 500 m (1,640 ft) are common, and spans of over 1,000 m (3,281 ft) are planned for construction. As lengths of these bridges increase, the stay cables are subjected to increasingly demanding performance requirements based on both static and dynamic load considerations.; An experimental and analytical investigation of carbon fiber reinforced polymer (CFRP) and steel stay cables was conducted in order to characterize the performance of these structural elements. This dissertation aimed to show that CFRP stay cables are less susceptible to the negative effects of both static and dynamic issues affecting the performance of bridge stay cables.; In the concept of cable stayed bridge design, the cables provide external support and stiffness to the roadway superstructure. Therefore, in terms of static load considerations, a key property of the stay cables is axial stiffness. As the length of a stay cable increases, its effectiveness, with respect to axial stiffness, decreases, due to the increased self weight of the cable. The use of CFRP stay cables can minimize this reduction in effective stiffness because CFRP cables have a significantly lower mass density relative to conventional steel stay cables.; The properties that govern the dynamic response of a stay cable are its associated mass, stiffness, and damping. As discussed, the stiffness of a stay cable is critical to its performance under static loads and, therefore, cannot practically be modified in an effort to limit dynamic response. However, modification of cable mass---using CFRP in lieu of steel stay cables---can be explored in order to avoid or limit large amplitude vibrations. In an effort to increase the damping in both steel and CFRP cables, this dissertation also investigated the application of constrained layer damping (CLD) to bridge stay cables. Traditionally, stay cable damping is provided by mechanisms that are attached near the ends of a cable. The proposed method places the damping mechanism along the length of a cable, thereby providing a new approach to stay cable damping. |
