الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Over the last decades, a large number of cable-stayed bridges have been built around the world. These bridges act as vital links in national and local transportation networks. They also provide a cost-effective option for carrying loads over medium to large spans, from 200 m to 1100 m. Cable-stayed bridges are characterised by a long fundamental period, significant flexibility, lightweight, and low structural damping. They are quite vulnerable to large amplitude oscillations when excited by earthquake ground motions and wind pressure. The consequences of their failures are severe and associated with loss of life and injuries. So, enhancing their seismic performances has drawn increasing attention to studying their dynamic behaviour and ensuring the essential post-earthquake functionality from both engineering and academic communities. Energy dissipation systems are an effective choice to suppress the vibrations of structures and control the dynamic responses. One of the energy dissipation systems is the tuned mass damper system. It is a secondary vibration system coupled to the primary structure at suitable locations to reduce the dynamic response of the building structure subjected to wind or earthquake loads. Reduction of vibrations is accomplished by transferring part of the structural vibration energy to the damper and dissipating the energy by the inertia force. Although efforts have been made, more attention needs to be paid to studying tuned mass dampers and their effect on the performance of cable-stayed bridges. This study aims to investigate how tuned mass dampers could enhance cable-stayed bridges’ dynamic behaviour in both lateral and longitudinal directions. Finite element analysis has been performed and verified to assess the optimum value of the damper’s mass ratio by II comparing the performance of the bridge before and after incorporating the damper under seismic excitations. Different possibilities of installing single or multiple-tuned mass dampers are also suggested to find the best equipping strategy. Generally, cable-stayed bridges have long spans, so the assumption of uniform earthquake motion along the entire bridge may be unreasonable; that is why the ground motion spatial variation effect was included in the analysis. The feasibility and efficiency of using mass dampers under multi-support excitations have been examined and compared to the response due to uniform input excitations. Results show that the damper could effectively improve the bridge’s seismic performance in the lateral direction even with low mass ratios, unlike in the longitudinal direction. The damper’s efficiency is reduced in case of using an isolation system for the bridge in the lateral direction. Furthermore, using the multiple-tuned mass damper system leads to better behaviour by overcoming the single damper’s narrow band of suppression frequency. Moreover, studying multi-support seismic excitation is a necessary stage in designing cable-stayed bridges as it affects the bridge’s structural responses and damper effectiveness as well.