| Stay cables are main functional components of cable-stayed bridge to transfer external loads from bridge girder to bridge tower.Due to light weight,low inherent damping and slenderness characteristics,cables are vunlerable to environmental excitations such as wind and wind/rain.Excessive long-time vibration extremely induce damage of HDPE protective layer of stay cable,and the infiltration of water and corrosive agents may cause the corrosion and fatigue-corrosion of the high-strength wireand shorten the service life of the cable.Excessive vibrations may also cause uneasiness of pedestrians and drivers.Aerodynamic countermeasures,damping devices and cross-ties are applied to restrain these harmful vibrations.And these measures may hybrid applied for better mitigation effects.Shape Memory Alloy(SMA)has the potential to be applied for cable vibration mitigation as the super elasticity and high damping,which can effectively dissipate the vibration energy as high damping cross-ties.However,the vibration mechanisms and design methods for cable system with additional SMA cross-link are not established yet.Particularly,the effects of damping of the cross-tie and temperature effect of SMA on the vibration characteristics of cable system are not clear.This paper tries to explore the vibration mechanism of cable networks interconnected by SMA cross-ties that can be simplified to parallel damper and spring.First,the free vibration of two cables interconnected by a grounding cross-tie is developed,and the damping characteristics of cross-tie are mainly analyzed,which can simplify the cross-tie into damper.The relevant limit solutions are classified and discussed,and the modal evolution characteristics and mode shape of the twin cable system are analyzed.The effect of change of the location of damper and damping coefficient on mode behaviors for the two different cables system was discussed by numerical method,and two kinds of multi-mode damping optimization methods are proposed then.Finally,the vibration mitigation experiment of a simple cable network with a grounding SMA strand cross-tie is carried out.The cross-tie’s tension,location,diameter and test temperature on frequencies and maximal damping ratio are discussed. |
