The Research On The Effects Of Viscoelastic Dampers To Steel Truss’s Vibration Fatigue Behavior

After a point or several points of a set of material sustained disturbing stress or strain and experienced enough cycles, some parts of the set of material cracked even broke up. And development of the permanent partial change is called fatigue. The broken of steel structure is not only limited in the unstable failure which is caused by great load, but also include the fatigue failure. Many steel structures will occur fatigue failure under the cyclic load such as wind load, mechanical cyclic load, etc. The fatigue failure is often difficult to be detected and prevented. Thus the fatigue failure is destructive and has the confidentiality. Therefore the structures’ fatigue resistant ability is one of the key characters of structures’ reliability and safety.On the other hand, the structures’ fatigue life has close relations with the strain and stress level of each component of structures. To a same structure, the greater strain or stress is, the lower fatigue life will be. The viscoelastic dampers, as a mature technology, have been well applied to the structure vibration control, which can reduce the structure components’ strain and stress effectively. Since the structures’ fatigue life is depended on the stress and strain level of structure components, if viscoelastic dampers can reduce the stress and strain level of structures, it much can also have some effects on structures’ fatigue behavior.This thesis begins with the introduction of fatigue theory. In the chapter one, the definition of fatigue, the mechanism of fatigue phenomenon, the development of fatigue theory, etc, were introduced. In the chapter two, the structure of viscoelastic dampers and the computational model of the viscoelastic dampers are introduced. In the chapter three, the method of calculating the fatigue life and the method of calculating the vibration fatigue life were discussed. In chapter four, the equivalent damper coefficient and equivalent stiffness coefficient were deduced. In the chapter five and six, the effect of viscoelastic dampers to structures’ vibration fatigue was illustrated by the engineering projectAccording to the compare, it was believed that viscoelastic dampers can extend the structure’s fatigue life efficiently. With the increase of the damping coefficient, the structure’s fatigue life experienced a process that it first increases then decreases. Therefore structures’ fatigue resistant ability can be optimized through justified choice of the damping coefficients.