Damping Characteristics of Composite Girder

An experimental laboratory program was conducted to determine the damping characteristics of a composite girder at different strain levels and the effect of structural deterioration due to cyclic loading on these characteristics. The cyclic loading was imposed by means of a moving-mass closed-loop electrohydraulic actuator system. Five different methods were employed in the investigation to evaluate the equivalent linear viscous damping of the composite girder. The results show that strain level and structural deterioration have a considerable effect on the damping ratio. Initially, the damping ratio increased as the strain level increased. However, after the composite girder had incurred some structural deterioration, the damping ratio decreased as the strain level increased. All five of the different methods used to determine the damping ratio yield approximately the same value for the damping ratio and predict the same trends with regard to the strain level.