Damping of Cable with HDR Damper Accounting for Restraint Boundary Conditions

Conventional designs for added damping in stay cables with a High Damping Rubber (HDR) damper are commonly carried out assuming perfect boundary conditions at the cable ends or a smooth transition between the damper and cable. This paper proposes an asymptotic formulation for the attainable damping in stay cables with an externally installed HDR damper that accounts for uncertain boundaries at the cable ends, which includes hinged, fixed, and rotational restraint ends. The results indicate that by adjusting supports at the cable ends with finite rotational restraint stiffness, the damper works more effectively. In addition, a reduction factor (R-rd) of the achievable damping caused by rotational restraint at an HDR damper location will be proposed and investigated for a clamped-clamped cable. In the design of an HDR damper with a rotational restraint between the damper and cable, the damping ratio is reidentified by multiplying the designed damping of a conventional case by the reduction factor (R-rd). (C) 2020 American Society of Civil Engineers.