Strand Damper

The flat bar impact damper showed that the impact concept could provide increased damping. However, the low strength combined with the low stiffness necessary to provide a damper with the same natural frequency as the pole resulted in yielding at the support. An increase in yield strength was needed without an associated increase in stiffness. A new impact device was designed that utilizes a ½ in (13 mm) diameter high-strength 270 ksi (1860 MPa) seven-wire strand (ASTM A416) as the support for the weights. The span of the impact damper could be raised or lowered to control the damper’s natural period. The weights were wrapped with neoprene to reduce the noise produced at impact.

Damping Results

In-Plane Response

Non-retrofitted Pole Non-retrofitted Pole

Out-of-Plane Response

Retrofitted Pole Retrofitted Pole