Damping in Cantilevered Traffic Signal Structures under Forced Vibration

The dynamic characteristics of a cantilevered traffic signal structure were determined experimentally and theoretically. The experimental procedures involved forced vibration of the structure by an eccentric-mass oscillator. Theoretical characteristics were determined using computer modeling. Several devices were developed to provide additional damping. The response spectra of the retrofitted structure were compared to the response spectrum of the non-retrofitted structure. Theoretical response curves were developed and compared to the experimental results. The most viable devices included a dual-strut system equipped with shock absorbers, and a tuned-mass impact damper. In the former, the damping was increased by an average factor of 6.3 in the in-plane direction, and 1.8 in the out-of-plane direction when considering the response at the box connection. In the latter, the most promising orientation yielded a 3.5 and 2.4 fold increase in damping in the in-plane and out-of-plane directions, respectively.