Performance of Pendulum Tuned Mass Dampers in Reducing the Responses of Flexible Structures

The primary objective of this paper is to study the dynamic responses of a flexible multiple degree-of-freedom structure coupled with the three-dimensional motions of a nonlinear pendulum tuned mass damper (PTMD). The three-dimensional motions consist of both planar and spherical motions of the PTMD. The optimal damper parameters obtained by using the three-dimensional model are compared with those predicted by models in which PTMD motion is linearized to the planar direction. The effect of and sensitivity to frequency and auxiliary damping detuning are considered for various levels of primary to auxiliary mass ratios. The performance of the PTMD is evaluated by using a finite element representation of an actual tower structure equipped with a PTMD, together with the responses obtained by using the high frequency base balance method from a boundary layer wind tunnel. The results are compared for linearized and three-dimensional PTMDs and the effect of directional coupling introduced by the nonlinear three-dimensional PTMD on the response estimates is studied by using the numerical model. Finally, a procedure is presented for conducting a condition assessment of existing PTMDs.