Study on self-adjustable variable pendulum tuned mass damper

Pendulum tuned mass damper (PTMD) is usually used to control the horizontal vibration of a tall building. However, traditional PTMD is highly sensitive to frequency deviation and difficult to adjust its frequency. In order to improve this problem of traditional PTMD and protect a tall building more effectively, a novel PTMD, called self-adjustable variable pendulum tuned mass damper (SAVP-TMD), is proposed in this paper. On the basis of the acceleration ratio between TMD and primary structure, the SAVP-TMD can retune itself by varying the length of the pendulum according to the improved acceleration ratio-based adjustment algorithm. PTMD and primary structural accelerations are obtained from two accelerometers respectively, and the acceleration ratio is calculated in a microcontroller, then, the stepper motor will adjust the pendulum under the guidance of the microcontroller under a specific harmonic excitation. The improved acceleration ratio-based adjustment algorithm is proposed and compared to solve the nonconvergent retuning problem. The SAVP-TMD can be regarded as a passive damper including a frequency adjustment device. A single-degree-of-freedom structure model is used to verify the effectiveness of SAVP-TMD through both experimental study and numerical simulation. In order to further verify the effect of SAVP-TMD in the MDOF structure, a five-storey structure coupled with an SAVP-TMD is proposed as a case study. The results of experiment, simulation, and case study all show that SAVP-TMD can retune itself to the primary structural dominant frequency robustly, and the retuned PTMD has a better vibration control effect than the mistuned one.