A Passive Adaptive Suspended Mass Pendulum to Compensate Detuning Due to Large Swing Angle

The suspended mass pendulum (SMP) conventionally used is a type of frequency sensitive vibration control device. It is vulnerable to detuning due to large amplitude oscillations, which can lead to a significant loss in vibration control performance. Although active or semi-active control systems can solve the problem of frequency detuning, the reliability and stability of the sensors and actuators in the control system are difficult to guarantee for large-scale civil structures. To overcome this issue, this study proposes a passive adaptive suspended mass pendulum (PASMP) that uses a curved support. First, the mathematical equations describing the curved support are derived to show that it can keep the frequency of the pendulum constant at large swing angles. Then the kinematic equations of a single-degree-of-freedom (SDOF) structure installed with the PASMP are established. A parametric analysis is conducted to verify how the parameters of the control system, including the excitation period, pendulum length and mass ratio, affect the dynamic responses of the main structure. Furthermore, to verify the effectiveness of the PASMP and the validity of the theoretical analysis, a two-story frame structure is chosen as the model structure in shaking table tests. Also, the proposed PASMP is applied to a transmission tower to numerically verify its effectiveness of vibration suppression under different seismic excitations. The numerical and experimental results demonstrate that the PASMP can more effectively suppress the vibration of structures than the conventionally used SMP.