Active and passive hybrid vibration control and analysis of dike pipeline

An active passive hybrid control system (MRTMD) was proposed to combine a magnetorheological damper (MRD) and a tuned mass damper (TMD). The vibration of water supply and drainage pipelines was controlled when passing through embankments caused by the operation of pumping station units. Linear quadratic regulator (LQR) based optimal control algorithm was utilized to optimize the parameters of the active passive hybrid vibration control system, in order to minimize the acceleration of the structure. Magnetorheological damper damping was stable enough to change the damping frequency in the new system, compared with the traditional single-tuned mass damper. Firstly, a simulation signal was constructed to simulate the load excitation of pump station units during operation, the vibration response of pump station pipeline was also used to compare with a single TMD and MRD control, in order to verify the applicability and effectiveness of the MRTMD for pump station pipeline vibration reduction. Secondly, shock waves were used as excitation to simulate and analyze the control effect of pipeline dynamic response, in response to the phenomenon of water hammer during opening and closing of the unit or the abnormal vibration under extreme working conditions. The damping force and displacement hysteresis curve were used to explore the robustness and vibration reduction of the output resistance force; Finally, MRTMD was applied to the water supply and drainage pipeline project in the Beijiang Dam in Guangdong Province. The simplified two-degree-of-freedom mass, stiffness, and damping matrices of the pipeline were solved using load inversion and then established the pipeline vibration dynamics equation. Taking the vibration reduction efficiency as the evaluation index, the vibration reduction efficiency of the new system on the water supply and drainage pipeline structure passing through the embankment was analyzed from the time domain perspective. The effective vibration reduction frequency range and energy reduction efficiency of each main frequency of MRTMD were also analyzed from the frequency domain perspective. The results show that the damping force provided by MRTMD shared a wide range, stable output, and strong energy dissipation. Better control was achieved in the acceleration response of pipeline structure, when passing through the embankment, with a damping efficiency of 37.56%-38.07%. There was a slightly better control in the displacement response of the structure, compared with the acceleration response, with a damping efficiency of 40.23%-41.38%, and a damping effect of 33.9% at the pipeline passing through the embankment. The vibration reduction was superior to single TMD and MRD control; There was the weakening effect of MRTMD on the main frequency energy of various vibration sources during operation in a frequency domain. Among them, the mechanical vibration energy caused by the rotation of the main shaft (such as rotation frequency and doubling frequency) was reduced to 27.46% and 75.88%, respectively, while the vibration energy was significantly reduced to 36.46% for medium to low frequency vibration that caused by water flow impact and axial vortices formed in the impeller.