Seismic performance of a continuous bridge with winding rope device activated by a fluid viscous damper

The seismic requirements of piers with fixed bearings (the fixed pier) for continuous girder bridges are relatively high, while the potential seismic capabilities of piers with sliding bearings (the sliding piers) are not fully utilized. To solve this contradiction, a new type of winding rope shock absorption device activated by a fluid viscous damper (WRD-D) was proposed. The WRD-D was installed on the top of the sliding piers, and the both ends of a fluid viscous damper were connected to the superstructure by winding ropes. During an earthquake, the damping force rises with the increase of relative speed between the sliding piers and the superstructure, activating the WRD-D and producing large frictional resistance, subsequently causing the sliding piers and the fixed pier to bear the seismic load cooperatively. In this study, the working mechanism of the WRD-D was researched. The shaking table test of a scaled continuous girder bridge model employing the WRD-D was conducted. The test results reveal that the WRD-D can effectively reduce the seismic requirements of the fixed pier and the superstructure displacements.

Monitoring of Liquid Viscosity for Viscous Dampers through a Wireless Impedance Measurement System

Viscous dampers are a type of seismic damping equipment widely used in high-rise buildings and bridges. However, the viscosity of the damping fluid inside the viscous damper will change over time during its use, which significantly reduces the seismic performance of the viscous damper. Hence, it is necessary to monitor the viscosity of the fluid inside the damper over its service life. In this paper, a damping fluid viscosity monitoring method based on wireless impedance measurement technology is proposed. A piezoelectric sensor is installed in a damper cylinder specimen, and the viscosity of the damping fluid is determined by measuring the piezoelectric impedance value of the sensor. In this study, 10 samples of damping fluids with different viscosities are tested. In order to quantitatively correlate damping fluid viscosity and electrical impedance, a viscosity index (VI) based on the root mean square deviation (RMSD) is proposed. The experimental results show that the variation of the real part in the impedance signal can qualitatively determine the damping fluid viscosity while the proposed VI can effectively and quantitatively identify the damping fluid viscosity.

Nonlinear Characteristics of Three-parameter Fluid Viscous Damper with Considering of Principal Stiffness and Hydraulic Stiffness

The three-parameter fluid viscous damper is used to isolate micro-vibration produced by control torque gyro (CMG) in satellite. In this paper, the damper is simplified by a single tube fluid viscous damper and two springs connected to the damping piston. With consideration of the principal stiffness of the bellows and the contraction and expansion effect of the damping orifice, the approximate analytical nonlinear model of the damper is established and verified by the computation fluid mechanics (CFD) method. Based on this analytical model, the displacement response of the damper and correction coefficient of hydraulic resistance are analyzed, the nonlinear characteristics in the frequency domain are also revealed. Furthermore, the energy consumptions of the nonlinear model and linear model are researched. The results show that the damper has an obvious amplitude at the first resonance peak, but not obvious at the second resonance peak. The vibration amplitude of the damping piston is only um level in the high-frequency domain. The correction coefficient of the hydraulic resistance at the resonance peak is much higher than other frequencies, which causes a significant nonlinear behavior. In addition, the energy consumption of the nonlinear model is larger than that of the linear model at the resonance peak, and the larger the resonance peak, the more obvious the phenomenon is. This means that the nonlinear damping can be used to further improve the suppression of the resonance peak of the three-parameter fluid viscous damper.