Experimental Study on The Mechanical Properties of Novel Viscous Mass Damper

ObjectiveThe inertial system has been shown to possess beneficial effects on building structures, such as extending their natural period. However, the development of the device itself remains relatively limited. This paper aims to design and develop a novel viscous mass damper (NVMD). The mechanical performance of the NVMD is evaluated through theoretical analysis and experimental validation. Based on the experimental results, numerical simulations are conducted to investigate the response control effectiveness of the NVMD during seismic events.MethodThis study presents a design methodology for a NVMD, whose theoretical model consists of a viscous damping element and an inerter element connected in parallel. The viscous damping element is responsible for energy dissipation, while the inerter element realizes inertia force generation through a high-speed rotating mass unit incorporated with a ball-screw system. Based on the physical relationship between the rotational inertia of the mass unit and the ball-screw mechanism, the axial force equation of the NVMD is derived, which serves as the foundation for mechanical parameter design. To comprehensively evaluate the mechanical performance of the NVMD under various loading conditions, dynamic tests were conducted under 24 different loading scenarios. These test conditions were designed to investigate the influence of loading amplitude and frequency on the damper's behavior. Specifically, the loading amplitude was set to four levels: 10, 20, 30, and 40 mm; while the loading frequency included six levels: 0.1, 0.3, 0.5, 0.7, 1.0, and 1.5 Hz. These combinations resulted in a total of 24 test conditions. To investigate the effect of friction generated by ball bearing friction on the mechanical properties of NVMD, a friction condition is set up. The acceleration and velocity of this operating condition need to be controlled within a quasi-static range to eliminate the effects of damping and inertia forces. Therefore, this working condition is loaded using a quasi-static triangular wave with a loading rate of 0.1 mm/s and a displacement amplitude of 40mm. To validate the theoretical model, dynamic tests under 24 different loading conditions were conducted to evaluate the hysteretic behavior and mechanical performance of the NVMD. In the investigation of seismic performance, the NVMD was applied to a frame structure and compared with a conventional viscous fluid damper (VFD) in numerical simulation. The comparison focused on their effectiveness in mitigating inter-storey drift and storey acceleration responses.Results and DiscussionsThis study experimentally investigated the adaptability and stability of the NVMD under various loading conditions. Numerical simulations further confirmed its feasibility and practicality as an efficient seismic mitigation damper.The experimental results of friction force conditions demonstrated that the hysteresis curve of the NVMD resembles that of a traditional friction damper, exhibiting a rectangular shape. The maximum friction force of the NVMD is 14.2 kN, while the minimum friction force is 15.2 kN. The average friction force is 14.6 kN. The experimental results demonstrated that the derived axial force formula for the NVMD can accurately predict its hysteretic behavior. The maximum error between the theoretical and experimental forces was 20.99%, with an average error of only 9.83%. In terms of force magnitude, the maximum error was 42.5 kN, while the average error was as low as 20.97 kN. These results validate the effectiveness of the proposed formula and provide a reliable theoretical basis for the design of the NVMD. Parametric analysis revealed that the energy dissipation capacity of the NVMD is highly sensitive to loading frequency under large displacement amplitudes. Specifically, under low-frequency loading conditions, the energy dissipation area within a single hysteresis loop increases significantly with increasing frequency, indicating superior energy dissipating performance. In terms of seismic performance of the frame structure, the NVMD exhibited distinct advantages. Although the inter-storey drift control performance of the NVMD was comparable to that of the conventional VFD, with a maximum difference of only 2.59% under a peak ground acceleration (<italic>P</italic>_GA) of 0.22g, it showed significantly better performance in acceleration control. Under the same <italic>P</italic>_GA condition, the NVMD achieved a storey acceleration reduction ranging from 37.00% to 51.32%, which represents an improvement of 11.36% over the VFD. Under a higher <italic>P</italic>_GA of 0.40<italic>g</italic>, the NVMD achieved acceleration reductions between 25.28% and 48.64%, showing an enhancement of 36.05% compared to the VFD. These findings indicate that, with only a marginal improvement (0.97%) in inter-story drift control, the NVMD can achieve an additional 36.05% reduction in storey acceleration response. Moreover, its superior seismic mitigation capability becomes even more pronounced under extreme earthquake conditions.ConclusionsThis study designed and developed a NVMD, and comprehensively evaluated its performance in energy dissipation and seismic response control through theoretical modeling, dynamic testing, and parametric analysis. The experimental results indicate that the proposed axial force formula for the NVMD can effectively predict its hysteretic behavior, providing a scientific basis for its design. The device demonstrates significant energy dissipation capabilities under various loading frequencies and displacement amplitudes. Notably, the NVMD exhibits distinct advantages in enhancing structural seismic performance. Although its effectiveness in controlling inter-storey drift is comparable to that of the conventional VFD, it shows superior performance in acceleration control. Particularly during rare and intense earthquakes, the NVMD can more effectively reduce peak storey accelerations, thereby improving the comfort and safety of buildings during seismic events.