SEMI-ACTIVE CAM-LEVER FRICTION DEVICE FOR VIBRATION CONTROL OF BUILDINGS SUBJECTED TO EARTHQUAKES

The implementation of damping devices in building structures increase their safety and serviceability during natural hazards like earthquakes and strong winds. Damping devices are categorized into passive, semi-active, and active systems according to their working principle. For instance, passive devices rely on physical mechanisms to dissipate energy, active devices use external power to modify the dissipative capabilities, and semi-active devices combine both principles to dissipate energy with the reliability of passive devices and the versatility to adapt like active systems using smaller magnitude of power consumption. Among semi-active devices, variable-friction dampers have received attention because they only require a variable clamping force to provide adaptability. Recently, a new semi-active friction damper was developed to apply a variable normal force using a cam-lever mechanism. The normal force applied with slipping bolts is controlled through a varying-radius cam attached to a lever, and a slider-crank mechanism that transforms the rotational movement of the first lever into a linear movement of an actuator. The proposed mechanism provides mechanical advantage to easily adjust the position of the levers and change the tension of the slipping bolts. The first prototypes of the proposed device provided insight into its capabilities as well as weaknesses that need to be improved to provide efficiency and reliability. Therefore, this project investigates the performance of a new prototype considering manufacturing materials, geometric configuration, and stiffness of components that improve the behavior of the device. The proposed device is evaluated experimentally at small-scale, using aluminum and additive manufacturing of components, and an Arduino microcontroller to change the positions of the levers. The test specimen is subjected to harmonic motions to characterize the device, and it is also subjected to earthquake motions through a Real-time Hybrid Simulation setup to evaluate the performance in a realistic structural control scenario. The results show that the device can have additional normal forces applied to the friction surface to increase the passive capabilities of the device if the actuation system malfunctions. Overall, this research encourages the implementation of modern technology in structural engineering to increase efficiency of systems, reduce costs, and add safety and reliability to civil infrastructure.