Novel Resettable Stiffness Systems for Response Mitigation of Civil Infrastructure

Ohio University, Athens OH

Investigators

Abstract

Earthquakes have the potential to cause large-scale destruction of civil infrastructure often leading to significant economic losses or even the loss of human life. Therefore, it is vital to protect civil infrastructure during these events. Structural vibration control using damper provides a method for mitigating the damage to civil infrastructure during earthquakes by absorbing seismic energy from the structure. Damper with semi-active control has emerged as an attractive form of structural control due to its effectiveness, inherent stability, and reliability. This proposal plans to pursue research in resetting semi-active stiffness damper (RSASD) to control vibrations. The purpose of the proposed research is to develop innovative resettable stiffness systems that use minimum feedback control. The resulting devices, by minimizing feedback control, will have high reliability and robustness. The project involves assembly and small-scale testing of the devices to evaluate their energy dissipation characteristics. Annual Ohio University Middle School Science Fair will be used to demonstrate the devices to students to encourage them to pursue STEM education. The research results will also be incorporated in the courses to advocate innovation in engineering. The RSASD has several complexities associated with its operation. In particular, the feedback control system is necessary such that the valve is pulsed open and closed when the piston has reached its maximum displacement, that is, when there is a change in sign of the piston velocity. However, this means that any noise (interference) in the sensor signal, or any high frequency small amplitude structural vibrations, could also trigger the valve, thereby resetting the device at the wrong time. To accommodate this, a threshold on the position signal is used. The threshold ensures that a predetermined minimum displacement of the piston has occurred before resetting the device. Also, as a semi-active control technology, the RSASD is subject to reliability issues related to the feedback system. Failure of the sensor, microcontroller, or valve would lead to device malfunction and loss of energy dissipation to the structure. An innovative design with reduced feedback components will be investigated to develop a resetting stiffness system to provide damping to vibrating civil infrastructure. This new system, if successful, will make RSASD highly reliable and robust.