This paper is focused on developing a Squeeze Mode MR damper with large control capacity for effective vibration
mitigation in infrastructures such as long span bridges and skyscrapers, etc. In order to maximize the magnetic field
required for control of MR fluid, this device is designed by separating electromagnet system from the main cylinder for
large capability of control force without changing its total length. This developed MR damper is tested to estimate its
maximum control capacity and dynamic range(defined as the ratio of the maximum force to the minimum force that MR
devices provide), inputting various strength magnet fields. These experimental results make it possible to estimate its
maximum control force by drawing a curve showing the relationship between generated forces and applied magnetic
fields. In order to verify its performance as a semi-active control device, its dynamic range is calculated. Through all
tests, the developed MR is proved to be an effective device for the response control of infrastructures.
Ubiquitous monitoring combining internet technologies and wireless communication is one of the most promising
technologies of infrastructure health monitoring against the natural of man-made hazards. In this paper, an integrated
framework of the ubiquitous monitoring is developed for real-time long term measurement in internet environment. This
framework develops a wireless sensor system based on Bluetooth technology and sends measured acceleration data to
the host computer through TCP/IP protocol. And it is also designed to respond to the request of web user on real time
basis. In order to verify this system, real time monitoring tests are carried out on a prototype self-anchored suspension
bridge. Also, wireless measurement system is analyzed to estimate its sensing capacity and evaluate its performance for
monitoring purpose. Based on the evaluation, this paper proposes the effective strategies for integrated framework in
order to detect structural deficiencies and to design an early warning system.
Magneto-rheological fluid is the fluid which is controllable with applied magnetic fields. This fluid is effective as a semiactive control device such as MR damper. In this paper, a new MR technology is developed with squeeze mode smart damper. And various dynamic tests are performed to identify the dynamic characteristics of this device. This squeeze mode smart damper can be used permanently, and can be freely allocated at the sub-region of large structures such as buildings and civil engineering infrastructures. Various dynamic tests are carried out to evaluate the performance of the squeeze mode smart damper in many loading conditions. Force-displacement and force-velocity hysteresis loops are also investigated for evaluation of its dynamic performance. In order to predict the dynamic performance of this device, two types of analytical models are compared with experimental results. A power model based on the damping and velocity, and a Bingham model are adopted in the viewpoint of practical usage. These results verify that the developed smart damper is effective in semi-active control of civil structures.
This paper attempts to validate the effectiveness of wireless sensor unit by field experiments on a self-anchored suspension bridge. This wireless sensor unit was developed at Konyang University's SIS lab in Korea for real-time dynamic response measurement of structures. This sensing unit called SWMAS(Smart Wireless MEMS-based Sensor System) consists of a sensor system module, a control and processing module, and a wireless modem module. In order to evaluate whether SWMAS would be applicable to structural monitoring system, experiments were performed to a full-scaled structure, which was a self-anchored suspension bridge, a wire-based monitoring system placed inside. In the field experiments, the data from the ambient vibrations of the bridge were acquired in real-time using SWMAS. All data acquired were compared with those of wire-based monitoring system. As a result, the comparison proved that SWMAS would be effectively applicable to smart monitoring system.
This paper experiments on each of two control algorithms which are adapted into a unified control algorithm, in order to decide which is better for semi-active control of civil structures using a squeeze mode smart damper. These algorithms are Lyapunov algorithm and a clipped optimal algorithm, both of which are superior in efficiency and reliability to any existing semi-active control algorithms. Such adaptation makes it easier to develop a control algorithm because it accommodates both continuous and discrete time signals at the same time, and to analyze the control characteristics in the case of broadly distributed natural frequency by securing enlarged stable regions. In order to prove its validity, we performed vibration control tests using a prototype steel plate girder bridge. Since the model is a reduced one, we also scaled EI Centro earthquake wave to the same scale as the reduced model bridge. Various performance indexes have been used to see which algorithm is most effective in control. Also, other experiments were performed to define the control characteristics which would enable us to see how all control conditions--displacement control, force control, and acceleration control--work with each control algorithm. Those experiments showed that each control algorithm works differently according to each different control condition. It is found that Lyapunov algorithm of the two is more effective for semi-active control in the unified control system. Therefore, it is necessary to design a control system according to structural conditions and circumstances.