Friction Based Semi-Active Control of Cable-Stayed Bridges
Shehata E. ABDEL RAHEEM *, Uwe E. DORKA ** and Toshiro HAYASHIKAWA *** * ** ***
Dr.-Eng., JSPS fellow, Hokkaido University, Assist. Professor, Assiut University, Assiut 71516, Egypt.
Dr.-Eng., Professor, Steel & Composite Structures, Kassel University, Kurt-Wolters-Strasse 3, Kassel 34125, Germany.
Dr.-Eng., Professor, Graduate School of Engineering., Hokkaido University, Nishi 8 Kita 13 Kita-ku, Sapporo 060-8628, Japan.
With the rapid increase of bridge spans, research on controlling earthquake-induced vibration of long-span bridges has been a problem of great concern. The concept of varying the normal force in a frictional interface is investigated to enhance the energy dissipation from a vibrating structure and improve the seismic performance of bridge structures. A semi-active optimal control algorithm is formulated to determine the controllable clamping force of a variable friction device; this algorithm uses measurements of the absolute acceleration and device relative displacements for determining the control action to ensure that the algorithm would be implementable on a physical structure. The friction device UHYDE-fbr is designed and manufactured such that the normal force in the friction interface can be influenced with air pressure chamber, hence the normal force and friction damping can be controlled. The friction device is a controllable energy dissipation device that cannot add mechanical energy to the structural system; the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. The numerical results demonstrated that the performance of the presented control design is nearly the same as that of the active control system; and that the friction device can effectively be used to control seismically excited cable-stayed bridges with multiple-support excitations. Key words: Cable-stayed bridges, seismic design, friction device system, control algorithm, semi-active control
The control of long-span bridges represents a challenging and unique problem, with many complexities in modelling, control design and implementation1) ~ 4). Cable-stayed bridges exhibit complex behaviour in which the vertical, translational and torsional motions are often strongly coupled. Through implementation of an appropriate adaptive control law, semi-active elements are able to adapt to different vibration environments and/or system configurations5) ~ 7)
able to dynamically modify the response of a structure in order to increase its safety and reliability. However, the engineering community has not yet fully embraced this technology because of questions of cost effectiveness, reliability, power requirements5). An alternative approach is the semi-active control device system offering the reliability of passive devices, yet maintaining the versatility and adaptability of fully active systems, because semi-active control systems are inherently stable and require relatively much less power, the application of semi-active control system to civil engineering structures is very promising8) ~ 9). Control forces are developed based on feedback from sensors that measure the excitation and/or the response of the structure, the feedback of the response may be measured at locations remote from the active control system. With the Hysteretic Device Systems; Hydes10) being independent of the vertical load bearing system, a wide variety of link hysteresis loops are possible for
advantage over passive damping elements is their ability to utilize sensor information from other parts of the structure. Passive control systems are relatively simple and easy to be complemented, but the effectiveness of passive devices is limited due to their passive nature and the random nature of earthquake events. Active control...