Study On Seismic Semi-active Control For Bridges

The bridge anti-earthquake and seismic mitigation is always an important content in earthquake engineering. In this thesis, the calculation and analysis on semi-active control of seismic response for bridge are performed systemically. Bridge calculating models are established with beam bridges (rigid-continuous bridge, continuous beam bridge, curved continuous rigid bridge) and cable-stayed bridge which are applied widely in bridge engineering. With three types of semi-active control dampers (viscous damper, magnetorheological damper and piezoelectric friction damper), on the clue of two basic problems (semi-active algorithm and damper position), three influencing factors (traveling wave effect, pile-soil interaction and time delay) and one engineering application (curved bridge), the serial problems are discussed on semi-active control of seismic response for bridge. The main contents and achievements are as following:(1) Comparing and analysis of semi-active control algorithms. The semi-active algorithms can be divided into "switch type" algorithms and "continuous type" algorithms. The optimal bang-bang control algorithm and maximal switch control algorithm are best in vibration-suppressed effectiveness for most seismic responses of bridge. Limited sliding control algorithm can follow up active control well. Semi-active control can make most seismic responses of bridge less, but make some other seismic responses of bridge larger. Semi-active control algorithms can make some seismic responses of bridge nodes neighboring the dampers to produce acute magnifying effect. The continuous type semi-control algorithms can mitigate the "needlepoint" phenomenon well because they operate the damping force more gently, and their acceleration-magnified effect are more mitigatory than that of switch type algorithms. There is no acceleration-magnified effect in active control.(2) Simple and practical approach about confirming positions of dampers in bridge. The position optimizing of semi-active dampers relates to many factors including optimizing goal, damper type, semi-active control algorithm, bridge structure type, etc. To get the accurate positions of semi-active dampers is a complicated problem. The approach of confirming positions of dampers according as value of energy consumed by actuators in active control is simple and practical, and is applied well in the "discontinuous type" structure like bridges with link components including bearing and extensiongap.(3) Analysis of traveling wave influence on seismic mitigation control for long span rigid-continuous bridge. Seismic traveling wave effect can severely influence the seismic responses of un-control, semi-active control and active control of long span rigid-continuous bridge in lognitudinal and transverse direction. It can bring adverse influence on the pier and beam of bridge, and not on the beam only. Traveling wave effect reduces vibration-suppressed effectiveness of semi-active control and active control systems that are designed with seismic uniform input. When parameters of semi-active control and active control systems for long span rigid-continuous bridge are designed, traveling wave effect should be considered.(4) Analysis of seismic mitigation control for long span floating cable-stayed bridge under traveling wave input. The ground motion input with different frequency spectrum components can remarkably...