ارزیابی پاسخ لرزه ای پلهای بتنی مستقیم با سه روش کنترل غیر فعال: میراگر K شکل، میراگر جرمی تنظیم شونده و جداساز لاستیکی با هسته سربی

Abstract

In present research, the ability and advantages of K-Damper, LRB and TMD as passive control devices in reducing or balancing the seismic forces on substructures of bridges are investigated. Regarding to the variety of bridge damages occurred in the past earthquakes mostly as a result of underestimation of the seismic forces, passive control devices can be effectively used in designing or retrofitting of bridges which are located in high seismicity zones. Contemporary Seismic isolation systems for the bridge applications provide: (a) horizontal isolation from the effects of earthquake shaking and (b) an energy dissipation mechanism to reduce displacements. Throughout the years many kinds of seismic isolation mechanisms have been developed with two concepts: the introduction of negative stiffness elements and the incorporation of an additional mass. Combining the beneficial characteristics of both concepts, a novel passive vibration isolation and damping concept has been introduced as the K-damper.In this paper, evaluation of seismic response of the straight concrete bridges with three methods of passive control (K-damper, TMD and LRB) by adding them to a typical bridge was investigated. It was concluded that these passive control devices are very effective in reducing seismic forces and displacements of the typical bridge. By absorbing most of input energy of earthquake, these devices have the ability to protect the bridge substructure from the seismic damage. A comparison with a non-isolated bridge with similar characteristics confirms that LRB can decrease the pier base shear because of high flexibility and increase the main period of the structure. Further, K-damper based seismic absorption designs can provide lower displacement at the top of the piers. Therefore, by combining K-damper and LRB can obtain the best performance in reducing the top displacement of the piers and reducing the base shear.