Research And Application Of Base Isolation In Seismic Retrofit Of RC Frame Structure

Base isolation is a damping control technology whose application is relatively mature in the world at present. Due to the outstanding performance in earthquake, base isolation has been more and more applied in earthquake-resistance of engineering structures. In addition, it also has the advantage of better anti-seismic behaviors, shorter construction period and no need to strengthen superstructure, so base isolation has been more and more applied in seismic retrofit of frame structure. Thus research and application of base isolation in seismic retrofit of RC frame structure is of great importance. The specific work in this paper is as follows:(1) Based on the practical strengthening engineering of a gym, with the Bouc-Wen model of rubber bearing, the models of original structure and base-isolated structure were both built by using the finite element software. Through model analysis and time-history analysis under frequent and seldom earthquake, it was shown that rubber bearing could prolong structure’s natural vibration period, decrease maximal acceleration on top, story force and inter-story drift angle. It also turned out that hysteresis curve of rubber bearing was good and the isolation layer absorbed most of seismic energy. The comparison of model analysis and time-history analysis between original structure and base-isolated structure highlights the excellent anti-seismic behaviors of base solated structure.(2) The models of original structure and base-isolated structure were both analysed by using pushover analysis. First, five seismic performance levels were defined. Then under the pushover analysis described in the paper, we found that according to development of plastic hinge in columns and beams, base-isolated structure was basically intact while original structure was intensely destoryed under seldom earthquake. It proves that isolation and reinforcement measures can improve the seismic performance of members and structures under earthquake.(3) The effects of different types and different ways of isolation bearings arrangements on damping effect were investigated. The results shows that natural rubber bearings are better in controlling acceleration while lead rubbering bearings are better in controlling story drift and story shear force, so it is often helpful to use both of the two kinds of bearings in seismic retrofit. The results also show that different ways of isolation bearings arrangements has great effect in damping effect of isolated structure. In the engineering with large opening, it is better to install lead rubber bearings in outer peripheral areas of the structure while install natural rubberbearings in inter peripheral areas of the structure.(4) The effects of different isolator’s parameters on damping effect were investigated. The results show that the acceleration response and base shear foce response of base-isolated structure are influenced remarkably by equivalent horizontal stiffness, pre-yield stiffness and yield force. Both the maximal acceleration and the maximal base shear force of isolated structure show an increase trend with the increasing of equivalent horizontal stiffness, pre-yield stiffness and yield force. Thus it is important to select suitable isolator’s parameters in base-isolated design and isolated rein seismic retrofit design.