中文摘要：

针对目前国内既有公路桥梁扩建改造工程尚无现成抗震设计规范可参考的问题,以待扩建的高速公路典型桥梁为例进行抗震设防标准研究.根据不同扩建改造方案下桥梁的后续使用年限,按一致危险性原则,采用与现行规范所要求的设防标准相同的地震动超越概率,研究并建立抗震重要性系数与抗震设防地震动水平的关系,通过调整抗震重要性系数的方法计算抗震设防地震动水平.运用该方法对京沪高速公路拟扩建工程进行分析,根据扩建改造方案确定剩余服役期,计算得相应设防标准的超越概率及抗震重要性系数,结果表明,当剩余服役期较短时,采用较小的抗震重要性系数,即可保证桥梁工程的抗震安全性,进而获得良好的经济性.

英文摘要：

In view of the problem that currently there are no ready seismic design codes to ahide by for the domestic expanding construction of existing highway bridges,the typical expressway bridges to be expanded are taken as examples and the seismic fortification criteria for the expanded bridges are studied.The relationship between the seismic importance factors and the seismic fortification ground motion levels is studied and established,using the exceeding probability of the ground motion that is consistent with the seismic fortification criteria in the current codes in consideration of the remaining service years of the bridges to be expanded with different schemes and on the principle of consistent risk.The seismic fortification ground motion levels are calculated by the method of adjusting the seismic importance factors and the complete method described herewith is used to analyze the bridges to be expanded on Beijing-Shanghai Expressway.In accordance with the expanding schemes,the remaining service periods of the bridges are determined and the exceeding probability and the seismic importance factors of the corresponding seismic fortification criteria are calculated and obtained.The results demonstrate that when the remaining service period of a expanded bridge is short,the little seismic importance factors can be used,the seismic safety of the bridge can be guaranteed and better economy will be therefore achieved.