基于增量动力分析的隧洞结构抗震性能评估

Seismic Performance Assessment of Tunnel Structure Based on Incremental Dynamic Analysis

近年来随着地震灾害的频繁发生,强震区的地下结构屡屡遭受破坏。长大隧洞作为中国实施西部大开发战略的重要基础工程,其抗震安全问题尤为突出。通过引入增量动力分析(IDA),结合地震易损性分析方法,提出基于损伤系数指标的隧洞结构抗震性能评估方法。该方法以震后衬砌结构特征部位的损伤系数为性能参数,以地震峰值加速度为强度参数,并建议了适用于隧洞结构抗震安全评价的5级震害划分标准和4级抗震性能水平。针对某隧道工程实例,通过大量非线性动力时程计算,得到了各抗震性能水平下衬砌结构特征部位的地震易损性曲线,进而分析了不同抗震设防水准下衬砌结构发生破坏的概率。结果表明:在8度多遇地震作用下,衬砌结构基本无破坏;在8度设防地震作用下,拱腰处于基本完好状态的概率为87.6%,处于轻微破坏状态的概率为10.72%;在8度罕遇地震作用下,拱腰处于轻微破坏状态的概率为68.7%,处于中等破坏状态的概率为20.8%。在横向和竖向地震动输入下,衬砌结构特征部位的抗震性能由小到大依次为拱腰、拱肩、拱脚、顶拱和仰拱,拱腰、拱肩和拱脚为抗震设计的薄弱部位。该方法较好地考虑了地震动的随机性,可为隧洞结构抗震安全评价提供一种有效思路,研究成果也能为隧洞结构的抗震减震设计提供参考。

With the frequent occurrence of earthquake disasters in recent years, underground structures in strong earthquake areas have been repeatedly damaged. Long and large tunnel is an important fundamental project for the implementation of China’s western development strategy,and its seismic safety problem is particularly prominent. By introducing incremental dynamic analysis(IDA) and combining with seismic fragility analysis method, a seismic performance assessment method for tunnel structure based on damage coefficient index was proposed. In this method, the damage coefficient of the characteristic part of lining structure after earthquake was taken as the demand measure, and the peak ground acceleration of the earthquake was taken as the intensity measure. Then, the 5–level seismic damage classification standard and 4–level seismic performance level suitable for the seismic safety evaluation of tunnel structure were suggested. Taking a tunnel project as an example, the seismic fragility curves of the characteristic parts of lining structure under different seismic performance levels were obtained through a great deal of nonlinear dynamic time-history calculation. Furthermore, the failure probabilities of lining structure under different seismic fortification standards were analyzed. The results showed that the lining structure was nearly undamaged under 8–intensity frequent seismic load. The probabilities of haunch in nearly intact state and slight damage state were 87.6% and 10.72% under 8–intensity fortified seismic load, respectively. The probabilities of haunch in slight damage state and medium damage state were 68.7% and 20.8% under 8–intensity rare seismic load, respectively. The seismic performance of the haunch, spandrel, arch foot, top arch and bottom arch of lining structure increased in turn under horizontal and vertical seismic motion input. The haunch, spandrel and arch foot were the weak parts of seismic design of lining structure. The method can well consider the randomness of seismic motion, and provide an effective way for the seismic safety evaluation of tunnel structure. The research results can also provide references for seismic design of tunnel structure.