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通过对2011年新西兰发生的6.3级地震中获取的硬土场地、软土场地和液化场地强震记录实测资料进行分析,研究包括3种类型场地的地震动特征及其相互关系。分析的强震记录为震中距小于50 km,且峰值大于0.05g的23个场地上的加速度记录,其中含3个硬场地、11个软场地和9个液化场地。3种类型场地上的放大系数谱对比分析表明,硬土场地、软土场地和液化场地上的地震动特征具有明显区别,三者层次清晰,差别显著,从地震动表现上液化场地已构成一个与常规场地并列的独立单元;液化场地减少地震动高频分量但同时对低频分量显著放大,与非液化场地相比,液化场地可使其上短周期结构反应减小一半,但同时可使其上长周期结构反应放大2.5~5.0倍;土层的液化对此次地震中克莱斯特彻奇市中心CTV大楼的破坏应有很大影响,大楼自振周期约为0.7 s,地震中土层液化使场地加速度反应谱卓越周期由0.1~0.3 s增到0.5~1.0 s,与大楼的自振周期趋于吻合,加重了大楼震害。以此为鉴,按现有规范中地震动的设计方法,如遇液化场地将对长周期结构给出明显危险的结果,因此从振动角度今后进行结构抗震设计时,可液化场地上的地震动应给予特殊考虑。
By analyzing the recorded data of strong earthquakes collected from the 6.3 earthquakes occurred in New Zealand in 2011, the ground motion characteristics of the three types of sites and their correlations are studied. The recorded strong earthquakes recorded acceleration records on 23 sites with epicentral distances less than 50 km and peak values greater than 0.05 g, including 3 hard sites, 11 soft sites and 9 liquefaction sites. The comparison of amplification coefficient spectra of the three types of sites shows that there is a clear difference between the ground motion characteristics of the soft soil site and the liquefied site, the three levels are clear and the difference is significant. From the seismic performance on the liquefaction site has formed a Liquefaction sites reduce high-frequency components of ground motion while significantly amplifying low-frequency components. Compared with non-liquefied sites, liquefaction sites can reduce their short-period structural response by half compared to non-liquefied sites, The long-period structural response is amplified by 2.5-5.0 times. The liquefaction of the soil layer should have a great influence on the damage of the CTV building in downtown Christchurch in this earthquake. The natural period of the building is about 0.7 s, The liquefaction of the liquefaction layer accelerated the remarkable period of the acceleration response spectrum of the site from 0.1-0.3 s to 0.5-1.0 s, which agrees with the natural vibration period of the building, which aggravated the seismic damage of the building. Taking this as a reference, according to the design method of ground motion in the existing code, if the liquefied site will give a noticeable danger to the long-period structure, the seismic motion on liquefiable ground Special consideration should be given.