考虑场地地震动影响的场地分类方法研究

发布时间：2018-04-12 07:46

本文选题：场地分类 + Vs30　；参考：《中国地震局地球物理研究所》2015年硕士论文

【摘要】：场地条件影响在建设工程的抗震设计和抗震安全性评价中占有举足轻重的地位。不同的场地条件可引起地震动反应谱不同周期段值的改变,如果结构的自振频率与场地放大周期段相近,那么可能会引起工程结构更严重的破坏,而一般建设工程抗震设防中反映场地条件影响的一个重要手段就是进行场地分类,相应的场地分类就是将地震动作用下具有相似场地条件的场地进行分类。因此,明确而合理的场地分类方法和指标,可为工程场地设计地震动确定和工程结果抗震设防提供重要依据。国内外许多学者进行过场地分类方法的研究,目前以抗震设计规范为基础,主要涉及的一般场地分类方法有美国《ASCE-10》中采用等效剪切波速Vs30作为场地类别划分指标的方法和国内《建筑抗震设计规范》中采用表层20m范围内覆盖土层的等效剪切波速和覆盖土层厚度双指标的场地类别划分方法。近年来国内越来越多的研究者认为,我国应借鉴欧美等国的经验,考虑更厚的覆盖土层影响,以审视我们现行的20m深度考虑方法。但从经济性、实用性和实际需求等诸方面来全面考虑,其性价比如何,我们是否需要增加深度至30m?这是一个需要认真研究和详细调查分析的课题。所以本论文将针对这一课题进行相关研究。本文收集了全国18个地区的1130个场地钻孔资料,先对覆盖层厚度小于20m的场地建立了基于Vs30的外推模型,并针对每一个场地钻孔建立相应的场地土层反应计算模型,随后分别依据中国和美国场地分类标准对场地土层反应计算模型进行了场地类别划分；选取人工基岩加速度时程和强震动加速度时程作为输入地震动对所建立的场地模型进行一维土层反应分析,得到场地地表地震动的峰值加速度PGA、峰值加速度场地放大系数Ka,峰值速度场地放大系数Kv和加速度反应谱特征周期Tg等参数。比较分析场地地震动参数计算结果发现,从同一类场地对地震动的影响效应的一致性来看：美国的C类场地优于中国的Ⅱ类场地；中国的Ⅲ类场地场地效应的离散性较大,表现出一定的劣势；在软弱场地上,中国的Ⅳ类场地比美国的E类划分更细致；总体而言,考虑覆盖土层厚度的中国场地类别划分方法比未考虑覆盖土层厚度的美国场地类别划分方法显示了一定的优势性,所以在新的场地类别划分方法中不应该摒弃覆盖层厚度,但同时考虑美国场地类别划分计算的Vs30必然能更全面的反映场地信息,所以建议将等效剪切波速的计算深度增加到30m。根据本文场地地震动参数的比较分析研究结果及经济性需要提出按照覆盖土层厚度和30m最小值计算等效剪切波速的场地分类方法,并根据现行的场地划分规范进行了各场地类别界限的调整。同时针对中国的Ⅱ类和Ⅲ类场地的场地地震动参数离散性较大的问题,依据覆盖土层厚度和新调整的场地类别等效剪切波速界限值将Ⅱ类场地划分为Ⅱ1和Ⅱ 2类场地,将Ⅲ类场地中H50m且Vse≤170m/s的场地归类到Ⅳ类场地。
[Abstract]:Effect of site conditions play an important role in seismic design and seismic safety evaluation of construction project. Different site conditions can cause the spectrum of different ground motion response period value change, if the frequency of the structure and site amplification period are similar, so may cause more serious damage of engineering structures, and general construction engineering seismic fortification is an important means to reflect the effect of site conditions is the site classification, site classification is the corresponding seismic classification with similar site condition of site effect. Therefore, the method of site classification index and clear and reasonable, for engineering site seismic design and seismic engineering results provide an important basis for fortification. Many domestic and foreign scholars have conducted research on site classification method, the seismic design specifications as the basis, mainly related to the general field A classification method of site classification method using the equivalent shear wave velocity in the range of 20m surface soil cover using the method of equivalent shear wave velocity Vs30 in the United States as site classification indicators and domestic seismic design code of building > and < double cover thickness index. More and more researchers in China in recent years, China should learn from Europe and the United States and other countries experience, considering the effect of soil cover more thick, to examine our current 20m method. But the depth of thinking from the economic, practical and actual demand and other aspects to consider, how its cost, whether we need to add depth to 30m? This is a need of careful study and detailed investigation the subject. So this paper will aim at this topic related research. This paper collected 1130 ground drilling data in 18 areas of the country, the first covering layer thickness is less than 20m The site established extrapolation model based on Vs30, and for each site drilling are established. The corresponding calculation model of soil reaction, then according to Chinese and America site classification standard of soil reaction calculation model for site classification; artificial selection of base rock acceleration and strong motion acceleration as one-dimensional analysis the soil reaction model was established on the site seismic input from PGA peak acceleration of ground surface vibration, the peak acceleration of site amplification coefficient Ka, peak velocity and acceleration of site amplification coefficient Kv spectrum characteristic period Tg parameters. Comparative analysis of ground motion parameters in the calculation results, from the same site of consistency the effect of ground motion of the C site: the United States is better than that of Chinese class II site; discrete III site site effect of China Large, show some disadvantages; in the soft ground, the China IV site than in the United States E more detailed classification; overall, considering the Chinese site classification methods covering soil thickness of covering soil thickness than without considering the American site classification method shows a certain advantage, so in site classification the new method should not abandon the cover thickness, but at the same time considering the United States site classification for Vs30 must be able to reflect the site more comprehensive information, so that the calculation depth equivalent shear wave velocity increased to 30m. according to the comparative analysis of the ground motion parameters of the research results and economic need proposed site classification method to calculate the equivalent shear according to the wave velocity of soil thickness and the minimum value of 30m, and the site boundaries adjusted according to current standard. At the same time to divide the space needle Class II and III site ground motion parameters of Chinese larger discreteness, according to soil covering thickness and adjustment of the site class equivalent shear wave velocity limit value will be divided into 1 class II site II and II 2 sites, classified III site in H50m and Vse than 170m/s to IV site site.

【学位授予单位】：中国地震局地球物理研究所
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435

【参考文献】