【作者】 邹颖娴；

【导师】 王社良；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2006， 硕士

【摘要】 砂砾石垫层是换填垫层法的一种,由于其比较经济,因此在实际工程中的应用比较广泛。这种垫层法是用碎石、卵石、角砾、圆砾、砾砂、粗砂、中砂或石屑等坚硬、较粗粒径的回填材料,经合理级配并夯压密实后形成持力垫层,其主要目的是为了提高浅层软弱地基或不均匀地基的承载力。砂砾石垫层具有压实性能好、透水性强、填筑密度大、抗剪强度高、沉陷变形小、承载力高等工程特性,应用前景较好。 常规的建筑结构抗震设计方法在进行上部结构的内力分析时,一般都将基础视为绝对刚性,建筑物的动力特性完全取决于上部结构,其地基及垫层对上部结构地震反应的影响可忽略不计,这与结构的实际工作状况有较大差异。因此,为了考虑砂砾石垫层及地基对上部结构抗震性能的影响,本文采用地基、砂砾石垫层、基础、上部结构共同工作的整体计算模型,主要研究其共同工作性能及砂砾石垫层的隔震效果。 基础隔震是一项发展较快的地震防护技术,其主要原理是在建筑物和基础之间设置一层具有足够可靠性的隔震层,以降低结构振动的基本频率,延长其基本周期,从而使其避开地震动的主要能量频带,“隔离”地震能量向上部结构的传递。本文以基础隔震技术的基本概念为基础,采用共同工作的整体计算模型来进行基础下铺设砂砾石垫层对上部结构地震反应影响的研究,以期为这类结构的抗震设计提供依据。 论文首先介绍了砂砾石垫层的基本概念和共同作用的研究现状,接着在现有基础隔震理论的基础上,分析了砂砾石垫层的力学性能和隔震原理,然后利用大型有限元分析软件ANSYS建立了考虑共同作用和不考虑共同作用2种工况下的有限元计算模型,并对其输入地震波,通过对2个计算模型的地震反应时程分析,研究了考虑砂砾石垫层及共同作用体系的地震响应特点,分析了其隔震机理和隔震效果。 研究结果表明,考虑地基土、砂砾石垫层、上部结构共同作用时,结构的基本频率明显减小,相应的基本周期明显延长;并且在强烈地震的作用下,整体结构的一部分变形将由下卧层土体和砂砾石垫层共同承担,上部结构则表现出一定程度的刚体平动;结构各层的加速度反应均明显减小,但底层的层间位移有所增大,其余各层的层间位移均明显减小,这说明铺设砂砾石垫层具有较明显的隔震作用,考虑其作用后上部结构各层的地震反应均有所降低,结构的抗震性能有所提高。更多还原

【Abstract】 Sand gravel cushion is a kind of ground cushion treatment, it is widely applied because of its low cost. It works by choosing appropriate gravel, scree, talus decries, coarse sand, medium sand, then ram them to be closely knitted. The sand gravel cushion can increase the bearing capacity of weak groundwork. It has widely use because of its good compact character, water permeability, high shearing strength and low deformation.The basement is treated as rigid in common seismic design, the dynamic character of the whole structure is decided by only the superstructure, and the infection of basement and foundation soil is neglected, in this way, the structure be calculated is quite different from its actual performance. So a finite calculating model considers the combined activate of basement soil, sand gravel cushion, basement and superstructure was taken in this paper, in order to study the infection on the anti-seismic ability of superstructure that brought on by sand gravel cushion.Basic isolation is the vibration isolation technique which has the most developed theory, and the most extensive use. Basic isolation mainly works by setting a reliable isolating zone between the basement and the structure, in order to reduce the fundamental frequency and prolong the fundamental period to keep the structure away from the main frequency band of the earthquake which carries the most energy, and in this way, the earthquake energy that transfers into the superstructure can be reduced. At the same time, the basic isolation systems use some dissipating equipments to reduce structure displacement, in this way, all the structure dynamic response can be reduced, and the structure and the establishment in it can be safe when earthquake occurred.In this paper, the definition of sand gravel underlayer and the researching actuality of combined activate are introduced at the very first. Then, the isolating mechanism of combined activate of sand gravel underlayer with foundation soil and superstructure is analyzed based on the basic isolation theory. Then, set up 2 finite element models using the numericalanalysis program ANSYS, one takes the combined activate into consideration, and the other not. At last, analyze the different time-history dynamic response of 2 model2, summarize the characteristics of the seismic response for combined activate system, and analyze the isolating effect of the combined activate system.The results shows that the fundamental frequency of the model which takes the combined activate into consideration reduced evidently, and the fundamental period prolonged evidently. The structural displacement of this model is partly carried by the underlayer and the foundation soil, so most stories’ deformation of superstructure are evidently reduced, but the deformation at the bottom is magnified. The acceleration response was reduced in all the floors. So we get the result that, when considering the combined activate of sand gravel underlayer with foundation soil and superstructure, the seismic response of most floors can be evidently reduced.更多还原