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土动力参数对土层动力反应的影响 总被引：19，自引：3，他引：19
本文通过关便指出了不同的土动力特性经验关系对土层地震反应的分析结果将产生不同的影响，特别是对大震作用下的土层反应，这一计算结果可作为有关部门制定相关规范的参考。 相似文献
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对利用一维波动理论计算土层地震反应时，将基岩假为具有自由边界的半无限空间，输入地震记录，计算传递函数，进而计算土层的表震反应这一方法步骤的合理性进行了讨论。理论推演表明，从基岩面输入地震记录和计算传递函数时，应当考虑基岩和上覆土层的相互作用影响。 相似文献
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通过梳理轨道交通地下结构抗震设计流程,明确抗震设计方法选择的原则和依据。在阐明反应加速度法基本原理基础上,引出土层地震反应分析的一维等效线性化法,并对影响土层地震反应计算结果关键参数进行讨论。针对一维土层地震反应得到的加速度时程提出合理拟合抛物线型二阶基线方程,可以消除加速度时程长周期随机分量引起的漂移问题,经自然积分可以得到消除基线漂移的位移时程;同时阐明数值分析软件Origin Pro有效解决积分得到位移时程的基线漂移问题并得到合理位移分布的途径和方法。以北京地铁3号线体育中心站为例,详细说明反应加速度法相关各个技术环节实现的方法和结果,并指出反应加速度法或位移法所依据的土层地震反应分析和位移时程的确定具有较强专业性,应做专项咨询分析工作;只有一维土层地震反应分析获得的加速度反应谱及时程客观合理,有限元计算所需相应地震动水平的等效剪切模量才可信;积分得到的位移时程需要有效消除基线漂移影响。只有上述相关结果真实客观可信,有限元计算结果才能模拟真实的土层-地下结构地震反应。 相似文献
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美国阿拉斯加安克雷奇德兰尼公园的土层地震反应观测台阵建有6个井下观测点和1个地表观测点, 每个观测点设置一个三分量加速度传感器, 该台阵建成后记录了多次地震事件. 本文通过反卷积地震干涉法对这些地震记录进行土层反应分析, 根据该分析结果提取土层结构的等效剪切波速和阻尼比. 所有层位的地震记录对地表记录的反卷积波形均反映出在土层中传播的上、 下行波, 其上行与下行至每一层的时间差别明显. 根据每一层的到时差, 确定土层中的等效剪切波速和分层等效剪切波速, 该结果与现场土层等效剪切波速测试结果吻合较好; 根据等效剪切波速计算出的土层卓越频率, 其一致性亦较好; 根据上、 下行波的峰值分析确定该场地土层的等效阻尼比, 也与软土的阻尼比经验值相当. 这些参数为后续的土层反应模拟和土结相互作用研究奠定了良好的数据基础. 结果表明, 反卷积干涉法能够用于土层反应分析和土层地震反应特性的提取. 相似文献
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首先基于地震作用下地下结构的变形受周围地基土变形控制这一相互作用特征,在反应位移法的基础上讨论两种简化分析方法:一种是将土层变形施加在模型边界模拟地震作用;另一种是将土层加速度施加到整个模型上模拟地震作用。这两种简化分析方法都避免了反应位移法中弹簧刚度的取值问题,提高了计算效率。其次分析不同地震动强度、不同侧边距的计算结果,并用动力时程分析的计算结果校核,分析两种简化计算方法的精度。结果表明:随着地震动强度的增加两种简化分析方法的计算结果都令人满意,使用强制反应位移法时建议侧边距取两倍结构宽度,使用反应加速度法时建议侧边距取三倍以上结构宽度。 相似文献
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砂土液化对设计反应谱和场地分类的影响 总被引：5，自引：0，他引：5
本文采用有效应力原理分析了液化土层对设计反应谱的影响，分析中考虑了砂层的厚度、埋深和输入地震动等因素。选择Ⅱ类场地，将其标准反应谱合成的三条地震加速度时程在考虑土层非液化下反演到基岩，再正演计算存在液化层时的地面运动时程和反应谱。分析结果表明，从特征周期的变化来看，液化土层使Ⅱ类场地易变为Ⅳ类场地，对地震影响系数的作用则不是很大，但频谱上0．8s是一个分界线，液化土层对分界线以下的高频分量有一定减震效果，对分界线以上的低频分量有显著的放大效应。 相似文献
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合理有效地模拟桩-土-结构动力相互作用是软土地基条件下核岛厂房结构抗震适应性分析及地基处理的关键环节。以某拟建核岛厂房实际工程为研究背景,结合SuperFLUSH软件平台,以Goodman单元模拟桩与桩周土间的接触效应,采用等价线性法描述近场软土地基非线性特性,并在模型底部和侧面引入黏性边界模拟半无限地基辐射阻尼效应,从而建立土质地基条件下桩-土-核岛结构相互作用分析模型。进而,通过对原状地基和嵌岩桩处理地基条件下核岛厂房的楼层反应谱、结构节点相对位移（绝对值）的对比分析,探讨考虑桩-土间接触效应的嵌岩桩基对核岛厂房结构的影响规律。研究成果可为实际工程中类似土质地基条件下核岛厂房结构的地基处理提供参考。 相似文献
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Naohiro Nakamura 《地震工程与结构动力学》2006,35(2):217-231
In order to perform time history earthquake response analyses with consideration to both the dynamic soil–structure interaction and the non‐linear behaviour of the structure, it is important to transform the soil impedance in the frequency domain to the impulse response in the time domain. In this paper, a new transform method with high practicality is proposed. First, the formulation of the proposed transform method is described. Next, the validity of the method is examined using an example problem whose impulse response is analytically obtained. Then, the impedance of the rigid foundation on 2‐layered soil is transformed to the time domain, and the characteristics of the impulse response are investigated. Finally, time history earthquake response analyses of a structure on the soil using the obtained impulse response are carried out. The validity and the efficiency of the proposed method are confirmed through these investigations. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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This paper presents development of a special finite difference method for the nonlinear dynamic response analysis of semi-infinite foundation soil. Semi-infinite domain is mapped into the finite domain using special mapping. For the region of engineering interest, mapping is isometrical, and for far field, shrink mapping which transforms an infinite interval into a finite interval is adopted. Using linear and nonlinear constitutive models, the responses of semi-infinite foundation soil are computed using a proposed method with a small mesh model and an extensive mesh model. Surface loadings or incident earthquake waves are applied to the models in the computations. Good agreements were obtained among the theoretical and computed results of the two models and the effectiveness of the proposed method was demonstrated. 相似文献
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考虑地基土液化影响的桩基高层建筑体系地震反应分析 总被引：5，自引：2，他引：5
本文建立了土体－结构体系地震反应分析的混合有限元法，并研究了地基土液化对地震反应的影响。本方法把土体－结构体系简化为一个完整的体系，该体系由梁（柱）单元、剪切杆单元、刚体单元、平面四边形等参单元与三角形单元、界面单元的任意组合来模拟。桩与上部结构材料视为线弹性体，土介质视为非线性材料。土的静应力－应变关系之间的非线性用邓肯一张模型来描述；土的动应力－应变关系之间的非线性和振动孔隙水压力对土的软化效 相似文献
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Hadi Sayyadpour Farhad Behnamfar M. Hesham El Naggar 《Bulletin of Earthquake Engineering》2016,14(8):2385-2404
Usually for modeling of soil in a direct soil–structure interaction (SSI) problem, the equivalent linear soil properties are used. However, this approach is not valid in the vicinity of a foundation, where the soil experiences large strains and a high level of nonlinearity because of structural vibrations. The near-field method was developed and described in a companion paper to overcome this limitation. This method considers the effects of large strains and suggests a shear modulus and a damping ratio further modified in the near-field of a foundation. Validity and performance of this approach are evaluated, application examples are explained and the results of a parametric study about the role of soil and structure parameters in the extent of SSI effects on the nonlinear seismic response of structures are presented in this paper. One real existing and five, ten, fifteen and twenty story moment-resisting frame steel buildings with two different site conditions corresponding to firm and soft soils are considered and the responses obtained from the near-field method are compared with the recorded and rigorous responses. Moreover, various SSI modeling techniques are employed to investigate the accuracy and performance of each approach. The results show that the near-field method is a simple yet accurate enough approach for analysis of direct SSI problems. 相似文献
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This paper aims at clarifying the role of dynamic soil–structure interaction in the seismic assessment of structure and foundation, when the non‐linear coupling of both subsystems is accounted for. For this purpose, the seismic assessment of an ideal set of bridge piers on shallow foundations is considered. After an initial standard assessment, based on capacity design principles, the evaluation of the seismic response of the piers is carried out by dynamic simulations, where both the non‐linear responses of the superstructure and of the foundation are accounted for, in the latter case through the macro‐element modeling of the soil–foundation system. The results of the dynamic simulations point out the beneficial effects of the non‐linear response of the foundation, which provides a substantial contribution to the overall energy dissipation during seismic excitation, thus allowing the structural ductility demand to decrease significantly with respect to a standard fixed‐base or linear‐elastic base assessment. Permanent deformations at the foundation level, such as rotation and settlement, turn out to be of limited amount. Therefore, an advanced assessment approach of the integrated non‐linear system, consisting of the interacting foundation and superstructure, is expected to provide more rationale and economic results than the standard uncoupled approach, which, neglecting any energy dissipation at the foundation level, generally overestimates the ductility demand on the superstructure. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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本文对无限层弹性地基中单桩基础通过特性分析建立了合理的软科学模型，按分层弹性地基土模型对桩进行动力分析，给出了桩基础轴向自振特性及在竖向地震载荷与动力载荷作用了强迫反应的解析解，文中的解析公式为无限层弹性地基中的单桩基础轴向地震反应分析提供了一种新的解析方法。 相似文献
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The problem of soil–structure interaction analysis with the direct method is studied. The direct method consists of explicitly modeling the surrounding soil to bedrock and the structure resting on the soil. For the soil medium, usually the traditional equivalent linear method with a reduced shear modulus and an increased damping ratio for the soil is used. However, this method does not work in the vicinity of foundation where the soil behavior is highly nonlinear because of presence of large strains. This research proposes a modified equivalent linear method with a further reduction of the soil shear modulus in the near-field of foundation that results in validity of using the equivalent linear method throughout. For regular short, intermediate and tall structures resting on such soft soils, a series of dynamic time-history analysis is implemented using earthquake records scaled to a sample design spectrum and the nonlinear structural responses are compared for different assumptions of soil behavior including the elasto-plastic Mohr–Coulomb, the traditional equivalent linear, and the proposed modified equivalent linear method. This analysis validates the proposed method. 相似文献