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基础隔震结构随机地震响应分析的复模态法 总被引：13，自引：1，他引：13
本文对多自由度基础隔震结构的随机地震响应问题进行了系统研究，首先建立了运动方程，然后用第一振型将上部结构展开，针对所得方程为非经典阻尼、非对称质量和非对称刚度情况，用复模态法解耦，获得了以第一振型表示的结构地震响应的解析解，对单自由度体系，此解即为结构响应的精确解，从而建立了两自由度体系在任意非经典阻尼与非对称质量和刚度情况下随机地震响应解析解分析的一般方法。本文方法也可用于带TMD减震结构、无损伤“加层减震”加固结构的随机地震响应分析与优化设计。 相似文献
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本文对多自由度基础平动结构随机地震响应问题进行了系统研究。针对用第1振型近似代表上部结构所得方程为非经典阻尼和非对称结构情况。用复模态法解耦。获得了以第1振型表示的结构地震响应的解析解。对单自由度体系。此解即为结构响应的精确解。本文方法也可用于带TMD减震结构等的随机地震响应分析与优化设计。 相似文献
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借助虚拟激励法,本文研究了非一致水平地震作用下三维车桥耦合时变系统的非平稳随机振动问题。通过轮轨间位移协调关系将列车和桥梁运动方程进行耦合,建立了考虑行波效应的多点地震激励下列车-桥梁时变系统运动方程。水平地震激励假设为均匀调制多点异相位完全相干随机激励;轨道不平顺激励假设为多点异相位完全相干平稳随机激励。采用时变系统的虚拟激励法将这些随机激励分别转化为一系列虚拟的确定性激励,然后通过数值积分求解相应的虚拟响应,进而方便地得到系统随机响应的时变功率谱密度函数和标准差等。数值算例中,通过Monte Carlo法验证了本文随机振动分析方法的正确性和有效性,并讨论了地震波视波速、场地土条件等对系统随机响应的影响。 相似文献
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大跨度结构TMD减震系统多点激励的地震随机响应分析 总被引：2，自引：1，他引：2
众多研究表明，对大跨度结构进行抗震分析时，必须采用非一致地震激励模型。本文对带TMD系统的大跨度结构考虑地震行波效应后的随机地震响应问题进行了研究。文中建立了结构的动力方程，并利用虚拟激励法求解。研究结果表明，对于大跨度结构装设TMD子结构以后可显著地降低结构的位移、速度和加速度响应，但在设计TMD减震系统时，必须考虑到地震激励的非一致性，否则可能会使预期的减震效果失效。 相似文献
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研究了应用主动锚索控制装置控制相邻建筑地震响应的有效性。首先，建立了主动锚索－相邻建筑系统的运动方程；然后应用广义振型分析方法，寻求了主动锚索联结的相邻建筑的力学特性，特别是振型阻尼比；最后，在频率域内应用广义振型分析与虚拟激励相结合的方法，建立了主动锚索控制装置联结相邻建筑的随机地震响应的分析方法。应用本文建立的公式，我们编制了计算机程序，进行了广泛的参数研究，以评价控制装置的有效性，并确定最优传感器类型及控制装置参数。研究表明，如果应用速度传感器，并能适当地选择主动锚索控制器的参数，则可以显著地提高系统的振型阻尼比，减小两个结构的地震响应。 相似文献
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为全面掌握核电超大型冷却塔的抗震性能,首先进行结构的模态分析,然后采用振型分解反应谱法和弹性时程分析方法,计算结构在多遇地震作用下的响应,并对结构进行考虑材料和几何非线性的动力弹塑性时程分析,得到结构在罕遇地震作用下的响应。由于超大塔支柱跨度达到170m,还首次对结构进行了考虑行波效应的多点激励分析。结果表明:结构前8阶振型以局部振动为主,直到第9阶出现整体倾覆振型。在多遇地震作用下,支柱的最大位移和基底剪力均满足规范要求,且水平地震反应远大于竖向地震反应。在罕遇地震作用下,支撑结构位移角远小于规范限值,出现的塑性铰数量较少,且主要分布在支柱与壳体的连接处。多点输入对支柱内力影响较为不利,而对支柱位移和塔筒内力影响较小,塑性铰出现的数量稍多且破坏程度更加严重。 相似文献
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以一座主跨为820 m的双塔非对称单侧混合梁斜拉桥为研究对象,对其进行动力特性分析。运用相对运动法进行多点激励地震响应计算,分析行波效应对塔顶、主梁、塔底等关键位置动力响应的影响,同时对比分析入射角方向（即斜拉桥两侧相对方向）对其动力响应的影响。结果表明：与一致激励分析结果相比,多点激励使得主塔内力结果偏小,而使得主梁内力结果偏大;不同入射角地震激励对非对称大跨度斜拉桥的内力也会产生较大影响,内力变化可达20%。因此,在进行该类型非对称混合梁斜拉桥设计中,应考虑非一致激励效应和地震动输入方向的影响因素。 相似文献
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多塔长跨斜拉桥受力复杂,采用轻质结合梁时结构地震响应更具特点.本文以某主跨为616m的三塔结合梁斜拉桥为工程背景,制作动力缩尺模型进行三台阵振动台试验.在单向一致激励振动台试验的基础上,进行多维激励、多点激励振动台试验,并与数值分析结果进行比较验证.试验结果表明:此结构的基本振型为中塔纵弯与主梁竖弯的耦合振动.纵向一致地震作用下,主塔及主梁均会有较大的地震响应;横向一致地震激励下,中塔地震响应较边塔更为不利.多点激励振动台试验表明,行波效应使得各构件地震响应不同程度增大;最后,通过多维地震激励下试验结果验证了规范中方向组合计算方法的准确性. 相似文献
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采用虚拟激励法,以一大跨度弦支穹顶结构—济南奥体中心体育馆为研究对象,考虑结构静力初始状态的影响,分析大跨度弦支穹顶结构多点激励随机地震响应。研究结果表明：大跨度弦支穹顶结构受行波效应与部分相干效应影响显著,考虑地震动空间变化效应使径向杆、环向杆、环索及竖向撑杆控制构件内力增幅约分别达到了50%、39%、27%及150%;其中结构不同类型、不同位置构件提升程度不同,需对具体响应具体分析;考虑地震动多维输入相比单维输入增大达到30%;行波效应与部分相干效应对结构轴力响应的影响程度存在差异;单独考虑行波效应和部分相干效应不能得到结构的最不利响应。由此得出结论：为确保大跨度弦支穹顶结构的安全,必须根据场地条件选取多种可能的地震波视波速,同时考虑部分相干效应的影响进行多维多点随机地震响应分析。 相似文献
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地震输入问题一直是工程结构抗震研究所关注的焦点.在对大跨度结构进行抗震设计时,需要考虑多点地震输入的影响已成为国内外学术界和工程界的共识.本文根据傅氏变换,运用精细传递矩阵法推导出了大跨结构在多点地震输入下的频域精细传递矩阵,并在频域内对大跨度结构进行了动力分析.这种方法公式简单,能够快速、高精度地进行结构的地震反应分析.算例显示了本文方法的有效性. 相似文献
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The observed behaviour of buildings during earthquakes indicates clearly the importance of the flexibility of floor and roof diaphragms in the response of many structures. This paper presents a new analytical method for the dynamic analysis of some one- and two-storey buildings whose floors may have significant in-plane flexibility. The method begins by treating the floors as bending beams and the walls as shear beams. The equations of motion and the boundary conditions for the floors and the walls are then formulated in one coordinate system and solved exactly to obtain the characteristic equation for the system, which can be solved numerically to obtain the natural frequencies. These, in turn, can be used to determine the mode shapes of the system and the participation factors for earthquake response. Solutions are given for one- and two-storey buildings that resist lateral loads in the transverse direction by two end walls. Perturbation techniques are also applied to simplify further the determination of the fundamental frequency of such single-storey structures. To illustrate the method, a two-storey structure, the Arvin (California) High School Administration Building, damaged in the Kern County earthquake of 1952, has been analysed in its transverse direction. It is seen that the first two modes, dominated by the floor and the roof vibrations, make the largest contributions to the total base shear in the structure. 相似文献
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结构平稳随机地震反应时域分析:方法 总被引：3，自引：3，他引：3
给出了三种常用的随机地震地面运动过程模型,即理想白噪声模型、金井清模型、改进金井清模型的相关函数表达式.引入状态向量,在状态空间中建立地震地面运动激励下的结构振动方程,并求解出结构的复模态特性和复模态反应.利用复模态叠加法推导出线性时不变多自由度体系在这三种随机地震动激励下的平稳协方差反应的解析式,可在时域内直接计算结构随机反应的统计特征.该方法物理概念清晰,结论简便明确,可作为实际工程结构平稳随机地震反应的实用分析方法. 相似文献
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It has been shown that the use of base isolation not only attenuates the response of a primary structural system but also reduces the response of a secondary system mounted on or within the main structure. The isolation system, superstructure and equipment may be made of different materials with significantly different energy dissipation characteristics such that the damping matrix for the combined system is non-classical and can only be approximately expressed by modal damping ratios if the classical mode method is used for analysis. The object of this paper is to evaluate the accuracy of this procedure in approximating the responses of base-isolated structures and internal equipment. The complex mode method can provide exact solutions to problems with non-classical damping and is used here to find the exact response of the isolation-superstructure-equipment system. The entire system is assumed to be linear elastic with viscous damping and the superstructure is assumed to be proportionally damped so that the deformation of the superstructure can be expressed in terms of its classical modes. Recognizing that the ratio of the equipment mass to the structural mass and the ratio of the stiffness of the isolation system to the superstructural stiffness are both small, perturbation methods are used to find the response. This study shows that the response of base-isolated structures can be determined by the classical mode method to some degree of accuracy, but the higher frequency content is distorted. The equipment response derived by the classical mode method is much smaller than the exact solution so that the complex mode method should be applied to find equipment response. 相似文献
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为提高大型复杂结构体系的计算效率,在深入分析约束模态综合法原理的基础上,论述了非比例阻尼体系中约束模态综合法对阻尼矩阵的处理方法,并探讨了如何缩减对接界面自由度的问题。同时,通过算例详细说明了该方法在高层建筑结构动力时程分析中的应用。计算结果表明,在利用约束模态综合法求解非比例阻尼体系的动力问题时,文中所采用的阻尼矩阵的处理方法是有效的,与有限元直接法相比具有很好的精度。对于地基土-高层建筑结构体系的地震响应分析问题而言,缩减对接界面自由度的约束模态综合法可达到很好的计算精度,能够更大程度的提高计算效率,为大型复杂结构的动力时程分析研究和工程应用提供了一定的依据和方便。 相似文献
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隔震结构的设计一般是采用时程分析算法进行的,故选择合适的地震波十分重要。而目前设计人员往往依据隔震前模型进行隔震设计,存在一定的不合理性。本文依据隔震前和隔震后两种不同的选波模型和对地震波反应谱控制频段的不同提出三种选波方案:方案一为对所选地震动的加速度反应谱在场地特征周期Tg附近的平台段和隔震前结构基本周期T1a所在下降段的控制;方案二为对在Tg附近的平台段和隔震后结构基本周期T1b所在下降段的控制;方案三为对所选地震动的加速度反应谱在Tg附近的平台段和隔震前、后两结构基本周期段的分别控制。通过对某五层混凝土框架隔震结构分别输入三种方案所选的20条地震动记录,对比隔震结构的水平向减震系数的离散性,分析罕遇地震作用下支座位移的合理性,证明方案三可以取得最优的计算结果,并提出一种基于规范设计反应谱不同频段的三频段控制选波方法。此外选取5个不同结构形式的工程算例验证三频段控制选波方法对于一般结构的适用性。 相似文献
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Bruce D. Westermo 《地震工程与结构动力学》1989,18(5):687-699
This paper examines the dynamic implications of connecting closely neighbouring structures for the purpose of eliminating pounding during earthquakes. To prevent this destructive contact the structures are connected by a link and beam system which transmits the connection forces to the floors of the structures. Four specific cases are used as examples of the effects. The coupled system is modelled as a combined mass and stiffness matrix problem which allows the traditional methods for analysis. The mode shapes and natural frequencies for these cases are examined, and it is shown that the general response characteristics can be derived from the coupled system's frequencies and modes. Estimates of the fundamental frequency of the coupled system are derived. Both the harmonic and earthquake response are examined for the four cases. In all circumstances the linkage reduces the relative overlap deflection of the structures at large amplitudes, but it also increases the base shear on the stiffer of the two structures at excitation frequencies below the fundamental frequency. It is shown that bounds on the base shear are derivable from the change in the fundamental frequencies. The dependence of the response characteristics on the stiffness of the coupling beam is also examined. 相似文献
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An innovative approximate method is presented to consider the plan asymmetry, nonlinear structural behaviour and soil-structure interaction (SSI) effects simultaneously. The proposed method so-called Flexible base 2DMPA (F2MPA) is an extension of 2 degrees of freedom modal pushover analysis (2DMPA) approach to consider foundation flexibility in seismic response analysis of plan asymmetric structures which itself were developed based on Uncoupled Modal Response History Analysis method for inelastic fixed-base asymmetric structures. In F2MPA for each mode shape using 2DMPA procedure, the elastic and inelastic properties of 2DOF modal systems corresponding to the fixed-base structure are initially derived. Then in each time step, displacements and inelastic restoring forces of the superstructure are computed from modal equations of the flexibly-supported structure. In each time step, the nonlinear secant stiffness matrix corresponding to the n-th MDOF modal equations of soil-structure system is updated using the corresponding modal 2DOF system of fixed-base structure. To update the transformed modal stiffness matrix of the SSI system, this matrix is partitioned and it is assumed that the non-linear variation of the superstructure can be estimated from the variation of modal stiffness matrix of the fixed-base structure. Accuracy of the proposed method was verified on an 8-story asymmetric-plan building under different seismic excitations. The results obtained from F2MPA method were compared with those obtained by nonlinear response history analysis of the asymmetric soil-structure system as a reference response. It was shown that the proposed approach could predict the results of the nonlinear time history analysis with a good accuracy. The main advantage of F2MPA is that this method is much less time-consuming and useful for the practical aims such as massive analysis of a nonlinear structure under different records with multiple intensity levels. 相似文献