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1.
考虑土-结构相互作用和岩土参数不确定性的核电厂结构地震响应分析 总被引:2,自引:0,他引:2
针对核电厂结构,在考虑土-结构相互作用(SSI)的情况下进行随机地震反应分析,探讨地基岩土参数的不确定性对反应堆厂房楼层反应谱(FRS)的影响。运用ANSYS软件模块建立核电厂(NPP)结构有限元模型,通过设置边界弹簧单元和阻尼装置来考虑SSI效应;并且通过设置具有概率意义的弹簧刚度和阻尼系数,来模拟土特性参数的不确定性。随机响应分析与确定性分析的结果对比,揭示了岩性地基条件下SSI效应对核电厂FRS的影响以及地基岩土参数不确定性对FRS的影响程度。研究表明,在岩性地基条件下,亦不应忽略SSI效应;考虑SSI效应的随机分析模型同确定性模型相比,二者的分析结果较为接近,两方法都可用于NPP的FRS敏感性分析评估之中,并可进行相互比照。 相似文献
2.
R. H. Scanlan 《地震工程与结构动力学》1976,4(4):379-388
One of the most common hypotheses implicit in the seismic analyses of structures is that the earthquake input motion is identical at all points beneath the structure. Very little experimental evidence presently is available to supplant this viewpoint. However, one may infer a spatially distributed surface motion of the soil if the earthquake is simply assumed to consist of a complex of surface waves traversing the plan of the structural site. Under these conditions, as shown in the paper, the effects of passing waves must be integrated over the structural area to obtain their net effects as exciting functions to the structure. When this is done for individual Fourier components of the quake, one important result is the diminution or ‘self-cancelling’ effect of some inputs, particularly for those waves the wavelengths of which are comparable to the dimensions of the structure, or shorter. Another important effect is the torsional excitation of the structure. The present paper is not necessarily aimed at replacing present analysis methods but at discussing some of the effects which will inevitably be entrained by the introduction of any information or hypotheses regarding the spatial distribution of earthquake motions. This analysis tends to suggest why higher frequencies are of lesser importance for a structure having a large rigid foundation. 相似文献
3.
J. P. Wolf 《地震工程与结构动力学》1977,5(4):337-363
The seismic response due to a travelling shear wave is investigated. The resulting input consists of a translational-and a torsional-acceleration time history, which depend on the ratio of the wavelength to the dimension of the footing. A nuclear reactor building is used for illustration. The combined result of the translational and torsional elastic response (the latter arises even in an axisymmetric structure) will not, in general, be larger than that encountered in the case of a spatially uniform earthquake. If the footing slips or becomes partially separated from the soil, a non-linear dynamic analysis has to be performed to determine the response. Substantial motions in all three directions will take place. The peak structural responses and the floor-response spectra are found to be highly non-linear for high acceleration input values. 相似文献
4.
Damping of structures resting on flexible foundations is affected by soil-structure interaction in two ways: (1) the structure gains damping through energy dissipation in soil, and (2) the damping the structure would have on a rigid foundation is reduced. These effects are evaluated using two approaches: an energy consideration which is a simple but approximate approach, and the complex eigenvalue analysis which is mathematically accurate but uses damped, non-classical vibration modes. These two methods are compared and the accuracy of the more convenient energy approach is assessed. Examples of modal damping are given for rigid structures, buildings and towers. 相似文献
5.
考虑土-结构相互作用双层柱面网壳在多点输入下的地震反应分析 总被引:3,自引:0,他引:3
目前对于网壳结构的地震反应研究大部分仍然采用一致输入,特别是没有考虑土-结构相互作用对网壳结构的影响。本文通过对大型有限元分析软件MSC.Nastran的二次开发,用等效线性化方法考虑土体的非线性,对土体采用三维实体单元建模,并对土体在基岩面上采用地震动的多点输入,计算分析了大跨度双层柱面网壳的动力反应,并且与一致地震动输入下网壳结构的地震反应进行了对比,考察了两者之间的差异,深入分析了考虑土-结构相互作用下,双层柱面网壳结构在多点输入和一致输入下的地震反应规律,并得出了一些重要结论。 相似文献
6.
This paper presents an effective analysis procedure for the dynamic soil-structure interaction problem considering not only the sliding and separation phenomena but also the non-linear behaviour of soil by the finite element method. Soil is assumed to be an elasto-plastic material and the contact surface between the soil and structure is modelled by the joint element. The load transfer method is adopted to carry out dynamic non-linear response analysis. The method is applied to the response analysis of a nuclear reactor building resting on the ground surface. The effects of non-linear behaviour of soil on the safety against sliding of the structure are examined. The numerical computations reveal the following results: that the non-linear behaviour of soil reduces the response of the system and the magnitude of sliding of the structure, and that the safety against sliding obtained by the proposed method is higher than the safety obtained by classical methods. This implies the possibility of a more rational and economical design of large structures; it can be said that the proposed method provides useful information for the stability analysis of important and large structures. 相似文献
7.
考虑SSI效应的立式储罐水平基础隔震研究 总被引:2,自引:0,他引:2
立式储罐在地震作用下破坏严重,损失较大.为了降低立式储罐在水平地震激励下的地震响应,考虑土与结构相互作用对储罐地震响应的影响,将立式储罐基础隔震体系简化为3质点5自由度力学模型.依据Hamilton原理建立立式储罐基础隔震体系的控制方程,给出了立式储罐基底剪力、倾覆弯矩、晃动波高和应力的理论表达.选取150000m3储罐,采用wilson-θ法对其进行了地震动响应分析.结果表明:储罐基础隔震体系能够降低储罐的地震响应;为获得理想的地震响应,场地、隔震周期和阻尼比存在优化取值区间;储罐抗震与减震设计要视设计安全需要来决定是否考虑土与结构的相互作用. 相似文献
8.
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
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Models of two-dimensional x-braced elevated tanks supported on isolated footings are analyzed to investigate the effects of dynamic interaction between the tower and the supporting soil-foundation system. Static, dynamic elastic, and dynamic inelastic responses of towers under horizontal ground motions are evaluated. Effects of soil properties, represented by the shear wave velocity, on joint displacements and on member end actions are studied. In general, soil-tower interaction reduces member end actions except near the base of tower. 相似文献
11.
This paper attempts to assess the effects of dynamic soil-structure interaction (SSI) on the seismic behavior of a PC cable-stayed bridge placed on a moderately deep soil stratum overlying rigid bedrock, and to evaluate the applicability of a simple mass-spring model in evaluating SSI. Parametric analysis is performed to investigate the significance of SSI under various stiffness, foundation depth conditions using finite element methods. The applicability of a mass-spring model is discussed by comparison with FEM. The results of analysis reveal the influence of SSI on the seismic behavior of bridge-soil system, and recommendations for aseismic design are provided. The mass-spring model proves to be promising for representing the seismic behavior of the bridge-soil system, and the mechanism is interpreted in detail. 相似文献
12.
土-结构相互作用效应对结构基底地震动影响的试验研究 总被引:3,自引:0,他引:3
利用土与结构动力相互作用振动台模型试验数据,通过各种试验工况下土层表面与基础表面加速度反应的比较,深入探讨了土与结构动力相互作用效应对高层建筑结构基底地震动的影响。从输入地震动频谱特性、输入地震动强度水平和上部结构动力特性3个方面详细分析了与SSI效应对高层建筑基底震动影响程度有关的一些因素。结果表明:SSI效应对高层建筑基底地震动的影响与输入地震波的动力特性有很大关系。在地震动的频谱成分方面,SSI效应对高层建筑基底地震动的影响主要体现为土层表面和基础表面在与输入地震动卓越频率相近处的频谱成分有较大差异;SSI效应对高层建筑基底地震动的影响程度随着输入加速度峰值水平的增加而减小;在某一特定地震波作用下,当上部结构的振动频率与地震地面运动的卓越频率相近时,SSI效应对高层建筑基底地震动的影响较为强烈。 相似文献
13.
In this study, simplified numerical models are developed to analyze the soil-structure interaction (SSI) effect on frame structures equipped with viscoelastic dampers (VEDs) based on pile group foundation. First, a single degree-of-freedom (SDOF) oscillator is successfully utilized to replace the SDOF energy dissipated structure considering the SSI effect. The equivalent period and damping ratio of the system are obtained through analogical analysis using the frequency transfer function with adoption of the modal strain energy (MSE) technique. A parametric analysis is carried out to study the SSI effect on the performance of VEDs. Then the equilibrium equations of the multi degree-of-freedom (MDOF) structure with VEDs considering SSI effect are established in the frequency domain. Based on the assumption that the superstructure of the coupled system possesses the classical normal mode, the MDOF superstructure is decoupled to a set of individual SDOF systems resting on a rigid foundation with adoption of the MSE technique through formula derivation. Numerical results demonstrate that the proposed methods have the advantage of reducing computational cost, however, retaining the satisfactory accuracy. The numerical method proposed herein can provide a fast evaluation of the efficiency of VEDs considering the SSI effect. 相似文献
14.
Effect of depth of soil stratum on estimated inelastic displacement of three typical structures, viz. a four storey building, a continuous bridge, and a tower, is studied and adequacy of the site amplification models of the current design codes and available empirical relationships is examined. The structures are assumed to be located on well-defined sites with varying bedrock depths, and effect of depth on elastic response spectrum, site amplification factor, displacement modification factor and inelastic displacement is studied, numerically, for two values of PGA. It is observed that soil depth has a significant effect on elastic as well as inelastic response of the structures; however, the effect of soil amplification on inelastic response is not as pronounced as in case of elastic response. Therefore, use of empirical site amplification models based on elastic response may be too conservative, for estimating inelastic response. 相似文献
15.
本文用墙单元将剪力墙中断的框架-剪力墙结构离散,利用传递矩阵技术探讨此不规则框架-剪力墙结构的地震反应,四阶Runge-Kutta法用来求解用正则坐标写出的对应于第j个振型的运动方程.将得到的3个不同剪力墙高度的钢筋混凝土框架-剪力墙模型结构的固有频率、最大位移反应和基底剪力与振动台的试验结果进行对比,说明本数值方法是正确的、有效的.最后得出了并不是对所有的框架-剪力墙结构都需把其剪力墙延伸到整个结构高度的结论以及用墙单元和传递矩阵技术求解能有效地减少计算单元、取得同样精度的计算结果. 相似文献
16.
In this research, a parametric study is carried out on the effect of soil–structure interaction on the ductility and strength demand of buildings with embedded foundation. Both kinematic interaction (KI) and inertial interaction effects are considered. The sub‐structure method is used in which the structure is modeled by a simplified single degree of freedom system with idealized bilinear behavior. Besides, the soil sub‐structure is considered as a homogeneous half‐space and is modeled by a discrete model based on the concept of cone models. The foundation is modeled as a rigid cylinder embedded in the soil with different embedment ratios. The soil–structure system is then analyzed subjected to a suit of 24 selected accelerograms recorded on alluvium deposits. An extensive parametric study is performed for a wide range of the introduced non‐dimensional key parameters, which control the problem. It is concluded that foundation embedment may increase the structural demands for slender buildings especially for the case of relatively soft soils. However, the increase in ductility demands may not be significant for shallow foundations with embedment depth to radius of foundation ratios up to one. Comparing the results with and without inclusion of KI reveals that the rocking input motion due to KI plays the main role in this phenomenon. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
17.
To alleviate some of the shortcomings associated with the statistically based inelastic spectral shapes, a rigorous method for the construction of inelastic design spectra is proposed. The method is based on several bounds which are derived from the differential equation of motion for a single degree of freedom system. Comparisons of the proposed spectral bounds with the actual elastoplastic response spectra and with the 84 per cent Newmark elastoplastic design spectra reveal that the proposed method yields a more economical, reliable and simple design aid. To demonstrate the quality of the proposed bounds, comparisons of the bounding spectra with their corresponding constant ductility elastoplastic response spectra for a number of records have been presented. 相似文献
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A three-dimensional hybrid model for the analysis of soil-structure interaction under dynamic conditions is developed which takes advantage of the desirable features of the finite element and substructure methods and which minimizes their undesirable features. The modelling is achieved by partitioning the total soil-structure system into a near-field and a far-field with a hemispherical interface. The near-field, which consists of the structure to be analysed and a finite region of soil around it, is modelled by finite elements. The semi-infinite far-field is modelled by distributed impedance functions at the interface which are determined by system identification methods. Numerical results indicate that the proposed model makes possible realistic and economical assessment of three-dimensional soil-structure interaction for both surface and embedded structures. 相似文献
20.
开展了土-结构动力相互作用的模型试验,探讨了框架结构的近似有效基本周期,并研究了考虑相互作用效应的界限.模型试验中分别进行了刚性地基和柔性地基条件下的结构基本周期测试,并通过与理论计算结果的比较,验证了FEMA450中建议的有效基本周期计算方法能够有效预测土-结构相互作用效应的影响.利用FEMA450中建议的刚性地基上普通钢筋混凝土框架结构基本周期近似值的计算式,分别建立了明置基础、埋置基础的框架结构有效基本周期近似值的计算式,并以此分析了框架结构考虑相互作用的界限问题,提出了考虑埋置深度影响的合理界限. 相似文献