S7—200／10型变压器抗震分析

本文采用有限元法分析了电力变压器结构的抗震特性，并考虑了其中液体对变压器结构动力特性的影响，文中提供了一种可供变压器结构抗震分析的方法，并以Ｓ７－２００／１０型变压器为例进行了理论计算和原型实验。结果表明：本文提供的分析方法是可靠的，可以满足变压器行业抗震设计分析的需要。     

高压变压器抗震可靠度分析

首先分析了变压器的震害特征，措出了变压器的抗震薄弱环节，根据变压器绝缘瓷件的结构特点，建立了具有柔性结点的有限元分析计算模型，应用高压电气设备抗震可靠性分析方法，对高压变压器进行了抗震可靠性计算，计算结果表明，高压变压器顶部瓷件在低烈度下的抗震性能良好，抗震可靠性指标较高，本文所得结果可为高压电气设备抗震性能评价与区域电力系统抗震可靠性分析提供基础。     

异形柱抗震性能分析

异形柱框架结构是1种新型节能住宅结构,本文利用有限元软件,采用反应谱方法,从异形柱与矩形柱框架结构在地震作用下的变形特性和位移着手,研究2种结构的抗震性能,得出了异形柱的抗震性能好的结论。     

抗震分析反应谱法和时程分析法数值仿真比较

基于ANSYS有限元软件比较抗震分析反应谱法和时程分析法的地震数值仿真结果,研究二者的共同性和仿真结果的可比较性。结果表明,反应谱法和时程分析法在抗震反应计算中都体现了地震动特性和结构动态特性对结构地震响应的影响,二者在响应最值和响应频率上的仿真结果具有一致性。     

S7-200/10 变型变压器抗震分析

本文采用有限元法分析了电力变压器结构的抗震特性，并考虑了其中液体对变压器结构动力特性的影响。文中提供了一种可供变压器结构抗震分析的方法，并以Ｓ７－２００／１０型变压器为例进行了理论计算和原型实验。结果表明：本文提供的分析方法是可靠的，可以满足变压器行业抗震设计分析的需要。     

变压器结构的动力反应分析

采用有限元法分析了电力变压器本体结构的自振特性，并给出了考虑其中液体影响的变压器结构抗震的分析方法。以Ｓ７－２００／１０型变压器为实例，进行了理论计算和原型实验，结果表明，本文的分析方法是可靠的，可以用于变压器抗震设计分析。     

某核电站常规岛抗震分析

核电常规岛主厂房与一般火力发电主厂房结构特点不同,其结构布置很不规则,质量分布也不均匀。本文使用有限元分析软件ANSYS建立力学模型,对常规岛结构进行了抗震分析,主要运用了振型分解反应谱法对结构进行了内力计算,为结构设计奠定了基础。     

某核电站常规岛抗震分析

核电常规岛主厂房与一般火力发电主厂房结构特点不同,其结构布置很不规则,质量分布也不均匀.本文使用有限元分析软件ANSYS建立力学模型,对常规岛结构进行了抗震分析,主要运用了振型分解反应谱法对结构进行了内力计算,为结构设计奠定了基础.     

南水北调台儿庄泵站抗震安全性评价

以南水北调台儿庄泵站为研究对象,运用三维有限单元法以及反应谱理论分析该泵站的动力特性和动力响应。根据上部结构与泵站站身刚度相差较大的特点,提出了分别计算各自的动力特性,再利用反应谱理论组合法求解结构动力响应的计算方法。计算结果证明,台儿庄泵站设计合理,整体结构的抗震安全性满足设计规范要求。     

特高压悬吊换流阀塔抗震分析

基于ANSYS有限元软件,建立单塔换流阀体的有限元模型,通过模态分析计算结构的动态特性,应用反应谱法计算换流阀塔的地震响应.在抗震分析计算中考虑结构的预应力效应和大变形效应,并考虑地震载荷和重力载荷的组合作用.计算结果表明,主要影响地震响应的振型是水平向的摆动和扭转振型,换流阀塔水平摆动的地震响应位移稍大,应在阀厅的布置设计中予以考虑.     

500kV电流互感器抗震性能分析

地震给电力设备带来严重破坏,需要加强对电力设备抗震性能方面的研究.根据GB 50260-1996电力设备抗震设计规范,阐述了振型分解反应谱理论计算电力设备地震响应的基本内容及步骤,结合500kV电流互感器抗震性能评估的工程实例,应用强度破坏准则对模型进行了抗震性能验算.结果表明,该互感器可满足抗震设防烈度为9度地区的使用要求;根据危险断面出现位置,给出提高抗震性能的几点措施,可为其他电力设备抗震性能优化提供参考.     

Seismic behaviour of shallow foundations: Shaking table experiments vs numerical modelling

The capability of a simplified approach to model the behaviour of shallow foundations during earthquakes is explored by numerical simulation of a series of shaking table tests performed at the Public Works Research Institute, Tsukuba, Japan. After a summary of the experimental work, the numerical model is introduced, where the whole soil–foundation system is represented by a multi‐degrees‐of‐freedom elasto‐plastic macro‐element, supporting a single degree‐of‐freedom superstructure. In spite of its simplicity and of the large intensity of the excitation involving a high degree of nonlinearity in the foundation response, the proposed approach is found to provide very satisfactory results in predicting the rocking behaviour of the system and the seismic actions transmitted to the superstructure. The agreement is further improved by introducing a simple degradation rule of the foundation stiffness parameters, suitable to capture even some minor details of the observed rocking response. On the other hand, the performance of the model is not fully satisfactory in predicting vertical settlements. Copyright © 2007 John Wiley & Sons, Ltd.     

Seismic modelling for geological fractures

Based on knowledge of a commutative group calculation of the rock stiffness and on some geophysical assumptions, the simplest fractured medium may be regarded as a fracture embedded in an isotropic background medium, and the fracture interface can be simulated as a linear slip interface that satisfies non‐welded contact boundary conditions: the kinematic displacements are discontinuous across the interface, whereas the dynamic stresses are continuous across the interface. The finite‐difference method with boundary conditions explicitly imposed is advantageous for modelling wave propagation in fractured discontinuous media that are described by the elastic equation of motion and non‐welded contact boundary conditions. In this paper, finite‐difference schemes for horizontally, vertically, and orthogonally fractured media are derived when the fracture interfaces are aligned with the boundaries of the finite‐difference grid. The new finite‐difference schemes explicitly have an additional part that is different from the conventional second‐order finite‐difference scheme and that directly describes the contributions of the fracture to the wave equation of motion in the fractured medium. The numerical seismograms presented, to first order, show that the new finite‐difference scheme is accurate and stable and agrees well with the results of previously published finite‐difference schemes (the Coates and Schoenberg method). The results of the new finite‐difference schemes show how the amplitude of the reflection produced by the fracture varies with the fracture compliances. Later, comparisons with the reflection coefficients indicate that the reflection coefficients of the fracture are frequency dependent, whereas the reflection coefficients of the impedance contrast interface are frequency independent. In addition, the numerical seismograms show that the reflections of the fractured medium are equal to the reflections of the background medium plus the reflections of the fracture in the elastic fractured medium.     

Seismic modelling,development and outlook

Резюме Описаны этапы развития сейсмического моделирования, взаимоотношения между сейсмическим моделированием, теоретическими разработками и полевыми наблюдениями и формулированы перспективные задачи сейсмического моделирования.

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Address: B. Gruzinskaja 10, Moskva G-242, USSR.     

Seismic modelling study of a subglacial lake

We characterize the seismic response of Lake Vostok, an Antarctic subglacial lake located at nearly 4 km depth below the ice sheet. This study is relevant for the determination of the location and morphology of subglacial lakes. The characterization requires the design of a methodology based on rock physics and numerical modelling of wave propagation. The methodology involves rock-physics models of the shallow layer (firn), the ice sheet and the lake sediments, numerical simulation of synthetic seismograms, ray tracing, τ–p transforms, and AVA analysis, based on the theoretical reflection coefficients. The modelled reflection seismograms show a set of straight events (refractions through the firn and top-ice layer) and the two reflection events associated with the top and bottom of the lake. Theoretical AVA analysis of these reflections indicates that, at near offsets, the PP-wave anomaly is negative for the ice/water interface and constant for the water/sediment interface. This behaviour is shown by AVA analysis of the synthetic data set. This study shows that subglacial lakes can be identified by using seismic methods. Moreover, the methodology provides a tool for designing suitable seismic surveys.     

Seismic risk mitigation technique for art objects: experimental evaluation and numerical modelling of double concave curved surface sliders

The opportunity and the advantages of applying base isolation technologies developed for civil structures to small objects are investigated and some considerations related to the scale effects are discussed. A series of experimental tests carried out at SRMD facility in San Diego are presented with the aim to investigate the dynamic response of a system designed to simulate a sculpture isolated by means of Double Concave Curved Surface Sliders. Such devices are specifically re-designed to fit the peculiar situation of light weight objects. In particular the samples used in the experimentation are designed with geometric and inertia characteristics fit for representing the Michelangelo’s sculptures exposed at the “Galleria dell’Accademia” in Florence, Italy. Finally, the main aspects concerning the numerical simulation of the seismic response of the proposed isolated system are discussed, also to investigate the efficiency of the existing numerical models, which are developed for traditional devices, when they are applied on such small and particular objects. The results of the experimental/numerical campaign show a general efficiency of the isolation system in terms of limiting the transferred action. Further study is needed to understand more clearly some local unexpected phenomena emerged from the experimental tests.     

Estimating reference evapotranspiration using numerical weather modelling

Evapotranspiration is an important hydrological process and its estimation usually needs measurements of many weather variables such as atmospheric pressure, wind speed, air temperature, net radiation and relative humidity. Those weather variables are not easily obtainable from in situ measurements in practical water resources projects. This study explored a potential application of downscaled global reanalysis weather data using mesoscale modelling system 5 (MM5). The MM5 is able to downscale the global data down to much finer resolutions in space and time for use in hydrological investigations. In this study, the ERA‐40 reanalysis data are downscaled to the Brue catchment in southwest England. The results are compared with the observation data. Among the studied weather variables, atmospheric pressure could be derived very accurately with less than 0·2% error. On the other hand, the error in wind speed is about 200–400%. The errors in other weather variables are air temperature (<10%), relative humidity (5–21%) and net radiation (4–23%). The downscaling process generally improves the data quality (except wind speed) and provides higher data resolution in comparison with the original reanalysis data. The evapotranspiration values estimated from the downscaled data are significantly overestimated across all the seasons (27–46%) based on the FAO Penman–Monteith equation. The dominant weather variables are net radiation (during the warm period) and relative humidity (during the cold period). There are clear patterns among some weather variables and they could be used to correct the biases in the downscaled data from either short‐term in situ measurements or through regionalization from surrounding weather stations. Artificial intelligence tools could be used to map the downscaled data directly into evapotranspiration or even river runoff if rainfall data are available. This study provides hydrologists with valuable information on downscaled weather variables and further exploration of this potentially valuable data source by the hydrological community should be encouraged. Copyright © 2010 John Wiley & Sons, Ltd.