Seismic behaviour of girder bridges for horizontally propagating waves

The results obtained from a parametric study on the influence of horizontally propagating waves for the earthquake behaviour of continuous girder bridges are presented. The investigation is performed for floating-supported bridges excited by an earthquake acting in their vertical planes. The shallow foundations are assumed to be supported on the surface of either a visco-elastic halfspace or a visco-elastic layer resting on an elastic halfspace. Steady-state response for harmonic excitation and transient response for an artificial time history are investigated. Approximate equations describing the influence of horizontally propagating waves are presented and criteria are derived indicating when an increase of the internal forces and of the relative motion between the girder and the abutments can be expected.     

Effects of horizontally propagating waves on the response of structures with a soft first storey

The influence of insulating a structure with a soft first storey (horizontally elastic or elastoplastic or horizontally and vertically elastic) is investigated for horizontally propagating waves. A comprehensive parametric study for a simple structure excited by SH- and R-waves is performed. A reactor building is examined for a horizontally propagating historic earthquake. Compared to a conventional structure, travelling-wave effects become more important for R-waves in a structure with a horizontal soft first storey. For SH-waves, the opposite applies.     

局部复杂场地条件对核电结构自振特性的影响分析

自振特征是核电厂结构动力分析首先应考虑的因素,它也是影响核电厂反应谱特征的关键因素之一。采用常规的自振特性分析方法(如Lanczos法等)只能以核电厂上部结构为模型进行计算求其固有频率,在复杂场地条件下,这样的计算结果通常与更符合实际的土-结构相互作用(SSI)模型计算结果存在较大差异。本文以SASSI用户手册中的典型压水堆核电厂土-结构动力相互作用模型为研究对象,采用时域显式有限元法结合透射人工边界方法及相应编写的三维显式有限元程序3DSSI,计算了同一上部结构,结合多工况局部复杂场地条件的核电厂SSI体系的单脉冲响应,并通过求传递函数幅值谱方法,获得各种工况下SSI体系的自振频率。依据计算结果,分别研究了核电厂上部结构、自由场及SSI体系的自振特征及其相互联系,并通过比较研究,讨论了局部复杂场地特性对核电厂SSI体系自振特性影响等问题,进而加深了对核电厂动力特征及动力安全区性的认知。     

Response of beams to propagating boundary excitation

An exact solution is presented for the transient response of viscously damped Bernoulli-Euler beams with arbitrary boundary conditions that are subjected to directly applied dynamic loads in addition to arbitrary support motion. It is shown that, for certain system characteristics, the wave-like progression of the disturbance may have a significant influence on the structural response of such beams.     

核电厂取水隧洞抗震分析

运用动力时程反应分析方法,针对百万千瓦级核电厂,利用FLAC3D对其取水隧洞进行了抗震分析.针对场地的岩质特征,对不同围岩下隧洞的内力分布开展具体研究分析,绘制衬砌内力包络图.计算得出的规律可为隧洞抗震分析提供依据.     

核电站抗震研究综述

核电站抗震性一直是核电站设计的主要问题之一。随着此问题各方面研究的深入和研究手段的进步,核电站的抗震计算理论也在不断发展,本文试图根据已有的资料,在核电站抗震问题的一些主要方面（地震输入参数的确定,抗震计算理论,结构与地基的相互作用,支加速度谱及反应谱的确定,建筑物及设备的抗震计算,地基,基础及地下建筑的抗震计算等）研究状况作一些综述,并在此基础上展望一下需要解决的问题。     

Local seismic network for monitoring of a potential nuclear power plant area

This study presents a plan for seismic monitoring of a region around a potential nuclear power plant. Seismic monitoring is needed to evaluate seismic risk. The International Atomic Energy Agency has set guidelines on seismic hazard evaluation and monitoring of such areas. According to these guidelines, we have made a plan for a local network of seismic stations to collect data for seismic source characterization and seismotectonic interpretations, as well as to monitor seismic activity and natural hazards. The detection and location capability of the network were simulated using different station configurations by computing spatial azimuthal coverages and detection threshold magnitudes. Background noise conditions around Pyhäjoki were analyzed by comparing data from different stations. The annual number of microearthquakes that should be detected with a dense local network centered around Pyhäjoki was estimated. The network should be dense enough to fulfill the requirements of azimuthal coverage better than 180° and automatic event location capability down to ML?～?0 within a distance of 25 km from the site. A network of 10 stations should be enough to reach these goals. With this setup, the detection threshold magnitudes are estimated to be ML?=??0.1 and ML?=?0.1 within a radius of 25 and 50 km from Pyhäjoki, respectively. The annual number of earthquakes detected by the network is estimated to be 2 (ML?≥?～ ?0.1) within 25 km radius and 5 (ML?≥?～?0.1 to ～0.1) within 50 km radius. The location accuracy within 25 km radius is estimated to be 1–2 and 4 km for horizontal coordinates and depth, respectively. Thus, the network is dense enough to map out capable faults with horizontal accuracy of 1–2 km within 25 km radius of the site. The estimation is based on the location accuracies of five existing networks in northern Europe. Local factors, such as seismic noise sources, geology and infrastructure might limit the station configuration and detection and location capability of the network.     

Response of a circular foundation on a uniform half-space to elastic waves

An alternative technique to obtain the dynamic response of a massless rigid circular foundation resting on a uniform elastic half-space when subjected to harmonic plane waves is presented. The technique relies on the use of an integral representation involving the free-field ground motion and the contact tractions obtained in the course of calculating the dynamic force–displacement relationship of the foundation for external forces. Tables listing the translational and rotational components of the response of the foundation for non-vertically incident SH, P, SV and Rayleigh waves are presented.     

核电厂地震PSA方法研究探讨

首先回顾了地震概率安全评价(Seismic Probability Safety Assessment,SPSA)方法的发展历史及应用现状;然后基于SPSA的要素,研究了SPSA方法中需要解决的主要问题,重点是地震易损性分析,并根据SPSA的任务描述SPSA流程,主要探讨电厂走访和继电器评价的方法;最后结合我国概率安全评价(Probability Safety Assessment,PSA)的研究进展、SPSA的基础等实际状况,提出适合我国的SPSA实施路线的建议,以保障核电站地震情况下的安全.     

内陆核电厂对水库环境的影响—以咸宁核电厂为例

随着我国核电产业的迅速发展,内陆核电厂的建没成为必然趋势.本文以成宁核电厂为例,从辐射影响、余氯影响和冷却系统影响等方面,评价核电厂对富水水库可能造成的环境影响.评价结果显示,核电厂放射性释放对于水库中参考鱼类产生的总辐射剂量率为2.06×10~(-4)mGy/d,低于背景辐射本底值和国际组织推荐限值;核电厂造成的库区和下游饮水口处水体中的总β放射性,叠加本底值后仍满足1Bq/L的生活饮用水质要求;核电厂运行的化学排放和冷却系统对于水库环境的影响也很小.同时,在与美国North Anna核电厂环境影响进行比较的基础上,分析了在我国滨湖厂址建设核电厂的适宜性,并对减缓内陆核电厂对湖库环境的影响给出建议.     

累积绝对速度在核电厂地震危险性分析中的应用研究

指出了运用我国现行的考虑时空非均匀性的地震危险性分析计算方法对核电厂等设计精良的设施进行地震危险性分析时所存在的问题.介绍了累积绝对速度（CAV）的概念,并将其引入到我国现行的考虑时空非均匀性的地震危险性分析计算方法之中,用以排除厂址周围小震对核电厂地震危险性分析的影响,并选取实际工程场点进行了试算.试算结果表明,此方法能明显排除厂址周围小震对地震危险性分析结果的影响.     

计算核电厂楼层反应谱的直接法及其对比分析

核电厂的楼层反应谱分析是核电厂房主结构和设备子系统抗震设计的主要依据.楼层谱计算方法可分为2种类型,一种是通过地震动反应谱输入直接得到楼层谱的计算方法,简称直接法;另一种是通过地震波输入的时程分析计算方法,简称时程法,文中主要研究前者.首先简要评述了几种具代表性的直接法,例如Biggs方法、Kaput方法、Singh方法等,并对它们的优缺点进行了分析.然后总结了我们的工程经验,并在Biggs和Kapur方法的基础上,提出一种修正模态法,既考虑了结构-地基动力相互作用的影响,又计算简便易行,也可获得比较满意的精确度.     

Response of a plate and elastic half-space to harmonic waves

Analytical results are presented for the dynamic interaction of an elastic flexural plate and an elastic half-space subjected to harmonic seismic waves. Displacements and contact stresses are presented for square, massless plates having a practical range of flexural stiffness and subjected to incident waves oriented parallel to either an edge or a diagonal of the plate. The behaviour of massive plates is also briefly discussed; such plates exhibit additional resonances higher than those normally associated with the motion of a rigid mass.     

Environmental impact assessment of a new nuclear power plant (NPP) based on atmospheric dispersion modeling

The US Environmental Protection Agency’s short-range atmospheric dispersion model (AERMOD 12345) is a good candidate for radiological dose calculations to the general public and the environment. It advanced capability should provide better confidence in the accuracy of offsite dose and risk assessment. The code has been used to compute the scaling factors for air concentration and ground level deposition of fission products based on routine and hypothetical accident releases from the NPP site in Geregu, Nigeria (7°33′N, 6°41′E). All computations were within the 16 km emergency planing zone of a generic reactor design considered by the study. The scaling factors have been used to assess the potential environmental risk of the NPP using an integrated approach to the assessment and management of environmental risks from ionizing radiation (D-ERICA). Obtained results should provide baseline information for decision making in terms of operation license provision for the pioneer NPP.     

核电厂IHP通风围板的抗震设计优化

核电厂一体化堆顶组件(IHP)通风围板为驱动机构磁轭线圈的冷却提供了间隙均匀的通道.为了优化IHP通风围板的设计,根据ANSI/AISC N690分析了当前设计的通风围板的关键结构件在D级使用限制下的应力和变形并对关键结构件进行了初步设计优化,然后对IHP通风围板进行了有限元分析并对通风围板进行了最终设计改进.经过抗震设计优化通风围板的最大应力值分布趋于均匀.本文对抗震类设备的设计优化具有一定的参考价值.     

AP1000核电厂模型基底隔震振动台试验研究

为研究AP1000核电厂基底隔震性能,设计了缩尺比为1/40的AP1000核电厂模型结构,进行了AP1000核电厂模型基底隔震振动台试验。试验中采用铅芯橡胶隔震支座进行隔震,并选取RG1.60人工波、El Centro波和Kobe波作为地震动输入。本文从加速度响应、楼层加速度反应谱、加速度峰值放大系数、减震率等方面对隔震与非隔震核电厂结构的地震响应特性进行了研究。试验结果表明:隔震能明显减小上部结构水平向加速度响应和加速度反应谱峰值,而在隔震频率处隔震模型加速度反应谱有所增加;隔震模型由于摇摆效应在隔震频率处的水平向楼层加速度反应谱随楼层高度的升高先减小后增大;在三向输入地震动作用下,隔震和非隔震AP1000模型各楼层在竖向基频附近的竖向加速度反应谱较竖向输入的地震动放大较为明显。     

软土地基核电厂房动力响应振动台试验

为了分析软土地基－筏基础核电厂房结构地震反应规律和特征,利用地震模拟振动台开展了软土地基－筏基础－核电厂房动力相互作用问题的试验研究。分别进行了表面水平土体模型和表面凹陷土体模型的运动相互作用试验、地基土－筏基础－核电厂房振动台相互作用试验、核电厂房直接固定在振动台面上的刚性基底振动台试验。试验采用圆形叠层剪切模型箱,地基土模型为某工程场地的均匀粉质粘土,其剪切波速为213 m/s;核电厂房简化为3层框架剪力墙结构模型。试验输入波形为美国核电规范常用的RG1.60反应谱合成得到的人工地震动时程。振动台试验结果对比分析表明:土－结构体系中系统的振动周期和阻尼明显大于刚性基底下结构的振动周期和阻尼;相同地震作用下在土－结构动力相互作用体系中结构加速度明显小于刚性基底下的结构加速度反应;而位移明显大于刚性基底下结构的位移。本文的研究成果可为软土地基建立核岛厂房的适应研究提供参考。     

Aseismic safety analysis of a prestressed concrete containment vessel for CPR1000 nuclear power plant

The containment vessel of a nuclear power plant is the last barrier to prevent nuclear reactor radiation. Aseismic safety analysis is the key to appropriate containment vessel design. A prestressed concrete containment vessel (PCCV) model with a semi-infinite elastic foundation and practical arrangement of tendons has been established to analyze the aseismic ability of the CPR1000 PCCV structure under seismic loads and internal pressure. A method to model the prestressing tendon and its interaction with concrete was proposed and the axial force of the prestressing tendons showed that the simulation was reasonable and accurate. The numerical results show that for the concrete structure, the location of the cylinder wall bottom around the equipment hatch and near the ring beam are critical locations with large principal stress. The concrete cracks occurred at the bottom of the PCCV cylinder wall under the peak earthquake motion of 0.50 g, however the PCCV was still basically in an elastic state. Furthermore, the concrete cracks occurred around the equipment hatch under the design internal pressure of 0.4MPa, but the steel liner was still in the elastic stage and its leak-proof function soundness was verified. The results provide the basis for analysis and design of containment vessels.     

Resistance of soil to a horizontally vibrating pile

The resistance of a soil layer to steady horizontal vibration of an elastic pile is theoretically investigated. The pile is assumed to be vertical and of circular cross-section. The soil is modelled as a linear viscoelastic layer with hysteretic material damping. A closed form solution is obtained for the resistance of the soil layer to the motion. This resistance depends on shear modulus of soil, frequency, pile slenderness, material damping and Poisson's ratio. A parametric study of the effect of these parameters is included. The soil layer resistance is expressed in a form which can be used directly in the solution of the soil-pile interaction problem which is treated in a subsequent paper. The approach also applies for rigid deeply embedded footings.     

三角网波行面扩展最小走时射线追踪全局算法

To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces, we propose a complex structure triangular net for a minimum traveltime ray tracing global algorithm. Our procedure is: (1) Subdivide a triangle grid based on the Delaunay triangular subdivision criterion and the relationships of the points, lines, and the surfaces in the subdividing area. (2) Define the topology relationships and related concepts of triangular unit ray tracing. (3) The source point and wave arrival points at any time compose the propagating plane wave and the minimum traveltime and secondary source positions are calculated during the plane wave propagation. We adopt the hyperbolic approximation global algorithm for secondary source retrieving. (4) By minimum traveltime ray tracing, collect the path from receiver to source points with the neighborhood point’s traveltime and the direction of the secondary source. Numerical simulation examples are given to test the algorithm. The results show that the triangular net ray tracing method demonstrates model subdivision flexibility, precise velocity discontinuity interfaces, and accurate computations.