不同高度面板堆石坝幅频反应的比较研究

一定的坝址地基未来所可能产生地震的卓越周期有一定范围，面板堆石坝的动力设计应尽量使坝体的高反应频率带与地基的卓越频率远离，不同高度面板堆石坝幅频反应比较研究的目的是弄清楚不同高度坝体的高动力反应频率带，为坝址与坝高的配套选择提供参考。本文通过对50m,100m,150m,200m面板堆石坝幅频反应的研究表明，面板堆石坝最适合修建在岩基上，高坝比低坝适合修建的地基范围更广。     

猴子岩高面板堆石坝地震模拟振动台模型试验研究

本文介绍了猴子岩水电站大坝振动台模型试验的概况,包括模型设计、模型制作、加速度传感器埋设、位移测点布置和试验工况设计等,并给出了主要的试验结果。试验研究表明,大坝结构的动力特性受振动强度和振动历史等因素影响,空间位置、输入地震动强度及类型、蓄水等因素对大坝结构的地震反应特性有重要影响。这些研究成果不仅可为大坝的抗震设计提供参考,而且是验证和改进地震动力反应分析方法和计算程序的重要资料。     

深厚库底回填料上面板堆石坝动力反应分析

深厚库底回填料是影响面板堆石坝动力响应的重要因素之一。为深入研究深厚库底回填料对面板堆石坝动力响应的影响,基于某拟建抽水蓄能电站,采用三维动力有限元分析系统研究其上库面板坝的地震反应,主要包括坝体加速度、面板动力响应、接缝变位情况以及库底防渗土工膜的动应变等。计算结果表明:由于库底回填料的存在,坝体加速度放大效应被明显削弱;面板周边以受拉为主,中部大部分区域受压;垂直缝呈现出周边张开、中间闭合的趋势;土工膜的顺河向和坝轴向的动拉应变皆小于屈服应变,最大应变出现在库底材料分界处,为提高坝体渗透安全性,建议对主堆石区与连接板相接处的回填料进行适当范围换填的处理措施。研究成果可以为类似工程提供参考。     

面板堆石坝的动力离心模型试验研究

为研究面板堆石坝的地震响应规律,采用Parkfield波作为地震动输入,在清华大学50g-t土工离心机上进行了动力离心模型试验.试验在50倍重力加速度条件下采用电液伺服离心机振动台系统完成,采用加速度传感器测量了模型不同位置动力响应的加速度时程并且测量了面板的变形.结果表明,地震最大响应发生于坝顶,该处地震动放大系数接...     

不同减隔震支座对跨断层桥梁地震响应的影响

为研究不同减隔震支座对跨断层桥梁横向地震响应的影响,以三跨简支梁桥为工程背景,用SAP2000建立有限元模型,并采用非一致多点激励输入的方式进行非线性时程分析.结果表明:在盆式支座、铅芯橡胶支座和摩擦摆式支座3种体系下,相较于盆式支座,后两种减隔震支座的引入可减小断层错动带来的结构约束扭转效应,降低下部结构响应水平,使...     

黄土高原混凝土建筑物的地震随机反应分析

本文利用随机振动理论和动力分析有限元法,计算了在9度地震作用下黄土高原混凝土建筑物在随机地震下响应的统计特性,分析了黄土层对混凝土建筑物地震反应的影响。     

基于严格条分法的拟动力地震边坡稳定性分析方法研究

将拟动力法基本原理与极限平衡法中的严格条分法(Sarma法)相结合,推导边坡地震力和安全系数的计算公式;在此基础上,基于Python语言开发相应的计算程序,实现一种考虑波动效应的、适用于任意滑面形状和任意滑块条分的拟动力地震边坡稳定性分析新方法;同时,探讨地震动特性和结构面强度对边坡地震稳定性的影响。研究表明：随着地震波初始相位的变化,边坡的安全系数呈现周期性的波动变化,且存在最小安全系数;边坡安全系数随着地震动幅值和地震波波长/坡高比的增大而减小;当滑块结构面抗剪强度参数下降时,边坡安全系数随之减小。此外,通过波动理论揭示拟静力法与拟动力法的区别与联系：当地震波波长与坡高比大于10时,两种方法的结果基本一致;当地震波波长与坡高比小于10时,拟静力法所得结果比拟动力法保守,拟动力法更合理。     

高强钢筋高强混凝土框架结构非线性地震反应分析

研究配有高强钢筋的高强混凝土框架结构的抗震性能.采用OpenSees开放式软件对配有高强钢筋的高强混凝土框架结构进行了地震作用下的非线性有限元分析,并将计算结果与同等参数条件下的结构拟动力试验进行了对比.得到不同峰值加速度情况下的结构层间反应时程曲线,层间位移滞回曲线,以及破坏模式等,数值计算结果与试验吻合程度较好.研究结果表明利用基于OpenSees的有限元分析方法,能够有效地分析配有高强钢筋的高强混凝土框架结构的地震响应,可以辅助研究该结构的抗震性能.     

地震波斜入射对高面板坝地震反应的影响

为研究地震波斜入射对高面板坝地震反应的影响,根据地震波动入射理论,采用FORTRAN进行波动荷载的编程计算,并与大型通用有限元软件ADINA相结合,实现基于黏弹性人工边界的地震波斜入射,研究P波和SV波分别以不同角度入射对高面板堆石坝地震反应的影响。结果表明,地震波斜入射时大坝地震动反应与垂直入射时明显不同,常规垂直入射的结果偏于不安全,因此在高面板坝地震反应分析和抗震设计中应考虑地震波斜入射的影响。     

坝料流变对高面板堆石坝的应力变形影响研究

在高应力状态下坝料的流变较为明显。为研究坝料流变对混凝土面板坝应力变形的影响,采用长科院九参数幂级数流变模型及其试验参数,对某高混凝土面板堆石坝进行应力、变形分析。结果表明,坝料流变使坝体变形明显增加,坝体应力有所减小。考虑坝料的流变特性后的面板法向位移(挠度)明显增加,面板坝轴向和顺坡向应力极值增加。对于分期浇筑面板和分期蓄水的高混凝土面板堆石坝,选用合适的流变本构模型正确地模拟堆石体的流变特性,可以为大坝填筑进度及面板分期浇筑时间的确定提供参考,并有助于正确地预测大坝的应力变形。     

Assessment of the seismic performance of a bituminous faced rockfill dam

In the attempt to codify a procedure exportable to other similar cases, a thorough investigation of the seismic performance of a bituminous concrete faced rockfill dam built in Italy in the early eighties is herein presented. The dam presents a 90 m tall embankment built in a narrow canyon and is situated in a highly seismic region. The implemented methodology encompasses the indications provided by the most recent literature to point out the problems potentially caused by earthquakes and to account for the paramount factors affecting the response of the dam. Particular attention has been paid to the concept of performance, defining its goals in accordance with the most recent standards and deriving the correspondent limit conditions from observations reported in the literature. In order to optimize the computational effort, dynamic analyses with two and three dimensional finite difference codes have been combined to study the coupled response of the embankment, rocky foundation and bituminous facing. After validating the numerical models with centrifuge tests performed on small scale models of the embankment, the performance of the dam has been investigated with reference to a number of possible scenarios focusing on the amplification spectra, the deformation of the embankment and the integrity of the bituminous lining.     

Influence of seismic input mechanisms and radiation damping on arch dam response

In this study, two different earthquake input models are introduced, i.e. massless foundation model and viscous-spring boundary input model considering radiation damping. Linear elastic and nonlinear contraction joint opening analyses of the 210 m high Dagangshan arch dam under construction in China are performed using the two different earthquake input models. First, the responses of the three-dimensional (3-D) canyon without the dam are analyzed, respectively, with massless-truncated foundation and with viscous-spring boundary; second, linear and nonlinear analyses of the dam–foundation system are performed and compared by using the two input models. Hydrodynamic effects are considered using finite element discretization for incompressible reservoir fluid. It is concluded that stresses and displacements and contraction joint opening in the dam are significantly reduced both in linear and nonlinear analyses when using viscous-spring boundary model. Interestingly, in the case of linear analysis of the Dagangshan, the massless foundation input model with a relatively higher damping ratio of 10% leads to a comparable response of the dam to that using viscous-spring boundary model. In addition, the maximum tensile stresses from nonlinear analysis are 10–25% larger than that of the corresponding linear cases due to a partial release of the arch action.     

Influence of seismic wave type and incident direction on the dynamic response of tall concrete-faced rockfill dams

Owing to the stochastic behavior of earthquakes and complex crustal structure, wave type and incident direction are uncertain when seismic waves arrive at a structure. In addition, because of the different types of the structures and terrains, the traveling wave effects have different influences on the dynamic response of the structures. For the tall concrete-faced rockfill dam (CFRD), it is not only built in the complex terrain such as river valley, but also its height has reached 300 m level, which puts forward higher requirements for the seismic safety of the anti-seepage system mainly comprising concrete face slabs, especially the accurate location of the weak area in seism. Considering the limitations of the traditional uniform vibration analysis method, we implemented an efficient dynamic interaction analysis between a tall CFRD and its foundation using a non-uniform wave input method with a viscous-spring artificial boundary and equivalent nodal loads. This method was then applied to investigate the dynamic stress distribution on the concrete face slabs for different seismic wave types and incident directions. The results indicate that dam-foundation interactions behave differently at different wave incident angles, and that the traveling wave effect becomes more evident in valley topography. Seismic wave type and incident direction dramatically influenced stress in the face slab, and the extreme stress values and distribution law will vary under oblique wave incidence. The influence of the incident direction on slab stress was particularly apparent when SH-waves arrived from the left bank. Specifically, the extreme stress values in the face slab increased with an increasing incident angle. Interestingly, the locations of the extreme stress values changed mainly along the axis of the dam, and did not exhibit large changes in height. The seismic safety of CFRDs is therefore lower at higher incident angles from an anti-seepage perspective. Therefore, it is necessary to consider both the seismic wave type and incident direction during seismic capacity evaluations of tall CFRDs.     

Dynamic response of concrete face rockfill dam affected by polarity reversal of near-fault earthquake

In China, an increasing number of high concrete face rockfill dams(CFRDs) are located in high intensity earthquake zones, some of which are close to the seismic fault line. Recordings suggest that near-fault ground motions are characterized by large one-sided velocity pulses. The conventional dynamic analysis of dams, however, neglects the features of strong ground movements. In this study, under different ground motion levels some numerical dynamic studies considering the one-sided broadband pu...     

Longitudinal vibrations of tall concrete faced rockfill dams in narrow canyons

Longitudinal vibrations of concrete-faced rockfill dams may cause significant compressive stresses and joint openings in the slab panels. The behavior of such dams subjected to longitudinal and vertical vibrations is investigated, based on numerical simulation of the staged construction, reservoir impoundment and seismic shaking. The static analysis uses a hyperbolic model for the rockfill, whereas the seismic analysis uses a nonlinear hysteretic model which accounts for the dynamic properties. A damage plasticity model is used for the reinforced concrete and frictional contact behavior is considered at the base and vertical sides of the concrete panels. The seismic analysis takes into account the flexibility of the canyon rock and potential dynamic rockfill settlements. An existing 150 m–high dam is used to investigate the effect of longitudinal vibrations on the compressive stresses near the slab-to-slab vertical interfaces and the opening of the joints. The effect of dynamic settlements is examined and comparisons are made to the response from upstream/downstream and combined vibrations. The effectiveness of introducing 5 cm-wide cuts at selected vertical joints to reduce slab compression in existing CFRDs is demonstrated. The presented results offer useful insight into the effect of longitudinal vibrations on the seismic behavior of CFRDs.     

Overview of the seismic input at dam sites in China

The current Chinese national standard, the Standard for Seismic Design of Hydraulic Structures (GB51247), released in 2018, is strictly based on China’s national conditions and dam engineering features. A comprehensive and systematic overview of the basis of the seismic fortification requirements, the framework of the fortification criteria, and the mechanisms of seismic input related to the seismic design of dams are presented herein. We first analyzed and clarified several conceptual aspects in traditional seismic design of dams. Then, for the seismic input at the dam site described in the first national standard for hydraulic structures, we expounded innovative concepts, ideas, and methods to make relevant provisions more realistic and practical and discussed whether reservoir earthquakes must be included in the seismic fortification framework of dams. This study seeks to incorporate seismic input at the dam site into traditional seismic design practice to promote its improvement from the quasi-static method to the dynamic method and from the closed vibration system to an open wave propagation system, to ensure that the seismic design of dams becomes more reasonable, reliable, scientific, and economic.     

软土隧道基于地震响应的输入地震动排序

为探讨“最不利地震动”概念在地下结构抗震设计中的适用性,以软土地铁区间隧道为对象建立相应的地层-结构动力分析模型。以直径变形率为分析指标,基于动力时程方法研究18条不同输入地震动作用下隧道结构动力响应的分布及差异性,得出基于隧道地震响应的输入地震动排序,并通过调幅手段对比分析了地面峰值加速度（PGA）和隧道埋深变化对隧道结构地震动响应排序的影响规律。最后,评价了不同输入地震动参数,包括峰值加速度、峰值速度、峰值位移、绝对累积速度（CAV）和阿里亚斯（Arias）强度（I_A）与隧道地震响应之间的相关性。分析结果表明:① 随着PGA从0.5 m/s2增加到2 m/s2,地震动排序发生明显变化,并且不同输入地震动引起的隧道地震响应差异显著提高,最不利地震动引起的直径变形率与平均值的比值从1.1增加到1.9;② 隧道从浅埋到深埋的过程中,地震动排序结果基本保持不变;③ PGA为2 m/s2时,隧道地震响应与基岩面峰值速度（PBV）的相关性最好,相关系数达到0.94,其次是与基岩面峰值位移（PBD）和I_A,相关系数分别为0.62和0.48,相关性最差的是基岩面峰值加速度（PBA）和CAV,相关系数仅为0.37和0.22。研究结论可为今后软土隧道的输入地震动选择提供科学依据。      

拱坝非线性地震反应分析

本文根据一致粘弹性模型的概念，引入应变率的影响，将混凝土静态William-Warnke三参数模型改造成一致粘塑性William-Warnke三参数本构模型，并用这个模型对某高拱坝进行了非线性地震响应分析，与线弹性模型和应变率无关的William-Warnke三参数模型的结果进行了比较，初步探讨了应变率对拱坝地震反应的影响。