共查询到20条相似文献，搜索用时 93 毫秒
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《华南地震》2016,(4)
新丰江水库大坝是世界上第一座经受六级地震考验的超百米高混凝土大坝,并且至今库区周围仍然有地震不断发生,因此对其进行抗震分析十分必要。首先利用大坝强震动台阵的监测数据进行模态分析,然后结合模态分析结果建立大坝典型引水坝段ANSYS有限元模型并对其进行静力和动力分析,探讨坝体的变形和应力分布规律。结果表明:大坝模态频率与水位负相关;大坝在地震作用下,上游坝面突变处出现最大拉应力,这一现象与挡水坝段上游坝面突变处出现贯穿裂缝的破坏结果是一致的,应当引起一定重视,静力作用和地震作用下其他部位均有一定的安全储备;动力时程分析结果与反应谱分析结果相比,前者更加偏于安全。 相似文献
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研究黄土丘陵河谷场地在地震作用下强地面运动特征的变化情况,可以揭示强震对该类场地上震害的触发机理。结合黄土高原的地貌特征,建立具有代表性的动力数值分析模型,通过输入不同幅值、频谱特性和持续时间的地震波,对起伏地形和覆盖黄土层共同影响下的黄土河谷场地进行地震反应分析。结果表明:黄土层和地形耦合作用控制了地表的PGA变化,使其趋于复杂,在同一输入波不同振幅作用下,与基岩河谷各测点相比,黄土覆盖河谷场地的地震动频谱幅值均有所增加,并且频谱主峰均向高频移动。在不同地震波输入下,场地不同部位的固有频率受地形高程和土层影响;而地震动大小和频谱幅值不仅与场地的基本频谱和地形起伏有关,也与输入地震波的频谱成分相关。输入波PGA与地震频谱特征都不变时,同一场地输出的地震频谱形状具有相似的特征,随着地震持时增长,能量向场地基本频率附近集中,从而可能导致场地上相应频率建筑物震动幅值增加,造成累积破坏。 相似文献
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基于ANSYS有限元分析软件,在模态分析基础上,采用等效静力法对调节阀的抗震性能进行分析,分析了调节阀在开启和关闭状态下对SL1(运行安全地震动)的应力响应,并分析了调节阀在开启状态下对SL2(安全停堆地震动)的应力响应,分析得知支架拐角、阀盖-中法兰连接的弯角处和阀体中腔为薄弱部位,其最大应力值均小于许用应力。对调节阀分别进行两次SL1地震和一次SL2地震试验,测定调节阀的自振频率、阻尼等振动参数和加速度、应力等地震响应参数,试验结果表明调节阀具有足够的刚度和强度,满足抗震设计强度要求。试验结果与有限元分析结果对比,误差小于10%。 相似文献
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乐昌峡大坝位于广东省韶关市乐昌市境内,建造时按照Ⅴ度区进行抗震设计,随着2016年第五代地震动参数区划图的实施,该区设防烈度提高为Ⅵ度,大坝在Ⅵ度地震影响下是否安全需要进行分析.利用图纸资料建立了大坝的三维有限元模型,计算分析了多水位下特征坝段的频率和大坝的地震响应,结果表明:溢流坝段的频率小于两岸挡水坝段.地震作用下,大坝位移最大值出现在坝顶处,应力最大处出现在闸墩、牛腿及坝踵处,但均处于安全范围,证明大坝抗震性能良好;库水水位会显著影响大坝的频率及地震响应,在抗震设计时,应引起注意. 相似文献
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《地震工程与工程振动》2015,(6)
通过直接拉伸试验和劈拉试验研究仿真混凝土材料动态受拉特性,为混凝土坝动力模型试验提供相关材料参数,研究其与原型混凝土材料的匹配问题。在应变速率10-5/s至10-1.08/s范围内对试件进行拉伸试验研究,给出拉伸曲线方程,并分别对仿真材料的强度、峰值应力处应变、弹性模量给出考虑率相关的经验公式,分析泊松比、吸能能力、破坏形态与应变速率的关系。通过与混凝土动态拉伸特性以及破坏形态对比,得出结论:仿真混凝土材料适合模型动力试验;其动态拉伸特性和混凝土材料表现出一定的相似性,但极限拉伸强度和吸能能力等方面率相关性更明显,在进行模型与原型的相似关系设计以及高坝模型动力破坏试验分析时,需充分考虑仿真材料的率相关特性以得到合理的高坝模型试验结论。 相似文献
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针对隧道的抗震安全性,借助有限元软件平台对其地震时程响应进行非线性有限元分析。利用弹性模型考虑混凝土隧道在循环荷载作用下的拉、压应力-应变关系,同时对土体采用MohrCoulomb模型,选用人工边界作为边界条件,以人工合成的多点地震加速度时程作为地震动输入,分别考虑一致输入、行波效应、相干效应及行波加相干效应对隧道的影响。分析结果表明,与一致激励的计算结果相比,非一致地震激励会显著增加隧道结构的内力和位移响应,从而对隧道抗震产生不利影响。研究结论可为长隧道结构的抗震设计和分析提供科学依据。 相似文献
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Chen Houqun 《地震工程与工程振动(英文版)》2014,(Z1)
China is a country of high seismicity with many hydropower resources. Recently,a series of high arch dams have either been completed or are being constructed in seismic regions,of which most are concrete dams. The evaluation of seismic safety often becomes a critical problem in dam design. In this paper,a brief introduction to major progress in the research on seismic aspects of large concrete dams,conducted mainly at the Institute of Water Resources and Hydropower Research(IWHR) during the past 60 years,is presented. The dam site-specific ground motion input,improved response analysis,dynamic model test verification,field experiment investigations,dynamic behavior of dam concrete,and seismic monitoring and observation are described. Methods to prevent collapse of high concrete dams under maximum credible earthquakes are discussed. 相似文献
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In this paper a rate-dependent isotropic damage model developed for the numerical analysis of concrete dams subjected to seismic excitation is presented. The model is shown to incorporate two features essential for seismic analysis: stiffness degradation and stiffness recovery upon load reversals and strain-rate sensitivity. The issue of mesh objectivity is addressed using the concept of the ‘characteristic length’ of the fracture zone, to show that both the softening modulus and the fluidity parameter must depend on it to provide consistent results as the computational mesh is refined. Some aspects of the numerical implementation of the model are also treated, to show that the model can be easily incorporated in any standard non-linear finite element code. The application of the proposed model to the seismic analysis of a large gravity concrete dam shows that the structural response may vary significantly in terms of the development of damage. The inclusion of rate sensitivity is able to reproduce the experimental observation that the tensile peak strength of concrete can be increased up to 50 percent for the range of strain rates that appear in a structural safety analysis of a dam subjected to severe seismic actions. 相似文献
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Earthquake safety assessment of concrete arch and gravity dams 总被引：9，自引：1，他引：8
Based on research studies currently being carried out at Dalian University of Technology, some important aspects for the earthquake safety assessment of concrete dams are reviewed and discussed. First, the rate-dependent behavior of concrete subjected to earthquake loading is examined, emphasizing the properties of concrete under cyclic and biaxial loading conditions. Second, a modified four-parameter Hsieh-Ting-Chen viscoplastic consistency model is developed to simulate the rate-dependent behavior of concrete. The earthquake response of a 278m high arch dam is analyzed, and the results show that the strain-rate effects become noticeable in the inelastic range. Third, a more accurate non-smooth Newton algorithm for the solution of three-dimensional frictional contact problems is developed to study the joint opening effects of arch dams during strong earthquakes. Such effects on two nearly 300m high arch dams have been studied. It was found that the canyon shape has great influence on the magnitude and distribution of the joint opening along the dam axis. Fourth, the scaled boundary finite element method presented by Song and Wolf is employed to study the dam-reservoir-foundation interaction effects of concrete dams. Particular emphases were placed on the variation of foundation stiffness and the anisotropic behavior of the foundation material on the dynamic response of concrete dams. Finally, nonlinear modeling of concrete to study the damage evolution of concrete dams during strong earthquakes is discussed. An elastic-damage mechanics approach for damage prediction of concrete gravity dams is described as an example. These findings are helpful in understanding the dynamic behavior of concrete dams and promoting the improvement of seismic safety assessment methods. 相似文献
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Concrete dams suffering from alkali-aggregate reaction (AAR) exhibit swelling and deterioration of concrete or even cracking over a long period. The deterioration of concrete may significantly affect the dynamic behavior of the structures, and it is necessary to estimate seismic safety of the deteriorated dams subjected to strong earthquakes. A unified approach is presented in this paper for long-term behavior and seismic response analysis of AAR-affected concrete dams by combining AAR kinetics, effects of creep and plastic-damage model in the finite element method. The proposed method is applied to a gravity dam and an arch dam. The long-term behavior of the AAR-affected dams is first predicted in terms of anisotropic swelling, spatially non-uniform deterioration of concrete, and cracking initiation and propagation with the development of AAR. The seismic response of the deteriorated dams is subsequently analyzed based on the state of the structures at the end of the long-term analysis. The AAR-induced expansion displacements obtained from the proposed method are in good agreement with the measured ones in the long-term operation. The simulated cracking patterns in the dams caused by the continuing AAR are also similar to the field observation. The results from the seismic analysis show that AAR-induced deterioration of concrete and cracking may lead to more severe damage cracking in the dams during earthquake. The dynamic displacements are also increased compared with the dams that are not suffering from AAR. The seismic safety of the AAR-affected concrete dams is significantly reduced because of the AAR-induced deterioration of concrete and cracking. 相似文献
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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。 相似文献
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Uncertainties in structural engineering are often arising from the modeling assumptions and errors, or from variability in input loadings. A practical approach for dealing with them is to perform sensitivity and uncertainty analysis in the framework of stochastic and probabilistic methods. These analyses can be statically and dynamically performed through nonlinear static pushover and IDA techniques, respectively. Of the existing structures, concrete gravity dams are infrastructures which may encounter many uncertainties. In this research, probabilistic analysis of the seismic performance of gravity dams is presented. The main characteristics of the nonlinear tensile behavior of mass concrete, along with the intensity of earthquake excitations are considered as random variables in the probabilistic analysis. Using the tallest non‐overflow monolith of the Pine Flat gravity dam as a case study, its response under static and dynamic situations is reliably examined utilizing different combinations of parameters in the material and the seismic loading. The sensitivity analysis reveals the relative importance of each parameter independently. It will be shown that the undamaged modulus of elasticity and tensile strength of mass concrete have more significant roles on the seismic resistance of the dam than the ultimate inelastic tensile strain. In order to propagate the parametric uncertainty to the actual seismic performance of the dam, probabilistic simulation methods such as Monte Carlo simulation with Latin hypercube sampling, and approximate moment estimation techniques will be used. The final results illustrate the possibility of using a mean‐parameter dam model to estimate the mean seismic performance of the dam. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Based on the consistency-viscoplastic constitutive model,the static William-Warnke model with three-parameters is modified and a consistency-viscoplastic William-Warnke model with three-parameters is developed that considers the effect of strain rates. Then,the tangent modulus of the consistency viscoplastic model is introduced and an implicit backward Elure iterative algorithm is developed. Comparisons between the numerical simulations and experimental data show that the consistency model properly provides the uniaxial and biaxial dynamic behaviors of concrete. To study the effect of strain rates on the dynamic response of concrete structures,the proposed model is used in the analysis of the dynamic response of a simply-supported beam and the results show that the strain rate has a significant effect on the displacement and stress magnitudes and distributions. Finally,the seismic responses of a 278 m high arch dam are obtained and compared by using the linear elastic model,as well as rate-independent and rate-dependent William-Warnke three-parameter models. The results indicate that the strain rate affects the first principal stresses,and the maximal equivalent viscoplastic strain rate of the arch dam. Numerical calculations and analyses reveal that considering the strain rate is important in the safety assessments of arch dams located in seismically active areas. 相似文献
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In this paper a general methodology for the analysis of large concrete dams subjected to seismic excitation is outlined. It is valid both for gravity dams (2D representation) and arch dams (3D representation). The method allows for non-linear material behaviour of the dam, ‘transparent fictitious boundaries’ for dealing properly with in-coming and out-going seismic waves, and an efficient procedure to deal with dam-soil-fluid interaction. The mechanical behaviour of concrete is modelled using an isotropic damage model which allows for tension and compression damage, and exhibits stiffness recovery upon load reversals. Emphasis is placed in the treatment of fluid-structure interaction, regarding both formulation and efficiency aspects. A gravity dam and an arch dam are analysed subjected to artificially generated earthquakes of different intensities, and the results are used to study the degree of (un)safety of the dams. 相似文献
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There are several alternatives to evaluate seismic damage‐cracking behavior of concrete arch dams, among which damage theory is the most popular. A more recent option introduced for this purpose is plastic–damage (PD) approach. In this study, a special finite element program coded in 3‐D space is developed on the basis of a well‐established PD model successfully applied to gravity dams in 2‐D plane stress state. The model originally proposed by Lee and Fenves in 1998 relies on isotropic damaged elasticity in combination with isotropic tensile and compressive plasticity to capture inelastic behaviors of concrete in cyclic or dynamic loadings. The present implementation is based on the rate‐dependent version of the model, including large crack opening/closing possibilities. Moreover, with utilizing the Hilber–Hughes–Taylor time integration scheme, an incremental–iterative solution strategy is detailed for the coupled dam–reservoir equations while the damage–dependent damping stress is included. The program is initially validated, and then, it is employed for the main analyses of the Koyna gravity dam in a 3‐D modeling as well as a typical concrete arch dam. The former is a major verification for the further examination on the arch dam. The application of the PD model to an arch dam is more challenging because the governing stress condition is multiaxial, causing shear damage to become more important than uniaxial states dominated in gravity dams. In fact, the softening and strength loss in compression for the damaged regions under multiaxial cyclic loadings affect its seismic safety. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Parallel computation of seismic analysis of high arch dam 总被引：1，自引：1，他引：0
Parallel computation programs are developed for three-dimensional meso-mechanics analysis of fully-graded dam concrete and seismic response analysis of high arch dams （ADs）, based on the Parallel Finite Element Program Generator （PFEPG）. The computational algorithms of the numerical simulation of the meso-structure of concrete specimens were studied. Taking into account damage evolution, static preload, strain rate effect, and the heterogeneity of the meso-structure of dam concrete, the fracture processes of damage evolution and configuration of the cracks can be directly simulated. In the seismic response analysis of ADs, all the following factors are involved, such as the nonlinear contact due to the opening and slipping of the contraction joints, energy dispersion of the far-field foundation, dynamic interactions of the dam-foundation- reservoir system, and the combining effects of seismic action with all static loads. The correctness, reliability and efficiency of the two parallel computational programs are verified with practical illustrations. 相似文献