共查询到20条相似文献，搜索用时 51 毫秒
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本文通过成层状地基地震动输入计算方法得到覆盖层边界自由场运动,采用粘弹性边界,考虑地基辐射阻尼效应及坝体和地基的接触非线性,针对强震区深厚覆盖层场地重力坝开展线性和非线性动力时程分析研究,结合需求能力比DCR评估其抗震性能。由线弹性动力时程分析可知,在运行基准地震OBE作用下,重力坝坝体应力均在允许范围内,其抗滑稳定安全系数不能满足要求;由非线性动力分析可知,在OBE和最大设计地震MDE作用下,重力坝发生较大滑动位移。通过在重力坝坝体下游坝后回填土加强重力坝抗震稳定性,结果表明,下游坝后回填土可有效减小坝体滑动位移,加强其抗震稳定性。本文针对深厚覆盖层场地重力坝开展的抗震安全研究为抗震设计提供了科学依据,为强震区深厚覆盖层场地重力坝的抗震分析提供参考。 相似文献
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基于非线性指数型动接触本构模型,对实际键槽模型进行简化处理。采用的本构模型可以考虑缝面的开合非线性以及横缝键槽的咬合作用。采用点-面接触模型模拟横缝的非线性动接触行为,精细研究了缝面开度、径向位移的变化及其对坝体应力状态的影响,并与平缝结果进行了比较。以一座拟建的混凝土重力拱坝,探讨了横缝及其诱导缝对大坝工作性态的影响,并对横缝键槽的影响进行了综合分析。研究表明,横缝的径向滑移量要远大于开度,当考虑诱导缝时,由于大坝整体性受到削弱,横缝开度变大;考虑键槽效应后,径向滑移效应大幅减小,而法向开度增大,坝踵处的主拉应力以及拱冠梁顶处的拱向拉应力的最大值均变大。 相似文献
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考虑流固耦合效应的辽宁葠窝水库溢流坝段抗震性能分析 总被引：1，自引：0，他引：1
针对辽宁葠窝水库混凝土重力坝抗震问题,采用耦合的拉格朗日-欧拉有限元分析技术,建立了可考虑库水-坝体-基岩动力耦合效应的典型溢流坝段抗震分析数值模型。模型中,采用等效一致粘弹性边界模拟基岩的人工截断边界;采用混凝土弥散裂缝本构模型模拟混凝土的动力特性。根据烈度与地震动之间的关系,确定了水库坝体抗震设计的输入加速度峰值。据此,分析了在不同季节水位变化条件下坝体地震反应的基本特性。研究表明：完好的辽宁葠窝水库混凝土重力坝溢流坝段能满足8度的抗震设防烈度要求。地震下溢流坝段峰值位移出现在胖坝和瘦坝的坝顶迎水面位置处,胖坝的动位移较瘦坝动位移大。胖坝在闸墩与溢流堰交接处出现了拉应力最大值。有库水条件下,瘦坝峰值拉应力出现在坝趾处,无库水条件下,瘦坝最大拉应力出现在溢流堰与闸墩交接处。 相似文献
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为了研究混凝土重力坝在地震动荷载作用下的潜在失效模式,以金安桥碾压混凝土重力坝5号非溢流坝段为例,运用粘弹性边界法和流固耦合法建立了反映重力坝在地震动作用下动力响应特征的坝体-地基-库水抗震分析模型。基于增量动力分析（IDA）法:绘制了以相对位移转角为x轴（损伤指标,DM）和峰值地面加速度为y轴（强度指标,IM）的IDA曲线簇;分析了金安桥大坝在极端荷载作用下的潜在失效模式和其在不同峰值地面加速度下重力坝的损伤破坏过程。结果表明:金安桥大坝在地震动荷载作用下,可能发生功能失效的地方多出现在坝体折坡处、碾压分区交界处、坝踵与坝基交界处、廊道顶等应力集中处。因此,加强对这些区域的抗震防护有利于提高大坝整体的抗震水平。 相似文献
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Adrian E. Scheidegger 《Surveys in Geophysics》1985,7(3):259-271
This brief review demonstrates the significance, on a global scale, of joints as shearing surfaces in the neotectonic stress field. Thus, the principal directions of the neotectonic stress field can be determined by a statistical treatment of joint orientation data. These principal stress directions agree with those postulated from plate tectonic theory in every case, on five continents. 相似文献
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J. C. Jaeger 《Pure and Applied Geophysics》1959,43(1):148-158
Summary The conditions for sliding over artificial joint surfaces have been studied experimentally by cutting rock cylinders at various angles to their axes and studying slip over these surfaces in a triaxial testing apparatus. The types of joint used were: (i) filled with plaster to simulate a soft joint filling, (ii) bare surfaces ground approximately flat, and (iii) natural surfaces across which shear failure had taken place. The results agreed reasonably well with the simple theory for a constant coefficient of friction. Measured coefficients of friction lie in the range 0.5–0.8 and differ by surprisingly little between the various surfaces. The surfaces across which sliding has taken place exhibit interesting slickenside phenomena. Subsidiary failures frequently occur which cut across the joint surfaces. 相似文献
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The paper proposes an alternative method for the earthquake-resistant design of HDC external beam-column joints which is based
on the assumption that the load transferred from the beam and column elements to the joint is predominantly resisted by a
diagonal strut mechanism. The validity of the proposed method is verified experimentally through a comparative study of the
behaviour of seven full-size beam-column joint sub-assemblages—three of them designed in compliance with the current European
Codes and four in accordance with the proposed method—under cyclic loading. The results obtained indicate that, in contrast
with the specimens designed in compliance with current code provisions, those designed so as to comply with the proposed specifications
fully satisfy the code performance requirements. 相似文献
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The behavior of bridge monolithic connections is modeled using a simplified mathematical model that accounts for stress equilibrium,
compatibility of deformations, and the state of bond of longitudinal column bars anchored through the joint panel. In this
regard, a stress gradient factor is introduced, to model the profile of bar stresses along the anchorage. To establish this
factor, two independent mechanisms of stress transfer are considered: a bond mechanism between the anchored bars and the surrounding
concrete and a friction mechanism between the anchored bars and the transverse bars that enclose and restrain the anchorages.
The model is used for calculation of the shear stress–shear strain relationship of all tests found in the international literature
on bridge monolithic connections that showed shear type of failure under simulated seismic loading. Joint strength values
calculated with the proposed model are compared with the experimental results. Based on this comparison the proposed model
is verified for use in interpretation of bridge monolithic connection behavior and design. 相似文献
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Sara Casciati 《地震工程与工程振动(英文版)》2007,6(3):259-268
The joints connecting vertical and horizontal elements are the "weak link" in structural systems assembled from wood panels. If they are too weak, local failures may occur, resulting in performance that is significantly below expectations. If they are too resistant, the joints may be unable to dissipate energy during vibrations, thus possibly initiating a fast progressive failure. This paper re-processes and re-elaborates the results of shaking table tests previously carried out by the author and other co-workers. The goal is to assess the feasibility of a joint which is able to dissipate energy during vibration, without degrading the connection performance. 相似文献
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We have found some mistakes in the article by Sara Casciati(2007).The revisions are given below:
1.The last sentence of the first paragraph in p.262 "(Casciati and Faravelli,2007)" should be changed to "(Casciati and Faravelli,1991)". 相似文献
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传统抗弯钢框架的梁柱节点通常设计为刚性连接,这种刚性节点具有很大的抗弯刚度,然而节点延性不足,罕遇地震作用导致节点脆性断裂。研究学者提出了多种解决该问题的思路,例如半刚性连接节点、节点加强或削弱方法使塑性铰外移等。本文提出了一种简化的梁柱节点连接方式-铰接连接,改变梁柱节点的传力方式,在节点处设置隅撑提供框架的抗侧刚度,控制结构的失效模式。本文设计了三组抗弯钢框架和铰接隅撑钢框架,分别为3层、5层和8层结构,通过Pushover分析和非线性动力时程分析,对比二者之间的承载力、刚度、延性和层间侧移等抗震性能。研究结果表明:铰接隅撑钢框架具有和传统抗弯钢框架相似的抗侧刚度,且承载能力略高。罕遇地震作用下,铰接隅撑钢框架的层间侧移较小。传统抗弯钢框架失效模式为梁端出现塑性铰,而铰接隅撑钢框架的塑性区域转移至隅撑与梁连接部位。 相似文献
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An aspect of seismic design of bridges that has hardly received proper attention so far is the appropriate selection of joint gaps. End gaps define the boundary conditions of the bridge and affect its dynamic response; their proper design can lead to an improved structural performance under dynamic actions. The idea of the ‘Dynamic Intelligent Bridge’ is explored here, wherein current bridge joints that have a fixed width are substituted by variable-width joints and, under seismic loading, the joint gap is optimised either with a one-off adjustment, or continuously (in real time) through semi-active control. In all cases, a novel device is used that permits this improved behaviour of the joints, the moveable shear key (MSK), a device for blocking the movement of the bridge deck, which has the possibility to slide, hence varying the size of the existing joint gap. In this context, the effect of gap size on the seismic response of bridges is assessed herein and a methodology is put forward for optimising this size, using a number of criteria such as maintaining the functionality of the bridge for moderate earthquakes, and ensuring the safety of the bridge and its users under earthquakes stronger than that used for design. 相似文献