共查询到19条相似文献，搜索用时 156 毫秒
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土石坝振动台模型试验颗粒流数值模拟分析 总被引：2，自引：0，他引：2
目前一般采用振动台试验、离心振动台试验和有限元动力分析来获得土石坝在设计地震荷载作用下的形态和抗震性能。本文结合孔宪京等的土石坝振动台试验结果开展了颗粒流细观数值模拟研究,克服了传统连续介质力学的宏观连续性假设,形象而直观地表现出坝体在动力荷载作用下的破坏特征。数值模拟规律与振动台试验规律基本一致。同时还分析了坝体颗粒粘结强度和地震峰值加速度变化对坝体破坏特征的影响。数值结果表明,当颗粒间粘结强度较低时,表现为坝体表面颗粒的滑动破坏,粘结强度稍大时,会出现局部的小块颗粒团整体滑动破坏;随着峰值加速度的增大,坝顶沉降量在增大,坝体破坏特征不变。 相似文献
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土石坝由于施工便捷、取材方便,是目前我国西部比较常见的一种坝型。但西部地区地震活动频繁且烈度较高,特别是一些土石坝坝基下存在深厚覆盖层,对土石坝的地震动力响应有重要影响。采用黏弹性模型-等效线性化方法对国内某拟建土石坝进行三维动力响应分析。考虑到实际土石坝坝体是不完全排水的,将根据经验公式得到的残余体变分成两部分,一部分转化为残余孔压,另一部分为产生的残余变形。根据有限元计算结果,分析在坝基深厚覆盖层影响下坝体残余变形、加速度响应、残余孔压等动力反应的特征和分布规律。计算结果符合一般规律,说明本文采用的计算方法适用于含深厚覆盖层心墙堆石坝的静动力分析。 相似文献
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爆炸荷载作用下钢柱的动力响应与影响因素分析 总被引：4，自引：0，他引：4
采用有限元软件ANSYS/LS-DYNA,建立钢柱有限元模型,模拟爆炸荷载作用下钢柱的动力响应,并对影响钢柱动力响应的主要因素进行数值分析。考虑了不同爆炸荷载、材料失效应变、单元网格密度、柱高、柱截面尺寸和柱承担的轴向压力等参数的影响。通过对钢柱动力响应时程曲线进行分析,研究爆炸荷载作用下钢柱响应特性及其破坏机理;通过分析,得到各参数对其动力响应的影响规律。分析结果表明：增大柱的截面尺寸,能够降低柱跨中水平位移;增大柱截面高度,能有效地提高钢框架柱的抗爆承载力;在钢柱抗爆设计中,应控制其所承受的轴向压力大小,轴压比值不宜超过0.3。 相似文献
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在GSA标准分析法基础上提出两阶段分析法,采用ANSYS/LS-DYNA建立了一个7层底框砌体结构的三维有限元模型,对爆炸荷载作用下底框砌体结构连续倒塌过程进行模拟。根据爆炸荷载引起的结构局部性破坏,对局部采取适当的防爆抗爆措施防止结构的连续倒塌。通过改变砌体材料的强度等级、纵向配筋率、粘贴玻璃纤维复合材料、粘贴钢板、柱网尺寸、墙体开洞以及底框层数,得到底框砌体结构在爆炸荷载作用下的响应规律和破坏情况以及结构墙体中砌体材料、钢筋的应力和位移随时间的变化规律,为底框砌体结构的防爆设计提供理论基础和有价值的参考数据。 相似文献
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《地震工程与工程振动》2015,(1)
船舶撞击荷载作用下高桩码头结构的动力放大效应不可忽略。采用数学理论推导与动力时程仿真计算相结合的方式,对靠泊船舶撞击作用下高桩码头结构的动力响应及动力放大效应进行了研究,获得了多自由度结构在单点撞击荷载作用下的动力响应公式及相应的动力放大系数公式,推荐了数值计算时船舶撞击荷载的时程曲线类型及持时,获取了船舶靠泊撞击荷载下考虑桩-土相互作用的高桩码头结构动力放大效应规律,明确了桩-土相互作用对放大效应的影响。计算与分析结果表明:船舶靠泊撞击荷载的时程曲线可近似为持时1.0 s的半正弦曲线;在靠泊船舶撞击荷载作用下考虑桩-土相互作用的软基上的高桩码头结构对撞击荷载的动力放大系数在2.0左右;不考虑桩-土相互作用的计算结果偏于不安全,建议在进行软土地基上高桩码头结构的动力响应计算时应避免采用假想嵌固点法;以上结论可为码头结构设计时船舶撞击荷载的合理取值与模型有限元计算提供理论依据。 相似文献
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采用理想化的压力—时间曲线模拟爆炸冲击荷载,压力—时间曲线为简化的三角形荷载形式。考虑应变率效应对钢材的影响,应用LS-DYNA有限元分析软件,对导管架海洋平台在爆炸冲击荷载作用下的动力响应进行数值模拟和分析,得到了不同峰值爆炸荷载作用下,海洋平台结构上层甲板、中层甲板和立面结构重要节点的动力响应时程曲线。结果表明：上层甲板和中层甲板节点竖向位移的绝对值随着爆炸荷载峰值压力的增大而增大,当爆炸荷载峰值压力为20～70kPa时,节点区域内均处于弹性状态,当爆炸荷载峰值压力为80kPa时,节点区域内进入了塑性状态。立面平台节点的水平位移随着爆炸荷载峰值压力的增大而增大,当爆炸荷载峰值压力为20～80kPa时,节点区域内进入塑性状态。 相似文献
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5·12汶川8.0级大地震对德阳市罗江县的水库造成了不同程度的破坏,经济损失严重,若水库出现渍坝现象,将会带来更大的损失。对罗江县19座高危以上险情水库的土坝震害进行了调查研究.发现典型的震害现象包括裂缝、渗漏、防浪墙损坏以及泄水建筑物和附属设施的损毁等。根据水库土坝的震前病害调查资料可以看出：水库土坝在地震前多是带病运行,严重影响地震时水库运行的因素主要有土料或填筑质量差、坝基问题、坝体结构设计不当、蚁害、观测设施不全等。依据震后水库土坝的破坏形态,分析了水库大坝的震前病害对大坝震害现象的影响。为今后水库土坝的抗震设计提供基础性的资料。 相似文献
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Conventional numeric simulations of rock-fill dams are generally performed finite element method (FEM), in which the rock-fill body is treated as continuum material. But the rock-fill body possesses strong discontinuity and FEM based on continuum idealization cannot simulate its failure process. The discontinuous deformation analysis (DDA) method is just the right tool of solving this problem satisfactorily. In this paper, two kinds of model dams, i.e. homogeneous rock-fill dam and concrete-faced rock-fill dam, are simulated using DDA method, their characteristics of response and failure process are presented. The results from numerical simulations are consistent with those from the author's previous dynamic experiments. 相似文献
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爆炸荷载作用下方钢管混凝土柱的动力响应及破坏机理 总被引：3，自引：0，他引：3
方钢管混凝土柱是被广泛采用的组合构件之一。爆炸发生时产生的爆炸冲击波可能会对框架结构内部的方钢管混凝土柱造成严重破坏,然而目前对其动力响应及破坏机理的研究成果相对较少。本文采用有限元分析软件ANSYS/LS-DYNA对爆炸荷载作用下方钢管混凝土柱的动力响应和破坏机理进行了研究分析。建立了方钢管混凝土柱实体有限元模型,其中混凝土采用HJC模型,方钢管采用考虑应变率的塑性随动强化模型,爆炸荷载施加在柱子一侧表面。通过对方钢管混凝土柱的破坏过程的模拟,比较分析了其在不同＂比例距离＂下的动力响应和破坏形式,进而得出方钢管混凝土柱的破坏机理。在爆炸荷载作用下,方钢管对其核心混凝土有一定的约束作用,使其处于复杂应力状态之下,从而使混凝土强度得以提高,塑性和韧性同时得到改善;同时,由于混凝土的存在,延缓了方钢管柱底和柱顶过早地发生局部屈曲。随着＂比例距离＂的增大,柱中水平位移逐渐减小。结果表明,方钢管混凝土柱具有良好的延性、优越的抗爆性能,所提出的破坏机理可供结构抗爆设计的进一步研究参考。 相似文献
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Earthquake induced liquefaction continues to be a major threat to many engineered structures around the world. Analysis of liquefaction becomes particularly difficult for two-dimensional (and 3D) problems such as dam/foundation systems. Predominantly, analyses for such systems are performed utilizing some type of finite element or finite difference procedure. Verification or validation of the analyses relies on very limited field performance data with reduced knowledge of the full scope of system conditions or loading conditions.Research reported in this paper represents a portion of ongoing work to obtain a database of information useful for numerical model calibration and to gain a better understanding of the complex dynamics of liquefying foundations under earth dams. Specifically, a highly instrumented model of an earth dam with clay core founded on a liquefiable foundation subjected to earthquake loading is being studied. Properties of the liquefiable foundation are varied to determine the related effects on the overlying earth dam. In this paper, results from three centrifuge physical models will be presented. The models are identical, with the exception of the location (depth) of a liquefiable layer in the foundation, and are subjected to the same dynamic excitation. Results and discussion related to the significance of the liquefiable layer location within the foundation and damage to the earth dam are presented. 相似文献
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The investigation on the seismic behavior of dams becomes crucial but is limited to lack of experimental or field data. This paper aims to experimentally simulate two major dam types of earth-core rock-fill dam and concrete-faced rock-fill dam by dynamic centrifuge tests to investigate the seismic response of the dam. A series of staged centrifuge tests was performed by applying real earthquake records from 0.05 to 0.5g. The distributions of amplification ratio differed depending on the magnitude of earthquake loading and the zoning condition. The amplification ratio at the crest increased in the bedrock acceleration that exceeds 0.3g and strongly influenced by the loosening behavior of the upper part. The residual settlements and horizontal displacement at the dam crest were small. Shallow surface sliding was dominant failure. The maximum tensile stress on the face slab by dynamic loading occurred at a height of around 4/5 near the upstream water level. Finally, two-dimensional numerical simulations were performed in an effort to simulate the centrifuge models. The centrifuge tests and numerical analysis obtained mostly comparable results, thus confirming that centrifuge modeling reasonably simulates the seismic behavior of dams. 相似文献
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调查、搜集和研究了汶川地震中被评定为高危以上险情的147座小型水库土坝的地震破坏情况,给出了高危以上险情土坝的地震破坏程度划分为中等破坏、严重破坏和极严重破坏三个等级的原则和标准,以及土坝的地震破坏程度与地震烈度、土坝的宽高比、上游坡比、坝高的经验关系表,可发现:土坝的几何形状对其破坏程度起着重要的作用;对于6～8度地震烈度区,土坝的宽高比越小,或上游坡比越小,或坝体越高,则土坝的破坏程度越严重;对于9度以上地震烈度区,土坝通常发生极严重破坏。依据高危以上险情土坝的地震反应分析结果,给出了土坝地震破坏程度与土坝宽高比、坝高、土坝上游坡比及坝顶加速度放大系数、坝体最大动剪应力的经验关系曲线,发现在相同的地震烈度水平下,土坝的宽高比越小,或上游坡比越小,或坝高越大,且坝顶加速度放大系数越大或坝体最大动剪应力越大,则其地震破坏程度越严重;坝体最大动剪应力超过30kPa的土坝,通常发生严重或极严重破坏,坝体最大动剪应力大于100kPa的土坝,通常发生极严重破坏;土坝离发震断层越远,则其坝顶加速度放大系数越大。本文给出的高危以上险情土坝的地震破坏程度与坝体几何形状的经验关系,可为今后土坝抗震设计提供参考依据。 相似文献
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A simplified analysis procedure for the non-linear hysteretic earthquake-response of earth dams is presented. The dam is modelled as a one-dimensional hysteretic shear-wedge subjected to base excitation. The hysteretic stress-strain behaviour of the dam materials is modelled by using elasto-plastic constitutive equations based on multi-surface kinematic plasticity theory. The method is based on a Galerkin formulation of the equations of motion in which the solution is expanded using eigenmodes of the linearized problem defined over the spatial domain occupied by the dam. The technique is applied to analyse the non-linear dynamic response of an earth dam subject to two very different input ground motions. The following investigations are presented: (i) comparison between the results obtained using two soil models depicting different nonlinear properties, (ii) comparison between the results of the one-mode and the multi-mode solution expansions, (iii) comparison with the results obtained through an elaborate finite element representation of the dam, and finally, (iv) comparison with the results obtained through the Makdisi-Seed11 iterative procedure for earth dam analysis. The comparisons show that the proposed technique can be used to determine adequately the transient earthquake response of long earth dams. Furthermore, the efficiency and low computational cost make the technique very attractive; it can easily and systematically be extended to two- and three-dimensional calculations of earth dam response. 相似文献
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The objective of this study is to estimate the shear wave velocity of earth dam materials using the vibration generated from artificial blasting events, and to verify its applicability. In this study, near-field artificial blast testing and monitoring were carried out at the Seongdeok dam, Korea, as the first blasting tests to be carried out on an existing dam in Korea. Vibrations were induced by four different types of blasting, using various explosive charge weights and depths of blasting bore-holes. During the tests, acceleration time histories were measured at the rock outcrop adjacent to the point of the explosion, and at the crest of the dam. The fundamental frequency of the target dam was computed from the frequency analysis of measured acceleration histories. Numerical analyses were carried out, varying the shear modulus of the earth fill zone and using the acceleration histories measured at the rock outcrop as input ground motions. From a comparison between the fundamental frequencies calculated by numerical analyses and those of measured records, the shear wave velocities with depth, which are closely related to shear moduli, could be estimated. It is found that the effect of different blasting types on shear wave velocity estimation for the target dam materials is negligible, and that shear wave velocity can be consistently evaluated. Furthermore, by comparing the evaluated shear wave velocity with empirical formulae from previous research, the applicability of the method was verified. Therefore, in cases of mid-to-small earth dams, where the earthquake record is not available, the shear wave velocity of earth fill materials can be reasonably evaluated using blasting vibration records obtained at the site adjacent to the dam. 相似文献