共查询到19条相似文献,搜索用时 169 毫秒
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基于XFEM的砼重力坝强震破坏模式及抗震安全评价 总被引:1,自引:1,他引:0
扩展有限元法(XFEM)通过在相关节点的影响域上富集非连续位移模式,使得对非连续位移场的表征独立于单元边界,可以有效描述混凝土中的裂纹扩展。采用XFEM对Koyna重力坝地震破坏过程进行了分析,结果表明大坝开裂破坏分布与Koyna大坝实际破坏情况及文献中的模型试验结果相符,验证了计算模型的有效性。将其应用到国内某混凝土重力坝,得到了强震作用下的动力响应及破坏模式,并据此评价大坝的抗震安全性及抗震超载潜能。研究表明,强震作用下,大坝首先在下游折坡出现裂缝并扩展至上游面形成贯穿性裂缝,同时在坝踵、上游坡度变化处也容易出现开裂破坏;该重力坝在设计地震作用下,尚有1.59~1.76倍的超载裕度,其抗震安全性能满足设计要求。 相似文献
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重大水利工程中,混凝土结构多处于高水压环境,坝体或多或少存在着裂缝,然而大部分开裂的混凝土坝仍能够安全运行,从而引申出是否可以允许混凝土结构出现裂缝,多大的裂缝才不至于引起破坏,以及用怎样一个合理的指标来对混凝土开裂程度进行描述评判的问题。该文以等效塑性应变表征混凝土弥散型裂缝模型数值模拟中的开裂破坏,通过混凝土单轴拉伸数值模拟,并根据试验资料及相关文献,建立了等效塑性应变与主拉应变、裂缝宽度之间的关系,得到对应于“有害裂缝”的等效塑性应变值。将方法和成果运用到混凝土重力坝的开裂研究中,具有较好的实际工程意义。 相似文献
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为了解配筋形式对单排配筋L形截面混凝土剪力墙在非工程轴方向的抗震能力影响,进行了2个单排配筋L形截面剪力墙模型的振动台试验,1个为普通单排配筋剪力墙,1个为带斜筋单排配筋剪力墙,2个剪力墙模型的总配筋量相同。通过在L形截面剪力墙的非工程轴方向输入El-Centro地震波,测试比较2个剪力墙模型在弹性、开裂及破坏阶段的动力特性、地震反应与破坏特征,分析不同配筋形式下L形截面混凝土剪力墙在非工程轴方向的抗震能力,结果表明,带斜筋与不带斜筋的单排配筋L形截面混凝土剪力墙在非工程轴方向均有良好的抗震性能,能够满足低多层建筑结构的抗震设计要求。 相似文献
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混合配筋混凝土结构将钢筋和纤维复合材料(FRP)筋混合配置于混凝土,可较好地解决钢筋混凝土(SRC)结构的耐久性问题和FRP筋混凝土结构脆性破坏的问题,已广泛应用于土木工程中。为了研究混合配筋混凝土板的抗爆性能,开展了不同比例距离下混合配筋混凝土板和钢筋混凝土板的非接触爆炸试验,对比分析两种板抗爆性能差异和确定混合配筋混凝土板的破坏模式。结果表明:比例距离为0.684 m/kg1/3时,混合配筋混凝土板位移峰值比钢筋混凝土板位移峰值大19.2%,但残余变形比钢筋混凝土板残余变形小27.3%。引入爆炸恢复指数评估混凝土板爆炸恢复能力,混合配筋混凝土板爆炸恢复指数大于钢筋混凝土板,混合配筋混凝土板有着出色的爆炸后恢复能力。混合配筋混凝土板背爆面破坏出现多条竖向裂缝和板对角线处斜裂缝,而钢筋混凝土板仅出现一条较宽的竖向主裂缝,多条斜裂缝向外辐射。混合配筋混凝土板随着比例距离的减小,破坏模式从整体弯曲破坏发展为整体弯曲破坏和局部混凝土破坏并存。结合试验数据提出混合配筋混凝土板最大支座转角θ的预测公式。为混合配筋混凝土板抗爆设计提供参考。 相似文献
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为了研究钢管混凝土组合桁梁-格构墩轻型桥梁的抗震性能,以干海子大桥为原型,设计制作了几何缩尺比例1∶8的两跨钢管混凝土组合桁梁-格构墩试验模型,利用福州大学地震模拟振动台台阵系统,采用实桥的设计地震波,进行了该轻型桥梁的基本动力特性试验、抗震性能试验及破坏特性研究。结果表明,模型实测频率和位移与实桥满足相似比关系;在横向或纵向地震作用下,桥墩格构式区域加速度放大效应明显,减小了主梁混凝土顶板的加速度响应;相同强度下,横桥向地震作用桥墩应变大于纵桥向地震作用,同时可以不考虑纵、横向地震力共同作用。在设计地震动作用下,墩顶位移满足位移限值的规定;模型未出现开裂和破坏现象,表明钢管混凝土组合桁梁-格构墩轻型桥梁具有良好的抗震性能。 相似文献
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High-pressure hydraulic fracturing (HF) of cracks is the crucial factor in the safety-assessment of high concrete dams, and fluid–structure interaction in HF is the key to accurately calculate the fluid pressure within cracks. In this study, a hybrid approach combining the extended finite element method (XFEM) and the finite volume method (FVM) is introduced to simulate HF in concrete dams. Through the hybrid approach XFEM-FVM, we can obtain water pressure distribution within cracks, which reflects the coupling relationship between water pressure and fracture width. This approach is verified by an example, and the numerical results agree well with the corresponding analytic solutions. Then, we use it to simulate the HF in a concrete gravity dam. Results show that, in contrast to the constant water pressure distribution within cracks, the distribution calculated by XFEM-FVM varies with time and leads to the bigger crack extension angle, contrary to growth length. It also illustrates the significance of considering fluid–structure interaction in HF progress. This study reveals that the approach is a very efficient tool for HF simulation in concrete dam. 相似文献
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Modeling the material behavior and estimation of the cracking capacity of concrete dams under the dynamic loading is important for safety operation purposes. In the present paper, an improved 3D co-axial rotating smeared crack model is used with the ability of updating the variable shear transfer coefficient. The model is implemented in the finite element code to assess the seismic cracking of three types of concrete dams, i.e. gravity, buttress, and arch dams.Results of the crack profiles confirm importance of the shear transfer coefficient in dynamic analysis of large concrete structures. It is found that the proposed model lead to less diffused cracks in concrete dams and can reasonably matches with the results obtained from experimental tests. 相似文献
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裂缝是混凝土结构的主要病害,查明裂缝的深度能够为结构的耐久性和安全性评价提供可靠的信息,但同时也是混凝土结构检测的难点之一。提出了一种基于数据驱动的学习算法,通过考察波经过带缝结构传播的信号预测裂缝深度,采用扩展有限元法(Extended finite element methods,XFEM)和边界吸收层模型模拟了带缝大体积混凝土结构中的波传播过程,将接收点的观测信号和裂缝信息配对。基于人工神经网络的机器学习模型建立了基于XFEM数据集的裂缝深度预测模型。对于含未知裂缝信息的混凝土结构,通过测得的观测点信号,利用建立的机器学习模型实现裂缝深度的实时预测。通过2个数值算例验证了该算法的性能,结果表明所提出的数据驱动算法能够准确预测裂缝深度。 相似文献
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用扩展有限元方法模拟混凝土的复合型开裂过程 总被引:3,自引:2,他引:3
用扩展有限元法对混凝土梁复合型开裂过程进行了数值模拟。裂纹面间的力学行为采用粘聚裂纹模型来描述,通过引入切向保留刚度考虑剪力分量的影响。开裂方向的计算采用了一种简化的最大切向应力准则。对Arrea和Ingraffea的混凝土梁复合开裂实验进行了数值模拟。计算给出了裂纹萌生、扩展的过程及破坏形态,并获得了与实验结果对比良好的荷载-裂纹开口滑移曲线。结果表明,扩展有限元法通过附加特定的位移模式,使裂纹两侧不连位移场的表达独立于网格划分,是一种能够模拟准脆性材料复合开裂问题的有效方法。 相似文献
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S. Jiang C. Du C. Gu X. Chen 《Fatigue & Fracture of Engineering Materials & Structures》2014,37(8):866-882
This paper is devoted to the extraction of the dynamic stress intensity factor (DSIF) for structures containing multiple discontinuities (cracks, voids and inclusions) by developing the extended finite element method (XFEM). In this method, four types of enrichment functions are used in the framework of the partition of unity to model interface discontinuity within the classical finite element method. In this procedure, elements that include a crack segment, the boundary of a void or the boundary of an inclusion are not required to conform to discontinuous edges. The DSIF is evaluated by the interaction integral. After the effectiveness of the implemented XFEM program is verified, the effects of voids, inclusions and other cracks on the DSIF of a stationary major crack are investigated by using XFEM. The results show that the dynamic effects have an influence on the path independence of the interaction integral, and these voids, inclusions and other cracks have a significant effect on the DSIF of the major crack. 相似文献
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Existence of a crack in structures would lead to a sudden failure and damage. Establishing a precise analytical model for the cracked element would be a powerful tool to achieve the right answers in the analysis of the structure. The main aim of this article is to formulate a hexahedral interface element for use in nonlinear crack analysis. In this investigation, the kinematics of the discontinuous displacement field along with the virtual work principle, for a body with an internal discontinuity, is utilized. Based on the suggested interpolation functions for the discrete segments, and also the element displacement field, the element stiffness matrix is calculated. The proposed element can be used for modeling of the discrete cracks in three-dimensional problems, such as a concrete dam. Several numerical examples are analyzed for the accuracy test and a few of them are presented here. The results indicated that utilizing sufficient elements yields suitable answers. 相似文献
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高土石坝抗震可靠度研究对大坝抗震防灾和震害风险研究具有重要意义。通过考虑地震动和筑坝料参数双重随机性,建立基于地震易损性和地震峰值加速度概率密度函数的高土石坝抗震可靠度模型,为研究不同设计使用年限的高土石坝抗震可靠度提供依据。通过拉丁抽样方法选取筑坝料参数样本并与选择地震动组合成样本对,选取坝顶相对震陷率作为性能参数,提出考虑抗震设防标准的高土石坝性能水平了;采用SWANDYNE Ⅱ程序进行动力计算,并根据改进云图法得到不同地震峰值加速度下坝顶相对震陷率的地震易损性三维曲面;结合糯扎渡高土石坝不同设计年限的概率分布函数与地震易损性曲面,确定不同设计年限失效概率和抗震可靠度。分析结果表明:随着设计使用年限增加,大坝各个性能水平可靠度不断减小,对于严重破坏状态下不同设计年限可靠度均能满足《水利水电工程结构可靠性设计统一标准》规范要求,说明糯扎渡高土石坝在变形方面抗震设计是合理的。 相似文献
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Ragnar Larsson Martin Fagerstrm 《International journal for numerical methods in engineering》2005,62(13):1763-1788
A theoretical and computational framework which covers both linear and non‐linear fracture behaviour is presented. As a basis for the formulation, we use the material forces concept due to the close relation between on one hand the Eshelby energy–momentum tensor and on the other hand material defects like cracks and material inhomogeneities. By separating the discontinuous displacement from the continuous counterpart in line with the eXtended finite element method (XFEM), we are able to formulate the weak equilibrium in two coupled problems representing the total deformation. However, in contrast to standard XFEM, where the direct motion discontinuity is used to model the crack, we rather formulate an inverse motion discontinuity to model crack development. The resulting formulation thus couples the continuous direct motion to the inverse discontinuous motion, which may be used to simulate linear as well as non‐linear fracture in one and the same formulation. In fact, the linear fracture formulation can be retrieved from the non‐linear cohesive zone formulation simply by confining the cohesive zone to the crack tip. These features are clarified in the two numerical examples which conclude the paper. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献