地震作用下丰满重力坝的塑性损伤     

程冬  张德岗  李守巨  刘迎曦  陈昌林 《岩土力学》2007,28(Z1):792-795

基于混凝土塑性损伤本构模型,将可以表征材料和结构渐进破坏的损伤变量作为内变量,考虑了混凝土拉压异性的损伤变量,利用有限元软件ABAQUS,对丰满混凝土重力坝在经受地震作用下的结构损伤区域的发展变化进行安全性评价。在数值计算过程中,对于受地震荷载作用所引起的地面水平运动而导致大坝水位水平运动对坝体的影响,通过扩充后的广义Westergaard公式予以计算模拟。通过分析得到了丰满大坝在地震作用下的塑性损伤破坏情况,并评价了丰满大坝的安全性,亦说明利用损伤力学对大坝进行安全性评价是一个可行的方法。  相似文献   

粘弹塑本构模型及用于冻土数值计算的柔度矩阵   总被引：5，自引：3，他引：2  

李栋伟  汪仁和  林斌 《冰川冻土》2007,29(2):322-326

随着寒区经济发展及冻结法施工技术在工程中的推广应用,对冻土蠕变的深入研究显得尤为重要.对冻土单轴流变试验结果分析,用非线性牛顿体替代线性牛顿体,从而对西原模型进行了改进,得到了冻土三向应力状态下的本构方程;并利用D-P屈服准则推导出应用与数值计算的柔度矩阵.通过有限元程序的二次开发,将本构模型添加到大型非线性程序ADINA中.用三轴蠕变试验检验了粘弹塑本构模型,获得相应的试验拟合曲线.结果表明:三轴蠕变试验与理论计算结果吻合良好,说明粘弹塑本构模型可以描述冻土在高应力下反映的非衰减性蠕变变形特征.  相似文献   

岩土材料极限分析上界法的讨论   总被引：9，自引：2，他引：7  

王敬林  郑颖人  陈瑜瑶  李克玉 《岩土力学》2003,24(4):538-544

现行的极限分析上界法,尽管求解结果合理,但理论上却存在一些矛盾：如试验证明,关联流动法则不适用于岩土材料,而现行解法却采用了关联流动法则;传统分析中假设体积不变,但计算中却出现大于实际的体积剪胀变形;按关联流动法则,应力特征线与速度滑移线重合,但在分析中却采用速度方向与应力特征线方向成 角;实际土体破坏时,破坏面上同时存在着剪切力 和正应力 ,但在计算中却反映不出摩擦功。近年在中国日益兴起的广义塑性力学理论为岩土材料的极限分析方法提供了科学的理论基础。作者提出了基于广义塑性力学的极限分析上界法,消除了上述矛盾,并获得了正确的计算结果。通过同经典算法的比较,证明了两种方法的计算结果几乎是一致的,但现行方法计算简便,因而,可作为一种实用的计算方法。论文还对上述两种算法作了系统的分析与比较,指出了它们求解的相同点与不同点。  相似文献   

真三轴条件下非饱和黄土的有效应力屈服特性     

方瑾瑾  冯以鑫  王立平  余永强 《岩土力学》2020,41(2):492-500

为了研究非饱和黄土在有效应力空间的屈服特性，利用真三轴仪对非饱和原状黄土进行了不排水等向净应力压缩固结和不同中主应力参数b值的剪切试验，研究了真三轴压缩条件下非饱和黄土的有效应力屈服变化规律。研究结果表明：有效应力比随着中主应力或净围压的增大而减小，中主应力的增大作用对有效球应力的影响大于广义剪应力；由有效应力比?体应变关系曲线确定的剪缩屈服曲线在有效应力空间具有良好的规律性，屈服点的有效屈服应力随着中主应力和初始吸力的增大而增大；π平面上的有效应力屈服强度面和强度破坏面与SMP强度准则稳合较好，有效球应力和初始吸力越大，屈服强度面和强度破坏面越大。提出了真三轴条件下弹性剪应变和塑性剪应变的计算公式，通过分析有效应力与塑性应变关系得出有效应力空间中不同子午平面内的塑性势面呈椭圆形，且随着中主应力的增大，椭圆屈服面增大。  相似文献   

RC structures cyclic behavior simulation with a model integrating plasticity,damage, and bond‐slip     

Bashar Alfarah  Juan Murcia‐Delso  Francisco López‐Almansa  Sergio Oller 《地震工程与结构动力学》2018,47(2):460-478

The behavior of reinforced concrete structures under severe demands, as strong ground motions, is highly complex; this is mainly due to the complexity of concrete behavior and to the strong interaction between concrete and steel, with several coupled failure modes. On the other hand, given the increasing awareness and concern on the worldwide seismic risk, new developments have arisen in earthquake engineering; nonetheless, some developments are mainly based on simple analytical tools that are widely used, given their moderate computational cost. This research aims to provide a solid basis for validation and calibration of such developments by using computationally efficient continuum mechanics‐based tools. Within this context, this paper presents a model for 3D simulation of cyclic behavior of RC structures. The model integrates a bond‐slip model developed by one of the authors and the damage variable evolution methodology for concrete damage plastic model developed by some authors. In the integrated model, a new technique is derived for efficient 3D analysis of bond‐slip of 2 or more crossing reinforcing bars in beam‐column joints, slabs, footings, pile caps, and other similar members. The analysis is performed by implementing the bond‐slip model in a user element subroutine of Abaqus and the damage variable evolution methodology in the original concrete damage plastic model in the package. Two laboratory experiments consisting of a column and a frame subjected to cyclic displacements up to failure are simulated with the proposed formulation.  相似文献   

Simulation of cyclic strength degradation of natural clays via bounding surface model with hybrid flow rule          下载免费PDF全文

Z. Shi  G. Buscarnera  R. J. Finno 《国际地质力学数值与分析法杂志》2018,42(14):1719-1740

Strength loss of natural clays subjected to seismic loading is a critical factor contributing to earthquake‐induced ground failure and associated hazards. This work proposes a bounding surface constitutive law to simulate cyclic strength degradation of natural clays resulting from the loss of structure and attendant accumulation of excess pore pressures. The proposed model employs an enhanced plastic flow rule that can simulate accurately the development of pore pressure and explicitly incorporates soil structure effects. The validation of the model with reference to the experimental evidence available for 3 structured clays shows that with a single set of parameters the proposed model can reasonably represent the mechanical behavior of natural clays under various loading conditions (1D compression, monotonic shearing in compression and extension, cyclic loading, and postcyclic shearing). Particularly, its satisfactory performance in terms of quantification of cyclic strength degradation encourages the use of the model in simulating boundary value problems related to the stability of geotechnical facilities under earthquakes.  相似文献   

双防线可恢复性能斜交网格结构耗能机制和抗震性能研究          下载免费PDF全文

李天翔  Yang T.Y.  童根树 《世界地震工程》2019,35(3):037-44

为提高斜交网格结构的抗震性能，提出一种双防线可恢复性能斜交网格结构。双防线可恢复性能斜交网格结构采用剪切耗能段和特定梁端塑形铰进行集中耗能，使主体结构构件保持弹性。剪切耗能段不承受和传递重力荷载，易在震后修复或更换，使建筑可迅速恢复功能。为实现目标耗能机制，对等效能量塑形设计法进行改进以适用于可恢复性能斜交网格结构，并进行结构设计举例。采用OpenSees软件对所设计结构建立详细的有限元计算模型，进行非线性动力时程分析，以验证双防线耗能机制并评估抗震性能。分析结果表明:（1）小震、中震和大震下的结构顶部位移角分别为0.28%、0.8%和1.7%，与性能设计目标基本相同；（2）中震时剪切耗能段屈服，特定梁端未出现塑性铰；（3）大震时，特定梁端出现塑性铰以增加结构耗能能力，剪切耗能段屈服且处于延性范围内。因此新型可恢复性能斜交网格结构具有有效的双防线耗能机制，在中震后可迅速修复，在大震中可保持延性，实现"中震可修，大震不倒"的性能目标。  相似文献   

基于ANSYS自定义单元的半刚性梁柱节点抗震滞回性能模拟分析          下载免费PDF全文

李冰洋  刘永华  刘中宪 《世界地震工程》2018,34(1):098-104

采用峰值指向滞回模型模拟半刚性连接在循环荷载下的非线性行为，建立了能同时考虑几何、材料和连接非线性的精细塑性铰法平面梁柱单元模型，利用ANSYS用户可编程特性（UPFs），对自定义单元进行编译并嵌入到ANSYS平台中。利用试验数据拟合得到滞回模型参数，经自定义单元进行分析计算，得到节点的载荷-位移滞回曲线。通过与试验结果对比分析表明:模拟结果与试验结果吻合良好，该单元模型具有很大优势，可用于半刚性梁柱节点的滞回性能分析。  相似文献   

台风作用下海上风机基础结构安全评价     

朱彬彬  王滨  李玉刚  楼敏俊  夏露  施勇 《海洋工程》2019,37(3):78-85

海上风机结构在运营期内可能面临极端风浪、地震等荷载作用。因此,极端工况作用下海上风机局部和整体结构反应将成为结构设计以及安全评价的重要参数。采用半整体方法,以桩基泥面最大位移、结构杆件极端承载力以及桩基抗压、抗拔承载力为判定指标,基于塑性可靠度理论,系统研究台风条件下运营期内海上风机基础结构可靠度指标变化规律,得出潜在的基础结构失效模式及相应判定指标。由研究可得,台风条件下运营期内海上风机基础结构各可靠度将显著受到基础冲刷、海生物生长和结构腐蚀的影响,并且结构失效模式将由单一模式破坏发展为多种模式联合失效。  相似文献   

A hypoplastic model for gas hydrate‐bearing sandy sediments          下载免费PDF全文

Xuhui Zhang  Jia Lin  Xiaobing Lu  Lele Liu  Changling Liu  Mingyao Li  Yewang Su 《国际地质力学数值与分析法杂志》2018,42(7):931-942

Gas hydrate‐bearing sediments (GHBSs) have been considered as a potential energy resource. In this paper, the mechanical properties of GHBS are firstly investigated by the integrated test apparatus for synthesis of GHBS using silty sand as skeleton. Triaxial tests indicate an obvious transition of stress‐strain relationship from strain hardening under low hydrate saturation and strain softening under high hydrate saturation. The hypoplastic models coupled with Drucker‐Prager criterion and the Mohr‐Coulomb criterion are proposed to analyze the stress‐strain relationship of GHBS with considering the effective porosity because of the hydrate filling in the pores of GHBS. The strain hardening and softening behaviors are well predicted with less material parameters compared with the classical models. Compared with the test results, the proposed hypoplastic models are verified to be capable of capturing the salient features of the mechanical behaviors of GHBS under the conditions of little temperature change and no hydrate dissociation.  相似文献