西安东门城墙的弹塑性有限元分析

西安东门城墙是我国的重点保护文物，对其研究意义重大．采用俞茂宏统一强度理论建立的弹塑性本构模型对其研究，得到了不同强度准则下的荷载系数位移曲线、塑性区分布、主应力迹线、弹塑性极限等结构特性．研究表明，不同的强度理论（如ＭｏｈｒＣｏｕｌｏｍｂ理论、广义双剪强度理论和ＤｒｕｃｋｅｒＰｒａｇｅｒ准则）对城墙结构分析有很大的影响．     

土动力本构模型初探

在粘弹性和弹塑性基本理论的基础上，综合阐述了目前国内外土体动力本构模型，并对各种模型的优缺点进行了比较。     

双剪统一弹塑性本构模型及其工程应用

本文提出了基于俞茂宏统一强度理论的双剪统一相关和非相关流动的弹塑性本构模型，并给出了该统一弹塑性本构模型的有限元实施方法。重点讨论了所谓“奇异屈服面”奇异性的处理方法，定义了两类不同类型的奇异形式，给出了它们的不同处理方法。该方法既直观、简单又便于有限元的实施，它对于其它类型“奇异屈服面”角点奇异性的处理同样适用。应用基于该统一弹塑性本构模型的有限元程序ＵＥＰＰ（ＵｎｉｆｉｅｄＥｌａｓｔｏ－ＰｌａｓｔｉｃｆｉｎｉｔｅｅｌｅｍｅｎｔＰｒｏｇｒａｍ），验证了作者提出的双剪统一弹塑性本构模型及其实施方法的正确性。统一强度理论和双剪统一弹塑性本构模型可以广泛应用于各种土木、机械、航空和岩土工程的结构分析。     

混凝土面板坝面板动力损伤有限元分析

联合采用混凝土塑性损伤模型和堆石料弹塑性本构模型,建立了面板堆石坝弹塑性动力分析方法,研究了地震荷载作用下混凝土面板的损伤发生和发展过程。计算结果表明：地震时,在0.65H（H为坝高）附近顺坡向拉应力最大,面板首先在该部位出现损伤,同时由于鞭稍效应,0.85H面板附近也出现损伤;采用损伤模型,损伤部位的面板出现软化,应力得到释放,计算结果比线弹性模型更加合理;采用塑性损伤模型可以反映混凝土面板渐进破坏过程,通过损伤变量可以清晰地了解面板的损伤分布和薄弱环节。此研究成果可以为进一步开展混凝土面板堆石坝极限抗震能力及抗震措施分析提供有效手段。     

冲击荷载作用下土体动力特性有限元分析

运用有限元软件ABAQUS,模拟了冲击荷载作用下土体动力响应特性,探索了夯锤运动动力特性和土体动态响应特征与规律,有助于进一步认识强夯加固机理,提高地基处理质量。     

土中爆炸波传播及其动力本构模型问题的研究综述

文章阐述了土中爆炸波传播及其动力本构模型建立的问题,综述了爆炸波在土中包括饱和土和非饱和土的传播规律,以及土介质动力本构模型研究的现状和进展,对不同模型的好处及不足进行了分析,重点阐述了С.С.Григорян提出的弹塑性介质模型,指出了目前研究中存在的问题和对未来的发展方向作了介绍。     

液化场地桩-土-结构动力相互作用的有限元分析

基于Biot两相饱和多孔介质动力耦合理论,采用有效应力方法对液化场地桩基础的地震反应进行了三维有限元分析。在饱和液化砂土的循环塑性模拟中,采用了超固结边界面、Armstrong-Frederick型非线性运动硬化准则和非关联流动准则来描述动荷载作用下砂土的循环活动性以及液化强度等特性。对于桩的动力本构行为,则采用了可以考虑体积效应和轴向力影响的梁-柱单元来模拟。以某城市高架桥的实际工程为例,应用该方法对地基液化时桩-土-结构的动力相互作用进行了计算分析,并得到了一些有用的结论。     

边坡稳定性有限元分析的处理技巧

在不同区域采用不同的本构模型进行边坡稳定性分析,能有效地消除有限元分析中的边界效应,真实地反应出边坡的受力状态。应用强度折减系数法得到边坡的稳定安全系数,并与极限平衡法的结果进行比较。分析高边坡和带有软弱夹层的边坡,得出较满意的结果。     

爆炸荷载作用下钢柱的动力反应分析

建筑室内爆炸超压载荷,考虑钢材在高应变速率下的材料力学性能的变化,对结构竖向构件钢柱在爆炸超压载荷作用下的动力反应进行数值分析。结果表明:采用Johnson-Cook本构模型,可以有效地模拟钢柱在爆炸荷载作用下的动力行为;对于给定截面型式的钢柱,钢柱长度及柱顶荷载的大小对钢柱在爆炸荷载作用下的承载能力有很大的影响。     

混凝土平面应力状态下的有限元分析

本文采用非线性的弹塑性本构模型,用Ottenson四参数强度准则判断混凝土所处的状态,分别对起弹塑性状态进行有限元分析,基于本文理论编制有限元程序验证了本文理论和程序的可行性和正确性。     

自锚式悬索桥结构有限元动力分析

随着交通事业的快速发展,大量复杂桥梁快速兴建。桥梁结构的动力分析是桥梁安全健康监测的重要保障。有限元建模是桥梁结构动力分析的重要研究方向。以自锚式悬索桥天津市富民桥为实例,应用有限元建模并进行动力分析,获得了该桥的前5阶模态振型。研究表明,该方法可行可靠,且可视化,有一定的应用性和适用性。     

复合土钉墙的有限元分析

采用同济大学编制的有限元软件分析了复合土钉墙的变形、受力状态,得出复合土钉墙变形与土钉墙变形有很大不同,水泥搅拌桩的存在改变了土钉力的分布,但其破裂面仍然为圆弧滑动破裂面,采用该有限元法进行工程实际设计是合理的。     

Nonlinear finite element analysis of short-limbed wall

Combined with the actual project, this paper carries out a nonlinear finite element analysis on 2 groups, 6 short-limbed shear walls, through the finite element calculation software ANSYS. The stress-strain relation of the models, and the effects of the type of sections and the axial compression ratios on the models can be obtained, providing a reference for future design. __________ Translated from Journal of Wuhan University of Technology, 2007, 29 (Suppl. II): 118-123 [译自: 武汉理工大学学报]     

System reliability analysis of soil nail wall using random finite element method

Soil nail wall is a compound system which for safety margin determination, consideration of safety factors of its components and their correlations is required. In this paper, considering a real site using the random finite element method (RFEM), the reliability indices of global stability, lateral displacement stability, tensile strength, and pullout resistance stability as components of the soil nail wall system are obtained. In another section of the paper, using the sequential compounding method (SCM), the importance of the mentioned stability modes and their effects on system reliability and system probability of failure are represented. Results show that the most considerable interdependence is between the global and lateral displacement stabilities. Among the reliability indices of the components, the minimum one is attributed to the pullout resistance. Furthermore, the uppermost row of the nails has the most critical reliability index compared with the others. The locations of the slip surfaces and nail intersections varied from 0.05–0.90 of the nail length, which means that the uncertainty of the soil parameters has the most significant effect on the pullout resistance safety factor of the nails. The performance level of the soil nail wall decreases from below average to poor when the soil nail wall is considered to be a system with series components.

     

结构优化设计的有限元方法分析

从理论上说明了结构优化设计的教学过程,介绍了大型有限元软件ANSYS优化设计的基本原理及主要步骤,并应用于屋架的优化设计中,取得了理想的结果,为其在实际工程优化中的应用提供了例证。     

Investigation of long-term behaviour of thermal wall by finite element analysis

Energy foundations utilise the natural thermal energy stored underground for the space heating and/or cooling of buildings. This technology can be used for lowering carbon dioxide gas emissions. However, there has been very limited research on the effects of cyclic heating and cooling on the structural performance of thermo-active diaphragm walls (thermal walls). An investigation of the long-term behaviour of a thermal wall is conducted in this study by a finite element analysis. The complex thermo-hydro-mechanical (THM) responses due to the operation of the thermal wall are analysed. With no operation of the thermal wall, the earth pressure and the wall movement change due to the dissipation of the excess pore pressure developing from the construction. However, there is only a small change in the bending moment of the wall. With the operation of the thermal wall, the thermal differential across the diaphragm wall induces thermal strain, and therefore, an increase in curvatures, resulting in an increase in the bending moment compared with no operation of the thermal wall. This study shows the necessity of examining the thermally induced effects of a thermal wall in the design, including variations in the bending moment of the wall, the cyclic changes in the earth pressure acting on the diaphragm wall, and the thermally induced soil shrinkage/expansion.     

加筋土挡墙试验研究及有限元分析

通过室内模型试验对加筋土挡墙的变形进行了研究,用分离式有限元法对加筋土挡土墙进行分析计算,结果表明:有限元分析结果与模型试验的结果具有较好的一致性,通过加筋能明显提高挡土墙的稳定性和承载力,填料的性质对加筋效果有重要影响.     

Stochastic finite element method for slope stability analysis

This paper describes a stochastic finite element method using the first-order approximation at a failure point of a set of random variables. The method is extended to equivalent normal represtation of non-normal distributions and offers two advantages: (1) It gives a consistent measure of failure probability for the limit-states defined in terms of different but equivalent performance function formulations, (2). It can be applied to reliability analysis for non-normal variants. Results using this method are compared favorably with that of Monte Carlo simulation in a simple example. Furthermore, this method will be applied to earth slope stability analysis to give probability levels for local and global failures on a potential failure surface.     

Improved numerical method for time domain dynamic structure-foundation interaction analysis based on scaled boundary finite element method

Based on the reduced set of base function in scaled boundary finite element method (SBFEM), an improved time domain numerical approach for the dynamic structure-foundation interaction analysis was proposed. With reasonable choice of the number of base functions, the degrees of freedom on the structure-foundation interface were reduced and the associated computation for the calculation of convolution integral was greatly reduced. The results of this proposed approach applied to the calculation of a gravity dam and an arch dam. The acceleration frequency response functions were calculated and the influences affected by different reduced set of base functions as well as full set were compared. It was found that a higher degree of reduced set of base functions resulted in a significant increase of computational efficiency but a little bit of loss in accuracy. When the reduced set was decreased by 60%, the efficiency may be increased to up to five times, while the loss of accuracy of peak value of response will be less than 4%. It may be concluded that the proposed approach is suitable for large-scale structure-foundation interaction analysis.     

Improved numerical method for time domain dynamic structure-foundation interaction analysis based on scaled boundary finite element method

Based on the reduced set of base function in scaled boundary finite element method (SBFEM), an improved time domain numerical approach for the dynamic structure-foundation interaction analysis was proposed. With reasonable choice of the number of base functions, the degrees of freedom on the structure-foundation interface were reduced and the associated computation for the calculation of convolution integral was greatly reduced. The results of this proposed approach applied to the calculation of a gravity dam and an arch dam. The acceleration frequency response functions were calculated and the influences affected by different reduced set of base functions as well as full set were compared. It was found that a higher degree of reduced set of base functions resulted in a significant increase of computational efficiency but a little bit of loss in accuracy. When the reduced set was decreased by 60%, the efficiency may be increased to up to five times, while the loss of accuracy of peak value of response will be less than 4%. It may be concluded that the proposed approach is suitable for large-scale structure-foundation interaction analysis. __________ Translated from Shuili Xuebao, 2007, 38 (1): 8–14 [译自: 水利学报]