有限单元法在边坡稳定性分析中的应用

本文对有限单元法进行了简要的介绍,并利用有限单元法对某边坡进行稳定性分析,通过对分析成果的整理和研究得出了边坡的稳定性结论,该结论与极限平衡法的分析成果对比表明分析取得了满意的效果。     

有限元法的特点及其在边坡工程中的应用实例

简述了在岩土工程中常用的有限元位移法的特点及计算步骤,对边坡分别在天然状态和坡顶均布荷载状态下的应力、应变作数值分析比较,分析结果显示在有荷载作用条件下边坡的塑性区贯通性强,相比天然状态下更易发生失稳破坏。     

有限元-无限元耦合分析软弱层桩基沉降与变形

采用无限元模拟远场区域土体、有限元模拟临近建筑物的土体,建立深厚软弱地基基础分析的无限元与有限元边界耦合分析方法,分析了深厚软弱地基上桩基础的沉降及变形形态,以及沉降对桩侧摩阻力的分布影响,并验证了无限元和有限元耦合分析的合理性。     

Coupling analysis of finite element and finite volume method for the design and construction of FPSO crane

The aim of this study is to establish a procedure for systematic design and performance evaluation of an offshore platform (FPSO; Floating, Production, Storage and Offloading) crane using a computational approach. Coupling analyses of the finite element and finite volume methods, which are applicable for ensuring robust design under the consideration of nonlinear environmental effects, were carried out. In order to investigate the effects of dynamic loading, the boundary conditions of an offshore platform crane having a lifting capacity of 100 tons were studied. In the finite volume method, a series of analyses were carried out using the computational fluid dynamics code, FLUENT. The crane's weight, maximum lifting load, calculated wind pressure and boundary conditions such as the inclination of the deck due to the extreme roll motion of FPSO were also considered in the finite element analyses using the commercial code, MSC/NASTRAN. Deformation, stress distribution, as well as fatigue life estimation were conducted under the unified computational environment. An advanced procedure for evaluating design concept validation was proposed for the application of FPSO design and construction.     

Composite element method for the bolted discontinuous rock masses and its application

This paper presents a composite element method (CEM) for discontinuous rock masses reinforced by fully grouted bolts. This element allows one to generate mesh without considering exactly the existence of bolts and joints, which further allows for an important simplification in the pre-process work. The sub-elements of rock, grout, bolt, joint, rock/grout interface and bolt/grout interface are defined using corresponding mapped nodal displacements at the composite element. The mapped nodal displacements can be determined using the governing equations established by means of the virtual work principle. Based on the mapped nodal displacements deformation and stress in each sub-element can be further obtained. The comparative study of the CEM and the conventional finite element method (FEM) has been carried out for the preliminary verification example. The numerical study for the rock bolt crane girder of an underground powerhouse by FEM and CEM is presented as the engineering application example, in which the attention has been paid to the portion of the contact face between the girder and surrounding rock masses, the contact faces between the bolts and surrounding rock masses, as well as to the portion where the rock bolt penetrates the contact face. The comparative and application studies show the validation and advantages of the CEM.     

温度场和温度应力的有限元分析

阐述了平面温度场与温度应力进行有限元分析的全过程,结合ANSYS大型软件对温度场与温度应力进行了模拟计算,为实际工程中考虑温度场与温度应力的作用提供了依据。     

Structural parameter identification and damage detection for a steel structure using a two-stage finite element model updating method

A two-stage eigensensitivity-based finite element (FE) model updating procedure is developed for structural parameter identification and damage detection for the IASC-ASCE structural health monitoring benchmark steel structure on the basis of ambient vibration measurements. In the first stage, both the weighted least squares and Bayesian estimation methods are adopted for the identification of the connection stiffness of beam-column joints and Young’s modulus of the structure; then the damage detection is conducted via the FE model updating procedure for detecting damaged braces with different damage patterns of the structure. Comparisons between the FE model updated results and the experimental data show that the eigensensitivity-based FE model updating procedure is an effective tool for structural parameter identification and damage detection for steel frame structures.     

有限元分析的位移控制法及其应用

对于非线性问题的有限元分析 ,位移控制法 (DCM)比常用的载荷控制法 (LCM)有着更广泛的应用和更强的适应能力。但因DCM在求解技术上的一些难度 ,限制了其在岩土力学中的应用。本文利用Sherman Morrison定理 ,使得DCM仅需很少的运算量 ,对经典的LCM程序做少量的修补 ,即可造就一个有良好数值特性的DCM程序     

有限单元法概述及其基本概念的分析

通过对有限单元法的概述,对有限单元法的分析过程以及基本概念进行了剖析,并作了简要说明,以使工程设计人员能更好的掌握有限单元法,更加高效安全的解决实际问题。     

有初始间隙摩擦接触问题的有限元混合法

针对三维有初始间隙摩擦接触问题,提出了一种新的迭代求解方法--有限元混合法。根据接触问题局部非线性的特点,将作用在接触体上的力系分解为外力和接触界面上的接触力,以接触体的位移为基本未知量,而以接触区域局部坐标系下的结点接触力为迭代变量,将非线性接触迭代收缩在可能接触面上进行,把复杂的摩擦接触非线性反映在接触力的变化上,使得迭代计算变得简单易行,并且对于存在多个接触界面的多体接触问题,可以保持柔度矩阵的对称性和稀疏性,大大提高了计算效率。文中首先给出了三维有初始间隙摩擦接触问题的力学模型,推导得出了相应的有限元柔度方程,然后详细给出了迭代求解步骤。最后通过两个数值算例来验证本文方法的正确性和有效性。     

三维离散单元法及其在滑坡分析中的应用

介绍了三维离散单元法的基本原理,编制了相应的C语言程序,并对具体的滑坡实例进行了模拟,发现计算结果与已有研究成果较为一致,表明三维离散单元法是一种可以动态模拟山地滑坡行为的比较适宜的数值方法。     

Tests on mechanical behavior of unsaturated decomposed granite and its modelling considering finite deformation

Generally speaking, most of the geomaterials in the surface ground are in an unsaturated state. The mechanical and hydraulic properties of unsaturated soil are much more complicated than those of saturated soil. To rationally describe these properties, it is important to couple the stress-strain relation of the unsaturated soil with its water retention characteristics using rational state variables. In this paper, oedometer and triaxial compression tests on decomposed granite under constant-suction and constant degree of saturation conditions were conducted. Based on the test results, a modified constitutive model was proposed to build an incremental relation between the degree of saturation and suction that considers the influence of finite deformation. The modified model was utilized to simulate the corresponding laboratory tests. It is found that the modified constitutive model has satisfactory accuracy to describe the mechanical and hydraulic properties of unsaturated decomposed granite, which verified the reasonability of the assumption adopted in this paper. The test results are also helpful for the understanding of the moisture characteristics of the decomposed granite under constant degree of saturation condition.     

3D finite element method (FEM) simulation of groundwater flow during backward erosion piping

Backward erosion piping is an important failure mechanism for cohesive water retaining structures which are founded on a sandy aquifer. At present, the prediction models for safety assessment are often based on 2D assumptions. In this work, a 3D numerical approach of the groundwater flow leading to the erosion mechanism of backward erosion piping is presented and discussed. Comparison of the 2D and 3D numerical results explicitly demonstrates the inherent 3D nature of the piping phenomenon. In addition, the influence of the seepage length is investigated and discussed for both piping initiation and piping progression. The results clearly indicate the superiority of the presented 3D numerical model compared to the established 2D approach. Moreover, the 3D numerical results enable a better understanding of the complex physical mechanism involved in backward erosion piping and thus can lead to a significant improvement in the safety assessment of water retaining structures.     

有限单元法库区渗流场数值模拟及敏感性分析

采用FORTRAN程序,编写了调用针对东部某抽水电站上库区渗流场数值模拟的计算程序,研究了库区渗流场的计算方法,并论证了该计算方法的正确性和实用性,分析结果证明该计算方法适应性强、精度高、应用方便、实用性好。     

坑边逆作法施工技术及二维有限元分析的应用

介绍了坑边逆作法的施工技术特点,提出一种经改进的地下坑边逆作主体梁板结构与土体—围护墙结构相分离的有限元分析计算思想,对开挖阶段水平支撑系统进行了数值分析,并对开挖卸载对围护结构以及周边环境的数值进行了模拟分析,供类似工程参考。     

高级切线模量法及其在地基沉降计算中的应用

切线模量法方法简单、参数少,易于工程应用,研究表明在计算常规尺寸的基础时具有较好的精度,而对于筏板这样的大尺寸基础时,当计算深度较深时,存在计算沉降偏大的问题.为此提出了考虑初始切线模量沿深度增大的高级切线模量法,通过与实际工程案例和小应变有限元数值计算方法结果比较,高级切线模量法能更符合实际,进一步发展完善了切线模量...     

Time-variant finite element reliability analysis – application to the durability of cooling towers

Durability of natural-draught cooling towers is investigated using finite element reliability analysis. A response surface of the linear finite element model is first derived from mechanical considerations. This surface is explicit and exact under certain conditions and requires a single multi-load finite element analysis. This leads to an analytical formulation of the reliability problem. The influence of concrete carbonation and the induced rebars corrosion is then studied in the framework of time-variant reliability analysis. It is shown that the problem reduces to a sequence of time-invariant problems that can be solved using the first-order reliability method (FORM). The evolution in time of the probability of failure in a single point is computed as well as sensitivity factors. Finally, an attempt to introducing space-variant reliability is made. The great difference between the numerical results obtained in the first and in the second approach is emphasized.     

基于有限差分与离散元耦合的支挡结构数值计算方法

土体与支挡结构的变形与稳定是岩土工程界关注的一个重要问题。作为探讨,介绍了运用快速拉格朗日有限差分与颗粒离散单元外部耦合的方法,对处于系统中的不同部位,分别应用二维刚性颗粒离散单元与允许大应变的有限差分网格,模拟离散体与结构物的相互作用,连续域与非连续域的平滑过渡则通过计算过程中满足两域对应边界的相容条件与平衡条件实现。就耦合的实现途径进行了说明,并将其应用于衡重式挡墙与墙后填土相互作用的分析,对比计算结果与现场实测数据,证明采用的方法能较有效地再现土与支挡结构的力学变形规律。     

Improvement in accuracy of the finite element method in analysis of stability of Euler–Bernoulli and Timoshenko beams

The problem of buckling of the Euler–Bernoulli and Timoshenko beams is analyzed by the finite element method. Significant improvement in accuracy of the method is obtained by replacing the discontinuous function of the bending moment related to the approximation of the eigenfunction obtained by FEM by a “smoothed” function in the Rayleigh quotient. The smoothed function is obtained by fitting the discontinuous one using the least square technique.