教学课程资源库 更多>>

关键词： 沉井基础   受力分析   稳定性   有限元分析  

摘要： 随着桥梁施工技术的快速发展，沉井基础被更多应用于诸多大型桥梁结构之中。然而，对于沉井基础数值分析的研究仍然没有较大进展，对沉井基础的计算还在沿用传统的近似计算法，对沉井基础在下沉过程中的受力分析还不明确。鉴于以上问题，本文对沉井基础的受力特性做了进一步深入的研究，具体内容概括如下: 1、介绍了沉井的基本构造以及组成部分。阐述了沉井基础的适用范围以及在下沉过程中遇到的问题和解决的方法。在受力分析的基础上，利用数值计算的结果说明沉井在下沉过程中遇到的问题。 2、对于沉井在下沉施工过程中的受力进行了总结与分析。根据刃脚反力的计算理论，建立一个完善的力学模型体系。利用该模型及前人已建立的模型，针对同一工程项目分析了刃脚反力、侧摩阻力、下沉系数与下沉深度之间的关系。 3、以某工程为例，对其进行了下沉验算、整体性承载力验算及稳定性计算，验证计算结果是否满足《公路桥梁地基基础设计规范》的要求。计算结果偏于保守，在满足桥规允许承载力的前提下改变材料属性，可供工程设计参考。 4、针对此工程实例，通过有限元建模分析，模拟出沉井基础在成桥状态下的受力状态，得出在不同工况下刃脚处的应力变化趋势，分析了不同混凝土强度对沉井基础底部受力的影响、不同钢筋直径对沉井基础底部受力的影响，不同刃脚度数对基底应力的影响，并提出其在施工过程中应注意的问题。将规范法的计算结果与有限元的计算结果进行对比，提出了规范法计算结果与有限元计算结果的差异，验证了规范法计算的保守性，并给出了部分建议，可供工程施工参考。

关键词： NiTi alloy   NiTi tube   shape memory alloy   finite element method   ball spinning  

摘要： As a new attempt, ball spinning was used to manufacture the *** shape memory alloy (NiTi SMA) tube at elevated temperature. The NiTi bar with a nominal composition of Ni50.9Ti49.1 (mole fraction, %) was solution treated and was used as the original tube blank for ball spinning. Based on the variable temperature field and the constitutive equation, rigid-viscoplastic finite element method (FEM) was applied in order to simulate the ball spinning of NiTi SMA tube. The temperature field, the stress field, the strain field and the load prediction were obtained by means of FEM. FEM results reveal that there is a temperature increase of about 160 °C in the principal deformation zone of the spun part. It can be found from the stress fields and the strain fields that the outer wall of NiTi SMA tube is easier to meet the plastic yield criterion than the inner wall, and the plastic deformation zone is caused to be in a three-dimensional compressive stress state. The radial strain and the tangential strain are characterized by the compressive strain, while the axial strain belongs to the tensile strain. The variation of spinning loads with the progression of the ball is of great importance in predicting the stable flow of the spun part.

关键词： FINITE-ELEMENT-METHOD   LEVEL SETS  

摘要： Titanium-alloy laminates fabricated by sheet materials using diffusion bonding process have drawn more and more attention in the recent years. Proper placement of nonwelded zones on the diffusion bonding (DB) interface within titanium-alloy laminates as crack arrest zones can improve damage tolerance. To achieve the optimal damage tolerance via designing non-welded zones, it is necessary to study fatigue crack growth characteristics for this type of laminates by adjusting all the relevant parameters such as geometrical sizes, locations, and the number of the nonwelded zones, which is highly time consuming. Therefore it is essential to develop a reliable and quick method to analyze the fatigue crack growth characteristics for titanium-alloy laminates with non-welded zones. In this paper, the extended finite element method (XFEM) which was employed to simulate the fatigue crack growth process and the applicability of this method to capture fatigue crack growth characteristics of titanium-alloy laminates with localized non-welded zones was also studied. The numerical results were compared with the experiment data, and the agreement on numerical and experimental results illustrated that the specific crack growth characteristics can be captured by using XFEM, thereby verifying the applicability of XFEM in the analysis of fatigue crack growth of the laminates with non-welded zones. The influence of non-welded zones on the fatigue crack growth was then discussed.

ISBN: (纸本)9787111425663

关键词： friction parameters   FEM calculation   foundation structures   SURFACE SUBSIDENCE   MINING SUBSIDENCE   PREDICTION   DEFORMATION   INTEGRATION   BUILDINGS  

摘要： When calculating the state of stress in a structure caused by relative strain of landscape which is a result of undermining, the structure is often deformed in order to create the specific situation. Each part of the structure resists the strain in a difference way. This depends on places where the structure is in contact with soil environment. When calculating the 3D foundation structures by means of the Finite Element Method (FEM), it is necessary to determine the soil environment resistance. For that purpose, most FEM software applications enable now to enter the friction parameters Clx and CIy. Unlike CIz which resists the structure in the direction perpendicular to the element's plane, these parameters are applied in the central line plane of a slab and rod element.

关键词： 桩筏基础   ABAQUS   分析  

摘要： 任何结构物的计算分析都是从建立计算模型开始的,即将其几何尺寸、材料性质、荷载作用方式和支撑条件与边界条件理想化。桩筏基础共同作用计算模型则是建立在对基础结构、地基土和接触模型条件这三个方面的若干简化假设之上的。以前Poulos、赵宏锡、董建国等国内外学者进行地基基础共同作用时是假定结构和地基土两者都是线弹性的,然而由此进行的共同作用分析的结果与实测情况有相当大的出入。重要原因之一就是共同作用分析过程中没有考虑两者及其接触问题上的非线性性状。地基与基础共同作用的非线性分析已引起广泛的注意,认为它是促使共同作用分析结果走向实用的关键。

关键词： 有限元分析法   地基工程   应用分析  

摘要： 地基基础工程施工中,地基岩土体的安全系数对地基基础工程的稳定性和安全性有着极为重大的影响。通过降低地基岩土体的强度或提高地基岩土体承担的荷载等施工实验,经过有限元函数的计算后,可以确定地基岩土体的安全系数。本文将对有限元极限分析法在地基基础工程中的应用做浅显研究。

关键词： 基础变形模量   变形模量不确定性   有限元等效应力   响应面方法   拱坝  

摘要： 为研究基础变形模量的不确定性对拱坝应力的影响,建立以基础变形模量为设计变量、以坝体应力为目标函数的计算拱坝最大应力的最优化模型;利用均匀试验设计法构造拱坝最大有限元等效应力与基础变形模量之间的二阶多项式响应面。工程实例分析表明,所建立的响应面模型具有较高的精度,当已知基础变形模量变化范围时可以较好地确定拱坝的最大有限元等效应力。

关键词： 扭剪   桶形基础   有限元分析   承载力  

摘要： 针对均质软黏土地基上扭剪荷载作用下桶形基础的破坏包络面,运用大型有限元分析软件ABAQUS进行了三维非线性数值分析.通过比较系统的数值计算与分析,分别考察了V-T、H-T、V-H-T空间内桶形基础的地基破坏模式以及破坏包络面特性,进而推导了其破坏包络面的拟合数学表达式.由此表明:(1)桶形基础在扭剪荷载作用下,以桶体中心为圆心,形成圆形塑性区,并且不断地向外扩展,距离桶体越近的区域塑性应变相对较为显著;(2)V-T、H-T空间内桶形基础的承载力性能随着桶体长径比(L/D)的增大而提高;(3)推导的破坏包络面拟合数学表达形式,可以近似地表达桶形基础的承载性能,以此评价扭剪荷载作用下桶形基础的稳定性.

关键词： 有限元   煤矿   带式输送机  

摘要： 通过对煤矿带式输送机的受力特性,分析建立了带式输送机沿轴线方向的力学模型,利用有限元软件,建立起了输送带以及滚筒摩擦接触部分的三维模型。