The Triangular Hermite Finite Element Complementing the Bogner-Fox-Schmit Rectangle

The Bogner-Fox-Schmit rectangular element is one of the simplest elements that provide continuous differentiability of an approximate solution in the framework of the finite element method. However, it can be applied only on a simple domain composed of rectangles or parallelograms whose sides are parallel to two different straight lines. We propose a new triangular Hermite element with 13 degrees of freedom. It is used in combination with the Bogner-Fox-Schmit element near the boundary of an arbitrary polygonal domain and provides continuous differentiability of an approximate solution in the whole domain up to the boundary.

Review on the Application of Bamboo-Based Materials in Construction Engineering

Due to the continuously increasing demand for building materials across the world,it is necessary to use renewable materials in place of the existing nonrenewable materials in construction projects.Bamboo is a fast-growing flowering plant that may be used as a renewable material in construction.The use of bamboo in the construction of buildings can improve its long-term carbon fixation capacity and economic benefits.Although bamboo has the advantages of superior performance,low carbon content,high energy-saving and emission-reducing capacity,bamboo is an anisotropic material,which has many factors affecting its material performance,large variability of material performance,lack of systematic research,and the use of bamboo as the main building material is not always limited.This paper systematically summarizes the research status of bamboo as a building material from the aspects of bamboo composition,gradation,material properties,bamboo building components,connection nodes,and use of artificial boards.On this basis,some constructive suggestions are put forward for the further study of bamboo in the field of architecture.

Novel high-performance element in the electromagnetic finite-element method——node-edge element

It is known in the computational electromagnetics （CEM） that the node element has a relative wellconditioned matrix, but suffers from the spurious solution problem; whereas the edge element has no spurious solutions, but usually produces an ill-conditioned matrix. Particularly, when the mesh is over dense, the iterative solution of the matrix equation from edge element converges very slowly. Based on the node element and edge element, a node-edge element is presented, which has no spurious solutions and better-conditioned matrix. Numerical experiments demonstrate that the proposed node-edge element is more efficient than now-widely used edge element.

BOUNDARY ELEMENT ANALYSIS OF CONTACT PROBLEMS USING ARTIFICIAL BOUNDARY NODE APPROACH

An improved version of the regular boundary element method, the artificial boundary node approach, is derived. A simple contact algorithm is designed and implemented into the direct boundary element, regular boundary element and artificial boundary node approaches. The exisiting and derived approaches are tested using some case studies. The results of the artificial boundary node approach are compared with those of the existing boundary element program, the regular element approach, ANSYS and analytical solution whenever possible. The results show the effectiveness of the artificial boundary node approach for a wider range of boundary offsets.

Implementing the Node Based Smoothed Finite Element Method as User Element in Abaqus for Linear and Nonlinear Elasticity

In this paper,the node based smoothed-strain Abaqus user element(UEL)in the framework of finite element method is introduced.The basic idea behind of the node based smoothed finite element(NSFEM)is that finite element cells are divided into subcells and subcells construct the smoothing domain associated with each node of a finite element cell[Liu,Dai and Nguyen-Thoi(2007)].Therefore,the numerical integration is globally performed over smoothing domains.It is demonstrated that the proposed UEL retains all the advantages of the NSFEM,i.e.,upper bound solution,overly soft stiffness and free from locking in compressible and nearly-incompressible media.In this work,the constant strain triangular(CST)elements are used to construct node based smoothing domains,since any complex two dimensional domains can be discretized using CST elements.This additional challenge is successfully addressed in this paper.The efficacy and robustness of the proposed work is obtained by several benchmark problems in both linear and nonlinear elasticity.The developed UEL and the associated files can be downloaded from https://github.com/nsundar/NSFEM.

Nonlinear simulation of arch dam cracking with mixed finite element method

This paper proposes a new, simple and efficient method for nonlinear simulation of arch dam cracking from the construction period to the operation period, which takes into account the arch dam construction process and temperature loads. In the calculation mesh, the contact surface of pair nodes is located at places on the arch dam where cracking is possible. A new effective iterative method, the mixed finite element method for friction-contact problems, is improved and used for nonlinear simulation of the cracking process. The forces acting on the structure are divided into two parts： external forces and contact forces. The displacement of the structure is chosen as the basic variable and the nodal contact force in the possible contact region of the local coordinate system is chosen as the iterative variable, so that the nonlinear iterative process is only limited within the possible contact surface and is much more economical. This method was used to simulate the cracking process of the Shuanghe Arch Dam in Southwest China. In order to prove the validity and accuracy of this method and to study the effect of thermal stress on arch dam cracking, three schemes were designed for calculation. Numerical results agree with actual measured data, proving that it is feasible to use this method to simulate the entire process of nonlinear arch dam cracking.

A novel four-node quadrilateral element with continuous nodal stress

Formulation and numerical evaluation of a novel four-node quadrilateral element with continuous nodal stress（Q4-CNS）are presented.Q4-CNS can be regarded as an improved hybrid FE-meshless four-node quadrilateral element（FE-LSPIM QUAD4）, which is a hybrid FE-meshless method.Derivatives of Q4-CNS are continuous at nodes, so the continuous nodal stress can be obtained without any smoothing operation.It is found that,compared with the standard four-node quadrilateral element（QUAD4）,Q4- CNS can achieve significantly better accuracy and higher convergence rate.It is also found that Q4-CNS exhibits high tolerance to mesh distortion.Moreover,since derivatives of Q4-CNS shape functions are continuous at nodes,Q4-CNS is potentially useful for the problem of bending plate and shell models.

A PENALTY-HYBRID FINITE ELEMENT ANALYSIS OF STOKES FLOW

A type of penalty-hybrid variational principle is suggested for the analysis of Stokesian flow. On such a basis, a finite element model is formulated featuring, among others, a priori satisfaction of the deviatoric stress and hydrostatic pressure on linear momentum balance equations. Also in the present scheme the hydrostatic pressure is successfully eliminated at the element level, leaving only nodal velocities as solution unknowns. A series of 4-node and 8-node quadrilateral elements are derived and examined. Numerical examples demonstrating their characteristic behaviors are also included.

Design on the Prestressed Concrete Frame Beam-column

A bidirectional ribbed concrete beam slab structure was widly adopted for the upper space of industrial buildings.To maintain ample space and minimize the presence of conventional columns,a bidirectional prestressed concrete beam is often employed.The intersection node of the prestressed concrete frame beam column was characterized by a high density of steel reinforcement,significant structural loads,and complex construction requirements.To ensure the quality,safety,and progress of prestressed frame beamcolumn intersection nodes during construction,this article proposed a new technology for constructing such nodes,which includes setting the tensioning and haunching ends of nodes at different positions,using ABAQUS finite element software to optimize the design of cross-sectional dimensions,conducting stress analysis simulations.

A 17-node quadrilateral spline finite element using the triangular area coordinates

Isopaxametric quadrilateral elements are widely used in the finite element method. However, they have a disadvantage of accuracy loss when elements are distorted. Spline functions have properties of simpleness and conformality. A 17onode quadrilateral element has been developed using the bivaxiate quaxtic spline interpolation basis and the triangular area coordinates, which can exactly model the quartic displacement fields. Some appropriate examples are employed to illustrate that the element possesses high precision and is insensitive to mesh distortions.

NORMALIZED ELEMENT NODE TOPOLOGICAL MATRIX OF FINITE ELEMENT MESHES

On the basis of concept of element node topological analysis, the normalized element node topological matrices for finite element meshes are presented in the paper, including 3-node and 6-node triangular element, 4-node and 8-node quadrilateral element, 8-node and 20-node hexahedral element. It is beneficial to further analyzing topological characteristics of finite element models and automatic generation of meshes

装配式钢筋混凝土梁柱螺栓连接节点抗震性能试验

提出了一种干式装配式梁柱节点,该节点由核心区梁端外包钢套筒与柱预留孔洞实现螺栓连接。为了验证节点构造的合理性,揭示其受力工作机理,设计并制作3组节点试件,以轴压比和螺栓等级作为试验变量,进行了3个工况的低周往复拟静力破坏性试验。研究节点破坏形式及抗震性能,得到试件的滞回曲线和骨架曲线,分析节点的荷载特征值、延性、耗能和刚度退化。试验结果表明:3个试件的破坏均发生在梁端,节点核心区均没有破坏,满足“强节点弱构件”设计要求;试件滞回曲线饱满,延性系数均大于3.6,黏滞阻尼系数均大于1.5,具有良好的抗震性能;降低螺栓等级能提高节点刚度,但对节点承载力影响有限;增大轴压比时,刚度显著提高,但延性和耗能能力有所降低。在试验结果的基础上,采用ABAQUS对节点进行参数化分析,得出不同参数变化对节点力学性能影响,使试验更有对比性、分析更全面、结论更准确。

扩孔型T型钢梁柱连接节点抗震性能分析

高强螺栓连接的钢梁柱节点可通过增大螺栓孔的方式延续耗能来提升节点的抗震性能,为研究扩孔T型梁柱节点的抗震性能,对4个悬臂式T型梁柱节点低周往复加载试验展开数值模拟研究,利用ABAQUS中C3D8I实体单元建立有限元分析模型,分析T型连接件尺寸、螺栓规格、梁截面尺寸对扩孔T型连接节点的滞回性能、刚度退化及耗能性能的影响规律。结果表明:扩孔后的T型节点出现明显的滑移特征,滑移过程中可以耗散大量能量,4个扩孔T型梁柱节点的耗能能力均较常规孔节点有明显提升;对于初始转动刚度较低的常规孔构件,T型节点的耗能能力相对较弱,经扩孔处理之后,节点的耗能能力提升幅度更大;由于承载力机制的先后转变,扩孔之后的构件中期承载力小于常规孔构件,后期的极限承载力基本相同。

L形钢管混凝土柱-钢梁节点的抗震性能试验研究及有限元分析

为了研究异形钢管混凝土节点的抗震性能,按照1∶2缩尺比例制作了6根L形钢管混凝土柱-钢梁节点试件。通过低周往复试验,探讨了轴压比、梁柱线刚度比和是否带楼板等因素对节点抗震性能的影响。试验结果表明:试件滞回曲线饱满,试件展现出较好的抗震性能;随着梁柱线刚度比的增大,试件的强度、刚度和延性均有所提高;随着轴压比的增大,其耗能能力也增加,但延性有所下降;此外,混凝土楼板的存在对节点承载力的影响较大。利用ABAQUS有限元软件建立有限元模型进行仿真模拟分析,结果显示,有限元计算结果与试验结果符合度较好,从而验证了有限元建模的准确性,为参数分析提供依据。

C型钢缀板柱的有限元模拟方法研究

缀板柱以其制造简便、稳定性高且价格低廉的优势,在工程钢结构中得到了广泛应用,如何准确模拟缀板与立柱之间的连接情况,是工程结构有限元模拟时的重要问题。文章采用有限元软件ANSYS,研究C型钢缀板柱中缀板与立柱之间连接情况的有限元模拟问题,通过对比单元整体建模与节点耦合建模的模拟结果,分析了节点耦合连接方法的模拟原理并提出了使用时的注意事项。计算分析表明:整体建模模拟效果较好但不便于模型修改和精细化模拟,节点耦合便于修改但需要考虑耦合方法和连接面积。文章提出的简化统一耦合方法模拟效果好,适应性强,对于工程实践中的有限元模拟工作具有一定指导意义。

新型煤矿单轨吊H型钢-轨道连接子结构受力性能研究

煤矿单轨吊辅助运输是保证矿井可持续发展和提高煤炭运输效率的关键性设备。根据不完全的数据统计,每年我国煤炭需运输约200亿t的物资和设备,其中有四分之一以上是依靠单轨吊的辅助运输进行的,但每年总会出现吊车倾覆、悬挂点断裂等事故。不断改进对单轨吊轨道的悬挂形式,以改善其安装质量,这对于矿井单轨吊辅助运输设备有着十分重要的作用。基于此,介绍了一种新型煤矿单轨吊H型钢梁-轨道连接的悬挂形式,并对节点子结构的实体单元进行了有限元分析,以此来研究其受力性能。

格栅节点加强对风积沙筋土界面力学性能的影响

在普通双向土工格栅上附加节点,可形成具有立体加筋效果的加强节点土工格栅。在普通双向土工格栅加筋风积沙拉拔试验和离散元数值模型的基础上,构建加强节点土工格栅加筋风积沙的三维离散元拉拔模型,研究加强节点排布方式、厚度、数量、相邻节点间距对筋土界面力学性能的影响。研究结果表明:在节点上侧加强、节点下侧加强和节点上、下两侧同时加强的排布方式中,上下两侧同时加厚对极限拉拔阻力和界面摩擦角的增幅最大;加强节点可优化土工格栅的加筋性能;当节点布置方式不变时,加强节点厚度和节点数量均与极限拉拔阻力增量呈现出良好的线性相关性;与普通土工格栅相比,加强节点土工格栅的剪切带范围更大,且限制土体位移的能力更强;当多个节点同时工作且相邻节点的间距较小时,相邻节点的影响区域互相重叠,使节点提供的极限拉拔阻力增量降低,产生节点群体效应;随着相邻节点的间距增大,节点影响区域的重叠范围减少,群体效应逐渐减弱。

FRP轻量化应急桥模块间连接节点力学性能研究

针对某高承载大跨径应急抢修桥梁模块间连接节点力学性能展开研究,通过试验对设计的两种结构形式(A形式、B形式)单双耳接头进行极限承载力测试。通过ANSYS建立了两种结构形式的单双耳接头数值模型并验证了模型的正确性,探究了造成两种结构形式单双耳接头力学性能差异的成因。结果表明:采用B形式的单双耳接头在不增加节点质量同时能够有效提高单双耳接头的极限承载力。单双耳被作为管材连接时,耳板在传力过程中由线性传递变为弧形传递,导致传力不均匀引起被连接件受力不均匀,最后致使节点薄弱处焊缝因应力集中而失效。B形式单双耳接头耳板根部设置非对称倒角和采用变截面过渡能有效改善节点处应力集中,提高了单双耳连接节点的力学性能和轻量化水平。

既有建筑与加装电梯的可滑移节点抗震研究

新型可滑移节点能显著提高减震效应,有效改善既有建筑加装电梯的抗震性能。本文提出的新型可滑移节点模型,利用高强螺栓、长圆孔板和橡胶垫将电梯入户平台与既有建筑进行连接,目的是通过螺栓与长圆孔板以及垫板与橡胶垫之间的摩擦进行耗能,抵抗地震作用,减小结构变形。为研究该节点的受力情况,本文设计并完成了4个试件位移加载实验,实验的主要变化参数为底座是否有橡胶以及螺栓的开孔形状。实验结果表明:传统节点的最大耗能系数为0.62,可滑移节点的最大耗能系数为1.45,螺栓开孔形状对试件的性能影响明显,增加橡胶垫使试件耗能增大,可滑移节点试件抗震能力较传统节点有所提高,充分发挥了结构的耗能能力。进一步的参数分析表明:橡胶垫和开孔形状明显影响试件的变形能力,新型可滑移节点滞回曲线比较饱满,表现出一定的“捏缩”现象,整个结构具有良好的抗震性能和耗能能力,实验结果和有限元分析结果吻合良好。

ALOF——新一代三维疲劳裂纹扩展分析软件

针对当前亟需开发能分析和评估含缺陷工程结构及装备的专业商业软件的现况,基于成熟的扩展有限元法(eXtended Finite Element Method,XFEM)和自主研发的虚节点法(Virtual Node Method,VNM),推出具有完全自主知识产权的三维疲劳裂纹扩展分析软件ALOF(Analyses Laboratory of Fracture).介绍ALOF求解断裂问题的流程及其特点:可以方便地导入完整的CAD模型及多种形式的裂纹模型,可以自动生成疏密合理的二维和三维裂纹扩展分析网格;具有丰富的失效准则库;能自动分层加密裂尖区域网格;能全自动地进行裂纹扩展计算等.与同类软件相比,ALOF更简单、更精准、更高效和更专业.利用ALOF进行的3个实际工程案例表明,ALOF能准确、高效评估任意复杂缺陷体的剩余强度和疲劳寿命.