Performance analysis of rocking shear wall‐frame structure

Incorporating the shear deformation effect of the shear wall and the restrained moment effect of the link beam, a continuum model is presented to conduct the preliminary analysis of the rocking shear wall‐frame structure. It can be applicable to fixed/hinged systems with link beams fixed/hinged at the ends and to clamped/rocking shear wall‐frame structures with clamped/rocking shear wall at the base. Its comprehension can improve the accuracy and integrality of the analytical theory for shear wall‐frame structures. Analytical solutions to three loading scenarios are derived and make manual computation possible. A finite element with the analytical solutions as the shape functions is presented. This formulation is convenient to analyze the stepped shear wall‐frame structures with variable cross sections along the height and under complicated loads. The frequency equations and mode shapes are also derived. Numerical examples demonstrate the accuracy and excellent predictions of the present model and the finite element formulation.     

FE‐Methoden zur Bestimmung der Lage des Schubmittelpunktes dünnwandiger Querschnitte

Finite element methods for the shear centre determination of thin walled cross‐sections. The position of the shear centre can be determined using different conditions and methods respectively. The calculation for complex cross sections, which consist of many components or hollow parts, is very extensive. For that reason the application of the finite element method (FEM) is suitable. It is shown, that the calculations are similar to FEM‐investigations of beam structures.     

Untersuchungen zur Längssteifigkeit von Stahlstützen mit kastenförmigem Querschnitt

Experimental tests and theoretical analyses of longitudinal stiffness of closed cross‐sections steel columns. In structures made of thin‐walled elements it is of great importance to establish how the compressed elements change their stiffness while loading increases. Nonuniform change of longitudinal stiffness induces change of force and stress redistribution. More ductile elements take less loading and more stiff, tensed, ones are being overloaded. Columns with closed cross‐sections, box cross‐sections and hollow circular cross‐sections need to be distinguished from steel elements with longitudinal stiffness decreasing while loading increases. Shortening of column working in elastic‐plastic phase comes from material compression, cross‐section walls buckling and increased displacement of column as a whole. Imperfections that depend on fabrication process of cross‐section have a great influence on stiffness variation of an element. It can be designated, among other factors, from the equilibrium paths of tested elements. Those equilibrium paths, up to the limit point, were obtained by applying incremental method of numerical integration of equilibrium equations assuming initial displacements and residual stresses of column's walls and initial displacements of column's axes. Some numerical analyses were calculated using FEA software LUSAS. All theoretical analyses were verified by experimental tests carried out by the authors with full scale elements: box cross‐section columns – length 5280 mm, cold‐formed welded cross‐section columns – length 2000 mm. The research results and analyses by others were also used.     

某大跨异型现浇预应力混凝土空心板结构分析

为准确计算空心板结构在荷载作用下的内力和变形,对比分析了采用拟板法、拟梁法、密肋梁法等简化计算模型与有限元实体分析模型的计算结果。结果表明．混凝土空心楼盖采用填充箱体对称布置时有着很好的各向同性性能,采用拟梁法和密肋梁法计算与框架柱相连的暗梁或拟梁时,其计算结果往往偏大很多,不宜直接采用。在此基础上。并进一步探讨了预应力筋的布置原则与方法。     

Large deflection analysis of beams,pipes, or poles

This paper describes an efficient algorithm for the analysis of flexible beams, pipes or poles. The algorithm has been applied to a wide variety of offshore systems in which flexible pipes or hoses are commonly used. The method can be used to study either a complete line-like flexible structure or to develop the properties of a ‘long flexible beam element’ which can be combined with other types of elements or substructures to model complex structural systems.     

A Fiber Model Based on Secondary Development of ABAQUS for Elastic–Plastic Analysis

With the aim to provide an efficient platform for the elastic–plastic analysis of steel structures, reinforced concrete (RC) structures and steel–concrete composite structures, a program iFiberLUT based on the fiber model was developed within the framework of ABAQUS. This program contains an ABAQUS Fiber Generator which can automatically divide the beam and column cross sections into fiber sections, and a material library which includes several concrete and steel uniaxial material models. The range of applications of iFiberLUT is introduced and its feasibility is verified through previously reported test data of individual structural members as well as planar steel frames, RC frames and composite frames subjected to various loadings. The simulation results indicate that the developed program is able to achieve high calculation accuracy and favorable convergence within a wide range of applications.     

大跨度拱桥钢管拱肋悬拼中的扣索索力优化计算

钢管拱肋悬拼吊装中的扣索索力计算,采用有限元计算同优化分析相结合的方法进行逆向求解,得到各悬拼工况下索力的最优值,既控制了拱肋线形,又保证了结构内力处于安全范围内,极大地方便了施工。经实践证明该方法实用、高效。     

Eigenspannungszustände an Verbundquerschnitten infolge von Dehnungsunterschieden – Anwendung eines neueren Rechenverfahrens auf einen bewährten Lösungsansatz

Internal stress on composite cross‐sections in consequence of differing extensions – application of an modern method to an approved calculation model. Internal stress on a composite beam can be caused by differing extensions of the single parts of the composite cross‐section as they appear in consequence of unequal shrinkage or differing tem‐perature effects for instance. The calculation of the resulting conditions is a demanding problem, particularly when the single parts are jointed together by a resilient shear connection. The “Schubanalogie” is an actual method for the approximate calculation of composite cross‐sections. Its application to an approved calculation model will be shown in order to solve the mentioned problem. Finally the results will be compared to the analytical solution.     

论空间结构的形式和分类

当前空间结构的发展方兴未艾、极具活力,新的空间结构形式不断涌现。传统的空间结构分类方法有时难以适应新的发展要求。本文提出一种以空间结构组成的基本单元进行分类的新的空间结构分类方法。组成空间结构的基本单元可归纳为板壳单元、梁单元、杆单元、索单元和膜单元等五种。根据国内外已建的空间结构工程,总结了33种具体的空间结构形式,它们均可由某一种单元或某两种、三种单元构成。文中还结合近年来空间结构发展中出现的一些新结构,对新的分类方法作了说明与讨论。     

考虑翘曲变形的复合材料叠合梁几何非线性的有限元分析

提出了一个用于复合材料叠合梁结构分析的有限元模型,梁结构具有几何非线性性能,包括扭转翘曲变形。采用一个考虑了改进拉格朗日法和广义位移控制法的公式对结构的变形进行计算。采用二次等参有限单元对梁横截面进行离散化,以确定梁的弯扭特性。利用两结点的Hermitean三维有限梁元对结构进行离散化,其中每结点具有7个自由度。运用数个实例,分析了层的取向对结构性能的影响。     

A new approach for free vibration analysis of nonuniform tall building structures with axial force effects

Dynamic analysis of beam‐like structures is significantly important in modeling actual cases such as tall buildings and several other related applications as well. This article studies free vibration analysis of tall buildings with nonuniform cross‐section structures. A novel and simple approach is presented to solve natural frequencies of free vibration of cantilevered tall structures with variable flexural rigidity and mass densities. These systems could be replaced by a cantilever Timoshenko beam with varying cross‐sections. The governing partial differential equation for vibration of a nonuniform Timoshenko beam under variable axial loads is transformed with varying coefficients to its weak form of integral equations. Natural frequencies can be determined by requiring the resulting integral equation, which has a nontrivial solution. The presented method in this study has fast convergence. Including high accuracy for the obtained numerical results as well. Numerical examples including framed tube as well as tube‐in‐tube structures are carried out in the study and compared with available results in the literature, and also with the results obtained from finite element analysis in order to show the accuracy of the proposed method in the study. Obtained results indicate that the presented method in this study is powerful enough for the free vibration analysis of tall buildings.     

Ein neues FEM‐Stabelement für nachgiebige Verbundquerschnitte

A new Beam‐Finite‐Element for flexible bond in composite sections. A new Beam‐Finite‐Element is presented for an n‐part bond‐flexible composite section. With the help of the principle of virtual work the stiffness matrix of the element will be derived. The matrix composes the sum of the stiffness‐matrices of every single bar and of all the composite joints. Based on the common analytical solution of the γ‐method the new solution will be verified and validated. Finally a maximum imit of the element length will be recommended.     

Coupled stability analysis of thin-walled composite beams with closed cross-section

For the coupled stability analysis of thin-walled composite beam with closed cross-section subjected to various forces such as eccentric constant axial force, end moments, and linearly varying axial force, the efficient numerical method to evaluate the element stiffness matrix is newly presented based on the homogeneous form of simultaneous ordinary differential equations. The general bifurcation type of buckling theory for thin-walled composite box beam is developed based on the energy functional corresponding to semitangential rotations and semitangential moments. The coupled stability equations including variable coefficients and the force–displacement relationships are derived from the energy principle and explicit expressions for displacement functions are presented based on power series expansions of displacement components. The element stiffness matrix is evaluated by applying member force–displacement relationships to these displacement functions. In addition, the finite element model based on the cubic Hermitian interpolation polynomial is presented. In order to verify the accuracy and validity of this study, numerical solutions are presented and compared with the finite element solutions using the Hermitian beam elements and the available results from other researchers. Particularly, the influence of the eccentricity and the force ratio of axial forces, the fiber orientation, and the boundary conditions on the buckling behavior of composite box beam are parametrically investigated. Also the emphasis is given in showing the phenomenon of buckling mode change.     

Berechnung von Holz‐Beton‐Verbunddecken

Evaluation of Timber Concrete Composite Slabs If timber and concrete acts together in a cross section, the carrying and deformation behaviour of this new composite section is affected by many influences e.g. geometry, material properties, connecting device, long‐term behaviour, etc. The advantages of this building method and an optimization of the cross sections only can be achieved, if these influences are known and can be taken into account in the structural design. For the proof of the short term behaviour different procedures, e. g. [1], are available. Regarding the long‐term behaviour of the timber concrete composite floors it becomes obvious that the rheological behaviour of timber concrete composite structures is not considered sufficiently by the design method in [1].     

Time‐dependent analysis of steel‐reinforced concrete structures

The time‐dependent behavior is a major consideration in the design and construction of tall buildings, especially in concrete and composite structural systems. To make an analysis of long‐term effect of steel‐reinforced concrete structures, the method of using master–slave constraint to deduce substructure element model of composite members was introduced, and the problem of co‐work between steel and concrete was solved. The creep calculation method of combined Age‐adjusted Effective Modulus Method (AEMM) and finite element method was adopted. Steel Reinforced Concrete Construction Modeling (SRCCM), a calculation program based on Visual C++ and ObjectARX, was developed for simulating the construction process of high‐rise composite structures. The use of the method is illustrated through one computation example of Shanghai Center Tower, which is a super high‐rise steel‐reinforced concrete structures. The method provides valuable information about time effects that may be used in designing new structures or in diagnosis existing structures. The results also indicate that the vertical shortening of Shanghai Center Tower between column and core‐tube is significant. Such differential length changes should be compensated during the construction process of high‐rise composite structures. Copyright © 2013 John Wiley & Sons, Ltd.     

Differential Quadrature Element Method Analysis of In-Plane Deflection of Vertically Curved Beam Structures

Abstract:   The development of the differential quadrature element method (DQEM) in-plane deflection analysis model of arbitrarily curved beam structures was carried out. The DQEM uses the extended differential quadrature to discretize the differential equation defined on each element, the transition conditions defined on the interelement boundary of two adjacent elements, and the boundary conditions of the beam. Numerical results obtained from solving two structural models using a numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient.     

冷弯翼缘闭合新型截面受弯构件性能研究

空翼缘梁(Hollow Flange Beam——HFB)具有截面形式开展,抗弯、扭刚度大的特点,主要用于承受弯矩。借鉴HFB的截面形式,适当改变其截面构成及截面参数,提出两种新型冷弯翼缘点焊闭合截面——HF1和HF2。采用有限元方法,建立适于冷弯截面受弯构件性能分析的非线性有限元分析模型。模型中考虑各种影响构件承载力的因素,包括材料的强化、局部屈曲、构件失稳以及构件的初始几何缺陷。通过对新型截面的变形模式、跨中相对挠度、弯矩-曲率曲线、极限弯矩等方面的研究,全面分析两种截面构件的静力性能。分析表明,新型截面构件具有刚度大、抗弯承载力高、截面局部屈曲不易发生等优越的受力性能,可以深入试验研究并合理推广使用。     

Querschnittsberechnung von Stahlbetonstäben – Stand der Forschung

Cross‐Sectional Analysis of Reinforced Concrete Beams – State of the Art Many common structures consist of one‐dimensional members. For such structures beam theory is applicable. Within beam theory, the material behaviour can be captured on cross‐sectional level. Regarding reinforced‐concrete structures, material nonlinearity has generally to be considered. The present article provides an overview of the state of the art in cross‐sectional analysis of one‐dimensional reinforced‐concrete elements. A crosssectional analysis describes the relationship between the internal forces and the generalized strains. There is a large number of different models, for which a classification is suggested here. Existing models can be classified into resultant models, truss models, uniaxial models, wall models, and finite element models. For each class, the characteristics are outlined and the most important models are presented.     

Inelastic restrained distortional buckling of continuous composite T-beams

This paper develops a method of inelastic buckling analysis of thin-walled sections to study buckling characteristics of single span and two-span composite T-section beams in the inelastic range of structural response. The method is based on a bubble-augmented spline finite strip method, developed elsewhere by the authors, and confirmed as both accurate and efficient for the elastic buckling analysis of thin-walled structural members and plates. The method admits both flexural and membrane buckling deformations and it allows for consideration of structures with intermediate supports and a variety of boundary conditions that may be prescribed at the ends of plate assembly. The analysis includes the so-called Tendon Force Concept developed at Cambridge University for residual stresses caused by the process of fabrication, and the non-linear stress-strain properties of the structural steel from which the joist section is made. The inelastic restrained distortional buckling (RDB) of continuous composite T-section beams under transverse loading and moment gradient is investigated, and conclusions are drawn that address the influence of geometry, residual stresses, member length, the rigid restraint provided by the concrete and the degree of reinforcement in the concrete element.