Behaviors of Bellows-Like Origami Patterned Tubes with Trapezoidal Patterns

In this paper, we show one of the possibility utilizing typical origami structures for civil engineering fields such as the bridge bearing support. We numerically investigate axial spring constants and buckling behaviors of bellows-like origami tube structures. The bellows-like origami tube structures, which can be folded because of elastic deformations, work as a kind of spring. If the initial heights of the bellows-like origami tubes are less than 90% of the height of the prismatic tubes without bellows-like folded lines, the spring constants of the bellows-like tubes are very low compared with those of the prismatic tubes. The buckling loads and patterns of the bellows-like tubes vary depending on the initial heights of the tubes.     

Bifurcation Analysis of Multistory Building Frames

By assuming incompressible beams and columns in a multistory building frame, the frame may assume either a primary state equal to its underformed shape or a buckling mode when it is subjected to a set of primary axial forces that constitute the bifurcation loading. This article describes the theory and algorithm for a computer program by which the buckling load factor for a set of proportionate primary axial forces and the shape of the buckling mode may be obtained. It is shown that the buckling load factor thus obtained can be used to produce and effective length ratio for every column so that the Euler load of a pin-ended column with this effective length is identical to the actual buckling load of that column in the multistory building frame.     

Rheology of Cement Mortars with Crushed Fine Aggregates of Different Lithological Types

Crushed fine aggregates are widely used for full or partial replacement of natural sands in concretes. The crushed sands present different characteristics from the natural sand, especially if taking into account the content of microfine particle, the distribution of particle sizes, the shape features, besides the different lithological origin. From the rheological point of view, the crushed sands frequently provide mixtures with high yield stress, high viscosity, high cohesion and internal friction, which hinders its use in concrete. This study is focused on the evaluation of the rheological behavior of concrete mortar phase when using different lithological types of crushed sand in total replacement of natural sand. The lithological types surveyed were granite, calcitic limestone, dolomite limestone and mica schist. Each of these sand types was studied in two ways： in natura and with adjusted grading curve. The results show the best performance of calcitic limestone providing lower viscosities and lower yield stress in mortars.     

A Study about the Effect of Space Size on the Individual Distance

This study is the design guidelines for the living space with robots. The study can be applied to the architectural planning and focused on the basic environmental primary factor. The authors focused on space size, specifical distance from the wall in the front direction, position, and distance between an individual as factors affecting individual distance. The authors research the distances a small mobile robot moves to a six mats space compared with that toward a distances 5 m or more （space less physical factors）. The following three results were obtained： （1） The individual distance is smaller than 30 cm in both the approach angle in the experiment space of six mats; （2） The distance from the wall in the front increased, and the individual distance between a participant and a robot also increased; （3） In terms of body position, the upright positioning was clarified and the individual distance was small.     

空间梁单元切线刚度矩阵的精确分析方法

为有效进行空间刚架结构后屈曲分析,提出一种新的空间梁单元切线刚度矩阵的精确分析方法。首先用直接法建立梁单元杆端力与杆端位移的增量关系式,然后根据矩阵微分理论求出单元杆端力关于杆端位移的导数,在求导结果表达式中令杆端位移增量为0,即可得到梁单元切线刚度矩阵。对六层和二十层空间刚架结构进行了后屈曲分析。结果表明:所得的空间梁单元切线刚度矩阵具有足够精度,可有效用于大型空间刚架结构的后屈曲分析。     

Narratives of Spatial Division： The Role of Social Memory in Shaping Urban Space in Belfast

The paper examines the role of shared spaces in divided cities in promoting future sustainable communities and spaces described as inclusive to all. It addresses the current challenges that prevent such inclusiveness and suggests future trends of its development to be of benefit to the wider city community. It explains how spaces in divided cities are carved up into perceived ownerships and territorialized areas, which increases tension on the shared space between territories; the control of which can often lead to inter-community disputes. The paper reports that common shared space in-between conflicting communities takes on increased importance since the nature of the conflict places emphasis on communities＇ confidence, politically and socially, while also highlighting the necessity for confidence in inclusion and feeling secure in the public domain. In order to achieve sustainable environments, strategies to promote shared spaces require further focus on the significance of everyday dynamics as essential aspects for future integration and conflict resolution.     

某玻璃幕墙空间钢框架计算长度分析

某工程玻璃幕墙钢框架体型复杂,以斜立柱、斜梁和斜撑构成一个稳定性良好的空间框架结构。在该结构中,斜立柱和梁等关键构件的计算长度系数难以套用现行规范来确定。通过屈曲分析,研究斜撑对斜立柱和梁的稳定性的影响,并采用分片加载的方法最终确定各个构件的计算长度系数。     

GBT buckling analysis of thin-walled steel frames: A state-of-the-art report

This paper presents a state-of-the-art report on the use of Generalised Beam Theory (GBT) to assess the buckling behaviour of plane and space thin-walled steel frames. After a very brief overview of the main concepts and procedures involved in performing a GBT buckling analysis, one addresses the development and numerical implementation of a GBT-based beam finite element formulation that is able (i) to unveil local, distortional and global buckling modes, (ii) to handle arbitrary loadings (namely those causing non-uniform member internal force and moment diagrams) and (iii) to incorporate the presence of several frame joint configurations and arbitrary end and/or intermediate support conditions (including those associated with the modelling of bracing systems). In particular, one describes the procedures employed to establish the frame linear and geometric stiffness matrices – special attention is paid to the constraint conditions adopted to ensure the local displacement compatibility at the frame joints. The paper closes with the presentation and discussion of a number of numerical results that make it possible to illustrate the application and show the potential of the GBT-based approach to perform frame buckling analyses – they concern both plane and space frames. In order to validate and assess the numerical efficiency and accuracy of the GBT analyses and results (critical buckling loads and mode shapes), the frames are also rigorously analysed in the commercial code Ansys – both the members and joints are discretised by means of fine shell finite element meshes.     

波形钢腹板预应力混凝土组合箱梁桥悬臂施工中钢腹板临时支撑方案比较

在悬臂施工的波形钢腹板预应力混凝土(PC)组合箱梁桥中,为了施工安全,往往需要在钢腹板上设置一些临时性支撑结构。为了克服临时支架法需占用大量施工空间的缺点,提出一种由大刚度钢管组成的钢管支架法,该方法结构简单、空间占用小。对两种方案进行比较分析,采用三维有限元数值模拟法,分别进行静力分析和特征值计算。计算结果表明:虽然临时支架在钢-混组合箱梁桥的施工中有效,但在波形钢腹板(PC)组合箱梁桥的悬臂施工过程中并不能明显改善波形钢腹板的受力状态;而钢管支架能够有效地改善悬臂状态下波形钢腹板的受力状况。     

A new shape function for tapered three-dimensional beams with flexible connections

The principle of virtual force and concept of force interpolation is employed to develop a systematic method for deriving the shape functions for the tapered three-dimensional frame element with flexible end connections. These shape functions can be used to calculate the stiffness, geometric stiffness and consistent mass matrices of the tapered frame element with flexible connections. The formulation adopts the Euler–Bernoulli hypothesis and linear elastic material behaviour, with local buckling effects being ignored. The formulation is verified by some numerical examples on the buckling load and dynamic frequency analysis of tapered beams with rigid and flexible connections. It is shown that the systematic method developed in the paper is mostly superior in its efficiency compared with elements based on Hermitian interpolation functions.     

膜型网壳结构巨型网格结构的整体与局部稳定性研究

针对子结构为单层膜型网壳的圆柱面交叉立体桁架系巨型网格结构 ,分析了结构的构成、形体参数 ,建立了几何非线性力学模型 ,编制了相应的稳定分析程序。着重研究了整个结构的稳定性能、失稳形式 (局部失稳与整体失稳 )、局部失稳与整体失稳模态等 ,就不同的失稳形式进行了一系列的参数分析 ,研究了各参数对结构的失稳形式及极限载荷的影响 ,找出了不同跨度结构在整体与局部失稳临界状态某些参数的取值规律     

Elastic Buckling of Complete Toroidal Shells of Elliptical Cross-Section Subjected to Uniform Internal Pressure

It was predicted recently that some complete toroidal shells of elliptical cross-section would buckle when subjected to internal pressure. As yet there is no experimental evidence for this, so two independent shell buckling programs (BOSOR and INCA) were employed to calculate the internal buckling pressures for some test cases. The agreement between the results of the two programs is very good, with both programs predicting that buckling occurs.

Calculations were also carried out by using BOSOR on complete toroids having cross-sections in the form of prolate (k = a/b> 1.0) ellipses. The ranges of the parameters were: R/b = 4 and 10, b/t = 50, 100 and 200, and 1.3 < k < 2.5. The shells were assumed to be perfect, made from steel and to behave elastically. The buckling pressures and circumferential wavenumbers are given in tabular form and some are plotted graphically. The deformed shapes of some typical cross-sections prior to buckling are also illustrated, along with the buckling modes.     

Imperfection sensitivity of plate girder webs subjected to patch loading

This paper is aimed at studying the influence of initial geometric imperfections on the postbuckling behavior of longitudinally stiffened plate girder webs subjected to patch loading. A sensitivity analysis is conducted herein using two approaches (deterministic and probabilistic) in order to investigate the effect of varying imperfection shape and amplitude on both, the postbuckling response and ultimate strength of plate girders under patch loading. This sensitivity analysis is performed by means of nonlinear finite element analysis. At first, the initial shape imperfections are modeled using the buckling mode shapes resulting from an eigenvalue buckling analysis. Thereafter, the amplitude of the buckling shapes for the various modes is varied, and then introduced in the nonlinear analysis. The results show the influence of these modes and amplitudes on the resistance to patch loading.     

On the love strain form of naturally curved and twisted rods

Love proposed in 1944 [A.E.H. Love, A Treatise on the Mathematical Theory of Elasticity. Dover Publications, New York, 1944] that the nonvanishing (linear) strain components of a naturally curved and twist spatial rod, whose centroidal axis is along x and cross-section is in yz plane, can be represented nicely in the form ε_xx = e₁ + zk₂ − yk₃ε_xy = e₂ − zk₁ε = e₃ + yk₁ where e₁, e₂, e₃ are the strain components at y = z = 0 and k₁, k₂, k₃ are the curvatures. Functions e₁, e₂, e₃, k₁, k₂, k₃ depend on x alone. Mottershead [J. E. Mottershead, “Finite elements for dynamical analysis for helical rods”, International Journal of Mechanical Sciences, 22, (1980), pp 252–283], Pearson and Wittrick [D. Pearson and W.H. Witrick “An exact solution for the vibration of helical springs using a Bernoulli-Euler Model”, International Journal for Mechanical Sciences, 28, (1986), pp 83–96], Leung [A.Y.T. Leung “Exact shape functions for helix- elements”, Finite Elements in Analysis and Design, 9, (1991), pp 23–32], and Tabarrok and Xiong [B. Tabarrok and Y. Xiong, “On the buckling equations for spatial rods”, International Journal for Mechanical Sciences, 31, (1980), pp 179–192] have made use of the Love form. We shall show that the Love form is not even valid for two-dimensionally curved beams when shear deformation is considered. The fact that the differential length ds at point P, on the cross-section with distance y, z away from the centroidal axis is different from the differential length dx at point S on the centroidal axis has been neglected. In fact DS = (1 − k₃y + k₂z)dx, where k; are initial curvatures, which contribute to the strain components of the first order of curvatures.     

佛山坊塔斜柱外框结构设计

佛山坊塔造型独特,体型复杂。针对斜柱外框设计中的主要问题,如立面结构方案选型、竖向变形分析、抗风设计和构件设计等,提出了相应的解决方法和设计思路。结合建筑立面和受力性能确定外框结构布置方案;通过风洞试验得到结构设计的风荷载;基于风荷载的基本概念确定风荷载的输入方法;利用屈曲后强度对构件进行设计。可供类似工程参考借鉴。     

屈曲约束支撑在磁浮虹桥站结构设计中的应用

本文介绍了屈曲约束支撑在磁浮虹桥站结构设计中的应用.虹桥综合交通枢纽磁浮站为框架结构,因为建筑使用功能的需要,地上二层比地上一层减少了2/5的框架柱,为了减小刚度突变和满足层间位移角的要求,需要在地上二层设置支撑.屈曲约束支撑由于在小震下能够为结构提供适当的侧向刚度,在中震和大震下具有良好的耗能减震能力,因而被用来设置在虹桥磁浮站的地上二层.文章对结构设置屈曲约束支撑相对于设置普通支撑的优点进行了阐述,并且对结构设置屈曲约束支撑的设计计算进行了描述.     

交叉加劲钢板深梁弹性屈曲分析

以交叉加劲钢板深梁为研究对象,利用有限元软件ANSYS分析其弹性屈曲性能,讨论了抗弯刚度比、跨高比、钢板深梁厚度对其弹性屈曲性能的影响;考虑钢板深梁在钢框架的弯剪受力特性,根据板的经典理论建立了交叉加劲钢板深梁屈曲荷载计算公式,提出了等效屈曲系数。结果表明:交叉加劲钢板深梁的临界屈曲荷载随抗弯刚度比增大而增大,但达到门槛刚度比后,增大幅度急剧减小,得到门槛刚度比约为10;临界屈曲荷载随跨高比和板厚的减小而减小,等效屈曲系数随板厚减小而增大;等效屈曲系数与跨高比关系曲线由二次抛物线形向波浪形渐变,交叉加劲钢板深梁受力特性由剪切主导向弯曲主导过渡。     

Buckling optimization of variable thickness prismatic folded plates

This paper deals with the structural shape optimization of prismatic folded plates under buckling load consideration. Buckling loads are determined using linear, quadratic and cubic, variable thickness, C(0) continuity, Mindlin-Reissner finite strips. The whole structural optimization process is carried out by integrating finite strip analysis, cubic spline shape and thickness definition, semi analytical sensitivity analysis and mathematical programming algorithm. The objective is either the maximization of the critical buckling load or minimization of the cross-section of the prismatic folded plate with constraints on the volume and buckling loads. Several examples are included to illustrate various features of the optimization algorithm, including plates and stiffened panels.     

援巴布亚新几内亚国际会议中心玻璃采光顶整体稳定性和节点应力分析

援巴布亚新几内亚国际会议中心玻璃采光顶为圆形,跨度32m,结构为内外钢环与连系钢梁组成的空间结构。此结构受力特点类似扁壳,存在整体稳定性问题。文章利用有限元软件ABAQUS对其做了整体稳定性分析,对承受复杂应力的连接节点做了应力状态分析。分析结果表明:结构第二阶失稳模态为可能失稳模态其对应的线性屈曲特征值为8.67;全跨活荷布置下最大缺陷为跨度1/300的缺陷结构的失稳加载系数为4.0,其为线性特征值的46%。结构整体稳定承载力对初始缺陷不敏感。节点应力分析得到连接节点的材料处于弹性状态,节点是安全的。     

局部火灾下钢框架中上翼缘无侧移工字梁的极限状态计算

本文根据钢框架中工字梁在梁下局部火灾下将产生较大温度轴压力，其受力状态发生改变的事实，建立了钢框架中上器无侧移工字形梁的下器侧移失稳挠曲微分方程，应用能量法近似求解获得了验算梁下翼缘侧向稳定的计算长度，并结合我国现行钢结构设计规范建立了梁下翼侧移失稳的极限状态方程。此外，本文还建立了局部火灾下梁形成三铰机构而破坏的极限状态方程。这两个极限状态方程可直接用于钢框架工字梁的抗火设计与计算。