Axially compressed cylindrical shells with local settlement

The design of cylindrical metal silos and tanks is often controlled by considerations of buckling under axial compression. Whilst the effects of geometric imperfections on the buckling strength have been extensively explored, few studies have explored the effects of defects in the boundary conditions and the effects of residual stresses have received even less attention.This paper investigates the initiation and development of imperfections caused by local differential settlement at the supported base and their effect on the elastic buckling of a thin cylindrical shell under axial compression. The shells were treated as initially perfect with perfect support, but developing geometric imperfections and residual stresses as a consequence of local displacement at the supported edge and with residual stresses consistent with the induced geometric imperfections.The results raise interesting questions concerning the criteria of failure and appropriate tolerance measurements for constructed cylindrical shells.     

Steel silos with different aspect ratios: I — Behaviour under concentric discharge

The current European standards for the design of thin-walled metal silos require the designer to use a complex combination of rules covering many different aspects of loading, structural behaviour and strength. Each individual rule was often developed autonomously, usually with implicit and undocumented conservative assumptions. When combined, the overall factor of safety of a designed silo may be significantly different from that guaranteed by the standard, making it difficult to reproduce the design rules in a numerical calculation that does not include the same implicit assumptions.This paper explores the behaviour of five thin-walled cylindrical silos with stepwise-varying wall thickness and aspect ratios varying from very squat to very slender, all custom-designed for and analysed under the EN 1991-4 concentric discharge loading condition. The aspect ratio plays a deciding role in both the behaviour and design of silos, and it is important to ascertain that a finding that is valid for one is transferable to the others. The nonlinear finite element analyses reveal that the computed load factor exceeds the partial safety factor in design by a large factor over a wide range of aspect ratio, suggesting that the overall design process is particularly conservative. The reasons for these discrepancies are explored.This paper is the first of a pair. The second paper explores the behaviour of the same set of example silos under the EN 1991-4 eccentric discharge loads, with fundamentally different conclusions.     

Shell element of relative degree of freedom and its application on buckling analysis of thin-walled structures

Shell element of relative degrees of freedom (SERDF) is a special transformation of solid element. It can be used in finite element (FE) analysis of both thin and thick shell structures and the formulation is simpler than normal shell elements. Introduction of additional internal degrees of freedom will improve the calculation precision.FE formulation of SERDF in the buckling analysis is derived in this article. Different measures of tackling additional internal degrees of freedom for different kinds of buckling problems and different stages of numerical analysis are presented. Some numerical examples are given to illustrate the validity of this element and the method.     

Recent developments in the design of cold-formed steel members and structures

Cold-formed steel members and structures are extremely widespread in use at the present time. The design analysis of such structures is often complex, as their behaviour can be influenced by effects, which arise due to the slenderness of members, walls and cross-sections. Prime among these effects are the various types of buckling which can occur, and which may interact with each other to promote failure at loads substantially less than those, which would be obtained in the absence of these effects. The complications induced by such effects must be taken into account in design, if the potential benefits offered by the use of such members are to be realised, and in recent design specifications this has been realised. In this paper the main types of cold-formed steel members are described, the particular characteristics affecting their design are discussed, as are the ways in which design specifications deal with these characteristics.     

Ultimate compressive strength design methods of aluminum welded stiffened panel structures for aerospace, marine and land-based applications: A benchmark study

The high strength-to-weight advantage of aluminum alloys has made it the material of choice for building airplanes and sometimes for the construction of land-based structures. For marine applications, the use of high-strength, weldable and corrosion resistant aluminum alloys have made it the material of choice for weight sensitive applications such as fast ferries, military patrol craft, luxury yachts and to lighten the top-sides of offshore structures and cruise ships. And while, over the last two decades, the ultimate limit state (ULS) design approach has been widely adopted in the design of aerospace and land-based (steel) structures, it is just recently being considered as a basis for the structural design and strength assessment of ships and offshore structures. Practical ULS methods or design codes are available in the aerospace and civil engineering industries, but they are just now being developed for use by the marine industry. The present paper compares some useful ULS methods adopted for the design of aerospace, marine and land-based aluminum structures. A common practice for aerospace, marine and civil engineering welded stiffened panel applications is discussed.     

采用不同的动力学模型对比研究扁平加劲薄壳结构的临界状态

目前大多采用Kantorovich逼近算法研究棱柱形平板和加劲薄壳结构的屈曲应力,该方法参考了Von Karman和Koiter-Sanders理论,当预测的屈曲模态涉及平面内和平面外位移的比较时,后者引入了Green-Lagrange应变张量的概念。此外,为了突出Koiter-Sanders模型的非线性特性,进一步考虑了两个中间模型,根据不同的理论方法选择了改进的Von Karman模型和伪似然模型,以简化数值计算。结果表明,至少从实用的角度看来,在所选择的3个模型的计算结果基本相同的条件下,在不能忽视平面内位移的屈曲问题中,Von Karman模型过高地估计了临界荷载。     

自复位结构的研究进展和应用现状

自复位结构拥有杰出的恢复变形能力和较好的消能能力,属于一种具有较高抗震韧性的结构类型。与其他抗震结构相比,自复位结构的突出优势在于其强震后的残余变形较小甚至为零。该特征不仅可有效保障单体结构的震后功能,而且对于整个城市的震后功能恢复具有重要意义。因此,自复位结构的研究成为了近年来地震工程领域的研究热点。通过采取不同的技术手段和关键材料,学术界提出了形式丰富的自复位结构,并开展了系统的理论分析、室内试验、数值模拟和设计方法研究。与此同时,国内外已有多个自复位结构的实际工程案例。鉴于此,该文评述自复位结构的研究进展和应用现状,总结已经取得的重要成果和关键技术,展望自复位结构在将来的研究方向和应用前景。     

The European construction industry and its competitiveness: a construct of the European Commission

The 'European construction industry' is a fiction that tends to obscure its heterogeneous character and to mar studies and policies of the European Commission aimed at improving the internal and external 'competitiveness' of the sector. In order to assess the process of integration in Europe under the impact of its own dynamics as well as Union policies, this paper looks at the dynamics of the sector from three different aspects: as investment, production and labour process. It shows, in particular, the persistent regional and social disparities dividing the industry into separate entities. Political attention tends to focus on a small number of construction companies competing for a few projects which represent the European dimension. Yet, these companies still rely on their respective national bases and local labour from the place where construction is carried out. Persistent divisions between the states are also reflected in the low level of transnational organization of the construction industry. The policy of the European Commission generally ignores these divisions and attempts to establish principles intended to make a whole sector more 'competitive', while its component parts, operating at hugely different levels of productivity, do not even meet on the same market. This paper argues that, instead of trying in vain to introduce a 'knock-out' system of competition in the EU Member States, a targeted approach might help raise productivity in lagging regions and thus improve the basis of competitiveness on global markets.     

壳体结构形态的量化重构——基于建筑参数化设计技术与结构力学的协同机制

复杂形态与结构体系之间所存在的数学逻辑与力学法则之间的偏差,构成了当今国际建筑参数化设计深化研究与面向现实实施的困境与挑战。因此,实现数字化复杂形态与结构力学逻辑的有机统一构成了该研究的初衷与最终目标。从结构工程学的角度出发,以双曲抛物面壳体为实验对象,提出了“结构原型——力学机制——力与形数字重构——验算与优化”的实验方法与创作思路,并通过圆形、三角形、菱形与编织状四种反映力学机制的肌理形式的量化试验与数据分析,论证了该技术路线的可行性与有效性,并最终形成一种从结构原型到多样性形态重塑的创新建筑设计模式。文中着力于如何利用与发掘潜在的结构力学机制,指出了复杂空间形态的创作如何结合结构力学的关键点,可为现时建筑参数化设计的现实运用与纵深研究提供实证参考与理论线索。     

浅析新欧盟标准EN15232:建筑自控与建筑管理系统对建筑能效的影响

本文对EPBD以及相关标准进行了简要介绍,并着重介绍标准EN15232。     

满足新时代大学生科研需求的关键平台:创新研修课

中美两国本科教学有着较大的区别。与美国相比，中国管理制的教学体制有利于督促学生学习，充足的课程让学生理论功底更扎实。但中国本科教学往往强调知识内容本身，而较少关注理论的实践运用，重知识传授，轻能力培养，以致学生实践能力不足。当代大学生科研热情日益高涨，越来越多的本科生期望参与科研。哈尔滨工业大学以科研优势为依托，设立"创新研修课"，受到学生欢迎。实践证明，"创新研修课"不仅为年轻教师提供了科研助手，更为本科生搭建了通往研究生继续深造的过渡桥梁。"创新研修课"已成为本科生发表SCI学术论文的创新平台，为本科生打开了参与国际交流的一扇窗。     

European Competition Policy and National Housing Policies: International Implications of the Dutch Case

This contribution explores the relationship between housing policy, which is the responsibility of national governments, and competition policy, including the decision on the legitimacy of state support, which is the responsibility of the European Commission (EC). The paper paints a general picture of EU policy on competition and state support and describes the Dutch social housing system. Attention then turns to the recent intervention by the European Commission in the governance of Dutch social housing and it is asked whether the factors that prompted the intervention exist in other EU member states as well. The analysis shows that this is indeed the case. It is concluded that the intervention of the EC in the Netherlands could become a precedent for other European countries, particularly for those countries that opt against a residualised social rented sector and for a competitive role of social housing providers on the housing market.     

Behaviour,failure and DSM design of cold-formed steel beams: Influence of the load point of application

This work presents and discusses the results of an ongoing numerical investigation on the buckling, post-buckling, collapse and design of cold-formed steel beams subjected to non-uniform bending due to transverse loadings acting away from the shear centre (either at the top or bottom flange). These results consist of (i) elastic buckling loads and modes, obtained through analyses based on Generalised Beam Theory (GBT), and (ii) elastic–plastic equilibrium paths and collapse loads, yielded by Ansys geometrically and materially non-linear shell finite element analyses. The numerical ultimate strength values are compared with their estimates provided by the current Direct Strength Method (DSM) strength curves and, on the basis of this comparison, it is possible to assess the merits of the DSM approach to design beams subjected to transverse loadings acting away from the shear centre – moreover, novel features that may improve the performance of this approach are identified.     

大剧院上下结构共同工作对钢屋盖抗震性能影响分析

河南艺术中心大剧院是屋盖为81m×108m大跨度钢结构,下部由主台、后台、观众厅三个混凝土结构单元组成的复杂结构体系。采用仅考虑上部钢结构、上下结构共同工作的整体结构、改变上下结构连接的滑动支座约束刚度等不同结构计算模型,进行小震作用反应谱分析、大震作用动力弹塑性时程分析。结果表明,下部结构刚度以及支座约束刚度对屋盖钢结构自振周期、地震作用总水平剪力、水平位移、支座反力影响均超过10%;在罕遇地震作用下对结构塑性铰分布有明显的影响。屋盖钢结构抗震安全性能设计应考虑上下部共同工作影响。     

依托“名师、名课、名专业”,打造“专业与思政”双核心课程——混凝土结构设计课程思政的探索与实践

西安建筑科技大学的混凝土结构设计课程是土木工程专业核心课程和国家首批一流本科线下课程,课程内容主要包括混凝土梁板结构、单层工业厂房结构、多高层建筑结构。在专业教育的同时,为培养学生的家国情怀、科学精神、工匠精神、法治精神、担当精神、人文素养,以更好提升学生综合素养,课程教学团队充分依托"名师、名课、名专业"三方面优势,提出专业教育与思政教育深度融合的"双核心"课程建设理念,重点开展课程思政教学体系设计、课程思政教学模式创新、课程思政案例库建设等工作,初步形成"三阶段"教师课程思政教学能力提升体系、"四要素"课程思政教学体系、"五形态"课程思政教学方式和"六模块"课程思政案例库,构建立体化的课程思政教学模式。     

Assessment of the Health and Comfort Effects of Chemical Emissions from Building Materials: the State of the Art in the European Union*

Abstract The promotion of healthier indoor air requires the use of building materials whose chemical emissions are free of toxicity and unfavourable sensory properties. Testing and assessment of chemical emissions are essential in order to identify “safe” materials, and to encourage manufacturers to produce, and the market to adopt, such materials. Various testing and assessment procedures for building materials have been developed in European countries such as Germany, Denmark, Sweden, and Finland. Recently the European Collaborative Action “Indoor Air Quality and its Impact on Man” proposed criteria and a testing procedure for the assessment of VOC emissions from solid flooring materials. The innovative aspects of this proposal are: a procedure for the performance of chemical emissions testing; sensory testing coupled with toxicological evaluation; and a procedure to handle compounds for which toxicological information is scarce or absent. This procedure, after validation and experience from practical use, will probably be extended to other building materials.     

Adding new floors to old timber-framed buildings: An assessment of demolished and preserved courtyard houses in the historic centre of Madrid

The constructive analysis of Madrid's old timber-framed collective courtyard buildings, whether demolished, preserved intact, or enlarged, has achieved the dating of relevant case studies. New parameters established in this study set a chronology based on front sector original projects: old (1737–1788), pre-modern (1788–1847) and modern (1847–1892). The on-site inspection and archival research point to ongoing misleading construction in the historic Southern area. Some modern corralas erected on top of pre-existing buildings confirm the initial hypothesis. First dimensioning rules for new façades and the stability required in old ones before adding new storeys, maintaining the original masonry or double-layered system, are discovered. Undated buildings suggest their possible origin a la malicia and a later transformation into transitional corralas. Finally, an analysis of the demolished courtyards narrows down the dating and points to new conjectures in some preserved by showing their uneven layout, old features, and structural discordances in each sector.     

Berlin and Warsaw: in search of a new role in the European urban system

After 1989, the cities of Central and Eastern Europe were engaged in an inter-urban competition, a process characteristic of the urban scene since the beginning of European integration. Being a topic of great interest to researchers, a large body of literature has accumulated on the observed role of capital cities in the region as well as on their potential role in the future. Several researchers have focused on the position as well as the interdependence of Berlin and Warsaw—two urban nodes in what is hypothesized as a future West–East development trajectory (see Domański, 1999). The present paper deals with the emergence and development of metropolitan functions in these two cities. It is based on a comparative research project, which involved a series of structured, in-depth interviews with planners and policy-makers in Germany and Poland conducted by the author during the period 2001–2003. The paper discusses the development factors and their contributions to the metropolitan potential of Berlin and Warsaw. The identification of these factors is a starting point for determining the future position and rank of these two capital cities in the European urban system. The analysis is complemented by a comparison of trends in the employment structure of Berlin and Warsaw during the period 1994–2002. The results allow the author to evaluate some hypotheses posed in strategic planning documents concerning Berlin and Warsaw.

urbanHIST: a multidisciplinary research and training programme on the history of European urbanism in the twentieth century

ABSTRACT

This paper introduces the Planning Perspectives readership to urbanHIST, a current Horizon 2020 European Joint Doctorate programme that focuses on the history of European urbanism in the twentieth century. Its concept is based on the inherent multidisciplinary approach of the research field and the ambition to gain a pan-European perspective on planning history. The paper delineates the underlying general research trends and the current responses of urbanHIST. Finally, it connects the programme's thematic orientation with both, its external contributions and its internal key activities that might bridge the gap between the protected environment of a PhD programme with the reality of academic life.