锥形储罐罐底施工方法

锥形罐底施工，存在空鼓、焊接变形等难题。施工方法不当，结果会引起罐底的局部凸凹变形超标。以16000m^3单层双向子午线穹形网壳式内浮顶锥底油罐罐底安装为例，重点介绍锥形罐底安装施工方法，讲述如何有效控制空鼓，如何将变形控制在最小，并指出在施工中应注意的事项。以便在严格的质量管理模式下更快、更有效、更经济地完成罐底的安装施工任务。     

双轴对称薄壁锥形柱轴心受压的极限承载力

薄壁工字型锥形构件的性能由构件长细比和板单元宽厚比决定。本文对这种交互效应进行了理论研究。构建了一个具有几何非线性的非线性有限元模型进行计算。选取了大量具有不同宽厚比的翼缘和腹板,以及具有不同长细比的构件进行研究,归纳出较完整的极限强度-长细比曲线,和不同的破坏模式。根据设计目的得出一系列的曲线。最后,提出了锥形细长工字型构件(整个截面)的轴心极限承载力经验公式。这个方程简化了有效宽度的计算,提供更灵活的设计方法。     

钢结构有侧移组合框架的新型简化分析设计方法

欧洲规范4是针对组合构造的欧洲设计规范,在EN1994-1-1中主要涵盖了对"无侧移框架建筑"设计的讨论。因此,欧洲规范4更注重对结构部件的检查,如梁、柱、板和节点。然而,近几年,没有抗风支撑体系的高层建筑和大型工业用房普遍出现整体失稳这样的失效模式,而欧洲规范4并没对其进行详尽的介绍。最近,在Liège大学进行了密集型试验以及数值和理论研究。后者旨在不断发展的设计规则下,完善对有侧移组合框架建筑这一领域的认识。梁-柱组合节点的转动性能是重要的一个研究方面并着重对其进行了讨论。文章介绍了Liège大学对这一研究主题的研究结果。特别提出一个新型的、可以预测静态荷载下钢和组合框架极限承载因素和相关倒塌模式的简化分析模型。     

桩基础型式的探讨—倒截锥形基础的设计

本文研究构件截面形状和构件截面的优化组合,并考虑构件所承受的反向外荷载的相互抵消,推荐一种倒截锥形基础,它可大大地减少基础的内力,一般可节约基础和地基梁钢筋约40%.     

组合空腹夹层板的简化计算方法研究

组合式空腹板是一种新型的组合结构,可用于大柱网、大跨度的多层建筑.与传统结构相比,它具有自重小、跨度大、结构高度小、施工速度快等优点,因此它具有很广阔的应用前景.文章讨论组合空腹夹层板的简化计算方法,并将简化计算结果与有限元分析结果进行对比分析,分析结果表明该组合空腹板简化计算方法在实际工程运用中具有可行性.     

钢结构间接空气冷却塔设计方法研究

以国外某165m高钢结构空冷塔为设计原型,在国内已有研究成果的基础上,进一步研究国内规范条件下钢结构间接空气冷却塔结构的可行性,通过对钢结构空冷塔结构的整体屈曲分析反推结构主要受力构件计算长度系数,从而对结构实现进一步的优化;通过有限元计算软件MIDAS分别对24对、30对、36对斜柱空冷塔模型进行计算,在不影响结构整体性能的前提下,优化空冷塔结构用钢量,最终结果表明,模型结构的用钢量基本维持在5 000t左右,从而保证了钢结构空冷塔的经济性。     

1300 m~3倒锥形保温水塔的设计

介绍了新疆某厂区内倒锥形保温水塔的工程概况,采用MIDAS有限元软件,建立了该水塔的分析模型,计算了水塔的受力情况,提出了水塔的设计施工方案,满足水塔的功能要求。     

波形钢腹板PC组合箱梁发展综述及受力分析

介绍了波形钢腹板PC组合箱梁在国内外的发展概况。对这种新桥型的构造要点、结构特点进行了阐述,并着重分析了箱梁的轴向变形、弯曲应力、钢腹板的屈曲稳定性及扭转等力学特性。最后,展望了该类桥梁的应用前景。     

浅圆仓锥形现浇混凝土屋面钢桁架支撑体系施工关键技术

浅圆仓屋面为锥形现浇混凝土屋面,常规支撑体系无法满足高效施工及经济性要求,设计一种伞状钢桁架支撑体系,实现降本增效,安全可靠。通过荷载计算与有限元分析,验证支撑体系安全可靠。利用高强螺栓连接H型钢构件,采用同步提升技术整体提升。实践表明,该体系施工安全可靠、施工高效,可广泛应用于筒形结构锥形现浇混凝土屋面施工。     

平安金融中心钢-混凝土组合剪力墙设计分析

在钢筋混凝土剪力墙中两端设置型钢暗柱、中部设置钢板,形成钢-混凝土组合剪力墙结构,能充分发挥钢-混凝土组合结构优势,提高剪力墙承载力,减小截面厚度,改善结构抗震性能。采用有限元软件ABAQUS对平安金融中心核心筒区域钢-混凝土组合剪力墙进行了计算分析。结果表明,对于钢-混凝土组合剪力墙,只要构造设计合理,内埋的型钢、钢板与钢筋混凝土在达到极限承载力前是协同工作的。     

Wind pressures and buckling of cylindrical steel tanks with a conical roof

Tanks with a conical roof are studied in this paper under wind load, for a roof which is supported by rafters and columns. Buckling occurs in the form of deflections in the cylindrical shell and the buckling mode is localized in the windward region. Both bifurcation analysis and geometrically nonlinear analysis have been performed using finite element discretizations of the structure. The wind pressures have been obtained from wind tunnel experiments performed as part of the research, and have been obtained for tank geometries for which information was not previously available. The results show high imperfection sensitivity of tanks with a conical roof, and buckling loads for wind velocities in the same order as those expected to occur in the Caribbean region.     

Dynamic buckling of anchored steel tanks subjected to horizontal earthquake excitation

We investigate dynamic buckling of aboveground steel tanks with conical roofs and anchored to the foundation, subjected to horizontal components of real earthquake records. The study attempts to estimate the critical horizontal peak ground acceleration (Critical PGA), which induces elastic buckling at the top of the cylindrical shell, for the impulsive hydrodynamic response of the tank-liquid system. Finite elements models of three cone roof tanks with height to diameter ratios (H/D) of 0.40, 0.63 and 0.95 and with a liquid level of 90% of the height of the cylinder were used in this study. The tank models were subjected to accelerograms recorded during the 1986 El Salvador and 1966 Parkfield earthquakes, and dynamic buckling computations (including material and geometric non-linearity) were carried out using the finite element package ABAQUS. For the El Salvador accelerogram, the critical PGA for buckling at the top of the cylindrical shell decreased with the H/D ratio of the tank, while similar critical PGAs regardless of the H/D ratio were obtained for the tanks subjected to the Parkfield accelerogram. The elastic buckling at the top occurred as a critical state for the medium height and tallest models regardless of the accelerogram considered, because plasticity was reached for a PGA larger than the critical PGA. For the shortest model (H/D=0.40), depending on the accelerogram considered, plasticity was reached at the shell before buckling at the top of the shell.     

Design procedure for stiffened water-filled steel conical tanks

Since the collapse of the steel liquid-filled conical tank located in Fredericton, Canada in December 1990, a concern has been raised about the safety of existing tanks. In a previous investigation, it was shown that welding longitudinal stiffeners to the bottom part of hydrostatically loaded conical tanks would provide a significant enhancement to the buckling capacity of this type of shell structure. In the current study, an attempt is made to develop a simple procedure that can be used in designing stiffened conical tanks. The procedure is based on the theory of orthotropic shells and design formulae for unstiffened tanks previously developed by Vandepitte.The study is conducted numerically using an in-house developed shell element model to simulate both the walls of the tank and the stiffeners. The study considers stiffening existing tanks and the design of newly stiffened ones. As the application of the orthotropic theory depends on the ratio between the stiffener spacing and the shell thickness, limiting values for such a ratio have been evaluated and are presented graphically. The orthotropic design procedure is then described and applied in two examples involving a retrofitted as well as a newly designed stiffened conical tanks.     

Stability of combined imperfect conical tanks under hydrostatic loading

Steel conical vessels with upper cylindrical caps are widely used as liquid containments in elevated water tanks. This type of structure for containing water is referred to as “combined conical tank”. A number of catastrophic failures of combined conical tanks occurred during the past decades in various locations around the globe. Previous studies available in the literature focused on pure conical tanks, where the vessels have no upper cylindrical caps. The current study focuses on characterizing the buckling behaviour of combined conical tanks under the effect of hydrostatic pressure. The study is conducted numerically using a three-dimensional finite element model developed in-house. The effects of geometric imperfection and residual stresses as well as the variation of the geometric and material parameters on the buckling capacity of combined conical tanks are investigated. Finally, a comparison between the buckling capacities of combined and equivalent pure conical tanks is conducted.     

受焊缝缺陷影响的锥形薄壳屈曲性能研究

壳体表面的初始压力通常是在各种平板的轧制或焊接过程中产生的。提出与现行规范相关的基本设计规则非常重要。本文重点介绍壳体制作过程中由平板边缘的持续焊接造成的纵向缺陷。将14个试验试件分成2组,分别称之为SCC和DCC,并施加均匀静水压力。随着厚度由1t,2t增大到3t(t为薄壳厚度),试件出现1条或2条直线缺陷。该文得到的研究结果与国际上的规范及关于初始和整体屈曲及破坏的理论基本吻合。     

Behavior of stiffened liquid-filled conical tanks

Unreinforced steel conical-shaped containment vessels are frequently used in water tower applications. The failure of one of these structures in Fredericton, New Brunswick, Canada, several years ago, raises the question of whether there are adequate safety provisions for existing conical tanks. The aim of this investigation is to study the effect of welding rectangular-shaped longitudinal stiffeners to enhance the buckling capacity of existing conical tanks and to improve the design of new structures. The investigation is carried out numerically using an in-house developed shell element model that includes the effects of geometric and material non-linearities and accounts for geometric imperfections. The study focuses on two cases of tanks reinforced by longitudinal stiffeners in the lower region: the case of stiffeners free at their bottom edge, which would correspond to the retrofit of existing tanks; and the second having stiffeners anchored to the bottom slab of the tank, which can duplicate the situation of a new design. An extensive parametric study is conducted to assess the typical behavior of the two cases and to determine the critical imperfection shape that leads to the minimum buckling capacity of such type of stiffened shell structures. Finally, a comparison between the buckling capacity of unstiffened and longitudinally stiffened conical tanks that have the same volume of steel is conducted, revealing a major benefit of including stiffeners.     

Wind pressures and buckling of cylindrical steel tanks with a dome roof

An experimental/computational strategy is used in this paper to evaluate the buckling behavior of steel tanks with a dome roof under exposure to wind. First, wind tunnel experiments using small scale rigid models were carried out, from which pressure distributions due to wind on the cylindrical part and on the roof were obtained. Second, a computational model of the structure (using the pressures obtained in the experiments) was used to evaluate buckling loads and modes and to study the imperfection sensitivity of the tanks. The computational tools used were bifurcation buckling analysis (eigenvalue analysis) and geometrical nonlinear analysis (step-by-step incremental analysis). Geometric imperfections and changes in the buckling results due to reductions in the thickness were also included in the study to investigate reductions in the buckling strength of the shell. For the geometries considered, the results show low imperfection sensitivity of the tanks and buckling loads associated with wind speeds 45% higher than those specified by the ASCE 7-02 standard.     

A coupled finite element genetic algorithm technique for optimum design of steel conical tanks

Steel conical tanks having an upper cylindrical section and supported by a reinforced concrete shaft are widely used for water containment in elevated tanks. During the past few decades, a number of conical tanks have failed as a result of buckling of the steel vessel due to inadequate selection of the shell thickness. In the current study a powerful numerical tool that couples a non-linear finite element model and a genetic algorithm optimization technique is developed specifically for the analysis and design of steel conical tanks. The developed numerical tool is capable of selecting the set of design variables which satisfies the structure safety requirements while achieving a minimum structure weight and consequently minimum cost.     

A coupled finite element genetic algorithm for optimum design of stiffened liquid-filled steel conical tanks

In the current study an optimum design technique of stiffened liquid-filled steel conical tanks subjected to global and local buckling constraints is developed using a numerical tool that couples a non-linear finite element model developed in-house and a genetic algorithm optimization technique. This numerical tool is an extended version of an earlier one, adapted for the optimum design of unstiffened conical tanks. The design variables considered in the current study are the shell thicknesses, the geometry of the steel vessel as well as the dimensions and number of stiffeners. The developed numerical tool is capable of selecting the set of design variables that leads to optimum safe design. The analysis is conducted twice; first, case of stiffeners free at their bottom edge, which represents the case of retrofitting an existing tank. In the second case the stiffeners are assumed to be anchored to the bottom slab of the tank, which represents the situation of a newly designed tank. Finally, the optimum design of the stiffened tanks is compared to the optimum design of unstiffened tanks computed in a previous study.     

塔式起重机塔身结构设计

利用组合压杆稳定性知识分析腹杆布置形式对轴心受压构件整体稳定性的影响。在等稳定性条件下,给出塔式起重机常见塔身腹杆布置形式的用料情况,在等刚度条件下对两种典型结构形式进行设计,并利用有限元计算软件对其进行分析,得出两种结构的应力、变形及用料情况。对塔式起重机设计和塔身结构改进有一定的指导意义。