Theoretical investigation of the strength and stability of special pseudospherical shells under external pressure

The paper is devoted to a new shape of a shell of revolution with negative Gaussian curvature. The main part of the meridian of the shell is a plane curve of the Huygens tractrix. Geometrical properties of the middle surface of the shell of revolution are presented. The membrane state of stress for a family of shells with constant capacity and constant mass under uniform external pressure is analysed. The critical pressure, buckling modes and equilibrium paths for the family of shells are calculated with the use of the FEM (the ANSYS system). Results of the analytical and numerical investigations are presented in tables and figures. A stable post-critical behaviour of presented shells is pointed out which is not typical for most shell structures.     

Elastic buckling of clothoidal–spherical shells under external pressure – theoretical study

The paper is devoted to a non-typical shape of a shell of revolution with positive Gaussian curvature. The meridian of the shell is a plane curve composed of a clothoid and a circular arc. Geometrical properties of the middle surface of the shell of revolution are presented. Pre-buckling state of the shell under uniform pressure is described analytically. The critical pressure and buckling modes for the shell are calculated with the use of the FEM (the ANSYS system). Post-buckling behaviour of the shells is shown. Results of analytical and numerical investigations are presented in tables and figures.     

Recent advances in local–global FE analysis of shells of revolution

A local–global finite element technique, suitable for the analysis of shells of revolution with localized non-axisymmetric effects such as cracks, cutouts and column supports, is presented. Both material and geometrical nonlinearities are considered. The model combines, in a single analysis, rotational shell elements, general shell elements, and column elements. Rotational shell elements are employed in the axisymmetric portion of the shell, where the nonaxisymmetric behaviour in loading and deformation is accounted for by including appropriate Fourier harmonics. In the local zone, where deviations from axisymmetry are contained, a general isoparametric shell element is employed. Continuity of displacements between the rotational and general shell elements is achieved either by a layer of transitional elements or by a direct coordinate transformation. If the shell is supported on a discrete system of columns , a standard 3-D beam element with six degrees-of-freedom per node is deployed. This local–global approach has been applied to a wide variety of shell problems.     

建筑工程中旋转壳的优化设计

本文探讨了建筑工程中常用的旋转壳建筑形式与结构的优化问题，其中包括建筑形状的条件极值优化，结构壁厚的塑性极限满应力优化，壳体在承载时的钢筋混凝土结构整体优化等。每一种优化都给出了算例。     

Harmonic settlement effects on uniform and tapered tank shells

For economic reasons, foundations of large tanks for fluid storage tend to be shallow and may consequently suffer differential settlement under load. But these tanks are ductile and are able to tolerate limited settlement without distress. For an economic limitation of settlement, the structure should be analyzed rationally. In this paper, the effects of peripheral differential settlement on the shell are evaluated for the practical case of a tapering wall thickness in floating roof tanks which have a relatively flexible response to warping displacements. Previous research has centred on walls of uniform thickness, and is therefore of more limited relevance. Settlement of harmonic form is imposed at the base, and shell deformations and stresses determined in accurate finite element analysis. The significance of stresses in the primary wind girder, adjoining shell and at the bottom is assessed in relation to radial displacement at the top arising from the warping displacement. Results of recent laboratory tests particularly relevant to stress distribution are reported.     

考虑横向剪切变形厚旋转壳振动的位移型基本方程

本文基于考虑横向剪切变形的中厚旋转壳的几何方程、物理方程、中面平衡方程，建立关于五个中面位移u,v,w,Φ，Ψ为五个独立变量的中厚旋转壳振动的位移型基本方程。该方程退化为薄旋转壳、厚圆柱壳、厚圆锥壳及厚球壳振动的位移基本方程的正确性说明所推导方程具有一般性。     

高强度等边单角钢轴压构件稳定设计研究回顾与问题探讨

高强度单角钢轴压构件的稳定性能因其材料的屈服强度等力学性能改变而发生变化,因而在稳定设计及其相关研究中会遇到许多新的问题。针对这一现状,结合我国GB 50017-2003《钢结构设计规范》、美国钢结构设计规范ANSI/AISC 360-05和ASCE 10-97等三部规范,对设计规范中宽厚比限值规定的适用性、高强度角钢宽厚比限值制定的必要性、角钢构件长细比的计算,以及现有角钢轴压构件稳定计算的折减方法等问题进行了探讨和算例分析,基于稳定的基本理论和数据结果的对比分析,解释并给出了上述几个问题的确定性结论和需要注意的方面,为高强度单角钢轴压构件稳定设计方法的研究提供了参考。     

Generalised capacity curves for stability and plasticity: Application and limitations

In recent decades, the resistance of a structure has been thought of as well defined by the outcome of a geometrically and materially nonlinear analysis with explicitly modelled imperfections (GMNIA). But when this is the only analysis that is performed on a complex structural system, it is sometimes difficult to interpret the result. The outcome must be seen in the context of those from simpler analyses, which can define appropriate reference quantities.     

数字技术下壳体结构艺术的重塑——泸州沙茜体育中心建筑设计方案

该项目设计以建筑的地域性与公共性为重要出发点,探求壳体结构在空间形态塑造上与建筑形体及空间的协同方式。在明确壳体结构的力学逻辑的基础上,引入了参数化设计的技术手段,结合结构力学软件的动态、实时的计算验证,实现在双曲抛物面壳体上开洞以产生自然采光与营造戏剧性室内场景的效果。通过该项目的数字技术设计,重新发掘壳体结构在现代性语境下的空间形态表现力,企求达到结构艺术中"经济、高效、美观"的最终目标。     

Combined axial and pressure buckling of end supported shells of revolution

A reduced stiffness theoretical analysis of the imperfection sensitive elastic buckling for end supported shells of revolution is extended to the case of arbitrary combinations of axial and radial pressure loading. Depending upon the shell and loading parameters, the potential reductions in load capacity due to imperfections are shown to involve two distinct forms of post-buckling loss of stiffness. Lower bounds in each of these regimes are provided by appropriate reduced stiffness models, and shown by comparisons with available test data to be reliable even for relatively perfect test models. By attributing reductions in load carrying capacity to weakened end support conditions, it is suggested that past interpretations of these tests may have underestimated the deleterious effects of initial imperfections.     

土木工程专业基础工程课程设计的实践与改革探索

土木工程专业是一个实践性很强的工科专业,基础工程课是土木工程专业的一门公共平台课程,其课程设计是该课程的实践教学环节,目的是培养学生运用基础工程中所学的知识,并结合之前所学专业课程的知识,进行基础的设计和计算。本文介绍了土木工程专业基础工程课程设计的实践与改革工作,并对其实践与改革进行了总结与展望,以期更好地达到课程设计的目的,培养大土木工程专业人才的应用能力。     

实腹圆弧钢拱的平面内稳定极限承载力设计理论及方法

拱的平面内稳定极限承载力设计一直没有成熟的规范指导。本文用有限壳单元模型先分析了工形截面两铰圆弧钢拱的平面内弹性屈曲性能,与拱的经典屈曲理论作了对比,指出了必须同时考虑长细比和矢跨比对屈曲荷载的影响。然后分析了两铰圆弧钢拱受静水压力和其它荷载作用下的弹塑性屈曲性能,指出了典型破坏机理为拱两侧1/4跨附近形成塑性铰导致结构失效。利用拱的弹性屈曲荷载定义了拱的正则化长细比,用Perry-Robertson公式的形式,建立了拱的稳定系数与正则化长细比的关系,提出了受静水压力的两铰圆弧钢拱的平面内稳定极限承载力设计方法,并用轴力和弯矩的两项相关公式提出了受其它荷载作用下的平面内稳定极限承载力设计方法。     

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。     

土动力学与土工抗震研究进展综述

综述当前国内外土动力学与土工抗震方面的研究进展,包括土体动力特性与本构关系、土工地震反应分析、土体动力测试、土体振动液化、土体地震永久变形、交通荷载作用下土体动力特性和土工抗震措施等内容。对各种方法的优缺点进行比较和评述。进一步阐述今后的研究方向。     

钢结构稳定问题概述

介绍了钢结构稳定问题的基本概念和类型，分析了各种因素对结构和构件稳定性能的影响，总结了钢结构稳定设计的特点，从而使钢结构稳定理论设计不断完善。     

Loss of stability of thin, elastic, strongly convex shells of revolution with initial imperfections, subjected to uniform pressure. A probabilistic approach

This paper presents an attempt to evaluate theoretically the influence of initial geometric imperfections in the shell surface on the value of the upper critical load of a strictly convex shell of revolution which is subjected to uniform pressure. Pogorelov's geometric method for nonlinear stability problems of thin shells is applied to obtain an analytical formula for the upper critical load, dependent on the initial imperfections. A probabilistic solution of the problem is presented. As a result, the stochastic influence of the initial deviations in the shell surface on the probability density function of the critical load and on the shell reliability are estimated and presented graphically. An example is given for an ellipsoidal shell of revolution.     

美国、欧盟及中国钢结构设计规范中柱子曲线的对比

通过对比美国规范AISC360-05,欧盟规范EN1993以及我国规范GB50017关于轴压构件整体稳定设计的相关规定,发现AISC360-05因采用单一柱子曲线,因而不能充分考虑残余应力等因素对整体稳定承载力的影响;EN1993和GB50017分别采用5条和4条柱子曲线,因而较为科学;GB50017规定的整体稳定系数对大多数截面而言高于EN1993,但由于GB50017采用的抗力分项系数较低,其预测的承载力设计值仍低于EN1993和AISC360-05。     

Lateral buckling of web-tapered I-beams: A new theory

This paper presents a new theory for the lateral buckling of web-tapered I-beams. Linear analysis is first conducted by taking account into the tapering effects of web-tapered I-beams, where the deformation compatibilities of the two flanges and web are considered in terms of the basic assumptions of thin-walled members. Subsequently, the total potential for the lateral buckling analysis of web-tapered I-beams is developed, based on the classical variational principle for buckling analysis. The lateral buckling loads of web-tapered cantilevers and simply supported beams of I-sections from the proposed theory are compared with those from the finite element (FE) analyses using two shell element models and two widely used beam element models. The two beam element models respectively represent the equivalent method using prismatic beam elements and the typical tapered beam theory in existing literature. These comparisons show that the results based on the total potential proposed in this paper are more accurate in predicting the lateral buckling loads of web-tapered I-beams than those in existing theories, indicating that the theory proposed in this paper is superior to existing theories. It is also found that the equivalent method using prismatic beam elements may yield unreliable buckling loads of tapered beams.     

腹板开洞钢拱的平面内稳定极限承载力设计理论及方法

腹板开洞钢拱组合了拱和开洞构件的特性,目前在轻轨列车站篷及航站楼等的钢结构中有广泛应用。本文首先用有限壳单元分析了以工形截面腹板开洞圆弧钢拱为代表的拱的平面内弹性屈曲性能,考察了腹板孔洞的几何参数和拱本身的几何参数对屈曲荷载的影响;按照整体屈曲荷载的等效原则,把腹板开洞拱等效为由两个T形截面和缀板组成的格构式构件,并给出了格构式构件的等效截面尺寸。然后研究了各参数下的腹板开洞钢拱的弹塑性屈曲性能,定量考察了孔洞对稳定极限承载力的削弱作用,提出了腹板开洞钢拱特有的单边塑性铰的破坏机理。利用已经建立的拱的稳定系数与拱的正则化长细比的关系,根据等效构件的换算长细比,提出了受静水压力及其它荷载分布形式的腹板开洞拱的平面内稳定极限承载力设计方法。