单层组合加肋拱支网壳的稳定性

介绍了某相贯单层组合加肋拱支网壳结构在竖向荷载及风荷载作用下的整体稳定性。采用有限元软件MIDAS,在两种荷载工况下分别进行了此网壳结构的特征值屈曲、几何非线性屈曲分析,初始缺陷对网壳结构的整体稳定性影响分析。结果表明:网壳结构对初始缺陷较为敏感,初始缺陷会明显降低结构稳定性;不同的荷载工况下,失稳的情况亦不同且网壳结构稳定临界系数随着荷载的增大而降低。     

施威德勒型单层球面网壳的固有振动特性及非线性屈曲研究

推导了施威德勒型单层球面网壳的结构动力平衡方程,分别讨论了该结构在线性和非线性情况下的特征值控制方程;对该结构进行固有振动分析,通过数值试验研究典型模型的自振频率和振型;将特征值屈曲分析的模态作为初始几何缺陷,通过几何非线性屈曲分析得到非线性屈曲荷载.结果表明:非线性特征值屈曲荷载小于相应的线性屈曲荷载,仅对该结构形式进行整体线性稳定分析是偏于不安全的,有必要进行非线性稳定分析.     

海安电视发射塔整体稳定分析

海安电视发射塔是典型的高耸结构,其结构布置不同于传统的电视发射塔,该结构只设有横杆和斜杆,没有主柱,所有的竖向荷载均由斜杆承担,因此海安电视发射塔的整体稳定显得尤为重要。本文利用ANSYS有限元软件对海安电视发射塔分别进行了特征值屈曲分析、初始缺陷屈曲分析和双重非线性分析。对比结果发现,初始缺陷对结构稳定的影响较小,材料非线性对结构稳定的影响较大,对其进行整体稳定分析时,不可忽略材料非线性的影响,为类似结构的稳定性设计提供了参考。     

大庆石油会展中心椭球形单层网壳稳定分析

本文对大庆石油会展中心椭球形单层网壳进行了全面的整体稳定分析。首先进行了线性稳定性分析,预测结构屈曲荷载的上限;然后,运用非线性有限元方法,考虑几何和材料非线性以及初始缺陷的影响,全面分析了网壳在各个工况荷载下的稳定性能,得到较准确的结果。     

武汉某体育馆大跨度圆钢管拱桁架结构稳定性分析

武汉某体育馆屋盖采用圆钢管拱桁架结构,单榀拱桁架的截面形式为倒三角形,两端支承于立体钢桁架上,该结构的整体稳定性足设计的重点.考虑完善及带缺陷结构两种情况,对单榀及多榀拱桁架子结构进行线性屈曲、几何非线性稳定及弹塑性非线性稳定分析,得到了临界荷载与位移的关系曲线.分析结果表明,初始缺陷及几何非线性对该结构的稳定承载力影响不明显,而材料非线性的影响显著,加强平面外支撑对于提高结构的整体稳定性具有重要作用.     

天津某贝壳形单层网壳整体稳定分析

对天津于家堡站房贝壳形单层网壳进行了全面的整体稳定分析。首先进行线性稳定性分析,预测结构屈曲荷载的上限;然后,运用非线性有限元方法,考虑几何非线性以及初始缺陷的影响,全面分析网壳在各个工况荷载下的稳定性能,得到较准确的结果。     

石家庄国际会展中心双向悬索结构整体稳定性分析

石家庄国际会展中心项目建筑造型新颖别致,富有艺术表现力,结构体系复杂,采用了双向悬索结构体系,其中纵向主承重采用自锚式悬索结构,横向次承重采用双层索桁架结构,传力方式特殊,为增大屋盖平面内刚度,还设有水平交叉支撑。以石家庄国际会展中心C厅结构为研究对象,进行了线性屈曲和非线性屈曲分析。研究了初始缺陷分布模式、荷载分布形式以及初始缺陷值的大小对结构整体稳定的影响。研究表明：初始缺陷的分布模式对石家庄国际会展中心结构的整体承载力影响不大;荷载分布形式对结构的整体承载力有较大的影响;初始缺陷值在结构跨度的1/300以内时,结构整体承载力损失不大,但当其增大至1/100结构跨度时,结构的整体承载力显著下降;该结构具有良好的整体稳定性,线性屈曲及双重非线性荷载因子均满足规范要求。     

非对称荷载对大跨度非规则单层网壳结构性能的影响

以某大跨度非规则单层网壳为研究背景,应用ANSYS通用有限元分析软件对网壳结构进行了建模并重点模拟了风荷载、雪荷载、温度效应等多种非对称荷载作用,进行了静力分析、特征值屈曲分析以及非线性稳定分析。得到了网壳结构在15种典型荷载组合下的内力、位移结果,分析了非对称荷载对网壳结构静力性能的影响;考虑了几何非线性、材料非线性、初始缺陷,得到了网壳结构在非对称荷载作用下的稳定系数,分析了非对称荷载对网壳结构稳定性能的影响。强调指出非对称荷载作用在大跨度单层网壳结构设计中的重要性,为大跨度非规则单层网壳设计提供参考。     

新型拉索-单层柱面网壳结构的稳定性和参数分析

为了确定新型拉索—单层柱面网壳结构从稳定平衡状态变为不稳定平衡状态的临界荷载和屈曲后性态,利用有限元分析软件ANSYS建立梁单元、杆单元和索单元的组合有限元模型,采用弧长法对新型拉索—单层柱面网壳结构在不同荷载工况下初始缺陷的非线性屈曲进行了弹性大挠度跟踪分析。通过改变结构参数、几何参数等因素,较深入地研究了该新型结构的非线性稳定性能。     

预应力损失对张弦桁架动力稳定性能的影响

以广州国际会展中心屋盖的整体空间张弦桁架结构为原型,分析预应力损失对张弦桁架动力稳定性能的影响.先对结构进行特征值屈曲分析和几何非线性后屈曲分析,得到结构失稳模态,并且分析了预应力损失对张弦桁架结构稳定的影响.随后考虑结构的材料非线性和几何非线性,在三向地震作用下对结构进行时程分析,分析预应力损失对张弦桁架动力稳定性能的影响.结果显示:预应力损失10%、20%后结构动力稳定的临界荷载有所下降但降幅不大;预应力损失30%后,结构动力稳定临界荷载有明显下降,且随着预应力的损失,结构的动力稳定性能越来越差;当预应力损失100%后结构动力稳定临界荷载下降了48.75%.     

Research on stability of single-layer inverted catenary cylindrical reticulated shells

The structural configuration and method of analysis of the single-layer inverted catenary cylindrical reticulated shell are introduced in this paper, and the elastic as well as elastic–plastic stability of this kind of reticulated shell is then investigated. The stability of the structures with different types of grid patterns is compared, and the reasonable grid pattern is hence recommended. The structural buckling mode and ultimate load-carrying capacity are studied in detail by parametric analysis. Influence of various factors on structural ultimate load is investigated, and the fitting formula of ultimate load is thus presented. Comparison analysis between the inverted catenary and circular cylindrical reticulated shells is also carried out. The work will provide guidance in theory for practical applications of this kind of structure.     

河南艺术中心艺术墙共享大厅结构体系稳定性分析

河南艺术中心40m高悬臂玻璃艺术墙采用了"单层索网次结构-平面钢管相贯桁架主体结构"体系。主体钢结构的整体稳定性设计是结构安全的控制因素。应用结构体系非线性屈曲分析方法进行结构稳定性设计,在进一步分析结构几何体系设置、关键节点约束条件、初始几何缺陷、构件材料弹塑性、荷载分布、计算子步数等各种因素对结构体系稳定性影响的基础上,采取加强措施,确保了结构安全。     

Shape optimization of aluminium alloy spherical reticulated shells considering nonlinearities

This study proposes a shape optimization method for K6 aluminum alloy spherical reticulated shells with gusset joints, considering geometric, material, and joint stiffness nonlinearities. The optimization procedure adopts a genetic algorithm in which the elastoplastic non-linear buckling load is selected as the objective function to be maximized. By confinement of the adjustment range of the controlling points, optimization results have enabled a path toward achieving a larger elastoplastic non-linear buckling load without changing the macroscopic shape of the structure. A numerical example is provided to demonstrate the effectiveness of the proposed method. In addition, the variation in structural performance during optimization is illustrated. Through parametric analysis, practical design tables containing the parameters of the optimized shape are obtained for aluminum alloy spherical shells with common geometric parameters. To explore the effect of material nonlinearity, the optimal shapes obtained based on considering and not considering material non-linear objective functions, the elastoplastic and elastic non-linear buckling loads, are compared.     

Loss-of-stability induced progressive collapse modes in 3D steel moment frames

This paper deals with the progressive collapse analysis of a tall steel frame following the removal of a corner column according to the alternate load path approach. Several analysis techniques are considered (eigenvalue, material nonlinearities, material and geometric nonlinearities), as well as 2D and 3D modelling of the structural system. It is determined that the collapse mechanism is a loss-of-stability-induced one that can be identified by combining a 3D structural model with an analysis involving both material and geometric nonlinearities. The progressive collapse analysis reveals that after the initial removal of a corner column, its two adjacent columns fail from elastic flexural-torsional buckling at a load lower than the design load. The failure of these two columns is immediately followed by the failure of the next two adjacent columns from elastic flexural–torsional buckling. After the failure of these five columns, the entire structure collapses without the occurrence of any significant plastification. The main contribution is the identification of buckling-induced collapse mechanisms in steel frames involving sequential buckling of multiple columns. This is a type of failure mechanism that has not received appropriate attention because it practically never occurs in properly designed structures without the accidental loss of a column.     

空间框架的非线性塑性分析

介绍一种纤维梁柱单元,考虑几何和材料非线性。通过轴力和弯矩作用下构件稳定方程中的稳定函数来表示几何非线性,通过跟踪横截面上各纤维的单轴应力-应变关系来模拟材料非线性。基于广义位移控制方法,采用增量迭代法求解非线性平衡方程。用1个单元模拟1根杆件,该单元的非线性性能与有限元软件分析结果及其他有效结果比较吻合,并举例证明了该单元的准确性和有效性。     

Structural stability of cable-stayed bridges during construction

This paper presents an investigation of the stability characteristics of steel cable-stayed bridges during construction. In general, cable-stayed bridges are subjected to quite large compressive forces induced by stayed cables, and may become unstable during their construction stage, due to the excessive compressive forces induced by added construction loads. To solve the structural instability problems of the bridges under construction, a nonlinear analysis program was developed based on the theory of nonlinear finite element analysis. The complex stability characteristics of cable-stayed bridges during construction were investigated through a series of rigorous geometric nonlinear analyses, including various structural nonlinearities such as cable-sag effect, beam-column effect of girder and mast, large displacement effect, and girder-mast-cable interaction. To consider the construction characteristics of the cable-stayed bridges, a three-step analysis method is proposed, and used in the present study. In addition, the effects of various cable-arrangement types and girder-mast stiffness ratios on the stability characteristics were extensively investigated. Typical buckling modes can be classified into two categories, depending on the location of critical member or members.     

Nonlinear static and cyclic analysis of concrete-filled steel columns

This paper presents the formulation of a one-dimensional (1D) composite frame element for the nonlinear static and cyclic analysis of concrete-filled steel (CFS) beam-columns. A two-node frame element is formulated using the force interpolation concept, and the material nonlinearity at section level is taken into account by employing a total secant stiffness and modified fibre element approach. The size effect and steel tube confinement on the concrete strength and ductility are taken into account. Further, the effect of steel tube local buckling on the member strength is addressed. Concerning geometrical nonlinearities at the element level, the equilibrium equations are satisfied for the deformed element to take account of P-Δ effects. The formulation accuracy and efficiency of the model are verified by some numerical examples of the static and cyclic analysis of CFS members.