某天线罩单层穹顶网壳施工技术

某天线罩单层穹顶网壳安装的难点为天线已先行安装完成,天线区域无法搭设支架安装.施工方案考虑天线水平上口以下采用满堂脚手槊散装法,天线水平上口以上球冠部分采用地面拼装整体吊装,为防止球冠变形采用10吊点并用钢绞线加固,使穹顶上下两部分能顺利合龙.     

单层肋环型椭圆穹顶网壳整体稳定性分析

大跨网壳结构具有高度的几何非线性,结构设计一般由整体稳定性控制.本文以北京某单层肋环型椭圆穹顶网壳工程为背景,利用非线性有限元计算方法,对其整体稳定性进行了线性特征值屈曲、弹性屈曲以及弹塑性屈曲三方面的分析,并求得了它们的极限荷载.同时,还考察了钢材的屈服强度以及初始缺陷对极限荷载的影响,并将数值计算结果与拟壳法所得的设计临界荷载进行了比较,得出的结论对实际工程具有一定参考价值.     

具有随机几何缺陷的单层网壳临界荷载的确定

本提出微小初挠曲杆件的单元切线刚度矩阵。通过对随机计算所得临界荷载的分析，认为单层网壳的临界荷载近似呈正态分布。在此基础上，本给出求解随机几何缺陷下单层网壳临界荷载的迭代方法。     

带缺陷Kiewitt型单层网壳稳定分析

通过ANSYS有限元分析,研究了各种非线性因素和结构初始缺陷对Kiewitt型单层网壳稳定承载力的影响,分析结果表明,材料非线性因素对结构稳定承载力影响较大,尤其是对带缺陷结构的稳定性能影响更加明显。     

网壳结构弹塑性大位移全过程分析

单层网壳结构的稳定性不仅与结构的几何非线性有关,而且与结构的物理非线性也有很大关系。本文根据Von Misses屈服准则及Prandtl-Reuss增量关系,推导出理想弹塑性材料薄壁钢管杆件单元的增量本构关系,并用有限分割有限元法编制了计算程序。首先用此程序对近年来国外发表的一些实验和计算结果进行了验证;其次对双杆体系的弹塑性大位移全过程做了详细的描述;最后对一个具有285个单元636个自由度的单层短程线穹顶网壳做了弹塑性大位移全过程分析。结果表明,所采用的理论及计算方法是正确、可靠的;在考虑结构的几何非线性基础上,进一步考虑结构的物理非线性影响能够更全面地反映结构的非线性性能,从而为工程结构设计提供了可靠的理论分析。     

单层网壳各向初始缺陷敏感性分析

单层网壳属于缺陷敏感结构,缺陷的存在会使得结构的稳定承载力降低,以往主流的缺陷考虑方法包括一致模态缺陷法和随机模态缺陷法,且这两种方法在缺陷引入时均假定缺陷是沿各向分布的,没有对缺陷方向做出明确说明。本文在随机模态缺陷法的理论基础上,采用有限元软件ABAQUS对700余例凯威特6型网壳进行非线性稳定分析,通过对不同方向上缺陷的引入,发现网壳节点安装偏差中的竖向偏差往往起到控制作用,仅引入节点竖向安装偏差所得的稳定承载力值接近于全方向缺陷情况,且二者的非线性屈曲模态也较为相同。同时,在竖直向缺陷与水平向缺陷共同作用下,水平向缺陷的影响会被掩盖,即在已有竖向缺陷前提下再次施加水平向缺陷对稳定承载力影响不大,二者耦合时竖向缺陷会起到控制作用。     

考虑初始缺陷的单层网壳稳定性能分析

对于缺陷敏感结构往往由稳定承载力来控制极限承载力。工程中常用一致缺陷模态法来分析结构的稳定性,存在初始缺陷的结构仍然可以采用静力法或能量法进行稳定性分析,因为荷载作用下产生变形后结构还处在的平衡状态。单层网壳是缺陷敏感结构,整体稳定性随缺陷变化影响,其稳定承载力显著变化。对缺陷敏感程度受支座条件,结构形式,荷载形式及缺陷形式等因素影响。在计算弹性及弹塑性稳定承载力时,将结构的几何缺陷引入网壳结构的截面优化及设计过程中,保证结构的安全度尤为必要。     

单层网壳临界荷载的弹塑性简化解法

本文提出求解弹塑性失稳的单层网壳临界载荷的简化方法。依据纤维思想，通过修改杆件截面性质，得到考虑杆件部分屈服后的切线刚度矩阵。与一般方法相比，计算工作量大为减少。     

单层球面网壳的最不利简单动荷载分析

同时考虑了几何非线性与材料非线性,分别对简谐荷载、阶跃荷载作用下的单层球面网壳进行了最不利动荷载分析:通过变换简谐荷载的频率和阶跃荷载的持时,明确了结构动力响应与其自振特性及荷载频谱特性之间的关系,确定了何种条件下的荷载为结构最不利动荷载。结果表明:无论是水平还是竖向简谐荷载,当激励荷载频率与激励作用方向最大振型参与系数所对应的固有频率接近时,为结构的最不利动荷载;无论是水平还是竖向阶跃荷载,当荷载持时为荷载作用方向最大振型参与系数所对应的固有周期的1/2时,为结构的最不利动荷载。     

单层球面网壳结构选型优化设计

针对5种典型单层球面网壳结构型式(联方型、施威德勒型、凯威特型、三向格子型和短程线型),本文采用基于离散变量的序列两级截面优化算法对一百个不同跨度(30m~60m)、不同矢高(1/3~1/7)的网壳进行截面优化设计,在截面优化设计结果中提取选型所需的优秀样本,一个优秀样本由3部分组成:跨度,矢跨比和该跨度、矢跨比下用钢量最少的网壳结构类型;然后利用BP人工神经网络对复杂非线性映射关系的模拟能力建立网壳跨度、矢跨比与用钢量最少的网壳型式之间的映射关系,避免了结构选型优化的多维、多重非线性模型的求解困难,通过截面优化简便地实现了网壳结构的选型优化。     

Influence of Multiple Earthquakes on Single-Layer Reticulated Dome and Its Shaking-Table Test

International Journal of Steel Structures - In this paper, a primary dataset of mainshock–aftershock sequences is constructed from the Pacific Earthquake Engineering Research Center. This is...     

Study on Dynamic Behavior of Single-Layer Reticulated Dome by Shaking Table Test

International Journal of Steel Structures - Large-span space structures in the form of reticulated domes, which have developed rapidly in the last three decades, are widely used in large-scale...     

Coupling Effect of Nodal Deviation and Member Imperfection on Load-Carrying Capacity of Single-Layer Reticulated Shell

Single-layer reticulated shell is sensitive to imperfections. To clarify the effect of member imperfection, nodal deviation and their couplings on load-carrying capacity of reticulated shell, the equivalent load method (ELM) is developed in the present study to establish single-layer reticulated shell with random member imperfection, and its realization procedures in FEM package are well-elaborated. The main conclusions are summarized as follows: the proposed ELM is of high efficiency to form member imperfection in space structures. For reticulated shell only with member imperfection, the limit load is more or less influenced by member imperfection. With the increase of amplitude of member bow imperfection, limit load gradually decreases. Load-carrying capacity of reticulated shell with larger amplitude of bowed member is more sensitive to bending direction of bowed member than the one with smaller amplitude. Load-carrying capacity of the reticulated shell considered is extremely sensitive to nodal deviation. For reticulated shell with nodal deviation and member imperfection, the effect of member imperfection on load-carrying capacity is closely related to the magnitude of nodal deviation. Load-carrying capacity of shell with smaller nodal deviation is obviously affected by member imperfection, while not sensitive to member imperfection for reticulated shell with larger one. Member imperfection can be neglected when nodal deviation is large enough. Load-carrying capacity of reticulated shell is also influenced by bending angle of bowed member. On the whole, load-carrying capacity of reticulated shell with larger amplitude of member imperfection is more sensitive to bending direction than the reticulated shell with smaller one.

     

单层索网玻璃幕墙与主体结构地震响应的整体分析

点式玻璃幕墙单层索网柔性支承体系将晶莹通透的建筑玻璃和简洁细小的单层索网有机结合,成为建筑与结构设计融合经典.而当前关于单层索网点式玻璃幕墙抗震性能研究甚少,尤其是主体结构对其地震响应的影响.本文针对不同的主体结构和单层索网的耦合模型,对单独索网地震响应研究进行整体分析.分析结果表明:耦合模型的自振特性具有一定的独立局部自振特性;主体结构对单层索网的地震二次输入影响受主体结构和单层索网自振特性的影响,主要表现为二次输入频谱特性和输入幅值的不同;主体结构对单层索网的地震响应较大,可不同程度的放大或者减弱地震作用;主体结构对索网高阶振型具有激发效应.因而对现有规范玻璃幕墙设计不考虑主体结构的做法提出了挑战,为进一步研究主体结构对幕墙的影响提供参考.     

Sensitivity of Seismic Response and Fragility to Parameter Uncertainty of Single-Layer Reticulated Domes

Quantitatively modeling and propagating all sources of uncertainty stand at the core of seismic fragility assessment of structures. This paper investigates the effects of various sources of uncertainty on seismic responses and seismic fragility estimates of single-layer reticulated domes. Sensitivity analyses are performed to examine the sensitivity of typical seismic responses to uncertainties in structural modeling parameters, and the results suggest that the variability in structural damping, yielding strength, steel ultimate strain, dead load and snow load has significant effects on the seismic responses, and these five parameters should be taken as random variables in the seismic fragility assessment. Based on this, fragility estimates and fragility curves incorporating different levels of uncertainty are obtained on the basis of the results of incremental dynamic analyses on the corresponding set of 40 sample models generated by Latin Hypercube Sampling method. The comparisons of these fragility curves illustrate that, the inclusion of only ground motion uncertainty is inappropriate and inadequate, and the appropriate way is incorporating the variability in the five identified structural modeling parameters as well into the seismic fragility assessment of single-layer reticulated domes.     

索穹顶结构的初始形状确定

本文对索穹项结构的初始态确定进行了问题分类。对于曲面几何和结构预应力分布均未定的情况，给出了采用动力松弛法确定结构初始态的方法。算例表明本文方法可成功应用于索穹顶结构的初始态确定。     

摩天轮结构的缺陷敏感性分析

摩天轮结构在制造安装过程中不可避免地存在误差或初始缺陷,这些初始缺陷直接影响摩天轮结构的受力性能.然而对于不同形式的初始缺陷,摩天轮结构的敏感程度不同.通过一个工程实例分析摩天轮结构对各种几何缺陷的敏感性,归纳了摩天轮结构对不同类型初始缺陷的敏感程度,以及显著影响摩天轮结构受力性态的主要因素,并提出控制敏感缺陷的方法,为设计提供参考.     

单层球面网壳的优化分析

应用ANSYS软件优化模块,以自重最轻为目标函数,以强度、稳定性等为约束条件,并考虑了结构几何非线性的影响,对凯威特型单层球面网壳进行优化分析。然后对优化所得的网壳作了稳定性全过程分析,从而验证优化设计是可靠的。     

拉索穹顶结构的弹塑性分析

本文采用能量变分原理分析拉索穹顶结构的弹性和弹塑性内力。文中有算例以说明其应用。