一种新型预应力空间结构形式——弦支拱壳结构

在总结拱支网壳结构力学特点的基础上,将张拉整体的概念引入拱支网壳,提出弦支拱壳结构,较好地解决了拱支网壳结构支座反力较大,下部支承结构设计较为困难的问题。结合算例分析弦支拱壳结构的静力性能、稳定性能,得出张拉整体的引入很大程度上能减小拱支网壳结构的支座反力,且较大提高拱支网壳结构的稳定性能;对比分析弦支拱壳和拱支网壳结构的基本动力特性,得到刚度和自振频率等特性。     

铁岭体育馆的钢屋盖及大悬挑平台结构设计

铁岭体育馆工程是局部带有大悬挑平台的单层网壳结构工程。介绍了大跨度网壳的结构布置特点、静力性态分析、动力响应分析与非线性屈曲分析,同时给出鼓形节点的计算结果。结构前方有近7m的大悬挑平台且平台端部荷载较重,采用预应力悬挑梁 钢管混凝土斜柱方式承担大悬挑弯矩作用。分析方法、结果及设计方法可供类似结构的分析、设计参考。     

单层椭球形网壳考虑下部结构减震性能分析

通过大型有限元分析软件ANSYS对40m跨单层椭球形网壳结构进行研究和参数分析.模型中的下部结构采用钢筋混凝土柱,以考虑对网壳的影响,并对单层椭球形网壳是否考虑下部结构的两种计算模型进行了自振振型下的模态比较.文中提出此类网壳屈曲约束支撑的布置方式,等截面替换了网壳内的部分杆件,并对有屈曲约束支撑单层椭球形网壳的减震性能进行分析.结果表明,下部结构对结构整体的影响不可忽略,合理布置约束屈曲支撑的网壳结构减震效果较好.     

我国新型组合壳体结构的发展与应用

钢筋混凝土薄壳结构施工时需搭设拆除临时模板,而纯钢网壳使得工程造价偏高,所以能够克服这两方面不利因素的新型组合壳体结构迅速发展起来。近年来我国学者提出并研究了7类新型组合壳体结构,对这些壳体的结构特点、截面形式、受力性能以及研究中采用的方法等进行了论述。最后对组合壳体结构的发展方向提出了一些建议。     

K6型单层球面网壳的自振特性分析

选用实际工程中应用较为普遍的K6型单层球面网壳作为重点研究对象，计算了多种工况（不同的矢跨比、荷载、支座条件）对网壳结构自振特性的影响，对K6型网壳结构的自振特性做了较为系统的研究，以得到K6型网壳结构的自振规律。     

基于容许位移的网壳结构稳定验算实用方法

针对网壳结构的稳定承载能力分析操作复杂且所需机时较多的不足,本文提出了一种容许位移验算方法。该方法以设计临界荷载所对应的位移值作为容许位移值,将承载能力验算转换为位移验算,然后以容许位移值来校核网壳结构的稳定设计。以K8型单层球面网壳为例,展现了该方法的具体实现过程。实例设计表明该方法操作简单,计算量小,可为网壳结构在方案设计阶段进行稳定验算提供了一种近似方法。     

一种新型后张拉整体成型网壳动力性能分析

提出一种新型后张拉整体成型局部双层球面网壳的单弦杆平板网架模型,并通过有限元软件ANSYS建立有限元模型,采用BlockLanczos法对3组缝隙值对应成型后局部双层球面网壳进行模态分析,得到网壳的自振频率和振型,并与相应成型后在单层部分环向补杆网壳进行对比分析。结果表明:成型后网壳的各阶自振频率有随成型前预留缝隙值的增大而增大的趋势;在网壳的单层部分进行环向补杆能有效提高结构刚度,使补杆网壳的各阶自振频率与非补杆网壳相比有显著提高。此外,补杆网壳与非补杆网壳都表现出复杂的动力性能,在进行网壳的动力响应分析时应特别注意。     

壳层交联单体量对中空苯丙乳胶粒性能的影响

采用交联改性的原位聚合封装非溶剂法制备了粒径分布均匀、单分散性良好的中空苯丙聚合物乳胶粒,并采用凝胶率分析、粒径分析仪、黏度计、酸值测量、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见光分光光度计、差示扫描量热分析(DSC)表征考察了壳层中交联单体用量对中空聚合物乳胶粒的合成过程、形态及其干膜遮盖性的影响.结果表明,在其他条件不变的情况下,壳层中交联单体的含量(以其占总单体质量的百分数计,下同)小于15%时,含量越低,壳层强度越低,乳胶粒致孔膨胀时易于塌陷,粒径分布越大;壳层中交联单体含量大于20%时,含量越高,壳层强度越高,乳胶粒尺寸变小,膨胀变得困难;当壳层中交联单体的含量为15%~20%时,粒径分布均匀,壳层强度适中,膨胀性较好,此时含有中空乳胶粒的干膜遮盖性能最好.     

单层杯形网壳竖向承重结构的研究应用

在常见的网壳结构中,网壳一般用做屋面结构,自支承或支承于其他结构上,而将网壳用做它承结构尚不多见.以具体工程为背景,分析单层杯形网壳作为竖向承重结构支撑楼板时的受力性能.结合网壳的几何形式,从结构概念上分析荷载传递分体系的构成,阐述整体结构的受力特点并在设计中对其进行验证.此外,对工程中两种较为特殊的鼓节点和滑动支座节...     

Investigations into stress shell characteristics of surrounding rock in fully mechanized top-coal caving face

A key issue in underground mining is to understand and master the evolving patterns of stress induced by mining, and to control and utilize the action of rock pressure. Numerical and physical modeling tests have been carried out to investigate the distribution patterns of stress in the rock surrounding a fully mechanized top-coal caving (FMTC) face. The results showed that a macro-stress shell composed of high stress exists in the rock surrounding an FMTC face. The stress of the shell is higher than its internal and external stress and the stresses at its skewback producing abutment pressure for the surrounding rock. The stress shell lies in the virgin coal and rock mass in the vicinity of the face and its sagging zone. The stress shell, which bears and transfers the loads of overlying strata, acts as the primary supporting system of forces, and is the corpus of characterizing three-dimensional and macro-rock pressure distribution of mining face. Its external and internal shape changes with the variations in the working face structure as the face advances. Within the low-stress zone inside the stress shell, another structure, i.e. voussoir beam, which only bears parts of the load from the lower-lying strata, will produce periodic pressures on the face instead of great dynamic pressure even if the beam ruptures and loses stability. The results show that the FMTC face is situated within the lower-stress zone, which is protected by the stress shell of the overlying surrounding rock. We give an explanation of lower occurrence of rock pressure on FMTC faces, and reveal the mechanical nature of the top coal of an FMTC face acting as a “cushion”. The strata behaviors of the face and its neighboring gates are under control of the stress shell. Drastic rock pressure in mine may occur when the balance of the stress shell is destruction or the forces system of the stress shell transfers.     

四类薄壳的临界荷载和失稳模态分析

本文应用非线性有限元法对球壳、扭壳、双曲扁壳和马鞍形壳在不同矢高情况下进行屈曲分析，获得了临界状态下的失稳模态和临界荷载。在此基础上找到了一些规律，供有关工程技术人员参考。     

多波多跨柱面网壳结构受力特性及简化分析方法

工程实践中可以把单波单跨的柱面网壳作为一个结构单体,在横向和纵向扩展形成单波多跨、多波单跨以及多波多跨的整体矩形平面屋盖系统。通过研究位于多波多跨柱面网壳4个不同区域的网壳单体,发现相同区域内的单体受力性能非常接近。并且依据不同区域网壳单体的约束情况建立相应的简化模型,通过分析比较简化模型和整体模型中相应单体的受力特性,可以得到二者的受力性能也比较接近。同时应用简化的单体模型考虑网壳杆件的截面选择和张弦柱面网壳中预应力设计的问题,也都能得到比较好的效果。     

网状扁壳与带肋扁壳组合结构的拟三层壳分析法

本文对网状扁壳与带肋扁壳共同工作的组合结构(可简称组合网状扁壳),采用连续化的拟三层壳的计算模型,按弹性小挠度薄壳理论进行分析计算,推导建立了混合法的基本方程式。由于这种构造上的拟三层壳在一般情况下不存在中面,因而壳体的薄膜内力、弯矩与薄膜应变,弯曲应变是耦合的,存在一个耦合矩阵,使得基本方程式比单层光面的符氏扁壳方程要复杂得多。对于周边简支的组合网状扁壳可求得基本方程式的解析解。文中对三向、四向组合网状扁壳进行了详细讨论,并指出了在特定条件下,可退化为一个当量的各向同性单层扁壳。对于一般网状扁壳的拟壳分析法及带肋扁壳的拟壳分析法分别属于本文的两种特殊情况。文中附有计算例题。     

2010年亚运会自行车馆结构设计

广州自行车馆为2010年亚运会的主要比赛场馆,屋盖采用局部双层的单层椭圆球面网壳结构。网壳通过可径向滑动球铰支座与下部混凝土结构连接,网壳周边设置封闭环形约束桁架,中间单层壳体部分利用建筑凸肋造型设置加劲桁架,解决了保证整体稳定和减小温度应力之间的矛盾,同时避免了网壳侧推力直接传递给下部混凝土结构,简化了网壳支座及下部混凝土结构的设计,节约了混凝土结构的造价。     

Junction reinforced pressurized spherical shell with a conical nozzle

In this paper, an analytical solution to the problem of a junction reinforced spherical shell with a conical nozzle under internal pressure is presented. The stresses are determined using Reissner's shallow spherical shell equations together with the solutions corresponding to the conical nozzle in terms of Bessel functions. The reinforcement and the conical nozzle are considered as an elastic discontinuity in the spherical shell causing perturbations in the undisturbed membrane state of stress in the spherical shell. After checking many limiting cases for which analytical or other solutions are available, the computer software developed is applied to a wide range of discontinuity parameters to assess their influence on the stress concentrations. Outside reinforcement is found to be more beneficial compared to inside reinforcement. The method presented is applicable to a wide range of discontinuity dimensions including those for which Esslinger's or Geckler's approximation is not applicable.     

Schalenbeulen von Sandwichzylindern mit einem neuen Elastomer als Verbundwerkstoff

Shell buckling of cylindrical sandwich shells with a new elastomer as composite material. Alternatively to cylindrical steel shells a sandwich shell with a new elastomer as composite material is investigated with regard to the stability. The sandwich shell has an inner and an outer steel face, which are bonded adhesively to an elastomer core between them. In cooperation with Krupp Stahlbau Hannover GmbH the institute for steel construction of University of Hannover checked, if the application of this sandwich technology is possible for towers of wind energy converters. Especially the combination with high strength steel is a point of interest. In comparison with numerical buckling analyses the validity of a laminate composites shell theory is proven. Finally the stability of the sandwich construction is investigated against shell buckling due to axial compression and torsion. The results are compared to the stability of cylindrical steel shells.     

Robust design of composite cylindrical shells under axial compression — Simulation and validation

Thin-walled shell structures like circular cylindrical shells are prone to buckling. Imperfections, which are defined as deviations from perfect shape and perfect loading distributions, can reduce the buckling load drastically compared to that of the perfect shell. Design criteria monographs like NASA-SP 8007 recommend that the buckling load of the perfect shell shall be reduced by using a knock-down factor. The existing knock-down factors are very conservative and do not account for the structural behaviour of composite shells. To determine an improved knock-down factor, several authors consider realistic shapes of shells in numerical simulations using probabilistic methods. Each manufacturing process causes a specific imperfection pattern; hence for this probabilistic approach a large number of test data is needed, which is often not available. Motivated by this lack of data, a new deterministic approach is presented for determining the lower bound of the buckling load of thin-walled cylindrical composite shells, which is derived from phenomenological test data. For the present test series, a single pre-buckle is induced by a radial perturbation load, before the axial displacement controlled loading starts. The deformations are measured using the prototype of a high-speed optical measurement system with a frequency up to 3680 Hz. The observed structural behaviour leads to a new reasonable lower bound of the buckling load. Based on test results, the numerical model is validated and the shell design is optimized by virtual testing. The results of test and numerical analysis indicate that this new approach has the potential to provide an improved and less conservative shell design in order to reduce weight and cost of thin-walled shell structures made from composite material.     

某工程毂节点网壳坍塌事故原因分析

某工程储罐顶盖采用了嵌入式毂节点形式的单层网壳结构,施工过程中,该网壳整体粉碎性坍塌.本文对该网壳结构的原设计进行评估,并对钢网壳无延性坍塌原因进行分析.该网壳的设计问题和事故原因具有典型的代表性,几乎涉及到规范规定的各个方面,从计算到设计,再到施工.本文对上述内容进行了全面分析.     

基于扁壳理论的半解析有限条法用于冷弯构件的屈曲分析

提出了一种基于Marguerre的扁壳理论的有限条法。现有的大多数半解析有限条法都是基于基尔霍夫和Mindlin的板理论。在本文中,该板理论可以被视为扁壳理论的特殊情况。数值分析结果证实了基于扁壳理论的有限条法的有效性。     

钢-混凝土组合薄壳屋盖的研究进展--施工阶段钢底壳的模型试验研究

钢-混凝土组合薄壳屋盖(Comshell屋盖体系)由兼作永久模板并替代钢筋的薄壁加劲钢底壳和现浇混凝土两部份组成。薄壁钢底壳由模块化单元件通过螺栓连接而成,单元件呈无盖扁盒状,由底板及周边板组成。其周边板在钢壳上构成两个方向的薄壁加劲板。这一新体系保留了混凝土薄壳屋盖的所有优点。又不需要使用临时模板．并大幅减少临时支撑。本文对这种新型结构体系及其各种可能的破坏模式进行了简单介绍,并给出了针对该结构体系施工阶段稳定性所进行模型试验的主要结果。