开口薄壁构件约束扭转的近似计算

在开口薄壁构件的约束扭转中，外扭矩的一部分由构件组成机件的抗弯刚度承担，另一部分由构件的抗扭刚度承担．这两部分的分配比例在不同我面是不同的，教精确计算很复杂．本文所提出的近似计算方法主要是通过特定截面的变形协调来确定此分配比例，使计算大为简化，误差亦不大，有较高的实用价值．     

冷弯薄壁型钢构件畸变屈曲研究综述与分析

对冷弯薄壁型钢构件的畸变屈曲进行了较全面的综述,介绍了畸变屈曲的特点和性能,总结了国内外畸变屈曲的研究成果,最后对畸变屈曲尚待研究的问题进行了归纳和探讨。     

冷弯薄壁型钢构件畸变屈曲试验和理论研究综述及分析

对冷弯薄壁型钢构件的畸变屈曲模式进行了较全面的综述。介绍并分析了畸变屈曲的特点和性能;总结了国内外畸变屈曲试验和理论方面的研究成果;同时还介绍了澳洲规范AS/NZS4600和北美规范NAS2004对畸变屈曲构件承载力的计算方法;最后对畸变屈曲尚待研究的理论、设计问题进行了归纳和探讨。     

冷弯薄壁型钢构件畸变屈曲研究现状

冷弯薄壁型钢开口截面构件受力过程中除出现局部屈曲和整体屈曲外,还可能出现另外一种畸变屈曲模式,畸变屈曲以及其与局部屈曲、整体屈曲的相关作用会降低构件的极限承载力,改变构件的受力性能。介绍了畸变屈曲的特点和性能,总结了国内外冷弯薄壁型钢构件畸变屈曲试验与理论研究成果,并对北美规范、澳洲规范、欧洲规范、英国规范以及我国规范关于畸变屈曲的设计计算方法进行了归纳介绍,最后在分析的基础上总结了畸变屈曲研究目前尚需解决的问题。     

绕弱轴纯弯的冷弯薄壁型钢构件畸变屈曲性能研究

采用有限条软件CUFSM对不同截面几何参数的冷弯薄壁卷边槽钢绕弱轴纯弯进行畸变屈曲应力计算,并根据经典板件屈曲应力公式计算构件翼缘畸变屈曲系数,分析构件截面几何参数的变化对畸变屈曲系数的影响,在此基础上,提出适用于求解直卷边槽钢绕弱轴纯弯畸变屈曲应力的简化公式。与有限条法和基于广义梁理论的横向弯曲铰支计算模型的计算公式进行对比,所提出的公式具有较高精度,且简单实用、便于手算,建议公式可供工程设计和修订规范参考。     

薄壁箱梁畸变的Galerkin解法

为揭示简支薄壁箱梁的畸变效应和跨内横隔板数量对箱梁畸变的影响,在改进的箱梁畸变分析理论的基础上,建立了以箱梁腹板竖向挠度为未知量的畸变控制微分方程,采用Galerkin解法进行求解。分析了矩形截面箱梁以畸变角为未知量和以腹板畸变挠度为未知量的畸变扇性坐标、畸变翘曲惯性矩之间的联系。通过算例,采用解析法研究了简支箱梁跨内横隔板数量对箱梁畸变的影响。结果表明：Galerkin解法求解箱梁跨内横隔板数量对畸变变形的影响较为直观,当箱梁在跨内设置3道横隔板时,腹板的竖向挠度可减小到不设跨内横隔板时挠度的98.84%,跨内横隔板数量多于3道时,限制箱梁畸变变形的效果并不明显;本文方法计算的箱梁畸变挠度和有限元结果较为接近,与修正后的相关文献算式计算结果吻合较好。     

约束有限条法的正交化、规一化的基对分析开口截面薄壁构件稳定性的影响

目的是解释和确定约束有限条法中不同的正交化、规一化的基对模态分解和模态识别的敏感性。有限条法为薄壁构件的变形与整体、畸变、局部屈曲,以及其他(例如:剪力和横向扩展)的区分提供了一种力学方法。对于薄壁构件的特征值屈曲分析,该方法使得与任意给定的特征模态(模态分解)得以区分,或者给定一般定义的特征值模型(模态识别)。通过建立被认可的模态识别和模态分解的方法,以完成对薄壁构件强度的预测,以及模态间相互作用的进一步研究。同样地,选用正交化、规一化的基的敏感性方法对提高薄壁构件的理解是很重要的,正如本文所示,机械定义用于区分引起整体、畸变和局部变形的向量空间,而不是区分其他(剪切和横向扩展)变形。此外,尽管该向量空间对应的基础和规范是唯一的,但对模态分解和模态识别方法有重要的影响。采用一些实例用于证明正交化、规一化的基的影响。基于如何选择正交化、规一化的基的基础上,采用约束有限条法。     

通过有限元法计算受压构件的纯畸变弹性屈曲荷载

基于有限元法,提出一个分析方法,可以计算纯畸变弹性屈曲荷载。计算中采用的有限元模型为非耦合屈曲变形模式。具体方法分为2步:第1步,采用一般梁理论(GBT)分析构件横截面,在此可以给有限元模型施加约束条件;第2步,对受约束有限元模型进行线性屈曲分析,确定纯畸变荷载。将此法应用于开口薄壁构件和冷弯构件,得到的畸变荷载非常准确,与一般梁理论和约束有限条法(cFSM)计算的荷载值一致。     

多弹性扭转支承开口薄壁杆的扭转屈曲

研究了截面形心和剪切中心重合的多弹性扭转支承开口薄壁杆在轴向压力作用下的扭转屈曲,把作用在开口薄壁杆上的弹性扭转支承去掉,代之以相应的未知扭矩,采用Laplace变换推导出了其扭转变形的位移函数,并求得了多弹性扭转支承开口薄壁杆在轴向压力作用下扭转的屈曲特征方程。     

Buckling mode identification of perforated thin-walled members by using GBT and shell FEA

The paper presents an original method based on the Generalised Beam Theory (GBT) whereby the general buckling modes, provided by the shell Finite Element Analysis (SFEA) of perforated thin-walled members, are expressed in terms of the fundamental (pure) buckling types (global, distortional and local). The contribution of each pure buckling mode to a coupled instability can be quantified, allowing a better understanding of the member buckling behaviour and post-buckling strength reserve. The main advantage of this method lies in using only the GBT cross-sectional pure deformation modes instead of member pure modal shapes. There are no restrictions regarding the element cross-sectional shape, loading and boundary conditions.     

薄壁构件弯扭失稳的一般理论

在薄壁构件的弯扭失稳问题上近20年以来存在着传统的和较新的两种不同的理论,这两种理论的并存使得一些国家的规范和一些著作出现不一致,例如我国的(GB50017—2003)和N.S.Trahair的著作犤17犦仍然采用传统理论的结果,而(GB50018—2003)、ISO的钢结构材料标准和美国的金属结构稳定设计解说却采用较新理论的结果。作者发现被忽视的横向正应力也是影响薄壁构件稳定的重要因素。本文在考虑非线性横向应变能的基础上,导出了薄壁构件的总势能方程。从板的理论出发,全面考虑微元上各种应力以及外荷载的影响,用假想荷载法导出了薄壁构件的弯扭失稳平衡微分方程。这组平衡微分方程和本文提出能量法的是一致的,这进一步证实了本文提出理论的正确性。     

Non-uniform torsion of stiffened open thin-walled members of steel structures

A general solution is derived, from distributional differential equations of equilibrium, for thin-walled structural members that are non-uniformly torsioned continuous, or situated in a Winkler rotational-elastic medium, with constant open cross-sections, stiffened with transversal ribs along their length. The equations were solved for a general case by means of the Laplace transform. Solutions were obtained in the form of closed generalized functions, holding good — for both non-uniform torsion displacements and internal forces and their influence lines — along the entire length of the bars. The effect of ribbing (diaphragms and closed ribs) on constrained torsion displacements and internal forces and on the respective influence lines is assessed for single-span and continuous I-section structural members.The results of non-uniform torsion tests carried out on I-bars stiffened along their length with battens or closed ribs (Fig. 12), in order to verify the theoretical models of the stiffened members (particularly with battens), are discussed. The test results confirmed the poor effectiveness of stiffeners in the form of battens directly joining the flanges of I-section members (Fig. 12(a)), due to the deformation of the flanges. The deformation can easily be eliminated by modifying the battens so that they join the flanges to the web (Fig. 12(b)). Tests showed that, by using the modified battens, one can effectively stiffen open thin-walled members. The effectiveness of the stiffening that is obtained is similar to that of stiffeners in the form of closed ribs.     

Buckling modes identification from FEA of thin-walled members using only GBT cross-sectional deformation modes

This paper presents the latest developments of an original method based on Generalized Beam Theory (GBT) capable to identify the fundamental deformation modes of global, distorsional or local nature, in general buckling modes provided by the shell finite element analysis (FEA) of isotropic thin-walled members. This method has the advantage of using only the GBT cross-sectional deformation modes instead of the member base mode shapes. The participation of each fundamental buckling mode can be calculated, allowing an accurate and quantitative evaluation of the coupled instability. There are no restrictions regarding the element cross-sectional shape, loading and quite recently discovered, boundary conditions.     

550MPa高强冷弯薄壁卷边槽钢受弯构件畸变屈曲试验研究

为了研究屈服强度550MPa高强冷弯薄壁型钢受弯构件的畸变屈曲性能,分别对直卷边、斜卷边和复杂卷边3种卷边形式的12组高强冷弯薄壁槽钢受弯试件进行了静力试验研究,其中纯弯试验6组,非纯弯试验6组。试验结果表明,卷边形式是影响试件发生畸变屈曲或局部和畸变相关屈曲的重要因素。相同卷边形式下,非纯弯试件的承载力均高于纯弯试件的承载力,且提高幅度与试件屈曲破坏模式有关,只发生畸变屈曲的试件承载力提高幅度最大,而在发生局部和畸变相关屈曲的试件中,由畸变屈曲引起破坏的试件承载力提高幅度次之,由局部屈曲引起破坏的试件承载力提高幅度最小。     

型钢混凝土受扭构件的非线性有限元分析

利用有限元分析软件ANSYS建立有限元模型,对型钢混凝土构件在纯扭矩作用下的整个受力过程进行了数值模拟。结果表明,有限元计算得到的极限荷载比试验值稍高,但总体上与试验值符合较好,说明利用ANSYS软件对型钢混凝土受扭构件进行数值模拟是可行的。     

考虑局部屈曲影响的H形钢构件在双向压弯作用下的滞回性能研究

由于地震作用是多维的,结构构件在地震作用下将会受到双向弯矩作用,而构件在一个主轴方向的屈服或屈曲会给构件在另一主轴方向的各项性能带来退化。针对H形截面钢构件,设计了一种由万向铰与三个跟动装置组成的三维加载系统,对11个不同宽厚比、轴压比和加载方向组配下的大宽厚比H形截面钢构件进行了双向压弯的滞回试验研究,考察了其破坏模态、滞回曲线及耗能能力等滞回性能。采用ABAQUS软件建立了有限元模型,采用试验结果进行了校核。最后基于试验和有限元分析结果,分析了扭转效应对试件的影响特性。研究结果表明,板件的局部屈曲和塑性变形的相关作用是影响试件滞回响应的重要因素,而影响效果主要取决于板材宽厚比、轴压比和加载方向的耦合作用;扭转效应对所设计的试件影响较小。     

Analysis and design reliability of axially compressed members with high-strength cold-formed thin-walled steel

High-strength cold-formed thin-walled steel has been widely used in developed countries in the last several years. However, the application and popularization of the new materials in China is still very limited, and there are no related provisions in current design codes for reference in engineering practice. In this paper, considering the effects of the variations from material strength in structural members, geometrical parameters of sections, analysis methods for limit load-carrying capacity and external loadings, the second-order moment probability method was used for conducting the design reliability analysis of 550 MPa high-strength cold-formed thin-walled steel structures, from which the reasonable target reliability index, the corresponding resistance partial coefficient and the design strength values were discussed and proposed. Existing experimental data related have been collected and used to demonstrate the suitability and reasonability of the proposed results, which shows that, with reasonable determination of the design strength value of 550 MPa high-strength cold-formed thin-walled steel sections, the effective width-to-thickness ratio method considering coupling stability of plates recommended by “Technical Code of Cold-formed Thin-Walled Steel Structures (GB50018-2002)” can be efficiently used to estimate the load-carrying capacities of the axially compressed elements of high-strength cold-formed thin-walled steel structures, and well satisfy the target reliability index in structural design.     

薄壁筒桩技术在软基处理中的应用及试验研究

以浙江省某高速公路软基处理为依托，研究了桩基工程的创新技术——薄壁筒桩的技术工艺原理以及该技术与现有各种桩基比较下所具有的特点，对其经济技术指标进行了分析，并对其软基处理效果进行了归纳，在现场试验分析研究基础上，得出薄壁筒桩应用于高等级公路软基处理效果良好的结论。