加劲板有限元屈曲分析

本文提出了加劲板屈曲分析的等参加劲板弯曲单元。在西文的方法中，加劲松件可放在平板单元内部任意位置，而不必放在节线上，由于等参二次单元能较容易地适应曲线边界，层状板材和横向剪切变形。公式暨能应用于薄板又能适用于厚板。并给出了各种正交含可变斜交角的斜交加劲板之临界荷载和加劲参数，其结果表明与某些文章发表过结果完全一致。     

对加劲板在局部和整体弯曲作用下的后屈曲及强度的半解析分析

对经受平面内双轴及剪切荷载作用下的带缺陷加劲板的预先和后屈曲分析采用半解析方法分析。结合了Rayleigh-Ritz方法的大变形理论,可以分析板局部及整体的平衡。采用vonMises屈服标准预测的极限强度作为膜压力的破坏标准。采用Fortran程序计算的结果也被非线性有限元分析的结果证实。该法因此也适用于结构优化设计以及可靠性研究。     

横向加劲板在局部载荷作用下的稳定性分析

本文采用Ｒｉｔｚ法分析局部载荷作用下的横向加劲板的屈曲强度，板内应力则采用有限条法计算。给出了加劲肋的临界刚度比及板的最大屈曲系数的计算图表。分析结果表明，当载荷相对尺寸小于０．５，板长宽比小于１．３８时，横向加劲板比纵向加劲板具有较高的临界载荷。     

开口肋加劲板屈曲模态与临界屈曲应力分析

为更好掌握开口肋加劲板的设计计算方法,采用弹性稳定分析方法,对无纵向和横向加劲肋的四边简支板、纵向加劲肋等间距布置的四边简支加劲板、纵向和横向加劲肋等间距布置的加劲板进行屈曲模态和临界屈曲应力分析。结果表明:对于四边简支板或四边简支加劲板,临界屈曲应力与板宽、板长和板厚均有关,减小板宽和板长以及增大板厚可提高临界屈曲应力;随着加劲肋刚度比的变化,四边简支加劲板一般表现出3种屈曲模态,模态1为加劲肋与被加劲板共同发生整体屈曲,模态2为在加劲肋处形成波节,加劲肋与被加劲板发生屈曲,模态3为加劲肋为刚性加劲肋,不会发生失稳,只有被加劲板发生局部失稳;临界屈曲应力随加劲肋刚度比的增大而增大,模态1增大幅度最大,模态2次之,模态3逐步趋于定值。     

发生畸变屈曲的纵向加劲板的受压试验

采用厚4.0mm,名义屈服应力为235.0MPa的中厚钢板制作板件,并分别设置不同刚度的纵向加劲肋,对此纵向加劲板进行受压破坏试验。对发生畸变屈曲或局部与畸变相关屈曲的纵向加劲板的受压极限承载力和性能进行试验和理论研究,结果表明:临界屈曲模式主要取决于纵向加劲肋的刚度和母板的宽厚比。对于某些加劲板,局部屈曲和畸变屈曲之间的相互作用非常明显。畸变屈曲构件和局部与畸变相关屈曲构件展示了较大的后屈曲强度。研究纵向加劲板的的畸变屈曲强度曲线。采用直接强度法提出设计强度简化公式,用于考虑纵向加劲板的畸变屈曲及局部与畸变相关屈曲。将强度曲线与试验和有限元结果对比,验证了曲线的正确性。通过试验研究,得出有关纵向加劲板的屈曲性能的一些结论。     

PBL加劲型矩形钢管混凝土轴压柱局部屈曲性能分析

为研究开孔钢板连接件（PBL）加劲肋对矩形钢管混凝土轴压柱局部屈曲性能的影响,用能量法推导钢管屈曲系数计算公式,引入PBL和加劲肋相对刚度计算式并分析二者对屈曲模式的相互作用关系,讨论了PBL加劲型钢管的极限屈曲模式及其极限屈曲系数、最大相对宽厚比限值。结果表明:PBL加劲肋可明显改善钢管局部稳定性,钢管屈曲系数k随着PBL加劲肋刚度增加而增大,直至达到极限屈曲系数42.68;PBL连接件可减小板件纵向屈曲的波长,而加劲肋的影响作用与之相反;设置PBL加劲肋后,钢管的最大相对宽厚比限值可达184,并且板件屈曲后强度随宽厚比的变化曲线下降趋势减缓,强度值随着PBL刚度增加而逐渐提高。     

大跨度钢桥加劲板件板组局部弹性稳定分析

大跨度钢桥加劲板件由于板件幅面较大，一般采用正交异性加劲板件。采用新型的加劲肋一板单元分析了大跨度钢桥加劲板件板组的局部弹性稳定。针对U形加劲板提出等效的加劲板单元，讨论了等效加劲板单元等效换算板的横向分配刚度的计算方法和简化计算方法，并进行了算例验证。发现介绍的简化分析方法具有精度高，而计算空间比全真模型大大减少，故可用于大跨度钢桥加劲板件板组局部弹性稳定分析。     

参数设计法分析纵向加劲板梁在局部荷载下的弹性屈曲

研究受局部荷载的纵向加劲板梁的弹性屈曲。首先,使用有限元法,通过线性屈曲分析计算屈曲系数。其后,对可以衡量几何参数的屈曲系数进行一阶参数设计。最后,获得可以预测纵向加劲板梁屈曲系数的二阶模型。在所研究的几何参数内,与已有文献中的相似公式相比,有显著提升。     

外加盖板斜加劲薄钢板墙弹性屈曲性能分析

采用有限元软件ANSYS 15.0对多组外加盖板斜加劲薄钢板墙(CSW)模型进行弹性屈曲分析,研究盖板相似比、盖板高厚比、加劲肋高厚比及肋板刚度比等因素对CSW模型屈曲性能的影响,探讨提高CSW结构屈曲应力的方法,最终给出了CSW肋板刚度比的门槛刚度以及盖板高厚比的合理取值范围。     

纵横加劲肋钢板剪力墙弹性屈曲性能分析

运用ANSYS有限元软件对高厚比在200~800范围内的纵横加劲肋钢板剪力墙进行了弹性屈曲性能分析,以了解加劲板弹性屈曲应力对比用钢量是否有相应的增加程度,从而为纵横加劲肋钢板剪力墙屈曲性能分析提供依据。     

Analytical calculation of local buckling and post-buckling behavior of isotropic and orthotropic stiffened panels

A methodology for the analytical assessment of local buckling and post-buckling behavior of isotropic and orthotropic stiffened plates is presented. The approach considers the stiffened panel segment located between two stiffeners, while the remaining panel is replaced by equivalent transverse and rotational springs of varying stiffness, which act as elastic edge supports. A two-dimensional Ritz displacement function (pb-2 Ritz) is utilized in the solution of the local buckling problem of isotropic and laminated symmetric composite panels with arbitrary edge boundary conditions. The buckling analysis of the segment provides an accurate and conservative prediction of the panel local buckling behavior. Consequently, the developed methodology is extended in the prediction of the post-buckling response of stiffened panels of which the skin has undergone local buckling. Of high importance for the calculation of the post-buckling behavior is the selection of appropriate boundary conditions for the structural members analyzed. A comparison of the present methodology results to respective finite element (FE) results has shown a satisfactory agreement.     

椭圆形加劲钢板的屈曲强度分析

对轻质椭圆形抛物面加劲钢板屈曲性能进行数值分析,这种钢板一般作为轻质混凝土桥面、人行道和楼板的大跨度模板应用。双曲率钢板模板可能实现无需脚手架或其他支撑支架便可浇筑大跨度的混凝土构件。当工地地面空间不足以支撑脚手架,或者施工时为保证交通,在地面无法安装脚手架时,这种大跨度模板就显得尤为重要。通过在壳表面施加均布压力来模拟湿混凝土的效应,同时硬化混凝土的自重,通过在壳的表面施加均布荷载来模拟。结果显示,板的上升和面积比对模板的屈曲强度影响很大。同时进行了初步的可行性分析。     

外压作用下偏心加劲功能梯度圆柱壳的非线性屈曲和后屈曲分析

通过解析法研究外压作用下功能梯度加劲薄圆柱壳的非线性屈曲和后屈曲性能。通过其在内部的偏心环和纵梁对壳体进行加固,假定壳体和加固件的材料性能在厚度方向为连续梯度。根据VonKarman理论中的刚度法和传统的壳理论推导出基本关系和平衡方程,可更准确地选择三种关于挠曲的近似公式,且使用盖勒金法得出的显式表达式可以推测出临界荷载和后屈曲压力-挠曲曲线。数值结果显示了加固件能有效地增强壳体稳定性。     

Buckling of elastically restrained steel columns under longitudinal non-uniform temperature distribution

Columns under natural fire conditions are usually exposed to a non-uniform temperature distribution in the longitudinal direction. The motivation for this study stems from zone modeling of a compartment fire where the gas layers are artificially divided into two zones, namely the hotter upper zone and the cooler lower zone. However, for field modeling of a compartment fire, more detailed information of the temperature distribution can be obtained. Depending on the required accuracy, two different idealizations of temperature distributions are analyzed in this paper, namely linear distribution from zone modeling and piece-wise step distribution from field modeling in the longitudinal direction. Compared to a column with uniform temperature distribution, both of them represent more realistically the thermal response of a column, which experiences greater temperature with increasing height. The difference in temperature between the top and bottom ends of a column can be quite significant, particularly prior to the flashover condition. Advantage can be made of this in a performance-based approach to ascertain the stability of a column subjected to a prescribed fire size. In this paper, the stability of a pin-ended steel column under a non-uniform temperature distribution is studied. Although the formulations are based on linear elastic assumptions, the paper explores the validity aspect of the approach and shows that it can be applied to columns with a minimum slenderness ratio where plasticity is negligible. Across a section, the temperature is assumed to be uniform. Two linear elastic springs connected to the column ends simulate the axial restraints from the adjoining unheated structure. The objective is to derive closed-form solutions to enable engineers to quickly ascertain the column stability under a non-uniform temperature distribution, without recourse to finite element modeling.     

全加劲两侧开缝钢板剪力墙弹性屈曲研究

采用有限元方法对全加劲两侧开缝钢板剪力墙在面内水平荷载作用下的弹性屈曲临界荷载、屈曲模态进行了研究。对影响其弹性屈曲性能的参数进行了分析,包括两侧和中部加劲肋与墙板的刚度比、两侧和中部加劲肋宽厚比以及墙板高厚比和边长比。给出了全加劲两侧开缝钢板剪力墙加劲肋的弹性屈曲设计参考公式,为开缝钢板剪力墙的应用提供依据。     

冷弯型钢板件相关屈曲和极限承载力

冷弯型钢板件相关屈曲的精确计算十分复杂。本文基于盈亏相抵的概念导出板件约束系数的近似计算公式,比已有公式简便。经过矩形管短柱试验数据的分析,加上其他截面的现成资料,可知板件在屈曲后仍然存在相关性,确定受压极限承载力时应该计及这种相关性。     

纵向加劲板非弹性抗弯强度和刚度试验研究

为验证所提出的受压板上纵向加劲肋的最小刚度方程,对9个纵向加劲板试件进行试验研究,并确定其极限承载力。根据SSRC临界应力曲线,对试验结果与有限元分析所预测的最大强度进行比较,两者具有相当高的相关性。因此,从试验上确定了受压板上纵向加劲最小刚度方程的精度,以及修正SSRC临界应力曲线,包括塑性屈服的范围和过渡区。通过试验得出加劲板弯曲性能的一系列结论。     

A semi-analytical model for local post-buckling analysis of stringer- and frame-stiffened cylindrical panels

A fast semi-analytical model for the post-buckling analysis of stiffened cylindrical panels is presented. The panel is comprised of a skin (shell) and stiffeners in both longitudinal (stringers) and circumferential direction (frames). Local buckling modes are considered where the skin may buckle within a bay and may induce rotation of the stiffeners. Stringers and frames are considered as structural elements and are thus not ‘smeared’ onto the skin. Large out-of-plane deflections and thus non-linear strain–displacement relations of skin and stiffeners are taken into account. The displacements of skin and stiffeners are approximated by trigonometric functions (Fourier series). First, a linear buckling eigenvalue analysis is carried out and some combination of buckling eigenmodes is chosen as imperfection. Then the load history is started and the Fourier coefficients are determined by minimizing the stiffened panel's energy at each load level. A curve-tracing algorithm, the Riks method, is used to solve the equations. The present model can be used to assess the post-buckling behavior of stiffened panels, for example, aircraft fuselage sections.     

叠合梁屈曲的分析与数值研究

根据Euler-Bernouli梁与古典叠合梁理论，提出了一个分析模型，用于获得叠合梁的屈曲荷载，同时，用有限元方法验证了该模型。数值模拟采用8节点壳单元和接触对单元。对铺层方向、排列次序、铺层在宽度方向上的位置、铺层长度以及总层数等参数的影响进行了分析。研究表明，应用R2分析模型给出了比R1更精确的结果；同时发现，重要的表达方式必然包含于反对称次级迭合单元的弯曲刚度阵中；此外，叠合层的长度也影响精确性和分析预测之间的差异。但分析结果和模型值吻合很好。