钢-聚氨酯夹层板稳定分析

分别建立了钢-聚氨酯夹层板和普通钢板的有限元模型,在边界条件、加载情况均相同的条件下进行有限元稳定分析,夹层板采用板-实体-板结构模拟,结果表明在相同条件下,夹层板比普通钢板的屈曲强度均有较大程度的提高。同时进行了保持一定条件不变,分别改变夹芯层厚度、面层钢板厚度模拟分析,结果表明在一定范围内,夹芯层厚度与钢面板厚度增大,夹层板的屈曲临界荷载值也随之增大。夹芯层的抗弯刚度和横向剪切变形对板的影响不可忽略。     

格构增强型泡沫夹层结构腹板剪切屈曲分析

基于双参数地基模型,分析了格构式增强型泡沫夹层结构的腹板在纯剪作用下的弹性稳定问题,讨论了泡沫芯材的存在对夹层结构腹板剪切稳定的影响规律、该理论分析模型的适用条件,通过有限元方法验证了该模型分析结果的合理性。分析表明,泡沫芯材的存在可以有效提高腹板的剪切稳定性能。即使芯材弹性模量较低,其提供的剪切刚度对于腹板的稳定也有着重要意义。随着腹板高厚比和芯材弹性模量的增加,泡沫对腹板提供的法向刚度控制作用越明显。芯材厚度是该模型结果准确与否的重要前提。从工程实用的角度,腹板区格的长高比对腹板剪切稳定的影响可以忽略不计。     

Influence of weld stiffness on buckling strength of laser-welded web-core sandwich plates

This paper investigates the influence of weld rotation stiffness on the global bifurcation buckling strength of laser-welded web-core sandwich plates. The study is carried out using two methods, the first is the equivalent single-layer theory approach solved analytically for simply supported plates and numerically for clamped plates. First-order shear deformation theory is used. The second method is the three-dimensional model of a sandwich plate solved with finite element method. Both approaches consider the weld through its rotation stiffness. The weld rotation stiffness affects the transverse shear stiffness. Plates are loaded in the web plate direction. Four different cross-sections are considered. Weld stiffness is taken from experimental results presented in the literature. The results show a maximum of 24% decrease in buckling strength. The strength was affected more in plates with high reduction of transverse shear stiffness and high bending stiffness. Furthermore, clamped plates were influenced more than simply supported. The intersection between buckling modes shifted towards higher aspect ratios, in the maximum case by 24%. The results show the importance of considering the deforming weld in buckling analysis.     

Tension buckling and parametric instability characteristics of doubly curved panels with circular cutout subjected to nonuniform tensile edge loading

This paper deals with the study of tensile buckling, vibration, and parametric instability behaviour of doubly curved panels with central circular cutout subjected to uniaxial in-plane partially distributed tensile edge loadings using finite element method. First order shear deformation theory is used to model the curved panels, to consider the effects of the transverse shear deformation and rotary inertia. The vibration analysis for this problem shows that for certain parameters of the tensile loading, the frequencies of the panel initially rise with the load, but begin to decrease with increasing tension, showing the onset of tension buckling. The parametric instability behaviour under tensile periodic edge loading with different load parameters shows that instability regions are influenced by the cutout size, load width and its location.     

Shear buckling strength and design of curved corrugated steel webs for bridges

This paper presents the shear buckling strength and design of curved corrugated steel webs for bridges considering material inelasticity. The inelastic buckling strength is determined from buckling curves based on the proposed shear buckling parameter, which is a function of the elastic shear buckling strength of steel web and the material shear yielding strength. A finite element analysis is carried out to study the geometric parameters affecting the shear buckling strength of curved corrugated steel webs for bridges. Based on the numerical results, a shear buckling parameter formula is proposed with no need to calculate either local, global, or interactive buckling parameters. But it depends on the geometric properties of the curved corrugated web profile. Another formula is presented to maximize the shear buckling capacity of curved corrugated web. The proposed formulae agreed well with the published experimental data. The curved corrugated webs produce a tremendous increase in the shear buckling strength and considerable weight saving in regard to the corresponding trapezoidal corrugated webs. The corrugation angle has a considerable effect on the behavior of curved corrugated webs, where higher corrugation angles produce a tremendous increase in the shear buckling strength of curved corrugated webs. It was found that the proposed approach provides a good prediction for the shear buckling strength of curved corrugated steel webs of bridges.     

Effect of moment of inertia on elastic stability of rectangular webs for thin-walled beams under a transverse load

So far, the equations for buckling capacity of web panels focus on thin-walled beams with very strong flanges. In this paper, elastic buckling behavior of web panels of thin-walled beams with weak flanges is further studied, aiming at a buckling coefficient formula unifying the effect of both weak and strong flanges. A new parameter, the flange-to-web ratio of moment of inertia, is proposed to characterize the effect of flanges. Then, a semi-analytical method is applied to investigate the buckling behavior of simply supported web panels, in two cases, inclusive or exclusive of effect of the moment of inertia of flanges. It is revealed that elastic buckling load, in particular, the buckling coefficient of web panel is a function of two key parameters, web aspect ratio and flange-to-web ratio of moment of inertia. Meanwhile, a finite element analysis (FEA) model allowing for the sensitivity of boundary conditions is validated by comparing with the semi-analytical solution to the case exclusive of effect of the moments of inertia of flanges. Next, numerical results are utilized to illustrate the influence of the previous parameters, which verify the increase of buckling coefficient with flange-to-web ratio of moment of inertia or the decrease of buckling coefficient with web aspect ratio. Besides, it also verifies that for the same flange-to-web ratio of moment of inertia, the buckling behavior of square web panels is closer to the uniform shear buckling than other rectangular web panels. Finally, an accurate design formula is proposed to calculate buckling coefficient of web panel.     

Basic parametric study on corrugated web girders with cut outs

This paper presents a basic parametric study on steel girders with trapezoidally corrugated webs having cut outs. A finite element analysis is carried out to investigate the effect of cut outs in corrugated webs. This FE-modelling is conceived in ANSYS because of the program’s significant capability to account for the web stresses and out-of-plane buckling failure modes. The Finite element model of corrugated web plates is calibrated with theoretical study and finally a parameter study with a scope of application of cut outs in girders with corrugated web plates is performed. This procedure includes the influence of web height, length of parallel part, depth of corrugation, web configuration, location of cut out and its diameter. The analytical study shows that the influence of geometry of corrugated sheets with cut outs on the load capacity and buckling behaviour of the girder can be significant. With the help of the finite element model, the eigenvalue buckling analysis is carried out for all parameter combinations. The local buckling coefficients and the accompanying failure mechanisms are determined for several heights of web and for a wide range of the horizontal eccentricity of the cut out. With the help of this numerical research, design specifications are recommended in line with Eurocode 3.     

波浪腹板连接的双核防屈曲支撑承载力及滞回性能研究

提出一种用波浪腹板连接的双内核防屈曲支撑(简称CW-BRB)。CW-BRB由浪腹板连接两个内置一字板 内核的全钢约束矩形钢管组成,且两个一字板内核在伸出外围约束构件端头前后均通过肋板加强形成H形截面 ,整体外围约束的抗弯刚度及内核端部强度均获得极大改善,承载力设计效益显著提高。首先,简要介绍波 浪腹板剪切变形对CW-BRB弹性屈曲荷载的影响,为计算其约束比或正则化长细比提供依据。其次,重点研究 CW-BRB受力性能,通过建立CW-BRB的壳单元模型,分析其单调加载承载力与反复拉压荷载作用下的滞回性能 ,研究约束比变化对其受力性能与破坏机理的影响。最后,设计了1根单波浪腹板和1根双波浪腹板连接的 CW-BRB进行反复加载滞回性能试验研究,并采用壳单元及壳单元位移耦合技术建立CW-BRB试验试件的精细化 有限元模型,进行反复拉压荷载作用下的滞回性能数值模拟分析。试验结果与有限元计算结果吻合较好。     

Stiffened steel plates under uniaxial compression

The stability of steel plates stiffened with tee-shape sections under uniaxial compression and combined uniaxial compression and bending was investigated using a finite element model. The emphasis of the work presented in this paper was to find the parameters that uniquely describe the strength and behaviour of stiffened steel plates. A finite element model, validated using the results of tests on full-size stiffened plate panels, was used to investigate the scale effect for five dimensionless parameters. The parameters investigated were: the transverse slenderness of the plate, the slenderness of the web and flange of the stiffener, the ratio of torsional slenderness of the stiffener to the transverse slenderness of the plate, and the stiffener-to-plate area ratio. Average magnitude residual stresses and initial imperfections were assumed for this study.A parametric study covering a wide range of dimensionless parameters indicated that stiffened steel plates do not fail by stiffener tripping unless a bending moment is applied to create flexural compressive stresses in the stiffener. Although plate buckling and overall buckling were found to lead to a very stable post-buckling behaviour, the interaction between these two buckling modes was found to give rise to a sudden loss of capacity following initial plate buckling. The plate transverse slenderness, the stiffener slenderness-to-plate slenderness ratio, and the stiffener-to-plate area ratio were found to have a significant effect on this behaviour.A comparison of the numerical analysis results with API and DnV design guidelines indicates that the guidelines predict stiffened steel plate capacity with various degrees of success, depending on the governing mode of failure. Neither guidelines address the potential interaction-buckling phenomenon.     

大跨变截面波形钢腹板箱梁横向受力分析

为研究大跨变截面波形钢腹板预应力混凝土（PC）组合箱梁顶板在车轮局部荷载作用下的横向受力问题,结合2座桥例,分别建立全桥实体有限元模型;选择纵向3个典型截面,建立与之匹配和考虑有效分布宽度的平面框架模型;依据实体模型中顶板控制截面的横向应力影响线进行空间实体模型和平面框架模型的横向最不利加载,获得控制截面的最大横向拉应力及其沿纵向的变化规律,并对比了2种模型的计算结果。结果表明:对于顶板悬臂根部截面和腹板内侧截面,框架法与实体有限元法计算结果吻合良好;对于顶板跨中截面,腹板间距较大时,框架法的计算值偏于保守,设计中需对框架法的计算值进行适当折减;随着加载位置由跨中向支点移动,顶板跨中截面的横向应力峰值逐渐减小,悬臂根部截面和腹板内侧截面的横向应力峰值有增大趋势;有无横隔板对桥面板的横向受力影响很小,顶板跨中截面的横向应力值随波形钢腹板线刚度的增加线性减小。     

梁腹板在弯、剪及局压复合应力作用下的屈曲分析

前钢结构设计规范(GBJ17-88)中有关梁腹板局部稳定的计算公式来源于无限弹性完善板假定,一方面与构件的实际工作状况有一定出入,导致计算结果有时会偏于不安全;另一方面又与有关钢梁在弯曲正应力作用下的强度计算公式(考虑截面部分进入塑性)不相协调。针对《钢结构设计规范》(GB50017-2003)中变动较大的该部分设计内容,本文考虑不同的几何参数及弯、剪、局压多种应力组合工况对梁腹板屈曲临界应力的影响,对修订后的梁腹板横向加劲区格在复合应力作用下的临界应力相关公式进行了大量的有限元分析与计算;重点考察了梁腹板的弹塑性屈曲性态及规范(GB50017-2003)中相关公式所具有的设计安全度。在此基础上,提出相关的设计建议,供规范修订及进一步的研究参考。     

Ⅰ形截面钢构件腹板屈曲后强度利用

介绍轻型门式框架I形截面钢构件腹板的设计原则和方法.首先从防止受压翼缘压入腹板来分析腹板高厚比的最大限值,其次分别论述腹板受剪屈曲后的极限剪力计算、受弯或压弯屈曲后有效宽度的确定,以及正应力和剪应力联合作用下屈曲后相关关系的计算.     

波形钢腹板梁边缘的应力分布

波形钢腹板因其很多良好的性能而在结构中应用广泛。由于波形钢腹板在边缘和腹板的正态分布和剪应力分布与受平面挠曲与剪力影响的传统工字梁的应力分布不同,对波形钢腹板梁边缘的应力分布进行重点分析。在波形钢腹板边缘出现的附加的横向弯曲力矩,会导致对抗弯力矩有一定影响的附加正应力的分布。附加的横向弯曲力矩来自波形钢腹板中的剪力,它的数值取决于波形剖面的几何特征。对这种横向弯曲力矩的影响和趋势进行了分析。根据试验背景构建一个数值模型用来分析边缘的应力分布。测定附加正应力的趋势,并根据数值结果提出一个改进的设计方法来确定横向弯曲力矩和附加的正应力。     

Stress distribution in the flanges of girders with corrugated webs

The corrugated steel plate is a widely used structural element in many fields of application because of its numerous favorable properties. Due to the web corrugation the normal and shear stress distribution in the flange and web plates are different from the stress distribution of the conventional I-girders under in-plane bending and shear. The focus of this paper is the analysis of the stress distribution in the flanges of the girders with corrugated webs. Due to the corrugated web an additional transverse bending moment arises in the flange, which results in an additional normal stress distribution what has an effect on the bending moment resistance. The additional transverse bending moment comes from the shear force in the corrugated web and its value depends on the geometry of the corrugation profile. The effect and the tendency of this transverse bending moment are analyzed in the current paper. Based on experimental background a numerical model is developed to analyze the stress distribution in the flanges. Tendency of the additional normal stresses are determined and based on the numerical results an enhanced design method is proposed to determine the transverse bending moment and the additional normal stresses.     

Local buckling of grouted and ungrouted internally stiffened double-plate HPS webs

High performance steel (HPS) is rapidly gaining attention as a desirable material for highway bridge girders largely due to its superior toughness properties and high strength. However, the benefits of using steels with nominal yield strengths of 485 MPa (70 ksi) or greater is restricted by factors such as web stability, deflection, and fatigue design limits, which may govern the design and prevent the effective utilization of the material strength. Therefore, new and innovative bridge design concepts are needed to take better advantage of the enhanced properties of HPS. One design innovation that provides a means of optimizing bridge girders for high strength material utilizes I-girders with double web plates. The web is composed of two steel face plates connected internally by continuous longitudinal stiffening elements. The voids between the face plates may be grouted or ungrouted. The stiffeners permit thin webs to be used, while still allowing the material to reach stresses as high as the yield strength without buckling. In the case of grouted webs, composite behavior increases the out-of-plane stiffness of the web, although bond between the two materials may be unreliable. Nevertheless, it is shown that even in a debonded state, the presence of the grout enhances the buckling capacity of the face plates significantly. Using classical plate buckling theory, design criteria are proposed for bend buckling of the web face plates, considering both the grouted and ungrouted cases. As a means of assessing the anticipated behavior of the plates, upper and lower bounds to the buckling strengths are established. In order to evaluate the ability of classical plate theory to predict the buckling of the face plates, tests were conducted on a series of web panels that simulate a portion of a girder web subjected to flexural compressive stresses. Two of the specimens were ungrouted, two were grouted with a cementitious material, and one was grouted with an epoxy grout. It was confirmed that the presence of grout increased the buckling capacity of the face plates and that the improved bond using epoxy grout served to delay buckling as well, although when the bond broke the failure was sudden. The experimentally determined buckling loads are used to validate the theory.     

Study on shear resistance of aluminum alloy I-section members

The design method for the shear resistance of aluminum alloy I-section members is presented, taking into consideration of the post-buckling strength of webs and the restraint effect of flanges, and the practical design formulas are proposed. The deflection of aluminum alloy I-section members under concentrated load is simulated by using the finite element method, and several design theories are discussed. The relation of shear resistance to the maximum web displacement reflects that the web of aluminum alloy I-section member is under fewer shears buckling force, while the whole member has higher shear resistance. However, the traditional design method is not able to give the real shear resistance of aluminum alloy I-section members. The proposed design formulas for the shear resistance of aluminum alloy I-section members is used to calculate accurately the post-buckling resistance of webs and the shear resistance contribution of flanges. The results are in a great agreement with the test data of Hamoodi M J, Burt C A, Evans H R and the results from Eurocode9 formulas.     

Shear buckling characteristics of cold-formed steel channel beams

Cold-formed steel members are increasingly used as primary structural elements in the building industries around the world due to the availability of thin and high strength steels and advanced cold-forming technologies. Cold-formed lipped channel beams (LCB) are commonly used as flexural members such as floor joists and bearers. However, their shear capacities are determined based on conservative design rules. For the shear design of LCB web panels, their elastic shear buckling strength must be determined accurately including the potential post-buckling strength. Currently the elastic shear buckling coefficients of LCB web panels are determined by assuming conservatively that the web panels are simply supported at the junction between their flange and web elements. Hence finite element analyses were conducted to investigate the elastic shear buckling behavior of LCBs. An improved equation for the higher elastic shear buckling coefficient of LCBs was proposed based on finite element analysis results and included in the ultimate shear capacity equations of the North American cold-formed steel codes. Finite element analyses show that relatively short span LCBs without flange restraints are subjected to a new combined shear and flange distortion action due to the unbalanced shear flow. They also show that significant post-buckling strength is available for LCBs subjected to shear. New equations were also proposed in which post-buckling strength of LCBs was included.     

不锈钢薄腹梁受剪性能试验研究

通过对7根不锈钢薄腹梁进行受剪性能试验研究,分析了梁腹板的剪切屈曲和屈曲后强度。结果表明：所有梁均发生剪切屈曲破坏,薄腹板中形成拉力带,上翼缘和横向加劲肋中出现塑性铰;根据腹板表面应变和侧向鼓曲变形测得的剪切屈曲应力均低于理论计算的弹性剪切屈曲应力;梁的受剪承载力显著高于腹板剪切屈曲时的荷载,具有较高的屈曲后强度;梁端设置封头肋板可以提高梁的受剪承载力。基于得出的试验结果及现有其他试验数据,对两种考虑腹板屈曲后强度的受剪承载力计算方法进行评估,我国GB 50017—2017《钢结构设计标准》中的公式仅考虑了腹板的受剪承载力,其计算结果总体偏于保守,但是对腹板高厚比较小(λs<1.5)的不锈钢薄腹梁,受剪承载力计算偏于不安全,且计算结果离散性较大;EN 1993-1-4中的计算公式中同时考虑了腹板和翼缘的受剪承载力,其计算结果偏于保守且离散性较小。     

A study into optimization of stiffeners in plates subjected to shear loading

A great deal of attention has been focused on plates subjected to shear loading over the past decades. One main fact in design of such elements, which fall in the category of thin-walled structures, is their buckling behavior. Plate girders and recently shear walls are being widely used by structural engineers, as well as ship and aircraft designers. The role of stiffeners is proved to be vital in design of such structures to minimize their weight and cost.In this work, by using ANSYS finite element method of analysis, some 1200 plates are analyzed in order to study the role of stiffeners and to come up with some limits for an optimized design procedure. This eigenvalue method of analysis is first validated with the theoretical calculations and known cases for a wide range of typical panel geometries.The results show that the number of panels produced by intermediate transverse stiffeners should not be less than the value of plate's aspect ratio. In other words, the transverse stiffeners should divide the length of the plate to portions equal or less than its width.It is also shown that the optimum geometric properties of the stiffeners correspond to the point when the buckling shape of a plate changes from the overall mode to local mode. Furthermore, all stiffened plates, with a similar aspect ratio and number of stiffeners, have a specific value of EI_s/aD, for which the critical shear stress is optimal. In addition, some expressions to predict these properties are presented.     

Shear capacity of steel plate girders with large web openings, Part I: Modeling and simulations

Numerical simulations are carried out in order to provide data for the development of a design model for the shear capacity of steel girders with web openings, with and without transverse stiffeners and opening reinforcements. The numerical model is designed such that the girder is in a state of pure shear at the opening center. Results are presented in terms of ultimate shear capacity and distribution of transverse web deformations and von Mises stresses. Based on the numerical data, a design model is presented that accounts for the reduction in web shear area, shear buckling of the web and the effect of opening position, vertical stiffeners and opening reinforcements.