Longitudinally stiffened hybrid steel plate girders subjected to patch loading

Hybrid girders subjected to patch loading have been analyzed in a detailed fashion for the case in which the plates that assemble the girders are transversally stiffened. Scant work, however, is available for the case in which the girders are hybrid and, simultaneously, longitudinally stiffened. The driving force for developing the present research work is to complete the knowledge of the patch loading field for the particular structural alternative of a hybrid steel plate girder assembled with a longitudinal stiffener. In the current paper, a numerical database of 255 simulations on longitudinally stiffened steel girders subjected to patch loading developed by the authors is presented. The results obtained are used for assessing the resistance of longitudinally stiffened hybrid steel plate girders subjected to patch loading. Some discrepancies between the numerical and EN1993-1-5 results are pinpointed. A design proposal which enhances the current EN1993-1-5 formulation is given at the end of the paper.     

Transversally stiffened plate girders subjected to patch loading. Part 1. Preliminary study

In this paper, an experimental programme of six steel plate girders subjected to patch loading as well as results of forty eight numerically-tested prototypes are presented. Results of ultimate load capacity as well as structural responses from these girders are provided. In addition, experimental and numerical values of ultimate load capacity are compared with those predicted by EN1993-1–5. With such results, the response of transversally stiffened steel plate girders is discussed throughout the paper. Particular emphasis is given to the influence of the transverse stiffening on the ultimate load capacity of the girders. It is observed that girders with largely spaced transverse stiffeners present a considerably different response from girders with closely spaced transverse stiffeners. The structural response for the former case has been thoroughly studied in the last decades whereas little attention has been paid for the latter. Further analysis of this particular topic is provided in a companion paper.     

Hybrid steel plate girders subjected to patch loading, Part 1: Numerical study

Extensive research focused on the structural behavior of hybrid steel plate girders is nowadays available in the literature. Furthermore, extensive research devoted to the resistance of homogeneous girders to patch loading has been performed in the last decades. Investigations dealing simultaneously with both fields are, however, rather scarce. The driving force behind developing the present research work has been the aim of completing the knowledge of the patch loading field for the particular structural alternative of hybrid steel plate girder. In the current paper, experimental results found in the literature as well as additional numerical simulations developed by the authors are summarized. The results presented can be used for assessing the resistance of hybrid steel plate girders subjected to patch loading. An in-depth exploit of such results is presented in a companion paper.     

剪切作用下锥形板梁的试验和数值研究

对剪切作用下的锥形钢板梁进行了试验和数值研究。试验包含4个缩尺锥形钢板梁试件,主要研究其临界剪切荷载和极限抗剪强度。此外,研究了锥形板的后屈曲特性。另外,对不同几何形状的锥形板进行了参数研究,以找到最有利的设计方案。分析的参数有:板的高宽比、翼缘的倾斜角、腹板和翼缘的长细比。由于性能的不同,对4种类型的锥形板梁分别进行建模和数值模拟。欧洲规范EN1993-1-5给出的锥形板的简化方法证实,在某些情况下,估计的极限剪切强度偏于不安全,需要进行修改。     

Finite element investigation of shear failure of lean duplex stainless steel plate girders

The use of duplex stainless steel material has gained popularity in the last two decades thanks to its nature that combines well the advantages of both austenitics and carbon steel materials. The duplex grades offer a combination of higher strength than austenitics in addition to a great majority of carbon steels with similar or superior corrosion resistance. However, high nickel prices have more recently led to a demand for lean duplexes with low nickel content, such as grade EN 1.4162. Wide-ranging work is needed to include the lean duplex grade EN 1.4162, into design standards such as EN 1993-1-4. Accordingly, a finite element modelling for full-size lean duplex stainless steel plate girders of non-rigid end stiffeners of Grade EN 1.4162 is presented in this paper. The paper is principally concerned with shear failure mechanism characteristics of this type of plate girders, which is not yet investigated. The ABAQUS 6.6 programme, as a finite element package, is used in the current work. The lean duplex stainless steel material is simulated here based on an accepted stainless steel material model available in the literature. A number of transversely stiffened I-section plate girders having equal depth of 1000 mm in span of 4 m is considered and parametric studies regarding flange width-to-web depth ratio, flange-to-web thickness ratio and web plate slenderness are carried out. However, new conclusions on shear strength of lean duplex stainless steel plate girders are presented.     

Moment–shear interaction of stiffened plate girders—Tests and numerical model verification

Results of four full-scale tests on plate girders stiffened with transverse and longitudinal stiffeners subjected to interaction of high bending moment and shear force are presented and discussed. In longitudinal direction the web was stiffened with open or closed stiffeners positioned in the compression zone. Detailed information on initial geometric imperfection and residual stresses is given. The experimental results were used to verify numerical model. The resistance is compared against reduced stress method and effective width method given in EN 1993-1-5.     

波浪腹板工形梁局部承压承载力设计方法研究

波浪腹板工形梁的局部承压性能目前国内外研究较少。在总结前人对平腹板和梯形波折腹板梁局部承压极限承载力研究工作的基础上,对波浪腹板工形梁的局部承压性能及设计方法进行研究。通过有限元数值分析,揭示波浪腹板工形梁在局部压力作用下的破坏形式以及腹板几何初始缺陷对局部承压性能的影响,在几何参数分析的基础上建立局部承压极限承载力的简化计算公式。最后针对同时承受局部荷载和弯矩的波浪腹板工形梁,建立截面弯矩与局部压力之间的M-P承载力相关计算公式,并通过有限元数值计算进行验证。     

Imperfection sensitivity of plate girder webs subjected to patch loading

This paper is aimed at studying the influence of initial geometric imperfections on the postbuckling behavior of longitudinally stiffened plate girder webs subjected to patch loading. A sensitivity analysis is conducted herein using two approaches (deterministic and probabilistic) in order to investigate the effect of varying imperfection shape and amplitude on both, the postbuckling response and ultimate strength of plate girders under patch loading. This sensitivity analysis is performed by means of nonlinear finite element analysis. At first, the initial shape imperfections are modeled using the buckling mode shapes resulting from an eigenvalue buckling analysis. Thereafter, the amplitude of the buckling shapes for the various modes is varied, and then introduced in the nonlinear analysis. The results show the influence of these modes and amplitudes on the resistance to patch loading.     

不锈钢节点板连接件数值分析

尽管不锈钢和碳素钢的力学性能有本质区别,然而,现行规范规定不锈钢连接设计时仍基本遵循碳素钢的设计准则,仅在此基础上稍作修改。对于常见的角钢单肢与加固板连接的情况,EN1993-1-4以及SCI/欧盟不锈钢设计手册对不锈钢的设计规定,直接采用了EN1993-1-8对碳素钢净截面承载力的设计规定,且未作任何修改。对单肢与加固板采用单排螺栓连接的L型不锈钢的净截面承载力进行了研究。建立奥氏体不锈钢的数值模型,并利用现有的试验结果对其进行了验证。这些模型随后用于进行参数研究。最后,基于研究结果对L型不锈钢净截面承载力的设计方程进行了修正,并通过统计分析验证了该方程可靠性。     

《钢结构设计规范》(GB50017—2002)焊接工字梁腹板的局部稳定和考虑屈曲后强度的计算

与现行《钢结构设计规范》(GBJ17—88)相比,新修订的《钢结构设计规范》(GB50017—2002)对焊接工字梁腹板屈曲临界应力和局部稳定的计算作了较大的改动,增加了梁腹板考虑屈曲后强度设计的相关条文。对弯矩、剪力和局部压力单独作用下的腹板屈曲临界应力作了修正,考虑了板件的几何缺陷和材料非弹性性能,对于直接承受动力荷载的吊车梁及类似构件或不考虑腹板屈曲后强度的焊接工字梁,要求按规定配置加劲肋,并验算腹板的局部稳定性,计算局部稳定的相关公式随着临界应力的修正也作了相应的调整;建议承受静力荷载和间接承受动力荷载的焊接工字梁宜考虑腹板屈曲后强度,按考虑腹板屈曲后强度来计算梁的的抗剪和抗弯承载力,而不再验算腹板的局部稳定。本文详细介绍了规范条文修改的理论依据,比较了新旧设计方法的差异,并通过设计实例说明了新设计方法的优越性。     

Parametric analysis of the lateral–torsional buckling resistance of steel beams in case of fire

Numerical modelling of the lateral–torsional buckling of steel beams at elevated temperature has shown that the beam design curve from EN 1993-1-2 is over-conservative in the case of non-uniform bending. Based on the newly proposed methodology for cold design from the EN 1993-1-1, an improved proposal for the lateral–torsional buckling of unrestrained steel beams subjected to fire is presented in this paper that addresses the issue of the influence of the loading type, the steel grade, the pattern of the residual stresses (hot-rolled or welded sections) and the ratio h/b, between the depth h and the width b of the cross-section on the resistance of the beam, achieving better agreement with the numerical behaviour while maintaining safety. The proposal is found to be safe and accurate through an extensive comparison with the results of FEM numerical simulations of more than 5000 beams. A statistical study of the results is performed, showing the accuracy of the improved proposal presented in this paper.     

Ultimate strength of I-girders under eccentric patch loading: Derivation of a new strength reduction coefficient

In structural applications I-girders are subjected to eccentric patch loading since even a small eccentricity of applied loads relative to the web plane is unavoidable in practice. Experimental research shows that the behaviour of eccentrically loaded girders differs from that of concentrically loaded girders. A reduction in ultimate strength due to eccentricity is evident, and some expressions for the reduction have been proposed. We show that these expressions overestimate the reduction in capacity for large eccentricities. In this paper, results of 102 tests on I-girders subjected to eccentric patch loading are presented and the variables involved in the phenomenon are evaluated based on a parametric study of experimental data and the results of several finite element models. The parametric study confirms that the parameters previously identified for evaluating the effect of small eccentricities are sufficient for addressing cases with larger eccentricities. New mathematical expressions are proposed herein to represent the reduction in strength across the full range of eccentricities considered.     

锈蚀箱梁极限强度试验中板变形量的分析

根据垂直弯曲荷载下3个锈蚀箱梁板的压应力试验结果,分析初始和倒塌后的板变形量。研究初始缺陷和腐蚀对倒塌后最终变形的影响,得出不同的荷载响应、初始缺陷和板高厚比之间的关系。分析初始缺陷、板高厚比和倒塌后最终变形,建立高厚比准则以计算倒塌后变形。     

Analysis of plate deflections during ultimate strength experiments of corroded box girders

The objective of this work is to analyze the initial and post-collapse plate deflections based on measurement records of the experiments of three corroded box girders subjected to pure vertical bending loading inducing a compressive stress on deck. The effect of initial imperfections and corrosion degradation on the final post-collapse deformation shape has been investigated and a relationship between different loading responses, shape of initial imperfections and plate slenderness has been derived. Analyzing initial imperfections, plate slenderness and final post-collapse deformations, a slenderness criterion has been established to predict the post-collapse deformation shape.     

Numerical investigation of net section failure in stainless steel bolted connections

Despite fundamental differences in the mechanical behaviour of stainless steel and carbon steel, design provisions for stainless steel connections in current standards essentially follow the rules for carbon steel with some limited modifications. For the case of net section capacity, the design rules from EN 1993-1-3 for cold-formed carbon steel have been adopted for stainless steel connections in EN 1993-1-4 and the SCI/Euro Inox Design Manual without any modification. In this paper, an investigation into the behaviour of stainless steel connections failing by net section rupture has been conducted. Numerical models for austenitic and ferritic stainless steel have been developed and validated against existing test results. The validated models were subsequently used to perform parametric studies to investigate the main parameters affecting the net section rupture of bolted connections; these include edge distance e₂ and bolt configuration. By studying the stress distribution along the net section for different edge distances and bolt arrangements, it was found that the ductility of stainless steel is sufficient to ensure extensive redistribution of stresses prior to fracture. Hence, a revised design equation (based on that given in EN 1993-1-3) for net section capacity of stainless steel connections has been proposed and its reliability demonstrated by means of statistical analysis.     

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。     

Calculation of temperature in fire-exposed bare steel structures: Comparison between ENV 1993-1-2 and EN 1993-1-2

A comparison is made between the formula presented in ENV 1993-1-2 and EN 1993-1-2 for calculating temperature in bare steel structures subjected to fire. The ratio between the radiative energy considered in each formula is first calculated for 377 commercially available sections. The evolution of the steel temperature is then calculated in 4 different representative sections. On the basis of these comparisons and taking into account the fact that the load-bearing capacity has to be ensured in steel members, it does not appear that significant modifications in the safety level have been introduced from the ENV to the EN version of Eurocode 3.     

Biegedrillknicken von Trägern mit einfach‐symmetrischen Profilen

Lateral torsional buckling of girders with monosymmetric cross‐sections. The determination of the critical moment for lateral torsional buckling constitutes a main design issue for steel girders subjected to bending moments. This paper presents simple formulae for the estimation of the critical moment for simply supported girders subjected to end moments and transverse loading. The formulae cover a wide range of practical applications. They are derived by formulation of the relevant energy potential and solution by means of the Ritz method. For the angle of twisting one series terms are considered. The accuracy in comparison with more elaborated solutions by means of more series terms is examined. The comparison shows the adequacy of the proposed method.     

U型加劲肋加固的高强钢面板体系的面内极限抗压强度

通过非线性有限元分析(FEA)研究使用U型加固件纵向加劲的面板的极限抗压强度。对112个由各种细长参数的面板和柱以及加固件组成的模型进行分析。模型包括了普通钢材和高强钢的弹塑性应变硬化本构关系。有限元分析中也包括了初始几何缺陷和残余应力。将有限元分析得出的结果与欧洲规范3EN1993-1-5、FHWA-TS-80–205和其他可用公式计算出的强度进行比较。基于分析结果,可得出一个针对使用普通钢材或高强钢(HPS)加劲板系统的新的强度预测公式。结果表明:当柱的长细比较大时,使用欧盟规范3EN1993-1-5和FHWA-TS-80–205可能导致设计过于保守;而采用所提出简化形式的公式可更精确地预测强度,从而得出更经济的设计。