考虑剪切变形和弯剪相互作用的带翼缘剪力墙数值模型（英文）

提出了一种基于柔度法的考虑剪切变形和弯剪耦合效应的有限元模型,通过T形和L形剪力墙试件拟静力试验验证了模型的正确性。结果表明,所有试件的破坏形态为无翼缘腹板端部混凝土压碎、纵筋压曲的弯曲破坏;增强无翼缘腹板端部约束和边缘构件约束,可以防止其发生受压过早破坏;腹板和翼缘相交处未观察到明显的混凝土剥落现象,腹板和翼缘相交处的约束边缘构件抗震设计可以适当放宽;随着剪跨比的减小,试件延性明显降低;当翼缘处于受拉时,试件表现出较高的强度、刚度和较低的延性。基于模型对钢筋混凝土带翼缘剪力墙的拟静力试验进行了非线性数值模拟分析,分析结果与试验结果吻合较好,表明模型能较好地模拟钢筋混凝土带翼缘剪力墙的非线性性能。     

翼缘非等厚矩形钢管混凝土梁受弯性能研究

为了研究翼缘非等厚矩形钢管混凝土梁的受力性能,进行了7根钢管混凝土梁的四点弯曲试验,试件的变化参数为钢管上、下翼缘厚度和混凝土强度。结果表明,钢管上下翼缘厚度之比越小,承载力极限状态下的截面中性轴越靠下,表明参与工作的混凝土越多,组合截面承载性能越好;当上下翼缘厚度之比约为1/3时,通过提高混凝土的强度能有效增大构件的受弯承载力。采用有限元软件ABAQUS对受弯试验进行了全过程模拟,得到的结果与试验结果吻合。模拟分析还表明,优化后的翼缘非等厚矩形钢管混凝土截面不仅增大了钢管分担的弯矩,同时也增加了混凝土的工作面积,两者共同作用提升了构件的受弯承载力,当含钢率约为0.2时,承载力相较于等壁厚构件可提升15%以上。在平截面假定的基础上推导了翼缘非等厚矩形钢管混凝土组合截面受弯承载力的解析表达式,并探讨了对构件截面的优化问题,特别对含钢率较高的高强混凝土构件,优化截面的承载力提高效果显著。研究结果表明,翼缘非等厚矩形钢管混凝土梁具有良好的承载性能和变形性能。     

受压钢构件的板件宽(高)厚比

本文通过对均匀压力作用下的四边简支矩形板在弹性状态下的平衡条件,按不同板件宽厚比求得屈曲应力,并以此为基础,进一步对其它支承条件及弹塑性状态(并考虑残余应力和初弯曲影响)、不同嵌固作用下板的屈曲应力的计算,进行了论述。并具体例述了由板件屈曲应力和构件临界应力等稳条件下工字形、箱形截面受压构件的翼缘和腹板宽(高)厚比的计算,经12个板件屈曲试验论证相符较好;同时,运用弹塑性理论对压弯作用下腹扳受剪、截面塑化不等的工字形、箱形截面构件的翼缘和腹板宽(高)厚比的规范规定,详细作了解说。     

冷弯残余应力的测试方法改进与模拟

针对采用电化学腐蚀方法,测试冷弯薄壁型钢构件残余应力工艺中,存在着测点失效过多的不足,调整了电解液配比,改进了测点防腐处理及调减测点数量等,测试效果改善明显。提出了运用有限元方法,采用弯曲与回弹组合的原理,模拟冷弯薄壁型钢的成型过程,获取冷弯残余应力的方法。模拟结果与试验结果比对表明,提出的模拟方法是可行的。试验与模拟相结合,为进一步开展冷弯残余应力的研究提供了方便。     

高强焊接工字钢开孔梁受弯性能试验研究

基于国产高强钢Q550D和TQ700MCD的材料性能试验结果,对窄翼缘和宽翼缘两种截面形式的高强焊接工字钢开孔梁进行受弯试验研究。主要研究试件的破坏形态、抗弯承载力、弯矩曲率、应变分布等,探讨窄翼缘和宽翼缘两种截面形式分别在两种弯曲状态下,孔洞参数对试件受弯性能的影响,并比较三点弯曲试验和四点弯曲试验下试件极限承载力的大小。试验结果表明:试件的典型破坏形式为受压翼缘板发生局部屈曲,屈曲半波长度与翼缘宽度相当。对于窄翼缘截面梁,在两种弯曲状态下,当开设孔洞的径高比为0.3时,孔洞的存在对试件的极限承载力影响都较小;当径高比为0.6时,四点弯曲试件的极限承载力比三点弯曲试件的极限承载力下降显著。对于宽翼缘截面梁,在两种弯曲状态下,当开设孔洞的径高比为0.3时,孔洞数目的增加对试件极限承载力的影响较小。开孔试件由于孔洞的存在,导致应力重分布,使试件的极限承载力有不同程度的下降,但下降幅度与开设孔洞的参数紧密相关。     

焊接H形截面纯弯钢构件弹塑性局部相关屈曲分析

采用ANSYS软件建立焊接H形截面纯弯钢构件有限元分析模型,模拟截面残余应力、板件初始缺陷和几何非线性,分析强翼缘弱腹板和弱翼缘强腹板两组构件的弹塑性局部相关屈曲性能,分别讨论腹板高厚比、翼缘宽厚比和相对宽厚比(腹板高厚比与翼缘宽厚比之比)对构件局部稳定系数的影响。研究结果表明,局部稳定系数随腹板高厚比或翼缘宽厚比增大而显著降低,与相对宽厚比基本成线性关系;两组局部稳定系数拟合公式相对误差为-1.19%~1.15%,精度较高;可以根据整体稳定性和局部相关稳定性近似相等的原则,确定腹板高厚比和翼缘宽厚比限值相关曲线;平面外整体长细比较小时,钢结构设计规范的腹板高厚比和翼缘宽厚比限值部分超越宽厚比限值相关曲线。     

负弯矩作用下钢-混凝土组合梁受力性能有限元分析及受弯承载力计算

为研究钢-混凝土组合梁在负弯矩作用下的畸变屈曲问题,基于作者在前期的试验研究,建立组合梁非线性有限元分析模型,其有效性得到试验数据的验证。应用该有限元分析模型进一步分析了端部弯矩比、力比、腹板高厚比、H形钢截面高宽比、受压翼缘侧向长细比、残余应力分布模式、组合程度等7种参数对组合梁畸变屈曲及受弯承载力的影响。分析结果表明:随着端部弯矩比、腹板高厚比、受压翼缘侧向长细比增大,受弯承载力减小。随着力比增大,受弯承载力增大。焊接截面组合梁的受弯承载力小于轧制组合梁的受弯承载力。组合程度对受弯承载力的影响较小。提出考虑上述影响参数以及侧向弯曲屈曲和侧向弯扭屈曲两种失稳模式的受弯承载力计算公式,计算结果与有限元分析以及试验结果吻合较好。     

冷弯厚壁型钢残余应力影响分析

结合现有关于冷弯型钢残余应力的研究成果,用有限元软件模拟分析了在初始缺陷影响下,冷弯厚壁双槽钢柱焊接组合截面构件,在冷弯残余应力单独作用以及焊接残余应力和冷弯残余应力共同作用下的整体稳定性。分析发现:在焊接残余应力和冷弯残余应力共同作用下,厚壁轴心受压构件的整体稳定性能普遍比现有规范的结果低,最大误差达15%。因此在确定该构件稳定承载力时,应考虑焊接残余应力和冷弯残余应力的共同作用。     

Experimental study on residual stresses in welded monosymmetric I-section

为了研究单轴对称焊接工字形截面残余应力分布规律,采用盲孔法对15个单轴对称工字形截面试件进行了试验研究,得到了不同试件全截面纵向残余应力分布,研究了腹板高厚比、翼缘宽厚比、翼缘宽度、施焊顺序等对残余应力的影响。试验结果表明：残余压应力数值与截面尺寸直接相关,残余拉应力数值受截面尺寸影响较小;腹板中靠近宽翼缘一侧的残余压应力峰值大于靠近窄翼缘一侧的压应力峰值;翼缘宽度增大时,分布于所在翼缘和腹板的残余压应力减小;施焊顺序对翼缘上的残余应力及腹板上的残余拉应力峰值有一定影响,而腹板上的残余压应力没有明显变化。基于试验结果,提出了适用于单轴对称焊接工字形截面的残余应力分布模型,该模型能够较准确反映各种因素的影响。     

单轴对称焊接工字形截面残余应力试验研究

为了研究单轴对称焊接工字形截面残余应力分布规律,采用盲孔法对15个单轴对称工字形截面试件进行了试验研究,得到了不同试件全截面纵向残余应力分布,研究了腹板高厚比、翼缘宽厚比、翼缘宽度、施焊顺序等对残余应力的影响。试验结果表明:残余压应力数值与截面尺寸直接相关,残余拉应力数值受截面尺寸影响较小;腹板中靠近宽翼缘一侧的残余压应力峰值大于靠近窄翼缘一侧的压应力峰值;翼缘宽度增大时,分布于所在翼缘和腹板的残余压应力减小;施焊顺序对翼缘上的残余应力及腹板上的残余拉应力峰值有一定影响,而腹板上的残余压应力没有明显变化。基于试验结果,提出了适用于单轴对称焊接工字形截面的残余应力分布模型,该模型能够较准确反映各种因素的影响。     

Finite element simulations of residual stresses in roller bent wide flange sections

Curved structural wide flange steel sections are frequently used in buildings or bridges. These sections are usually curved at ambient temperatures with a roller bending machine. This process alters the residual stress distribution, which may affect the elasto-plastic buckling behavior of arches. This paper presents a numerical modeling technique to estimate residual stresses in curved wide flange sections manufactured by the pyramid roller bending process. The technique incorporates material non-linearity, geometrical non-linearity and contact modeling. Numerically obtained residual stresses are compared to experimental results and good agreement was found for the top flange. Only moderate agreement was observed for the web but very good coherence was realized for the bottom flange. It is concluded that a finite element analysis can be used to estimate residual stresses in roller bent wide flange sections.     

Experimental investigation of residual stresses in roller bent wide flange steel sections

Residual stresses in straight hot rolled wide flange sections are well documented and have been investigated in the recent past. However, to the knowledge of the authors, residual stress measurements have not been published on roller bent wide flange sections. Straight sections are curved into roller bent ones at ambient temperatures by means of the roller bending process. Since roller bent sections underwent severe plastic deformation during the forming process, the well-known residual stress patterns from hot rolling may not be appropriate for the roller bent steel. Roller bent sections can be applied in halls, roofings and bridges, thereby acting as structural arches and it is important that a realistic residual stress pattern is implemented when assessing their load carrying capacity. An experimental program has been carried out to investigate the residual stresses in roller bent wide flange sections bent about the strong axis. Residual stresses were measured with the sectioning method. The experimental technique was investigated with respect to possible temperature influence and repeatability of the measurements. Experimental values revealed that the residual stress pattern and magnitude in roller bent sections is different when compared to their straight counterparts.     

Proposed residual stress model for roller bent steel wide flange sections

The manufacturing process of structural wide flange steel sections introduces residual stresses in the material. These stresses due to hot-rolling or welding influence the inelastic buckling response of structural steel members and need to be taken into account in the design. Based on experimental data standardized residual stress models have been proposed for inclusion in inelastic buckling analyses. By incorporating these residual stress models their effect on the resistance of beams and columns can be obtained. Residual stress models for roller bent steel sections are currently not available. Roller bent wide flange sections are manufactured by curving straight members at ambient temperature. This manufacturing technique, which is also known as roller bending, stresses the material beyond its yield stress, thereby overriding the initial residual stresses prior to bending and generating an entirely new pattern. This paper proposes a residual stress model for roller bent wide flange sections, based on earlier conducted numerical investigations which were validated by experimental research performed at Eindhoven University of Technology. The proposed residual stress model can serve as an initial state of a roller bent steel section in fully non-linear finite element analyses to accurately predict its influence on the inelastic buckling response.     

Mechanical properties of roller bent wide flange sections — Part 1: Experimental investigation

Arched roofs are built more and more with roller bent wide flange sections, serving as structural elements. Roller bent wide flange sections are manufactured from straight hot-rolled wide flange sections by a process called roller bending. The material is cold worked during forming, inducing a new distribution of mechanical properties across the section which is different compared to its original state. For the design of arches the use of original or nominal strength properties of the straight material neglects the influence of the roller bending process. This may lead to conservative or nonconservative designs. This paper presents the results of an extensive experimental investigation of the mechanical properties of roller bent wide flange sections. It comprises tensile tests and compression tests on coupons taken from roller bent sections and their straight counterparts. The results show that the roller bending process alters the mechanical properties of the material non-uniformly over the cross-section. In this paper the experimental results are presented. In a companion paper the experimental results are used to arrive at a set of equations that yields different stress-strain curves for specific zones across the roller bent steel section.     

Mechanical properties of roller bent wide flange sections — Part 2: Prediction model

This paper provides a series of simple equations that allow the structural engineer to predict the mechanical properties across the section of roller bent wide flange steel members: proportional limit, yield stress, ultimate tensile stress, strain at ultimate tensile stress and strain at rupture. The equations are based on experimental results from tensile tests performed on coupons taken from roller bent wide flange sections which are presented in a companion paper. The newly obtained mechanical properties yield seven different full stress-strain curves for nine specific locations on the steel cross-section. The stress-strain models for the material of the flanges are defined by non-linear curves. The stress-strain characteristics in the web allow the material to be represented by bi-linear stress-strain curves. Comparison between predicted adjustments in mechanical properties due to roller bending and measured properties gives good agreement. The obtained stress-strain curves are suitable for implementation in finite element models for the analysis of arch structures employing beam, shell or solid elements.     

Influence of cold bending on the resistance of wide flange members

Cold rolling is used for bending straight members with hot rolled wide-flange sections to create arches. Extensive studies have shown that the influence of residual stresses due to hot rolling on the resistance of wide-flange steel sections is nonnegligible. On the contrary, the residual stress pattern due to roller bending has been only recently identified. Its effects on the elasto-plastic behavior of curved members have not been studied sufficiently. In this paper, an in-depth study of the influence of such residual stresses is performed. Considering the residual stress pattern due to cold bending, interaction diagrams and buckling curves for cold bent steel arches are developed. The results are quantified and compared with those for hot-rolled and stress free members. This allows designers to appreciate the available margins of safety when using standard interaction equations and buckling curves for cold bent members. Furthermore, the results suggest the necessity for the development of buckling curves for cold bent members including initial imperfections.     

Flange/web distortional buckling of cold-formed steel sections in bending

Recent experimental tests of cold-formed steel C- and Z-sections in bending have revealed unconservative results in the prediction of the bending moment resistance, using the current North American Design Standards. The failure mode of these tests was identified as flange/web distortional buckling. This mode of failure initially involves a rotation of the lip/flange component about the flange/web corner, which typically occurs for short half-wavelength distortional buckling. Near ultimate failure, an apparent lateral movement of the flange/web corner, which includes transverse bending of the web, is experienced. Various analytical methods that predict the moment resistance of sections which experience short half-wavelength distortional buckling were investigated and compared with the applicable test data. The modified Lau and Hancock 2 Model, with S136-94 Standard calculated effective section modulus, is recommended for use as the North American predictor model for the flange/web distortional buckling moment resistance of cold-formed steel sections in bending.     

Section moment capacity tests of LiteSteel beams

The LiteSteel beam (LSB) is a new cold-formed hollow flange channel section developed by OneSteel Australian Tube Mills using their patented dual electric resistance welding and automated continuous roll-forming process. It has a unique geometry consisting of torsionally rigid rectangular hollow flanges and a relatively slender web. In addition to this unique geometry, the LSB sections also have unique characteristics relating to their stress–strain curves, residual stresses, initial geometric imperfections and hollow flanges that are not encountered in conventional hot-rolled and cold-formed steel channel sections. An experimental study including 20 section moment capacity tests was therefore conducted to investigate the behaviour and strength of LSB flexural members. The presence of inelastic reserve bending capacity in these beams was investigated in detail although the current design rules generally limit the section moment capacities of cold-formed steel members to their first yield moments. The ultimate moment capacities from the tests were compared with the section moment capacities predicted by the current cold-formed and hot-rolled steel design standards. It was found that compact and non-compact LSB sections have greater moment capacities than their first yield moments. The current cold-formed steel design standards were found to be conservative in predicting the section moment capacities of compact and non-compact LSB sections, while the hot-rolled steel design standards were able to better predict them. This paper has shown that suitable modifications are needed to the current design rules to allow the inclusion of available inelastic bending capacities of LSBs in design.     

Behaviour and strength of hollow flange channel sections under torsion and bending

Hollow flange channel section is a cold-formed high-strength and thin-walled steel section with a unique shape including two rectangular hollow flanges and a slender web. Due to its mono-symmetric characteristics, it will also be subjected to torsion when subjected to transverse loads in practical applications. Past research on steel beams subject to torsion has concentrated on open sections while very few steel design standards give suitable design rules for torsion design. Since the hollow flange channel section is different from conventional open sections, its torsional behaviour remains unknown to researchers. Therefore the elastic behaviour of hollow flange channel sections subject to uniform and non-uniform torsion, and combined torsion and bending was investigated using the solutions of appropriate differential equilibrium equations. The section torsion shear flow, warping normal stress distribution, and section constants including torsion constant and warping constant were obtained. The results were compared with those from finite element analyses that verified the accuracy of analytical solutions. Parametric studies were undertaken for simply supported beams subject to a uniformly distributed torque and a uniformly distributed transverse load applied away from the shear centre. This paper presents the details of this research into the elastic behaviour and strength of hollow flange channel sections subject to torsion and bending and the results.     

Elasto‐plastische Schubverformungen und Schubversagen kurzer Stahlstützen

Elasto‐plastic shear deformation and fracture behaviors of short steel stanchions. Short steel stanchions with various width‐to‐thickness ratios of flange and web under axial compression are clarified experimentally as well as analytically. There exists a critical value of shear span ratio _Gr(H/h) between shear and bending yield of wide flange steel stanchions. Shear yielding of short steel columns shows no Lüders's lines but very many small protuberance particles up to parallelogram deformed web surfaces. There exists a fundamental large difference between shear and bending yield behaviors of wide flange steel stanchions. Finally the critical shear span ratio of wide flange steel profile will be derived analytically and through experiment proved.