高强H形钢混凝土组合柱轴压性能研究

为研究高强H形钢混凝土组合柱的轴心受压性能以及探究国内外现行规范对此类构件承载力计算方法的适用性,对12根内置Q460、Q690高强H形钢混凝土组合柱及3根内置Q235普通H形钢混凝土组合柱进行轴压试验,研究钢材强度等级、含钢率、长细比和配箍率等参数对构件承载力的影响。试验结果表明：内置Q460、Q690高强H形钢混凝土组合柱与内置Q235普通H形钢混凝土组合柱相比,承载力最大提高幅度分别为19.6%和35.8%;高强H形钢含钢率的提升能显著提高组合柱的承载力;当组合柱长细比在23.0~45.9范围变化时,其对承载力影响不明显;提高配箍率对内置Q690的H形钢混凝土组合柱承载力的提高幅度高于内置Q460的H形钢混凝土组合柱。将试验结果与我国JGJ 138—2016《组合结构设计规范》、美国ANSI/AISC 360-16和欧洲EN1994-1-1:2004中的H形钢混凝土组合柱轴压承载力公式计算值进行对比可得,各国规范的计算值均偏于保守,JGJ 138—2016的计算值与试验结果最为接近。考虑箍筋对混凝土的约束效应,对JGJ 138—2016的组合柱轴压承载力计算公式进行修正,修正公式所得承载力计算结果与试验结果误差降低至10%以内。基于约束效应建立组合柱有限元模型,考虑约束效应的承载力有限元模拟结果与试验结果吻合良好,误差在5%以内。     

Study on axial compression performance of high strength H-section steel reinforced concrete composite columns

为研究高强H形钢混凝土组合柱的轴心受压性能以及探究国内外现行规范对此类构件承载力计算方法的适用性，对12根内置Q460、Q690高强H形钢混凝土组合柱及3根内置Q235普通H形钢混凝土组合柱进行轴压试验，研究钢材强度等级、含钢率、长细比和配箍率等参数对构件承载力的影响。试验结果表明：内置Q460、Q690高强H形钢混凝土组合柱与内置Q235普通H形钢混凝土组合柱相比，承载力最大提高幅度分别为19.6%和35.8%；高强H形钢含钢率的提升能显著提高组合柱的承载力；当组合柱长细比在23.0~45.9范围变化时，其对承载力影响不明显；提高配箍率对内置Q690的H形钢混凝土组合柱承载力的提高幅度高于内置Q460的H形钢混凝土组合柱。将试验结果与我国JGJ 138—2016《组合结构设计规范》、美国ANSI/AISC 360-16和欧洲EN1994-1-1:2004中的H形钢混凝土组合柱轴压承载力公式计算值进行对比可得，各国规范的计算值均偏于保守，JGJ 138—2016的计算值与试验结果最为接近。考虑箍筋对混凝土的约束效应，对JGJ 138—2016的组合柱轴压承载力计算公式进行修正，修正公式所得承载力计算结果与试验结果误差降低至10%以内。基于约束效应建立组合柱有限元模型，考虑约束效应的承载力有限元模拟结果与试验结果吻合良好，误差在5%以内。     

冷弯中厚壁矩形管屈服强度设计公式研究

为研究冷弯中厚壁矩形管冷弯效应对钢材屈服强度及其他力学性能的影响,对国内现有冷弯中厚壁矩形管的板件试样材性试验和短柱试验数据按照不同截面形式、钢材等级、厂家、厚度及成型方式等进行汇总与分析。提出了适合我国钢材特点与考虑冷弯效应的冷弯中厚壁矩形管屈服强度设计建议公式,将国内外相关规范的考虑冷弯效应的屈服强度计算公式和本文建议公式的计算结果与冷弯中厚壁方(矩)形管短柱试验数据进行对比分析,以验证本文建议公式的适用性。结果表明:按北美规范AISI S100-2007、欧洲规范EN 1993-1-3:2006和加拿大规范CAN3-S136-M84:1984得到的强度计算值相比于个别短柱试验值偏大,我国GB 50018—2002《冷弯薄壁型钢结构技术规范》中的屈服强度计算值相对于采用宝钢和Q345钢材的某些短柱试验值偏大。本文建议公式计算值相对于短柱试验值均偏小且安全,可作为冷弯中厚壁矩形管考虑冷弯效应的强度设计公式。     

高强钢管高强混凝土短柱力学性能智能模型研究

为研究超出规范范围材料强度的高强钢管高强混凝土短柱承载力在规范范围外拓展应用的相关问题,搜集61组试验及有限元数据,利用神经网络智能技术研究了在不同的截面尺寸、高强材料、含钢率、偏心率和长细比等影响因素下的高强钢管高强混凝土短柱的极限承载力及荷载-位移曲线,将承载力预测结果与规范EC4、规范ACI及规范GJB 4142—2000的计算结果进行了对比分析,并预测了试件的荷载-位移曲线,对各阶段各模型的切线刚度进行了分析研究。研究结果表明：所述规范可以在一定程度上继续延伸使用,而神经网络智能模型不仅与试验数据吻合度较高、精确度高,还考虑了规范没有考虑的约束效应减弱及两种材料强度匹配程度对承载力的影响,承载力会随着混凝土强度和钢材强度的提高而减缓增强速度;神经网络智能模型非常适合用于预测高强钢管高强混凝土短柱承载力,可以为实际工程和规范延伸拓展提供设计参考;神经网络智能模型相比于现有组合构件应力-应变理论公式会更加简便准确,以切线刚度的对比结果可知,其可以更加准确地反映和再现轴压作用下高强钢管高强混凝土短柱荷载-位移曲线的特征,对构件的力学性能研究有一定的参考作用。     

高强钢焊接箱形截面压弯构件局部稳定试验研究

为研究高强钢压弯构件的局部稳定性能，对5个Q460C和5个Q690D钢焊接箱形截面构件进行了单向偏压试验，分析了其破坏形式、局部稳定性能以及承载力；将实测承载力与欧洲规范EN 1993-1、我国标准GB 50017—2017和美国规范ANSI/AISC 360-16相关公式计算结果相比较，以验证各规范对Q460C钢和Q690D钢焊接箱形截面压弯构件屈曲后强度计算的适用性。研究结果表明：所有高强钢焊接箱形截面压弯构件均在柱中附近发生局部屈曲破坏；由轴向压力-轴向压缩变形或轴向压力-水平位移曲线可知，其为极值点失稳；构件的轴向压力-水平位移或轴向压力-应变曲线的形状和局部屈曲模式有关；在翼缘宽厚比为28.1～56.3、腹板高厚比为40.2～80.4、偏心距为20～50 mm范围之内，EN 1993-1和GB 50017—2017中的屈曲后强度计算公式仍然适用于Q460C和Q690D钢焊接箱形截面压弯构件，而ANSI/AISC 360-16中的相关公式需要进一步修正。     

高强方钢管高强混凝土短柱轴压性能

选取四种混凝土本构关系模型,应用有限元分析软件ABAQUS建立高强方钢管高强混凝土轴压短柱有限元分析模型,再通过试验研究加以验证。结果表明:采用韩林海提出的约束混凝土本构关系模型的有限元计算结果与试验结果吻合较好。在此基础上,研究了含钢率、钢材屈服强度和混凝土强度对模型混凝土贡献比(CCR)及跨中截面钢管应力的影响。最后,提出了高强方钢管高强混凝土轴压短柱组合构件受力全过程应力-应变关系曲线表达式,计算结果与试验结果吻合较好,验证了公式的准确性。     

高强H形钢混凝土组合柱偏心受压性能试验研究

为研究高强H形钢混凝土组合柱的偏心受压性能以及验证采用国内外相关规范计算此类构件承载力的可行性,进行了1∶3缩尺的10根内置Q460、Q690高强H形钢混凝土组合柱与2根内置Q235普通H形钢混凝土组合柱的偏心受压试验,研究型钢钢材牌号、相对偏心距、含钢率与箍筋间距对组合柱偏压承载力与延性的影响。研究结果表明：当型钢钢材牌号由Q235提升至Q460、Q690时,组合柱的承载力和延性均有明显提升,型钢钢材牌号为Q690的组合柱承载力提高幅度略高于Q460的,其位移延性系数提高幅度明显高于Q460的;增大相对偏心距和含钢率可显著提升高强H形钢混凝土组合柱的延性;较小箍筋间距有利于充分发挥Q690高强H形钢的材料性能。将试验结果与按我国JGJ 138—2016《组合结构设计规范》、欧洲EN 1994-1-1:2004以及美国ANSI/AISC360-16得到的型钢组合柱偏压承载力计算结果进行对比。结果表明,按EN 1994-1-1:2004、ANSI/AISC360-16得到的高强H形钢组合柱偏压承载力计算结果与试验结果相差较大,总体上偏于保守;按JGJ 138—2016的计算结果与试验结果...     

混合高强钢框架极限承载性能有限元分析

混合高强钢框架是一种钢梁采用低强钢材(Q235,Q345),钢柱采用高强钢材(Q460,Q690)的新型抗弯钢框架结构体系。为研究不同钢材强度等级对混合高强钢框架承载性能的影响规律,采用有限元软件Abaqus对钢框架进行非线性分析。在试验验证的基础上,建立五榀单跨两层混合高强钢框架模型以及两榀普通低强钢框架有限元模型,对其承载性能与用钢量进行研究,比较各种抗弯钢框架结构的承载能力、变形能力、延性以及用钢量。研究结果表明:若合理选用梁柱的钢材强度等级,特别是钢梁选用较低的钢材(Q235)而钢柱选用高强钢材,混合高强钢框架可以获得比普通钢框架更好的承载能力、刚度与延性性能,并且可以节省18.3%的钢材,具有较好的经济效益。     

单轴偏压下高强钢热轧椭圆空心柱的数值模拟

利用四节点减缩积分壳单元模拟了椭圆空心截面柱,研究了单轴偏压下高强钢热轧椭圆空心截面柱的力学性能,讨论了热轧椭圆空心截面柱的长外径、短外径、厚度、偏心距及高强钢材料属性对单轴偏压下热轧椭圆空心柱承载能力的影响.结果表明,现有的设计规范如EN 1993-1-1、BS 5950-1、AS4100和Gardner公式等都可以...     

高强钢焊接薄壁箱形截面双向压弯构件局部和整体相关屈曲试验研究

通过13个Q460C、Q550D和Q690D钢中长柱的双向偏压试验,研究了高强钢焊接薄壁箱形截面双向压弯构件的局部-整体相关屈曲性能和极限承载力;将极限承载力与美国、欧洲规范以及新提出的计算公式的计算结果相比较,以验证它们对高强钢焊接薄壁箱形截面双向压弯构件局部-整体相关屈曲计算的适用性。结果表明,在钢材名义屈服强度fy=460～690 MPa,板件宽厚比b/t=40～70,构件长细比λ=45～79,偏心距ex=ey=20～45 mm范围内,美国规范ANSI/AISC 360-16对较大长细比（λ=79）和Q690D钢较小宽厚比（b/t=40）试件的计算结果偏于保守;欧洲规范BS EN 1993-1-1对较小板件宽厚比（b/t=40）试件的计算结果偏于保守,对其余试件是安全的;使用新提出的有效屈服强度法所得到的计算结果和试验结果吻合良好;新提出的有效截面法对大部分试件的计算结果偏于保守。     

Influence of concrete strength and length/diameter on the axial capacity of CFT columns

This paper presents an experimental analysis of the confinement effects in steel–concrete composite columns regarding two parameters: concrete compressive strength and column slenderness. Sixteen concrete-filled steel tubular columns with circular cross section were tested under axial loading. The tested columns were filled by concrete with compressive strengths of 30, 60, 80, and 100 MPa, and had length/diameter ratios of 3, 5, 7, and 10. The experimental values of the columns’ ultimate load were compared to the predictions of 4 code provisions: the Brazilian Code NBR 8800:2008, Eurocode 4 (EN 1994-1-1:2004), AINSI/AISC 360:2005, and CAN/CSA S16-01:2001. According to the results, the load capacity of the composite columns increased with increasing concrete strength and decreased with increasing length/diameter ratio. In general, the code provisions were highly accurate in the prediction of column capacity. Among them, the Brazilian Code was the most conservative, while Eurocode 4 presented the values closest to the experimental results.     

Ultimate flexural strengths of plate girders subjected to web local buckling

The ultimate flexural strengths of bisymmetric and monosymmetric I-girders subjected to local bend-buckling in webs have been investigated by nonlinear finite element analysis incorporating post-buckling behaviors. The plate girders fabricated with high performance steel (HPS) and conventional steel were modeled three-dimensionally with thin shell elements and ultimate strength analyses were conducted utilizing versatile nonlinear techniques provided by a commercial finite element analysis (FEA) package program, ABAQUS. The constitutive relationship for both HPS and conventional steel was assumed to be elasto-plastic strain-hardening, and the initial imperfections were considered in the web panels and the residual stresses were imposed on the hypothetical built-up sections. The ultimate flexural strengths of girders with various slenderness of web were evaluated from the nonlinear FEA and compared with values predicted by the specifications in AASHTO LRFD and Eurocode 3. It has been found that the current flexural strength formulas for conventional steel girders from AASHTO LRFD and Eurocode 3 can be extended to application for HPS girders without modification.     

Empirical formulations for estimation of ultimate strength of continuous stiffened aluminium plates under combined in-plane compression and lateral pressure

The present research was undertaken based on the results obtained by the same authors in a sensitivity study on the buckling and ultimate strength of continuous stiffened aluminium plates. Empirical expressions are developed for predicting ultimate compressive strength of welded stiffened aluminium plates used in marine applications under combined in-plane axial compression and different levels of lateral pressure. Existing data of the ultimate compressive strength for stiffened aluminium plates numerically obtained by the authors through the previously performed sensitivity analysis are used for deriving formulations that are expressed as functions of two parameters, namely the plate slenderness ratio and the column (stiffener) slenderness ratio. Regression analysis is used in order to derive the empirical formulations. The formulae implicitly include effects of the weld on initial imperfections, and the heat-affected zone.     

Numerical study on the permissible gap of intermittent fillet welds of longitudinally stiffened plates under in plane axial compression

Intermittent fillet welding of stiffeners to plates and its influence on the collapse behaviour of stiffened plates is investigated applying the finite element method. Special attention is paid to the modelling of the fillet welds at the plate-to-stiffener junction. Some available experimental results are simulated in order to obtain reliable numerical results. A series of numerical analyses of stiffened steel plates subjected to an in plane axial compressive load has been performed. Stiffened plates are selected from the deck structure of real sea-going ships and inland waterway vessels. Complete equilibrium paths are traced up to collapse for the non-linear elastoplastic response of stiffened plates. Finally a proposal is presented for the permissible gap of welds in intermittent fillet welding of stiffened plates.     

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.     

火灾下带肋薄壁方钢管混凝土柱承载力分析

对带肋薄壁方钢管混凝土柱在火灾下的承载力进行了分析,考察了各重要参数对构件承载力影响系数的影响。结果表明:在火灾作用下,带肋薄壁方钢管混凝土柱的承载力损失较为严重,在一定参数范围内,截面尺寸、构件长细比和防火保护层厚度对火灾下构件承载力影响系数的影响较大,荷载偏心率、截面含钢率的影响次之,钢管屈服强度、加劲肋屈服强度、混凝土抗压强度的影响较小,加劲肋宽厚比在荷载比≤0.3且宽厚比≤25的情况下有一定影响。在构件外表面采用防火保护能有效提高耐火极限,而且厚涂型钢结构防火涂料的效果明显优于水泥砂浆保护层。     

Calculating the buckling strength of steel plates exposed to fire

The local buckling capacity of fire-exposed steel cross sections is affected by the reduction in strength and stiffness associated with an increase in steel temperature. Using a stress-based approach, simple continuous equations that account for these reductions are proposed in this paper to calculate the ultimate strength of thin steel plates (i.e. idealized webs and flanges) at elevated temperature. Calculations made using the proposed equations show good agreement with computational results for a range of temperatures, boundary conditions, and loading scenarios. Comparisons with the results of previously published experiments show that the proposed approach provides a conservative prediction of experimentally measured buckling strengths of heated steel sections with thin plates. The proposed equations for calculating ultimate plate strength at elevated temperature offer a significant improvement over current AISC methods, which do not include an explicit temperature-based reduction of buckling capacity. The proposed equations are also a slight improvement over current Eurocode methods, which may become discontinuous for smaller values of plate slenderness. The proposed approach also has greater similarity to current North American standards than those of Eurocode.     

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.     

带肋冷弯薄壁方钢管混凝土柱滞回性能研究

对3根带肋冷弯薄壁方钢管混凝土柱进行滞回试验,主要参数为轴压比。试验结果表明：纵向加劲肋有效延缓了钢管壁局部屈曲的发生;其滞回曲线饱满,具有良好的耗能能力;随着轴压比的增大,柱承载力略有增大,而延性、耗能能力则明显减小;当横向位移大于6倍的屈服位移时,大轴压比的刚度退化速度最快。建立了该类试件的有限元模型,对比可得有限元模拟结果与试验结果吻合较好。基于有限元模型对该类构件开展机理分析和参数分析。结果表明：在带肋冷弯薄壁方钢管的约束下,核心混凝土的强度得到了较大提高;钢管局部屈曲发生在峰值荷载后,局部屈曲只发生在纵向加劲肋和钢管角部间;材料强度、轴压比、钢管宽厚比和长细比等参数对该类构件的承载力有较大影响;混凝土强度、轴压比和长细比对荷载-位移骨架曲线形状有较大影响。基于参数分析建议了该类构件的简化滞回模型,简化计算结果和有限元计算结果吻合较好。     

Ultimate capacity of battened columns composed of four equal slender angles

Cold-formed steel structural members play a great role in modern steel structures due to their high strength and light weight. The behavior and strength of battened column members composed of slender angle sections are mainly governed by local buckling of angle legs or torsional buckling of the angle between batten plates. Moreover, local buckling depends on the interaction between the width–thickness ratio of angle leg, overall slenderness ratio of angle between batten plates and overall slenderness of column. Theoretical study has been carried out by a nonlinear material and geometrical finite element model. Numerous cases of slender battened column sections having different width–thickness angle leg ratios, overall slenderness ratios between batten plates and overall slenderness ratios are chosen in this study. Complete ultimate strength curves are drawn and different failure modes are studied by taking different member lengths, which produce local or torsional buckling of single angles between batten plates or overall buckling of the member. Empirical equations for the effect of shear deformation factor and the ultimate axial load capacities of members formed of battened slender angle sections are proposed. Strengths of axially loaded battened members predicted using finite element as well as the proposed empirical equations is compared with the design strengths obtained using North American and European codes. It is concluded that the design strengths predicted by North American and European codes are generally conservative, and these design rules have been shown to be reliable using reliability analysis.