基于欧洲规范4的组合梁及蜂窝梁简化弹塑性分析

当考虑大应变时梁抗弯能力的增强及钢与混凝土之间的相对滑移时,组合梁的弹塑性分析很重要。通过将组合横截面的平衡考虑为应变分布的函数,提出了一种简化弹塑性分析方法。采用抛物线-矩形应力块单元模拟混凝土,当应变超过0.0035时,混凝土强度退化。将组合梁的抗弯能力表示为下翼缘应变的函数,并与基于欧洲规范4和美国AISCLRFD规范的全塑型设计进行比较。研究了各种参数对组合梁塑性抗弯能力的影响,如:截面不对称、钢材强度、设置或不设支撑、大应变时钢材的应变硬化及混凝土的强度退化、界面滑移、梁腹板开口等。对有支撑梁,达到2～4倍屈服应变时,组合梁达到95%的塑性抗弯能力;对无支撑梁,达到5～10倍屈服应变时,组合梁达到95%的塑性抗弯能力。考虑钢材的应变硬化时0.95的极限塑性弯矩对应的下翼缘应变比不考虑应变硬化减小了30%。     

钢-混凝土组合梁在负弯矩作用下抗剪性能的试验研究

通过3根钢-混凝土组合梁在负弯矩作用下的试验,研究了其变形发展及破坏过程,得到了组合梁的跨中剪力-挠度曲线、交界面滑移曲线和沿截面高度分布的应变变化曲线,分析了剪切连接程度、截面尺寸、剪跨比、材料强度、钢筋配置等因素对组合梁承载力和延性的影响。对钢梁进行了塑性分析,得出在负弯矩作用下钢-混凝土组合梁抗剪承载力的提高不是由于钢梁腹板的硬化效应所致,而是由于混凝土翼板的贡献,并提出了考虑混凝土翼板影响的组合梁在负弯矩作用下抗剪承载力计算公式。将计算结果与实测结果进行了比较,二者吻合良好。     

Study of partially encased composite beams with innovative position of stud bolts

In this article, static behavior of three partially encased composite beams under flexural condition is investigated in the context of studying some alternative positions for the headed studs. Shear resistance between the I-shaped beam and the concrete was provided by headed studs in two positions: vertically welded on the bottom flange and horizontally welded on the faces of the web. Experimental results show that the headed studs provide the composite action and increase the bending strength. The most remarkable position seems to be the headed studs vertically welded on the bottom flange. An analytical method to estimate the bending capacity of the encased beams is also proposed, giving a good prediction of the experimental results     

部分外包混凝土简支组合梁受弯性能试验研究

为了研究部分外包混凝土组合梁在正弯矩作用下的受力性能,考察钢梁腹部钢筋混凝土对组合梁承载力及刚度的影响,对4根简支梁试件进行了试验研究,其中包括1根普通钢-混凝土组合梁试件和3根钢梁腹板与腹部混凝土界面采用不同连接方式的部分外包组合梁试件。试验结果表明：钢梁腹板与腹部混凝土界面采用不同连接方式对部分外包组合梁的受弯承载力和刚度没有显著的影响;与普通钢－混凝土组合梁相比,由于钢梁腹部钢筋混凝土的贡献,部分外包组合梁的受弯承载力和抵抗变形的能力均有较大的提高;承载力极限状态时部分外包组合梁中钢梁与腹部混凝土之间的相对滑移值较小,其滑移效应对组合梁截面受弯承载力的影响可以忽略不计。在试验研究的基础上,推导了部分外包组合梁塑性受弯承载力的计算公式,计算结果表明,简化塑性理论可以较准确地预测该类组合梁的受弯承载力。     

Full-scale long-term experiments of simply supported composite beams with solid slabs

This paper presents an experimental study aimed at the evaluation of the long-term behaviour of composite steel-concrete beams designed with partial shear connection formed by a steel joist and a solid concrete slab. Three full-scale simply supported beams with identical spans and cross-sections were prepared and tested. These specimens were designed as secondary beams of a typical composite flooring system based on Australian guidelines with the lowest permitted level of degree of shear connection of 0.5. They were cast simultaneously to enable comparisons with respect to pouring and loading conditions. One beam was cast un-propped and was kept unloaded for the whole duration of the long-term tests to measure shrinkage effects. The remaining two beams, cast under un-propped and propped conditions, respectively, were subjected to a sustained uniformly distributed load. Standard short-term and long-term tests were carried out to obtain the relevant material properties of both the steel and the concrete. Short-term and long-term push-out tests were carried out to obtain information on the response of the shear connectors. The experimental results were modelled by means of the finite element method. The time-dependent behaviour was depicted using a step-by-step procedure, while the steel joist and reinforcement were assumed to remain linear elastic. Two constitutive relationships were adopted for the shear connection, i.e., a linear-elastic one, and a new time-dependent one, to account for the long-term effects produced in the complex stress state of the concrete surrounding the shear connectors. The latter representation is intended to fall within the framework of simplified approaches suitable for design applications. Considerations of the accuracy of the numerical predictions are presented based on the two shear connection models.     

钢-高强混凝土组合梁的试验研究

为了研究钢-高强混凝土组合梁在静载作用下的抗弯性能,本文完成了8根钢-高强混凝土组合梁在跨中两点对称荷载作用下的试验,对其受力性能进行了分析,并探讨了翼缘板混凝土强度、钢梁屈服强度和翼缘板宽度对组合梁正截面受弯承载力、延性的影响。结合试验结果和理论分析,对现行规范中组合梁正截面受弯承载力计算公式进行了补充修正,以拓宽计算公式中翼缘板混凝土强度的适用范围,为高强混凝土在钢-混凝土组合梁中的应用提供设计依据。     

Experimental study of prestressed steel-concrete composite beams with external tendons for negative moments

Four groups of prestressed steel-concrete composite beams with external tendons in negative moment regions were tested, and the cracking behaviours and the ultimate negative moment resistances of the composite beams were investigated experimentally. It is found that in hogging moment regions, on adding prestressing to the composite beams with external tendons, the cracking resistance of the beams can be effectively increased; however, the incremental internal tendon forces of the prestressed composite beams are rather small, and therefore can be neglected in the evaluation of the negative moment resistance of the beams. In hogging moment regions, the ultimate resistance of a composite beam prestressed with external tendons is governed by either distortional lateral buckling or local buckling, or an interactive mode composed of the two bucklings. For a beam with a compact section, the negative bending moment can reach the plastic moment when the steel section is fully plastic, and for a non-compact section, the negative bending moment is limited to the yield moment at which the compression steel flange initiates yield. The method for evaluating the buckling resistance of the composite beams is discussed, and a tentative design method based on BS5400: Part 3 is proposed to assess the buckling resistances of the prestressed composite beams.     

Experimental study on shear behavior of box section bamboo-steel composite beams

为研究以冷弯薄壁型钢和竹材人造板通过结构胶复合而成的箱形截面钢-竹组合梁的受剪性能,以梁截面的翼缘及腹板竹胶板厚度、型钢翼缘宽度和剪跨比等为主要参数,对6根钢-竹组合箱形梁进行受剪试验,观察各级荷载作用下组合梁的应变和挠度发展,分析其破坏过程和破坏机理,研究组合梁受剪性能的影响因素,探讨钢-竹组合箱形梁的受剪承载力及变形计算方法。研究结果表明：钢-竹组合箱形梁整体工作性能优良且组合效应显著,其受力过程经历弹性和弹塑性两个阶段,具有良好的延性和安全储备;增加翼缘和腹板处竹胶板厚度可提高组合梁的受剪承载力,减小剪跨比可有效提高组合梁的受剪能力,同时适当减小型钢翼缘宽度能使梁的受剪性能进一步增强;采用所提出的组合梁的跨中挠度计算公式得到的计算值与试验值吻合较好,组合梁受剪承载力的计算公式所得结果偏于保守。     

Bending and rotational behaviour of semi-continuous composite beams

Stresses and deflections were measured in various semi-continuous composite beams. The bending and rotational capacities of the composite connections were measured in terms of beam curvatures and deflections by using two full-scale semi-rigid composite frames with monotonic loadings. The effect of semi-rigid connections on the performance of composite beams with various loadings was compared with predictions and codes. The tests show that the semi-continuous composite beams are more economic and effective than the simple or continuous composite beams. The semi-rigid connections affect the bending capacities and beam deflections, so the connection behavior should be considered in the design of composite beams. Yielding analysis of the steel beam bottom flange has some influence on the deflection calculation of composite beams. __________ Translated from J Tsinghua Univ (Sci & Tech), 2007, 47(3): 313–318 [译自: 清华大学学报(自然科学版)]     

凹槽销栓型竹-混凝土组合梁的受弯性能

文章将混凝土与竹材组合,提出一种新型凹槽销栓型竹-混凝土组合结构,为研究凹槽销栓型竹-混凝土组合梁的受弯力学性能,对5组组合梁和1组对比竹梁进行四点弯曲试验,试验参数包括连接件间距及其数量,试验主要测试试验荷载、跨中挠度、竹梁与混凝土翼缘的应变以及竹梁与混凝土翼缘的界面相对滑移。试验结果表明,凹槽销栓型竹-混凝土组合梁的破坏模式表现为两种：第Ⅰ类以混凝土翼缘斜向剪切破坏为控制,脆性特征明显,发生于连接件间距较密时;第Ⅱ类是以凹槽混凝土剪压破坏为控制,发生于连接件间距较疏时,连接件的凹槽内混凝土破损严重,破坏之前有明显的预兆。相对于对比竹梁,组合梁在各级荷载下的跨中位移大幅降低,截面刚度得到大幅度的提高,与对比竹梁相比,组合梁的承载力提高了1.23～1.61倍,对应跨中挠度为L/250和L/300时的荷载PL/250和PL/300平均提高了3.81倍和3.95倍,在正常使用荷载下,凹槽销栓型竹-混凝土组合梁的组合系数为0.86～0.98,组合截面的混凝土和竹材两种材料呈现良好的整体工作状态,凹槽销栓型连接件表现出刚性连接件的特征,具有较高的组合系数。     

Numerical analysis on mechanical behavior of steel-concrete composite beams under fire

This paper investigated the fire behavior of steel-concrete composite beams (SCB) and partially encased steel-concrete composite beams (PEB) through numerical analysis. The numerical models established by the software ABAQUS were verified against experimental results. Parametric studies were performed to study the influences of load ratio, strength of concrete and steel, width of concrete slab, size of steel beam, fire protection layer, and degree of shear connection on the fire behavior of SCB and PEB. The analysis results show that the deformation stages of SCB and PEB under fire both go through four stages: elastic, elastic–plastic, plastic small deformation, and plastic large deformation. The web of SCB experiences a tension–compression–tension process under fire, and the bottom flange of PEB may even change from tension to compression at a lower load ratio. The failure mode of PEB, whether the concrete is crushed, depends on the load ratio. When SCB fails, the concrete is crushed and only the bottom flange of the steel beam yields. Under various parameters, the fire resistance of SCB is about 22 min, while the fire resistance of PEB is 82–93 min under a load of 0.4. When the load ratio increases from 0.2 to 0.6, the fire resistance of SCB decreases by 8 min, while that of PEB decreases by 110 min. To meet class I fire resistance rating under a normal service load ratio of 0.4, additional measures for PEB are still required, and at least 15 mm of fire protection layer is required for the steel beam of SCB. Finally, considering the temperature internal fore, a coefficient related to the fire time was introduced to modify the formula of ultimate flexural capacity of SCB and PEB, which showed good accuracy.     

高强钢-混凝土组合梁受弯性能试验研究

为研究高强钢-混凝土组合梁在静载作用下的受弯性能,共进行了8根简支梁在跨中两点对称荷载作用下的试验。8根试件均为完全剪力连接,主要变化参数为混凝土强度等级和钢梁强度等级。加载方式为单调静力加载,试验测量内容主要为竖向加载荷载、挠度、截面应变等。试验结果表明,所有试件均发生典型的弯曲破坏,高强钢与混凝土通过栓钉连接表现出良好的整体工作性能。现行规范中的简化塑性计算方法可以较准确地预测该类型梁的极限受弯承载力。根据该塑性理论方法,对组合梁进行了参数分析,主要变化参数为混凝土强度等级和钢梁强度等级。分析表明,其他条件相同时,相比混凝土强度,钢梁强度是影响组合梁受弯承载力的主要因素。研究为高强钢在组合梁中的应用提供了试验依据。     

Local/distortional mode interaction in cold-formed steel lipped channel beams

This paper reports a numerical investigation concerning the post-buckling behaviour of cold-formed steel lipped channel beams, subjected to uniform major axis bending, affected by local/distortional mode interaction – the results presented and discussed were obtained through shell finite element analyses performed using the code Abaqus. One analyses simply supported beams (locally/globally pinned and free to warp end sections) (i) with cross-section dimensions ensuring coincident local and distortional critical buckling moments and (ii) having critical-mode initial geometrical imperfections with different shapes and the same overall amplitude – local buckling is triggered either by the compressed flange (most common case) or by the web. The results reported consist of (i) elastic and elastic–plastic post-buckling equilibrium paths, (ii) curves and figures showing how the beam deformed configuration evolves along those paths and, for the elastic–plastic beams, (iii) figures making it possible to visualise (iii₁) the location and growth of plastic strains and (iii₂) the nature of the failure mechanisms detected.     

Ultimate load analysis of thin-walled box beams considering shear lag effect

In this paper, the ultimate load of thin-walled box beams undergoing limited plastic strain is investigated with consideration of shear lag effect on the basis of the stress–strain relationship of elastic, linearly hardening materials. In the procedure, calculation formulae for strength increase coefficient, flange effective width ratio, critical values of plastic strain and shear lag coefficient are obtained for thin-walled box beams with elastic, linearly hardening materials. In addition, the relationships among the abovementioned parameters and conditions of boundary, load and aspect ratio L/2b (span length/beam width) of the box beams are established in this paper. For illustration, the numerical results of box beams under certain boundary and load conditions are presented and some conclusions are drawn which may offer references for the application of this procedure in structural design.     

波形钢腹板体外预应力组合梁正截面承载力及应力分布特征研究

为研究预应力状态下波形钢腹板组合梁的截面应力分布特征,设计制作2根波形钢腹板组合梁,在预应力筋张拉过程中研究了预应力对组合梁受弯截面应力分布特征的影响,通过正截面受弯试验对试件塑性承载力先进行测定;对体外预应力组合梁正截面承载力进行了理论分析;利用有限元分析软件,对与试件同类型的波形钢腹板体外预应力组合梁的塑性受弯承载力进行了参数分析,研究了腹板高度和混凝土强度对正截面承载力的影响。结果表明：预应力对此类构件的翼缘应变变化量影响较波形钢腹板的大约2~3倍;预应力损失对截面中性轴位置变化影响可忽略不计;施加预应力将使波形钢腹板组合梁的受弯承载力提高约30%,腹板高度等参数与此类结构跨中截面承载力呈线性关系;理论值与有限元模拟结果吻合良好,验证了所提出正截面承载力理论的准确性。     

Bending and rotational behaviour of semi-continuous composite beams

Stresses and deflections were measured in various semi-continuous composite beams. The bending and rotational capacities of the composite connections were measured in terms of beam curvatures and deflections by using two full-scale semi-rigid composite frames with monotonic loadings. The effect of semi-rigid connections on the performance of composite beams with various loadings was compared with predictions and codes. The tests show that the semi-continuous composite beams are more economic and effective than the simple or continuous composite beams. The semi-rigid connections affect the bending capacities and beam deflections, so the connection behavior should be considered in the design of composite beams. Yielding analysis of the steel beam bottom flange has some influence on the deflection calculation of composite beams.     

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。     

钢-ECC组合梁负弯矩区受弯性能试验研究

纤维增强水泥基复合材料（Engineered Cementitious Composite,ECC）具有高延展性以及受拉刚化特点,应用于组合梁桥的负弯矩区时可有效减少桥面板的受拉开裂。完成了2根钢-ECC组合梁和1根钢-混凝土组合梁对比构件在负弯矩作用下的静力加载试验,通过试验研究了不同配筋率的ECC对结构受力性能特别是抗裂性的影响。试验研究表明：在负弯矩作用下,钢-ECC组合梁的刚度较钢-混凝土组合梁明显提高|由于ECC翼板的抗拉作用导致截面中和轴上升,钢梁受压区增大,构件延性有所降低|钢-ECC组合梁可有效提高结构的开裂荷载并减小裂缝宽度,提高配筋率有利于进一步减少ECC翼板的裂缝宽度。提出了钢-ECC组合梁的承载力与开裂荷载的计算方法,提供了挠度分析的方法和裂缝宽度的基本模型。     

考虑楼板组合作用的方钢管混凝土组合框架受力性能有限元分析

为了对组合框架结构的抗震性能进行深入的研究,基于方钢管混凝土组合框架低周往复荷载试验的足尺试件,采用通用有限元软件Msc.Marc建立了壳-实体精细非线性有限元分析模型,考虑了钢材及混凝土的弹塑性性能,混凝土的开裂及受拉软化,钢梁与混凝土楼板交界面的滑移以及钢梁下翼缘断裂等非线性因素,对4榀组合框架及2榀组合节点进行了...