Behaviour of embedded steel plate in composite coupling beams

Plate-reinforced composite (PRC) coupling beam is fabricated by embedding a vertical steel plate into a conventional-reinforced concrete coupling beam to enhance its strength and ductility. Shear studs are welded on the steel plate surfaces to allow for proper load transfer between the concrete and steel plate. The present study focuses on the evaluation of internal load distributions and load sharing on the embedded steel plate as well as at the shear studs in composite coupling beams using the nonlinear finite element package ATENA. The proposed two-dimensional finite element model is able to simulate the overall load-deflection behaviour and internal load distributions of coupling beams subjected to bending and shear forces. The reliability of the model is demonstrated by comparisons with the available experimental results. This is followed by an extensive and carefully planned parametric study using the calibrated finite element model. Numerical results on the effects of steel plate geometry, span-depth ratio of beams and steel reinforcement ratios at beam spans and in wall regions are presented and discussed in this paper. The finite element model provides a better understanding of the behaviour of shear studs as well as plate anchorage in the wall regions and embedded beam region. Based on the numerical results, equations for quantifying the shear stud forces are established and a set of non-dimensional design charts for determining the internal forces of the embedded steel plates is constructed. Both of them are useful for engineers to design PRC coupling beams.     

钢筋混凝土梁受剪承载力可靠度分析

在GB 50010-2010《混凝土结构设计规范》修订过程中,所参考的试验数据主要来自85版设计规范背景资料,其构件数量及试验参数取值范围均存在一定的局限性。通过收集并整理国内外的钢筋混凝土矩形截面简支梁受剪试验数据,对GB 50010-2010《混凝土结构设计规范》中钢筋混凝土梁受剪承载力计算公式的合理性进行分析,得到计算模式不定性的统计参数,并采用考虑基本变量概率分布类型的一次二阶矩方法进行可靠度分析。结果表明：GB 50010-2010《混凝土结构设计规范》中均布荷载作用下钢筋混凝土梁受剪承载力的可靠指标能够满足GB 50068-2001《建筑结构可靠度设计统一标准》的要求;集中荷载作用下钢筋混凝土梁受剪承载力计算公式拟合曲线不再是更新后的试验数据的下包线,其可靠指标既不能满足GB 50068-2001《建筑结构可靠度设计统一标准》的基本要求,也明显低于正截面受弯承载力的可靠指标。建议GB 50010-2010在全面更新试验数据的基础上,校准钢筋混凝土梁承载力计算公式的可靠度。     

考虑剪切和轴向效应的半刚性连接Timoshenko梁柱的大挠度和后屈曲性态

研究Timoshenko梁-柱的非线性大挠度-小应变分析和后屈曲行为。这种梁具有半刚性连接的对称横截面,其连接经受保守和非保守端部荷载(力和弯矩)作用,分析中将组合剪切作用、轴向和弯曲变形、轴向偏心力、水平支撑和移位等都简化为单一的荷载作用。基于改进的剪力公式,推导出一套包括剪切变形和轴向外力导致的剪力等效应的函数集合。同时,还推出了因梁柱在端部力和弯矩作用下弯曲而产生的轴向位移δb的表达方式。尽管只是近似推算,但所提出的方法和相应的非线性方程,却可以用于带刚性、半刚性连接和铰接的Timoshenko梁-柱的拉压稳定性和非线性大挠度-小应变弹性分析。分析研究表明,剪切变形增加了纵横向的挠度,减小了梁柱由于轴向压力而产生的屈曲。在具有相对低效剪力区域或低抗剪刚度的梁柱分析中必须考虑剪切变形的作用。剪切效应在板式橡胶支座的拉压稳定性和动力特性方面的影响上同样非常重要。采用4个范例说明该方法和公式的有效性。     

Nonlinear finite element analysis of concrete filled steel plate composite coupling beams: force and deformation mechanics

在外包钢板-混凝土组合连梁试验研究的基础上,对组合连梁试件和不同参数取值的补充模型进行了非线性有限元分析。有限元分析得到的滞回曲线与试验曲线吻合良好,能较好地模拟组合连梁的受力行为。通过应力分析,发现内填混凝土的工作机制类似于斜压杆,其压力沿着连梁对角线方向从一端的受压侧传递到另一端的受压侧。外包钢板承担的剪力比例和弯矩比例的范围分别为0.36~0.76和0.57~0.82;混凝土的剪力与轴压力之比和连梁的高跨比近似相等。连梁的侧向位移由节点区变形引起的梁端转角、连梁的弯曲变形与剪切变形产生;在常用的跨高比范围内,剪切变形产生的侧向位移在总位移中占有较大比例,且受跨高比的影响很大。     

复合荷载作用下钢梁弯扭屈曲的临界弯矩: (Ⅱ)系数计算及数值算例

基于平面外4种边界约束条件简支钢梁在满跨均布荷载、跨中对称集中荷载和端弯矩作用下,以及平面外4种边界约束条件固支钢梁在满跨均布荷载、跨中对称集中荷载作用下的Mcr三系数(C1,i、C2,i、C3,i)计算式,计算了典型单一荷载工况的Mcr三系数数值,给出了横向荷载与端弯矩共同作用简支钢梁以及横向荷载两两共同作用固支钢梁的复合弯矩系数Cb计算式,通过数值算例验证了本文Mcr三系数和复合弯矩系数计算式的精度。最后对比了本文的Mcr三系数数值与EN 1999 1 1: 2007和ENV 1993 1 1: 1992中单一荷载的Mcr三系数数值,校验了“4M”等效弯矩系数计算式对简支钢梁、固支钢梁的适用性。结果表明：对于除平面外边界约束条件为R R(平面外两端简支且约束转动)外的单轴或双轴对称截面简支钢梁以及双轴对称截面固支钢梁,单一荷载的Mcr三系数的数值或计算式以及复合弯矩系数计算式均具有较高精度;EN 1999 1 1: 2007和ENV 1993 1 1: 1992中部分工况的C2,i和C3,i不精确;现有“4M”等效弯矩系数计算式仅能用于计算平面内外简支钢梁的Cb或C1,i。     

钢筋混凝土界面抗剪承载力可靠度对比分析

对中国规范、美国规范及欧洲规范中钢筋混凝土构件界面抗剪承载力的可靠度进行了对比分析。分析中作用、材料强度和几何尺寸采用相关研究报告或相关文献提供的概率分布和统计参数,抗剪承载力计算模式不定性统计参数采用国内外127个钢筋混凝土构件抗剪承载力的试验结果与计算结果的分析值。结果表明:规范GB 50010—2002界面抗剪承载力的计算可靠指标最小,未能达到目标可靠指标要求;其余规范公式的计算可靠指标均能满足目标可靠指标要求,其中JGJ 1—91与EN 1992—1—1:2004公式的计算可靠指标较大,偏于保守;ACI 318—08的可靠指标介于中间并与目标可靠指标接近。     

Theoretical model of the determination of the deformation rates of RC beams

A theoretical model for the determination of the moment vs. curvature, and shear force vs. shear deformation relationships based on the stress–strain curves of materials given in ENV (1991), with material characteristics obtained from the tests of concrete and steel specimens is presented. A comparison of the theoretical values with the results of tests for reinforced beams subjected to the concentrated force shows good agreement for both the curvature and shear deformations. The values of the deformation work due to bending moments as well as those due to shear forces were also determined.     

Behaviour of column web component of steel beam-to-column joints at elevated temperatures

This paper presents an experimental investigation on stocky column web panels of semi-rigid beam-to-column joints exposed to fire conditions in order to verify an analytical prediction model. Recent experimental studies show that the degradation of material properties and high axial forces, due to restrained thermal expansion of beams at elevated temperatures, significantly affect the moment–rotation response of the joints. The component method originally established for the evaluation of the joint behaviour at ambient conditions can be adopted for elevated-temperature cases. Recently developed mechanical models for joints may not be accurate as the column web component is simultaneously subjected to bending moments and axial forces. This paper focuses on the component column web in shear in order to identify the key parameters which affect joint behaviour in shear at elevated temperatures. This experimental work was conducted on three extended end-plate connections subjected to both ambient and elevated temperature conditions. After validations by test results, detailed finite element simulations were performed for a series of parametric studies at other elevated temperatures. Both experimental and numerical results are finally compared with analytical predictions.     

Parametrical static analysis on group studs with typical push-out tests

Group studs are known as shear connectors in steel and concrete composite structures. By now, many composite bridges have been characterized by long lateral cantilevers. The shear studs are actually under biaxial action consisting of shear force and action in light of lateral bending moment on concrete slab induced by long cantilever and passing by moving loads. Moreover, lateral bending moment may even lead to the initiation of bending-induced concrete cracks. These two situations can both affect mechanical performance of group studs. Thus, a parametrical FEM analysis was carried out, in which damage plasticity was introduced to simulate material nonlinear behavior. In the analysis, lateral bending moments respectively inducing maximum concrete crack widths of 0.1 mm and 0.2 mm, shank diameters of 13 mm, 16 mm, 19 mm and 22 mm and stud heights including 80 mm and 100 mm were parameters. It was found that mechanical behavior of group studs with large shank diameter would be less affected by biaxial action and initial bending-induced concrete cracks seemed unfavorable to stud shear stiffness. On the other hand, typical push-out tests were executed to investigate reductions of shear stiffness and shear capacity of group studs. The reliability of FEM analysis was also verified based on the tests. In addition, stud shear capacity evaluations according to several design specifications were presented. It indicated shear capacity evaluation of Eurocode 4 got a relatively large safety factor. Moreover, the applicability of these specifications for group studs on shear capacity evaluation was also discussed.     

任意开口薄壁截面圆弧曲梁弯扭精确分析

现有薄壁曲梁弯扭理论缺乏严密的理论推导。本文基于薄壁构件分析的两个基本假定，导出了任意开口薄壁截面圆弧曲梁的翘曲位移、正应力、剪应力及其各自合力以及平衡微分方程的精确表示式。为便于应用，本文还给出了一套具有良好精度的内力简化公式及相应的平衡微分方程。     

Non-linear model for stability of thin-walled composite beams with shear deformation

A geometrically non-linear theory for thin-walled composite beams is developed for both open and closed cross-sections and taking into account shear flexibility (bending and warping shear). This non-linear formulation is used for analyzing the static stability of beams made of composite materials subjected to concentrated end moments, concentrated forces, or uniformly distributed loads. Composite is assumed to be made of symmetric balanced laminates or especially orthotropic laminates. In order to solve the non-linear differential system, Ritz's method is first applied. Then, the resulting algebraic equilibrium equations are solved by means of an incremental Newton–Rapshon method. This paper investigates numerically the flexural–torsional and lateral buckling and post-buckling behavior of simply supported beams, pointing out the influence of shear–deformation for different laminate stacking sequence and the pre-buckling deflections effect on buckling loads. The numerical results show that the classical predictions of lateral buckling are conservative when the pre-buckling displacements are not negligible, and a non-linear buckling analysis may be required for reliable solutions.     

最小配箍率下钢筋混凝土简支梁受剪性能试验研究

为研究配置最小配箍率有腹筋梁的受剪性能,以配箍率、剪跨比和混凝土强度为变量,完成了集中荷载作用下36根钢筋混凝土简支梁(12根无腹筋梁和24根有腹筋梁)的受剪性能试验,对其裂缝发展、破坏形态、临界斜裂缝倾角、主斜裂缝荷载、受剪承载力及跨中挠度等进行了分析.结果 表明,最小配箍梁与无腹筋梁的裂缝发展、破坏形态差异较大,剪...     

蜂窝梁的稳定性能研究进展

对蜂窝梁破坏模式的研究表明，失稳是其结构性能失效的重要破坏模式。为此，在回顾蜂窝梁结构特性研究的基础上，总结归纳了蜂窝梁失稳的3种主要模式：整体弯扭失稳、梁墩屈曲、畸变屈曲。结合国内外近30多年来对蜂窝梁稳定性的试验研究成果，对影响蜂窝梁稳定性的主要因素进行分析。采用蒙特卡洛法得到纯弯简支蜂窝梁弯扭失稳临界荷载的概率分布和影响因子的敏感度。将部分具有代表性的试验成果与欧洲规范EN 1993-1-1计算结果进行对比，根据中国规范GB 50068—2001《建筑结构可靠度设计统一标准》提供的抗力分项系数，计算了不同荷载组合下蜂窝梁整体弯扭失稳临界荷载的可靠度指标，为国内规范的制订提供依据。最后，总结了当前蜂窝梁稳定性研究中存在的不足，指明了进一步研究的方向。     

采用纤维梁单元分析钢-混凝土组合结构地震反应的应用

将用于钢-混凝土组合结构地震反应分析的纤维梁单元应用于各种类型构件的非线性分析中,包括普通钢筋混凝土构件（钢筋混凝土梁、钢筋混凝土柱和钢筋混凝土受弯剪力墙）、钢-混凝土组合梁构件（承受正、负弯矩的简支组合梁、连续组合梁和往复荷载作用下的组合梁）以及钢管混凝土构件（圆形、方形以及矩形轴心受压短柱构件、纯弯构件、压弯构件和往复荷载作用下的压弯构件）,数值模拟结果和试验结果均吻合良好,证明了该模型具有良好的精度以及广泛的适用性。通过对关键截面关键纤维的应力-应变发展过程进行分析,对这些构件的内在受力机理和破坏规律进行了深入的讨论。经过验证可知,开发的纤维梁单元不仅能充分兼顾准确性、通用性以及高效性,同时还具备求解速度快、数值稳定性好以及前后处理强大方便的特点,为组合结构体系的地震反应分析提供了可靠的手段。     

Behaviour of column web component of steel beam-to-column joints at elevated temperatures

This paper presents an experimental investigation on stocky column web panels of semi-rigid beam-to-column joints exposed to fire conditions in order to verify an analytical prediction model. Recent experimental studies show that the degradation of material properties and high axial forces, due to restrained thermal expansion of beams at elevated temperatures, significantly affect the moment–rotation response of the joints. The component method originally established for the evaluation of the joint behaviour at ambient conditions can be adopted for elevated-temperature cases. Recently developed mechanical models for joints may not be accurate as the column web component is simultaneously subjected to bending moments and axial forces. This paper focuses on the component column web in shear in order to identify the key parameters which affect joint behaviour in shear at elevated temperatures. This experimental work was conducted on three extended end-plate connections subjected to both ambient and elevated temperature conditions. After validations by test results, detailed finite element simulations were performed for a series of parametric studies at other elevated temperatures. Both experimental and numerical results are finally compared with analytical predictions.     

Bending analysis of partially restrained channel-section purlins subjected to up-lift loadings

Cold-formed steel section beams are widely used as the secondary structural members in buildings to support roof and side cladding or sheeting. These members are thus commonly treated as the restrained beams either fully or partially in its lateral and rotational directions. In this paper an analytical model is presented to describe the bending and twisting behaviour of partially restrained channel-section purlins when subjected to uplift loading. Formulae used to calculate the bending stresses of the roof purlins are derived by using the classical bending theory of thin-walled beams. Detailed comparisons are made between the present model and the simplified model proposed in Eurocodes (EN1993-1-3). To validate the accuracy of the present model, both available experimental data and finite element analysis results are used, from which the bending stress distributions along the lip, flange and web lines are compared with those obtained from the present and EN1993-1-3 models.     

Statistical evaluation of the lateral-torsional buckling resistance of steel I-beams, Part 1: Variability of the Eurocode 3 resistance model

The EN version of part 1-1 of EC3 introduces significant changes in the evaluation of the lateral-torsional buckling resistance of unrestrained beams, as well as alternative design procedures. Simultaneously, as a part of the preparation of the National Annexes of EC3 part 1-1 and the establishment of the corresponding NDP’s (Nationally Determined Parameters) it becomes necessary to define the partial safety coefficients for the bending resistance of beams when lateral-torsional buckling is a potential failure mode. In this paper the methodology for the resistance evaluation of beams subjected to instability is briefly described and the results are compared with FEM numerical results for the same elements. Subsequently, to assess the accuracy of the alternative design formulae, a statistical analysis of the results is performed on the basis of EN 1990-Annex D. A methodology is proposed for the evaluation of the design procedures allowing for the uncertainties in the resistance model. Results are presented for a wide set of beam geometries and loading cases and a proposal for the definition of the partial safety factor γ_rd is presented for the various methods, in line with the target failure probability of EN 1990.     

上举荷载作用下局部约束槽钢檩条的弯曲分析

建筑中,冷弯型钢梁作为次要结构构件广泛用于支撑屋顶和侧面的包覆层或挡板。因此,这些构件常被视为侧向或旋转方向受到全部或部分约束。给出描述上举荷载作用下局部约束槽钢檩条的弯曲和扭转性能的分析模型。基于薄壁梁的经典弯曲理论推导出屋顶檩条弯曲应力的计算公式。将该模型和欧洲规范(EN1993-1-3)给出的简易模型进行对比。采用该模型和EN1993-1-3分别计算沿卷边、翼缘和腹板的弯曲应力分布,并将计算结构与试验数据和有限元分析结果进行比较,验证了该模型的准确性。     

The effects of axial tension on the hogging-moment regions of composite beams

Structural parts commonly comprised of composite members such as bridge approaches, inclined parking ramps and stadium beams, can be subjected to a combination of high axial loads and bending moments. Steel-concrete composite construction is a popular solution for these types of structures due to the numerous advantages that they offer. Although, current design codes (e.g. Eurocode 4, American code AISC, Australian codes AS2327 and AS5100) provide rules for the design of composite columns subjected to flexure and axial load, however the design of composite beams, which are asymmetric in nature under the combined effects of tension and bending, is not yet fully addressed. This paper investigates the ultimate strength of composite beams under the combined effects of axial tension and negative (hogging) bending moment. An experimental programme carried out in the laboratory of the University of Western Sydney comprised of a total of six specimens representing composite beams and subjected to various levels of axial tension and bending moment. Ultimate failure modes were identified and the resulting interaction diagrams were compared to the results of sectional rigid plastic analysis. Following the tests, three-dimensional finite element models were employed using the ABAQUS finite element software to further investigate the nonlinear behaviour of the composite beams and extend the experimental observations by studying the effects of parameters such as the span length and the effect of partial shear connection. Finally, simple design rules and formulae are proposed for use in engineering practice.     

Effect of inelastic soil deformations on forces in crossed-strip foundations

Conclusions 1. Strip foundations on soils having slump-type settlements and on undermined territories should be designed with an increased pressure on the soil, which leads to a more intense redistribution of the contact pressures and to a decrease of bending moments in the case of slumping. In all cases, it is necessary to take into account residual deformations of the soil, otherwise the effect of reducing the bending moments is exaggerated and, accordingly, the reliability of the structure decreases. 2. Replacement of the p-s diagram having two explicitly expressed segments by a bilinear diagram can be used for developing engineering methods of calculation. The programs developed can also be used for calculating slabs on a nonlinear inelastic bed, with replacement of the slab by a crossed system of beams. In this case, the flexural and torsional rigidities of the replacing beams should be taken equal to Db, where D is the cylindrical rigidity of the slab and b is the width of the band being replaced. 3. Consideration of nonlinear deformation of soils leads to a substantial decrease of forces in foundations. In the calculations performed, the decrease of the maximum values of the bending moments was 30%. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 23–26, September–October, 1982.