Nonlinear analysis of composite beams subjected to combined flexure and torsion

There are situations in which a composite steel-concrete beam is subjected to torsion, such as members that are curved in plan or straight edge beams in buildings or bridges. The composite action of the steel beam and concrete slab in torsion is usually ignored in design codes of practice. Therefore, a three-dimensional (3D) finite element model is introduced in this paper to simulate composite steel-concrete beams subjected to combined flexure and torsion with the influence of partial shear connection using a commercial software ABAQUS. Brick and truss elements were used with the incorporation of nonlinear material characteristics and geometric behaviour in the model. This is coupled with an extensive parametric study using the validated finite element model using different parameters such as the span length and the level of shear connection. From the analytical study, a new phenomenon has been uncovered, which was validated by the test observation. This phenomenon called torsion induced vertical slip is an important issue, which would make the assumption plane sections remain plane invalid. In addition, difference in span length greatly affected the flexure-torsion interaction relationship of the composite steel-concrete beams, whilst the partial shear connection did not affect the relationship. Design models for readers to take away at the end of this paper are also proposed.     

弯扭作用下组合梁的非线性分析

对扭矩作用下型钢-混凝土组合梁的性能进行研究,如建筑或桥梁中的曲杆。设计规范和实际设计中常忽略扭矩作用下钢梁与混凝土板的组合效应。采用有限元软件ABAQUS,建立三维有限元模型,考虑部分剪力连接的影响,模拟弯扭作用下型钢-混凝土组合梁性能。考虑材料非线性和几何非线性,选用块单元和桁架单元进行模拟。以跨度、剪力连接水平等为参数,进行参数研究。分析发现了一个新现象,并通过试验验证。这个现象称为"扭转引起竖向滑移",它使假定平面构件发生弯曲。跨度对型钢-混凝土组合梁的弯曲-扭转效应的影响很大,而部分剪力连接却没有影响。最后,提出了设计模型。     

箱形钢-混凝土组合梁的复合弯扭试验研究

为研究钢-混凝土组合梁的弯扭性能,完成了6根箱形组合梁的纯扭和弯扭试验,详述了在不同扭弯比下箱形组合梁的受力性能及破坏形态,对裂缝发展和应力的变化情况进行了分析,揭示了箱形组合梁在弯扭复合作用下,极限扭矩和极限弯矩会相应提高的机理。对组合梁扭型破坏和弯型破坏进行了对比分析,指出了根据传统的弯剪扭相关方程而得到的相关公式的不合理性,并给出了在复合弯扭和弯剪扭下的相关公式,得到的结论能为组合梁计算和分析设计提供参考。     

抗扭钢-混凝土组合梁的构造要求和设计过程

为研究抗扭钢-混凝土组合梁的构造要求和设计过程,分析了影响组合梁抗扭强度的主要因素,结合试验和理论分析成果,对抗扭组合梁的截面尺寸、纵筋和箍筋的最大、最小配筋率和间距的构造要求作了说明。给出了抗扭混凝土翼板截面的限制条件,提出了供实际使用的抗扭组合梁的实际设计方法。     

Experimental study on curved composite beams subjected to combined flexure and torsion

There are situations in which a composite steel–concrete beam is subjected to torsion, such as members that are curved in plan or straight edge beams. The concrete slab and steel beam contribute to the torsional strength and stiffness of a composite steel–concrete beam, but this composite action is usually ignored in design codes of practice, which leads to conservative designs. Therefore, this paper investigates the ultimate strength of curved in place composite steel–concrete beams. Eight curved in plan composite steel–concrete beams have been tested under a single applied load at mid-span. Partial shear connection has also been considered in these tests. The composite steel–concrete beams have been designed with different span/radius of curvature ratios. This paper further supports the view that, in the presence of flexure, there will be an increase in the torsional moment capacity, but the flexural moment capacity does not greatly increase in the presence of torsion. A model has also been presented to represent the bending–torsion interaction for curved in plan composite steel–concrete beams with full and partial shear connection.     

Numerical study on horizontally curved steel-concrete composite beams subjected to hogging moment

The horizontally curved continuous composite steel-concrete beams, for instance, curved continuous composite bridges, have excellent qualities, such as quick construction, good seismic performance, saving construction formwork and convenience in spatial arrangement etc. At present, the application research of this kind of structures is becoming more of a concern, but very few studies have been conducted to study the mechanical performance of composite beams subjected to combined hogging (negative) bending and torsion. The purpose of the present study is to investigate the effects of curvatures on both elastic and inelastic behaviours of curved continuous steel-concrete composite beams in the interior support regions. Based on the experimental observations in a straight composite beam, a three-dimensional FE model capable of analysing the composite beams subjected to negative bending moment is built. Further numerical studies on curved composite beams with different curvatures are performed in this study. Strength and load carrying capacity, sectional strain distribution and movement of composite neutral axis before and after cracking, as well as the strain results of longitudinal reinforcing bars are investigated. Besides, the interaction equation for ultimate bending and torsional moments is proposed.     

复合弯扭下钢-混凝土组合梁连接件的设计方法

在合理假设的基础上,把受弯扭的直梁等效为受弯扭的圆弧曲梁,经过理论推导,提出了复合受扭作用下组合梁的剪力连接件简化设计计算方法,并用实际组合梁的设计算例,指出了目前仅采用受弯设计的不足.本文方法概念清晰且便于实用.     

钢-混凝土组合梁在重庆国际会展中心工程中的应用

通过重庆国际会展中心工程中钢-混凝土组合梁的设计实例,介绍组合梁的特点和基本设计思路。工程实践表明,钢-混凝土组合梁用于大跨度结构具有良好的综合效益。     

钢-混凝土组合梁滑移性能的研究与展望

钢-混凝土组合梁的研究和应用近年来发展很快,其兼有钢结构与混凝土结构两者的优点。钢梁与混凝土板界面滑移对组合梁的承载力和抗弯性能有很大影响。它在一定程度上减小组合梁刚度,增大变形,影响构件性能。通过总结目前国内外对钢-混凝土组合梁滑移性能研究以及连接件的荷载-滑移曲线公式,对钢-混凝土组合梁的研究提出了问题并进行了展望。     

开口截面钢-混凝土组合梁受扭的试验分析

为研究钢-混凝土组合梁在不同加载方式下的受扭性能,完成了6根钢-混凝土组合梁的弯扭试验和纯扭试验,其中2根梁的扭矩直接作用于工字钢梁上,其余4根梁则由钢梁和混凝土翼缘板作为整体共同受扭。试验结果表明,当扭矩直接作用于钢梁上时,混凝土翼缘板通过栓钉对钢梁的扭转提供约束,从而使钢梁的抗扭承载力比纯钢梁的提高2倍以上。在试验参数相同时,混凝土翼缘板和钢梁作为整体复合受扭时组合梁的开裂扭矩及极限抗扭承载力比扭矩直接作用于钢梁时的分别提高86%和39%。分析了两种不同加载方式下钢-混凝土组合梁受扭和受弯承载力的变化。建立了扭矩直接作用于钢梁上时极限扭矩的计算模型及计算公式。对整体受扭时组合梁的弯矩相关性进行了分析,并建立了相关曲线公式。计算结果与实测值吻合较好。     

腹板开洞压型钢板组合梁的非线性分析

钢-混凝土组合梁下通过的管道会导致建筑层高的增加而减小组合结构的优势。腹板开洞的钢-混凝土组合梁有效的减小了梁下所需的空间,从而在工程上解决了该问题。但是,洞口的存在影响了钢-混凝土组合梁的受力性能。文章利用ANSYS有限元软件对腹板开洞压型钢板组合梁进行了非线性分析,探讨了洞口处弯剪比对腹板开洞组合梁受力性能的影响。分析结果表明,洞口位置靠近加载点或者支座处都会削弱组合梁的承载力,而组合板对腹板开洞组合梁的抗剪承载力贡献很大,在计算中忽略的话是偏于保守的。     

钢-混凝土组合梁弯扭相关性的试验研究

为研究钢 混凝土组合梁的弯扭性能 ,完成了 4根组合梁的弯扭试验。详述了在不同扭弯比下组合梁的受力性能及破坏形态 ,对裂缝发展和应力的变化情况进行了分析。指出了根据传统的弯剪扭相关方程得到的极限扭矩计算公式的不合理性。根据破坏机理 ,推导出了弯扭复合作用时极限扭矩的计算公式 ,并给出了弯剪扭复合作用时的相关公式及影响因素。计算结果与试验值吻合较好     

钢-混凝土组合梁扭转的组合作用分析

在试验及理论分析的基础上,对开口截面钢-混凝土组合梁在扭转中的组合作用进行研究。组合梁在扭转中,即使是纯扭作用下,截面上仍存在组合作用,分析时不能忽略混凝土翼板和钢梁间的相互约束作用,否则会低估组合梁的抗扭能力。钢梁自身的抗扭作用很小,钢梁对组合梁扭转的贡献在于,它向混凝土翼板提供了纵向约束。在钢筋混凝土变角软化桁架模型(RA-STM)的基础上,通过引入平截面假定,以考虑组合梁扭转中的组合作用,建立适于分析开口截面钢-混凝土组合弯扭性能的三维桁架模型:在弯扭作用下,组合梁截面各单元分别处于一维应力状态(体系1)和二维应力状态(体系2),体系1用来抵抗由弯矩和扭矩引起的截面纵向应力,体系2用来抵抗由扭矩引起的截面剪应力,两者通过截面的纵向应变协调和内力平衡条件联系起来。所分析内容充分满足平衡条件、变形协调条件和材料本构方程。计算结果与试验结果吻合良好。此外还简要评价了现有的组合梁极限扭矩计算公式的不足。     

部分剪力连接钢-混凝土组合梁的非线性有限元分析

在受弯承载力和变形许可的条件下 ,钢 -混凝土组合梁采用部分剪力连接 ,不但可以降低造价 ,而且方便施工。采用大型有限元软件ANSYS作为仿真分析工具 ,通过自定义一种非线性弹簧单元 ,探讨了均布荷载作用下的钢 -混凝土简支组合梁在不同剪力连接程度系数下的受力性能 ,并将有限元计算结果与已有的试验结果作比较 ,验证了计算结果的合理性。其结论还可以指导实际工程中组合梁剪力连接程度的选择。     

Behaviour of headed stud shear connectors for composite steel-concrete beams at elevated temperatures

The behaviour of composite steel-concrete beams at elevated temperatures is an important problem. A three-dimensional push test model is developed herein with a two-dimensional temperature distribution field based on the finite element method (FEM) and which may be applied to steel-concrete composite beams. The motivation for this paper is to increase the awareness of the structural engineering community to the concepts behind composite steel-concrete structural design for fire exposure. The behaviour of reinforced concrete slabs under fire conditions strongly depends on the interaction of the slabs with the surrounding elements which include the structural steel beam, steel reinforcing and shear connectors. This study was carried out to consider the effects of elevated temperatures on the behaviour of composite steel-concrete beams for both solid and profiled steel sheeting slabs. This investigation considers the load-slip relationship and ultimate load behaviour for push tests with a three-dimensional non-linear finite element program ABAQUS. As a result of elevated temperatures, the material properties change with temperature. The studies were compared with experimental tests under both ambient and elevated temperatures. Furthermore, for the elevated temperature study, the models were loaded progressively up to the ultimate load to illustrate the capability of the structure to withstand load during a fire. It is concluded that finite element analysis showed that the shear connector strength under fire exposure was very sensitive. It is also shown that profiled steel sheeting slabs exhibit greater fire resistance when compared with that of a solid slab as a function of their ambient temperature strength.     

钢-混凝土组合梁的抗扭特点

钢-混凝土组合梁能充分发挥混凝土抗压强度高、钢材抗拉性能好的优势,近年来,在我国已得到了越来越广泛的应用。相比抗弯曲性能,目前对组合梁扭转性能的研究还很少。然而,在建筑及桥梁结构中,组合梁受扭转作用是不少的。本文介绍了开口截面组合梁和箱形组合梁的极限抗扭特点及已有的研究成果,并指出了需要进一步研究的问题。     

大跨度梁结构设计方案比选

为了使结构尽可能的优化,对上海海关专科学校教学楼报告厅大跨度梁提出了预应力混凝土梁、组合梁以及预应力组合梁三种方案,并对三种结构方案做了技术与经济性分析,其研究结果可为今后类似工程提供参考。     

钢与混凝土组合梁板结构在沉井顶板中的应用

在借鉴钢与混凝土组合梁原理的基础上,结合沉井施工工艺,研究了钢梁作为钢模板结构和作为组合梁顶板结构一部分的全过程受力机理,提出了钢与混凝土组合梁板结构在沉井顶板结构中应用的技术方案,并以内净空跨度6 m的顶板结构为例,开展了组合梁板结构的优化设计。结果表明,与现浇结构相比,组合梁板结构的施工工期短,但在设计时应考虑防水、结构耐久性等问题;组合梁中钢梁的横向布置间距可从l0/3处开始优化分析。     

Behavior of composite beams prestressed with external tendons: Experimental study

The paper deals with the failure mechanisms and behavior of composite steel-concrete beams prestressed with external tendons and subjected to positive bending. Experimental tests were carried out on beams with straight and draped tendons as well as on a non-prestressed beam. Six simply supported beams subjected to a positive static bending moment were tested up to failure. The influence of shear connection flexibility was taken into account and slip was measured along the beam axis. Concurrently, push-out specimens were made and tested to determine shear force vs. slip curves. It was found that at the same eccentricity of tendons (draped or straight without saddle points) the tendon shape has no significant effect on the behavior and ultimate resistance of composite steel-concrete beams. It is also shown that steel-concrete bond cohesion can significantly influence the behavior of the shear connection in composite beams. This influence is comparable with the design shear resistance of a single stud connector.     

深圳北站组合梁抗弯承载力及稳定性分析

组合梁抗弯承载力和稳定性分析对组合梁的结构设计很关键,但组合钢梁上翼缘受混凝土楼板约束,其稳定性分析应与我国现行规范规定的自由梁弯扭失稳不同,我国《钢结构设计规范》GB50017—2003采用限制绕弱轴的长细比的方法,未能考虑楼板作用,不适用于组合钢梁稳定性分析。此外,在连续组合梁的负弯矩区,局部稳定性问题也要考虑。结合深圳北站站房楼盖组合梁的工程实例,采用GB50017—2003和欧洲规范EC4,对组合梁抗弯承载力和稳定性进行计算分析,同时,利用通用有限元程序SAP2000对组合钢梁进行弹性屈曲分析,进一步确保了结构的安全。