水平荷载作用下半刚性连接组合梁框架承载能力极限状态验算方法

本文分析了半刚性连接组合梁框架的在水平荷载作用下的受力特性,提出了对于具有合理构造措施的半刚性连接框架,采用塑性分析方法进行在水平荷载作用下的框架整体极限承载能力、组合梁的承载能力及框架柱的承载能力验算。采用塑性分析方法可使设计计算工作量极大地降低,而且能给出较为安全和准确的分析结果,这可供半刚性连接框架的实际设计参考。     

水平荷载作用下足尺半刚性连接组合梁框架试验

为研究半刚性连接组合梁钢框架在水平荷载作用下的特性,进行水平荷载作用下足尺的空间两层两跨半刚性连接组合梁框架的试验研究。半刚性连接组合梁框架由热轧H型钢柱和焊接H钢梁及压型钢板混凝土组合梁组成,连接为平端板连接半刚性节点。试验主要进行相应测点的应变、转角及位移测量,框架整体性能及半刚性连接节点性能的分析。试验结果显示半刚性连接组合梁框架具有较强的抵抗水平荷载的能力;平端板连接组合节点为半刚性连接、部分强度节点,具有较高的强度、刚度和较好的延性。将试验结果与简化计算方法的预测结果进行比较,结果显示框架的总体位移、极限承载能力、节点转动能力及强度的试验值与简化方法的预测值能较好的吻合。     

梁柱连接组合节点弯矩-转角关系研究

梁柱连接组合节点传递着梁柱之间的弯矩和剪力,是钢框架中的重要组成部分,也是钢框架设计中的关键部位之一。弯矩-转角关系是梁柱连接组合节点的主要力学性能,它反映着节点的初始刚度、抗弯承载力和转动能力,直接影响着钢框架体系的变形、极限承载力与整体性能。梁柱连接组合节点连接方式多样、构造形式种类繁多、几何参数多变、各组件受力状态与性能复杂等特性决定了弯矩-转角曲线是非线性的。而弯矩-转角曲线的非线性造成其难以拟合和预测。目前,半刚性连接组合节点的试验与理论研究有了较大的进展。本文归纳和总结了国内外梁柱半刚性连接组合节点弯矩-转角关系研究,包括试验研究和理论模型,并指出了今后需要进一步研究的重点与方向。     

竖向荷载下足尺半刚性连接组合框架试验研究

为研究半刚性连接组合框架在静载作用下的力学性能,进行了竖向荷载下两榀足尺的两层两跨半刚性连接组合框架试验。组合框架由H型钢柱和压型钢板混凝土组合梁组成,钢节点由焊接到钢梁端部的平端板通过螺栓与钢柱翼缘连接。为了解半刚性连接组合框架的结构性能和破坏特征,考察不同荷载水平作用下半刚性连接和楼板的组合效应对钢框架结构整体性能的影响,重点分析框架整体性能、节点性能和梁性能。试验表明:平端板型组合节点为半刚性连接、部分强度节点,具有较高的强度和刚度,其极限转角可满足不小于30mrad的延性设计要求;半刚性连接和楼板的组合效应对钢框架的强度、刚度和延性有较大影响,设计时应加以考虑。试验结果可为今后半刚性连接组合框架理论研究和工程实际应用提供参考。     

竖向荷载下梁柱连接的刚性判别准则

框架结构中梁柱的连接往往是半刚性的,设计中把梁柱连接假定为完全刚接或完全铰接都是不合理的。在对半刚性框架和刚性框架受力变形分析的基础上,综合框架正常使用极限状态和承载能力极限状态两种状态,建立了竖向荷载作用下梁柱连接刚性判别准则。     

钢-混凝土组合框架梁的稳定设计方法

在已有的钢-混凝土组合梁和钢框架理论研究基础上,分析了影响组合梁负弯矩区转动能力的主要因素,建立了组合梁连续和钢柱连续两种组合框架结构体系的节点塑性极限转角的求解方法,提出了相应的计算公式及一种简化的组合框架梁稳定设计方法,并得出了组合梁负弯矩极限调幅系数的计算方法.结果表明,该设计方法可以使组合框架塑性铰处的内力充分重分布,使梁柱连接的转动刚度合理,也能使组合梁的设计达到充分利用组合效应及节点延性的目的.     

半刚性连接梁柱组合节点低周反复荷载试验研究

为研究半刚性连接梁柱组合节点的抗震性能,开展了1个纯钢框架梁柱中节点、2个组合框架梁柱中节点的低周反复荷载试验。梁柱采用平齐式高强螺栓端板连接,试验采用柱顶加载模式。对试件的试验现象、变形、应变和耗能能力等进行了分析和比较。试验结果表明,组合节点相对于纯钢节点而言,由于负弯矩作用下钢筋的抗拉作用和正弯矩作用下混凝土板的抗压作用,其受弯承载力和转动刚度均有较大程度地提高;连接弯矩-转角关系的滞回曲线饱满、稳定,具有良好的耗能能力;平端板连接梁柱组合节点在反复荷载作用下具有较高的承载力和良好的延性,抗震性能良好。     

半刚性连接钢框架基于极限状态的抗震设计

简述了CECS 260∶2009《端板式半刚性连接钢结构技术规程》中关于半刚性连接钢框架在水平地震作用下的设计流程,其主要以结构处于极限状态下承载力验算为主,为了更好地使验算内容与极限状态相适应,基于塑性设计的研究成果,提出改进的半刚性连接钢框架抗震设计方法:基于极限状态的抗震设计方法。通过提出的侧移承载力修正系数计算结构极限状态下的基底剪力,确定结构极限状态下地震作用沿层高的分布,最后对半刚性连接节点以及梁柱进行设计。采用此方法对1榀6层半刚性连接钢框架结构进行设计,然后采用动力时程分析方法验证了该方法的可行性。     

负弯矩作用下钢管混凝土组合框架端板连接节点的抗弯承载力计算方法

为了获悉负弯矩作用下钢管混凝土组合框架端板连接节点的抗弯承载力,给出组合节点的失效模式,建立对称荷载和非对称荷载作用下组合节点的力学模型,详细考虑柱截面类型、端板类型、荷载类型、楼板组合作用的影响。基于节点失效模式,分别提出钢筋抗拉承载力、螺栓抗拉承载力、连接抗压承载力等组件承载力的简化计算方法。根据力学平衡原理和力学模型,利用组件法,确定组合节点受弯中和轴位置,分别提出平齐端板连接和外伸端板连接钢管混凝土组合节点在负弯矩作用下的承载力计算公式。用试验结果验证了所提组合节点抗弯承载力简化计算方法的正确性,研究成果可为建立半刚性钢管混凝土组合框架设计理论提供科学依据。     

竖向荷载下半刚性连接组合框架的实用设计方法(Ⅱ)——梁与柱设计及算例

虽然在钢框架结构设计中考虑半刚性连接和楼板的组合效应会产生良好的结构经济性,但是在实际工程中仍很难应用,主要原因是缺乏合适简便的设计方法。本文在国内外研究的基础上,结合我国钢结构设计规范GB50017-2003,给出了竖向荷载下半刚性连接组合框架的实用设计建议方法。设计建议方法包括满足两个极限状态的节点、梁、柱设计,较好地解决了梁挠度和柱有效长度系数计算中节点连接刚度的合理选取、半刚性特征对梁挠度和柱计算长度的影响。该方法不仅反映了节点和框架的实际性能,而且简便实用,符合工程师对普通钢框架的设计习惯。本文为全文的第二部分,介绍梁与柱设计。并通过一个算例,说明竖向荷载下半刚性连接组合框架的实用设计过程及经济性。     

竖直荷载作用下半刚性组合结构的实用设计方法

尽管半刚性连接和楼板组合效应在钢框架设计中的优点已被广泛证实，但在实践工程中却较少采用，首要原因是缺乏合适的实用设计方法。在此提出了一种针对竖直荷载作用下半刚性组合结构的实用设计方法。该方法可以用于正常使用极限状态下半刚性组合结构的连接、梁柱的设计。同时也确定了用于计算梁挠度的梁柱连接的转动刚度以及柱的有效长度系数。     

竖向荷载下半刚性连接组合框架的实用设计方法(Ⅰ)——梁柱节点设计

虽然在钢框架结构设计中考虑半刚性连接和楼板的组合效应会产生良好的结构经济性,但是在实际工程中仍很难应用,主要原因是缺乏合适简便的设计方法。本文在国内外研究的基础上,结合我国钢结构设计规范GB50017-2003,给出了竖向荷载下半刚性连接组合框架的实用设计建议方法。设计建议方法包括满足两个极限状态的节点、梁、柱设计,较好地解决了梁挠度和柱有效长度系数计算中节点连接刚度的合理选取、半刚性特征对梁挠度和柱计算长度的影响。该方法不仅反映了节点和框架的实际性能,而且简便实用,符合工程师对普通钢框架的设计习惯。本文为全文的第一部分,介绍了梁柱节点设计。     

A practical design method for semi-rigid composite frames under vertical loads

Although the benefits of semi-rigid connections and composite actions of slabs are extensively documented in the design of steel frames, they are not widely used in practice. The primary cause is the lack of appropriate practical design methods. In this paper, a practical method suitable for the design of semi-rigid composite frames under vertical loads is proposed. The proposed method provides the design of the connections, beams and columns for semi-rigid composite frames at the ultimate and serviceability limit states. The rotational stiffness of beam-to-column connections for calculating the deflection of the frame beams and the effective length factor of columns are also determined. In addition, the accuracy of the proposed design method is verified by a pair of tests carried out on full-scale semi-rigid composite frames. Moreover, a design example is proposed to demonstrate the application of the proposed design method. It is shown that the proposed design method not only takes into account the actual behavior of the beam-to-column connections and its influence on the behavior of the overall structures, but is also simple and convenient for a designer to use in engineering practice.     

Required and available moment redistribution of continuous steel-concrete composite beams

Based on the ultimate limit state analysis, the required moment redistribution to enable full plastic mechanism for continuous composite beams is derived. The composite beams studied are continuous over the internal support and with a uniform section along the beams which are one of the conventional steel structural forms in Chinese construction practice for buildings and medium span bridges. It is illustrated that the required moment redistribution for the beam increases as the ratio of negative to positive moment resistance reduces, but decreases as the span difference, or the difference of load in the two spans increases. A method to assess the available moment redistribution based on the rotation capacity at the notional plastic hinges of a composite beam is developed. The potential moment redistribution in a continuous composite beam is also assessed when the available rotation capacity at the notional hinge fails to satisfy the required capacity capable of a plastic design. For a continuous composite beam to develop full plastic design, the available moment redistribution for the beam should be greater than or at least equal to the moment redistribution required, hence the full moment redistribution from the hogging region to the sagging region in the beam is capable. The derived available moment redistributions agree with the test results and computer simulations, but in a general lower bound of the strength capacity. An example is given and the results are compared with that based on the moment redistribution proposed in the present Chinese design code for steel-concrete composite beams. The present study provide a design approach to assess the load carrying capacity for a continuous composite beam based on the available moment redistribution capable depending on the rotation capacity or the force ratio etc rather than a fixed value of moment redistribution proposed, so that in most cases, an economic design is capable.     

The effects of partial shear connection in composite flush end plate joints Part I — experimental study

The experimental results of partial shear connection composite beams subjected to hogging bending have been previously reported. An extension to this work which considers the presence of a semi-rigid, partial strength connection is described herein. Five sub-assemblages of cruciform composite joints that simulate the internal region of a semi-continuous frame were tested. The joints were constructed using a novel approach of blind bolting a flush end plate to concrete-filled square hollow columns. Apart from the level of shear connection, the other parameter varied was the reinforcement area. In addition, a bare steel joint was also tested to act as comparison specimen. Based on the experimental results, the intrinsic behaviour of the joints in terms of strength, stiffness and ductility was assessed. It was further affirmed that by lowering the levels of shear connection, the rotation capacity of the composite joints was enhanced with only a slight compromise if the stiffness and moment resistance. A notable effect on the connection behaviour was also observed by varying the reinforcement levels. The outcomes clearly affirmed the benefits of partial shear connection in contributing the additional flexibility to increase the joint ductility, which is extremely advantageous for plastic design purposes. In view of this, the current restriction of providing full shear connection design within hogging moment regions of continuous and semi-continuous structures could be relaxed.     

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.     

Design of semi-continuous composite steel-concrete beams at the fire limit state

A two-dimensional temperature analysis procedure based on the finite element method (FEM) is described and applied to steel-concrete composite beams. A computer program developed for the analysis is detailed. A strategy is also proposed for incorporating the influence of the partial resistance of the composite connections in reducing the sagging moment at central regions of the beam spans when the beam is calculated as semi-continuous. Finally, an example problem is discussed, comparing the design uniformly distributed loads that can be supported by a composite beam calculated as semi-continuous and with simply supported spans. The temperature distribution due to fire at the central region of the spans is taken as in the simplified procedure proposed in European Prestandard ENV 1994-1-2 [ENV 1994-1-2. Eurocode 4, Design of composite steel and concrete structures — Structural fire design. Brussels: European Committee for Standardization (CEN); 1994] and then obtained with the more rigorous calculation using the described numerical algorithm. It will be assumed that no ultimate limit state will occur due to shear force (web buckling) or due to bending moment at the hogging moment regions of the beam (web and bottom flange buckling or distortional lateral buckling).