Testing of composite steel top-and-seat-and-web angle joints at ambient and elevated temperatures: Part 2 — Elevated-temperature tests

An experimental programme of eight elevated-temperature tests on composite steel top-and-seat-and-web (TSW) angle joints was carried out to investigate the behaviour of this form of joints under fire conditions. It is found that the inherent strength and stiffness of composite joints can significantly improve the structural behaviour of steel framed structures under fire conditions. However, experimental works on composite steel TSW angle joints under fire conditions have not been published yet. To develop a versatile model to predict the joint moment-rotation characteristics, the authors have developed a component-based mechanical model for this form of joints. The objectives of this study are to ascertain the moment-rotation characteristic for this form of joint at elevated temperatures and to validate the authors’ mechanical model. The effects of some parameters on the overall joint behaviour, such as elevated temperatures, longitudinal shear strength of RC slabs, steel beam depth and bolt behaviour were observed and investigated. The mechanical model predictions are compared with the test results and showed good agreement.     

Review on the modelling of joint behaviour in steel frames

Steel portal frames were traditionally designed assuming that beam-to-column joints are ideally pinned or fully rigid. This simplifies the analysis and structural design processes, but at the expense of not obtaining a detailed understanding of the behaviour of the joints, which in reality, have finite stiffness and are therefore semi-rigid. The last century saw the evolution of analysis methods of semi-rigid joints, from the slope-deflection equation and moment distribution methods, to matrix stiffness methods and, at present, to iterative methods coupling the global and joint structural analyses. Studies agree that in frame analysis, joint rotational behaviour should be considered. This is usually done by using the moment-rotation curve. Models such as analytical, empirical, experimental, informational, mechanical and numerical can be used to determine joint mechanical behaviour. The most popular is the mechanical model, with several variances (e.g. Component Method). A summary is given of the advantages and disadvantages and principal characteristics of each model. Joint behaviour must be modelled when analysing semi-rigid frames, which is associated with a mathematical model of the moment-rotation curve. Depending on the type of structural analysis required, any moment-rotation curve representation can be used; these include linear, bilinear, multilinear and nonlinear representations. The most accurate representation uses continuous nonlinear functions, although the multilinear representation is commonly used for mechanical models. This article reviews three areas of steel joint research: (1) analysis methods of semi-rigid joints; (2) prediction methods for the mechanical behaviour of joints; (3) mathematical representations of the moment-rotation curve.     

地铁盾构隧道纵向接缝承载能力试验研究与解析分析

当前地铁运营实践和研究表明管片接缝是盾构隧道衬砌结构的薄弱环节,接缝的受力性能直接决定了隧道结构的承载能力。依托于整环试验研究结论,以盾构隧道管片纵缝接缝为研究对象,对不同运营工况下管片接缝的承载性能进行了足尺试验研究,获得不同工况下构件挠度、接缝转角等变化规律,得到转角刚度。分析得到了纵缝接缝的破坏链条,推导了可模拟接缝受力全过程的解析模型分析了纵缝接缝的全过程受力性能及其极限承载力。并借此模型对接缝截面与全截面受力变形进行对比分析,通过试验数据与解析模型数据的对比分析验证解析模型的合理性。     

Stiffened aluminium panels subjected to axial compression

This paper presents axial compression tests on longitudinally stiffened aluminium panels in alloy AA6082 temper T6. A specially designed test facility is presented. The panels are built up with extruded aluminium profiles connected by longitudinal welds. Two panel types are considered, with open section (L-shaped) stiffeners and closed section stiffeners, respectively. The experimental programme comprises tests on single panels supported along all four edges and as a special case panels supported at two edges only. Tests on panels with lengths 1.0 m and 2.0 m are reported. Two deformation modes were observed in the tests; regular flexural buckling of the entire panel towards either the stiffener side or the plating side, and, for the case of the panels with L-shaped stiffeners, collapse initiated by stiffener tripping. The panel resistance is compared with the design resistance obtained from the European standard for aluminium structures, Eurocode 9. For all panels the experimental capacity exceeded the design value.     

古建筑木结构透榫节点力学模型研究

为研究古建筑木结构透榫节点的M-θ力学模型，在分析透榫节点构造特征与受力机理的基础上，建立其数值模型，用透榫节点的试验数据验证了该数值模型的正确性，并分析了节点缝隙、木材横纹弹性模量和大榫头长度对透榫节点受弯承载力的影响。根据受力分析结果，建立以弹性点、屈服点与极限点为特征点的三折线多参数M-θ力学模型，其结果与多数的试验结果基本吻合，并将该力学模型应用于木构架的受力分析。研究结果表明：透榫节点的滞回耗能能力强，节点的变形主要集中在榫头处。当榫头与卯口之间的缝隙增大时，节点的受弯承载力降低。随木材横纹弹性模量的提高和大榫头长度的增加，节点的受弯承载力有一定提高。文章建立的M-θ力学模型能较好反映透榫节点的受力过程，适用于木构架的受力分析，其荷载 位移骨架曲线与试验结果基本吻合。研究成果可为古建筑木结构的维修与保护提供参考。     

50 Jahre Aluminiumbrücke über den Datteln‐Hamm‐Kanal

50th birthday of the aluminium road bridge across the Datteln‐Hamm‐Kanal in Germany. Germany's first aluminium road bridge, the Schwansbell Bridge spanning the Datteln–Hamm Canal near Lünen, was opened to traffic in 1956. The design is a trussed structure made from extruded profiles and sheets using AlMgSi 1 alloy (today's equivalent would be EN AW‐6082). The bridge has a span of 44.2 metres; it has a dead weight of 25 t and vehicles weighing up to 12 t are allowed to use it. The design of a comparable steel bridge had a dead weight of 60 t. Thus, the use of aluminium led to a weight saving of 58%. Aluminium rivets, also made from AlMgSi1, were used almost exclusively for the joints. The shape of the rivets had previously been tested and optimised in a series of tests. A decision was made before the bridge was built to forego the use of any additional coating in order to evaluate the corrosion resistance of the aluminium. To this day, there has not been any need for either additional corrosion protection to be applied to the aluminium structure of the bridge or for any maintenance work to be carried out on the bridge because of corrosion. Routine inspections of the bridge confirm that it is in an excellent condition. This is all the more remarkable as the construction is located in the Ruhr area and has been exposed to an industrial atmosphere for 50 years. Savings in the cost of corrosion protection as well as for the work needed to maintain such protection have been made during the bridge's entire service life.     

纵向焊接铝合金压杆承载力研究

大多数结构用铝合金通常要经过热处理或加工硬化以改善其力学性能。当这种合金焊接后除了产生残余应力外,在焊缝附近还将产生强度明显降低的热影响区(HAZ)。而对于钢结构,由于其热导率比铝材小得多,因此只有高强钢才可能产生强度降低的热影响区,而且其强度的降低没有铝合金显著,热影响区的宽度也比铝合金小得多。这将使得铝合金受压杆件的屈曲性能变得更为复杂。对贴角焊和剖口焊这两种焊接方式的工字型铝合金中心受压杆件进行试验研究,并将试验结果同即将颁布的国标《铝合金结构设计规范》(送审稿)及欧洲规范9(EC9)进行比较。结果表明,通常情况下,对于贴角焊构件,规范结果与试验结果吻合较好;而对于剖口焊构件,规范结果偏保守。     

盾构管片接头转动刚度的理论与实验分析

在地铁区间盾构隧道的衬砌环结构的设计中,管片间接头处往往是结构的薄弱部位。本文在已有接头计算模型的基础上,引入简化假设,推导出了管片环向接头的力学模型,该模型考虑了混凝土的接触压力、螺栓的预紧力以及针对密封垫的修正。利用该模型可以得到接缝转角、张开量、螺栓拉力和接头转动刚度等内力和变形信息。为了验证模型的准确性,针对上海地铁区间隧道管片纵向接头进行了1∶1足尺加载试验,将试验的量测结果与理论模型的计算结果进行了对比。结果表明,计算模型可以很好反映接头的受力和变形情况。     

Experimental study on semi-rigid composite joints with steel beams and precast hollowcore slabs

The concept of semi-rigid composite connection has been widely researched in the past; however, most of the researches are limited to composite joints with metal deck flooring and solid concrete slabs. Composite construction incorporating precast concrete hollowcore slabs (HCU) is a recently developed composite floor system for buildings. The research on the structural behaviour of the semi-rigid composite joints with HCU is new and without any previous experimental database. In this paper, eight full-scale tests of beam-to-column semi-rigid composite joints with steel beams and precast hollowcore slabs are reported. The variables are stud spacing, degree of the shear connections, area of the longitudinal reinforcement and slab thickness. The test set-up and instrumentation is described in detail. The experimental behaviour is analysed and based on the test data the structural behaviour of these semi-rigid composite joints is discussed. Based on the experimental data, a simplified method to predict rotation and moment capacity for this type of composite connection is proposed.     

错位交汇型钢管焊接节点试验研究

厦门火车西站站台雨棚钢结构节点为钢管焊接的空间管桁节点,其中存在一种杆件错位交汇的特殊节点形式.由于此种节点并非所有杆件交汇于同一点,杆件错位交汇使得节点受到较大偏心力的影响,加上节点杆件较多,受力状态较为复杂.为确保其安全性,选择其中典型的KT-KTT型节点进行足尺试验研究和弹塑性有限元分析.试验结果表明,节点承载力...     

Numerical and analytical investigations of steel beam-to-column joints at elevated temperatures

Several furnace tests on the behavior of steel beam-to-column end-plate joints at high temperatures have been reported in a previous paper. This paper presents a series of corresponding analytical and numerical investigations to study the behavior of these steel joints, in some cases taking account of the influence of thermal restraint. A “component-based” methodology has been utilized to analyze the mechanical response of steel end-plate joints at elevated temperatures, incorporating the beam web shear component together with those within the tension and compression zones of the connection. Effects from thermal restraints on steel joints have also been integrated into this approach. This analytical model was found to represent well the structural behavior in the tests, including the effects of thermal restraint. In order to set these results into their proper context, detailed finite element simulations of the tests were also performed. Both the component-based and numerical predictions provide acceptable correlations with the test behavior.     

基于数码摄影技术的岩体裂隙测量方法初探

基于数码摄影技术的岩体裂隙测量法，是一种与传统测量完全不同的新方法，可以高效率地测量岩体裂隙。基于数字图像处理理论，针对裂隙图像的特点，对这一新方法进行了比较全面地探索，提出了裂隙图像的现场采集方法及其解译路线，重点研究了智能识别方法，并研发了相应的处理软件。按照上述解译路线，应用自编裂隙图像处理软件，对从野外实拍的典型数字裂隙图像进行了试算、分析和总结，初步证明了此解译路线的可行性。     

大型厂房钢筋混凝土框排架结构中异型节点的抗震性能和设计方法研究

针对大型厂房框排架结构中通常存在变梁变柱异型节点的实际情况,进行4个1/5比例异型中节点伪静力试验研究及含有该类节点整体结构的试验,分析大小梁相对刚度、大小核心面积及小核心与柱配箍率等因素对该类节点破坏模式的影响。研究结果表明:该类节点初裂荷载、极限荷载较常规节点显著降低,通裂阶段与极限阶段非常接近,易发生小核心剪切破坏和柱端剪切破坏等两种破坏模式。采用约束机理对小核心剪切破坏进行分析并提出承载力计算方法;对于柱端剪切破坏应采用限制大梁底部纵向钢筋的方法予以避免。提出采用大小梁端弯矩比为参数区分不同类型的破坏模式,为该类异型节点合理设计提供了依据。     

外包钢-混凝土组合梁与钢筋混凝土柱节点的试验研究

外包钢-混凝土组合梁是一种新型组合梁,在负弯矩作用下具有良好的工作性能,其与柱连接节点的构造还有待合理设计并试验验证。采用两种不同的构造形式,设计4个外包钢-混凝土组合梁与钢筋混凝土柱的连接节点,并对其进行低周反复荷载作用下的试验研究。对节点的破坏形态、滞回曲线、强度、延性和钢筋、钢板的应变等性能进行分析,结果表明:通过合理的构造措施,外包钢-混凝土组合梁与钢筋混凝土柱的连接节点具有较好的受剪承载力、延性和耗能能力,能够满足工程要求。在此基础上对节点的受力机理进行探讨,提出节点核心区受剪承载力的计算公式,计算结果和试验结果吻合良好。     

挤出形状/尺寸对3D打印混凝土力学性能的影响

为了揭示3D打印挤出形状和尺寸对成型混凝土性能的影响机制,对比了模具成型、同挤出流量条件下不同挤出形状（三角形、方形和圆形）成型、同挤出形状条件下不同挤出尺寸成型、同挤出形状和同尺寸下不同打印条排列成型的混凝土断面形态、力学性能和空间孔隙分布,分析了不同挤出形状和尺寸条件下打印试件的层/条缺陷特征,探讨了打印试件孔隙率与其力学性能的对应关系.结果表明：层间和条间缺陷会显著影响打印试件的密实度,在同挤出流量条件下,由于层/条间的压紧作用,挤出形状呈三角形的打印试件具有最少的层间缺陷和最佳的力学性能;同形状的打印试件随着挤出尺寸的增大,其缺陷降低、力学性能提高;在挤出形状和尺寸均不变的情况下,打印口交错排列可提升打印试件力学性能13%～47%.     

An experimental study on clinched joints realized with different dies

An experimental investigation has been conducted on mechanically clinched joints, produced with fixed and extensible dies with different forming forces. Mechanical testing involving single lap shear tests, both with one and two joining points, and peeling tests were conducted under quasi-static conditions to assess the different mechanical behaviors of these joints. The effect of the processing conditions on the main mechanical response of the joints, namely the maximum strength, stiffness and absorbed energy, was investigated.The results showed that the joints produced with the extensible die exhibited a similar strength as compared to those produced with the fixed die in single lap shear tests, while they are characterized by a higher strength (up to 40%) when loaded during the peeling test because of a larger interlock. In addition, the employment of extensible dies allows a drastic reduction of the forming loads as compared to those required by adopting the fixed dies.     

北京新机场装配式单层铝合金网壳结构整体稳定性能研究

以北京新机场装配式单层铝合金网壳结构作为研究对象,建立了其装配式节点——板式节点及考虑节点性能的单层铝合金网壳的有限元模型,分析了板式节点的力学性能及节点性能对单层铝合金网壳稳定性能的影响。研究表明：板式节点刚度良好,破坏表现为不锈钢拉铆钉剪切破坏、连接板拉剪破坏和杆件在螺栓孔处承压破坏;北京新机场装配式单层铝合金网壳结构的整体稳定性能良好,承载力约为刚接网壳结构的90%,满足JGJ 7—2010《空间网格结构技术规程》的要求;由于铝合金材料无明显的屈服台阶,弹性模量较小,考虑几何非线性和材料非线性的稳定承载力比仅考虑几何非线性的稳定承载力降低约30%,结构发生弹塑性失稳,结构失稳形态表现为网壳结构在靠近长轴右端出现凹陷。     

岩石模型结构面的取样代表性试验研究

岩石结构面的代表性取样是开展不同尺寸模型结构面直剪试验的前提条件,直接影响到结构面抗剪强度尺寸效应试验结果的有效性和可靠性。通过对取样尺寸为10 cm的18组岩石结构面粗糙度系数(JRC)的测量和统计分析,得到该尺寸岩石结构面试样的粗糙度系数分布规律,表明模型结构面取样代表性评价的必要性。基于结构面粗糙度系数非均一性分布特点,以及对简单随机取样法和分层取样法2种概率取样方法的比较分析,提出基于分层取样法的岩石模型结构面代表性取样方法,该方法采用JRC四分位法确定各层样本的数量比例,再利用分层取样公式计算样本的取样数量。通过岩体结构面抗剪强度的力学机制分析,对试样取样代表性和力学可靠性进行校验,结果表明,采用该取样方法能较好地代表该尺寸的表面形态分布,取样结果也较好地满足力学试验的统计精度要求。     

Numerical Modelling of the Influence of Joint Typologies on the 3D Behaviour of a Steel Sub-Frame Under a Natural Fire

In order to address the complex loading condition of steel joints in fire, and based on the experimental fire tests on steel frames with different joint typologies, performed at the University of Coimbra (Santiago et al. 2008), a detailed three-dimensional model was developed and calibrated to simulate the behaviour of welded and bolted end plate beam-to-column joints. The structural frame is modeled combining 3D shell, solid and joint elements, thereby taking into account the effect of the local failure modes, and the realistic behaviour of the frame exposed to a natural fire. The numerical model accounts for the initial geometrical imperfections, non-linear temperature gradient, geometrical and material nonlinearity and temperature dependent material properties. The results show the performance of each individual structural joint component under heating and cooling conditions and identify the main dependencies of the geometrical and mechanical variables of the components on the joint behaviour. The global behaviour of the frame and the joint failure modes are compared and discussed with the experimental observations.     

门式刚架含缺陷外伸式端板梁柱节点有限元分析与试验研究

对1个符合规范要求(无缺陷)和3个不符合规范要求(含缺陷)的门式刚架外伸式端板连接节点进行了承载力试验及相应的有限元分析,以了解实际工程中存在的含缺陷节点的力学性能,并对该类节点在正负弯矩作用下的性能进行了有限元分析。研究结果表明:在节点域屈曲起控制的节点中,节点域设置加劲肋对提高节点的承载力作用相当显著;相对于梁端板和柱翼缘同时加厚的无缺陷节点,含缺陷节点的极限承载力基本接近,但其弹性抗弯能力下降、初始转动刚度有所下降,其性能分析适合采用半刚性理论。所采用的有限元分析方法结果可靠,可为含缺陷节点的门式刚架结构的整体受力分析或后续加固提供依据。