Moment resistance statistical distribution of beam-to-column composite joints

In seismic design of steel–concrete composite moment resisting frames, the randomness of beam-to-column joint rotational response can affect the location of dissipative zones. In fact, in case of full-strength joints, the dissipation of the earthquake input energy occurs at the beam ends; conversely, in case of partial-strength joints, the connection components of beam-to-column joints are involved. Within this framework, random material variability of joint components plays an important role, because it affects the joint flexural strength and, as a consequence, also the plastic rotation supply. Therefore, within the framework of a research program aimed at the evaluation of the seismic reliability of steel–concrete composite frames including random material variability, this paper focuses the attention on the analysis of the influence of random material variability on the rotational response of beam-to-column joints. In particular, the aim of the work is the evaluation, by means of Monte Carlo simulations, of the statistical distribution laws of the parameters describing, from the overall point of view, the rotational behaviour of beam-to-column joints. Such distribution laws represent important input data for a complete probabilistic seismic demand analysis of steel–concrete composite moment-resisting frames where the joint modelling is performed by using rotational spring elements whose parameters are selected as random values satisfying the distribution laws previously derived.     

梁柱组合节点受弯承载力统计分布

在钢-混凝土组合抗弯框架的抗震设计中,梁柱组合节点转动响应的随机性会影响能量耗散区域的位置。事实上,在节点的强度作用全部发挥的情况下,地震能量的耗散发生在梁端,相反地,在节点的强度作用部分发挥的情况下,则耗散也会发生在梁柱连接节点的连接部件上。在结构框架中,节点构件的材料随机性变化扮演了重要的角色,因为它影响了节点的弯曲强度,从而也影响了其塑性转角。因此,框架的研究项目旨在评估包括材料随机变化在内的钢-混凝土组合框架的地震可靠性,并着重分析了材料随机变化对梁柱节点转动响应的影响。特别是通过蒙特卡罗模拟法从整体来对梁柱节点转动性能描述参数的统计分布法则进行评估。这种分布法则提出了关于钢-混凝土组合抗弯框架的一个完整的概率地震需求分析的重要输入数据,而其节点建模所使用的转动弹簧的随机值参数也满足之前推断出的分布法则。     

Structural assessment of minor axis steel joints using photoelasticity and finite elements

Traditionally, the steel portal frame design assumes that beam-to-column joints are rigid or pinned. However, it is largely recognized that the great majority of joints do not exhibit such idealized behaviour transmitting bending moments with non-negligible rotations. These joints are called semi-rigid and their design should be performed according to their actual structural behaviour. When minor axis beam-to-column joints are considered, the adopted design process generally assumes a flexible response although this is not true for the great majority of structural joints. Minor axis joints present a distinct behaviour that differentiates them from major axis joints. In fact, the absence of transverse stiffeners implies that the column web must resist all the tensile and compressive forces arising from the beam flanges in bending, akin to a plate supported on its vertical sides. In order to evaluate this component’s behaviour, this paper presents a comparison between results obtained from a finite element model analysis and experiments. The experimental programme was based on the use of reflection photoelasticity techniques to determine the column web stress and strain distribution present in minor axis semi-rigid joints. This technique, although widely used for determining stress and strain distributions in other applications, was first used in this investigation to determine the semi-rigid joints structural response.     

Analysis and behaviour of steel storage pallet racks

For steel storage pallet racks, lateral stiffness in down-aisle direction is usually provided by beam-to-column joints and base-plate connections, owing to the impracticability of using bracing systems in selected areas of pallet racks. Because of the high slenderness of members, second order effects influence remarkably the frame performance. The model of unbraced semi-continuous frame is hence adopted for design.

This paper presents the main results of a numerical study on the response of pallet racks commonly used in Europe. The influence of beam-to-column joint modelling on the overall frame response is singled out with reference to both service condition and ultimate limit states. The effect of an accurate definition of frame imperfections is considered. Finally, the influence of base-plate joints on the overall stability of the rack systems is discussed focussing attention on both stiffness and strength of the column bases.     

Post-earthquake fire and seismic performance of welded steel-concrete composite beam-to-column joints

The performance of steel-concrete composite full strength joints endowed with concrete filled tubes, designed with a multi-objective methodology dealing with seismic actions followed by fire is presented in this paper. In detail, instead of a traditional single-objective design where fire safety and seismic safety are independently achieved and the sequence of seismic and fire loading are not taken into account, the proposed design approach guarantees: (i) both seismic safety and fire safety with regard to accidental actions; (ii) fire safety for at least 15 min fire exposure on a joint characterised by stiffness deterioration and strength degradation due to seismic loading.In order to achieve the multi-objective design, full strength beam-to-composite tubular column joints were designed by means of the component method of Eurocode 4 Part 1-1 and Eurocode 3 Part 1-8, while Eurocode 4 Part 1-2 was considered for fire design. Moreover, to face a seismic-induced fire, they were enhanced with specific joint components which will be detailed.Both the experimental programme and the results provided by seismic tests, pre-damaged tests and fire tests carried out on beam-to-column joints are presented and discussed. The results demonstrate their adequacy in terms of design and performance. Moreover, non-linear numerical simulations clearly show that these joints can be deemed adequate for moment resisting frames of medium ductility class characterised by a behaviour factor of about 4.     

不锈钢端板连接梁柱节点静力承载性能试验研究

为了研究不锈钢端板连接梁柱节点的静力承载性能,对5个不锈钢端板连接梁柱节点和1个普通钢端板连接梁柱节点开展单调静力加载试验,得到了节点试件的弯矩-转角曲线,对比分析了钢材牌号、节点类型和端板有无加劲肋等因素对节点承载性能的影响。结果表明：相同尺寸和构造的不锈钢节点延性优于普通钢节点的延性;不锈钢中柱节点和边柱节点的承载力相差较小,但前者的初始转动刚度较高而后者的变形更大;端板加劲肋的设置显著提高了节点的承载性能。基于得到的试验结果,对中国GB 51022—2015、美国ANSI/AISC 358-16和欧洲EN 1993-1-8中的端板连接节点承载性能计算方法进行评估,3种计算方法均低估了不锈钢端板连接梁柱节点的承载性能。     

钢框架节点性能模拟综述

在钢结构门式刚架设计中,通常采用节点理想铰接或刚接的简化分析方法。但实际上梁柱节点具有一定刚度(即半刚性),这种简化方法不能反映节点的实际性能。20世纪开始逐渐出现了半刚性节点的分析方法,从最初的转角-位移方程和力矩分配法到刚度矩阵法,直至现在的融合整体和节点结构分析的迭代法。研究表明,框架分析中应该考虑节点转动性能,通常采用弯矩-转角曲线来描述。为确定节点的力学性能,可采用分析模型、经验模型、试验模型、力学模型、数值模型等,其中力学模型应用最普遍。介绍了各模型的优、缺点及主要特征。分析半刚性连接框架时必须模拟节点性能,这就与弯矩-转角性能的数值模型有关。基于分析模型,可输入弯矩-转角特性,包括:线性、双线性、多线性和非线性特性。虽然在力学模型中多采用多线性特性,但最准确的还是连续非线性特性。综述了钢节点研究的3个方面:1)半刚性节点分析方法;2)节点力学性能分析方法;3)弯矩-转角数值分析方法。     

Seismic behaviour of beam-to-column partial-strength joints for steel-concrete composite frames

The paper presents a large experimental campaign carried out on ten steel-concrete composite beam-to-column sub-assemblages employing monotonic and cyclic loading test protocols. Structural members (beams, columns and slabs) were defined through the design of a full-scale 3D prototype frame subjected to PSD testing campaign; main design hypothesis was to dissipate seismic energy in the joints designed as partial-strength. Testing programme on beam-to-column sub-assemblages was executed in order to assess seismic performance varying structural details at beam-to-column connection level and material qualities. Different mechanical connecting systems between concrete slab and column, two end-plate configurations, weak and strong column web panel, two steel qualities and different concrete strengths.The analysis of sub-assemblages performance was realized in two steps: a first step in which the joints behaviour was assessed, characterizing response at local level (e.g. moment-rotation curves); a second step in which the response was assessed at global level (e.g. force-displacement curves). The structural behaviour (i.e. resistance, plastic deformation and stiffness) was evaluated at three stages-identified as initial, service and maximum load-in order to monitor the evolution of sub-assemblage response increasing solicitation level. Moreover, seismic behaviour of specimens-in terms of dissipated energy, ductility, over-strength and equivalent viscous damping-was also executed. Comparison between experimental results was made in order to identify those parameter suitable for improved and reliable seismic behaviour of steel-concrete composite partial-strength joints.     

设置悬臂梁段拼接耗能的钢框架抗震性能试验研究

为了检验设置悬臂梁段拼接的钢框架抗震性能,对3榀1/2缩尺的一层半单跨钢框架进行了低周往复加载试验,研究拼接节点对整个钢框架抗震性能影响.拼接处翼缘和腹板拼接板均采用8.8级高强度摩擦型螺栓连接,研究了3种钢梁拼接设计方法对结构抗震性能的影响,得到了钢框架的滞回曲线、骨架曲线、耗能能力、刚度退化、层间侧移角、拼接梁段竖...     

槽孔套管连接的冷弯薄壁檩条分析

在多跨檩条设计中,一般假设梁是连续的,以避免进行节点分析。当采用等强度和刚性连接时,该假设是合理的。常用的两种连接类型为:搭接连接和套管连接。套管连接的优点主要是在装配过程中节约了时间和费用。而对于大部分Z型截面,采用搭接连接方式时,可以准确地计算出搭接部分的长宽比。对部分加劲的Z型套管连接节点进行试验和数值分析,研究它们的结构性能和确定合理的刚度和强度。     

考虑配箍率影响的RC梁-柱节点抗剪强度尺寸效应律

由于经典的混凝土尺寸效应律难以准确描述破坏机制更为复杂的RC构件破坏的尺寸效应行为,且无法定量描述相关参数对RC构件尺寸效应的影响。为此,以核心区剪切破坏的RC梁-柱节点为研究对象,在已有试验研究的基础上,采用三维细观尺度数值模拟方法,对影响节点剪切破坏性能的配箍率进行分析,研究其对RC梁-柱节点核心区剪切破坏行为及抗剪强度尺寸效应的影响规律。结果表明：箍筋一方面提高了梁-柱节点的名义抗剪强度,另一方面增强了节点的变形能力,减弱节点剪切破坏的脆性破坏程度,进而削弱节点抗剪强度的尺寸效应。结合配箍率的影响机制与规律,在无腹筋梁抗剪强度尺寸效应律的基础上,提出了能够定量考虑配箍率影响的用于梁-柱节点的尺寸效应半经验-半理论公式,模拟及试验结果证实了公式的合理性与准确性。     

Analysis of cold-formed purlins with slotted sleeve connections

In multi-span purlin design, it is customary to assume beam continuity, avoiding joint analysis. This analysis is safe when employing full strength and stiffness connection. There are two usual joint typologies: overlapping and sleeve connections. The main advantage of sleeve joints is reduction of cost and time in the assembly process. Overlapping joints can be correctly designed selecting the overlap length to depth ratio, for a wide range of Z-shaped profiles. In this paper, a partial strength and stiffness Z profile sleeve joint is experimentally and numerically analyzed, studying their structural behavior and characterizing their rotational stiffness and strength.     

端板型半刚性组合节点的有限元分析

利用有限元分析软件ANSYS对端板型半刚性组合节点进行了弹塑性有限元计算，分析了组合节点中混凝土板中的纵向钢筋总面积及钢筋强度对组合节点初始转动刚度、弹性极限弯矩和转角及塑性极限弯矩和转角的影响，从而为这种节点的设计提供了参考和借鉴。     

高层建筑混合结构钢梁与混凝土墙节点低周反复加载试验研究

为研究高层建筑混合结构钢梁与混凝土墙连接节点的性能,本文进行了3个足尺钢梁-混凝土墙节点试件试验研究。通过对钢梁施加恒定剪力与反复轴力,模拟重力与地震作用的影响,研究了解高层建筑混合结构钢梁与混凝土墙节点在地震作用下的破坏机理、破坏形态和极限承载力等特性。试验表明,按现行规范规定的锚固长度,可使节点的锚筋强度充分发挥,但反复荷载作用会使锚筋强度降低,而节点的承载力可按强度理论同时考虑重力引起的剪力和弯矩及地震引起的轴力确定。     

Seismic behavior of bolted beam-to-column connections for concrete filled steel tube

Concrete-filled steel tubes (CFT) have the advantage of high strength, high stiffness and being constructed quickly. However, because the behavior of the beam-to-column connection for CFT is complicated and its design has not been sufficiently verified, their use has been limited.In this paper, a new design of bolted beam-to-column connections for CFT is proposed. A mechanical model is established in order to derive theoretical equations for calculating the stiffness, the yielding shear strength and the ultimate shear strength of the panel zone. Also, a series of cyclic loading experiments have been conducted. The experimental results and theoretical results are very close, which demonstrates that the bolted connections have superior seismic resistance in stiffness, strength, ductility and energy dissipation mechanisms. From the laboratory studies, even though the story angular drift reaches 7% and the plastic angular displacement reaches 5%, the structure still stands. Those results indicate that the seismic resistance exceeds those specified in Taiwan and the US.     

Seismic behavior of reduced beam section joints considering concrete floor effect

This study investigates the seismic impact of concrete floors on reduced beam section beam-to-column joints through four quasi-static cyclic tests. We examine mechanical properties, failure modes, and processes against specific criteria. Additionally, we analyze hysteretic response, energy dissipation, stiffness, capacity, and stress–strain mechanisms. Moreover, the ABAQUS platform was used to reproduce the specimen nonlinear finite element model to compare and analyze the test results. The results showed that the specimens exhibit excellent energy dissipation capacity and ductility (with a coefficient of 5.00); the column-bar connection characteristics affect the maximum capacity and plastic hinge behavior in the reduced beam area. The reduced section of beam's upper flange could not improve the overall seismic performance of the joint. The observed failure sequence is as follows: concrete floor cracking, beam flange yielding, reinforcement fracture, lower flange yielding in the reduced beam area, and overall joint failure. This sequence confirms that the joint fulfills the design criteria of a “strong column-weak beam” by achieving the target of plastic hinge outward movement.     

Mechanical modeling of the nonlinear response of beam-to-column joints

A methodology for the estimation of the complete moment-rotation curve of structural beam-to-column joints is presented in this paper. The methodology is based on the component method and is materialized through appropriate mechanical models that are analyzed nonlinearly. The cases examined in this work include bolted connections with end-plates and with angles. Significant consideration is devoted to the reliable simulation of the tensile joint components that have the form of equivalent T-stubs, by application of a recently developed incremental T-stub model, for the calculation of their nonlinear force-displacement laws. The proposed methodology is evaluated against experimental tests and advanced finite element models in terms of stiffness, strength and rotational capacity, and its performance is found to be very satisfactory.     

型钢桁架K形节点的加固措施及试验研究

大连某工程在结构设计中采用了宽翼缘H型钢桁架结构,其中K形节点较多,在设计过程中,采用杆系程序计算时,强度和刚度能满足设计规范要求。目前涉及宽翼缘K形节点的资料较少,有限元分析结果表明,部分节点腹板强度不能满足设计要求,需要进行加固补强。为了验证节点加固补强措施的有效性,对宽翼缘H型钢K形节点进行了试验研究。通过试验,得到K形节点的工作机理、承载力、刚度及退化进程、延性、耗能能力和破坏特性等,为K形节点加固补强提供了设计依据。     

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.     

圆钢管空间相贯节点的实验研究

针对圆钢管空间相贯节点,进行了三种类型大尺寸足尺试件的试验。具体介绍了试件和加载方案的设计,提供了主要试验结果,并根据变形极限概念,提出了确定试件极限承载力的方法。对试件的破坏机理进行了分析,指出节点区焊缝刚度过大延性不足的特征,可能阻碍钢管节点管壁极限强度的充分发挥。根据试验结果,对空间相贯节点强度计算公式作了初步探讨。