焊接型钢-混凝土组合节点的震后耐火和抗震性能

介绍了采用多目标方法设计的型钢-混凝土全强度组合节点的性能,同时考虑抗震和耐火。传统的单目标设计方法没有考虑地震作用和耐火荷载次序,独立研究耐火安全和抗震安全。所建议的设计方法保证:1)偶然工况下的抗震安全和耐火安全;2)至少曝露在火灾下15min的节点的耐火安全,通过由地震作用引起的刚度和强度退化描述节点。为了达到多目标设计,根据欧洲规范3(1-8部分)及欧洲规范4(1-1部分)的组件法设计全强度梁-组合柱节点,根据欧洲规范4(1-2部分)进行耐火设计。为应对地震引起的火灾,通过特殊节点构造进行加强。介绍节点抗震试验、预损伤试验和耐火试验的过程和结果,并进行探讨。根据设计和性能,验证它们的可靠性。非线性数值模拟结果表明:对于性能因子为4的中等延性抗弯框架,这些节点是足够安全的。     

A Simple Method to Predict Temperatures in Steel Joints with Partial Intumescent Coating Fire Protection

Based on temperatures measured in steel joints with different extents of fire protection, this paper proposes a simple method to calculate temperatures in steel joints with partial intumescent coating fire protection. The method combines the simple temperature calculation methods in EN 1993-1-2 (Committee of European Normalisation CEN, Eurocode 3: design of steel structures—part 1-2: general rules—structural fire design, 2005) for unprotected and protected steel structures through the introduction of an exposure factor, which is the ratio of the unprotected surface area of the joint region to the total surface area of the joint area. Using the measured temperatures for fully protected steel joints, this paper first extracts the effective thermal conductivity of the intumescent coating used in the fire tests. Afterwards, this paper presents validation results based on fire test results on joints with partial fire protection. Finally, this paper presents methods to calculate the exposure factor for different types of partially fire protected steel joints.     

Experimental and analytical studies on the cyclic behavior of end-plate joints of composite structural elements

The subject of this paper is the analysis of end-plate joints under cyclic and monotonic loading conditions by experimental and analytical studies. The experimental programs are performed on bolted end-plate type joints of composite members under cyclic loading conditions with the purpose to study the seismic response of the considered connection type. The performed experimental research is the second and third steps of an international research project started in 1999 between the Budapest University of Technology and Economics (BME), Hungary and the Technical University of Lisbon (IST), Portugal. The monotonic behavior of the tested joints is followed by the Eurocode standard design method to evaluate the moment resistance and rotational stiffness of the joint. The comparison of the design and the experimental results are performed by the envelope moment-rotation relationships of the hysteretic curves and the design moment-rotation diagram. On the basis of the comparison the modification of the design model is proposed. The monotonic moment-rotation diagram is extended to large rotation regions with the purpose of covering the whole cyclic diagrams until the final failure of the specimen. A semi-empirical method is proposed to approximate the cyclic hysteretic behavior of the studied joints, based on the knowledge of the monotonic moment-rotation curve. This prediction method is based on all the available test results for each behavior mode type (6 tests on steel and 12 tests on composite specimens). The calculated hysteretic curve follows the cycles by polygonal lines taking into consideration the experimental observations. The proposed method establishes the absorbed energy of the consecutive cycles in the case of the studied joint arrangement using standard loading history. The proposed method is applied and verified in the case of each observed failure mode type. By these experimental and analytical investigations the favorable seismic behavior can be derived for the studied joint type.     

Eurocode 3, a basis for further development in joint design

This paper deals with the design aspects of joints based on Eurocode 3 and in particular on Part 1-8 “Design of Joints” and the possibilities for further developments. An overview is given of design philosophies named as “traditional” and “modern” design and the various design rules by which the structural behaviour in terms of stiffness, strength and deformation capacity can be predicted, with the aim of reducing the integral costs of steel structures.Emphasis is given on the need for reliable software tools to make the use of the Eurocode information easier for the designer. Possibilities for further development in joint design are discussed.     

Experimental testing of joints for seismic design of lightweight structures. Part 2: Bolted joints in straps

An experimental testing campaign on tensile bolted joints between straps is reported. Two dominant failure modes are identified: (1) tilting, bearing and tearing of the sheets (TS) and (2) tilting, bearing and net-section failure (NSF). The analysis in terms of ductility and strength shows that bolted connections are less adequate than screwed connections (reported in Part 1 of this paper) for the seismic design of X-braced shear walls in lightweight structures. NSF joints are more ductile than TS joints in the sense that they undergo larger displacements before failure. However, if washers are not used, both types of connections fail before energy dissipation through yielding of the diagonal straps can occur. Some design recommendations to improve the seismic performance of bolted joints, including the use of washers, are given. The accuracy of Eurocode 3 formulas to predict the ultimate load is also analyzed.     

Experimental analysis and modelling of bolted T-stubs under cyclic loads

Bolted connections have recently attracted new research efforts after the unexpected failures of welded connections during Northridge and Kobe earthquakes. The criteria and the formulations for predicting the rotational stiffness and the flexural resistance, under static loading conditions, of the most common connection typologies have been codified by Eurocode 3 [CEN. EN 1993-1-8 Eurocode 3: Design of steel structures — Part 1.8 Design of joints. 2005] which is based on the so-called component approach. In order to extend the component approach to the prediction of the seismic response of partial-strength connections, the modelling of the cyclic response of the joint components is necessary. Starting from the observation that the main sources of deformability and plastic deformation capacity of bolted connections can be modelled by means of an equivalent T-stub, an experimental program devoted to the cyclic response of the most important component of bolted connections has been carried out aiming at the modelling of the cyclic force-displacement curve of bolted T-stubs. In this paper, starting from the analysis of the results of the experimental tests performed, stiffness and strength degradation rules are derived as a function of the displacement amplitude required at any cycle and of the energy dissipated in the previous loading history. The combination of these rules with the theoretical prediction of the monotonic envelope leads to a proposal for predicting the cyclic behaviour of bolted T-stubs starting from the knowledge of their geometrical and mechanical properties.     

Axial strength of cold-formed thin-walled steel channels under non-uniform temperatures in fire

This paper presents the results of a numerical investigation into the axial strength of cold-formed thin-walled channel sections (columns) under non-uniform high temperatures in fire. The non-uniform temperature distributions are based on the results of a thermal analysis of thin-walled stud panels carried out by the authors. The general finite-element package ABAQUS is used to obtain strengths of columns with different lengths at different fire exposure times. To aid development of a hand calculation method of column strength in fire, the accuracy of using two ways of simplifying the non-uniform temperature distribution is investigated. The ambient temperature design method for cold-formed thin-walled columns in Eurocode 3 Part 1.3 (EN1993-1-3, Eurocode 3: design of steel structures, Part 1.3: general rules, supplementary rules for cold formed thin gauge members and sheeting, European Commission for Standardisation, Brussels, 2001) is modified to take into account the change in the strength and stiffness of steel at elevated temperatures and thermal-bowing effects. The results of this design method are compared to the ABAQUS simulation results.     

高强钢芯筒-螺栓连接钢管柱框架节点抗震性能试验研究

为解决现有单边螺栓容易拔出、钢管柱壁板撕裂等锚固不足问题,提出高强钢板-螺栓组合连接副,用于钢管柱框架节点.为研究该类节点的抗震性能和破坏模式,设计4个足尺比例的高强钢芯筒-螺栓连接钢管柱框架节点试件,变化参数为螺栓规格和钢梁端板厚度,分别进行单调加载静力试验和循环加载拟静力试验,考察节点破坏模式、转动能力、连接系数、...     

Plug and play type joints in steel and steel–concrete composite constructions: Development guide and design considerations

Traditionally, for countries in Western Europe, joints in steel frame structures are realised using bolts and welds. In the workshop, the components are made using welding end plates and attachments and drilling of the bolt holes. On site, these structural components are connected together using bolts and nuts. The activities on site mean a large physical effort of the steel construction workers who are not free from danger. Measures needed to ease the work and to make it safer for workers are increasingly expensive. There is a need to develop the so-called ‘plug and play’ connections which can be realised using remotely controlled techniques. The development of plug and play type joints is not only important to ease the work on site, but it can also reduce overall costs of the construction if the joint characteristics are taken into account at the design stage. Of the total costs of a steel structure, 50% of that amount is related to the joints whereas almost 90% of the total costs are already decided upon in the construction detailing phase. Optimisation in weight will not result in an optimal cost-efficient structure. Even semi-rigid and partial strength joints that result after the erection phase could lead to cost reduction. Some considerations are given to optimise the joint with respect to overall structural behaviour from a technical and economical point of view. Fast and safe construction methods with plug and play joints are required for the future. Structures need to be designed such that they are fit to be demounted and rebuilt easily. For these types of joints no specific design rules are available in Eurocode 3, Part 1.8: ‘Design of joints’ or in chapter 9 of Eurocode 4, Part 1.1: ‘Composite joints’. This article describes the basis of design for these joints.     

玻璃纤维片材加固混凝土梁柱节点的抗震性能研究

进行了 6个玻璃纤维 (GFRP)片材加固混凝土梁柱节点在低周反复荷载作用下的试验研究 ,结果表明GFRP片材加固节点是一个有效的加固方法 ,节点的抗剪强度和延性比加固前有较大的提高。基于试验结果提出了考虑混凝土、箍筋、GFRP片材共同作用的节点抗剪承载力计算方法。计算结果和试验数据基本吻合     

Towards a consistent design approach for steel joints under generalized loading

The behaviour of steel joints is complex and requires the proper consideration of a multitude of phenomena, ranging from material non-linearity (plasticity, strain-hardening), non-linear contact and slip, geometrical non-linearity (local instability) to residual stress conditions, and complicated geometrical configurations. The component method is widely accepted as the practical approach in predicting the behaviour of steel joints and it provides detailed procedures to evaluate the strength and initial stiffness of steel joints, as specified in Eurocode 3.Current safety concerns for steel structures require that steel joints are designed to perform adequately under a wider range of loading conditions: besides standard static loading conditions, fire and seismic loading must often be considered. In addition, robustness requirements impose that joints present a minimum level of resistance for any arbitrary loading. Predicting the 3-D behaviour of steel joints under arbitrary loading must thus be achieved in a practical way.This paper presents the results of a series of experimental developments that attempt to contribute to the knowledge of the 3D behaviour of steel joints, under static and dynamic conditions, and to discuss a possible framework for these general conditions that is in line with the principles of the component method.     

Vergleichende Betrachtung in der Entwicklung der Beulnachweise in den deutschen Normen

Compared view in the development of the buckling safety in the german rules. Eurocode 3 will be soon introduced in Germany. Part 1.5 deals with the buckling safety of plane plates without transverse loading with completely new safety design. This report deals with the differences between the still applicable design rule DIN 18800 Part 3 in comparison to the new Eurocode 3 Part 1.5 and DIN ‐Fachbericht 103 chapterIII respectively. These differences are shown by a calculation example performed at real bridge construction.     

Numerical modelling of load bearing light gauge steel frame wall systems exposed to realistic design fires

Fire safety has become an important part in structural design due to the ever increasing loss of properties and lives during fires. Conventionally the fire rating of load bearing wall systems made of Light gauge Steel Frames (LSF) is determined using fire tests based on the standard time–temperature curve in ISO834 (ISO 834-1, 1999 [1]). However, modern commercial and residential buildings make use of thermoplastic materials, which mean considerably high fuel loads. Hence a detailed fire research study into the fire performance of LSF walls was undertaken using realistic design fire curves developed based on Eurocode parametric (ENV 1991-1-2, 2002 [2]) and Barnett's BFD (Barnett, 2002 [3]) curves using both full scale fire tests and numerical studies. It included LSF walls without cavity insulation, and the recently developed externally insulated composite panel system. This paper presents the details of finite element models developed to simulate the full scale fire tests of LSF wall panels under realistic design fires. Finite element models of LSF walls exposed to realistic design fires were developed, and analysed under both transient and steady state fire conditions using the measured stud time–temperature curves. Transient state analyses were performed to simulate fire test conditions while steady state analyses were performed to obtain the load ratio versus time and failure temperature curves of LSF walls. Details of the developed finite element models and the results including the axial deformation and lateral deflection versus time curves, and the stud failure modes and times are presented in this paper. Comparison with fire test results demonstrate the ability of developed finite element models to predict the performance and fire resistance ratings of LSF walls under realistic design fires.     

论地震作用和钢框架板件宽厚比限值的对应关系(上)——我国规范与国际主流规范的地震作用比较

抗震钢框架梁柱截面的板件宽厚比,既是反映钢框架延性的关键指标,也是控制耗钢量的关键指标。框架梁柱截面的板件宽厚比选择,与地震作用下钢框架的受力状态紧密相关。对我国《建筑抗震设计规范》（GB50011-2001）与国际主流规范的设防标准进行比较,讨论我国抗震规范采用“小震”为基准的弹性设计方式,与国际主流规范以“中震”为基准,并按结构性能折减设计地震作用进行结构弹性设计方式之间的异同。进而,详细比较我国抗震规范与欧洲EC8、日本BCJ等国际主流抗震规范的地震作用计算和底部剪力。比较结果表明,我国抗震规范第一水准设防的地震作用FEk,与欧洲EC8规范性能因子q=4时及日本BCJ规范Ds=0.25时的设计地震作用水平比较接近。所分析内容,是合理借鉴国际主流规范,建立适合我国抗震规范体系的地震作用与框架梁柱截面板件宽厚比限值对应关系的基础。     

A design model for stainless steel box columns in fire

A study of stainless steel cold-rolled box columns at elevated temperatures is presented, which is a part of an on-going RFCS project “Stainless Steel in Fire”, 2004-2007. Experimental results of six, class 4, stub columns at elevated temperature, tested by Ala-Outinen [Members with Class 4 cross-sections in fire: Work package 3, ECSC project stainless steel in fire. Contract no. RFS-CR-04048, Espoo, Finland; 2005], were used to evaluate the finite element (FE) model. The FE analysis obtained using the commercially available software, ABAQUS, shows that the critical temperature was closely predicted. Further, a parametric study was performed using the same numerical model. This was a basis to check the quality of prediction of a newly proposed improvement for design rules of class 4 cross-sections in fire according to EN 1993-1-4 [Eurocode 3 - Design of steel structures — Part 1-4: General rules — Supplementary rules for stainless steels, CEN; 2006] and EN 1993-1-2 [Eurocode 3: Design of steel structures — Part 1.2: General rules — Structural fire design, CEN; 2005].     

钢筋砼空间框架节点抗震性能的研究

本文提供了12个钢筋砼空间框架节点在双向反复荷载作用下的试验研究结果,其主要的研究参数是柱梁抗弯强度比值、约束构件尺寸(梁与板)、节点配筋、柱轴向力以及加荷过程。对节点的滞回特性和通过节点的梁筋与柱筋的滑移也进行了研究。在试验结果的基础上,提出了在地震型荷载作用下空间框架节点的设计建议,其中包括柱梁抗弯强度的最小比值、约束梁梁宽与柱宽的最小比值、节点抗剪强度的计算方法以及梁纵向钢筋在节点内的最小锚固长度。     

Fire design method for concrete filled tubular columns based on equivalent concrete core cross-section

In this work, a method for a realistic cross-sectional temperature prediction and a simplified fire design method for circular concrete filled tubular columns under axial load are presented. The generalized lack of simple proposals for computing the cross-sectional temperature field of CFT columns when their fire resistance is evaluated is evident. Even Eurocode 4 Part 1-2, which provides one of the most used fire design methods for composite columns, does not give any indications to the designers for computing the cross-sectional temperatures. Given the clear necessity of having an available method for that purpose, in this paper a set of equations for computing the temperature distribution of circular CFT columns filled with normal strength concrete is provided. First, a finite differences thermal model is presented and satisfactorily validated against experimental results for any type of concrete infill. This model consideres the gap at steel–concrete interface, the moisture content in concrete and the temperature dependent properties of both materials. Using this model, a thermal parametric analysis is executed and from the corresponding statistical analysis of the data generated, the practical expressions are derived. The second part of the paper deals with the development of a fire design method for axially loaded CFT columns based on the general rules stablished in Eurocode 4 Part 1-1 and employing the concept of room temperature equivalent concrete core cross-section. In order to propose simple equations, a multiple nonlinear regression analysis is made with the numerical results generated through a thermo-mechanical parametric analysis. Once more, predicted results are compared to experimental values giving a reasonable accuracy and slightly safe results.     

低周反复荷载作用下钢筋混凝土框架梁柱节点核心区抗剪强度的试验研究

本文通过30个钢筋混凝土框架梁柱节点在低周反复荷载作用下的试验,对梁柱节点核心区的受力性能以及影响核心区混凝土抗剪强度的几个主要因素,如直交梁约束、轴压比、剪压比、配箍率以及梁纵筋在核心区的锚固滑移等进行了研究,并提出节点核心区混凝土抗剪强度计算公式及有关设计建议。同时进行了6个转移梁塑性铰的节点试验,探索了避免梁纵筋在节点核心区的滑移、改善节点抗震性能的新途径。     

钢筋砼扁梁结构的抗震性能及其设计方法

采用钢筋砼扁梁结构是一种降低高层建筑层高的有效途径。由于梁宽大于柱宽,因此其梁柱节点的抗震性能较为复杂。为解决这类结构的设计问题,本文通过5个中柱扁梁节点和2个边柱扁梁节点在低周反复荷载下的试验以及3根约束扁梁在弯、剪静力荷载下的试验,基本摸清了扁梁结构的静力性能及抗震性能。根据受力特征和破坏形态的机理分析,提出了扁梁结构的实用强度计算方法及有效的配筋构造措施。     

Experimental study of structural fire behaviour of steel beam to concrete filled tubular column assemblies with different types of joints

This paper presents experimental results of structural fire behaviour of steel beam to concrete filled tubular (CFT) column assemblies using different types of joints. The joint types include fin plate, end plate, reverse channel and T-stub. The structural assembly was in the form of a “rugby goalpost”. In each test, loads were applied to the beam and then the structural assembly was exposed to the standard fire condition in a furnace while maintaining the applied loads. In total, 10 tests were carried out. In eight of the 10 tests, fire exposure continued until termination of the fire test, which was mainly caused by structural failure in the joints under tension when the beam was clearly in substantial catenary action. In the other two tests (one using fin plates and one using reverse channels), fire exposure stopped and forced cooling started when the beam was near a state of pure bending and just about to enter into catenary action. The results of the experiments indicate that even the relatively simple joints used in this study were able to allow the beams to develop substantial catenary action so that the final failure times and beam temperatures of the assemblies were much higher than those obtained by assuming the beams in pure bending. At termination of the tests, the beams reached very high deflections (about span/5), even then failure of the assemblies always occurred in the joints. Therefore, to enable the beams to reach their full potential in catenary action, the joints should be made to be much stronger. The results also indicate that reverse channel connection has the potential to be developed into a robust connection characterised by high stiffness, strength, rotational capacity and ductility. The beams in the two cooling tests developed high tension forces, however there was no structural failure in the assemblies. The principal aim of this paper is to present experimental results of joint behaviour in fire (which until now is lacking) to enable development of better understanding and rational design methods for robust construction of joints to resist extreme fire attack.