Stahl‐Beton‐Haftverbindungen für Verbundbrücken – Versuche und Bemessung

Connections by adherence for steel‐concrete composite bridges – tests and design. This paper presents experimental and analytical research that was conducted on new connections “by adherence” for steel‐concrete composite bridges. Their resistance is due to the frictional shear resistance of different interfaces positioned in a judicious manner. These connections makes it possible to erect the structure quickly with full‐depth precast concrete slabs, while the concreting works on site are as much as possible limited. Experimental results show that these connections exhibit a high resistance to horizontal shear forces and are very stiff compared to traditional connectors (headed studs). However, their ductility is limited. Based on the experimental results, a calculation model, taking into account the deformation observed during the tests and behavior laws for interfaces, was then developed and used in a parametric study. Some results are presented and discussed. A simplified method for determining the resistance of these connections, based on these results, some design rules as well as some recommendations for construction are finally proposed. The behavior of steel‐concrete composite beams with connections by adherence is also shortly discussed.     

夹层玻璃金属植入节点抗拉拔性能研究

结构玻璃一般采用夹层玻璃。对于夹层玻璃构件,可采用金属植入节点来实现构件间的连接,但目前缺少成熟的金属植入式节点承载力设计方法。为此,设计并制作了5个采用离子性中间层的夹层玻璃金属植入节点,通过静力试验研究金属植入节点的抗拉拔性能,得到了节点的破坏形态及节点在拔出过程中的荷载-位移曲线。试验中节点破坏由胶片脱黏控制,且具有一定的延性破坏特征。通过理论推导得到了考虑胶片拉伸及剪切变形协调的胶片内力计算方法和节点承载力计算方法,将拉伸黏接面脱黏时定义为金属植入节点的承载能力极限状态,建议设计时应保证外层玻璃具有足够的强度。通过试验结果与理论计算结果进行对比,验证了所提出承载力计算方法的合理性。     

Grout‐Verbindungen von Monopile‐Gründungsstrukturen – Trag‐ und Ermüdungsverhalten

Grouted Joint Connections of Monopile Support Structures – Structural and Fatigue Behaviour. This paper summarises the state of the art for grouted connections of support structures of Offshore Wind Energy Converters (OWECs). Results of numerical and experimental investigations of small and large scale tests of grouted joints which have been carried out within the research project “ForWind – TP V: Fatigue Assessment of Support Structures of Offshore Wind Energy Conversion Systems” at the Institute for Steel Construction, Leibniz Universität Hannover are presented. Furthermore the results of the numerical and experimental investigations are used for an exemplary calculation of a grouted joint connection of an OWEC located in the Baltic Sea. Besides the analysis of grouted joints with plain pipes the effects of an increased mechanical interlock due to shear keys on the fatigue design of grouted connections is demonstrated and fatigue classes for shear keys are presented.     

Experimental and numerical investigation on the shear behaviour of friction-welded bar-plate connections embedded in concrete

Friction-welded bar-plate connections are a basic structural component of Bi-steel steel-concrete-steel sandwich construction. In Bi-steel members, the bar-plate connections, embedded in concrete, are subject to tension, shear and bending. The static and fatigue behaviour of the embedded connections subjected to bar tension is described in another paper [Xie M, Chapman JC. Static and fatigue tensile strength of friction-welded bar-plate connections embedded in concrete. Journal of Constructional Steel Research [in press]]. This paper presents experimental and numerical studies on the static behaviour of the friction-welded connections with the bar loaded in shear. Finite element analysis is carried out to examine the effects of variations in geometric and material parameters. The experimental results are used to derive an empirical equation for predicting the shear strength of embedded connections, and compared with existing test results and code specifications. Further papers will describe fatigue behaviour of the embedded connections subjected to bar shear, and static and fatigue tests on Bi-steel beams.     

Point fixings in annealed and tempered glass structures: Modeling and optimization of bolted connections

In the design of high load bearing elements made of tempered flat glass, connections cannot be avoided when large spans or high stiffness beams are considered. This paper investigates bolted connections in glass structures; the main objective is to determine the optimal joint. This work is performed through the determination of stress states due to both thermal tempering and in-plane loading. The modeling of the thermal tempering is performed with the FE software Abaqus and additional user subroutines. Experiments on industrial tempering line with specific set-up allow the determination of the air flow in the hole and then of the forced convection coefficients. The radiative heat transfer is also modeled numerically and the semi-transparency of glass in the near infrared is considered. In order to calculate residual stresses, the visco-elasticity of glass and the structural relaxation phenomena are taken into account. The computed stresses are checked against photo-elastic measurements. As various holes are considered, this study allows to determine the hole geometry for which the tempering process is the most effective. For the study of the consequences of in-plane loading, a large experimental campaign has been performed. The studied connection is derived from countersunk supports. The influences of different parameters as the hole geometry, the nature of the washer between glass and metallic connector as well as the glass-washer material friction coefficient were investigated. The modeling of these tests is performed with the FE software Abaqus. This modeling takes into account the ductility of the materials, the friction and the clearances between the parts. This modeling is validated thanks to failure stress measurements. The combination of modeling and experiments leads to identify optimal connection.     

Hysteretic behaviour of dissipative bolted fuses for earthquake resistant steel frames

One of the most recent trends in earthquake-resistant design of structures – damage control when these are subjected to severe earthquakes – led to the development of an innovative repairable fuse device for dissipative beam-to-column connections in moment resistant steel frames with composite beams. This fuse consists of a set of bolted steel plates, at the web and bottom flange, connecting the “I” beam profile stub to the beam element. The seismic performance of the proposed device was assessed through an extensive experimental campaign comprising twenty-four cyclic and two monotonic tests. Those tests were conducted on a set of three beam-to-column sub-assemblies with different fuse devices for each test. The tested devices varied in terms of selected geometric and mechanical parameters, such as the resistance capacity ratio and the geometric slenderness. The tests showed that the proposed devices were able to concentrate plasticity and to dissipate large amounts of energy through non-linear behaviour. Subsequently, two distinct design models are proposed to allow the computation of the resistance and stiffness of the fuses. The results of these design models were favourably compared with those from the experimental tests.     

Laser welded built-up cold-formed steel beams: Experimental investigations

The results of a research project aimed at designing and development a built-up cold-formed steel beam assembled by laser welding are described in this paper. The research activity was concerned with the evaluation of the applicability of laser welded connections to cold-formed members and with the assessment of the load bearing capacity of the assembled beams. With this aim, both lap-shear and U-tension tests were carried out on laser welds in order to assess the influence on connection strength of different parameters such as the gap between the steel sheets and the zinc coating. Finally, the load bearing capacity of laser welded built-up cold-formed members was investigated by four-point bending tests. Four full-scale prototypes were manufactured with different spacings of connections along the flanges in order to evaluate the effects of weld configuration on the load bearing capacity.     

Möglichkeiten der Bemessung von Bauteilen aus Glas

Methods for design of structural elements made of glass. The application of structural elements made of glass became more common and nowadays appear to be standard. For the design of such elements legal conditions and background have to be obeyed. In addition knowledge about design rules and – for special problems – alternative methods and technical background is necessary. In this paper the past and present regulations and related questions for design of structural elements of glass are presented. Finally an outlook for future design methods and regulations in context with the modern concept of partial safety factors is given.     

Projekt Steel Earthquake Design (SEQD) – Erdbebenresistentes Stahlbausystem für Wohnhäuser

The SEQD – Steel Earthquake Design – project for earthquake‐resistant residential buildings. The construction material steel is currently mostly applied in highly‐engineered structures like bridges, industrial halls or high‐rise buildings. The SEQD – Steel Earthquake Design – project had the aim of developing a safe and economic solution for small residential buildings in earthquake regions. The basic idea of the system is to combine an engineered steel frame as primary structure with non load‐bearing infill walls from local materials. The new design includes innovative connections between frame elements and special uniaxial couplings between walls and steel frame. Reinforcement of the infill walls is achieved by applying grids from synthetic materials. In October 2004 experimental tests on a prototype structure were carried out in an assembly hall of the Rudolstädter Stahlbau GmbH.     

Experimental Investigation of T-Stub Link-to-Column Connections in Eccentrically Braced Frames

Link-to-column connections in eccentrically braced frame should transfer large shear and moment developed in a fully plastic and strain hardened link. Moreover, the connection should allow the link to undergo large plastic rotations. It was observed in previous studies that link-to-column connections are failed before achieving the plastic link rotation capacity. Design of link-to-column connections in seismic-resistant eccentrically braced frames is still an unresolved problem. In this paper, experimental tests are carried out on long link-to-column connections. T-stub connections are used for connecting the link to column. The test parameter is the strength of connection by changing the connection details. The results of the tests indicate that the proposed connections can successfully achieve the desired rotations without any strength loss.     

Stahlglas‐Bauweise – Rechnerische und experimentelle Nachweise am Beispiel einer Treppe

Stahlglas‐structure – design check and load test. The following article deals with the design checks at the “ultimate limit state” of a Stahlglas structure, using a free‐carrying glass staircase as exhibited at the ‘glasstec2004’ as an example. In an earlier paper published in this journal, the construction details of the most important elements, including an explanation of the fundamentals of the safety concept of the Stahlglas construction method, was presented. In this paper, the design checks which are explicitly required for this structure are described, together with the testing of individual structural components and final test loading.     

长柱无牛腿装配整体式多层框架设计与试验研究

本文对多层工业厂房提出了采用长柱无牛腿、齿槽槽钢梁柱连接的新的框架结构体系。文中对结构方案、构件试验及设计计算均作了较详细的介绍,并附有某工厂近二万平方米的六层厂房工程实例。     

Neue Messe Mailand – Verglasung der Freiformfläche

The New Fair of Milan – glass on free-form surfaces. The glazing of free-form surfaces often has to fulfil many expectations – highly stressed, light-weight and economic. The construction must ensure post-breakage safety but still appear filigran and transparent. The glazing of the free-form surfaces of Milan's New Fair is described with special attention to structural analysis, details and typical problems resulting from the free-form geometry.     

Investigation on the inelastic behavior of full-scale heavy clip-angle connections

This paper describes the investigation on the inelastic behavior of steel heavy clip-angle connections subjected to static loading. The work depends on the results of a large experimental investigation into the cyclic behavior of full-scale connections involving thick clip-angle components. The results of these experimental tests are described first, and then a methodology to simulate the response of clip-angle connections numerically using nonlinear finite element (FE) models is mainly treated in this study. Extensive studies utilizing numerous 3D models are discussed, including the introduction of the pretension force into the bolts and the effects of small changes in geometry on the deformation capacity of the angles. Generally, FE test results show a good agreement with experimental test results. These outcomes indicate that it is possible to model such connections successfully if care is exercised in the modeling phase. Moreover, these FE models provide useful instrumentation which is difficult to obtain during an experiment. They have widely been used to understand the parametric effect of connection components and establish a comprehensive study of their inelastic behavior including slip deformation and prying action.     

Moment-rotation-temperature curves for semi-rigid joints

Although connections are known to have a very significant effect on the behaviour of steel and composite framed buildings in the event of fire, the cost of high temperature tests on the broad range of connections used in practice means that their influence is not well detailed in current design codes. The paucity of data also limits the effective use of numerical models developed to simulate the behaviour of complete structures at elevated temperature. This research describes a series of elevated temperature tests conducted on beam-to-column connections. This paper presents moment-rotation-temperature curves for a variety of connections.     

Ermittlung der Grenztragfähigkeit von Mehrschraubenverbindungen bei Normalkraft‐Biegemoment‐Interaktion

Determination of the ultimate bearing capacity of multi‐bolt connections with normal force – bending moment – interaction. This paper will present a general design method for single or multi‐bolt connections of beams with arbitrary thin‐walled cross sections, suitable for application in computer programs. The design method is based on the classical strain iteration algorithm for the determination of the stress distribution in cross sections. In this case, the ultimate capacity of bolted connections will be obtained using an iterative numerical determination of the elastic‐plastic stress distribution in the connection elements. The numerical method will be derived in two steps – the first step is the numerical determination of the stress distribution in the connection for a given combination of internal forces and the next step is the determination of the ultimate bearing capacity of the connection. Furthermore, an analytical design method for a multi‐bolt tube connection will be derived. Finally, results of numerical and analytical calculations will be compared with corresponding test results.     

Tragfähigkeit von Lochleibungsverbindungen vorgespannter Glasscheiben zur Ausbildung von Anschlüssen im Konstruktiven Glasbau

Strength of bearing connections in toughened glass plates for the structural use. In steel structures due to their “infinite'” ductility the bearing connections are standard components of joints. Their design rules are based on simple engineering models. However if analogous bearing connections are subject of glazing structures the requirements on the materials' ductility cannot be met. Therefore interlayers out of mortar etc. in the hole surrounding the bolt have to be introduced such that a ductile load deformation behaviour can be reached reducing stress peaks and avoiding steel‐glass‐contact. On this basis design rules are to be established to predict the load carrying capacity of bolts in glass bearings. The following investigations describe the experimental and theoretical works to derive an engineering model for this purpose.     

Cyclic behaviour of bolted cold-formed steel moment connections: FE modelling including slip

In this paper a Finite Element (FE) procedure is described for simulating hysteretic moment–rotation behaviour and failure deformations of bolted cold-formed steel (CFS) moment connections. One of the main challenges in modelling the response of bolted connections is the presence of bolt slip. A series of six beam–column assemblies comprising CFS curved flange beams, a support column and a through plate were tested under cyclic loading. The moment–rotation behaviour of the connections was dominated either by flexure in the beams or by bolt slip in the connections. FE models presented in this paper incorporate geometrical imperfections of the beams, material properties obtained from tensile coupon tests and bolt slip to address these two types of behaviour. The updated FE models result in an accurate prediction of the hysteretic moment–rotation behaviour of the connections dominated by a flexural behaviour in the beams. A simplified cyclic slip model which allows slip at a specified reduced slip resistance load simulates reasonably well the hysteretic behaviour of connections dominated by bolt slip. Using the updated FE model, the failure modes of the connections predicted by the simulations also agree well with those observed in the experiments.     

Thermo-mechanical behaviour of timber-to-timber connections exposed to fire

A numerical model is developed to analyse the thermo-mechanical fire behaviour of timber-to-timber dowelled and bolted connections in tension parallel to wood grain. The experimental results of two series of tests are used to validate the model based on three-dimensional (3D) finite element modelling. The thermo-mechanical performances of the connections are determined using two different meshing and calculation procedures. The thermal model meshing is continuous to take the thermal continuity between the connection components into account. Regarding mechanical and thermo-mechanical calculations, the meshing is discontinuous to consider the gap and the contact changes between the connection components. The thermal model takes into account the evolution of physical properties of materials as a function of the temperature and is calibrated according to the experimental measurements. The thermo-mechanical model considers the mechanical properties – temperature evolutions of the materials provided by the corresponding Eurocodes. The thermal model can predict the temperature fields inside the connection components. Its validation is conducted through comparison with the experimental temperatures measured in different places inside the connections. The mechanical model is validated using the experimental load–slip curves of the connections in standard conditions. Finally, the thermo-mechanical model is validated by considering the global time–slip curves and by determining the fire resistance rating of the connections. A good agreement is obtained between simulated fire resistance times and experimental ones.     

A connection element for modelling end-plate connections in fire

In this paper a robust 2-noded connection element has been developed for modelling the bolted end-plate connection between a steel beam and column at elevated temperatures. The connection element allows the element nodes to be placed at the reference plane with offset and the non-uniform temperature distributions within the connection. In this model the connection failure due to bending, axial tension, compression and vertical shear are considered. The influence of the axial tensile force of the connected beam on the connection is also taken into account. This model has the advantages of both the previous simple and component-based models. A total of 23 fire tests were used to extensively validate the model. It can be seen that the current model is robust and has a capability to predict the behaviour of a bolted end-plate connection under fire attack with reasonable accuracy. Compared to the tested results the predictions of the current model were mainly on the conservative side. Hence, the model can be used for structural fire engineering design on steel-framed composite buildings. The idea described in this paper can also easily be applied to develop other kinds of connections, such as simple connections, column based connections or hollow section connections, and so on.