In 2010 the VFT-Rail® system was approved in accordance with CEN and railway standards by Germany's Federal Railway Authority (EBA) for operational testing. The approval was accompanied by a monitoring campaign on a VFT-Rail® bridge crossing the River Simmerbach. As a result of the positive experience gained during the operation of this bridge, two additional railway bridges were designed by SSF Ingenieure AG and put into service in 2014 by Deutsche Bahn (DB). To survey those bridges, a monitoring programme has been developed and instigated. The monitoring programme includes investigating the stress distribution between the concrete and specially designed composite dowels, which have a better fatigue resistance compared with conventional headed studs. The forces at several rail support points are also a focus of interest. The German railway operator DB Netz AG requested the survey to prove the applicability of state-of-the-art calculation methods, which were not part of compulsory codes.

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This paper presents additional potential for the future economic development of composite dowel strips by using the durable and long-lasting corrosion protection of hot-dip galvanization. Based on the completed FOSTA research project P835 [5] on the use of hot-dip galvanizing for steel and composite bridge construction, the range of applications for hot-dip galvanizing will be transferred to composite dowel strips in composite bridges. Following a brief summary of the most important results of the previous project, where the corrosion protection duration and the influence of hot-dip galvanizing on the fatigue behaviour of steel were examined, the objectives and planned studies of the new research project will be presented. The currently ongoing FOSTA research project P1042 [8] was initiated by RWTH Aachen University and TU Dortmund University. The results should allow the safe use of hot-dip galvanized composite dowel strips in conjunction with cyclic loads.

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Substitute structures for old railway bridges with open railway tracks, which are constructed in accordance with valid European standards and regulations, require a specific, suitable deck slab design. Therefore, a composite plate with cellular longitudinal shear connectors and a low overall depth of 200 mm has been investigated at the Research Centre of Steel Structures (TU Wien). The research programme comprised experimental studies as well as additional numerical analyses by means of the finite element method concerning the shear force transmission-mechanism of the sandwich design. Laboratory studies included, among other issues, information about the failure mechanism in the core concrete. This article provides a description of the test program and gives a brief summary of selected research results. A short overview on continuing research activities to determine the serviceability, the load-bearing capacity as well as the fatigue strength of the sandwich plate is presented.

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The floods in the Czech Republic in the last few decades have resulted in a significant number of bridges having to be rebuilt. Unfortunately, the work meant long-term traffic closures for railway bridges, coupled with significant costs for renovation and for providing alternative transport services. As a result, the minimum clear headroom above the design flood level required for new bridges and for reconstructing existing bridges has been increased. This initiated a search for new approaches to designing individual parts of bridge crossings, aiming to comply with the stricter conditions. The research aims to decrease costs in comparison with the costs of raising the finished grade level of the railway, especially at places where adjacent sections such as railway stations etc. are connected.

The European research programme SBRI attempted to reveal the costs caused during the service life of a bridge - direct costs for the bridge owner as well as indirect costs for users. The principal results of SBRI should make it possible to take better account of the true costs of a central pier by considering the risks in the construction phase and those that may threaten the highway overpass during its service life.
CEREMA has developed two economic solutions to reach the objective of avoiding the central pier:
1) The solution implemented at Ko Wé Kara in New Caledonia is a steel-concrete composite tied arch bridge with innovative and economic details:
- innovative radial hangers made of welded plates, and
- innovative reinforcement against accidental impact of over-height vehicles.
2) One other possible solution is the composite steel-concrete gantry bridge. The European research programme PRECOBEAM allowed the use of tests and experimental projects to finalize a new system of connection to lower the cost of this type of structure: a strip along which the cutting line of the steel dowels is made in a clothoid shape (CL), which improves the fatigue resistance. CEREMA introduced this innovation in its research programme.
A composite structure can take various forms. It can associate, for instance, the steel web of a beam directly with a concrete flange. It can also constitute a composite deck with a bottom plate stiffened by connecting CL-shape indented strips. An outstanding project of this type in New Caledonia is described in detail. Of course, this type of bridge is an integral bridge and the article includes some recommendations for the design and construction of integral bridges.

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Glass is used in current construction applications mostly as a façade element, its structural role being only rarely exploited, despite its significant resistance to in-plane compression. A steel-glass composite beam was built to investigate a hybrid steel-glass assembly and its loadbearing behaviour. To fulfil this objective, the existing types of steel-glass connection were evaluated, which allowed the possibilities offered by adhesive jointing to be highlighted. The selection of the adhesive, detailed in the present article, constituted a crucial aspect. An excessively soft connection does not transfer the shear loads between the glass and steel adherends, whereas an excessively stiff connection leads to failure of the glass. A two-component structural silicone was chosen and its properties were assessed with the help of an intensive test programme. As a result of this programme, a new quasi-incompressible hyperelastic material law was developed in order to represent the silicone elastomer behaviour. Numerical simulations were conducted in parallel to large-scale four-point bending tests on the adhesively bonded steel-glass composite beams. The aims were, on the one hand, to assess the bending stiffness of the steel-glass composite beam and, on the other, to validate the numerical simulations to conduct parametric studies.

A new rivet fastened rectangular hollow flange channel beam (RHFCB) was proposed using an intermittently rivet fastening process as an alternative to welded beams. The rivet fastened RHFCB allows greater section optimisation and flexibility in designing suitable combinations of web and flange widths and thicknesses for many industrial applications. In the industrial applications of rivet fastened RHFCBs as flooring, roofing or modular building systems, their flanges will be fastened to supports, which will provide increased capacities. However no research has been conducted to investigate the web crippling capacities of RHFCBs with flanges unfastened and fastened to supports under one-flange load cases. Similarly the applicability of current design rules for cold-formed steel sections are not suitable for rivet fastened RHFCBs. Hence to address these issues, an experimental study was conducted to investigate the web crippling behaviour and capacities of RHFCBs based on the new AISI S909 standard test method. This study included rivet fastened RHFCBs with flanges unfastened and fastened to supports under End One Flange (EOF) and Interior One Flange (IOF) load cases. Tests with flanges fastened to supports showed that web crippling capacities increased by 39 and 5 % for EOF and IOF load cases. Comparisons of experimental web crippling capacity results with predictions using the current AS/NZS 4600 and AISI S100 design standards showed that web crippling design equations are conservative for rivet fastened RHFCBs with flanges unfastened and fastened to supports under EOF and IOF load cases. Hence new equations are proposed to determine the web crippling capacities of rivet fastened RHFCBs. This paper presents the details of this web crippling experimental study of rivet fastened RHFCB sections and the results.

This paper presents and clarifies the treatments included in EN 1993-1-1 [1] relating to checking the resistance of steel cross-sections under torsion and its interaction with other internal forces. Specifically, the origin of the formulations for shear-torsion interaction, which has not been found in the literature, is presented. Furthermore, a very simple formulation based on the expressions used for shear-torsion interaction is developed in order to take into account bending-warping torsion interaction for symmetrical I-sections (IP and HE steel profiles). Such a formulation overcomes the overly conservative approach given in EN 1993-1-1 [1] for class 1 and class 2 cross-sections (plastic and compact cross-sections). Finally, a rigorous method for determining the bending resistance of cross-sections is proposed considering the interaction with shear and torsion. The proposal is well suited to the concept of cross-section class and is perfectly consistent with the approaches set out to consider bending-shear and bending-warping torsion interactions.

The Bory Mall Shopping Centre, designed by the Italian architect Massimiliano Fuksas, is a mixed use development located on the outskirts of Bratislava, Slovakia.
The roof to the shopping mall's central plaza is a free-form steel gridshell. The concept for its shape is consistent from the footprint to the shape of the grid nodes. The gridshell is assembled from standard rolled steel hollow sections but uses the freedom created by individually shaped CNC-milled grid nodes to achieve a smooth transition between high slenderness at the bottom and the necessary stiffness at the top.
Working in close collaboration with Massimiliano Fuksas Architects, Knippers Helbig provided support for the development of the roof structure right from the start of the project and rounded off their services by providing detailed design of the free-form central “Tornado” façade grid nodes, which were fabricated and built by Metal Yapi.

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Events:
The Pacific Structural Steel Conference 2016 / WINERCOST'17 /P Eurosteel 2017

Announcements: In Memoriam / Numerous reaction and testimonies have been received / Steel Construction Day 2016 in Belgium / Steel Construction Day 2016 in Norway
Technical Committees (TC) activities

TC news: Activities of ECCS TC6 „Fatigue and Fracture” / News from ECCS-TC 11 „Composite Structures” / Annex A - Membership / News from ECCS TC16 „Wind Energy Support Structures”

Other ECCS news: ECCS Meeting 2016 / EUROPEAN STEEL BRIDGES AWARDS CEREMONY

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Composite dowels are known as powerful shear connectors in steel-concrete composite girders. They are being used more and more in practice, especially for prefabricated composite bridges. Compared with headed studs, they provide increased strength. They also exhibit good deformation capacity even in high-strength concrete. Further, their use in steel sections without an upper flange is very simple. However, a lack of standards for composite dowels with the economic clothoid and puzzle shapes has led to hesitations regarding applications, which is often due to delays in the approval process. Hence, the aim of the recently finished German research project P804 funded by FOSTA, the Research Association for Steel Application, was to solve unanswered questions concerning these innovative shear connectors and to prepare a national technical approval available for any design office or construction company. This paper describes the technical rules derived for ultimate and fatigue limit states, the structural design principles and instructions for production and construction, and provides further background information.

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The design concept for the steel part of a composite dowel shear connection is based on a geometric stress concept and it assumes the superposition of individual stress components resulting from longitudinal shearing and bending of a composite section. Analytical transformations of FEM calculation results for critical regions in steel dowels lead to the solution represented by closed interaction curves for the dimensionless shear resis tance of the connection versus the axial resistance of the web.

The theoretical background to the elastic design of steel dowels is presented in [1], what constitutes the basis for Fatigue Limit State (FLS) and Serviceability Limit State (SLS) are given. In this paper assumptions for Ultimate Limit State (ULS) and mechanical models are presented for both shapes covered by the German National Technical Approval [2]. The yield strength of steel is assumed in the plastic design of steel dowels, contrary to the tensile strength of steel used in the case of headed studs. A dis cussion on this aspect is presented using results obtained by finite elements which are presented in [3]. Hence, a consistent approach for ULS, SLS and FLS is established which is based on the statement that the resistance of a unit length of a shear connection with steel dowels does not depend on the size of the dowels and the ductility of the connection is a linear function of the dowel size.

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