Stefanie Weidner and Walter Haase: The Implementation of an Adaptive High-rise Building
Bill Baker: The Design of Structural “Spider” Webs
Roland Bechmann, Stephen Hagenmayer and Thomas Winterstetter: Efficiency and Beauty - Steel Structures by Werner Sobek
Frank Barkow and Regine Leibinger: In Dialogue
Stephan Engelsmann and Stephan Peters: Emblematic steel roof structures for central bus stations in Baden-Württemberg / Germany
Walter Grasmug and Lucio Blandini: The Role of Steel in Innovative Building Skins

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The authors have studied the buckling-restrained brace providing a stable hysteretic characteristic even under high-strain conditions. The structural performance of the buckling-restrained brace is represented by the evaluation formula that is the lower limit of the cumulative plastic strain energy ratio. However, as earthquakes are becoming much longer, so it is necessary to research and develop a new buckling-restrained brace with a higher energy dissipation capacity. In this paper, our past studies are reviewed and the conditions of high-performance of buckling-restrained braces extracted. The buckling-restrained brace considered was tested. As a result, a buckling-restrained brace with a larger cumulative plastic strain energy ratio is proposed.

This paper compares the buckling strengths derived from a validated shell-based FEM model of discretely supported axially compressed silos with the interaction curves given in EN 1993-1-6 for axial compression. The buckling strengths were numerically determined for a wide range of geometries and yield strengths, considering two configuration types of discretely supported steel silos: with engaged columns and partial-height U-shaped longitudinal stiffeners. For these types, remarkably good correspondence was found between the numerical results of discretely supported steel silos and the interaction curves for uniformly compressed cylindrical steel silos, although unconservative in many cases.

Dedicated to Prof. Dr.-Ing. Helmut Saal on the occasion of his 75th birthday
Diaphragms made of trapezoidal profile sheeting are often used to stabilize members or work as bracing to transfer horizontal loads (wind or seismic loads) to the ground. In Europe there are currently two approaches for the design of these shear diaphragms, both often denoted by the names of their corresponding developers: Schardt and Strehl and Bryan and Davies. Although the mechanical background to calculating the diaphragm stiffness is more or less identical in both approaches, there are differences in the level of detailing, i.e. in the number of parameters regarded as significant for practical design. Generally, the Schardt/Strehl approach was reworked much more and is therefore easier to use in practical design. On the other hand, the Bryan/Davies approach is much more realistic regarding the failure modes (shear buckling, failure of fasteners) and loadbearing capacity. This paper discusses the differences and similarities in detail, makes an assessment and highlights the particular advantages.
Recently, a new approach was elaborated based on work previously carried out by Baehre and Wolfram and taking into account new developments and findings. This “combined approach” presented here combines the advantages of the Schardt/Strehl and Bryan/Davies approaches as given above. The paper includes a comparison with test results with regard to both diaphragm stiffness and loadbearing capacity.
Detailed information is given on how to elaborate the sheeting-related parameters in tables, allowing for easy use in practical design. This is of special importance for implementation in practical design and in relation to the further development of the Eurocodes.

Steel design codes continue to be expanded to permit the use of more advanced methods of non-linear analysis. Designers looking to employ such methods need to validate their analysis software and, just as importantly, verify their ability to utilize it properly. The literature contains many benchmark problems and results to help achieve this, but nearly all are limited to two-dimensional behaviour. This paper is intended to contribute a new set of benchmark problems in order to help satisfy the need for a database of examples in which accurate modelling of three-dimensional or spatial behaviour is essential.

According to Eurocode 3 Part 1-1, the resistance of compression members may be calculated in two different ways: through the design buckling resistance based on the reduction factor &khgr; or through the cross section resistance based on internal forces according to a second order analysis, also taking into account equivalent initial bow imperfections e0. The second way is especially advantageous in the case of axial forces and bending. Values for equivalent initial bow imperfections e0 are given in codes like Eurocode 3 [4] or DIN 18800 [3]. The presently used values from Table 5.1 of Eurocode 3 will have to be changed in future, as was demonstrated recently by intensive investigations, especially for cases of axial compression and bending moments My or Mz respectively. Additional investigations concerning high-strength steel S700, welded sections and circular hollow sections are presented. The proposed changes included in the newest draft of prEN1993-1-1 are explained through the evaluation of several ultimate load calculations. It is also shown that for the case that the initial bow imperfection e0 is calculated dependent on the non-dimensional slenderness , restrictions regarding interaction and the ratio of Mpl/Mel are also necessary.

The rotational capacity of beams made of high-strength steel grades S700 and S960 was investigated within the scope of the RUOSTE research project, which was partly funded by the RFCS. Beams made of high-strength steel are supposed to have a lower rotational capacity, and are thus excluded from plastic/plastic design according to [1], [2]. Although the strain hardening of high-strength steel material is generally lower than that of mild steels, for some structures with discrete plastic hinges, the rotational capacity might be still sufficient to reach the respective cross-section classification. In the research presented here, eight tests on beams in bending were carried out to assess the limit of cross-section class 1 for high-strength steel.

To perform geometrically and materially non-linear analyses including imperfections for steel beam lateral torsional buckling, the size and shape of the geometric imperfection can be taken from EN 1993-1-1. The shape is prescribed as an initial bow along the weak axis of the section, excluding torsion of the cross-section. Alternatively the shape of the imperfection can be taken equal to the lateral torsional buckling mode, including torsion. Several tables and formulae exist for the determination of the size of the imperfection. In this article, different imperfection approaches are presented for finite element simulations to evaluate lateral torsional non-linear buckling resistances and to compare these to results obtained with design rules. Based on the comparisons made, the article concludes with a proposal for design imperfections to be used in non-linear Finite Element Analyses (FEA) for lateral torsional buckling of beams.

Significant research effort has been devoted in recent years to the evaluation of the capacity of steel frame structures to resist progressive collapse after sudden column loss. Due to the complex load-structure interaction and material behaviour, it can be very difficult to evaluate the ultimate capacity of structural components using current analytical methods. Therefore considerable research effort has been directed to experimental testing and sophisticated numerical simulations. Although sudden column loss is a dynamic process, most experimental studies on full-scale or scaled down specimens were performed under quasi-static loads. This paper presents the results of a study devoted to the evaluation of steel frame response following the loss of a column. Advanced numerical models are calibrated using experimental test results and dynamic increase factors are studied. Several full-scale structures are investigated for a sudden column loss scenario.

This paper describes a calculation method for steel plate girders with transverse web stiffeners subjected to shear. It may be used to predict the failure load or, as a design method, to determine the optimal number of internal web stiffeners. The method is based on the theory of plasticity. Many other theories have been developed, but the method presented here differs from these theories by incorporating the strength of the transverse stiffeners and by assuming that the tensile bands may pass the transverse stiffeners - an effect often observed in tests. Other methods have only dealt with a single web field between two stiffeners.
The load-carrying capacity may be predicted by applying both the lower-bound and upper-bound theorems. The upper-bound solutions show very good correlation with existing tests. The emphasis is placed on the presentation of the tests conducted at the Technical University of Denmark. The test programme comprised six full-scale plate girder specimens. Agreement between the theory and the tests is very good.

World trade is steadily increasing, leading to a high demand for economic solutions for quay walls. The combined steel pile wall is the most common steel construction solution. The primary elements are king piles, while intermediate piles function as secondary elements. The design of these secondary elements is governed by section 5.5.2 of EN 1993-5 [9]. The test-based method described in section 5.5.2(5) and (6) is used to generate the characteristic water pressure resistance values of the different combinations of I-shaped king and Z-shaped intermediate piles, each in different steel grades, which are given in the product catalogue of ArcelorMittal [1]. The test series executed and the subsequent setting-up and validation of a numerical model are presented in detail in this paper. A numerical model was used for a parametric study. The different failure modes observed in this parametric study are presented. A statistical evaluation according to Annex D of EN 1990 [6] and Annex C of EN 1993-1-5 [8] leads to characteristic resistance values.

Angle sections are widely used in civil engineering applications and especially in lattice towers for telecommunication purposes. The principal and geometrical axes of angle sections do not coincide and exhibit very low rigidity when it comes to uniform and non-uniform torsion. Thus, design expressions, e.g. those included in EN1993-1-1 or EN 1993-3-1, do not apply for cross-sections or members composed of angle sections. In addition, limited experimental investigations of members made from angle sections can be found in the literature, and those are mostly for cold-formed ones. This paper presents a test campaign involving members made from equal-leg hot-rolled angle sections which was carried out at the Institute of Steel Structures of the National Technical University of Athens (NTUA). Tests included eight three-point bending tests and 31 buckling tests on columns subjected to concentric and eccentric compression. The aims of the research are to use the experimental data for the calibration of numerical models, to investigate possible inelastic reserves in angles which have been detected in analytical models and to serve as a reference for the development of new design expressions oriented towards angle sections only.

The flexural strength of steel-concrete composite members depends on both the shear capacity and the ductility of the shear connectors between steel beam and concrete slab. Plastic design strategies of composite beams (equilibrium method) allow the shear strength of the connectors to be easily considered. However, these models do not take into account the deformation behaviour of the connectors nor their limited slip capacity. Several design codes only allow ductile shear connectors with a deformation capacity &dgr;ult of at least 6 mm to be used, while composite beams with non-ductile connectors (&dgr;ult < 6 mm) are excluded from plastic design. Consequently, promising innovative shear connectors with non-ductile deformation behaviour cannot be used economically. Using the example of the miniaturized pin connector, this paper illustrates how finite element models of composite beams - considering both the shear and slip capacities of the connectors - can be used to derive the minimum degree of partial shear connection for beams with limited slip capacity. The proposed modelling strategy and the methodology for deducing the minimum degree of partial shear connection can be transferred and assigned to other types of shear connector with either a ductile or non-ductile deformation behaviour.

Steel Construction has been accepted for inclusion in Scopus
Symposium Smart Bridge - New Developments

Events:
ldquo;Digital planning and building - BIM & Industry 4.0 in steel construction”
Intergalva 2018 - 25th International Galvanizing Conference

Technical Committees (TC) activities: TC3 - Fire Safety
TC7 - THIN GAUGE STRUCTURES
TC9 - Manufacturing and erection standards
TC16 - Wind Energy Supporting Structures

Further ECCS news: STESSA - Behaviour of Steel Structures in Seismic Areas - 14-17 February 2018
ECCS - European Convention for Constructional Steelwork
Design of Steel Structures for Buildings in Seismic Areas

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Slip-resistant connections are always used when slip and deformation in a bolted connection must be avoided at all costs, e.g. in radio masts and bridges. For some popular surface treatments, slip factors are given in EN 1090-2, the execution standard for steel structures. For those surface conditions not considered in EN 1090-2, the slip factor can be determined experimentally according to Annex G of EN 1090-2. By reviewing slip factor values obtained with the Annex G test procedure and reported in the literature, it becomes obvious that in most cases the slip factors achieved experimentally are not comparable for identical surface conditions. This is potentially caused by different interpretations of the Annex G slip test procedure. As the slip factor is one of the main parameters influencing the bearing capacity of slip-resistant connections, its determination should be on the safe side and not dependent on the various interpretation possibilities of the test procedure itself. For this reason, the optimization of the Annex G test procedure was thoroughly investigated in the European RFCS research project SIROCO, with the final objective being to enhance its reliability. The focus was on investigating the various test parameters such as type of preload measurement, ascertaining the possible slip planes, test speed, position of slip measurement, clamping length, preload level, evaluation of critical slip load and the performance of the extended creep test. The results achieved in these investigations have already been partly implemented in the revision of the current draft version of EN 1090-2.

Preloaded bolts are used to achieve slip-resistant shear connections. The actual preload force in each bolt has a direct influence on the fatigue and slip resistance of the connection. The strain gauge method is examined for practical assessment of the actual preload because its use is no longer limited by the demands on adhesive curing conditions. The main objective of the paper is to describe how measured strain in the bolt shank and statistical variation of the nominal mechanical and geometrical properties of the bolt are used to determine the actual bolt preload without calibrating every single bolt. The calibration factors established by laboratory and in situ measurements exhibit rather small scatter. The minimum bolt preload required is achieved with a 95 % probability of being exceeded in a bolted connection on a Dutch highway bridge (Middachterbrug).

The RFCS project SIROCO (2014-17) included research on the further development and optimization of double shear connections with injection bolts to achieve slip- and creep-resistant bolted connections considering various influencing parameters. The type of resin, the curing condition of the resin, the geometrical and mechanical characteristics of the connection and the type of loading were studied. Results showed, for example, that of the five epoxy resins investigated, only RenGel SW404 + HY2404 (Araldite) fulfils the requirements given in Eurocode 3. A bearing stress of 175 MPa is safely allowable in the long-term without exceeding imposed deformation limits.

HV bolts are often used for safe and durable connections in steel structures. However, this well-known and established bolting system has some disadvantages. Those include the scattering of the initial preload by the torque-controlled tightening method and the risk of self-loosening during fatigue loads due to lateral displacement of the components in connections with high loads. In this respect, the lockbolt technology has some advantages regarding the initial preload and loss of preload; both will be discussed in detail in this paper. The technology was invented in the 1940s and is mainly used in automotive, aviation, truck, trailer, rail, bus, agriculture, mining and military applications. Its use in structural steelwork, and especially for slip-resistant connections, has been mainly made possible through individual experimental investigations by users of the technology. Some applications call for its use in slip-resistant connections according to EN 1090-2 and Eurocode 3, e.g. the wind industry for new tower concepts with higher hub heights, and steel girder bridges. These connections can be subjected to fatigue and/or significant load reversal. The load-bearing capacity (or slip resistance) of a slip-resistant connection is mainly determined by the level of preload in the bolt and the coating system applied to the faying surfaces. However, the preload is determined by the type of bolt, and lockbolts can be used as an alternative bolting system. This paper describes a comparative study of HV bolts and lockbolts regarding their use in slip-resistant connections for steel structures. The design and execution of lockbolts will be presented. Investigations will be presented which compare HV bolts and lockbolts regarding the assembly preload, the slip resistance by performing slip load tests and the long-term behaviour with respect to loss of preload for maintenance-free connections. Furthermore, there is a discussion of the results of an online monitoring system for measuring the preload in HV bolts and Bobtail lockbolts in an alternative tower for wind turbines with the use of slip-resistant connections.

Stainless steel material is a suitable choice for modern steel constructions as it has a high resistance to corrosion combined with high material strength and ductility. Furthermore, its use leads to significant reductions in maintenance. In this frame, bolted connections made of stainless steel components become more and more important to enhance the application of stainless steel not only to small parts of steel structures but also to complex structures. Whereas non preloaded stainless steel bolted connections are already widely used, according to EN 1090-2, the application of preloaded stainless steel bolting assemblies is not allowed unless otherwise specified. If they shall be used, they shall be treated as special fasteners and a procedure test is mandatory. Also EN 1993-1-4 requires that their acceptability in a particular application has to be demonstrated from test results. These restrictions are mainly caused by two facts: firstly, the viscoplastic deformation behaviour of stainless steel which might result in not negligible preload losses in the bolting assemblies themselves and secondly, the gap of knowledge regarding suitable tightening parameters and procedures for stainless steel bolting assemblies to secure a required preload in the bolting assemblies and to avoid galling. To solve these questions, research activities have been carried out in the frame of the European RFCS-research project “Execution and reliability of slip resistant connections for steel structures using CS and SS” SIROCO. The present contribution gives an initial insight into the viscoplastic deformation behaviour of stainless steel bolting assemblies which were achieved in SIROCO which shows that preloaded bolted stainless steel connections can be treated similar to those made of carbon steel.