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Wind from all directions Wind loads on membrane structures are not regulated by standards. The variety of shapes of the typically open and thus flow‐exposed surfaces on both sides cannot be captured using geometric variables in tables, as is common for typical building forms in Eurocode EN 1991‐1‐4. The recommended individual wind tunnel tests are only feasible for larger projects with the corresponding budgets and planning periods. Therefore, some recommendations for typical membrane roofs have been collected in the literature, and at the same time, computer‐based wind simulations have developed to the extent that they are now also offered in market‐standard FEM software packages. This paper aims to explain the accuracy and comparability of the various approaches using case studies. The paper presents the analysis of standard approaches, literature values, wind tunnel tests, and computer‐based methods with a comparison of calculation results and provides insights into the development of load assumptions in membrane construction. [ABSTRACT FROM AUTHOR]

FE‐based design of crane girders – application of the rules in prEN 1993‐1‐14 The economic and safe design and verification of crane runway girders poses significant challenges in industrial steel construction. Using a specific example of crane runway girder, this paper compares the conventional analytical verification with a Finite Element Method (FEM) based design acc. to prEN 1993‐1‐14. The new standard prEN 1993‐1‐14, which is currently in the draft stage and regulates the FEM‐based design of steel structures, promises a more efficient and accurate determination of the load‐bearing behaviour of crane runways through direct simulation of more complex structures and load conditions. The system considered in the example corresponds to a single‐span crane runway girder with a span of 10.0 m and a welded cross‐section. Design checks include the verification against lateral‐torsional buckling and web buckling. Insights into the accuracy, efficiency, and applicability of FEM‐based analysis for crane runway design are provided in this paper. [ABSTRACT FROM AUTHOR]

Welds of ultra‐high strength steels and their post‐weld treatment for increasing the fatigue strength Whenever even higher‐strength steels were developed, there were doubts about their cost‐effectiveness and usability. However, the development from S355 to S460 and finally to S700 has shown that this innovation paid off in a very short time. In terms of sustainability, the use of ultra‐high strength steel up to S960 can save resources, make connections more efficient and extend the service life of bridges. These aspects can be realised through the use of ultra‐high strength steel, and the extension of the scope from S700 to S960 in prEN 1993‐1‐12 forms a basis for this. At the same time, further investigations are required, such as the adaptation of the design rules for welding and for the use of post‐weld treatment to increase the fatigue strength. This paper presents results from two current AiF FOSTA projects. As part of the research project "Effective design concepts for mixed connections in steel structures", this paper presents extensive investigations on butt and fillet welded joints of ultra‐high strength steels S960. As part of the research project "FAT‐classification of HFMI‐treated ultra‐high strength structural steels considering geometric manufacturing imperfections in steel construction", this paper presents results and a proposal for extending the DASt guideline 026 and the new Annex F in prEN 1993‐1‐9 to ultra‐high strength steels up to S960 for the constructional detail transverse stiffener. [ABSTRACT FROM AUTHOR]

Translation abstract Linking nano with macro – opportunities for steel constructionNanostructured metallic multilayers have significantly higher strength, fatigue resistance and ductility than monolithic homogeneous metal cross sections. The superior structural properties of these nanostructured cross sections are known, and so it is surprising why no attempt has been made to date to use nanostructured cross sections in macro cross sections in structural engineering to improve the cross section properties. This paper links the advantages of nanostructured multilayers with the needs of homogeneous metallic macro‐cross sections and examines the question of the extent to which the high‐performance material nanolaminate can compensate for the structural weak points of metallic infrastructure. The following weak points of metallic infrastructure are addressed: 1) the welded connection subjected to fatigue and corrosion, 2) additively printed metallic cross sections exposed to fatigue and corrosion. The article provides food for thought on how nanostructured multilayer can potentially contribute to the future of steel construction. As an example, the design and maintenance of cyclically loaded metallic infrastructure structures, such as bridges and offshore wind turbines, are discussed and it is shown how sustainability, resource conservation, reduction of the CO2 footprint, availability, security of supply and economic viability of steel infrastructure structures can potentially be achieved. [ABSTRACT FROM AUTHOR]

Load‐bearing and fatigue behaviour of butt welds in plates of different thicknesses The cross‐section of long‐span steel structures is usually adapted to the bending moment distribution. For this purpose, a thickness transition is applied in the area of butt‐welded joints in flanges of I‐shaped beam members. The fatigue behaviour of these constructional details is complex and differs from a butt‐welded joint in steel plates of the same thickness. This paper presents the results of 30 notch detail tests and compares the behaviour of butt‐welded joints in plates with a thickness transition with those of the same thickness. The statistical analysis of the experimental studies shows a higher fatigue resistance for butt‐welded joints with a thickness transition compared to butt welds of plates of the same thickness. The classification of the latter constructional detail in detail category 90 acc. to FprEN1993‐1‐9:2024 can be confirmed. The prognosis of the notch detail tests with the Two‐Stage‐Model confirms its applicability for the analytical‐numerical prediction of the service life of complex welded constructional details. In addition, the application of the model proves the influence of the thickness ratio and stress ratio on the service life of butt‐welded joints with thickness transition. [ABSTRACT FROM AUTHOR]

Structural stability tests on two‐span channel members in bending, axial compression and torsion The use of slender steel members promotes the competitiveness of steel structures in structural engineering. However, these members often necessitate stability verifications. Global research activities in this field have so far mainly focussed on single‐span members with doubly symmetric cross‐sections. For mono‐symmetric sections such as channels, only a few design models exist based on experimental evidence. Moreover, the potential of structural systems such as multi‐span members is yet not entirely exploited in the normative verification models. Therefore, this paper presents a comprehensive experimental study on the stability behaviour of two‐span members with steel channels under combined loading. Five‐point bending tests were conducted to determine the load‐bearing capacities and to experimentally analyse the influence of the constructional detail of the central support, the axial load, the slenderness ratio and other parameters on the load‐bearing behaviour. The article provides the scientific basis for extending the scope of the stability verification for members subjected to bending, axial compression and torsion in Annex C.2 of the novel EN 1993‐1‐1:2022 to two‐span channel members. [ABSTRACT FROM AUTHOR]

The way to Construction 4.0 in the production and construction of infrastructure projects The construction industry is facing profound changes. Among other things, the requirement of implementing a more sustainable building culture, the increasing shortage of skilled workers and the rising demand for infrastructure construction projects, are challenges of today. Indeed, the industry will not succeed in solving these challenges with the procedures and processes that have been practised for decades. Therefore, it is important to prepare the construction industry for the implementation of Construction 4.0. This paper explains what is behind the term Construction 4.0 and what difficulties currently exist in its implementation. Based on this, recommendations, measures and initial approaches for implementing are presented. Thereby, the paper focus on the production and construction phase of infrastructure projects, which is important for construction companies. [ABSTRACT FROM AUTHOR]

Load‐bearing capacity tests on large scale test specimens for modular polygon tower sections of wind turbines The verification for stability and fatigue of steel towers for onshore wind‐turbines require large dimensions due to the high static and dynamic loads. Since, the rated power as well as the hub height will further increase for wind turbines in the future, also the dimensions of the tower must be increased. Some kind of turbines will require a tower base diameter of > 4.5 m. Tubular steel sections with this dimensions cannot be transported (economically) by road. Therefore modular construction methods have been developed, whereby the tubular steel sections consist of longitudinally divided segments, which will finally assembled on site. Furthermore, the detail design of the connections between the structural components is also a challenge when planning wind turbines for the next generation. As a technical alternative to the existing tower configurations, a concept for a modular polygon tower made of steel is presented, where single plate segments can be connected along the longitudinal edges using extruded profiles so that no further bolted or welded connections are required for the final assembly on site. This technical proposal allows a longitudinal manufacturing of tower segments with steel plates but without any formwork with rolling and bending machines. As part of a research project, the technical feasibility of a modular polygon tower for a hub height of 200 m and a wind turbine class with 10 MW rated power was analysed to offer technical solutions for the next generation of onshore wind turbines. Load cases were generated for a fictitious reference wind turbine to carry out a pre‐design for the tower sections. A test programme was created on the basis of the calculated tower dimensions and ultimate load bearing tests were carried out on test specimens at a scale of 1 : 10. This paper presents the results of the experimental investigations, comparing the load‐bearing capacity of the various tower configurations and the observed failure mechanisms are explained. [ABSTRACT FROM AUTHOR]

Fire risk analysis of electric vehicles and internal combustion vehicles in open car parks: part 2: fire safety and reliability analysis In order to counteract climate change, it is necessary to switch from vehicles with combustion engines to electric vehicles. Consequently, an increasing number of electric vehicles can be observed in Germany. In this context, the question arises whether and if how this development influences the fire risks in open car parks. Answers to this question are the subject of a research project under the leadership of the Institute of Steel Construction of Leibniz University Hannover in cooperation with the iBMB, Division of Fire Safety, of TU Braunschweig. In particular, the project is investigating the influence of a fire scenarios with electric vehicles compared to vehicles with combustion engines on the load‐bearing behaviour structure of an open car park. In this paper, the methodological approach to evaluate the fire risk based on a reliability analysis for the load‐bearing structure of these car parks is explained. By means of the reliability analysis, the fire risk assessment procedure is illustrated for the composite beam using exemplary fire scenarios. As a result, it can be concluded from the fire risk analysis that fire scenarios with electric vehicles do not have a higher fire risk than conventional vehicles with combustion engines and fulfil the required safety level. [ABSTRACT FROM AUTHOR]

Machine learning for design and analysis of steel frame halls The use of digital tools in design and construction processes increases efficiency, especially for recurring tasks and processes, such as the dimensioning of components or structures, which follow similar patterns. This paper develops an artificial intelligence (AI)‐based assistant for use in the pre‐design and design of steel frame halls as a prototypical co‐pilot. For this purpose, the necessary database of steel frame halls is first compiled from project archives of TRAGRAUM Partnerschaft Beratender Ingenieure mbB. This will be examined in the context of data analyses according to the decisive description parameters and similarities, so that finally suitable AI surrogate models for the prediction of the hall parameters are trained by means of regression analyses. Furthermore, an interface to the finite element program SOFiSTiK is implemented, which passes the predictions of the AI regarding the parameters of the steel frame halls to a parameterized input file and triggers the calculation and design. In the course of the calibration of the AI substitute models, in addition to the approximation qualities, possible safety margins to be provided are also discussed in the context of this article. This article shows that the prototypical co‐pilot for the preliminary design of steel frame halls could be successfully implemented. Furthermore the AI newly generated hall frames can be classified as stable with respect to the validation considerations. An outlook on future further developments of this approach as well as the transfer to other applications complete this paper. [ABSTRACT FROM AUTHOR]

Numerical investigations as part of the assessment of the historic bearings of the Chemnitz viaduct As part of the refurbishment of the Chemnitz viaduct in line with monument protection requirements, the cast steel bearing components also had to be assessed. This required extensive numerical calculations in order to carry out the verifications in the ultimate limit state and the serviceability limit state. The results of the finite element calculations, taking into account the exceptional combination of actions and unit load cases, served as input parameters for fracture mechanical investigations to assess the risk of brittle fracture and to verify safety against fatigue. Non‐destructive and destructive tests as well as casting simulations and 3D scans completed the state assessment and thus the overall assessment of the cast bearings. Complex load conditions, such as impressed stress conditions from initial plasticization, were taken into account by means of non‐linear calculations with loading, unloading and reloading. The numerical calculations are presented in this article, in addition to the explanations regarding the other components of the assessment in the first part of this paper, and exemplary results are shown. The detailed recalculation was an important basis for the continued use of a large part of the bearing components. [ABSTRACT FROM AUTHOR]

Assessment of the historic bearings of the Chemnitz viaduct The Chemnitz viaduct was built at the beginning of the 20th century and has been refurbished in recent years in line with its listed status. This required, among other things, an assessment of the reuse of the bearings consisting of individual cast components. The assessment included standard non‐destructive and destructive testing as well as numerical calculations to verify the load‐bearing capacity. As a novel addition, casting simulations, 3D scans of the bearings to record the actual condition and fracture mechanical investigations to assess the risk of brittle fracture and possible crack propagation were carried out. Among other things, difficult accessibility and complex load conditions posed a challenge. This paper presents the bearing concept and the methodology of the assessment and describes the individual components with the associated results. The extensive assessment allowed for the continued use of most of the bearing components. [ABSTRACT FROM AUTHOR]

Bath galvanized substructures for rear‐ventilated façades – part 2 The rear‐ventilated façade is a proven façade construction in modern architecture, which has advantages in terms of building physics due to the technical separation of weathering and thermal protection, combined with excellent properties for dismantling and recycling. Thermal bridges, which are formed by the brackets in insulation layer, have a disadvantageous effect on energy savings. The reduction of heat losses of rear‐ventilated façades depends in particular on the design of brackets, which have already been presented in part 1 of this paper. The numerical simulation of the mechanical and thermal properties for brackets made of hot‐dip galvanised steel in this part 2 of the article show that different requirements result from both fields. With a combined approach that determines the heat losses of façades by required number of brackets for a defined load, basic statements can be made for the most favourable design. [ABSTRACT FROM AUTHOR]

Evaluation of the preload‐time behaviour of slip‐resistant preloaded connections in tower structures for wind turbines In addition to the coefficient of friction, the bolt preload and its preservation have a significant influence on the load‐bearing capacity of slip‐resistant preloaded connections. For cyclically loaded steel structures such as wind turbine towers, mechanically low maintenance or maintenance free bolted connections are of particular interest. The design of mechanically maintenance free connections requires knowledge of the preload losses occuring over the service life of the structure, since these losses must be taken into account already in the design. In steel construction, however, the mechanically joined parts are often coated for corrosion protection. Therefore, a test‐based determination of the preload losses is often necessary instead of an analytical calculation. Scope and expense of corresponding laboratory or field tests can be reduced using existing experience. This paper therefore discusses laboratory investigations based on IEC guideline 61400‐6, in which the sensitivity of preload losses to relevant influencing variables was systematically evaluated for the first time. In addition to long‐term embedding tests, tests under cyclic loads were carried out, which were derived from load situations typical for wind turbines. [ABSTRACT FROM AUTHOR]

A design proposal for polygonal endplates in circular hollow section members in tension Hollow section members under tensile load are usually connected by round end plates. Polygonal end plates with 4, 6, 8, 12 corners and bolts are an easy‐to‐manufacture alternative. The so‐called T‐stub model of EN 1993‐1‐8 can be used for designing such connections. However, the standard does not specify the required effective lengths of the yield‐lines. Therefore, the ultimate loads and the kinematic failure mechanisms of such connections were determined within this Paper by using the Discontinuity Layout Optimization (DLO) method. The mechanisms were analytically described, and the effective lengths of the yield‐lines were presented in the form of a practical design model. A comparison of the design proposal with the ultimate loads of the DLO method shows a good agreement with some deviations of a maximum of 10 % to the unsafe side. [ABSTRACT FROM AUTHOR]

Architectural building envelopes made of metal – optimized forming of double‐curved components The teaching and research unit "Sustainable Metal Building Envelopes" at RWTH Aachen University conducts research on lightweight building envelopes made of metal and develops processes for planning and manufacturing of components for bespoke designs and built structures. Double curved facades and roofs pose a particular challenge for architecture, civil engineering, fabrication and construction. In this paper, the improved shaping of double‐curved metal components for building construction applications is presented, which was developed within the framework of a collaborative research project. The interaction of the forming processes as well as the simulation of shape formation and approaches to optimizing the process are discussed. In an introduction, various shaping processes for three‐dimensionally curved building components are examined. [ABSTRACT FROM AUTHOR]

Tests on sandwich façades as a basis for seismic design As part of an ongoing research project, the performance of lightweight metal façade elements under in‐plane loading was investigated to assess their cyclic behavior, dissipation capacity and functionality during seismic events. As preliminary investigations showed, metal wall and roof elements contribute to the stiffening of the overall structure, and thus to the change of the eigen period compared to the primary structure, which can lead to increased seismic loads to be applied acc. to the response spectrum method. Based on this, a new behavior‐based approach considering the contribution of lightweight metal building envelopes can be developed to determine the improved resilience of structures and the effect of a damaging earthquake on the building envelope performance. This paper includes: (i) a brief state of the art, (ii) a presentation of the research project, (iii) the experimental program, (iv) the detailed experimental setup, (v) the system response under monotonic and cyclic loading, (vi) the main results, (vii) an overview of the numerical investigations and ongoing and future research activities. [ABSTRACT FROM AUTHOR]

ÖBB trough bridges with UHPFRC‐composite slab In the railway system of the Austrian Railway Association there are a lot of single span steel bridges with short span (<20 m) and without ballast bed. One of these bridges was the Auenbachbrücke, situated on the railway track Zeltweg–St. Paul in the Lavanttal (Kärnten, Austria), which should be replaced by a modern bridge structure with ballast bed. The main task in the design of the bridge construction was to maintain the existing top of the rails as well as the bottom height of the construction due to flood prevention issues. This task could be solved by using a steel trough bridge with transversal orientated UHPFRC‐composite slab, as shear connection crown dowels were used. In the present paper, the bridge construction is presented and the statically calculation as well as the corresponding testing are introduced. [ABSTRACT FROM AUTHOR]

Design of clamped crane rails with foot flange (type A) The interface between crane (mechanical engineering) and crane runway girder (civil engineering), which is not explicitly defined, has repeatedly led to misunderstandings in practice in the past. Only the contact pressure between the wheel of the crane and the rail surface is verified by the crane designer acc. to EN 13001‐3‐3. The design of the crane rail itself is not covered by the crane design standards. On the other hand, the design of clamped rails acc. to EN 1993‐6, that are subject of biaxial bending and torsion as a result of eccentric load introduction, has not been possible up to now because of missing design recommendations. This paper presents the current status of the design rules developed for the draft standard prEN 1993‐6 and presents comparisons with realistic numerical investigations. In addition, an improved calculation model for the longitudinal stresses from concentric wheel loading is presented that is able to describe the actual load‐bearing behaviour significantly more accurate in comparison to draft standard prEN 1993‐6. Furthermore, a recommendation for a fatigue verification is formulated. [ABSTRACT FROM AUTHOR]

Grain size development of high‐strength steels after cold forming and heat treatment The risk of embrittlement of steels during welding in cold‐formed areas leads to many production restrictions or high production costs. The reason for embrittlement is the coarse grain formation in the recrystallization zone. In this paper, three high‐strength steels were investigated with respect to their tendency to embrittlement at different degrees of deformation over a temperature spectrum. The aim was to simulate the temperatures during welding in the recrystallization zone and thus to estimate the grain growth. For this purpose, the materials were elongated to maximum elongations up to just before the uniform elongation. The subsequent heat treatment was carried out between 500 °C and 800 °C with different holding times. Over the entire series of tests, no significant correlation was found between grain growth, the degree of deformation, the annealing time and annealing temperature. The results indicate that the critical degree of deformation cannot be reached during the elongation of high‐strength steels, and thus no coarse grain formation takes place in the recrystallization zone. [ABSTRACT FROM AUTHOR]

Dimensioning tools for stiffened and unstiffened buckling plates according to DIN EN 1993‐1‐5 – part 1: unstiffened buckling plates In Germany, stiffened buckling plates in bridge construction must be verified using the reduced stress method (MRS) according to DIN EN 1993‐1‐5. Unstiffened buckling panels, on the other hand, may be verified either according to the method of effective widths or according to the method of reduced stresses. To shorten the time‐consuming verification of the standardised verification formats for pre‐dimensioning, which is particularly prevalent for stiffened buckling fields, part 1 of this paper develops and presents diagrams for unstiffened buckling fields based on the MRS by reformulating the buckling verification, which enable fast pre‐dimensioning. With the diagrams, the dimensioning of plate thicknesses or stiffener spacings can be carried out in a few simple and comprehensible steps. The diagrams are selected based on the geometry parameters a, b and t or the applicable boundary conditions. For stiffened buckling panels, the maximum permissible distances of the longitudinal stiffeners or the required main plate thickness can be determined. In the second part of this paper, diagrams for the dimensioning of longitudinal stiffeners via the determination of minimum stiffnesses are presented. The minimum stiffnesses are derived from the geometry of the linear buckling shapes of simply stiffened buckling fields. [ABSTRACT FROM AUTHOR]

On fatigue strength of large‐size bolt‐assemblies in steel constructions under consideration of manufacturing and surface condition related impacts – part 2: evaluation of fatigue tests Manufacturing related impact factor significantly affect the fatigue strength of bolt assemblies used in steel constructions. The effects are taken into account very inconsistently in the design bases, depending on the normative reference used. Especially for bolt assemblies with large diameters, as they are commonly applied in large numbers at towers for wind energy plants, only a very limited experimental background for assessment of relevant impact factors has been available in the past. This paper presents and evaluates results from 20 different fatigue test series, most of them conducted in the recent past on three different high‐strength bolt assembly systems with varying manufacturing conditions. The data base covers a diameter range between M12 and M64 and focuses on test series with high mean stress in a representative order of magnitude for practical application of the bolts. Based on the knowledge given in the relevant literature, the test results are evaluated regarding the impact of different manufacturing related effects. Furthermore, the results are compared to the specifications of the relevant international normative guidelines. In addition to the results of fatigue tests, supplementary metallographic examinations of the fracture surface shape and surface‐layer condition behavior are taken into account. On this basis, the paper derives recommendations for future design considerations and gives an outlook on further expedient investigations. [ABSTRACT FROM AUTHOR]

On fatigue strength of large‐size bolt‐assemblies in steel constructions under consideration of manufacturing and surface condition related impacts – part 1: state of knowledge Manufacturing related impact factors significantly affect the fatigue strength of bolt assemblies used in steel constructions. The effects are taken into account very inconsistently in the design bases, depending on the normative reference used. Especially for bolt assemblies with large diameters, as they are commonly applied in large numbers at towers for wind energy plants, only a very limited experimental background for assessment of relevant impact factors has been available in the past. Part 1 of this paper presents the state of knowledge regarding the decisive influencing variables on the fatigue strength of bolts in steel structures. From this state of knowledge, the authors derive the basis for evaluating existing and (242) previously unpublished results from fatigue tests on axially loaded bolt nut connections up to nominal size M64, which are included in Part 2 of this paper. The focus is on the influence of size and surface layers, the influence of thread fabrication as well as the stress condition from the pulling assembly practice. [ABSTRACT FROM AUTHOR]

Durability and robustness of bolted joints for crane runway beams The paper deals with selected topics related to bolted connections in crane runway girders. First, the behaviour of the connection during tightening and under external loading is described. The significance of the preload for the bolted connection is discussed. The mechanisms underlying losses of preload and securing methods to counteract them are introduced. Subsequently, these securing methods are linked to typical crane runway connections. The paper concludes with considerations for the inspection of the connections in the event of installation and operation of the crane system. [ABSTRACT FROM AUTHOR]

Application of BIM in the context of Construction 4.0 in the Oberbürgermeister‐Karl‐Lehr bridge project The construction industry is facing new demands, such as the creation of a more sustainable building culture and the necessary increase in efficiency. These challenges can only be solved with the help of modern planning and construction methods such as Building Information Modelling, which opens the way to Building 4.0. Due to the increasing requirements for implementing the BIM method in infrastructure projects, it is important for companies to build up experience. For this reason, the Max Bögl Group decided to use the BIM method in the production and construction phase of the Oberbürgermeister‐Karl‐Lehr bridge project. In addition to an overview of the project, this paper provides a summary of the BIM methods used and the lessons learned. [ABSTRACT FROM AUTHOR]

Reinforcement of the Rhine bridge Maxau – accompanying measurements, effects and efficacy Due to the steadily increasing traffic volume, fatigue damages occurred on the orthotropic steel deck of the Maxau Rhine Bridge, necessitating a deck reinforcement. In order to reinforce the bridge for traffic loads in future, a layer of high‐strength concrete (HPC) was applied on the orthotropic deck plate. A team of engineers from the Karlsruhe Institute of Technology (KIT) conducted measurements during the reinforcement project. This paper presents the corresponding measurement results, discusses the effects achieved by the reinforcement project, and draws conclusions on its effectiveness. Numerical analyses indicate a decrease in fatigue loads on the orthotropic steel deck, confirming an improved load distribution, which was also determined by the measurements. [ABSTRACT FROM AUTHOR]

Fast‐charging station Leipzig – the floating roof on a computer‐generated endless support For a fast‐charging station at the production site of a sports car manufacturer, a roof was to be developed that would transport the image of the brand in addition to I function as weather protection. The existing technical infrastructure, i. e., power lines that could not be built over and movement and maintenance spaces for the charging columns, only allowed for a few and, above all, irregular support points and support positions. The design process results in a seemingly floating roof whose cladding is modelled on an aerofoil supported on a single endless column. The infinite support Spline, iconographically analogous to an initially simple appearing bent‐up paper clip, ensures both the clamping of the cantilevered roof and the global reinforcement through the spatial support positions and inclinations. The geometry was developed using an evolutionary optimisation algorithm with the most outstanding efficiency while complying with the given geometric restrictions. Within the parametric structural model, in addition to the control and analysis of the static performance, the geometric implementation of the milled circular arcs at the head and foot points was also carried out. The entire process, from the development and variant study to the analysis and documentation to the production, thus took place in a closed digital process chain. Therefore, it was possible to achieve the design goal of contrasting a flat roof and a filigree support structure. [ABSTRACT FROM AUTHOR]

Fire testing of loaded carbon tension members The application of carbon tension members is motivated by extraordinary well fatigue behaviour and high tensile strength of the material. Compared to steel, cross sections can be reduced. Steel tension members used for network arch bridges shall be replaced in perspective. The loadbearing behaviour of carbon tension members in case of fire is still unknown. Therefore, fire tests were performed to investigate the failure mechanisms. Based on the derived test data the comparability to conventional steel tension members was estimated. This paper describes real scale fire testing of mechanically loaded carbon tension members, carried out as a part of the joint research project NeZuCa. The test setup consisted of four carbon tension members with circular cross sections and diameters of 36 mm and 51 mm. In absence of a prescriptive fire scenario for the application case intended in the research project and to ensure comparability, a fire exposure according to standard temperature/time curve was chosen. The elongation of the tension members as well as the temperatures of the specimen and the furnace were recorded. [ABSTRACT FROM AUTHOR]

Lateral torsional buckling of girders with rotational restraints – influence and application of the new rules in prEN1993‐1‐1:2020 This paper presents the results of a study that investigated the effects of the innovations introduced in the draft standard for the 2nd generation of EN 1993‐1‐1 for the lateral‐torsional buckling (LTB) verification of beams with I and H cross‐sections on the regulations for the calculation of the minimum stiffness of a rotational restraint to avoid LTB. In the first part of the paper, the background of the existing and new regulations is discussed together with previous proposals for adapting the definition of the minimum rotation bedding. Then, based on theoretical considerations and numerical calculations of the realistic load‐bearing capacity of rotationally restrained beams, it is shown that the new regulations for LTB in prEN1993‐1‐1 lead to very precise predictions of the load‐bearing capacity of rotationally restrained girders and beams, provided that rotational stiffness is also taken into account in the determination of the corresponding slenderness for LTB. In addition, it is shown that the currently valid specifications for the minimum rotational stiffness contained in the National Annex of DIN EN 1993‐1‐1 are also sufficiently accurate for practical use and do not contradict the newly introduced regulations for torsional buckling. The planned tightening of the regulations on the minimum rotational stiffness in prEN 1993‐1‐1, Annex D are thus shown to be unnecessary. [ABSTRACT FROM AUTHOR]

Modified notch functions for a welded detail of a through‐bridge In a previous paper, the notch tension concept was presented as an appropriate tool for the fatigue verification of a welded detail occurring in single‐track railway through bridge with a 120 mm thick steel deck‐plate. The basics for the computation of the notch stresses using a finite element program were argued and the merging of single results to functions was described. To illustrate the procedure, the notch function was derived in detail for one of nine critical spots (six at the upper weld, three at the lower weld). In this paper, the remaining notch functions for the upper weld are derived considering the interaction of sectional forces. The practical application of the derived formulae is explained by a numerical example. Controlling item for the welds is the fatigue verification for the longitudinal carrying action. Finally, hints referring to the throat depths are given. [ABSTRACT FROM AUTHOR]

Eigenshape based imperfection method for beam‐columns with mono‐symmetric I‐sections This paper shows for the first time the application of the Overall Imperfection Method (OIM) for columns, beams and beam‐columns with mono‐symmetric I cross‐section. The buckling failure mode of compressed members with mono‐symmetric I‐section is torsional‐flexural like. The second‐order effect from the rotation around the longitudinal shear axis during the loss of stability is taken into account when the amplitude of the initial imperfection is calculated for the compressed members. For beams, the buckling behaviour is also different from doubly symmetric cross‐section because the shear centre and the centre of gravity of the cross‐section do not meet at the same position. This paper shows the extension and the usability of the OIM for steel structures with mono‐symmetric I‐section. The automatic determination of the equivalent amplitudes for columns, beams and beam‐columns are presented for the first time. The practicality of the proposed method is demonstrated for single and multi‐span members with three examples. [ABSTRACT FROM AUTHOR]

Reasonable periods of inspection for crack detection on historical riveted railway bridges based on fracture mechanics – part 2 An assessment of the remaining fatigue life based on SN‐curves often leads to conservative and imponderable results, because of the high effect of the fatigue damage in the past with minor knowledge of the associated service trains. For a representative single span truss bridge an alternative assessment based on fracture mechanics was done, with calibrated models based on fatigue tests on dismounted historical girders and stress spectra based on numerical simulations of the crossing of the individual service trains. This was the content of part 1 of this paper. Based on the assumption of a starting crack length detectable at regular inspections, remaining fatigue life are calculated for the individual bridge members, leading to a proposal of accurate time periods for inspection. This topic is the content of this part 2 of the paper, including also comprehensive parameter variations to allow a generalization for other historical riveted railway bridges. [ABSTRACT FROM AUTHOR]

Reasonable periods of inspection for crack detection on historical riveted railway bridges based on fracture mechanics – part 1 An assessment of the remaining fatigue life based on SN‐curves often leads to conservative and imponderable results, because of the high effect of the fatigue damage in the past with minor knowledge of the associated service trains. For a representative single span truss bridge an alternative assessment based on fracture mechanics was done, with calibrated models based on fatigue tests on dismounted historical girders and stress spectra based on numerical simulations of the crossing of the individual service trains. This is the content of part 1 of the paper. Based on the assumption of a starting crack length detectable at regular inspections, remaining fatigue life are calculated for the individual bridge members, leading to a proposal of accurate time periods for inspection. This is the content of part 2 of the paper. [ABSTRACT FROM AUTHOR]

Investigation of an engineering model for the assessment of the seismic behaviour of large mobile equipment For large mobile equipment in seismically active regions, seismic stability is an essential and often decisive design criterion. The seismic behaviour of such large equipment is usually characterised by complex nonlinear types of behaviour (uplift, tilting and rocking), which are difficult to compute and analyse in practice. In this paper, a highly simplified engineering model is presented or developed step by step, which should be able to represent basic features of the typical behaviour of large mobile equipment transverse to the rail under seismic excitation. The typical rocking motion of the equipment, as determined in previous analyses, is to be reflected in the simplified model. The engineering model will be designed in such a way that it is able to reproduce qualitative statements about uplift and rocking or tilting as a function of incisive model parameters and seismic excitation. The dissipation mechanisms of the model are presented and seismic tilting spectra are generated using different approaches. The suitability and applicability of these approaches for assessing uplift and rocking tendencies for large mobile equipment is reviewed using representative series of bucket wheel machines and stackers as examples. In addition, parameters are determined for quantitative application to further large mobile equipment and the delimitation criteria of qualitative and quantitative applicability are compiled. [ABSTRACT FROM AUTHOR]

Material properties of historical steels from exhibition hall 12 in Leipzig at elevated temperatures This paper describes material investigations on historic steel structures. In the course of the reconstruction of the exhibition hall 12 in Leipzig, parts of the original load‐bearing structure are to be restored and integrated into the new building. In order to verify the resistance of the structure, material tests were carried out on the steels and the riveted joints both under ambient temperature and at elevated temperatures. In analogy to the regulations of Eurocode 3, calculation values for the verification were derived from the test results. [ABSTRACT FROM AUTHOR]

Damage equivalence factors for deck slabs of steel railway bridges According to EN 1993‐2, the fatigue verification of railway bridges can be based on internal forces due to the standard load model 71. These internal forces are to be multiplied by a dynamic coefficient Φ2 and a damage equivalence factor λ. In this paper, factors λ1 allowing for the damage effect of traffic on quadrilaterally supported plates with torsionally flexible supports at the longitudinal edges as encountered in single‐track railway‐brides in a span range between 10.0 and 27.5 m are derived for three standard traffic situations. The required damage equivalence factors λ are obtained from the factors λ1, considering the annual traffic volume and the requested service life. [ABSTRACT FROM AUTHOR]

3DWelding – additive fabrication of structural steel elements This paper investigates the possibilities of robotic 3D printing with steel (WAAM – Wire and Arc Additive Manufacturing) in the construction industry. The aim of the project team is to develop a stable and economical manufacturing process for customized steel elements. Thus, the influence of different process parameters such as wire feed rate and travel speed on the weld shape and build‐up rate as well as on the material properties will be explained and a parameter window with stable, verified parameter sets will be defined for each material used. Three different filler metals (G 2Si1, G 3Si1, G 4Si1) are tested in terms of their strength and stiffness, with particular attention paid to the joining area between substrate and welded structure. For this purpose, test methods for testing additively manufactured components, especially for shear capacity, have been newly developed. As a proof of concept, an exemplary application is shown and the load‐bearing capacity of this connection is investigated in different configurations. [ABSTRACT FROM AUTHOR]

Unexpected fatigue cracks at main girders of a railway bridge – strain measurements under service and analyses based on fracture mechanics At a steel railway bridge, erected and taken into service in 1960, fatigue cracks were detected at some transverse stiffener to web connections at the lower flange of the main girder. These findings were surprising, because this specific connection detail was suggested in previous national design standards for fatigue. The paper presents the comprehensive strain measurements under service to show the local stress field at the critical detail within the web plate of the main girder, indicating the well‐known phenomenon of distortion‐induced fatigue, but with unexpectedly high resonance‐like bending stresses in the web. Based on fracture mechanics analyses, with implementation of the measured strain/stress data due to local and global effects at the transverse stiffener connection, as well as the measured material properties (fracture toughness and crack growth parameters) the remaining fatigue life was analysed. The positive results allow an unrestricted train operation in the future. It also turned out, that the mixed‐mode effects must be taken into account and considering only mode I at the crack tip may lead to unsafe results. [ABSTRACT FROM AUTHOR]

Sandwich panels with a core of corrugated cardboard The goal of a research project of the Institute for Steel Construction and Materials Mechanics was to determine the utilization of corrugated cardboard as a core material for sandwich panels for roof and wall cladding. In contrast to common core materials, corrugated cardboard is recyclable and consists of renewable raw materials. The bearing behaviour depends mainly on the paper types and on the orientation of the anisotropic material inside the panel. The weakest orientation has similar stiffness and strength as common core materials. However, these can be exceeded many times by other core orientations. Investigations of the most important building physical parameters have shown that the fire behaviour is slightly better than that of most PU‐sandwich panels. The thermal conductivity in the weakest core orientation is comparable to that of mineral wool, the stronger core orientations show higher thermal conductivity. [ABSTRACT FROM AUTHOR]

Mechanical material behaviour of ultra‐high‐strength structural steel S960QL in case of fire Due to their good strength‐to‐weight ratio, high‐ and ultra‐high‐strength structural steels are increasingly used in multi‐storey and industrial buildings in the form of plate material, pipes and sections. For structures with fire protection requirements, however, the use of high‐strength structural steels is currently inhibited by a lack of knowledge regarding temperature‐ and rate‐dependent material behaviour. Comprehensive knowledge of the material behaviour is a basis for a realistic modeling of the load‐bearing behaviour of steel structures. Within the framework of the FOSTA‐research project P 1502, systematic investigations of the structural material behaviour of ultra‐high‐strength steels are carried out in terms of an extensive tensile test program. The aim of the project is to characterise the mechanical material behaviour during all phases of a fire, including the cooling phase of natural fire scenarios. The paper addresses the material behaviour of quenched and tempered steel S960QL in fire. Steady state and transient state tensile test results are presented and used for the characterisation of the material behaviour during the heating phase of a fire and the comparison to common material models. In addition, the results of natural fire tests for the evaluation of the material behaviour in the cooling phase and the residual behaviour are presented. [ABSTRACT FROM AUTHOR]

Universal high‐performance columns made of high‐strength steels without welding In recent years, steel‐concrete composite columns made of normal‐strength steels are seldom used owing to the economic and technological advantages of precast reinforced concrete columns. Though, the use of high‐strength structural steels bears high potential for the efficient production of composite columns with excellent structural performance that are economically competitive to precast concrete columns, there are currently major obstacles to use of the ultra‐high‐strength steels (UHSS) in Germany. Hollow section composite columns with embedded high strength steel core without welded connections provide an opportunity to regain lost market share. A research project, funded by the AiF (Arbeitsgemeinschaft industrieller Forschungsvereinigungen), is intended to explore the potential of UHSS composite columns by experimental and theoretical investigations. The present paper demonstrates the concept of such composite columns with UHSS and gives first exciting insights into the research results. In addition to column tests under ambient and fire conditions, small scale tests are necessary to investigate various influencing factors and to create the basis for new and easy to use design and construction principles that allow efficient application. [ABSTRACT FROM AUTHOR]

Experimental investigations on the durability of intumescent coatings Intumescent coatings are used in structural fire protection to improve the fire resistance of steel structures. Beside structural fire resistance also aesthetic demands can be fulfilled. The profile‐following application and the low dry film thickness of the products make it possible to maintain the filigree appearance of steel structures. In addition to the thermal protection effect, the durability of the coating must also be ensured. The assessment methods available at European level by EAD 350402‐00‐1106 aim to a service life of ten years. Test methods for a longer period are not described. This paper presents experimental investigations on the influence of weathering on the expansion behaviour, the thermal performance and the reactions taking place during foaming in case of fire. The tests were carried out on a water‐based and an epoxy resin‐based intumescent coating. The research results were obtained in the IGF research project 20470 N. [ABSTRACT FROM AUTHOR]

An online platform for the management of digital visual data for the condition monitoring of protective coatings on marine steel structures The paper presents an online platform for the annotation and management of visual digital data, which allows for the condition monitoring and maintenance modelling of protective coatings of marine steel structures by means of digital image data only. A 10‐step procedure is introduced which includes the data acquisition, transfer of the data into the online platform, the annotation and management of the data by means of special tools and methods, and the modelling for condition monitoring and maintenance purposes. Some special applications of the platform are exemplary illustrated. [ABSTRACT FROM AUTHOR]

Component based finite element design of steel joints This paper describes the principles of multi‐level finite element modelling for design of structural steel joints. The internal part of the design by finite elements is the validation and verification of the model and its results. For models by shell and solid elements is mesh sensitivity study. In component bases finite element design (CBFEB) are the steel plates considered by geometrically and materially non‐linear analysis (GMNA). Its resistance in elastoplastic stage is limited by strains. The behaviour of components, e. g. of bolts, anchor bolts, welds etc., is treated by introducing nonlinear springs representing its behaviour in term of initial stiffness, ultimate resistance and deformation capacity. To show this process a contribution is prepared, which summarises the history of achievements of finite element analyses (FEA) in structural steel connections. This paper shows differences of the research‐oriented and design‐oriented models and the currents trends in modelling of connection components. Both have their roles in advanced analyses. The validation and verification is demonstrated on model of block shear during potential failure mode for gusset plate connection and for the base plates loaded by bending moments to both axes. The summary shows the potential in design of elements including its connection. [ABSTRACT FROM AUTHOR]

The effects of diffraction and multi‐reflection on cylindrical columns The surrounding topology of a column potentially has a significant impact on a blast wave and the following design procedure. Effects like diffraction or multi‐reflection does not seem to be included in design codes or technical literature. This issue shall be addressed within this paper. The paper addresses three main topics. First, the paper answers the question whether the area behind the column is protected, constituting a shadowed area. For the column itself, this is not of significant influence, but shall clarify if the load on a backwards‐placed structure, e. g. a façade, can be determined correctly by using current technical codes. Second, a secondary shock‐front, which originally initiates by diffraction and then distributes diagonally in space, shall be investigated. The correct load assessment on e. g. a second‐row‐column is discussed. Third, directly coupled with the assessment of incident pressure build‐up behind the column due to diffraction is the quantification of pressure increase due to (multi‐)wave reflection at a facade, leading to a significant pressure scale up, which might be relevant for design of column and/or façade. [ABSTRACT FROM AUTHOR]

Design model for headed studs as shear connectors under additional tensile loading Headed studs are primarily subjected to shear when used as shear connectors in usual steel‐concrete composite structures. Consequently, initial design rules for shear connectors in composite structures did not address tensile forces directly. In case of horizontally lying headed studs embedded in a thin concrete slab such as in composite bridges, the headed studs may be subjected to tensile forces. For horizontally lying studs, current design rules consider a possible failure caused by a tensile load due to pull‐out by specifying geometric boundary conditions. As a consequence, relatively long shear connectors are required, which lead to uneconomical or impractical embedment lengths of the shear connectors. As meanwhile European code rules for fasteners under shear and tension (EN 1992‐4) have been developed, the upcoming Eurocode 4 refers to them for the design of shear connectors under combined tension and shear in composite structures. The fastening technology allows a direct design for tensile loading for different failure mechanisms, considering the influence of the reinforcement and concrete strength. Following this idea, this paper presents a design model for shear connectors in steel‐concrete composite structures under additional tensile loading based on experimental and numerical investigations considering recent developments in fastening technology. [ABSTRACT FROM AUTHOR]

Transversal load introduction into unstiffened girder webs – interaction with shear force and bending moment and implementation in new Eurocode version Transversal load introductions into unstiffened girder webs are often used economic solutions in building structures, not directly covered in the current Eurocode. Within this paper an engineering design model, developed at TU Graz, is evaluated for cases with additional high shear forces and bending moments acting at the girder. The resulting load carrying behaviour, in cases of interaction between Fz & Vz & My, is presented, based on comprehensive numerical studies, also for girders which are susceptible to web buckling. Finally, the modified design model is presented, which will be part of the new Eurocode version prEN 1993‐1‐1. In addition, a more general solution is shown, which could also be implemented in the Eurocode in form of a national Annex. [ABSTRACT FROM AUTHOR]

Penstocks with multiple thrust rings – accurate forces at thrust rings due to constraining effects and comparison with a simple design model Thrust rings are a component of penstocks and have to transfer the longitudinal forces of the steel pipe to the surrounding rock mass. Longitudinal forces occur primarily due the pressure loads at valves or at pipe covers. Within this paper, the realistic load bearing behaviour of different penstocks geometries with multiple thrust rings is presented, including constraining effects due to internal pressure and temperature. Results are shown with and without friction effects between steel pipe and surrounding concrete and are based on numerical FE analyses. In addition, a simple 1D beam model (design model), developed by the authors, is presented. The forces at the thrust rings are compared between both models. It is shown that also for different load combinations the simple 1D beam model gives accurate results for practical application. The FE study also shows, that always the load combinations with the constraining effects due to internal pressure and temperature must be analysed – a superposition of the results of the individual load cases leads to misleading results. [ABSTRACT FROM AUTHOR]

Automated post weld treatment for offshore wind turbines A more economical and resource‐saving construction of offshore wind energy converters (OWEC) is necessary in order to implement climate policy objectives. The increase of the fatigue resistance by using high‐strength steels and by applying post‐weld treatment methods offers great potential for reducing the use of materials and costs for monopiles. Specifically, in the automated OWEC manufacturing chain, automated processes such as deep rolling are a suitable option. Deep rolling is an established process in mechanical engineering for increasing the wear and fatigue resistance of metallic components. This paper presents results of deep rolling as a new post treatment method to increase the fatigue strength of welds. The surface and subsurface zone properties of submerged arc welded butt joints made of a structural steel grade S355MLO before and after deep rolling are shown. In order to quantify the influence of deep rolling on the weld geometry, measurements of a laser line sensor are presented. Finally, the results of fatigue tests are discussed, which show the great potential of the deep rolling process as a post weld treatment method. [ABSTRACT FROM AUTHOR]