Search

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]

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]

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]

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]

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]

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]

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]

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]

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]

Abstract: Digital form‐fitting – Cog connections for complex steel structures. This paper discusses the potentials of form‐fit connections in steel structures to generate ‘digital details' which are easily adapted to different boundary conditions and organize their manufacturing and assembly. In this paper, a grid shell for a 45 m span ETFE cushion dome and a large membrane façade that use digital detailing as a basic principle for all joints of the structure, will be discussed. The projects demonstrate how the inclusion of simple digital production processes in the detail design enable rational planning, manufacturing and assembly of complex structures. Next to the new challenge in understanding geometric relationships, material properties, and manufacturing techniques, computationally expensive analysis using Finite Volume Elements with nonlinear connection and material models is necessary to the engineering of such details. [ABSTRACT FROM AUTHOR]

Abstract: Load bearing behaviour of combined steel pile walls under water pressure under the influence of positional imperfections. Increasing global trade leads to a significant expansion and strengthening of seaport facilities and thus to an increasing use of quay walls with combined steel pile walls. Horizontal loads, which mainly come from groundwater pressure, are forwarded by Z‐shaped intermediate piles via special connector profiles to I‐shaped king piles and then directed into the ground. The design of the intermediate piles is regulated in DIN EN 1993‐5. The test‐based method in provides the most accurate and thus most economic results. This paper shows how with this method water pressure resistances were derived for the HZ‐M/AZ‐system [2] in nominal position. However, fabrication influences often lead to deviations from the nominal position, which the intermediate piles have to compensate for. In this paper, the influence of a stretching of a sheet pile wall in the wall direction and thus an increase of the system width is examined. Firstly, the stretch itself is analysed and secondly, the load bearing behaviour of the stretched system is compared to that of the system in the nominal position. [ABSTRACT FROM AUTHOR]

Abstract: Dedicated to Prof. Dr.‐Ing. habil. Joachim Lindner on the occasion of his 80th birthday The aesthetical and structural advantages of tubular structural elements sustained the increase in their use in Brazil in last decades. The joints between tubular members remain a critical issue, with many studies indicating that further research is still needed, particularly for some geometries. In the past, some experiments on the influence of the chord stresses over the brace load capacity were published, but a definitive answer to this design issues was not reached. The first part of this paper presents an experimental evaluation centred on the effect of tension and compression chord stresses over RHS chord to SHS braces T‐joints. The results showed that compressive chord stresses could considerably reduce the joint resistance. In contrast, when tension chord stresses are applied the joint resistance increases but this is still not considered in the design codes. Still considering the tubular joints structural behaviour, there are cases where the ultimate resistance of the tubular joints may be enhanced by using flange plates as reinforcement, instead of replacing the chord or braces with stronger sections. Bearing this scenario in mind, the second part of this paper presents some experimental results of SHS T‐joints reinforced with flange plates to achieve a more economical design. The results showed that the joint resistance could be increased about 88 % using the reinforced plate with the same thickness of the chord profile. [ABSTRACT FROM AUTHOR]

Abstract: Limitations to the use of partial shear connection in composite beams with single flange steel beams and composite dowels – Part 1: Theoretical background, methodology and development of FE‐models. The plastic bending resistance design of composite beams with partial shear connection in EC4 is subject to several limitations of use. For instance, the shear connectors, usually shear studs, have to provide sufficient ductility (at least 6 mm deformation capacity) and the geometry of the steel beam is restricted to sections with either equal flanges or only slightly differing areas of top and bottom flange. Furthermore, EC 4 defines a minimum degree of partial shear connection. For composite members with single flange steel section and composite dowels, limitations to the use partial shear connection have not yet been researched. Because of remarkable differences regarding steel section geometry and deformation behaviour of the connectors a simple transfer of EC 4 rules is not possible and likely non‐conservative. In the first of two companion papers on that topic, the theoretical background and the methodology to investigate the limitations of use for partial shear connection are provided. Besides plastic design of several beams sections with partial shear connection, the paper presents the development of nonlinear, 3D FE‐models of composite beams with single flange steel beam and composite dowels, which are validated against experimental beam tests from the literature. [ABSTRACT FROM AUTHOR]

Abstract: Development of a DASt‐guideline for high frequency mechanical impact treatments – conclusion of investigations and proposal of DASt‐guideline‐draft. Numerous research work in recent years has proven an increase in fatigue strength by using high frequency mechanical impact (HFMI) treatment on welded steel joints. Regardless of the profound research activities in the field of HFMI‐methods at national and international level, the increase in fatigue strength that can be achieved by these methods may not be taken into account for the design of welded structures in Germany until now. Previous use of HFMI‐methods for structural applications is limited to projects in which a technical approval has been obtained for particular cases (ZiE). A DASt‐guideline, which regulates the design of HFMI‐treated structures, will make a decisive contribution regarding structural applications of these methods in future. This paper presents the results of a research project with the objective of developing a design concept for HFMI‐treated welds. This design proposal forms the basis for the forthcoming DASt‐guideline and regulates the classification of fatigue strength for HFMI‐treated welds depending on the stress ratio and the material yield strength according to Eurocode 3, specifying suitable application limits. The developed concept also takes into account the increasing effectiveness of these methods with increasing material strength. [ABSTRACT FROM AUTHOR]

Abstract: Flatness tolerances for bolted steel flanges in wind turbine support structures are a much discussed topic. The tolerances that are currently used in the industry and provided in relevant codes and standards were devised around 10–15 years ago, and their application for the significantly larger dimensions of current towers and flanges is frequently questioned. In this paper, these tolerance requirements are presented together with their historical background, and a methodology for adapting them based on a determination of gap‐closing behaviour is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Emerging offshore wind markets in the East Asian region demand seismic design for offshore wind support structures. This paper analyses site conditions and design methods applicable for jacket designs in earthquake regions. Required seismic standards, guidelines and load cases are described in detail. A design case study identifies the relevance of seismic impact in the design of jacket support structures for offshore wind turbines. In a design case study, jacket structures for a typical North Sea site and East Asian conditions were developed based on a generic 12.5 MW wind turbine. For different methods during the design process (conceptual and detailed design), the resulting ultimate limit state loads at the top and bottom of the jacket are compared. Summarising the case study, the governing design situations are identified, and recommendations for seismic design practice are derived. [ABSTRACT FROM AUTHOR]

Abstract: Transverse butt welds as fatigue critical detail of steel towers and monopiles – Influence of the geometrical notch effect on the fatigue resistance. The large dimensions of wind turbines and their components become more and more challenging for the entire supply chain in the wind industry. An efficient manufacturing of components is of an increasing importance in order to withstand the cost pressure and to be competitive on the international market. Welding is the most common joining technique in heavy steel construction. Newly developed high‐performance welding techniques may contribute to reduce the number of weld passes and by this the manufacturing time. These alternative welds have to show comparable or even better mechanical‐technological properties than the conventionally welded seams. This paper mainly focuses on the evaluation of the fatigue resistance. Samples welded by a newly developed combination of nonvacuum electron beam and submerged arc welding are numerically and experimentally checked against conventionally submerged arc welded samples. Motivated by the question of an optimized fatigue design process as part of a serial production process for tubular tower and monopile, the weld geometry was measured. In order to ensure a wide comparability, measurement standards regarding accuracy and data processing were defined. The measured weld profiles were prepared for FE‐simulations of the theoretical notch factor Kt. It is possible to predict the fatigue critical weld transition by means of the maximum Kt. Combining the test results with the statistical evaluation of the notch factors, a definite correlation between fatigue life and geometrical notch effect can be shown. [ABSTRACT FROM AUTHOR]

Abstract: Automated manufacturing of tubular joints for jacket support structures – Description of the welding process chain as well as integration of the process parameters within the fatigue design. The development within the offshore wind energy sector towards more powerful turbines combined with increasing water depth for new wind parks is challenging both, the designer as well as the manufacturer of support structures. Besides XL‐monopiles the jacket support structure is a reasonable alternative due to the high rigidity combined with low material consumption. However, the effort for manufacturing of the hollow section joints reduces the economic potential of jacket structures significantly. Therefore, a changeover from an individual towards a serial production based on automated manufactured tubular joints combined with standardized pipes has to be achieved. Hence, this paper addresses the welding process chain of automated manufactured tubular joints including digitization of the relevant manufacturing parameters such as laser scanning of the weld seam geometry. Additionally a methodology for the computation of the notch radius as well as the weld seam angle is presented based on the scanned profiles of three analysis points of an automated manufactured tubular X‐joint. Subsequently, these parameters are considered within the notch stress approach based fatigue design and their impact is quantified by a comparison with the structural stress approach using equivalent stress concentration factors. [ABSTRACT FROM AUTHOR]

Abstract: In Japan, the new steel‐glass architecture of railway stations observes usually not only the typical canons of aesthetics but often also – increasingly – the local habits, traditions and social features. Moreover, such architecture is understood to respect well the natural and built environment – forming friendly compositions, which respond fairly to the needs of contemporary Japanese people. Thus, that architecture becomes certain steel‐glass art of structures. In this paper, on the basis of several practical examples, such special steel‐glass art will be presented. [ABSTRACT FROM AUTHOR]

Abstract: Modern railway bridges as thick‐plate trough bridges – Optimization of fatigue design and life‐cycle analyses. Innovative improved design solutions of bridge constructions increasingly aim at maintenance reduced structures where the utilization and surrounding traffic routes are affected only in minor extent by rehabilitation and maintenance works. As part of the FOSTA‐AiF‐research project „Holistic Assessment of steel‐ and composite railway bridges according to criteria of sustainability” (P978) specific investigations were carried out in order to optimize different railway bridge types by improving single structural details and construction variants types. To assess the benefits of these optimized constructions within the life‐cycle of the bridge, the conventional and improved constructions were compared with each other by applying sustainability analyses. This paper deals with the evaluation of the trough bridges with thick track plates which was especially developed for rail traffic constructions and which is also known as thick‐plate trough bridges. It focusses on questions related to the fatigue design, uses large scale tests for verifications and provides recommendations for the construction and design. [ABSTRACT FROM AUTHOR]

Abstract: Modern heavy plate solutions for bridge constructions for sustainable, efficient constructions. In many European countries infrastructure – road as well as railway infrastructure – needs intensive investments to follow the growing demands of mobility and goods traffic. Steel or steel composite bridges offer in this context viable and very sustainable solutions. Due to its unlimited recyclability steel can in general be seen as the ideal material for such sustainable constructions, but especially when designers or fabricators consistently exploit the potentials nowadays available thanks to smart product developments during steel production very cost‐efficient and remarkable constructions are realizable . It therefore pays off to select modern and innovative grades and high‐quality steels, like longitudinally profiled plates or higher strength thermomechanically rolled or quenched and tempered steels, as early as the planning and design phase. Modern innovations in steel permit not only highly efficient, cost‐optimized fabrication but also more slender and architectural aesthetics. This paper will highlight some of these possibilities in heavy plate production for bridge building. [ABSTRACT FROM AUTHOR]

Abstract: Applying the theory of structural state of stress, this paper investigates the behaviour characteristics of concrete‐filled stainless steel tubular (CFSST) short columns during their experimental working process. First, the sum of the generalized strain energy density (GSED) values (Eij) of the short column at every load value (Fj) is normalized as Ej,norm to describe the structural state of stress. Then, the state of stress jump is identified by applying the Mann‐Kendall (M‐K) criterion to the Ej,norm‐Fj curve creatively, following the rule of quantitative change to qualitative change. The investigation reveals the general state of stress mutation characteristics of short columns at specific individual loads, leading to an update of the failure load. Furthermore, it is verified that the simulative working behaviour of short columns can also reflect the state of stress characteristics revealed through the investigation into the experimental data. Hence, we formulate the relationship between the failure loads of CFSST short columns using the simulative data, and then validate it through both experimental and simulative data. In total, this study explores a new way to reveal some unseen working characteristics of structures; hopefully, it will initiate similar research on various structures, and the results achieved will lead to more rational design codes. [ABSTRACT FROM AUTHOR]

Abstract: Large‐size HV‐bolt sets in ring‐flange connections are crucial structural members of wind turbine support structures, which are subjected to strong static as well as cyclic loads with considerable numbers of load cycles. Additionally to direct experimental investigations on the structural components themselves, analytical and numerical assessment methods of the bolts performance inside ring‐flanges are valuable engineering tools to gain knowledge about the structural behaviour and to support the development of appropriate design solutions. In this paper, probabilistic fatigue assessment, using Monte Carlo Simulation technique, is utilized to compute the failure probability and to investigate the influence of the scattering parameters on the fatigue performance of HV‐bolt sets in ring‐flange connections. Subsequently, an analytical fatigue calculation approach for large‐size bolts, based on the local strain‐life concept, is introduced. Results from two different methods for determination of required base material properties are compared. The calculations are validated on fatigue tests on HV‐bolt sets and results are discussed with regard to the evaluation of local loading conditions, damage assessment parameters and sensitivity to base material input. [ABSTRACT FROM AUTHOR]

Abstract: Investigations on the load bearing behavior of composite dowels positioned close to the free concrete surface. Composite dowels are an economic alternative to headed studs with various advantages. Modern concrete slabs are dimensioned increasingly thinner and often include several additional functions, for example air conditioning or thermal activation of concrete surfaces. For those applications composite dowels can be positioned horizontally in the concrete slab. Existing investigations on composite dowels describe different failure modes of composite structures such as splitting of the concrete, local compression of the concrete, pry‐out of a concrete cone or plasticizing of the steel teeth. At University of Kaiserslautern composite dowels with positions close to the free surface of the concrete slab were investigated experimentally by push‐out‐tests and on the basis of numerical simulations. In addition, the positive influence of a spiral reinforcement between the steel teeth was analyzed. Further primary and secondary failure mechanisms were observed for this specific position of the composite dowels. These investigations and a design approach will be presented within the paper. [ABSTRACT FROM AUTHOR]

Abstract: Equivalent initial imperfections for applying the partial internal forces method for flexural buckling about the weak axis. This paper compares design approaches for equivalent initial imperfections of steel members with hot‐rolled double symmetric I‐/H‐profiles subjected to buckling about the weak axis. In addition to the normative rules applied in Germany and Europe, design approaches for imperfections are also taken into account, which are currently discussed as part of the further development of Eurocode 3. A proposal using the partial internal forces method allows a consistent design for steel members taking into account the cross‐sectional failure as well as the flexural buckling about the strong and weak axis. The proposal leads to design results that agree well with the results of numerical simulations. [ABSTRACT FROM AUTHOR]

Abstract: Dedicated to Prof. Dr.‐Ing. habil. Joachim Lindner on the occasion of his 80th birthday This paper reports the latest developments concerning the application of Generalised Beam Theory (GBT) to thin‐walled members with deformable cross‐section and whose undeformed axis is a circular arc, with no pre‐twist. Initially, the fundamental equations and relations are presented, leading to the first‐order equilibrium equations and associated boundary conditions, which can be written in terms of GBT modal matrices or stress resultants. Then, the procedure to obtain the cross‐section deformation modes is explained. Arbitrary (open, closed or ”mixed“) flat‐walled cross‐sections are covered, even though the kinematic constraints employed to subdivide the modes are much more complex than for prismatic members – in particular, the mode shapes become dependent on the curvature of the beam axis. Using a displacement‐based GBT finite element, a set of illustrative examples is presented, involving complex local‐distortional‐global deformation. These examples show that very accurate results are obtained with the proposed GBT formulation and that the modal solution provides in‐depth insight into the structural behaviour of naturally curved members. [ABSTRACT FROM AUTHOR]

Abstract: Introduction of the Direct Strength Method into the design of cold formed steel members according to EN 1993‐1‐3. Cold formed steel members have a varied area of applications in steel lightweight constructions but are subject to local and global instabilities due to compressive and bending stress. The design method of the European Standard EN 1993‐1‐3 is based on the Method of Effective Widths covering local and distortional buckling. Unfortunately, an EN 1993‐1‐3 design is time‐consuming and prone to errors, furthermore the results are often conservative. This paper is going to introduce a new, practical design method for cold‐formed steel sections that combines the established European regulations of global instabilities with the Direct Strength Method (DSM) described in the North American standard AISI Standard 100 regarding local stability analysis. Based on comparative studies of mono‐symmetric cross‐sections it is possible to demonstrate that this new method offers a great potential of improving the design of cold‐formed sections, additionally improves the economic efficiency of lightweight steel sections. More theoretical and experimental investigations are needed, deeper leading questions are to answer, until this method is able to supplement the European standard. [ABSTRACT FROM AUTHOR]

Abstract: Trough girders are widely accepted in engineering on account of lowing construction depth and protection against traffic noise pollution, but most of them are used for simple‐supported girder bridges with a span of generally less than 30 m. On the railway line of Nanjing–Qidong in China a new railway bridge will be built which has a span of over 64 m but a construction depth of less than 2.4 m on which Shanghai–Nantong railway line is also passed, so the type of concrete‐filled steel tube tied‐arch bridge with trough girder was chosen. For such a new structure hardly used in engineering, there are no research results yet available about mechanical properties of the structure. This paper therefore makes for the bridge an experimental model of 1:4 geometric scale in order to test mechanical properties under operation load, cracking load, and ultimate load such as cracking diagram, load‐carrying capacity, stress distribution, and failure mechanism. According to the experimental results, when the model is subjected to longitudinal bending moment, the failure mode is similar to that of pure bending of a girder, and when the model is subjected to transverse bending moment failure mode behaves like the flexural failure mode of the traditional reinforced concrete structure. A non‐linear element analysis is also made on the model with the results in good agreement with that of the experiment. The same modeling method is applied to the finite element analysis of the real bridge, considering various load in design. In the analysis, it is finally verified that this new type of bridge meets specification requirements in strength, rigidity, and resistance to cracking. [ABSTRACT FROM AUTHOR]

Abstract: Limitations on the use of partial shear connection in composite beams with single flange steel beams and composite dowels – Part 2: Analysis of the load bearing and deformation behaviour and modes for the minimum degree of partial shear connection. For composite beams with single flange steel beams and composite dowel connectors, the limitations to the use of partial shear connection have not yet been clarified. In this paper (continuation of [1]) the bearing and deformation behavior is analyzed using experimentally verified FE models. For this purpose, a comprehensive parametric study is performed, in which, in addition to the degree of shear connection and different cross‐sectional types, different parameters of the composite beam are varied which do not enter into the analytical calculation of the plastic bending moment capacity. These are, on the one hand, properties which depend on the static system, such as the loading situation (single load or uniformly distributed load) and the span, on the other hand, the slip deformation behavior of the connectors is varied by establishing different ductility characteristics for pry‐out and steel failure of composite dowels. Based on the simulation results, equations are derived for the minimum degree of partial shear connection for beams with single flange steel sections and composite dowel connectors including all required limitations of use for plastic design. The own models are compared to regulations given in a technical approval for composite dowels. The models may also be adopted for composite beams with steel T‐sections and horizontally lying shear studs. [ABSTRACT FROM AUTHOR]

Abstract: 50th anniversary of the Bonn‐Nord (Friedrich‐Ebert) Bridge across river Rhine. This bridge, opened to traffic on June 28, 1967, was the world's first cable‐stayed bridge with a central multicable system (80 locked coil ropes) and has a main span of 280 m. The 36.3 m wide bridge deck consists of a central steel box girder and wide cantilevers, the 49.4 m high towers are also from steel. The side spans were erected on the final and auxiliary piers and the main span by free cantilevering. The paper deals with the design, shop fabrication and erection of the bridge, a recent structural health monitoring and the results of calculations according to the actual Eurocodes. Although the bridge does not meet some of the actual requirements, no major structural defects have been detected. So, the life time of the bridge may not be determined by the structural but by the traffic capacity which may require a wider bridge in about 2040. [ABSTRACT FROM AUTHOR]

Abstract: Failure of a steel pallet rack in Athens. Pallet racking systems have peculiar characteristics which differ from usual steel structures that make them sensitive to stability failure modes. In the present paper a rack failure is presented where the rack has failed due to lateral torsional and distortional buckling of its most stressed uprights. The structural behavior was studied by a combination of experimental and numerical/analytical methods. The investigations included test loading, bending tests on pallet beams, compression tests on stub column and bending tests on beam end connectors. Subsequently, a global geometrical non‐linear analysis is performed on the 3‐D system. Its results indicate by comparison with the pictures of the actual structure that the collapse mode is correctly detected. Conclusions are drawn that recommend the performance of static and dynamic analyses on an obligatory basis. [ABSTRACT FROM AUTHOR]

Mit der Einführung des Eurocodes 3 und der DIN EN 1090-2 ist es in Deutschland unter anderem in Bezug auf die Ausführung von geschraubten Verbindungen in Stahltragwerken zu großen Verwirrungen gekommen. Diese beruhen im Wesentlichen - aber nicht nur - auf der Frage: Welches Vorspannkraftniveau darf bei welchem Verbindungstyp mit welchem Anziehverfahren angesetzt werden? Wo die Frage nach dem richtigen Anziehverfahren relativ schnell geklärt ist, da dieses über den Nationalen Anhang zur Bemessungsnorm für Stahlbauanschlüsse, der DIN EN 1993-1-8/NA, eindeutig an die Höhe des Vorspannkraftniveaus gekoppelt ist, führt die Frage nach dem 'richtigen' Vorspannkraftniveau sowohl beim Tragwerksplaner als auch bei der ausführenden Stahlbaufirma immer wieder zu großen Diskussionen, dass das in DIN EN 1090-2 angebotene Mindestvorspannkraftniveau Fp,C in Deutschland nur mit dem in der nationalen Praxis zwar durchaus bekannten, aber absolut unüblichen Kombinierten Vorspannverfahren aufgebracht werden darf. Alternativ dazu wurde in DIN EN 1993-1-8/NA das niedrigere 'alte' deutsche Regelvorspannkraftniveau Fp,C* mit Ausführungsregeln zum Anziehen mittels des modifizierten Drehmoment-Vorspannverfahrens wieder definiert. Weitere praxisrelevante Fragestellungen betreffen exemplarisch das Anziehen von nicht vorgespannten Schraubverbindungen und den Einsatz von nicht CE-gekennzeichneten Komponenten einer CE-gekennzeichneten Schraubengarnitur. Im Rahmen des vorliegenden Beitrags werden diese und weitere Fragestellungen zum Anziehen von geschraubten Verbindungen im Stahlbau zusammenfassend beantwortet. Tightening of bolted connections according to Eurocode 3 and DIN EN 1090-2. With the introduction of Eurocode 3 and DIN EN 1090-2, great confusions arise in Germany regarding the execution of bolted connections in steel structures. This is based essentially - but not exclusively - on the question: which preload level may be applied in which connection type with which tightening procedure? Where the question of the 'correct' tightening procedure is resolved relatively quickly, since this is clearly linked via DIN EN 1993-1-8 / NA at the height of the applied preload level, yields the question of the 'correct' preload level for both the structural engineer and the executive steel construction company to major discussions since DIN EN 1090-2 offers the minimum preloading force Fp,C which is allowed to be applied in Germany only by the - although known, but absolutely unusual - combined method. Alternatively, the lower 'old' German preloading force Fp,C* is defined in DIN EN 1993-1-8 / NA with execution rules for the modified torque method. Other practical questions relate to the tightening of non-preloaded bolts and the use of non CE-marked components of a CE-marked bolt assembly. As part of this paper, these and other issues for the tightening of bolted connections in steel structures are answered. [ABSTRACT FROM AUTHOR]

Hochspannungsstahlgittermaste sind Stahlbauwerke. Der Nachweis erfolgt in Deutschland seit 1903 nach verschiedenen Ausgaben der VDE 0210. Die aktuelle Ausgabe und alle Vorgängerausgaben enthalten keine Berücksichtigung der Höhe möglicher Schadensfolgen. Das bedeutet, dass für alle Maststandorte, ganz gleich ob in bebautem Gebiet oder in Gebieten ohne Personenzugang, die gleiche Versagenswahrscheinlichkeit angestrebt wird. Eine Grenze für diese überall gleich angestrebte Versagenswahrscheinlichkeit ist allerdings unbekannt, denn ein Zahlenwert für die zugelassene Versagenswahrscheinlichkeit wird in den VDE 0210-Normausgaben, wie bei anderen technischen Normen des Bauwesens auch üblich, nicht genannt. An Maststandorten mit kleinen Schadensfolgen werden somit möglicherweise mehr -Ressourcen eingesetzt als nötig, an Maststandorten mit großen Schadensfolgen fehlen diese dann eventuell. Der vorliegende Beitrag zeigt am Beispiel von Hochspannungsstahlgittermasten eine Möglichkeit, bestehende Bauwerke probabilistisch nachzuweisen und die der Gesellschaft zur Verfügung stehenden -begrenzten Ressourcen optimal einzusetzen. Probabilistic static calculation of existing high voltage steel lattice towers. High voltage steel lattice towers are steel constructions. The static calculation happens since 1903 in accordance with several editions of VDE 0210. All editions of this code including the current edition include no consideration of an amount of failure consequences. At all tower locations the same value of probability of failure is targeted. It does not matter whether the location is built-up or there is no admittance of persons. A limit for this everyplace equal targeted probability of failure is certainly unknown. A value for the tolerated probability of failure is commonly not mentioned in codes of civil engineering including the VDE 0210. At tower locations with little failure consequences more resources than necessary will set in. It is possible that these resources are missing at locations with high failure consequences. This paper tells about an optional method for probabilistic static calculation of existing constructions using the example of high voltage steel lattice towers. Subsequently the limited available resources of human society can be used optimally. [ABSTRACT FROM AUTHOR]

Die Sichtprüfung von Schweißnähten ist die einfachste und am häufigsten durchgeführte Art der Schweißnahtprüfungen. Neben laufenden Soll-Kontrollen durch das Schweißpersonal während der Fertigung ist abschließend die Sichtprüfung für alle Ausführungsklassen vollumfänglich nach EN 1990-2 durchzuführen. Dabei können direkte und indirekte Prüfmethoden angewendet werden, zu denen auch die Geometrieerfassung durch Laserscanning zu zählen ist. In diesem Beitrag wird die praktische Anwendung eines mobilen Laserscansystems für den Vergleich unterschiedlicher Schweißverfahren und Schweißlagen aufgezeigt und das Potential einer vollautomatischen Sichtprüfung erläutert. Ein solches Verfahren besitzt gegenüber einer manuellen Sichtprüfung einige Vorteile. Zum einen kann eine hoch qualitative und vor allem unabhängige Bewertung der Schweißnahtqualität sichergestellt werden. Des Weiteren können die so gewonnen Daten zu Dokumentationszwecken sowie als Inputdaten für eine Ermüdungsberechnung der entsprechenden Bauteile zum Einsatz kommen. Der letzte Punkt wird in Teil 2 dieses Beitrages thematisiert werden. Welded seam evaluation based on 3D laser scanning - Practical application of mobile laser scanning systems for surface analysis of welds - Part 1. The visual examination of welds is a simple and frequently used method for weld inspections. Besides the comparison between a target and performance state executed by the technical staff during the production process, a final visual inspection of the welds for all execution classes is demanded by EN 1990-2. According to this code, direct or indirect methods can be applied. An example for an indirect method is the scanning of the real geometry of the weld using laser scan technology. In this paper the practical use of a mobile laser scan device is shown. Different welding methods as well as different welding positions are examined and the potential of a fully automatized (visual) inspection is exemplified. Such a procedure offers important advantages compared to a manual examination. On the one hand a high quality and most important an independent examination of the weld quality can be ensured. This data can also be used for documentation purposes and as input for a component specific fatigue life calculation. This calculation is described in part 2 of this article. [ABSTRACT FROM AUTHOR]

Cost-efficient design concepts of monopile foundations for offshore wind turbines have recently focused on bolted ring flange connections. The bolted connection between the monopile and transition piece implies that the pile-driving operation by means of a hydraulic hammer is directly performed on the flange. The highly dynamic pile-driving loads may lead to substantial pre-damages at the flange structure and weld. For the determination of pile-driving fatigue, the initial hammer strike as well as an induced oscillation has to be considered. In this paper, the main parameters defining a pile-driving analysis are presented. Basic pile-driving effects are investigated by application of a one-dimensional wave equation analysis. The results are used to validate a detailed finite element (FE) model which simulates the initial hammer strike as well as the dynamic response of the pile-soil interaction. Based on the calculation results, recommendations for design optimizations and evaluation methods of pile-driving fatigue are provided. [ABSTRACT FROM AUTHOR]

Crane girders with hinged supports on top of the columns are often fixed to the column head by placing vertical bolts between the girder's lower flange and the column's head plate, in order to prevent uplift of the girder. The passing of the crane load over the girder causes a deflection of the latter, which in turn leads to rotations of the girder end cross-sections. The relative movements and rotations between the girder's lower flange and the column's head plate can lead to exceptionally large bending stresses in the fixing bolts, as is illustrated by means of a numerical (FEM) example in this paper. A simple engineering model, which is however capable of capturing all the relevant parameters for the different types of fixing detailing, is developed for the determination of these additional bending stresses and was verified by comparisons with the FEM models. Finally, proposals for an improved detailing solution are presented. [ABSTRACT FROM AUTHOR]

The new road bridge represents in modern times the fourth and historically already the fifth crossing of the river Vistula in Toruń (Thorunium). Together with a short reference to the history of the city and its earlier constructed bridges, this paper shows the newest bridge - an arch bridge of 270 m span length and 50 m rise of both its superstructures. The first part contains details on the design and the construction, as well as the cultural background of the bridge. Part 2 presents the theoretical and experimental controls, which are competent for the bridge mounting and load test. This contribution is devoted to the lately passed Marek Sudak, who was besides the first here mentioned author the second chief designer of that bridge. [ABSTRACT FROM AUTHOR]

Due to the demand for sustainable buildings and slim constructions, composite slim-floor systems become more important. The present European Codes do not include complete design rules for shallow-floor beams. In the design, additional regulations have to be considered for ultimate limit state, serviceability limit state and fire design. In this paper the characteristics in erection state, for the cross section classification, the plastic moment resistance and the influence of transverse bending moments are presented. Apart from traditional sections consisting of rolled profiles also floor slabs with integrated steel box-sections have been considered. [ABSTRACT FROM AUTHOR]

Elastic gridshells making use of a rapid construction process, in which the spatial geometry of the gridshell is obtained by bending an initially flat grid. This particular shaping process saves time during the erection of the structure, as the grid members must not be bent individually but the grid can be shaped as a whole. Moreover, the assembly of the connections between the superposed rod layers of the grid can be done on the ground on a flat geometry. Nevertheless, in order to introduce shear stiffness to the initially unstable grid lattice, an additional layer of beam elements or diagonal cables must be added. The assembling of this bracing layer is usually time-consuming and requires additional supplies such as cherry-pickers or movable scaffolds. In this manner one of the great advantages – the rapid deployability of elastic gridshells – is clearly reduced. In order to accelerate the construction process of deployable elastic gridshells, we propose to use covering textile membranes as stiffening and at the same time cladding surfaces. In this paper we explain the design space for the development of elastic shells mainly made of GFRP and the structural behaviour of an elastic hemispheric gridshell braced with a membrane layer. Different connection configurations between membrane and grid have been analysed in FE-simualtions and the results have been compared with the load bearing behavior of a physical Prototype. [ABSTRACT FROM AUTHOR]