Prof. Dr.-Ing. Natalie Stranghöner

Metal and Lightweight Structures
University of Duisburg-Essen

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  • Architectural woven polyester fabrics: examination of possible classification of stiffness values in correlation with strength values
    Uhlemann, J. and Stranghöner, N. and Motevalli, M. and Balzani, D.
    Architectural Engineering and Design Management (2020)
    Down to the present day, the determination of stiffness parameters for architectural fabrics, mainly used as coated woven fabrics, is a field of intense discussion. Designers and material producers are affected by an existing uncertainty. The present contribution investigates the possibility to provide tables of tensile stiffness parameters for specific materials in which tensile stiffness values are given dependent on the material’s tensile strength. The focus is on PVC-coated polyester fabrics as the most commonly used material for textile architecture. Materials of four different producers have been tested experimentally. Furthermore, from each material producer products of different strength classes have been considered in the test series. To achieve a general statement on the possibility of material classification according to their tensile stiffness, material parameters of two different material formulations have been investigated: (1) for a simplified but widely applied linear-elastic material model based on a standardized test and evaluation method and (2) for a recently developed more advanced orthotropic hyperelastic nonlinear material model. The tensile stiffness parameters are statistically evaluated and compared. In order to achieve a required basis, standardized and project-specific biaxial test procedures are presented and analysed in combination with established evaluation procedures. A tabulation of tensile stiffness parameters would be of great help for design engineers and material producers. The results of the present work will lead to a possible classified tabulation of the investigated materials in a meaningful manner. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/17452007.2020.1793720
  • Biaxial load bearing behaviour of woven fabric membranes under multiple loads [Biaxiales Tragverhalten von Gewebemembranen nach DIN EN 17117-1]
    Uhlemann, J. and Stranghöner, N.
    Stahlbau 89 (2020)
    Biaxial load bearing behaviour of woven fabric membranes under multiple loads. With DIN EN 17117-1, a European standard for the performance and evaluation of biaxial tensile tests on coated textiles, as used in membrane construction, has been available for about a year now. This article offers a presentation, analysis and valuation of the new regulations. Particular innovations compared to the previous test practice, such as regulations on test specimen geometry, load protocol and loading speed are explained and evaluated. The article shows the difference between elastic design constants and elastic comparison constants and gives examples of their application and interpretation. © 2020, Ernst und Sohn. All rights reserved.
    view abstract10.1002/stab.202000040
  • Experimental investigation on the preload behaviour of noise barrier steel post fastenings on structures [Experimentelle Untersuchung von Lärmschutzwandstehern und deren Befestigung auf Kunstbauten: Teil 2 – Vorspannverhalten]
    Reiterer, M. and Stranghöner, N. and Jungbluth, D.
    Stahlbau 89 (2020)
    Experimental investigation on the preload behaviour of noise barrier steel post fastenings on structures. In addition to part 1 – fatigue behaviour in the present article the preload behaviour of noise barrier steel post fastenings on structures is experimentally studied and valuated. In a first indicative pre-test altogether four bolted connections were preloaded and released three times consecutively with a defined level of tightening torque and in every test the solid lubricant Molykote 1000 was applied. The tested threaded bolts and screw nuts are made of stainless steel A4-80 of M20 dimension. Beside the investigation of the preload behaviour of the bolted connection the pre-tests were performed to study the influence of different washer types to the resulting preload level within the threaded bolts. Due to the fact that bolted connections made of stainless steel are currently not regulated in civil engineering standards, it was decided to perform additional experimental tests in term of a tightening procedure test on the calibrated tightening-torque testing machine facility for mechanical fasteners of the Institute for Metal and Light Weight Structures of University of Duisburg-Essen. On the basis of the performed tightening-torque tests considering threaded bolts of M16 and M20 dimension made of stainless steel in combination with stainless steel wedge-lock washers and solid lubricant a tightening procedure for preloading threaded bolts made of stainless steel was defined. © 2020, Ernst und Sohn. All rights reserved.
    view abstract10.1002/stab.201900101
  • Membrane supporting structures [Membrantragwerke]
    Stranghöner, N.
    Stahlbau 89 (2020)
    view abstract10.1002/stab.202070803
  • Preloaded bolted connections made of stainless steel [Vorgespannte Schraubverbindungen aus nichtrostendem Stahl]
    Stranghöner, N. and Jungbluth, D. and Afzali, N. and Abraham, C.
    Stahlbau 89 (2020)
    Preloaded bolted connections made of stainless steel. The application of preloaded bolted connections made of stainless steel is demanded in reasons of serviceability or ultimate limit state, e. g. when used in particularly corrosive environments or in stainless steel structures. However, based on EN 1090-2 the use of bolting assemblies made of stainless steel is restricted to non-preloaded bolted connections for several reasons. Resentment still exists against the application of stainless steel bolting assemblies in preloaded connections due to the expected high preload losses and the problem of cold welding (“seizure”). In addition, there are currently no bolting assemblies available on the market comparable to the DIN EN 14399 standards, which are tested by the manufacturer for suitability for preloading including the application of a calibrated lubrication. The main product standard for high-strength structural bolting assemblies for preloading of bolted connections in steel structures, EN 14399-1, is also limited to the application of bolts made of carbon steel, so that the use is also restricted there. Consequently, procedure tests must be carried out for every application scenario. The presented contribution shall give an insight into the possibilities of the application of stainless steel in preloaded bolted connections in general, and in slip-resistant connections in particular. In addition, assistance and guidance for the approach within a procedure test is given by the “Bolt Tightening Qualification Procedure (BTQP)” as a supplement to the regulations of the DASt-Guideline 024. © 2020, Ernst und Sohn. All rights reserved.
    view abstract10.1002/stab.202000004
  • Saturation of the stress-strain behaviour of architectural fabrics
    Uhlemann, J. and Surholt, F. and Westerhoff, A. and Stranghöner, N. and Motevalli, M. and Balzani, D.
    Materials and Design 191 (2020)
    The stress-strain characteristics of nonlinear visco-elastoplastic architectural fabrics show a mechanically saturating behaviour in cyclic tensile tests: stiffness changes decline, the increase of permanent strain decreases and the nonlinear material behaviour increasingly approaches a linear behaviour. Appropriate stress-strain paths for elastic material models for the structural analysis must be taken from load cycles in which the saturation processes are finished to a satisfactory degree. Generally, consistency of elastic analysis of fabric strutctures is achieved when it is based on the fabric's saturated state and the closely linked stable amount of presstress in the structure. To determine load cycles correlated to the saturated state, a new method is proposed here which considers three different inspection characteristics: irreversible strain increment, total strain increment and intensity of nonlinearity. Biaxial saturation tests with 1000 load cycles are performed on a PVC-coated polyester fabric. For each inspection characteristic, saturation development curves are generated. They are fitted by functions with horizontal asymptotes and are thereby extrapolated, revealing that for the tested polyster fabric tens of thousands of load cycles are required to achieve a satisfying state of saturation. The meaning and implications for biaxial testing and analysis of textile structures is discussed. © 2020 The Authors
    view abstract10.1016/j.matdes.2020.108584
  • The elastic share of inelastic stress-strain paths of woven fabrics
    Motevalli, M. and Uhlemann, J. and Stranghöner, N. and Balzani, D.
    Materials 13 (2020)
    Manifold variations of the mechanical behavior of structural woven fabrics appear in the first load cycles. Nevertheless, invariable states, i.e., mechanically saturated states, can be approached by multiple monotonous load cycle biaxial tests. In a state acceptably close to the ideal saturated state, the stress-strain paths reveal the elastic share of the initially inelastic stress-strain paths of woven fabrics. In this paper, the mechanical saturation behavior of two types of PTFE-coated woven glass fiber fabrics is examined and compared to the recently reported saturation behavior of a PVC-coated polyester fabric. With the help of the saturation test data, an extrapolation function is developed that facilitates an estimation of late cycle stiffness behavior based on measured early cycle behavior. Furthermore, the considerable impact of late cycle properties on structural analyses is shown exemplarily in the numerical simulation of a prestressed fabric structure by comparing results achieved from late and early load cycle stiffness parameters. © 2020 by the authors.
    view abstract10.3390/MA13194243
  • A new nonlinear polyconvex orthotropic material model for the robust simulation of technical fabrics in civil engineering applications at large strains – validation with large-scale experiment [Ein neues polykonvexes orthotropes materialmodell zur robusten simulation von textilmembranen im bauingenieurwesen unter berücksichtigung großer deformationen – validierung anhand eines großbauteilversuchs]
    Motevalli, M. and Uhlemann, J. and Stranghöner, N. and Balzani, D.
    Bauingenieur 94 (2019)
    A polyconvex orthotropic material model is proposed for the simulation of tensile membrane structures. The notion of anisotropic metric tensors is employed in the formulation of the polyconvex orthotropic term which allows for the description of the interaction of the warp and fill yarns. The model is adjusted to the stress-strain paths of uni-and biaxial tensile tests of a woven fabric and the results are compared with the linear elastic model. The lateral contraction in the uniaxial loading case is taken into account to also capture the strong crosswise interactions. An increased number of load cycles is considered in the experiments to reach a saturated elastic state of the material. A new method is proposed enabling in principle the identification of unique (linear) stiffness parameters by previously identifying the (nonlinear) model parameters. Eventually, the proposed nonlinear model contains only 4 material parameters to be identified for the individual membrane material. Moreover, a new large-scale experimental setting is presented which allows for the validation of the proposed model response in real-life engineering applications. The numerical robustness of the model is tested in an advanced simulation of a large roof structure under application of realistic boundary conditions. © 2019, VDI Fachmedien GmBbH & Co.. All rights reserved.
    view abstract10.37544/0005-6650-2019-12-50
  • Geometrically nonlinear simulation of textile membrane structures based on orthotropic hyperelastic energy functions
    Motevalli, M. and Uhlemann, J. and Stranghöner, N. and Balzani, D.
    Composite Structures 223 (2019)
    New hyperelastic orthotropic models are proposed for the simulation of textile membranes used in civil engineering applications. In contrast to published models, part of the new models is polyconvex and ensures thereby a physically meaningful and mathematically sound formulation. The models are adjusted to uniaxial tension tests performed in warp and fill direction, where not only the stress-strain response in tension direction is accounted for but also the lateral contraction. Thereby, the crosswise interaction between the warp and fill direction is captured. In a series of different boundary value problems the new models as well as a competitive formulation given in literature are compared with respect to the accuracy to represent the experimental data, the mathematical properties as well as the numerical robustness. As it turns out, most formulations including the model from the literature show a loss of material stability and non-converging Newton iterations in structural simulations. Only one of the proposed polyconvex formulations works robustly in numerical simulations of realistic structural engineering problems. Thereby, this new orthotropic model enables realistic simulations of textile membranes in a fully geometrically nonlinear setting, which does not require simplifications based on linearized strains, which are currently used as standard in engineering practice. © 2019 Elsevier Ltd
    view abstract10.1016/j.compstruct.2019.110908
  • Influence of material nonlinearity on the buckling resistance of stainless steel shells
    Stranghöner, N. and Azizi, E. and Gorbachov, A.
    Journal of Constructional Steel Research 157 (2019)
    One of the greatest challenges in the design of shell structures made of stainless steel compared to those made of carbon steel is the meaningful consideration of the nonlinear stress-strain behaviour of stainless steels which has a significant influence on the buckling behaviour of axially compressed shells in the medium slenderness range and lead to lower buckling strengths. A detailed description of the actual material behaviour of stainless steels is given by the material model developed by Arrayago, Real and Gardner on the basis of the by Rasmussen modified two stage Ramberg-Osgood material model. One of the parameters of which the model consists is the exponent n, which describes the nonlinear behaviour just before the 0.2% proof stress. This exponent is of great importance for the buckling behaviour of axially loaded shell structures of medium slenderness. For this reason, a thorough numerical parametric study has been conducted in order to evaluate the effect of the nonlinear material behaviour described by the exponent n on the buckling resistance of austenitic, duplex, and ferritic stainless steel shells. The numerical model has been validated by experimental results of axially compressed cylindrical shells conducted in the frame of the European RFCS-research project BiogaSS. © 2019
    view abstract10.1016/j.jcsr.2019.02.030
  • Slip factors for slip-resistant connections made of stainless steel
    Stranghöner, N. and Afzali, N. and de Vries, P. and Schedin, E. and Pilhagen, J.
    Journal of Constructional Steel Research 152 (2019)
    Stainless steels are becoming more and more popular as a construction material in both building and civil engineering structures, because of their high material strength, ductility and corrosion resistance. In this frame, the execution of slip-resistant connections made of stainless steel is necessary, e. g. in footbridges, facades etc. As no design regulations exist in any code, special experimental testing has to be performed in each case. Stainless steel alloys are thought to suffer more than carbon steels from time dependent viscoplastic deformation at room temperature. It could lead to higher preload losses and consequently to lower slip factors than achieved for carbon steels with comparable surface treatment. However, no evidence of this behaviour can be found in literature for preloaded bolted connections. For this reason, slip factors for the various stainless steel grades have to be determined experimentally if they want to be used in the steel structures. In the frame of the European RFCS-research project SIROCO, the preloading behaviour of stainless steel bolted connections as well as the slip-resistant behaviour of slip-resistant connections made of austenitic, various duplex and ferritic stainless steels have been investigated. In this paper, the results of slip factor tests on four stainless steel grades are presented and the influence of different surface treatments and the preload level on the slip factor of stainless steel slip-resistant connections is discussed. Finally, slip factors for various stainless steel grades with different surface treatments are proposed for a future implementation in the next revision of EN 1090-2. © 2018 Elsevier Ltd
    view abstract10.1016/j.jcsr.2018.07.005
  • Viscoplastic deformation behaviour of preloaded stainless steel connections
    Afzali, N. and Stranghöner, N. and Pilhagen, J. and Manninen, T. and Schedin, E.
    Journal of Constructional Steel Research 152 (2019)
    Preloaded bolted connections made of stainless steel are not commonly used in stainless steel structures as their application is not allowed by the execution standard EN 1090–2 and the design standard EN 1993-1-4 for stainless steel structures unless otherwise specified, respectively unless their acceptability for a particular application has been demonstrated from test results. This restriction is mainly caused by three facts: firstly, it is feared that due to the viscoplastic deformation behaviour of stainless steel, severe preload losses have to be expected, secondly, neither stainless steel bolting assemblies for preloading nor tightening procedures exist on which could have been relied and thirdly, galling and seizure of stainless steel bolting assemblies lead to problems on site. These three questions, beside others, were treated in the frame of the European RFCS-research project “Execution and reliability of slip resistant connections for steel structures using CS and SS” SIROCO. Some of the results are presented in this contribution with the main focus on the loss of preload of preloaded stainless steel bolted connections. The main conclusion is that preloaded stainless steel bolted connections can be treated similar to those made of carbon steel with regard to preload losses as they show comparable magnitudes of preload losses. © 2018 Elsevier Ltd
    view abstract10.1016/j.jcsr.2018.07.004
  • Brittle fracture of high-strength bolts of large diameters at low temperatures
    Stranghöner, N. and Lorenz, C. and Feldmann, M. and Citarelli, S. and Bleck, W. and Münstermann, S. and Brinnel, V.
    Stahlbau 87 (2018)
    Brittle fracture of high-strength bolts of large diameters at low temperatures. High-strength structural bolting assemblies of the system HV are executed as preloaded bolting assemblies in highly loaded steel structures. More often these bolting assemblies are used up to M72 e. g. in wind energy towers. In addition to static and fatigue loads, these connections are exposed to low temperatures. In case of equal boundary conditions, the risk of brittle fracture increases with increasing thickness of the steel material. In principle, this relation also applies to increasing bolt diameters. Since no systematic investigations into the tendency to brittle fracture of high-strength bolts with large diameter exist and the choice of steel material to avoid brittle fracture of high-strength bolts is not covered in EN 1993-1-10, high-strength bolts of large diameters are made of higher alloyed steels. In the frame of the IGF-project ”Brittle Fracture of High-Strength Bolts of Large Diameters at Low Temperatures“ systematic investigations into the low temperature behaviour of high-strength bolts of the system HV were carried out for bolt diameters from M24 to M64 to assess the risk of brittle fracture for these components. This article presents the main results and conclusions achieved in the research project. Copyright © 2018 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stab.201810559
  • Membrane structures and tents [Membranstrukturen und Zelte]
    Stranghöner, N.
    Stahlbau 87 (2018)
    view abstract10.1002/stab.201870703
  • Membranstrukturen und Zelte
    Stranghöner, N.
    Stahlbau 87 (2018)
    view abstract10.1002/stab.201870703
  • Stainless steel in construction - Design of steel structures made of stainless steel in accordance with DIN EN 1993-1-4 [Nichtrostender Stahl im Bauwesen – Bemessung von Stahltragwerken aus nichtrostendem Stahl nach DIN EN 1993-1-4]
    Stranghöner, N. and Baddoo, N. and Stehr, S.
    Stahlbau 87 (2018)
    view abstract10.1002/stab.201820584
  • Tents and halls made of PVC-coated polyester fabric according to the updated standard series DIN 18204 [Zelthallen aus PVC-beschichtetem Polyestergewebe nach aktualisierter Normenreihe DIN 18204]
    Uhlemann, J. and Stranghöner, N.
    Stahlbau 87 (2018)
    Tents and halls made of PVC-coated polyester fabric according to the updated standard series DIN 18204. The standard series DIN 18204 ”Components for enclosures made of textile fabrics and plastic films (awnings)“ has been extensively reviewed in the last two years. Alongside with updates of normative references, the structure has been fundamentally changed so that the standard can also cover additional textile and plastic structures in new parts to be developed in future. Material specifications have been purified and adapted to new test standards. Moreover, the design concept has been gently revised. The present contribution describes the background, illustrates the changes compared to the previous edition and provides an outlook to the final version. © 2018, Wiley Blackwell. All rights reserved.
    view abstract10.1002/stab.201810618
  • Vorspannkraftverluste geschraubter Verbindungen infolge beschichteter Kontaktflächen
    Stranghöner, N. and Makevičius, L. and Henkel, K.-M. and Glienke, R. and Dörre, M.
    Stahlbau 87 (2018)
    Losses of preload in bolted connections due to coated faying surfaces. Bolted connections are preloaded to increase their resistance and stiffness. Preload losses during the lifetime of a structure might lead to loosening and consequently pose a risk to the serviceability or even the load capacity of the bolted connections. For this reason, the estimation of potential preload losses as well as their consideration during design and execution is an important issue. In the frame of the IGF research project 18711 BG ”Loss of preload of fatigue loaded preloaded bolted connections“ carried out by the Institute for Metal and Lightweight Structures (IML) of the University of Duisburg-Essen in cooperation with Fraunhofer Research Institution for Large Structures in Production Engineering (IGP), Rostock, systematic investigations were carried out on preloaded bolted connections of categories B/C and E according to EN 1993-1-8. Herein, preload losses due to setting and fatigue loading were experimentally determined, evaluated and extrapolated to the intended service life. The investigations were based on different types of M20 bolting assemblies, tightening methods as well as clamping length ratios and surface treatments. © 2018, Ernst und Sohn. All rights reserved.
    view abstract10.1002/stab.201810014
  • Water infiltration impact on tensile strength and breaking strain of architectural fabrics
    Asadi, H. and Uhlemann, J. and Stranghöner, N.
    Advances in Structural Engineering 21 (2018)
    Architectural fabrics consist of woven base cloth protected by a coating on both sides. Corrosive liquids or vapours may diffuse through the matrix material and corrosion effects on fibres may lead to substantial reduction in mechanical properties. Tensile strength is of most importance for the safety of a structure and strain properties govern its serviceability. Wetting is one of the main environmental impacts. Due to rain, condensation or snow melting cycles, the membrane gets wet. If the fabric under the coating gets wet and to which amount depends on the condition of the covering coating over the lifetime of the architectural structure and on the wicking properties of the fabric material. Water penetration influences the fabric’s properties. How and to what extent is the field of investigations of this article. The influence of water on the tensile strength and the breaking strain of two common architectural fabrics, polyester (PES)/ polyvinylchloride (PVC) and glass/polytetrafluoroethylene (PTFE), are investigated. Virgin and aged materials are examined. © The Author(s) 2018.
    view abstract10.1177/1369433218756005
  • Zelthallen aus PVC-beschichtetem Polyestergewebe nach aktualisierter Normenreihe DIN 18204
    Uhlemann, J. and Stranghöner, N.
    Stahlbau 87 (2018)
    Tents and halls made of PVC-coated polyester fabric according to the updated standard series DIN 18204. The standard series DIN 18204 ”Components for enclosures made of textile fabrics and plastic films (awnings)“ has been extensively reviewed in the last two years. Alongside with updates of normative references, the structure has been fundamentally changed so that the standard can also cover additional textile and plastic structures in new parts to be developed in future. Material specifications have been purified and adapted to new test standards. Moreover, the design concept has been gently revised. The present contribution describes the background, illustrates the changes compared to the previous edition and provides an outlook to the final version. © 2018, Wiley Blackwell. All rights reserved.
    view abstract10.1002/stab.201810618
  • Application of direct tension indicators in preloaded bolted connections
    Schiborr, M. and Stranghöner, N.
    Steel Construction 10 (2017)
    The direct tension indicator (DTI) method is specified in EN 1090-2 as one of the tightening procedures for preloading bolting assemblies to a specified level of preload. As Germany so far has no experience of using the DTI method, recent experimental and theoretical investigations were carried at the Institute for Metal and Lightweight Structures, University of Duisburg-Essen, Germany, with the main focus being the loadbearing behaviour of preloaded bolting assemblies with DTIs under external axial tensile loading. Whereas tension connections employing preloaded bolting assemblies are quite common in Germany, in the UK, for example, bolted connections are preferably designed as shear connections, as far as is known. As a result of the investigations presented below, it can be summarized that, under tensile loading especially, preloaded bolting assemblies with DTIs might suffer from a severe loss of preload – something that should be considered in preloaded bolted connections in which the preload is taken into account in the design of the connections, e.g. in slip-resistant connections, to activate the slip resistance, and in tension connections subjected to fatigue. Based on these investigations, recommendations have been formulated for preloaded bolting assemblies with DTIs under external axial tensile loading. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stco.201710013
  • Insight into the preloading behaviour of bolted assemblies of stainless steel
    Stranghöner, N. and Jungbluth, D. and Afzali, N. and Lorenz, C.
    Stahlbau 86 (2017)
    Insight into the preloading behaviour of bolted assemblies of stainless steel. Preloaded bolted assemblies made of stainless steel are currently not permitted. Nonetheless, the wish of the construction industry exists to carry out these types of connections in special cases for ultimate or serviceability limit state reasons. Generally, preloaded bolted assemblies made of stainless steel are presumed to be subjected to very high preload losses due to relaxation and creep of the bolts and creep of the clamping packages, which is why the actual preloading force remaining in the connection is assumed not to be estimable. Within the scope of the European RFCS research project SIROCO, extensive investigations are currently being conducted on the tightening and preloading behaviour of bolted assemblies made of austenitic and duplex stainless steels. First results from this project show that a targeted attraction of such compounds is quite possible and that the preload losses due to relaxation are far from being as high as presumed. Furthermore, galling of the connections can be avoided by choosing suitable material pairings and lubricants. The present paper will provide an initial insight into the results of the still ongoing project. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stab.201710476
  • Instandsetzung und Verstärkung von Stahlbrücken mit Kategorie-1-Schäden
    Stranghöner, N. and Lorenz, C. and Friedrich, H.
    Stahlbau 86 (2017)
    Retrofitting methods for orthotropic steel deck plates with category-1-damages. Due to a high increase of traffic load during the last decades orthotropic steel deck plates show more and more fatigue damages in the welded connection between longitudinal stiffeners and steel deck plate (category-1-damages). This contribution gives an overview about existing retrofitting methods which have already been applied in pilot projects and currently investigates renovation techniques for retrofitting category-1-damages. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stab.201710501
  • Optimization of the test procedure for slip factor tests according to EN 1090-2
    Stranghöner, N. and Afzali, N. and de Vries, P. and Glienke, R. and Ebert, A.
    Steel Construction 10 (2017)
    Slip-resistant connections are always used when slip and deformation in a bolted connection must be avoided at all costs, e.g. in radio masts and bridges. For some popular surface treatments, slip factors are given in EN 1090-2, the execution standard for steel structures. For those surface conditions not considered in EN 1090-2, the slip factor can be determined experimentally according to Annex G of EN 1090-2. By reviewing slip factor values obtained with the Annex G test procedure and reported in the literature, it becomes obvious that in most cases the slip factors achieved experimentally are not comparable for identical surface conditions. This is potentially caused by different interpretations of the Annex G slip test procedure. As the slip factor is one of the main parameters influencing the bearing capacity of slip-resistant connections, its determination should be on the safe side and not dependent on the various interpretation possibilities of the test procedure itself. For this reason, the optimization of the Annex G test procedure was thoroughly investigated in the European RFCS research project SIROCO, with the final objective being to enhance its reliability. The focus was on investigating the various test parameters such as type of preload measurement, ascertaining the possible slip planes, test speed, position of slip measurement, clamping length, preload level, evaluation of critical slip load and the performance of the extended creep test. The results achieved in these investigations have already been partly implemented in the revision of the current draft version of EN 1090-2. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stco.201710040
  • Preload losses in stainless steel bolting assemblies
    Afzali, N. and Pilhagen, J. and Manninen, T. and Schedin, E. and Stranghöner, N.
    Steel Construction 10 (2017)
    Stainless steel material is a suitable choice for modern steel constructions as it has a high resistance to corrosion combined with high material strength and ductility. Furthermore, its use leads to significant reductions in maintenance. In this frame, bolted connections made of stainless steel components become more and more important to enhance the application of stainless steel not only to small parts of steel structures but also to complex structures. Whereas non preloaded stainless steel bolted connections are already widely used, according to EN 1090-2, the application of preloaded stainless steel bolting assemblies is not allowed unless otherwise specified. If they shall be used, they shall be treated as special fasteners and a procedure test is mandatory. Also EN 1993-1-4 requires that their acceptability in a particular application has to be demonstrated from test results. These restrictions are mainly caused by two facts: firstly, the viscoplastic deformation behaviour of stainless steel which might result in not negligible preload losses in the bolting assemblies themselves and secondly, the gap of knowledge regarding suitable tightening parameters and procedures for stainless steel bolting assemblies to secure a required preload in the bolting assemblies and to avoid galling. To solve these questions, research activities have been carried out in the frame of the European RFCS-research project ”Execution and reliability of slip resistant connections for steel structures using CS and SS“ SIROCO. The present contribution gives an initial insight into the viscoplastic deformation behaviour of stainless steel bolting assemblies which were achieved in SIROCO which shows that preloaded bolted stainless steel connections can be treated similar to those made of carbon steel. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stco.201710041
  • Procedure qualification for the determination of tightening parameters for preloaded bolted connections
    Stranghöner, N. and Jungbluth, D.
    Stahlbau 86 (2017)
    Procedure qualification for the determination of tightening parameters for preloaded bolted connections. DIN EN 1090-2 and DIN EN 1993-1-8/NA define tightening procedures for preloaded bolted assemblies tightened at the nut side by simple use thereof. However, in a multitude of applications, preloaded bolted connections are used, which for example are tightened on the head side, designed as tapped hole connections and/or are to be used several times. In these cases, a procedure test is necessary to determine the tightening parameters. The present paper describes the principal procedure for carrying out such a procedure test, in particular the target level of preloading, the length of thread engagement for components with internal threads, the single and multiple use of components, and the boundary criteria for determining the tightening parameters. Furthermore, the procedure is explained using practical examples. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stab.201710548
  • Prof. Herbert Schmidt on the occasion of his 80th birthday!
    Stranghöner, N.
    Stahlbau 86 (2017)
    view abstract10.1002/stab.201770403
  • Retrofitting methods for orthotropic steel deck plates with category-1-damages
    Stranghöner, N. and Lorenz, C. and Friedrich, H.
    Stahlbau 86 (2017)
    Retrofitting methods for orthotropic steel deck plates with category-1-damages. Due to a high increase of traffic load during the last decades orthotropic steel deck plates show more and more fatigue damages in the welded connection between longitudinal stiffeners and steel deck plate (category-1-damages). This contribution gives an overview about existing retrofitting methods which have already been applied in pilot projects and currently investigates renovation techniques for retrofitting category-1-damages. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stab.201710501
  • SIROCO – Slip-Resistant Connections Made of Carbon and Stainless Steel
    Stranghöner, N.
    Steel Construction 10 (2017)
    view abstract10.1002/stco.201770403
  • Slip-resistant bolted connections of stainless steel
    Stranghöner, N. and Afzali, N. and de Vries, P. and Schedin, E. and Pilhagen, J. and Cardwell, S.
    Steel Construction 10 (2017)
    The use of stainless steel components can lead to a significant reduction of maintenance costs compared to a structure executed in carbon steel. Because of its high material strength, ductility and corrosion resistance stainless steels are becoming more and more popular as a construction material in both building and civil engineering structures. Consequently slip-resistant bolted connections made of stainless steel are becoming more important. Slip-resistant bolted connections are used in joints where slip is not acceptable (because they are subject to reversal of shear load or any other reason) or in joints that are subject to cyclic shear load (to improve the fatigue class of the connecting plates). Existing design codes/standards do not specify slip factors for surface treatments of stainless steel grades, the minimum values of slip factors for common surface treatments/coatings that are specified in EN 1090-2 are exclusively valid for carbon steels. One of the reasons for this is that stainless steel alloys are thought to suffer more than carbon steels from time dependent behaviour (creep and relaxation) at room temperature. This could lead to higher preload losses and consequently to lower slip factors than used for carbon steels with comparable surface treatment. However, no evidence of this can be found in literature. Creep and relaxation are stress dependant phenomena and the stresses in the components of preloaded bolted connections are locally highly non-uniform. Therefore, slip factors of different stainless steel grades have to be determined by experiments to investigate the effects of time dependant material behaviour. In this paper the results of slip factor tests on four stainless steel grades are presented and the influence of surface treatments and the preload level on the slip factor of stainless steel slip-resistant connections is discussed. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stco.201710044
  • Stiffness parameters of fabrics – Standardized for products and project oriented for design
    Uhlemann, J. and Stranghöner, N.
    Stahlbau 86 (2017)
    Stiffness parameters of fabrics – Standardized for products and project oriented for design. For fabrics used in the field of textile architecture or tent structures, the declaration of stiffness parameters by the material supplier as well as the assumption of appropriate stiffness parameters by the design engineer is still a matter of uncertainty. The present contribution discusses possible methods for a standardized determination of stiffness parameters and for a tailored determination for specific structures. Moreover, for PVC-coated polyester fabrics of three strength classes an investigation at random is conducted analyzing whether they can be classified regarding their stiffness parameters. A classification would make a tabulation possible. This would be of great help for the design engineer for choosing appropriate stiffness parameters as input for the structural analysis of fabric structures. The presented results indicate the possibility of a classification for the investigated materials. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stab.201710481
  • Tightening behaviour of preloaded stainless steel bolting assemblies
    Stranghöner, N. and Jungbluth, D. and Abraham, C. and Söderman, A.
    Steel Construction 10 (2017)
    Preloaded bolting assemblies made of stainless steel are currently not permitted in steel structures due to the unknown viscoplastic deformation behaviour as well as the unknown tightening behaviour and tightening procedures for these kinds of bolting assemblies. Nonetheless, the construction industry wishes to carry out these types of connections in special cases, e.g. when special requirements exist with regard to corrosion resistance or for architectural reasons. Generally, the tightening behaviour of carbon steel HR and HV bolting assemblies according to EN 14399-3 and -4 cannot simply be transferred uncritically to stainless steel bolting assemblies due to several reasons. Within the scope of the European RFCS research project SIROCO, extensive investigations are currently being conducted on the tightening and preloading behaviour of EN ISO 4014 and EN ISO 4017 bolting assemblies made of austenitic and duplex stainless steels. First results from this project show that a targeted tightening of such assemblies is in principle possible. Specified preloading levels, e. g. Fp,C* and Fp,C, can be achieved with sufficient reliability using suitable lubricants. Herewith, it is possible to define feasible tightening procedures. Furthermore, it could be shown that these bolting assemblies show sufficient ductility and galling of the assemblies can be for sure avoided. The present paper provides an initial insight into the results of the project. Copyright © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin
    view abstract10.1002/stco.201710038
  • 20. DASt-Forschungskolloquium am 8./9. März 2016 in Essen
    Stranghöner, N.
    Stahlbau 85 (2016)
    view abstract10.1002/stab.201690089
  • Background to the Science and Policy Report for Tensile Membrane Structures
    Stranghöner, N. and Uhlemann, J. and Mollaert, M.
    Procedia Engineering 155 (2016)
    Nowadays, comprehensive design standards for tensile membrane structures exist neither on European level nor in most European countries on national levels. Currently, the development of a European design standard for membrane structures made from technical textiles and foils is under way. One of the first steps towards a new Eurocode for membrane structures is the preparation of a "Science and Policy Report", so-called "SaP-Report". It is published by the Joint Research Centre (JRC). The SaP-Report for the structural design of membranes was drafted by CEN/TC 250/WG5 "Membrane structures", titled "Prospect for European guidance for the Structural Design of Tensile Membrane Structures". This is an important milestone. The SaP-Report will be the basis of discussions and specifications in the process of creating a new standard throughout the next years. This paper gives background on the meaning, structure and content of the SaP-Report as well as the state of the art regarding the code development. © 2016 The Author(s).
    view abstract10.1016/j.proeng.2016.08.027
  • Fatigue behaviour of high frequency hammer peened ultra high strength steels
    Berg, J. and Stranghöner, N.
    International Journal of Fatigue 82 (2016)
    Existing design recommendations for the consideration of high frequency hammer peening (HFHP) are limited to steel grades of S960 and plate thicknesses of 5 mm and higher. The influence of HFHP treatment on the fatigue behaviour of welded ultra high strength steels with yield strengths of 960 MPa and higher - loaded in the upper finite and low cycle fatigue life region - has not been investigated sufficiently so far. For this reason, fatigue tests have been performed on four typical welded notch details of mobile crane structures made of S960, S1100 and S1300 to determine the influence of HFHP on the fatigue strength. The fatigue strength of HFHP treated specimens was at least twice the fatigue strength of the as welded toe condition. A fatigue life improvement due to HFHP treatment can be observed at load cycles of 10,000 and higher. In accordance with existing investigations, the slope of the S-N-line increases to approximately m ∼ 5 due to HFHP treatment if the fatigue cracks start from the treated weld toes. The classification of the test results for the HFHP treated toe condition shows, that fatigue classes (FAT) of existing design proposals are conservative. Further improvements of the proposed FAT classes are possible which shows the potential use of UHSS with steel grades higher than S960 in combination with HFHP treatment. © 2015 Elsevier Ltd. All rights reserved.
    view abstract10.1016/j.ijfatigue.2015.08.012
  • Numerical simulation of the preloading procedure of bolted assemblies considering plastic material behaviour
    Lorenz, C. and Stranghöner, N.
    Stahlbau 85 (2016)
    The load bearing behaviour of a preloaded bolted assembly is mainly influenced by the lubricated mating threads of the bolt and the nut. Especially when parts of a bolted assembly shall be reused and/or consist of different materials, an understanding of the stress distribution in the mating threads and the bolt is of great importance. Typical applications for this kind of connections are blind hole connections in transition joints and bridge bearings where high strength bolts are screwed in cut threads made of mild steel. For the numerical simulation of the preloading procedure a full parametrized 3D finite element model of a bolted assembly was built up and calibrated to experimental results achieved from tightening tests using the institutes own tightening torque testing machine. In the finite element model, the nonlinear material behaviour as well as the realistic coefficients of friction can be taken into account. To assess the reusability of different parts of the bolted assemblies, plastic deformations can be quantified and evaluated. © 2016, Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH and Co. KG, Berlin
    view abstract10.1002/stab.201610390
  • Refined Biaxial Test Procedures for the Determination of Design Elastic Constants of Architectural Fabrics
    Uhlemann, J. and Stranghöner, N.
    Procedia Engineering 155 (2016)
    In today's structural design practice for textile structures, still one of the most challenging aspects is the determination of material stiffness parameters. The only constitutive law used in practice describes orthotropic linear-elastic stress-strain relations in the two principal directions. The elastic constants are "tensile modulus" and "Poisson's ratio". In contrast, the actual stiffness behaviour of architectural textiles is nonlinear and nonelastic. Moreover, the potential high orthotropy of textiles is often not sufficiently covered by the test and evaluation methods available. This paper presents principles for refined biaxial test procedures that fit to the requirements of structural fabrics. As a result, sets of elastic constants for design purposes can be determined which ensure a very good correlation between measured and calculated strain on a specific stress level for all common PVC-coated polyester fabrics and PTFE-coated glass fibre fabrics. Furthermore, the refined method enables to model the very high transverse strains which are observed especially for glass-PTFE fabrics. © 2016 The Author(s).
    view abstract10.1016/j.proeng.2016.08.022
  • Tightening of bolted connections according to Eurocode 3 and DIN EN 1090-2
    Stranghöner, N. and Jungbluth, D. and Hüller, V. and Machura, G.
    Stahlbau 85 (2016)
    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. © 2017 John Wiley & Sons Ltd.
    view abstract10.1002/stab.201610377
  • Verschraubung von aufgeschweißten Gewindebolzen nach Merkblatt DVS 0904
    Stranghöner, N. and Jungbluth, D.
    Stahlbau 85 (2016)
    Tightening of arc welded studs according to the technical bulletin DVS 0904. Within the process of arc stud welding, a pen-shaped threaded or non-threaded stud is connected to a steel component. During the process the two components bolt and steel component are locally melted by an arc and then plunched together. The process of arc stud welding can be divided into arc stud welding with a drawn arc or with condenser discharge. The technical bulletin DVS 0904 of the German Welding Society (DVS) gives next to the rules for arc stud welding in EN ISO 14555 further references for arc stud welding in practical use. Beside rules and references for welding preparation, execution and controlling of arc stud welding, DVS 0904 gives further information on tightening and tensile testing of the installed studs. The given tightening torque and bolt force values for different stud diameters and materials are based on assumptions for coefficients of friction, which were not determined by tightening tests. In the frame of the revision of DVS 0904 these assumptions should be checked. For this reason tightening tests were performed at the Institute for Metal and Lightweight Structures of University of Duisburg-Essen. The experimental investigations and their results are presented as background information for the revision of DVS 0904 within this contribution. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201610386
  • Experimental load bearing behaviour of axially compressed cylinders made of ferritic and duplex stainless steels
    Stranghöner, N. and Gorbachov, A.
    Stahlbau 84 (2015)
    Shell structures made of stainless steels are used e. g. in tank structures and biogas plants. They are fully recyclable, do not need any corrosion protection and therefore, they are valuable in terms of environmental protection and environmental compatibility. However, the design of these shells with regard to their buckling resistance is limited according to DIN EN 1993-1-6 due to the non-linear stress-strain-behaviour of stainless steels. For this reason, additional temperature and slenderness dependent buckling strength reduction factors for axial loaded cylindrical shells made of austenitic stainless steels were already developed by Schmidt and Hautala. The transferability of these buckling strength reduction factors on shell structures made of ferritic and duplex stainless steels will be reviewed in the context of the European RFCS research project BiogaSS by means of experimental, numerical and theoretical studies. The results shall be incorporated in the revision of DIN EN 1993-1-6. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG.
    view abstract10.1002/stab.201510255
  • Fatigue Strength of Marked Steel Components
    Stranghöner, N. and Jungbluth, D.
    Procedia Engineering 133 (2015)
    Steel components have to be identifiable and traceable during the whole manufacturing chain. The choice of the identification method is not specified consistently in international rules and standards. In the European standard for the execution of steel structures EN 1090-2 it is specified that the use of durable marks may not result in producing damages and that hard stamped marks are only permitted for steel grades up to S355 and only in areas where no effect on the fatigue life is expected. In terms of durability and liability, markings should be resistant against particular manufacturing processes such as sandblasting, hot-dip galvanizing or coating. In detail, these methods are hard stamping, scribing, plasma marking and needling. Nowadays the machinery manufacturers have developed machines in which the marking process is automatically integrated in the manufacturing process. However, the effect of the installed notch due to the marking process on the fatigue strength of the components has not been investigated in detail yet. As a result a classification of the notched details in the European detail categories of EN 1993-1-9 is in principle not possible. For these reasons the influence of durable marking methods on the fatigue strength of steel components needs to be clarified by experimental fatigue tests and numerical calculations which are actually performed at the Institute for Metal and Lightweight Structures of University of Duisburg-Essen. The tests should determine the influence of several identification methods on the fatigue strength of structural steel details. Within the investigations the different surface conditions hard stamped, scribed, plasma marked and needled are considered. The fatigue tests are carried out considering three different steel plate thicknesses 15 mm, 25 mm and 40 mm and two different steel grades S355J2 and S460N. © 2015 Published by Elsevier Ltd.
    view abstract10.1016/j.proeng.2015.12.672
  • Slip-resistant connection in towers and masts-testing and coating
    Stranghöner, N. and Afzali, N. and Berg, J.
    Stahlbau 84 (2015)
    Bolted connections in towers and masts are executed as slip-resistant connections of categories B or C according to EN 1993-1-8 when deformations and slip have to be minimized, e. g. in radio masts and towers of wind turbines. The load bearing capacity of slip-resistant connections is mainly influenced by the level of preloading in the bolts and the friction of the faying surfaces - described by the slip factor. The highest possible and over the service life of the structure guaranteed slip resistance is desirable in order to keep the number of bolts and the faying surfaces of the complex and therefore expensive connections low and to meet the demand of the industry for maintenance-free connections. For these reasons, at present, extensive studies on the determination of the slip factor of slip-resistant connections on the basis of EN 1090-2 are carried out as part of the European RFCS research project SIROCO taking into account different preloading levels and coating types. Within the present contribution, first results are presented for alkali zinc silicate coated and zinc spray metallized faying surfaces. © 2015 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201510337
  • Stiffness parameters for architectural fabrics: An analysis of two determination procedures
    Uhlemann, J. and Stranghöner, N. and Saxe, K.
    Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) 25 (2015)
    One important and challenging aspect of the design process for tensile membrane structures is the determination of biaxial material stiffness parameters. Coated textiles that are used as architectural fabrics display highly nonlinear and anisotropic stress-strain behaviour under biaxial tensile stresses. Nevertheless, in state-of-the-art structural analyses, the behaviour of these coated textiles is often simplified to a linear-elastic plane stress relationship, where the elastic constants are "tensile stiffness" and "Poisson's ratio." The elastic constants must be determined for each material using biaxial tensile tests. Several different biaxial test procedures to determine the elastic constants exist worldwide, and these procedures yield various sets of elastic constants with a wide spectrum of stiffness parameters. At the same time, design engineers have no guidelines to assess which set of parameters is appropriate for a specific design situation. This paper compares two different methods of determining stiffness parameters using theoretical and experimental analyses. The variation in structural analysis results due to stiffness parameters that were determined using different techniques is demonstrated using three types of PES/PVC materials from two material producers. Furthermore, this paper provides guidance regarding the manner of evaluation of sets of elastic constants and the modification of the evaluation of experimental biaxial tests, if required. Information is also provided concerning the applicability of the investigated procedures.
    view abstract10.2749/101686614X14043795570291
  • Fatigue behaviour of HFH-treated notch details of mobile crane structures
    Berg, J. and Stranghöner, N.
    Stahlbau 83 (2014)
    In mobile crane structures, ultra high strength fine grained structural steels (UHS) with yield strengths up to 1100 N/mm2 and 1300 N/mm2 respectively are used. The fatigue life of welded notch details which can be classified into the upper finite fatigue life region is critical. One possibility to improve the fatigue behaviour is the application of post weld treatment methods like high frequency hammer peening (HFH). Existing design recommendations for the consideration of HFH are limited to maximum steel grades of S960 and plate thicknesses of 5 mm and higher. The influence of HFH-treatment on the fatigue behaviour of welded ultra high strength steels with yield strengths of 960 N/mm2 and higher - loaded in the upper finite and low cycle fatigue (LCF) life region respectively - has not been investigated sufficiently so far. For this reason, fatigue tests have been performed at four typical welded notch details of mobile crane structures made of S960, S1100 and S1300 to determine the influence of HFH on the fatigue strength. The results of the HFH-treated specimens showed a significant improvement of the fatigue strength in comparison with the as welded toe condition. Furthermore, a fatigue life improvement due to HFH treatment can be observed at loading cycles of 10000 and higher. In accordance with existing investigations, the slope of the S-N-line increases to approximately m ~ 5 due to HFH treatment if the fatigue cracks start from the treated weld toes. The classification of the test results for the HFH-treated toe condition shows, that FAT classes of existing design proposals are conservative. © 2014 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201410180
  • Sustainability of steel constructions of renewables
    Schaumann, P. and Bechtel, A. and Eichstädt, R. and Stranghöner, N. and Berg, J. and Gorbachov, A. and Wagner, H.-J. and Röder, J.
    Stahlbau 83 (2014)
    Mechanical resistance, serviceability and durability are the primary requirements for steel structures of renewable energies. During design and execution, these structures are mainly influenced by economic and technical aspects. Currently, there is a lack of appropriate instruments for a holistic sustainability approach in order to consider sustainability aspects during the stages of design, manufacturing and erection of steel constructions. Based on existing rating systems originating from the building sector, a method for a holistic sustainability assessment of steel structures for renewables has been developed within the research project "NaStafEE". With the help of the sustainability rating system, different types of construction and variants of execution can be compared under consideration of requirements for sustainability aspects. This article deals with the development of the rating system and the exemplary application to steel support structures of offshore wind energy turbines and to steel digesters of biogas power plants. © 2014 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201410169
  • Importance of fictitious elastic constants of textile fabrics on the structural analysis of membrane structures
    Uhlemann, J. and Stranghöner, N.
    Stahlbau 82 (2013)
    Architecturally ambitious lightweight structures made from spatially curved textile membranes are increasingly used, e. g. for roofing of stadia or big halls. The curvature gives geometric stiffness. However, a trend to structures with small curvature can currently be recognised. This trend decreases the importance of the geometric stiffness and highlights the importance of the material stiffness at the same time. Today, the highly nonlinear material behavior of coated fabrics is roughly been modeled linear-elastic. As a consequence of a lack of consistent rules for the determination of fictitious elastic constants, a great variety of stiffness values can be obtained. In the structural analysis this leads to a spectrum of resulting stresses for the membrane and the primary steel structure. The aim of the presented paper is to illustrate this problem exemplary for a typical membrane structure and to sensitize the structural engineers for that issue. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201310086
  • Slip-resistant connections according to Eurocode 3 and DIN EN 1090-2
    Stranghöner, N. and Schiborr, M. and Glienke, R. and Wanner, M.-C. and Ulbrich, D.
    Stahlbau 82 (2013)
    Slip-resistant connections in steel structures permit bolted connections with low slip and deformation, which are mainly used in structures, in which deformations of the connections would limit the serviceability of the structures. Typical applications can be found in radio masts, bridges and towers of wind turbines, which are loaded by fatigue. Essential characteristics of these connections are the slip factor and the preload in the bolts. The new execution standard for steel structures, DIN EN 1090-2, provides in contrast to DIN 18800-7 the possibility of considering different surface treatments by various classes and with Annex G, it provides a detailed test method to determine the slip factor taking into account possible creep effects. The differences in the testing methodology in comparison to the TL/TP-KOR- Stahlbauten are in the details and can lead to unfavourable slip factors. © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201310098
  • Sustainability assessment for load carrying steel constructions of renewables - Development of methods and application examples
    Stranghöner, N. and Berg, J. and Gorbachov, A. and Schaumann, P. and Bechtel, A. and Eichstädt, R. and Wagner, H.-J. and Baack, C. and Lohmann, J.
    Stahlbau 82 (2013)
    The upcoming installation of renewables in Germany is already politically established. Especially under consideration of sustainability aspects, the structural systems of renewables are very important. Rating systems for sustainability exist only for buldings but not sufficient for application in structural engineering. For a sustainable energy supply sustainability aspects should be considered during design and execution of structures of renewables. This article addresses the development of methods for sustainability assessment of load carrying steel structures of renewables. The described method is applied exemplary for the environmental sustainabilty assessment of a steel digester of a biogas power plant. With the help of the sustainability rating system, different construction methods can be compared under consideration of sustainability aspects. Furthermore, the method can be utilized as a help for a decision in order to fulfill sustainability requirements. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201201642
  • Choice of the steel grade according to DIN EN 1993-1-10
    Stranghöner, N. and Kühn, B.
    Stahlbau 81 (2012)
    As part of the Eurocode 3-family, DIN EN 1993-1-10 is responsible for sufficient selection of steel grades to avoid brittle fracture and lamellar tearing. The regulations of DIN EN 1993-1-10 are almost identical to the well known rules of the national DASt guidelines 009 and 014, so that there are only minor changes for the user. The choice of the steel grade to avoid brittle fracture is based on a fracture mechanics approach, in which the fracture toughness of the material considers a correlation to the notched impact strength requirements specified in the product standards. DIN EN 1993-1-10 allows three methods of verification, where normally the simple proof of the choice of permissible plate thickness using a standardized table comes into play. The proof of adequate fracture toughness in the through-thickness direction to avoid lamellar tearing can be done basically in two ways: the traditional way to DASt guideline 014 on the definition of a required Z-grade prior to ordering of the material or the possibility of testing the already fabricated steel components whether lamellar tearing has occurred. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
    view abstract10.1002/stab.201201543
  • Sustainability assessment for steel constructions of renewables
    Schaumann, P. and Bechtel, A. and Wagner, H.-J. and Baack, C. and Lohmann, J. and Stranghöner, N. and Berg, J.
    Stahlbau 80 (2011)
    The consideration of sustainability gets more important to society aspects. Sustainable Systems that eliminate ecologic and economic effects on future generations are preferred. Especially in civil engineering this Convention gains importance. Up-to-date established and approved assessment Systems to evaluate and quantify the sustainability of constructions regard only buildings. With respect to the change of energy sources from fossil to renewable, the constructions for renewables should fulfil sustainable criteria. Therefore this article establishs a rating system regarding sustainability for steel structures of renewable energies. The approach as well as preliminary results considering ecological effects of offshore wind energy support structures are given. Indicators derived from the building sector are presented. Beside the wind energy, the focus is set to biogas plants.
    view abstract10.1002/stab.201101475
  • The use of hot-finished hollow sections with wall thicknesses up to 20 mm at low temperatures
    Stranghöner, N. and Krampen, J. and Lorenz, C.
    Stahlbau 80 (2011)
    In Europe, hot-finished hollow sections according to DIN EN 10210 are mainly used with wall thicknesses up to 20 mm and steel grade S355J2H which is normally in stock at the steel suppliers. A recurring question concerns the usability of those hollow sections at low temperatures due to the test temperature of impact toughness at-20 °C set in the product standard: Is a steel grade S355J2H applicable below -20 °C service temperature, or should, by security considerations, rather a higher-quality steel be used? This paper describes the toughness behaviour of hot-finished hollow sections based on experimental studies and explains the relationship between the required impact toughness in the product standards at a defined test temperature and the fracture mechanics based concept for the choice of steel material of DIN EN 1993-1-10. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG.
    view abstract10.1002/stab.201101449
  • fatigue

  • mechanical properies

  • membranes

  • steel

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