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Buckling behaviour of axially and circumferentially loaded cylindrical shells made of high‐strength steels In the past, shell structures have largely been made of mild steels or austenitic stainless steels. However, high‐strength duplex stainless steels acc. to DIN EN 10088‐4, ‐5 are increasingly being used, e. g. in biogas fermenters. The use of high‐strength steels and duplex stainless steels not only reduces steel consumption and production costs, but also assembly costs, and thus significantly increases the competitiveness of tanks and silos in steel construction compared to containers made of other construction materials, e. g. concrete. One prerequisite, however, is that the problem of stability failure in the form of shell buckling can be eliminated. The European design standards for shell structures EN 1993‐1‐6, ‐4‐1, ‐4‐2 are developed for mild steels and do not take into account strength verification formats for ring‐stiffened and axially stiffened circular cylindrical shells for high‐strength structural steels and stainless steels with a nonlinear material behaviour below the 0.2 % yield strength. For this reason, within the framework of the IGF research project no. 21719N "Load‐bearing behaviour of meridionally and ring stiffened tanks and silos made of high strength (duplex) steels and low‐temperature steels for pressure vessels", systematic investigations are carried out on (un‐)stiffened circular cylindrical shells at the Institute of Metal and Lightweight Structures at the University of Duisburg‐Essen and the Testing Institute for Steel, Wood and Stone at the Karlsruhe Institute of Technology. The first results of this research project are presented here. [ABSTRACT FROM AUTHOR]

The application of duroplastic gap filling material DIAMANT MM1018 in preloaded bolted connections In steel construction, bolted connections are preloaded either for load‐bearing capacity reasons or for serviceability reasons. Single and multi‐section connections of wind turbines, offshore plants, bridges etc. are typical application examples. Gap formation, caused by imperfections due to fabrication and assembly, poses a risk e. g. for the controlled application of the required preload level as well as for the prevention of cavity corrosion. This can significantly impair the load‐bearing capacity and the durability of the connection and even lead to a premature failure. Therefore, the formation of gaps must be kept to a minimum, whereby DIN EN 1090‐2 provides possible measures such as the use of packing plates for this purpose. Two‐component reaction resin systems based on epoxy resins, which are filled with special metallic materials to improve the mechanical properties, are a possible alternative for gap filling. Within the framework of the ZIM cooperation project "Bri‐San‐T – DuroFüllSta", systematic investigations were carried out into the use of the gap‐filling material MM1018 of the company Diamant Polymer GmbH for use in preloaded bolted connections. In this contribution, experimentally determined slip factors as well as the expected preload losses over the service life are presented and discussed. [ABSTRACT FROM AUTHOR]

Slip‐resistant connections with imperfections Slip‐resistant connections are traditionally used in steel and plant structures whenever slip and deformation in the bolted connections must be minimized. The current test procedure according to EN 1090‐2, Annex G is limited to the basic load‐bearing behaviour under laboratory conditions. For the industry, important questions are to which extent production‐, assembly‐ and operation‐related influences have to be considered in the design of slip‐resistant connections, as they affect the economic efficiency of this type of connection. In the frame of the IGF research project 19749 BG "Influence of manufacturing‐ and assembly‐related imperfections on the bearing behaviour of bolted slip‐resistant connections in steel structures" carried out by the Institute for Metal and Lightweight Structures (IML) of the University of Duisburg‐Essen in cooperation with Fraunhofer Institute for Large Structures in Production Engineering (IGP), Rostock and Institute for Corrosion Protection Dresden GmbH (IKS), systematic investigations into slip‐resistant connections of categories B/C according to EN 1993‐1‐8 were carried out. Herein, reference tests were conducted without imperfections and then compared with connections with artificial imperfections. Based on the test results, the influence of different imperfections on the load‐bearing behaviour of slip‐resistant connections in steel construction could be determined. [ABSTRACT FROM AUTHOR]

New design rules for bolted connections made of stainless steel The tensile/shear behaviour of stainless steel bolts is significantly influenced by their specific material properties (non‐linearity, strain hardening). However, this is currently only taken into account to a limited extent in the design. Essentially, the design according to EN 1993‐1‐4 is based on regulations of EN 1993‐1‐8, which were derived for bolts made of carbon steel. At national level, the shear capacities of stainless austenitic bolts have already been designed differently, based on a few investigations. For duplex stainless bolts, there have been no specific regulations at all so far. Within the framework of the IGF research project no. 20651 N "Development of a normative basis of the load bearing capacity of bolted connections loaded in shear and tension made of austenitic and austenitic‐ferritic (duplex) stainless steel M12 to M36", experimental and numerical investigations as well as statistical evaluations according to EN 1990 on the tensile, shear and combined tensile‐shear load‐bearing capacity of bolts made of stainless steel were carried out systematically for the first time. The results have currently been implemented into the revision of EN 1993‐1‐4. In addition, the bearing resistance of stainless steel plates was investigated. Ultimately, the new regulations lead to a more economical design of bolted connections made of stainless steel. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hot spot stress on circular hollow section joints – methods in comparison For the assessment of the fatigue strength of tubular joints, the structural stress concept is predominantly used. The structural stress can be determined using various methods. In this regard, the surface extrapolation method is mainly applied. Accordingly, this procedure is well established in normative specifications. In the frame of this contribution, in addition to this approach, the concept of through‐thickness linearization is elucidated, as only less detailed application guidelines are provided in the relevant standards. Furthermore, an alternative approach is presented, which in principle allows a direct extraction of structural stresses from the computational model. In order to assess the comparability and the validity of this methods, investigations were conducted on K‐, Y‐, and KK‐joints. The results are subsequently compared. [ABSTRACT FROM AUTHOR]

More economical and statistically verified design approaches for carbon steel bolts are presented based on an extensive literature review and own systematical experimental investigations into the tension, shear and interaction resistance of carbon steel bolts conducted at the Institute for Metal and Lightweight Structures of the University of Duisburg-Essen, Germany. Herein, reliability analyses according to EN 1990, Annex D were carried out and confirmed that an increase of the reduction factor to k 2 = 1.0 for the tension resistance F t,Rd is in principle possible. Regarding the shear resistance of carbon steel bolts, simplified but more economical shear coefficients a independent of the position of the shear plane are proposed. Finally, newly design equations for the interaction resistance of carbon steel bolts are proposed, which are in line with the new interaction formulations developed by Stranghöner/Abraham and implemented in prEN 1993–1-4 and abZ/abG Z-30.3-6 for stainless steel bolts. The new interaction concept provides a more economical design compared to EN 1993–1-8/prEN 1993–1-8 and serves to harmonise the European design rules between carbon and stainless steel. [Display omitted] • Various experimental investigations are not included in EN 1993–1-8/prEN 1993–1-8. • Experimental studies and a literature review on bolts have been carried out. • Reliability analyses were conducted to prove g M2 = 1.25 for connections. • More economical design rules compared to EN 1993–1-8/prEN 1993–1-8 were developed. • Harmonisation of the European design rules between carbon and stainless steel bolts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. • Finite element models of stainless steel shells were developed and validated with experimental tests. • Numerical parametric studies were performed to investigate the effect of material nonlinearity on the buckling resistance. • Buckling correction factors were determined depending on the material nonlinearity, the fabrication tolerance class. • Geometric imperfections partly superimpose the effect of the material nonlinearity. • New analytical models were developed to determine the buckling reduction factor for critical shell slendernesses. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Results of slip factor tests on four stainless steel (SS) grades with different surface treatments are presented. • Slip factors for different SS grades are proposed for a future implementation in the next revision of EN 1090-2. • Comparable high slip factors μ > 0.4/0.5 are obtained for different uncoated grit-blasted stainless steel grades. • Highest slip factor was achieved for thermal aluminium spray metalized faying surfaces. • A higher preload level leads to higher slip factors for uncoated and lower slip factors for coated SS surfaces. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Relaxation behaviour of preloaded stainless steel (SS) bolted connections has been investigated. • 47 different series of bolted connections were tested including stainless and carbon steel bolted connections. • Preload losses are mainly due to the embedment of the surfaces and viscoplastic deformation of the bolting assemblies. • Preloaded SS bolted connections can be treated similar to those made of carbon steel with regard to preload losses. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Abstract: Tragwerke aus nichtrostendem Stahl kommen mehr und mehr zum Einsatz. Die aktuelle Bemessungsnorm zu nichtrostenden Stählen der Eurocode 3‐Familie, DIN EN 1993‐1‐4, kann nun, nachdem auch der Nationale Anhang hierzu letztes Jahr veröffentlicht wurde, angewendet werden. In diesem Zusammenhang wurden im Rahmen des europäischen RFCS‐Dissemination Projekts PUREST die Bemessungshilfen zu nichtrostenden Stählen im Bauwesen aktualisiert und stehen den Anwendern zusammen mit einer Kommentierung, online nutzbarer Bemessungssoftware sowie einem Webinar als Hilfestellungen zur kostenlosen Verfügung. Diese Hilfestellungen liefern Erläuterungen und ermöglichen den Ingenieuren aus der Praxis ein größeres Verständnis der Anwendungs‐ und Ausführungsregeln zur Auslegung und Konstruktion von Tragwerken aus nichtrostendem Stahl. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The current design rules in EN 1993-1-4 for non-preloaded stainless steel bolted connections under pure shear and tension are essentially based on the regulations for carbon steel bolted connections. Furthermore, the load bearing behaviour under combined tension and shear (category A + D bolted connections) was adopted from EN 1993-1-8 as well. Recent research activities within the German IGF research project "Load-bearing capacity of bolted connections loaded in shear and tension made of stainless steel M12 to M36" (P 1386/IGF-No. 20651 N) showed that stainless steel bolting assemblies behave different. Herein, systematic experimental investigations and an extensive literature review into the shear, tension and interaction resistance of stainless steel bolts were conducted. Furthermore, reliability analyses according to EN 1990, Annex D were accomplished to prove the partial safety factor of γ M2 = 1.25 for connections made of stainless steel bolting assemblies. The results regarding the shear resistance have already been presented in a former paper in this journal. In these investigations, it could be shown that an increase of the tension resistance F t,Rd with k 2 = 1.0 is in principle possible following the normative regulations of EN ISO 3506-1 regarding the minimum ultimate tensile strength as well as North American ANSI/AISC 360 and Australian Standard AS 4100. Furthermore, a new interaction approach for both unthreaded and threaded part of the bolt lying in the shear plane could be proposed which has statistically been verified for all property classes with γ M * < γ Μ2 = 1.25. The new regulations have already been implemented in the current revision of EN 1993-1-4. The background for the new regulations is presented in this contribution. [Display omitted] • Revised design rules for the tension/interaction resistance of stainless steel bolts for implementation in EN 1993-1-4. • Literature review and own experimental investigations of the tension/interactionresistance of stainless steel bolts. • Deviating load bearing behaviour between bolting assemblies made of stainless steel and carbon steel. • Reliability analysis acc. to EN 1990 to prove the applicability of γ M2 = 1.25 for bolted connections. • New design rules regarding the tension/interaction resistance of stainless steel bolts are proposed for a more economical design. [ABSTRACT FROM AUTHOR]

Das Verständnis des Tragverhaltens in gepaarten Gewinden von Schraubverbindungen ist besonders dann von speziellem Interesse, wenn einzelne Komponenten von Schraubverbindungen mehrfach verwendet werden sollen und/oder diese Komponenten aus unterschiedlichen Werkstoffen bestehen. Um eine prinzipielle Aussage über die Eignung zur Mehrfachverwendung von ausgewählten Verschraubungsdetails treffen zu können, werden am Institut für Metall- und Leichtbau der Universität Duisburg-Essen derzeit umfangreiche experimentelle und numerische Untersuchungen zum Anziehverhalten von Schraubverbindungen durchgeführt. Zur numerischen Simulation des Anziehverhaltens von Schraubverbindungen wurde hierzu unter anderem auch ein vollständig parametrisiertes 3D-Finite-Elemente-Modell entwickelt und an Versuchsergebnissen kalibriert. Hierbei wurden sowohl die am institutseigenen Anziehprüfstand ermittelten Teilreibungszahlen als auch das plastische Materialverhalten berücksichtigt. Erste numerische Berechnungen zeigen, dass sich das Anziehverhalten von hochfesten Schrauben unter Berücksichtigung des plastischen Materialverhaltens prinzipiell simulieren lässt. Für die Bewertung der Wiederverwendbarkeit lassen sich plastische Dehnungen während des Anziehvorgangs quantifizieren und bewerten. Numerical simulation of the preloading procedure of bolted assemblies considering plastic material behaviour. 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. [ABSTRACT FROM AUTHOR]

Beim Lichtbogenbolzenschweißen wird ein stiftförmiges Verbindungselement mit oder ohne Gewinde mittels eines Lichtbogens mit einem Bauteil verbunden. Verwendet werden in der Regel Verbindungsmittel wie Stifte, Buchsen und Bolzen mit Gewinde. Während des Schweißprozesses wird ein Lichtbogen an der Stirnfläche des zu verschweißenden Bolzens gezündet, wodurch sowohl die Stirnfläche des Bolzens als auch das Werkstück lokal angeschmolzen und unter einem definierten Anpressdruck zusammengefügt werden. Unterschieden wird zwischen zwei Verfahren der Schweißung, dem Lichtbogenbolzenschweißen mit Hub- oder mit Spitzenzündung. Das Merkblatt DVS 0904 des Deutschen Verbands für Schweißen und verwandte Verfahren e.V. (DVS) gibt neben den Regelungen zum Lichtbogenschweißen von metallischen Werkstoffen der DIN EN ISO 14555 weiterführende Hinweise zum Lichtbogenbolzenschweißen für die Praxis. Für das Bolzenschweißen werden unter anderem Anweisungen für die Schweißvorbereitung, die Ausführung und die Prüfung der Bolzenschweißung gegeben. Darüber hinaus liefert das Merkblatt aber auch Angaben zur Montage und damit zur Verschraubung sowie zur Zugprüfung von aufgeschweißten Gewindebolzen. Diese Angaben betreffen das Montagedrehmoment und die resultierende Montagevorspannkraft, die auf Annahmen zu Reibbeiwerten beruhen, welche bisher nicht durch Versuche gestützt wurden. Im Zuge der Überarbeitung des Merkblatts DVS 0904 sollten diese Angaben überprüft und angepasst werden, weshalb experimentelle Untersuchungen an aufgeschweißten Gewindebolzen am Institut für Metall- und Leichtbau der Universität Duisburg-Essen durchgeführt wurden. Diese Untersuchungen und deren Ergebnisse werden im vorliegenden Beitrag als Hintergrundinformationen zu den in der überarbeiteten DVS 0904 ausgewiesenen Anziehdrehmomenten dargestellt und erörtert. 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. [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]

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. [ABSTRACT FROM AUTHOR]

Schraubenverbindungen im Turm- und Mastbau werden immer dann als gleitfest vorgespannte Verbindungen der Kategorien B oder C nach DIN EN 1993-1-8 ausgeführt, wenn die Verformungen und der Schlupf in den Verbindungen minimiert werden müssen, wie zum Beispiel bei Funkmasten und Türmen von Windenergieanlagen. Wesentliche Einflussparameter auf die Tragfähigkeit einer gleitfesten Verbindung sind die Höhe der Vorspannkraft in den Schrauben und die Reibeigenschaften der gepaarten Oberflächen - beschrieben durch die Haftreibungszahl. Ein möglichst hoher und über die Lebensdauer der Struktur garantierter Gleitwiderstand ist wünschenswert, um die Anzahl der Schrauben und die Flächen der aufwändig und damit kostenintensiv herzustellenden Verbindungen gering zu halten und der Forderung der Industrie nach wartungsfreien Verbindungen nachzukommen. Aus diesen Gründen erfolgen derzeit umfangreiche Untersuchungen zur Ermittlung der Haftreibungszahl gleitfester Verbindungen auf Basis der DIN EN 1090-2 im Rahmen des europäischen RFCS-Forschungsvorhabens SIROCO unter Berücksichtigung unterschiedlicher Vorspannkraftniveaus und Beschichtungsarten, die im vorliegenden Beitrag auszugsweise am Beispiel von Alkali-Zink-Silikat beschichteten und spritzverzinkten gleitfesten Oberflächen vorgestellt werden. Slip-resistant connection in towers and masts - testing and coating. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Im Mobilkranbau werden ultrahochfeste Feinkornbaustähle mit Streckgrenzen von bis zu 1100 bzw. 1300 N/mm2 eingesetzt. Kritisch ist das Ermüdungsverhalten der geschweißten Kerbdetails, die hauptsächlich im oberen Zeitfestigkeitsbereich beansprucht werden. Eine Möglichkeit, die Lebensdauer zu erhöhen, stellt der Einsatz von Schweißnahtnachbehandlungsmethoden wie beispielsweise das höherfrequente Hämmern (HFH) dar. Bestehende Bemessungsvorschläge zur Erfassung von HFH berücksichtigen lediglich Stahlsorten bis maximal S960 und Blechdicken größer gleich 5 mm. Der Einfluss einer HFH-Behandlung auf das Ermüdungsverhalten geschweißter, ultrahochfester Stähle mit Streckgrenzen von 960 N/mm2 und höher im oberen Zeit- bzw. im Kurzzeitfestigkeitsbereich ist bisher nicht hinreichend abgedeckt. An vier kranbautypischen Kerbdetails aus S960, S1100 und S1300 wurden Ermüdungsversuche zur Erfassung des Einflusses von HFH durchgeführt. Im Vergleich zum unbehandelten Nahtzustand konnten infolge einer HFH-Behandlung signifikant höhere Ermüdungsfestigkeiten sowie Lebensdauersteigerungen ab einer Lastwechselzahl von etwa 10 000 festgestellt werden. In Übereinstimmung mit existierenden Untersuchungen flacht die Wöhlerlinie infolge einer HFH-Behandlung auf etwa m ~ 5 ab, wenn die Ermüdungsrisse von den behandelten Nahtübergangskerben ausgehen. Die Einordnung der Versuchsergebnisse für den HFH-behandelten Nahtzustand in vorhandene Bemessungsansätze zeigt, dass die Kerbfallklassen aller Bemessungsansätze konservativ sind. Fatigue behaviour of HFH-treated notch details of mobile crane structures. 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. [ABSTRACT FROM AUTHOR]

Gleitfeste Verbindungen im Stahlbau ermöglichen schlupf- und verformungsarme geschraubte Anschlüsse, die vorwiegend in Konstruktionen zum Einsatz kommen, in denen ungewollte Verformungen innerhalb der Verbindungen die Gebrauchseigenschaften der Tragwerke einschränken würden. Typische Einsatzgebiete stellen beispielsweise Funkmasten und ermüdungsbeanspruchte Brücken oder Türme von Windenergieanlagen dar. Wesentliche Kenngrößen derartiger Verbindungen sind die Haftreibungszahl und die Höhe der Vorspannung in den Schrauben. Die neue Herstellungsnorm für Stahlbauten, die DIN EN 1090-2, bietet im Gegensatz zur DIN 18800-7 die Möglichkeit der Berücksichtigung verschiedener Arten von Oberflächen und Oberflächenvorbereitungen über unterschiedliche Gleitflächenklassen und stellt mit dem Anhang G ein detailliertes Prüfverfahren zur Ermittlung der Haftreibungszahl unter Berücksichtigung der Kriechgleitneigung zur Verfügung. Die Unterschiede in der Prüfmethodik im Vergleich zur TL/TP-KOR-Stahlbauten liegen im Detail und können zu ungünstigeren Haftreibungszahlen führen. Slip-resistant connections according to Eurocode 3 and DIN EN 1090-2. 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. [ABSTRACT FROM AUTHOR]

Architektonisch anspruchsvolle Leichtbaustrukturen aus räumlich gekrümmten textilen Gewebemembranen werden zunehmend eingesetzt, vor allem wenn große Flächen stützenfrei zu überdachen sind, wie z. B. in Stadien oder großen Hallen. Die räumliche Krümmung gibt der Membrane geometrische Steifigkeit. Trotzdem zeigt sich ein Trend zu immer weniger gekrümmten Membranen. Dadurch nimmt die Bedeutung der geometrischen Steifigkeit für die Spannungen und Verformungen von Membrantragwerken ab, während gleichzeitig die Bedeutung der Materialsteifigkeit zunehmend ins Blickfeld gerät. Das hochgradig nichtlineare anisotrope Materialverhalten beschichteter Gewebemembranen wird bei der Berechnung komplexer Membranstrukturen grob vereinfacht linear-elastisch angenommen. Da einheitliche Regelungen zur Bestimmung fiktiver elastischer Konstanten fehlen, ergibt sich ein großes Spektrum an Werten, das einen erheblichen quantitativen Einfluss auf die rechnerische Beanspruchung der Membrane und der stählernen Primärstruktur haben kann. Ziel dieses Beitrags ist es, diese Problematik beispielhaft an einer typischen Membranstruktur zu verdeutlichen und die Tragwerksplaner dafür zu sensibilisieren. Importance of fictitious elastic constants of textile fabrics on the structural analysis of membrane structures. 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. [ABSTRACT FROM AUTHOR]

Der Ausbau Erneuerbarer Energien in Deutschland ist politisch verankert. Insbesondere unter dem Aspekt der Nachhaltigkeit spielen die zugehörigen baulichen Anlagen eine wichtige Rolle. Bewertungssysteme zur Nachhaltigkeitsquantifizierung von baulichen Anlagen existieren zwar auf dem Gebäudesektor, jedoch nicht ausreichend für die Anwendung bei Ingenieurbauwerken. Im Zuge einer nachhaltigen Energieversorgung liegt es nahe, Nachhaltigkeitsaspekte bereits während der Planung und Ausführung von Anlagen zur Gewinnung Erneuerbarer Energien zu berücksichtigen. Der Beitrag behandelt die Entwicklung einer Methodik zur Nachhaltigkeitsbewertung von tragenden Stahlkonstruktionen Erneuerbarer Energien. Die Anwendung der Methodik erfolgt exemplarisch im Rahmen einer ökologischen Nachhaltigkeitsbewertung am Beispiel eines Baustahlfermenters einer Biogasanlage. Die entwickelte Methodik erlaubt einen Vergleich unterschiedlicher Bauweisen und Ausführungsvarianten in Bezug auf nachhaltigkeitsbezogene Gesichtspunkte und dient als Entscheidungshilfe unter Berücksichtigung von Anforderungen an eine nachhaltige Bauweise. Sustainability assessment for load carrying steel constructions of renewables - Development of methods and application examples. 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. [ABSTRACT FROM AUTHOR]

The current design rules in EN 1993-1-4 for non-preloaded stainless steel bolted connections under pure shear and tension (specified as category A and category D connections acc. to EN 1993-1-8) are essentially based on the regulations for carbon steel bolted connections. However, bolts made of stainless steels have in principle a different load bearing behaviour compared to carbon steel bolts and should be investigated systematically and considered in the design rules. For this reason, research activities have been carried out within the German research project "Load-bearing capacity of bolted connections loaded in shear and tension made of stainless steel M12 to M36" (IGF-No. 20651 N). Herein, experimental investigations and a literature review into the load bearing behaviour under pure tension and single-shear has been carried out to evaluate the resulting shear coefficients α for austenitic and duplex stainless steel bolts of property classes 50 to 12.9 as a basis for implementation in the revision of EN 1993-1-4. Furthermore, a reliability analysis according to EN 1990, Annex D has been carried out to prove the partial safety factor of γ M2 = 1.25 for connections. On this basis, new shear coefficients α could be proposed which allow a more economical design of non-preloaded bolted shear connections. [Display omitted] • Revised design rules for shear bearing resistance of bolting assemblies made of stainless steel for implementation in EN 1993-1-4. • Literature review and own experimental investigations regarding the shear load bearing behaviour of stainless steel bolts. • Deviating load bearing behaviour of bolting assemblies made of stainless steel compared to that of bolting assemblies made of carbon steel. • Reliability analysis acc. to EN 1990 to prove the applicability of γ M2 = 1.25 for bolted connections. • New shear coefficients α could be proposed for a more economical design. [ABSTRACT FROM AUTHOR]

Design and execution of membrane structures according to prCEN/TS 19102 This paper reflects the progressive development of the first European design standard for membrane structures. It will be published in future as CEN/TS 19102 "Design of tensioned membrane structures". In addition to design rules, it will also contain interim execution rules based on the design concept. The current status of the planned regulations in these two areas is presented in this article. [ABSTRACT FROM AUTHOR]

Beside their high mechanical strength, duplex stainless steels are a suitable choice in highly corrosive environments. These types of steels are used in steel bridges more and more frequently exposed to low temperatures and fatigue loads. However, for low temperature applications, it must be guaranteed that brittle fracture is avoided since duplex stainless steel shows a toughness-temperature relationship similar to that of carbon steel. For this reason, in the frame of the German national FOSTA research project "P 1390", comprehensive investigations have been started into the material selection of duplex stainless steel to avoid brittle fracture considering the fracture mechanic based background of EN 1993-1-10. For this purpose, Charpy-V impact tests and fracture toughness tests have been systematically carried out for various duplex stainless steels in order to create the basis for the development of toughness requirements for new duplex classes. The validity of the already existing Master Curve concept and the applicability of the transition temperature correlation for duplex stainless steels based on experimental fracture toughness and Charpy-V impact tests have been investigated. The aim of this contribution is to present first results of these investigations. • A comprehensive investigation has been started and first results are presented based on Charpy-V impact and fracture toughness tests. • The highest nickel content in 1.4462 resulted in the lowest transition temperature followed by lean duplex 1.4662 and 1.4162. • The 3 °C temperature shift per percent of cold deformation in transition curve according to EN 1993-1-10 appears suitable for tested duplex steels. • Lower fracture toughness values are achieved for the specimens fabricated from thicker plates for both duplex 1.4462 and lean duplex 1.4162. • The results confirm that the transition temperature correlation in accordance with EN 1993-1-10 is valid for the studied duplex stainless steels. • The Master Curve approach presented in ASTM E1921 which was developed for carbon steel material is also valid for the tested duplex stainless steels. [ABSTRACT FROM AUTHOR]

The execution of preloaded stainless steel bolting assemblies is currently only permitted according to EN 1090-2 if procedure tests are carried out. Nevertheless, it has be shown in various previously and recently conducted studies that preloading of bolting assemblies and threaded rods made of stainless steel is in principle feasible and that reliable tightening procedures can be developed. Thus, there is an urgent need for clear guidance and normative implementation as EN 1090-2 does not give any procedure to qualify these bolting assemblies for preloading. This paper aims to present background information on the Bolt Tightening Qualification Procedure (BTQP) for stainless steel bolting assemblies, which was already implemented in the recently drafted ISO 17607-6. • EN 1090–2 only permits the use of stainless steel if procedure tests are carried out. • EN 1090–2 does not give any guidance on how to perform procedure tests. • The Bolt Tightening Qualification Procedure (BTQP) BTQP does give guidance on how to qualify bolting assemblies for preloading. • The BTQP covers the initial parameters, determination of tightening parameters as wells as inspection requirements. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Mechanical‐technological behaviour of ETFE foils and their welded connections The thermoplastic fluoropolymer ethylene/tetrafluoroethylene, ETFE, has been increasingly used in membrane structures in the construction industry since the 1980s. The plastic ETFE exhibits a nonlinear, viscoelastic material behaviour that has not yet been fully investigated. However, when building membrane structures with ETFE foils, knowledge of the nonlinear, viscoelastic material behaviour is essential in order to be able to build wide, open and at the same time safe and economical structures. The material behaviour can be divided into short‐term tensile behaviour and long‐term behaviour, both under monoaxial and biaxial stresses. For the assembly of the surface structures, welding of the individual cut length is essential, since the basic material is only available in limited product widths. So far, there have only been a few studies on the load‐bearing behaviour of welded ETFE foils. This article provides a brief overview of the material behaviour of ETFE foils in short‐term tensile tests as well as long‐term tests in monoaxial and biaxial stress conditions. In addition, material models are presented which describe the material behaviour in the above‐mentioned tests or stress‐states. Furthermore, first insights into the fracture behaviour of welded ETFE foils are given. [ABSTRACT FROM AUTHOR]

Use of twin girder auxiliary bridges in the course of an emergency project for crossing the BAB 40 On 2020/09/17 a damaged fuel tanker completely burnt‐out under a railway bridge over the German motorway A 40 between Duisburg and Mülheim a. d. R. Three out of five bridges had been damaged by the extremely high temperature that the structural and transport safety could no longer be ensured. Therefore the affected railway tracks of the DB Netz AG had to be shut. Immediately after the recording of damages, one bridge structure had been demolished. Due to the immediate detailed design for the replacement and the DB‐internal as well as the governmental approvals the erection of the complete structure, including foundations, auxiliary bridges and rail system could be realized in a minimum amount of time. The initial operation of the bridges took place on 2020/12/28 (bridge 3) and 2012/09/06 (bridges 2, 4). Only by the use of twin‐girder‐auxiliary‐bridges type ZH26 of the DB Netz AG the short‐term replacement of the damaged bridges could be realized. Subsequent the whole building process is described. The available auxiliary‐bridge‐systems of the DB Netz AG and their limitations of use are summarized additionally. The use of the auxiliary‐bridges as a structural chain as well as the use as permanent makeshift require DB‐internal approvals. The required verifications, especially fatigue design, and the therefore required expertise for the durability of the bolted connections are described as well. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Tragfähigkeit, Gebrauchstauglichkeit und Dauerhaftigkeit sind die primären Anforderungen, die an Stahlkonstruktionen regenerativer Technologien gestellt werden, so dass die Auslegung und Errichtung dieser Konstruktionen vorwiegend durch monetäre und technische Gesichtspunkte beeinflusst wird. Zur Berücksichtigung von Nachhaltigkeitsaspekten aufseiten der Planung, Herstellung und Fertigung von Stahlkonstruktionen fehlen derzeit geeignete Instrumente, um die Nachhaltigkeit ganzheitlich zu dimensionieren. Auf Basis bestehender Bewertungssysteme aus dem Hochbau wurde im Rahmen des Forschungsprojektes 'NaStafEE' eine Methode zur ganzheitlichen Nachhaltigkeitsbewertung stählerner Tragstrukturen für regenerative Technologien entwickelt. Mit Hilfe der entwickelten Methodik können unterschiedliche Bauweisen und Ausführungsvarianten unter Berücksichtigung von Anforderungen an eine nachhaltige Bauweise verglichen werden. Der Beitrag beschäftigt sich mit der Methodenentwicklung sowie der beispielhaften Anwendung auf stählerne Gründungsstrukturen von Offshore-Windenergieanlagen sowie Stahlfermenter von Biogasanlagen. Sustainability of steel constructions of renewables. 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. [ABSTRACT FROM AUTHOR]

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. Unlabelled Image • The novel saturation analysis procedure developed can assess the mechanical saturation behaviour of textiles • A suggestion for a suitable approach to the finally saturated state is provided • Exemplary application reveals that many thousands of load cycles are required for the tested fabric to suitably saturate • These findings are useful for design guidelines to sufficiently cover the saturated state in fabric structure projects [ABSTRACT FROM AUTHOR]

In this contribution new orthotropic hyperelastic energy functions are proposed for the geometrically nonlinear simulation of woven textile membranes. The new models are investigated and compared with a competitive formulation with respect to mathematical characteristics, accuracy in representation of experimental data and their robustness in numerical simulations. Part of the models is polyconvex and thus, a physically meaningful and mathematically sound formulation is obtained. The models are adjusted to stress‐strain paths of a glass‐PTFE fabric under cyclic uniaxial and biaxial tension tests. Moreover, a new large scale experimental setup is presented which enables the study of the material behavior in real structural problems. [ABSTRACT FROM AUTHOR]

Abstract: Coated fabric membranes have been widely used in construction of light‐weight structures. The material behavior of textile membranes is highly nonlinear and anisotropic which may not be sufficiently represented by commonly used linear elastic orthotropic models. This contribution presents a formulation of a suitable nonlinear anisotropic polyconvex energy function for textile membranes in the geometrically nonlinear framework. Representation of total in‐plane material behavior is the main goal of this paper, however, the induced thickness change is also considered in the continuum model. The material parameters of the energy function are adjusted by introducing and minimizing an objective function enforcing the model response to be as similar as possible to the experimental data. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]