02 Fakultät Bau- und Umweltingenieurwissenschaften
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3
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Item Open Access Finite element based design of timber structures(2023) Töpler, Janusch; Schweigler, Michael; Lemaître, Romain; Palma, Pedro; Schenk, Martin; Grönquist, Philippe; Tapia Camú, Cristóbal; Hochreiner, Georg; Kuhlmann, UlrikeItem Open Access Lateral torsional buckling of glulam beam-columns : axial compression and bending verification(2024) Töpler, Janusch; Kuhlmann, Ulrike; Schänzlin, JörgItem Open Access Structural member stability verification in the new part 1‐1 of the second generation of Eurocode 3 : part 1: evolution of Eurocodes, background to partial factors, cross‐section classification and structural analysis(2020) Knobloch, Markus; Bureau, Alain; Kuhlmann, Ulrike; da Silva, Luís Simões; Snijder, Hubertus. H.; Taras, Andreas; Bours, Anna‐Lena; Jörg, FabianThis two‐part article gives an overview of the developments of the structural member verification in prEN 1993‐1‐1:2020 “Eurocode 3: Design of steel structures - part 1‐1: General rules and rules for buildings”, one of the second generation of Eurocodes. These developments were undertaken by Working Group 1 (WG1) of Subcommittee CEN/TC250/SC3 and by Project Team 1 (SC3.PT1) responsible for drafting the new version of EN 1993‐1‐1. In the past, WG1 collected many topics needing improvement, and the systematic review conducted every five years also yielded topics needing further development. Based on this, the current version of EN 1993‐1‐1 has been developed into a new draft version prEN 1993‐1‐1:2020 enhancing “ease of use”. The technical content of this new draft was laid down at the end of 2019. Many improvements to design rules have been established with respect to structural analysis, resistance of cross‐sections and stability of members. This two‐part article focuses on member stability design rules and deals with the basis for the calibration of partial factors, the introduction of more economic design rules for semi‐compact sections, methods for structural analysis in relation to the appropriate member stability design rules, new design rules for lateral torsional buckling plus other developments and innovations. This first part of the article primarily serves to explain the general background to the European Commission Mandate M/515 that led to the further evolution of the Eurocodes and to illustrate the developments in prEN1993‐1‐1:2020 that pertain to new material grades, partial factors, cross‐sectional classification and structural analysis. These form the necessary background to the changes to member buckling design rules, which are treated more specifically in the second part.Item Open Access A statistical assessment of the fatigue strength improvement of butt-welded joints by flush grinding(2023) Braun, Moritz; Baumgartner, Jörg; Hofmann, Gloria; Drebenstedt, Karl; Bauer, Niklas Michael; Bakhschi, Hadi; Kuhlmann, UlrikeAll major rules and guidelines include fatigue design (FAT) classes for flush ground butt-welded joints. These FAT classes vary between FAT110 and FAT155; however, in the majority of cases, the underlying database and specimen-related details are unclear or unknown. This study evaluates 1003 fatigue test results gathered from various literature sources and tries to relate the fatigue strength improvement to typical specimen types and test conditions. To this goal, statistical methods based on correlation analysis are employed. Next, proposals for updates of rules and guidelines for flush ground butt-welded joints made of steel are established by determining new FAT classes and a suitable slope exponent. In addition, an overview of design standards and recommendations is given and main influencing factors are discussed.Item Open Access Influence of the geometric properties, the timber-concrete interface, and the load protocol on the mechanical properties of timber-concrete composite connections(2024) Mönch, Simon; Campos, Joana A. A.; Dias, Alfredo M. P. G.; Kuhlmann, UlrikeTimber-concrete composite (TCC) structural systems are characterized by the combination of timber and concrete, which are connected to transmit shear forces between the two elements. In addition, to achieve an efficient connection, the slip between the two materials should be limited. Therefore, the load-carrying capacity, the stiffness, and the failure mode of TCC connections are important for the behavior of the composite element. This work aims to investigate the influence of test conditions on TCC connections using shear tests to determine the mechanical properties of connections. Therefore, it is essential to understand the influence of the configuration of the specimens (symmetric as push-out tests or asymmetric as inclined tests), the type of interface between the timber and concrete, and the test procedure (static or cyclic load protocol) on the resulting load-carrying capacity, stiffness, and failure modes. This paper reviews experimental tests conducted on TCC shear connection specimens, using various configurations to assess the influence of the test specimen configuration, material interface, and testing protocol on the determination of the mechanical properties.Item Open Access Structural member stability verification in the new part 1‐1 of the second generation of Eurocode 3 : part 2: member buckling design rules and further innovations(2020) Knobloch, Markus; Bureau, Alain; Kuhlmann, Ulrike; Simões da Silva, Luís; Snijder, Hubertus. H.; Taras, Andreas; Bours, Anna‐Lena; Jörg, FabianThis two‐part article gives an overview of the developments of the structural member verification in prEN 1993‐1‐1:2020 ”Eurocode 3: Design of steel structures - part 1‐1: General rules and rules for buildings“, one of the second generation of Eurocodes. These developments were undertaken by Working Group 1 (WG1) of Subcommittee CEN/TC250/SC3 and by Project Team 1 (SC3.PT1) responsible for drafting the new version of EN 1993‐1‐1. In the past, WG1 collected many topics needing improvement, and the systematic review conducted every five years also yielded topics needing further development. Based on this, the current version of EN 1993‐1‐1 has been developed into a new draft version prEN 1993‐1‐1:2020 enhancing ”ease of use“. The technical content of this new draft was laid down at the end of 2019. Many improvements to design rules have been established with respect to structural analysis, resistance of cross‐sections and stability of members. This two‐part article focuses on member stability design rules and deals with the basis for the calibration of partial factors, the introduction of more economic design rules for semi‐compact sections, methods for structural analysis in relation to the appropriate member stability design rules, new design rules for lateral torsional buckling plus other developments and innovations. This second part of the article is dedicated to illustrating the most relevant changes to member buckling design rules.Item Open Access Heat management and tensile strength of 3 mm mixed and matched connections of butt joints of S355J2+N, S460MC and S700MC(2023) Eichler, Stefan; Arnim, Mareike von; Brätz, Oliver; Hildebrand, Jörg; Gericke, Andreas; Bergmann, Jean Pierre; Kuhlmann, Ulrike; Henkel, Knuth‐MichaelHigh-strength structural steels are beneficial in terms of the sustainability of constructions due to the possible reduction of weight and overall material needs. Nevertheless, high-strength steels have a smaller processing parameter range in regarding the specific heat input and resulting cooling rate. Especially the cooling time t8/5 characterizing the time span to cool down from 800 to 500 °C is an important indicator. Single layer butt-welded gas metal arc welding (GMAW) connections of 3 mm plates between normal strength (S355J2+N, S460MC) and high-strength steels (S700MC) as well as matched connections (S460MC, S700MC) are carried out. Hereby, the influence of the energy input, melting rate, joint preparation, filler metal (matching and undermatching) and backing methods are observed. Spatially resolved IR-thermal observation shows variations within the welds of up to 50 % in the cooling time t8/5 depending on those parameters. These fluctuations lead to significant changes of the microstructure within the melting and heat-affected zone. UCI hardness mappings show the softening and microstructural change within these zones. Those soft zones can be the region of failure for butt welded connections as shown by transverse tensile tests with spatially resolved optical strain measurements. The results obtained can be used to define more precise welding procedures of these types of connections and also are used to develop design rules for mixed connections made of normal strength and high-strength steel.Item Open Access Load‐carrying capacity of MAG butt and fillet welded joints on high‐strength structural steels of grade S960QL and S960MC(2023) Brätz, Oliver; Arnim, Mareike von; Eichler, Stefan; Gericke, Andreas; Henkel, Knuth‐Michael; Hildebrand, Jörg; Bergmann, Jean Pierre; Kuhlmann, UlrikeThe use of high-strength structural steels brings great advantages in constructions regarding material requirements, weight reduction and productivity. Different steel grades within the S960 range are commercially available but not yet represented in Eurocode 3. The weldability of these steels is limited to smaller process windows to ensure the high material properties. In contrast to steels with moderate strength, there is a considerable risk of softening in the heat-affected zone causing a strength reduction of the connection. By now, the current EN 1993-1-12 only extends the design rules to cover steel grades up to S700. Therefore, the potential of these high-strength steels cannot be used to its full extent in structural engineering. This study, made within a steel application research project (FOSTA P 1507), deals with the weldability and load-carrying capacity of butt and fillet welded joints of S960QL and S960MC produced by gas-shielded metal arc welding. The influence of different bevel geometry, filler metal, and plate thicknesses was investigated. To extend the design rules up to S960, a need of an amendment was found for some combinations.Item Open Access The simplified method of the equivalent compression flange : development based on LTB tests and residual stress measurements(2019) Schaper, Lukas; Jörg, Fabian; Winkler, Rebekka; Kuhlmann, Ulrike; Knobloch, MarkusThe method of the equivalent compression flange simplifies the verification of lateral torsional buckling of steel beams to flexural buckling of an equivalent part of the cross‐section that is in compression. The current simplified method is based on outdated normative rules and the design results may be both, uneconomic and non‐conservative. To remedy these shortcomings, the simplified method is modified based on the basic structural behaviour of steel beams taking into account the effects of material, cross‐sectional geometry and residual stresses. This paper presents a comprehensive experimental study on the lateral torsional buckling behaviour and residual stresses of welded doubly‐ and mono‐symmetric I‐shaped steel beams. Moreover, an improved simplified method of the equivalent compression flange is proposed for design purposes.Item Open Access Fatigue of welded tubular K‐joints made up of circular hollow sections(2022) Kuhlmann, Ulrike; Dürr, André; Bove, Simon; Roth, Jakob; Knecht, WigandThis article deals with the fatigue behaviour of thick‐walled welded K‐joints made up of circular hollow sections (CHS). Two important aspects of the investigations were the extension of the application range to large CHS and the development of practice‐oriented recommendations for fabrication and quality assurance for weld shape and weld quality. For this purpose, fatigue tests were conducted on large CHS joints and on single K‐joints with specified weld irregularities. These studies were accompanied by systematic ultrasonic tests using the phased‐array technique, which were also used for the development of an inspection method for these complex weld geometries. Based on the results achieved by these experimental studies and additional numerical and statistical investigations, a proposal for a German design guideline (DASt‐Richtlinie 029) was finally elaborated to promote the practical implementation of trusses made up of CHS with thick‐walled chords and also to take a first step towards standardization.