@misc{LaunertSzczerbaGajewskietal., author = {Launert, Benjamin and Szczerba, Radosław and Gajewski, Marcin and Rhode, Michael and Pasternak, Hartmut and Giżejowski, Marian}, title = {The buckling resistance of welded plate girders taking into account the influence of post-welding imperfections - Part 1: Parameter study}, series = {Materials Testing}, volume = {59}, journal = {Materials Testing}, number = {1}, issn = {0025-5300}, doi = {10.3139/120.110964}, pages = {47 -- 56}, abstract = {Welding is the most important joining technique and offers the advantage of customizable plate thicknesses. On the other hand, welding causes residual stresses and deformations influencing the load carrying capacity. Their consideration in the design requires simple and fast models. Though welding simulation has contributed to accurately access to these values nowadays, their application to large components remains still in a less practicable range. Nevertheless, many studies emphasized the need to make corrections in recently available simplified models. Especially the influence of residual stresses seems somewhat overestimated in many cases if comparing conventional structural steel S355 and high-strength steel S690. In times of computer-aided design, an improved procedure to implement weld-inducted imperfections appears overdue. This will be presented in two parts. The first part illustrates the potential influence of post-welding imperfections exemplified for weak axis buckling in comparison with the general method in accordance with Eurocode 3. Residual stresses and initial crookedness were varied systematically in order to produce a scatter band of capacities. An approach to characterize the borders of these imperfections was undertaken before that. The excessive scattering of reduction factors for the load bearing capacity demonstrates the importance of these variables. Results were finally evaluated against advanced simulation models which will be further detailed in part two of this contribution.}, language = {en} } @misc{PasternakLaunertKannengiesseretal., author = {Pasternak, Hartmut and Launert, Benjamin and Kannengießer, Thomas and Rhode, Michael}, title = {Advanced Residual Stress Assessment of Plate Girders Through Welding Simulation}, series = {Procedia Engineering}, volume = {172}, journal = {Procedia Engineering}, issn = {1877-7058}, doi = {10.1016/j.proeng.2017.02.013}, pages = {23 -- 30}, abstract = {This article provides an impression on potentials in applying nowadays welding simulation tools in construction design. This is carried out exemplary on plate girders from two structural steel grades. The calculated residual stresses are compared with measurements by sectioning method. It has been repeatedly stated that present Eurocode models fail to approximate the residual stresses. Especially for high strength steel (HSS) only limited information is available on realistic occurring residual stresses in typical I-girders. The investigations are aimed to give further guidance on these values. A few proposals on advanced models are discussed.}, language = {en} } @techreport{LaunertPasternakRhodeetal., author = {Launert, Benjamin and Pasternak, Hartmut and Rhode, Michael and Kromm, Arne and Kannengießer, Thomas}, title = {Erh{\"o}hung der Tragf{\"a}higkeit geschweißter I-Tr{\"a}ger aus hochfestem Baustahl durch verbesserte Ans{\"a}tze zur Ber{\"u}cksichtigung von Eigenspannungen}, pages = {4}, language = {de} } @misc{LaunertPasternak, author = {Launert, Benjamin and Pasternak, Hartmut}, title = {Weld residual stresses effects in the design of welded plate girders: Simulation and Implementation}, series = {Ce/papers}, volume = {1}, journal = {Ce/papers}, number = {2-3}, issn = {2509-7075}, doi = {10.1002/cepa.144}, pages = {1039 -- 1047}, abstract = {Eurocode 3 offers different possibilities on a numerically-aided design of welded plate girders. In this, a geometrically and materially nonlinear analysis of the imperfect structure (GMNIA) provides the theoretically highest possible degree of realism. A correct implementation of "imperfections" is of critical importance in the practical application of this method. The current design rules are based on long term experience in terms of traditional ("old") welding procedures and regular ("low strength") steel grades. Thus, they provide very approximate (but safe) rules for these structures. With the introduction of modern shop welding operations and materials, many of these assumptions seem to be over-conservative. A revision of these rules is being processed in different national and international research projects. This particular study focusses on the weld residual stresses and their effects in conventional steel S355 and high strength steel S690. Metal active gas (MAG) welding under shop welding conditions was used. The measurement of weld residual stresses on component-like samples (carried out by the BAM Bundesanstalt f{\"u}r Materialforschung und -pr{\"u}fung in Berlin) has been widely published. The hereupon based (simplified) welding simulation as part of a subsequent structural analysis is shown here. A novel numerical approach how to directly incorporate the results into large structural components models is presented. The capacity analysis is performed on a simple example for weak-axis buckling. The results indicate significant improvements in the utilization of load-bearing capacity and underline the superior buckling assignment for the S690 compared to conventional S355. The experimental validation of the findings is currently being prepared.}, language = {en} } @misc{KrauscheLaunertPasternak, author = {Krausche, Thomas and Launert, Benjamin and Pasternak, Hartmut}, title = {A study on the prediction of welding effects in steel box girders}, series = {Ce/papers}, volume = {1}, journal = {Ce/papers}, number = {2-3}, issn = {2509-7075}, doi = {10.1002/cepa.500}, pages = {4410 -- 4416}, abstract = {For standard sections including I-girders and rectangular box girders, several approaches on geometrical and structural imperfections are given in the literature, which can be implemented in a numerical analysis. For complex sections, as found in many of today's lightweight roof structures, these assumptions are conservative due to the sections typically unique shape, which leads to increased thicknesses or additional stiffening of the plates. This, on the other hand, can significantly affect fabrication costs. This paper aims to provide an overview on the possibilities in the numerical prediction of weld residual stresses and weld-induced deformations for these sections. The obtained values can be used in a subsequent numerical analysis to understand the structural behavior and optimize the design. A representative example on a section used in a steel compression ring is described and analyzed using the numerical welding simulation. A simplification of the originally transient weld procedure is used in order to reduce computation times to a practically reasonable level. In this context, the Abaqus Welding Interface (AWI) helps to automate working steps in conjunction with the definition of weld passes and their sequencing, which shall be shown in here. The applicability of this method is discussed showing also a need of further investigations in this field. This is especially with regard to result quality, which requires some experimental back-up. Nonetheless, this method could already help to show up tendencies or to identify potential critical spots in the design.}, language = {en} } @inproceedings{KrauscheLaunertPasternak, author = {Krausche, Thomas and Launert, Benjamin and Pasternak, Hartmut}, title = {Welding effects in unregularly steel box girders}, series = {6th Structural Engineers World Congress (SEWC 2017), Cancun/Mexico}, booktitle = {6th Structural Engineers World Congress (SEWC 2017), Cancun/Mexico}, publisher = {Universidad Nacional Aut{\´o}noma de M{\´e}xico - UNAM}, pages = {6}, abstract = {Several approaches on geometrical and structural imperfections are given in the literature for I sections and rectangular box girders. Those approximations of the residuals stress state can be implemented into the structural analysis using multi-purpose FEM program packages. The knowledge of the stress state of free forming cross sections has still to be determined. To fulfil a safe design, the assumptions mostly will be very conservative due to the lack of the assumed stress state. This will result directly to increased thicknesses or additional stiffening of the plates. Not only the material cost will rise, but also the fabrication costs like welding will be affected. This paper aims to provide an overview on the possibilities in the numerical prediction of weld residual stresses and weld induced deformations for cross sections with unique shapes. With the obtained values the tendencies of the residual stress state and deformations will be used to optimize the design. A representative example on a section used in a steel compression ring of a realized roof is described and analyzed using a simplification of a numerical welding simulation. The reduced simulation of the originally transient weld procedure was held to a practically reasonable level and can be reproduced for similar problems. The calculations used the Abaqus Welding Interface (AWI) to automate working steps in conjunction with the definition of weld passes and their sequencing. The field of the method that is discussed also a need of further investigations to prove its applicability. Some experimental back up is requires to verify the result quality. Nonetheless, this method could already help to show up tendencies or to identify potential critical spots in the design.}, language = {en} }