@inproceedings{LiPasternak, author = {Li, Zheng and Pasternak, Hartmut}, title = {Development of a stochastic material model at constant stress distribution in steel construction}, series = {16th International Scientific Conference VSU 2016, Sofia, 2016, vol. 1}, booktitle = {16th International Scientific Conference VSU 2016, Sofia, 2016, vol. 1}, publisher = {VSU}, address = {Sofia}, pages = {193 -- 198}, abstract = {This paper briefly presents the results of theoretical and experimental investigations on the size effect in metal. The Chain of Bundle Model, which is based on a stochastic material model by Weibull and log-normal distribution, will be developed and the possibility to approximately determine the parameter ξ of the model is given. The tests were performed on specimens from the same steel with different sizes. According to the experiments, the relationship between the sizes of the specimens and the strength can be analyzed through probability- and reliability theory. The theoretical and experimental results show that if the volume increases hundredfold, the strength will be reduced to 90\% ~ 95\%. Therefore, the size effect plays an unnegligible role in steel construction.}, language = {en} } @inproceedings{LiPasternak, author = {Li, Zheng and Pasternak, Hartmut}, title = {Reliability analysis of size effect on flexural members with stochastic finite element method}, series = {12th International Conference on Structural Safety \& Reliability, Vienna, Austria, 6-10 August 2017}, booktitle = {12th International Conference on Structural Safety \& Reliability, Vienna, Austria, 6-10 August 2017}, editor = {Bucher, Christian and Ellingwood, Bruce R. and Frangopol, Dan M.}, publisher = {TU-MV Media Verlag}, address = {Vienna}, isbn = {978-3-903024-28-1}, language = {en} } @misc{LiLaunertPasternak, author = {Li, Zheng and Launert, Benjamin and Pasternak, Hartmut}, title = {Application of the stochastic finite element method in welding simulation}, series = {Welding in the World}, volume = {62}, journal = {Welding in the World}, number = {5}, issn = {0043-2288}, doi = {10.1007/s40194-018-0596-4}, pages = {905 -- 912}, abstract = {Due to the uncertain microscopic structure of the material, the strength of the material exhibits strong randomness. This randomness results in uncertain response of the structure in the sequentially coupled thermal-mechanical analysis by welding simulation. Because of the limitations of deterministic welding simulation, the stochastic finite element method with random field will be introduced into the welding simulation, so that the welded structure can be more accurately calculated in the stability and reliability structural analysis. Particularly, it is necessary to propose reasonable distributions of residual stress from welding simulations based on statistical and reliability theories. This paper is intended to implement the stochastic finite element method in the welding simulation using a general-purpose simulation program and to demonstrate the potential of the proposed approach. Furthermore, the statistical distribution function of the welding simulation response is obtained by maximum entropy fitting method. Then, a numerical example is presented by the proposed method.}, language = {en} } @misc{WangLiEuler, author = {Wang, Jian and Li, Zheng and Euler, Mathias}, title = {Investigation on shear buckling of steel welded I-section beams with reinforced web openings}, series = {ce/papers}, volume = {6}, journal = {ce/papers}, number = {3-4}, doi = {10.1002/cepa.2361}, pages = {1754 -- 1760}, language = {en} } @inproceedings{LiPasternakPartov, author = {Li, Zheng and Pasternak, Hartmut and Partov, Doncho}, title = {Influence of statistical size effect in steel on structural safety}, series = {Proceedings of 16th International Conference on New Trends in Statics and Dynamics of Buildings}, booktitle = {Proceedings of 16th International Conference on New Trends in Statics and Dynamics of Buildings}, editor = {Jendželovsk{\´y}, Norbert and Grmanov{\´a}, Alžbeta}, publisher = {Slovak University of Technology}, address = {Bratislava}, isbn = {978-80-227-4845-2}, abstract = {This paper present the investigation of the statistical size effect in steel structure and the corresponding reliability. This study described the randomness of material properties through two different ways. These two proposed simulation methods, which are an extension and supplement to traditional simulation methods, can effectively simulate the statistical size effect for the tensile and flexural components in steel structures. The test results show that the variations of the yield and tensile strength increase with the decreasing specimen volume. Besides, the structural component strength is not only related to the specimen volume, but also the stress distribution. It is found by studying the influence of statistical size effect on structural reliability that the strength, which is obtained by small specimens through statistical analysis in the laboratory, is no more accurately applicable to large construction. The core idea is that the stochastic material proper-ties are directly embedded in mechanical calculations to develop a more accurate and economical design method for steel structure.}, language = {en} } @misc{WangLiPasternaketal., author = {Wang, Jian and Li, Zheng and Pasternak, Hartmut and Euler, Mathias}, title = {Querkrafttragf{\"a}higkeit von Wellstegtr{\"a}gern mit versteiften quadratischen Steg{\"o}ffnungen}, series = {Bauingenieur}, volume = {98}, journal = {Bauingenieur}, number = {11}, issn = {0005-6650}, doi = {10.37544/0005-6650-2023-11-31}, pages = {343 -- 353}, abstract = {Die Ergebnisse aus drei Traglastversuchen und einer umfangreichen numerischen Parameterstudie (FE-Berechnungen) zum Tragverhalten von Wellstegtr{\"a}gern mit quadratischen Steg{\"o}ffnungen werden vorgestellt. Es werden versteifte Steg{\"o}ffnungen mit einem umlaufenden Versteifungskranz betrachtet. In der Parameterstudie werden die Einfl{\"u}sse der Steg{\"o}ffnungsgeometrie, der Tr{\"a}gergeometrie und der Position der Steg{\"o}ffnung auf die Querkrafttragf{\"a}higkeit der Wellstegtr{\"a}ger untersucht.}, language = {de} } @misc{LiuDongZhangetal., author = {Liu, Wen-Cai and Dong, Jie and Zhang, Ping and Zheng, Xing-Wei and Ding, Wen-Jiang and Li, De-Hui and Korsunsky, Alexander M.}, title = {Smooth and notched fatigue performance of aging treated and shot peened ZK60 magnesium alloy}, series = {Journal of materials research}, volume = {25}, journal = {Journal of materials research}, number = {7}, issn = {2044-5326}, pages = {1375 -- 1387}, language = {en} } @misc{LiPasternak, author = {Li, Zheng and Pasternak, Hartmut}, title = {Statistischer Maßstabseffekt und seine Bedeutung f{\"u}r die Zuverl{\"a}ssigkeit im Stahlbau,Teil 1 - Modell und Versuch}, series = {Bautechnik}, volume = {97}, journal = {Bautechnik}, number = {11}, doi = {10.1002/bate.202000030}, pages = {766 -- 772}, language = {de} } @misc{LiLoebjinskiPasternak, author = {Li, Zheng and Loebjinski, Maria and Pasternak, Hartmut}, title = {Statistischer Maßstabseffekt und seine Bedeutung f{\"u}r die Zuverl{\"a}ssigkeit im Stahlbau, Teil 2- Zuverl{\"a}ssigkeitsanalyse}, series = {Bautechnik}, volume = {97}, journal = {Bautechnik}, number = {11}, doi = {10.1002/bate.202000031}, pages = {773 -- 779}, language = {de} } @misc{LiPasternakRobra, author = {Li, Zheng and Pasternak, Hartmut and Robra, J{\"o}rgen}, title = {Tragverhalten von Wellstegtr{\"a}gern mit kreisf{\"o}rmigem {\"O}ffnungskranz}, series = {Bauingenieur}, volume = {96}, journal = {Bauingenieur}, number = {4}, issn = {0005-6650}, doi = {10.37544/0005-6650-2021-04-50}, pages = {114 -- 120}, language = {de} } @misc{WangLiPasternaketal., author = {Wang, Jian and Li, Zheng and Pasternak, Hartmut and Euler, Mathias}, title = {Shear Buckling Behavior of Tapered Steel Plate Girders with Sinusoidally Corrugated Webs}, series = {ce/papers}, volume = {6}, journal = {ce/papers}, number = {3-4}, issn = {2509-7075}, doi = {10.1002/cepa.2534}, pages = {1787 -- 1792}, language = {en} } @misc{WangEulerPasternaketal., author = {Wang, Jian and Euler, Mathias and Pasternak, Hartmut and Li, Zheng and Krausche, Thomas and Launert, Benjamin}, title = {Bending capacity of single and double-sided welded I-section girders: Part 1: Experimental investigations}, series = {Current Perspectives and New Directions in Mechanics, Modelling and Design of Structural Systems : Proceedings of The Eighth International Conference on Structural Engineering, Mechanics and Computation, 5-7 September 2022, Cape Town, South Africa}, journal = {Current Perspectives and New Directions in Mechanics, Modelling and Design of Structural Systems : Proceedings of The Eighth International Conference on Structural Engineering, Mechanics and Computation, 5-7 September 2022, Cape Town, South Africa}, publisher = {CRC Press}, address = {Boca Raton}, isbn = {978-1-00-334845-0}, doi = {10.1201/9781003348443-159}, pages = {975 -- 980}, abstract = {The lateral-torsional buckling resistance of welded steel girders is affected by their residual stresses and geo-metric imperfections. Generally, both influences are mainly controlled by the manufacturing process, in partic-ular the welding of the girder. This paper presents experimental investigations on four laterally unbraced welded steel girders with thin-walled I-sections, whose flange-to-web junctions are welded from one or two sides to evaluate the fabrication influence. The investigations include lateral-torsional buckling tests under combined bending and torsion loading caused by three-point bending due to an eccentric vertical single force. The geometric imperfections of the welded test girders are determined by 3D laser scanning. The test results show that the influence of the geometric imperfections and the residual stresses on the lateral-torsional buck-ling resistance is limited for the tested girders.}, language = {en} } @misc{DongLiPasternaketal., author = {Dong, Jiwu and Li, Zheng and Pasternak, Hartmut and Ciupack, Yvonne}, title = {Reinforcement of Fatigue Damaged Steel Structures Using CFRP Lamellas - Part 3: Numerical Simulation}, series = {Bauingenieur}, volume = {96}, journal = {Bauingenieur}, number = {10}, issn = {0005-6650}, pages = {362 -- 368}, language = {en} } @misc{LiPasternak, author = {Li, Zheng and Pasternak, Hartmut}, title = {Experimental and numerical investigations of statistical size effect in S235JR steel structural elements}, series = {Construction and Building Materials}, volume = {206}, journal = {Construction and Building Materials}, issn = {0950-0618}, doi = {10.1016/j.conbuildmat.2019.02.106}, pages = {665 -- 673}, abstract = {This paper presents the analysis of the statistical size effect in steel structural elements using the stochastic finite element (FE) method. The three-dimensional random field theory is applied to simulate the uncertainty of a nonlinear material. The proposed approach, which combines the discrete random field describing the randomness of the material properties via Monte Carlo simulations, is used for computing the bearing capacity variability of the steel structures. In addition, the mapping interpolation method makes it possible to separate the random field mesh and FE model mesh. The three-dimensional random field for the material properties is established according to the yield strength with a lognormal distribution based on reasonable assumptions, and the corresponding random field parameters are studied. Finally, the results of experimental investigation and simulations are compared based on the tensile and bending tests, and they indicate that the statistical size effect cannot be overlooked in S235JR steel structural elements and that the use of stochastic FE in the analysis of the statistical size effect has tremendous potential.}, language = {en} } @misc{LiPasternakCiupack, author = {Li, Zheng and Pasternak, Hartmut and Ciupack, Yvonne}, title = {Artificial neural network prediction of bearing capacity of welded columns based on simplified welding simulations}, series = {Advances in engineering materials, structures and systems : innovations, mechanics and applications : proceedings of the 7th International Conference on Structural Engineering, Mechanics, and Computation (SEMC 2019), September 2-4, 2019, Cape Town, South Africa}, journal = {Advances in engineering materials, structures and systems : innovations, mechanics and applications : proceedings of the 7th International Conference on Structural Engineering, Mechanics, and Computation (SEMC 2019), September 2-4, 2019, Cape Town, South Africa}, editor = {Zingoni, Alphose}, publisher = {Taylor \& Francis Group}, address = {London}, isbn = {978-1-138-38696-9}, pages = {1219 -- 1223}, language = {en} } @misc{LaunertLiPasternak, author = {Launert, Benjamin and Li, Zheng and Pasternak, Hartmut}, title = {Development of a new method for the direct numerical consideration of welding effects in the component design of welded plate girders}, series = {Advances in engineering materials, structures and systems : innovations, mechanics and applications : proceedings of the 7th International Conference on Structural Engineering, Mechanics, and Computation (SEMC 2019), September 2-4, 2019, Cape Town, South Africa}, journal = {Advances in engineering materials, structures and systems : innovations, mechanics and applications : proceedings of the 7th International Conference on Structural Engineering, Mechanics, and Computation (SEMC 2019), September 2-4, 2019, Cape Town, South Africa}, editor = {Zingoni, Alphose}, publisher = {Taylor \& Francis Group}, address = {London}, isbn = {978-1-138-38696-9}, pages = {1143 -- 1147}, language = {en} } @misc{LiPasternak, author = {Li, Zheng and Pasternak, Hartmut}, title = {Statistical size effect of flexural members in steel structures}, series = {Journal of Constructional Steel Research}, volume = {144}, journal = {Journal of Constructional Steel Research}, issn = {0143-974X}, doi = {10.1016/j.jcsr.2018.01.025}, pages = {176 -- 185}, abstract = {This paper presents the results of theoretical and experimental investigations on the statistical size effect (SSE) of flexural members in steel. The chain of bundle model is developed, which is based on a stochastic material model by Weibull and lognormal distribution. Furthermore, this model is embedded into the finite element method (FEM) software for the analysis of a complicated structure with a stress gradient. In order to determine the stochastic material model parameters, uniaxial tensile tests were carried out based on specimens using the same steel with different sizes. By comparing the experimental and simulation results, the material parameters could be analyzed based on the relationship between the specimen sizes and strength. Moreover, the 3-point and 4-point bending tests were performed and simulated with the developed model. The experimental and simulation results demonstrate that the SSE also exists in the flexural member, and the equivalent yield stress is closely related to the stress distribution and volume of the structure component.}, language = {en} } @misc{LiXuGeissleretal., author = {Li, Zheng and Xu, Siying and Geißler, Karsten and Wang, Jian and Pasternak, Hartmut}, title = {Developed numerical Analysis of Residual Stress caused by Welding and Cutting in Steel Structures}, series = {ce/papers}, volume = {6}, journal = {ce/papers}, number = {3-4}, issn = {2509-7075}, doi = {10.1002/cepa.2601}, pages = {1507 -- 1512}, abstract = {The welding and flame-cutting process in the steel construction are commonly used, especially for the bridge structure. Some experiments about welding and cutting have been done separately by some researchers. The results from the experiments were also compared with the results from the numerical simulation under 3D or 2D models. The agreements between those results are as good as they predicted. Therefore, the numerical simulation is a better way to analyze the quality of the steel construction after welding and cutting without time-consuming and a large amount of cost. But there are only a few research about the numerical simulation and the some of them are aimed to verify the experiments. In this study, the calculation about the residual stresses after welding and thermo-cutting are considered from 3D-model into 2D-Model. The heat source model is simply regarded as curves of time and welding energy with the algorithm methods. And no matter the change of the parameters of the model and the heat source, the heat transfer and the residual stresses can be calculated with the 2D models as fast as possible. By the means of the finite element software Abaqus, the I-profiles are easy to receive the job results with the input parameters. The influence of the welding and cutting process are visual and direct.}, language = {en} } @misc{PasternakLiStapelfeldetal., author = {Pasternak, Hartmut and Li, Zheng and Stapelfeld, Christoph and J{\"a}ger-Ca{\~n}{\´a}s, Andreas and Launert, Benjamin}, title = {Considering realistic weld imperfections in load bearing capacity calculations of ring-stiffened shells using the analytical numerical hybrid model}, series = {Stability and Ductility of Steel Structures 2019 : Proceedings of the International Colloquia on Stability and Ductility of Steel Structures (SDSS 2019), September 11-13, 2019, Prague, Czech Republic}, journal = {Stability and Ductility of Steel Structures 2019 : Proceedings of the International Colloquia on Stability and Ductility of Steel Structures (SDSS 2019), September 11-13, 2019, Prague, Czech Republic}, edition = {1st Edition}, publisher = {CRC Press}, address = {London}, isbn = {978-0-429-32024-8}, doi = {10.1201/9780429320248}, pages = {882 -- 889}, language = {en} } @misc{JaegerCanasLiPasternak, author = {J{\"a}ger-Ca{\~n}{\´a}s, Andreas and Li, Zheng and Pasternak, Hartmut}, title = {Axial buckling behavior of welded ring-stiffened shells}, series = {Stability and Ductility of Steel Structures 2019 : Proceedings of the International Colloquia on Stability and Ductility of Steel Structures (SDSS 2019), September 11-13, 2019, Prague, Czech Republic}, journal = {Stability and Ductility of Steel Structures 2019 : Proceedings of the International Colloquia on Stability and Ductility of Steel Structures (SDSS 2019), September 11-13, 2019, Prague, Czech Republic}, edition = {1st Edition}, publisher = {CRC Press}, address = {London}, isbn = {978-0-429-32024-8}, doi = {10.1201/9780429320248}, pages = {556 -- 563}, language = {en} } @misc{WangLiRobraetal., author = {Wang, Jian and Li, Zheng and Robra, J{\"o}rgen and Pasternak, Hartmut and Euler, Mathias}, title = {Investigation on Shear Buckling of Corrugated Web Beams with Reinforced Web Openings}, series = {ce/papers}, volume = {5}, journal = {ce/papers}, number = {4}, issn = {2509-7075}, doi = {10.1002/cepa.1800}, pages = {628 -- 634}, abstract = {Corrugated web beams are welded I-sections with thin-walled sinusoidal corrugated webs and flanges made of wide flat steel that have been developed as an alternative to steel girders with flat webs. In comparison with hot-rolled or welded I-beams with flat webs, corrugated web beams are connected with considerable material savings and fully automated production. Assuming the same load-bearing capacity, corrugated web beams are lighter than those with a flat web, since the corrugated web beams can often be loaded up to their plastic resistance without reinforcement of the web. The research on the load-bearing behavior of corrugated web beams without web openings is relatively mature. However, the resistance of corrugated web beams with reinforced web openings, as they are often used in buildings for installations, has not well experimentally been investigated, yet. This paper deals with the shear resistance of corrugated web beams with reinforced square web openings. Three specimens of different geometry with two square web openings were tested. The experiments are compared with a Finite Element Analysis by Abaqus® and with an analytical model allowing simplified calculation. Both models can relatively accurately calculate the shear resistance. The experimental and numerical results show that the increase of the shear resistance of perforated corrugated web beams depends on the wall-thickness and the steel grade of the web opening reinforcement.}, language = {en} } @misc{LiZhangShietal., author = {Li, Zheng and Zhang, Qiulei and Shi, Fei and Wang, Jian and Pasternak, Hartmut}, title = {Geometric Properties of Steel Components with Stability and Fatigue Risks Using 3D-Laser-Scanning}, series = {Buildings}, volume = {14}, journal = {Buildings}, number = {1}, issn = {2075-5309}, doi = {10.3390/buildings14010168}, abstract = {Nowadays, 3D laser scanning technology is extensively employed in laboratory investigations of steel structural components, providing accurate geometric dimensions to reduce uncertainties caused by indeterminate geometry in experimental results. It is often used in conjunction with the Finite Element (FE) Method and analytical solutions, which are more accurate deterministic operators in the research on steel structures. However, establishing a common methodological framework for transferring or mapping 3D-scanned information into finite element models for complex steel structures with stability and fatigue risks remains an ongoing task. In light of this, this study has developed a 3D scanning platform capable of obtaining accurate geometric dimensions for various types of steel components. Different coordinate systems and point cloud mapping algorithms have been established for different types of components to construct actual finite element models with initial imperfections. The feasibility of the self-developed 3D scanning platform and finite element modelling has been validated through three experimental cases: weld details, steel girders, and cylindrical shells. The research findings demonstrate that the captured point cloud can be automatically processed and corrected using the developed algorithm. The scanned data can then be input into the numerical model using various mapping algorithms tailored to the specific geometric properties of the specimens. The differences between the experimental test results and the simulated results obtained from the 3D-scanned finite element models remain within a small range. The self-developed 3D scanning platform and finite element modelling technique effectively capture the actual dimensions of different steel components, enabling the prediction of their stability and fatigue risks through numerical simulations.}, language = {en} }