Optimisation of large complex structures in an early design stage considering accidental loads
Final Report Abstract
In this project, a large-scale ultra-low cycle fatigue (ULCF) test of a box girder is carried out. During the test, large plastic deformation, buckling, and fracture are observed. In the last half-cycle of the test, the large box girder is loaded with all these damages as initial imperfections. No prior experiment has applied this extent of cyclic load to a specimen with such dimension. During the ULCF of the large box girder, the occurred damage become significant imperfection for the following half-cycles, especially those sharing the load direction with the damage. Therefore, the structure is prone to collapse within a small number of cycles. The UHGS of a ship will reduce because of the damage from collision, making the ship structure prone to ULCF or collapse. The influence from collision to UHGS is relevant to the position of collision. Material definition is always the fundamental part of numerical simulation of ship structures. The pragmatic method introduced in this project is feasible and reliable. The consideration of computation efficiency and modelling accuracy brings a dilemma in the selection of mesh size. In this project, the h-AES method is introduced to reveal local details while keeping an overall coarse mesh. At the same time, the crack could be modelled without deleting elements. To represent the real components with adequate fidelity in numerical analysis, the 3Co principle is introduced in this project as a framework for the assessment of fidelity. Moreover, the fidelities of two bulb flat models are systematically assessed using the 3Co principle. This is believed to provide a sound basis for the use of bulb flat models in future applications regarding non-linear ship structural analysis. The pandemic influenced the project in many aspects. As a result, the project was severely influenced during the pandemic. The increase in steel price, which was significantly higher than the 2021 and 2022 plan, was also a surprise. This directly influenced the budget and schedule of the project.
Publications
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Pragmatic regularization of element-dependent effects in finite element simulations of ductile tensile failure initiation using fine meshes. Marine Structures, 74, 102823.
Wiegard, B. & Ehlers, S.
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Combining H-Adaptivity with the Element Splitting Method for Crack Simulation in Large Structures. Materials, 15(1), 240.
Song, Shi; Braun, Moritz; Wiegard, Bjarne; Herrnring, Hauke & Ehlers, Sören
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The ISSC 2022 committee III.1-Ultimate strength benchmark study on the ultimate limit state analysis of a stiffened plate structure subjected to uniaxial compressive loads. Marine Structures, 79, 103026.
Ringsberg, Jonas W.; Darie, Ionel; Nahshon, Ken; Shilling, Gillian; Vaz, Murilo Augusto; Benson, Simon; Brubak, Lars; Feng, Guoqing; Fujikubo, Masahiko; Gaiotti, Marco; Hu, Zhiqiang; Jang, Beom-Seon; Paik, Jeom-Kee; Slagstad, Martin; Tabri, Kristjan; Wang, Yikun; Wiegard, Bjarne & Yanagihara, Daisuke
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Committee V.2: Experimental Methods. 21st International Ship and Offshore Structures Congress, Volume 2. SNAME.
Ehlers, Soren; Abdussamie, Nagi; Branner, Kim; Fu, ShiXiao; Hoogeland, Martijn; Kolari, Kari; Lara, Paul; Michailides, Constantine; Murayama, Hideaki; Rizzo, Cesare; Seo, Jung Kwan & Kaeding, Patrick
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Application of the limit design state to hull-girder ultimate strength evaluations on the ship-shaped structures. Procedia Structural Integrity, 47, 812-819.
Faqih, Imaduddin; Prabowo, Aditya Rio; Adiputra, Ristiyanto; Muhayat, Nurul; Braun, Moritz & Ehlers, Sören
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Comparative study of shell element formulations as NLFE parameters to forecast structural crashworthiness. Curved and Layered Structures, 10(1).
Prabowo, Aditya Rio; Ridwan, Ridwan; Braun, Moritz; Song, Shi; Ehlers, Sören; Firdaus, Nurman & Adiputra, Ristiyanto
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Hull girder ultimate strength of bulk carrier (HGUS-BC) evaluation: Structural performances subjected to true inclination conditions of stiffened panel members. Results in Engineering, 18, 101076.
Faqih, Imaduddin; Adiputra, Ristiyanto; Prabowo, Aditya Rio; Muhayat, Nurul; Ehlers, Sören & Braun, Moritz
