Dropped Object Analysis Using Non-Linear Dynamic FE Analysis

Ahn, Kwanghyun; Chun, Min-Sung; Han, Sang‐Min; Jang, Ki-Bok; Suh, Yong-Suk

doi:10.1115/omae2014-23333

Cited by 4 publications

(4 citation statements)

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“…A conversion must be made accordingly in the Abaqus platform. A complete solution for the RTCL stress state-dependent damage criterion in the plane stress condition is shown in equation (6); see details in Tornqvist. 25 e pl D (h, _ e pl ) = e crt f(h) The above formulation is only valid for the plane stress, where À 2=34h \ 2=3, which may cover most stress states in the simulation.…”

Section: Stress State Dependencymentioning

confidence: 99%

“…4 Sun et al 5 investigated the dropped object impact loads to a simplified platform deck; Ls-Dyna was used, and the failure strain was set as 0.5, which might be not conservative for deck structure design. Ahn et al 6 presented a nonlinear numerical FE analysis for dropped object impacts with an offshore platform deck by using Ls-Dyna. The dropped object was treated as a rigid object, and the rupture strain was simply set as 15%.…”

Section: Introductionmentioning

confidence: 99%

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Numerical simulation of dropped container impacts with an offshore platform deck in the North Sea

Liu¹

2021

Proceedings of the Institution of Mechanical Engineers, Part M:

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This paper presents a numeric study for an offshore platform deck that encounters potential dropped container impacts in the North Sea. The commercial Abaqus Explicit code was used. Significant plastic deformation was observed due to the high impact energy. A correct tensile fracture model that simulates the steel ductile failure under complicated stress states becomes crucial in such analysis. The material test data are normally very limited in design, which makes it difficult to calibrate the failure criterion. The critical failure strain provided by rules/codes (NORSOK and DNV GL) is not explicitly based on the stress states. This paper presents two simple approaches to extend the failure strain to a wider triaxiality range. Validation has been performed for the two failure criteria that depend on stress states (based on the RTCL and first principal plastic strain). The criterion based on the first principal plastic strain is shown to give the most conservative results. The RTCL-based interpretation shows good agreement under different mesh sizes. Several practical issues during the analysis are also addressed. Both criteria have been applied in the case study. Minor differences are observed from the obtained results of the dissipated energy and impact force. However, the local failure patterns are quite different, to which further attention shall be paid.

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Section: Stress State Dependencymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical simulation of dropped container impacts with an offshore platform deck in the North Sea

Liu¹

2021

Proceedings of the Institution of Mechanical Engineers, Part M:

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“…Ahn et al 22 examined the influence of drop object analysis condition by means of parametric work. The work was related to the conditions, methodology, and dropped object calculation using non-linear dynamic finite element simulation.…”

Section: Literature Reviewmentioning

confidence: 99%

The assessment of impact damage caused by dropped objects on floating offshore structures

Özgüç

2020

Proceedings of the Institution of Mechanical Engineers, Part M:

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Offshore facilities are exposed to the risk of accidental damages caused by fire, explosion, dropped objects, extreme environmental events and vessel collision poses a big threat to the safety and operation. During any lifting work, either from a supply vessel to the installation or from within the installation or plant itself, there is a potential danger when objects are being lifted for a dropped object accident to take place. This paper introduces extensive dropped object analyses applied in the design of Floating Production Storage Offloading (FPSO) offshore units, where non-linear finite element analyses are performed using an explicit LS-DYNA tool. In the structural evaluation, the hull parts such as infill deck, galley, and main lay-down located on poop deck, and cargo deck are taken into account. The dropped objects study is to find out what happens to the FPSO hull structure if the heavy items are dropped. The drop object impact analyses show that even though some structural members were permanently deformed by drop loads, however, there was no failure taken place in accordance with the plastic strain criteria as per NORSOK Code. It is discovered that the pillars supporting the main lay-down area have not been suffered from buckling failure through examined reaction forces. Further, the impact resistance of a deck depends on the plate thickness and the size and spacing of the supporting stringers.

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“…Ahn et al [1] investigated the effect of the conditions under which an object is dropped, using a parametric study. This study examined the methodology, conditions, and design aspects of dropped object calculations using a non-linear dynamics FEM analysis.…”

Section: Introductionmentioning

confidence: 99%

Structural Assessment of the Hull Response of an FPSO Unit to Dropped Objects: A Case Study

Özgüç

2019

Polish Maritime Research

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Offshore structures are exposed to the risk of damage caused by various types of extreme and accidental events, such as fire, explosion, collision, and dropped objects. These events cause structural damage in the impact area, including yielding of materials, local buckling, and in some cases local failure and penetration. The structural response of an FPSO hull subjected to events involving dropped objects is investigated in this study, and non-linear finite element analyses are carried out using an explicit dynamic code written LS-DYNA software. The scenarios involving dropped objects are based on the impact from the fall of a container and rigid mechanical equipment. Impact analyses of the dropped objects demonstrated that even though some structural members were permanently deformed by drop loads, no failure took place in accordance with the plastic strain criteria, as per NORSOK standards. The findings and insights derived from the present study may be informative in the safe design of floating offshore structures.

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Dropped Object Analysis Using Non-Linear Dynamic FE Analysis

Cited by 4 publications

References 0 publications

Numerical simulation of dropped container impacts with an offshore platform deck in the North Sea

Numerical simulation of dropped container impacts with an offshore platform deck in the North Sea

The assessment of impact damage caused by dropped objects on floating offshore structures

Structural Assessment of the Hull Response of an FPSO Unit to Dropped Objects: A Case Study

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