Elsevier

Thin-Walled Structures

Volume 45, Issue 1, January 2007, Pages 15-23
Thin-Walled Structures

A method for progressive structural crashworthiness analysis under collisions and grounding

https://doi.org/10.1016/j.tws.2007.01.012Get rights and content

Abstract

Collisions and grounding always give rise to structural crashworthiness issues involving crushing, yielding, and fracture. For accidental limit state design and safety assessment associated with collisions and grounding, the resulting progressive structural crashworthiness characteristics should be analyzed to evaluate the energy absorption capability of the structure in the corresponding accidental event in conjunction with the associated criteria. The accidental energy absorption capability of a structure under collisions or grounding can be predicted by integrating the area below the reaction forces versus penetration curve until or after the accidental limit state is reached. For risk assessment associated with such accidents, the results of structural crashworthiness analysis are also used as a basis of the consequence analysis. The aim of the present paper is to present an efficient and accurate method which is useful for the progressive structural crashworthiness analysis of ships and ship-shaped offshore structures under collisions or grounding. Theoretical outline of the method is addressed. Application examples of the method to ship-shaped test structures are presented by a comparison with experimental results.

Introduction

Accidental limit states (ALS) potentially lead to a threat of serious injury or loss of life, pollution, damage and loss of property or significant financial expenditure. The intention of ALS design is to ensure that the structure is able to tolerate specified accidental events and, when accidents occur, it subsequently remains structural integrity for a sufficient period under specified (usually reduced) environmental conditions to enable evacuation of personnel from the structure, control of undesirable movement or motion of the structure, temporary repairs, safe refuge and firefighting in the case of fire and explosion, and minimizing outflow of cargo or other hazardous material to take risk mitigation and recovery measures to take place as relevant [1], [2].

Limit state design and safety assessment associated with collisions and grounding is typically based on the energy absorption capability of the structure until the accidental limit state is reached. Since the energy absorption capability can be obtained by integrating the area below the reaction forces versus penetration curve of the structure, the progressive structural crashworthiness analysis involving crushing, yielding, and fracture must be carried out to obtain the resulting force-penetration curve of the structure in the accidental event.

Further, the risk assessment associated with ALS needs to identify the consequence of accidental events, because the reaction forces versus penetration relationships of a structure under collisions and grounding are used as a basis of the consequence analysis.

While the finite element method is a powerful tool for the simulations of structural crashworthiness due to collisions and grounding [2], [3], [4], [5], [6], it may require a lot of modeling and computational efforts.

The aim of the present paper is to introduce an efficient and accurate numerical method for structural crashworthiness analysis of ships and ship-shaped offshore structures under collisions or grounding (stranding), which involves crushing, yielding, and fracture. The analysis method presented has been implemented into ALPS/SCOL [7] program, being linked with MAESTRO [8] for pre- and post-processing of the related computations.

Application examples of the method are presented by a comparison with experimental results on ship-shaped test structures under crushing loads or collisions or stranding actions.

Section snippets

Theory for structural crashworthiness analysis

ALPS/SCOL [7] is a computer program for the progressive structural crashworthiness analysis under collisions and grounding. It applies the idealized structural unit method (ISUM) [1], [2]. The following three types of ISUM elements are employed for ALPS/SCOL analysis, namely.

  • Rectangular plate element;

  • Beam-column element;

  • Gap/contact element.

It is noted that the theoretical formulation for the old version of the three types of ISUM elements above is presented in Paik and Pedersen [9], and Paik

Structural crashworthiness analysis for square tubes under crushing loads

Paik et al. [11] conducted a series of crushing tests on ship-shaped structure models such as unstiffened plate structures, longitudinally stiffened plate structures, transversely stiffened plate structures, and orthogonally stiffened plate structures, under crushing loads, until and after crushing takes place. Crushing loads were applied uniformly to the cross section of each tube.

Fig. 4 shows the four types of square tubes used for the tests. The aim of their tests was to investigate the

Structural crashworthiness analysis for a double-skin plated structure under collisions or stranding

Paik et al. [15] carried out an experimental study on a double-skin-plated structure quasi-statically penetrated by a circular cone type indentor, with varying the plate thickness and the collision location. Fig. 9 shows a schematic view of the test structure and the photograph of the actual test setup. The test structure is composed of plate elements only. The test results can also be applied to the study of stranding which is a specific type of grounding.

The details of the test are presented

Concluding remarks

For accidental limit state design and strength assessment of thin-walled structures under collisions and grounding, the progressive crashworthiness analysis involving crushing, yielding, and fracture must be carried out. This kind of the analysis is also required for the risk assessment associated with such accidental events, because the consequence analysis during the risk assessment is typically based on the results of the progressive crashworthiness analysis.

In the present paper, an

Acknowledgments

The present study was undertaken at the Ship and Offshore Structural Mechanics Laboratory (http://alps.ac), Pusan National University, Korea, which is a National Research Laboratory funded by the Korea Ministry of Science and Technology (No. M10600000239–06J00000–23910). The authors are pleased to acknowledge the support of Pusan National University. The present paper was presented at International Conference on Advancements in Marine Structures, 12–14 March 2007, Glasgow, UK.

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