Crack identification in an offshore structural frame through static substructuring and finite element method

Alam, Md. Rabiul (2001) Crack identification in an offshore structural frame through static substructuring and finite element method. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (19MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Identification of crack in an offshore structural frame using static substructuring and finite element approach was carried out by comparing local stresses, strains and global displacement results between uncracked and cracked structures. For simplicity of calculation and reduction of computational time and resources, a two-dimensional plane frame instead of the actual three-dimensional space frame structure was used in the numerical analysis; substructuring technique in finite element method was utilized as the numerical analysis methodology. In order to develop finite element meshes of this plane frame, eight noded degenerate isoparametric shell elements with reduced Gaussian integration points were used over the entire structure. ABAQUS finite element software was used to solve the problem and process all information relating to the above- mentioned global and local responses. Numerical results obtained in the analysis have been verified (for correctness) by using earlier published information and comparison with those obtained using other types of elements available in ABAQUS. -- From the analysis mentioned above, it was observed that the rate of change of normalized global displacements of a cracked structure becomes a maximum within the crack region; in addition, enormous changes in normalized local strains develop around the crack region. These parameters could be used to detect the crack and its position in real structures by the processing of information obtained from installed sensors (triaxial strain gauges, LVDTs and accelerometers) at various critical regions of the structure.

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