A Study on the Beam Permutation Technique for Frame Type Offshore Structures

J. Ocean Eng. Technol. 1999;13(1):23-28.

Piao Chun-Jun;Park, Han-Il;

프레임형 해양구조물의 보치환 기법에 관한 연구

박춘군;박한일;

한국해양대학교 대학원;한국해양대학교 조선.해양공학부;

Keywords: Frame Type Offshore Structure, Beam Permutation Technique, Reduction of Degree of Freedom

핵심용어: 프레임형 해양구조물, 보치환 기법, 자유도의 저감

Abstract

For offshore structures, dynamic analysis becomes increasingly important as water depth increases and structural configuration becomes more slender. In the case of dynamic analysis of frame structures, much computer time and high cost are required due to many degrees of freedom, In this paper, a new technique of permutating a segment of frame structure to a beam is developed, which is called here Beam Permutation Technique. The technique is based on definition of stiffness matrix of the beam which is obtained by defining the actions(or forces) required to obtain unit translation or rotation for each degree of freedom wiht al other degree of freedom restrained to zero displacement or rotation. In the technique, an assumption is made that relative positions of nodes in the ends of the segment are not variable, The technique can significantly reduce the degrees of freedom of frame structures and thus the computiong time in dynamic analysis. The natural frequencies and static displacements of the permutated beam are obtained and compared to those of ANSYS with a good agreement.