ABSTRACT:

The recent research achievements on stress analysis of tubular joints in China are presented in this paper. Both theoretical analysis and experimental research on the elastic, elasto-plastic and rigid-plastic behaviour of tubular joints are investigated.

1. INTRODUCTION

There are two main kinds of limit states of tubular joints in offshore structures, such as fixed platforms and semisubmersible drilling vessels. One is the fatigue failure limit state related to the damaging effect of repeated loading and the other is the ultimate limit state, corresponding to the maximum carrying capacity. The occurence of high stress is the main cause of brittle fracture (high cycle fatigue). Sometimes, in the condition of bad huge storm, the plastic deformations occurred at the large part of the intersection curve of tubular joints is the main cause of low cycle fatigue failure (ductile fracture). The recent research actives on computing methods for elastic, elasto-plastic, rigid-plastic analysis of tubular joints and experimental works on steel models, photo-elastic models of tubular joints carried in China are presented in this paper.

2. ELASTIC ANALYSIS

The elastic analysis of tubular joints by analytic method was firstly carried out by Bijlaard(1) and Dundrova (2) thirty years ago. Owing to the difficulties in mathematical analysis only the stress distribution of chord tube could be found, and the analysis is limited to tubular T-joints, meanwhile the transfer loads between branch tube and chord tube are based on assumptions. Hence these analysis are somewhat empirical. The sem1-analytic method for the stress analysis of tubular Joints was investigated firstly by A.C. ScordeliS (3). He assumed that the vertical displacements of the chord tube around the intersection curve is uniform with magnitude same as the vertical displacement of top end of branch tube, i.e. the branch tube is considered as a rigid tube.

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