Stress Concentration Factors at Saddle and Crown Positions on the Central Brace of Two-Planar Welded CHS DKT-connections

作     者：Hamid Ahmadi Mohammad Ali Lotfollahi-Yaghin Mohammad H. Aminfar 

作者机构：Faculty of Civil EngineeringUniversity of TabrizTabriz 51664Iran 

出 版 物：《Journal of Marine Science and Application》 (船舶与海洋工程学报（英文版）)

年 卷 期：2012年第11卷第1期

页      面：83-97页

学科分类：08[工学] 080104[工学-工程力学] 080102[工学-固体力学] 0801[工学-力学（可授工学、理学学位）] 

主　　题：offshore jacket structure multi-planar tubular DKT-joint fatigue hot-spot stress method stressconcentration factor (SCF) 

摘      要：A set of parametric stress analyses was carried out for two-planar tubular DKT-joints under different axial loading conditions. The analysis results were used to present general remarks on the effects of the geometrical parameters on stress concentration factors （SCFs） at the inner saddle, outer saddle, and crown positions on the central brace. Based on results of finite element （FE） analysis and through nonlinear regression analysis, a new set of SCF parametric equations was established for fatigue design purposes. An assessment study of equations was conducted against the experimental data and original SCF database. The satisfaction of acceptance criteria proposed by the UK Department of Energy （UK DoE） was also checked. Results of parametric study showed that highly remarkable differences exist between the SCF values in a multi-planar DKT-joint and the corresponding SCFs in an equivalent uni-planar KT-joint having the same geometrical properties. It can be clearly concluded from this observation that using the equations proposed for uni-planar KT-connections to compute the SCFs in multi-planar DKT-joints will lead to either considerably under-predicting or over-predicting results. Hence, it is necessary to develop SCF formulae specially designed for multi-planar DKT-joints. Good results of equation assessment according to UK DoE acceptance criteria, high values of correlation coefficients, and the satisfactory agreement between the predictions of the proposed equations and the experimental data guarantee the accuracy of the equations. Therefore, the developed equations can be reliably used for fatigue design of offshore structures.