Local joint flexibility of tubular offshore joints with eccentric brace to chord connections

Abstract

Local joint flexibility of tubular offshore joints has been researched to be able to account for correct deflection and redistribution of member forces and moments. This has shown to improve design life prediction for offshore structures. The literature reviewed in this thesis do not account for brace eccentricity in their equations. A study of the effect of brace eccentricity on tubular joints was therefore done. This involves a parametric study of around 200 linear static analysis of tubular T-joints. These were used to implement the eccentricity variable into Buitrago’s out of plane bending equation. 28 nonlinear models were analysed in order to implement the eccentricity variable into MSL nonlinear ultimate capacity formula. After obtaining the results through finite element analysis. Regression and optimization were used to fit a function to the response generated by finite element analysis. Outcome from the linear static study resulted in a new equation with eccentricity that fitted the finite element analysis response with a R squared equal to 0.99. The nonlinear capacity equation with eccentricity achieved a R squared of 0.985. In both cases, there could be observed that the eccentricity factor did not have large influence on the local joint flexibility.