This paper presents a method of determining in-plane LocaI Joint Flexibility (LJF) of innovative tubular connections using finite element modelling. LJF coefficients were determined by modelling the chord with braces removed and applying prescribed displacements and rotations to nodes along the brace-chord intersection line. Finite element models were used to form parametric equations for the LJF of a variety of standard and innovative joint configurations. The derived equations were validated, by laboratory testing and by modelling several connections using an independent finite element software package.
In recent years, the inclusion of Local Joint Flexibility (LJF) coefficients in a structural analysis has been shown to produce significantly different member actions to those calculated using a standard structural analysis. Including the effect of LJF in a structural jacket analysis for profile-cut joints has resulted in calculated joint bending moments of as low as one quarter of that calculated using standard structural analyses, while other structural actions are affected to a smaller but equally significant extent. Considerable research has been conducted at Monash University over the past 8 years developing novel steel tubular jointing systems which circumvent many of the problems and costs associated with conventional tubular joints. These connections incorporate grouted sleeves and flattened-end braces shown in Figure 1. Grout has been used with success for a number of years in offshore applications for effecting connections between jacket legs and piles and more recently in repairs to damaged tubular braces. These have not realised the full potential of grouted sleeve technology which extend well beyond the limited applications used to date. The findings so far are very positive. indicating superior strength under static and dynamic loading. superior fatigue performance as well as enormous benefits In fabrication and construction through minimising detailed welding and, low on-site technology required for erection particularly with its ability to readily accommodate large construction tolerances.
