Numerical Analysis of Local Joint Flexibility of K-joints with External Plates Under Axial Loads in Offshore Tubular Structures

Abstract

The Local Joint Flexibility (LJF) of steel K-joints reinforced with external plates under axial loads is investigated in this paper. For this aim, firstly, a finite element (FE) model was produced and verified with the results of several experimental tests. In the next step, a set of 150 FE models was generated to assess the effect of the brace angle (θ), the stiffener plate size (η and λ), and the joint geometry (γ, τ, ξ and β) on the LJF factor (f _LJF). The results showed that using the external plates can decrease 81% of the f _LJF. Moreover, the reinforcing effect of the reinforcing plate on the f _LJF is more remarkable in the joints with smaller β. Also, the effect of the γ on the f _LJF ratio can be ignored. Despite the important effect of the f _LJF on the behavior of tubular joints, there is not available any study or equation on the f _LJF in any reinforced K-joints under axial load. Consequently, using the present FE results, a design parametric equation is proposed. The equation can reasonably predict the f _LJF in the reinforced K-joints under axial load.

Keywords

Local joint flexibility / K-joints / Axial load / External stiffener plates / Parametric study / Design formula