Static strength of collar plate reinforced tubular T/Y-joints under brace compressive loading

• The ultimate strength and failure modes of collar plate reinforced tubular T/Y-joints under axial load were studied.
• 168 FE models were developed for the parametric study of geometrical effects on the ultimate strength.
• Geometrical effects on the failure modes under axially compressive loads were studied.
• Significant difference exists between the static strength of unreinforced and collar plate reinforced joints.
• A parametric equation was proposed for the calculation of the strength ratio in reinforced T/Y-joints.

In the present paper, the static strength of steel collar plate reinforced tubular T/Y-joints is numerically investigated. A finite element (FE) model was developed and the results were verified against the experimental data. Afterwards, a set of 168 FE models of collar plate reinforced T/Y-joints was generated and analyzed under axially compressive loads. The effect of plate size and joint geometry on the ultimate strength and failure mechanism of the joints were investigated through a parametric study. Results showed that the ultimate strength of a collar plate reinforced T/Y-joint can be up to 270% of the strength of the corresponding unreinforced joint. Despite this significant difference between the static strength of unreinforced and collar plate reinforced T/Y-joints, studies on this type of reinforced joints have been limited to very few T-joint tests. Also, no design equation is available to determine the ultimate strength of T/Y-joints reinforced with collar plates. Hence, after the parametric study, a new equation is proposed, through nonlinear regression analysis, for determining the ultimate strength of collar plate reinforced T/Y-joints under axially compressive loads.