Static strength of doubler plate reinforced tubular T/Y-joints under in-plane bending load

In the present paper, results of comprehensive finite element (FE) analyses performed on 210 generated models of T/Y-joints strengthened with doubler plate are presented. The results of FE models were validated against the data available from 12 experimental tests. These FE models investigate the effect of the doubler plate size and joint geometry on the static strength of doubler plate strengthened tubular T/Y subjected to in-plane bending (IPB) load. Afterwards, the ultimate capacity and deformed shapes of doubler plate and collar plate reinforced T- and Y-joints are compared. Results indicated that the doubler plate can significantly enhance the initial stiffness, ultimate capacity, and considerably improve failure patterns of T- and Y-joints under IPB load. In spite of the remarkable difference between the static capacity of un-strengthened and doubler plate strengthened T- and Y-joints subjected to IPB, the static strength of doubler plate strengthened T/Y-joints under IPB load has not been investigated so far and no design equation is available to calculate the ultimate strength of doubler plate reinforced T/Y-joints. For this reason, geometrically parametric study was followed by a set of nonlinear regression analyses to propose an ultimate capacity parametric formula for the static analyses of doubler plate strengthened tubular T/Y-joints subjected to IPB load.