Static strength of X-joints reinforced with collar plates subjected to brace tensile loading

Present research investigates the initial stiffness, ultimate strength, and failure modes of the X-joints reinforced with collar plates under axially tensile load. At the first stage, a finite element (FE) model was developed and verified against the test results obtained from an experimental study. After that, 136 FE models were created and analyzed. Results showed that the ultimate strength of an X-joint reinforced with collar plates can be up to 325% of the strength of the corresponding un-reinforced joint. Furthermore, the increase of the collar plate length leads to the remarkable increase of the initial stiffness and ultimate tensile strength. Also, in the same applied load, the deformation in the reinforced joints is significantly smaller than the deformation in the corresponding un-reinforced joint. In spite of remarkable difference between the static strength of the un-reinforced and the collar plate reinforced X-joints under tensile load, no study is available on this topic. In addition, no design equation is available to determine the ultimate strength of the reinforced X-joints subjected to tensile load. Therefore, after the parametric investigation, a new theoretical formula is proposed for the static design of the X-joints with collar plates subjected to axially tensile load.