Pooya Rezadoost - Ph.D. Student of Civil Engineering, Faculty of Civil Engineering, K.N. Toosi University ofTechnology, Tehran, Iran.
Hossein Nassiraei - Assistant Prof., Department of Civil Engineering, Faculty of Engineering, University of Guilan,Guilan, Iran.

In the present paper, the Local Joint Flexibility (LJF) of the tubular X-joints reinforced with external plates under compressive load is investigated. In the first phase, a finite element (FE) model was generated and verified with the results of experimental tests and available equations. In the next phase, a set number of ۱۱۷ FE models were created to evaluate the role of the external plate size (βp and p), and the connection geometry (y, , and β) on the LJF factor (fLJF). In these FE models, the weld connecting the chord and brace members was generated. The results indicated that the growth of the plate size (βp and p), β and , and the decrease of the y led to the decrease of the fLJF. Despite the notable effect of the external plate on the fLJF, there is no study or formula on tubular connections reinforced with external plates. Therefore, the FE results were used to propose a parametric formula for determining the fLJF in X-joints with external plates under brace compressive load. Moreover, the derived formulas were checked based on the UK DoE acceptance criteria.

Geometrical Effects, Local Joint Flexibility, External Plates, Tubular X-Joints, Parametric Formula.