Recently, the demands of flush endplate connections have been increased in the field of bridge structures. However, no estimation-methods are proposed of the bolt axial force in such connections. This study proposes a new estimation method of the bolt axial force in flush endplate connections by FE analysis. Firstly, prying force coefficient and joint stiffness formulas are derived from the analysis of joint elements which can simulate the bolt force increment of flush endplate connections. Secondly, formulas for acting force in lower flange, horizontal stiffener and web are also obtained from girder analysis with a lower flange that has the low-Young's-modulus-region. Finally, the new estimation method for a bolt axial force is established by these proposed formulas.
