Evaluation of Diaphragm Effect for Steel Welded Box Beam and Circular Column Connections

This paper investigates the design equations and the strength behavior of the diaphragm for steel box beams and circular column connections. The strength of the connection is decided by the strength of beam and column as well as connection diaphragm, because the connection diaphragm supports the concentration forces from the box beam's lower flange. In previous researches, however, the calculation procedure of the diaphragm stress from the indeterminate curved-girder model is too complicated to apply in regular practice. Irrational assumptions exist in deriving the process of the equation. Moreover, no reasonable design has yet been made because the diaphragm's effect on the strength of the connection has not been considered. Therefore, this study examines the strength behavior of a connection with diaphragm details through non-linear FEM analysis of the connection diaphragm. Finally, the connection strength is evaluated by using rigidity capacity of diaphragm, new diaphragm design method is proposed.