Numerical and experimental study on the behavior of drilled flange steel beam to CFT column connections

Numerous studies conducted on different types of rigid connections such as reduced beam section (RBS) and drilled flange (DF) showed their ductile behavior. This paper evaluates the seismic performance of moment resisting connections with drilled flange (DF) beams as a simple and efficient alternative for RBS connected to concrete-filled steel tube CFT columns. Different patterns are proposed and the shear capacity of panel zone and ductility of connection are assessed to obtain the optimum case. For this purpose, the finite element Abaqus version 6.14 is used for the numerical models with the thickness ratio of beam flange to web, the type of hole and the number of holes in beam flange as the main parameters. The best arrangement of zigzag hole pattern is first determined by cyclic loading and then experimentally validated. Based on the obtained results, the type and number of holes significantly affect the ductility of connection and decrease stress concentration in the area of beam to column connection. In addition, the idea results in changing plastic hinge from the area of beam-to column connection and panel zone to the beam in its drilled flange region and reducing the possibility of brittle failure at connection. Further, the arrangement can decrease flexural stress in the groove weld of direct beam-toCFT column connection by 41% and increase the flexural capacity of panel zone by 31%. Furthermore, a 35% enhancement was observed in the shear capacity of panel zone by increasing the flange to web thickness ratio.