Investigation of seismic behavior of drilled flange connection with inclined arrangement of holes

Because unreinforced welded connections (WUFs) were brittle and prematurely fractured in the 1994 Northridge earthquake in the area of penetrating welds in the beam-to-column connection, the researchers proposed RBS connections to improve the seismic behavior of rigid connections. The brittle failure of weld in the beam-to-column connection and the lateral buckling of the beam flange in the reduced sections of the beam flange led to the proposed modified forms of this type of connection. The new type of connection includes drilled flange connection (DFC) with parallel rows of holes. In order to improve the performance of these DFCs, in this study, beam flange drilling arrangements were used with an inclined arrangement of holes with different hole diameters. The study showed that in the inclined arrangement of a hole, the amount of plastic rotation is 0.059 radians, which is 7.3% more than the plastic rotation of the same RBS connection. Also, in the connection sample DFC7 with the most suitable oblique drilling arrangement, the equivalent plastic strain index in the center and corner of the penetration welding line has decreased to 92.3% and 87.7%, respectively, compared to conventional RBS connections. Mises index in this connection in the center and corner of the penetration welding line has decreased to 45.5% and 39.9% compared to RBS connections, respectively, indicating better performance and less sensitivity of this type of connection to the problems of the penetration welding area of the beam-to-column connection compared with conventional RBS connections and DFC connections with the parallel arrangement.