A novel clevis-based beam-column model to investigate the hysteretic characteristics of steel moment connections: Experimental and numerical simulations. (February 2023) - Rastegaran, Mostafa
Highlights: Mechanical clevis-based connections equipped with steel tendons were tested under two different cyclic loading protocols representing far- and near-fault ground motions. Two deteriorations phenomena of steel moment-resisting frame connections, deformation softening and fracture (ductile and brittle types) have been simulated by this connection through various configurations and arrangements of steel tendons. Some connection behavioral indicators have a lot of dispersion that should be seriously considered when analyzing structures whose connections are susceptible to the mentioned failures. Connection hysteretic parameters are dependent on loading protocol features. Abstract: Following the 1994 Northridge and 1995 Hyogo-ken Nambu earthquakes, the potential for possible deterioration and failures in the connections of steel structures due to strong ground motions has been studied and explored. The most typical connection deteriorations have been fractures and deformation softening, as reported in earlier studies. The present study investigates the connection behavior uncertainties in fracture and deformation softening conditions. The connection behavior uncertainties were analyzed by applying a clevis-based mechanical connection under two loading protocols exhibiting far- and near-field earthquakes. In this connection, steel coupons on both sides of a middle pin were used to transfer the bending moment. Two notch patterns were formed on the steel coupons to create fracture conditions. Deformation softening cases were developed by reducing coupons' cross-sections in various configurations. To compare the uncertainties, seven indicators were considered: (1) capping rotation, (2) fracture rotation, (3) yield bending strength, (4) capping bending strength, (5) residual bending strength, (6) negative post-yield stiffness, and (7) Park and Ang's damage index. The results of various tests, subsequent numerical studies, and nonlinear regression analyses show that some connection behavioral indicators have many uncertainties that should be seriously considered when analyzing structures with these types of connections. In addition to having varying dispersion, different indicators are also dependent on loading protocol characteristics.