Evaluation of the capacity of steel special bolted moment frame connections subjected to simulated column removal

Abstract

The eight bolted stiffened extended endplate (8ES) and bolted flange plate (BFP) moment connection are two common rigid joints that are widely used in special steel moment frames (moment resisting frames with high ductility). In this study, to investigate these connections' behaviour and capacity, first, verification of finite element assumptions was carried out using the Abaqus software. Then, based on the verification models, by changing different parameters, 17 specimens were designed following the AISC Manual using two beams and three columns to determine the maximum capacity values in a column loss scenario. The finite element analysis represents that the 8ES connection's failure begins near the joint area and at the vicinity of the rib stiffener, and the BFP connections provided no warning of failure before brittle fracture of bolts at the large displacement due to catenary action mode. The plastic equivalent strain, Von-Mises stress, and middle column force–displacement curve were discussed. Finally, a formula is presented based on the numerical results to determine the displacement at the maximum capacity of these connections, a formula is presented based on the numerical results using the Least Square Method (LSM). Finally, the modification factors are presented for the theoretical formula to determine these connections' maximum capacity under column removal demands.