Finite element analysis of the conventional and upgraded steel moment connections

Abstract

Many steel moment frames were damaged during the Northridge Earthquake and the Kobe Earthquake in Japan. The common damages came from fractures in the beam-to-column moment connection region. This incident clearly suggested that the current design procedures of the moment connection were not adequate. In this study, first , the nonlinear finite element analysis of a typical beam-to-column moment connection was performed to investigate the behavior of the weak panel zone and identify some potential problems of such a connection. Second, the upgraded model, which is a combination of the uses of continuity plates, the unrestrained beam flange length, and the supplemental plate, was modeled and analyzed. The stress triaxiality ratio at the beam flange interface area of both conventional and upgraded finite element models was compared. The results from the first part show that the state of stress around the connection area is, in fact, very complex. The stress contours show the high stress concentration between the interface and the access hole area. The current practice design is inadequate to meet the required strength of the connection. The study also shows that the weak panel zone can be used to absorb energy from the connection area in order to reduce the high ductility demand of the beam flange. Finally, the upgraded model also demonstrates the improved behavior of the connection.