Nonlinear Deformation of Satchel Connections

Document Type : Structural Earthquake Engineering


University of California, Berkeley


A type of connection, called Khorjeeni, has been widely used in Iran for low-rise steel frame buildings. The term describes the configuration with two beam profiles placed on the sides of the columns. Here we use the English equivalent and refer to this connection as satchel connection. The beam profiles are fastened to the columns by top and seat angles placed parallel to the beam. Depending on the relative stiffness of the angles, profiles, and the strength of the welds, the connection stiffness may range from very stiff to quite flexible. A large number of steel frames with satchel connections have been used in the earthquake zones, replacing masonry buildings destroyed by previous earthquakes. However, their effectiveness remains unclear under seismic forces. The stress in the connection is due to bending, shear, and torsion. Testraining in-plane forces are developed in the angles as they are typically welded to the flange of the beam profiles. These restrictions increase the bending capacity of the angle substantially, making the connection much stiffer. Excessive drift is often a major problem in flexible connections. Until recently building codes did not allow flexible connections in earthquake or high wind regions. The economic and practical advantages of flexible connections, however, have provided impetus for much research in recent years. Based on this research the Eurocode has already provided specifications for the use of flexible connections and the AISC Code is developing similar specifications. This paper discusses the nonlinear deformations of satchel connections. The purpose of the study is to develop a better understanding of the behavior of this type of connection under monotonic and cyclic loads, and to identify the areas requiring special attention during the design.