Seismic design of steel column-tree moment-resisting frames, an state-of-the-art

In column-tree moment-resisting frames, short stubs of girders are welded to the column in the shop and then the middle portion of the girder spans are bolted to the column trees in the field. Thus, the system is a field bolted-shop welded structural system. The proposed seismic design procedures are expected to result in seismic behavior that can be categorized as Special Ductile Moment Resisting Frame behavior. The strength of shop-welded girder to column connection should match the strain hardened strength of the girder. The strength of field bolted splice, away from the column face, can be between 70% to 100% of the girder strength. The stiffness of the connections should be such that the ratio of rotational stiffness of the connection to EI/L of the girder is greater than 18. Column-tree connection details that result in ductile behavior are presented.