DUCTILE STEEL BEAM-TO-COLUMN CONNECTIONS FOR SEISMIC RESISTANCE

The strength and ductility of steel frames depend strongly on the beha vior of their beam-to-column connections, The fracture of beam-to-colu mn connections of steel buildings in the Northridge Earthquake generat ed concern about the reliability of current design and construction te chnology on steel connections. There is an urgent need to find a relia ble method to retrofit these connections and to use it for the design of new buildings. A simple method is proposed here to enhance the duct ility of beam-to-column connections. On trimming the beam flanges slig htly, the ductility of the connection can be improved greatly. Experim ental study of the newly designed connections under cyclic load shows that the ultimate strengths are almost unaltered, whereas the stiffnes s is decreased only slightly. However, the plastic rotational capacity can be increased several times. Moreover, the fracture proneness of c onnections due to welding sensitivity and stress concentration from ab rupt geometry alternation can be minimized and the energy dissipation capacity can be improved. A shaking table test of a steel frame design ed according to the proposed connection method also behaves better tha n that of a conventional moment-resisting frame.