SEISMIC RESPONSE OF A NINE-STORY STEEL FRAME WITH FRICTION DAMPED CROSS-BRACING

lan D. Aiken', James M. Kelly2 , and Avtar S. Pall3

1 Graduate Student, Dept. of Civil Engineering, University of

California, Berkeley, USA

2 Professor, Dept. of Civil Engineering, University of California,

Berkeley, USA

3 President, Pall Dynamics Limited, Montreal, Quebec, Canada

SUMMARY

A passive energy dissipation system that incorporates friction damping devices in the cross-bracing of a medium-rise steel moment resisting frame is investigated. Earthquake simulator tests and an analytical study of the system are performed and the response characteristics compared with those of equivalent moment resisting and eccentric braced frames. An existing scale model 9 story steel moment resisting frame (MRF) was modified to include friction damped bracing as part of the lateral load resisting system. The frame is one bay wide and three bays long and represents a typical section in the weak direction of a steel frame building of approximately one quarter scale. It was observed that the friction damped braced frame (FDBF) system had the ability to behave in a nonlinear fashion without demanding inelastic behavior in the frame itself. This implied continued integrity of the structure during and after a seismic event. Analytical results and experimental observations confirmed that for small variations of the slip loads from the optimum loads the overall response of the frame remained essentially unchanged.