ABSTRACT
Modern seismic design codes recognize that inelastic behaviour can reduce the earthquake forces generated in structures significantly and that this reduction is accompanied by an appreciable ductility demand. Currently, no generally accepted means exists of establishing the degree of force reduction suitable for use in design codes. A standardized means of establishing force reduction factors is therefore required. This paper describes a method for establishing force reduction factors for lateral load resisting systems based on large-scale physical tests. Lower and upper bounds to the force reduction factor are found from the hysteretic behaviour obtained through a cyclic test of the system to failure. Within these bounds, an appropriate value for code use is then selected based on properties that influence the behaviour of the structure in an actual earthquake, such as ductility, hysteretic energy dissipation, resistance to degradation, inherent redundancy, number of cycles resisted, and the failure mode.
