Should we relax seismic criteria for shorter system exposure times

Structures are conventionally designed for a level of earthquake-induced ground motion associated with a specified annual frequency of exceedance. Recently, a question has been raised as to whether the design basis seismic load can be reduced for systems with exposure durations much shorter than the normal economic life of a facility implying that a greater annual frequency of exceedance can be justified. Examples are temporary structures and structures with a short remaining life. With the intent of initiating a dialogue for establishing a well-founded basis for design of such systems, this paper identifies factors that might influence their design, introduces some fundamental safety principles that should be considered and reviews several related analyses that suggest bases for such reductions.