Basis for seismic provisions of DOE-STD-1020

Abstract

DOE-STD-1020 provides for a graded approach for the seismic design and evaluation of DOE structures, systems, and components (SSC). Each SSC is assigned to a Performance Category (PC) with a performance description and an approximate annual probability of seismic-induced unacceptable performance, P{sub F}. The seismic annual probability performance goals for PC 1 through 4 for which specific seismic design and evaluation criteria are presented. DOE-STD-1020 also provides a seismic design and evaluation procedure applicable to achieve any seismic performance goal annual probability of unacceptable performance specified by the user. The desired seismic performance goal is achieved by defining the seismic hazard in terms of a site-specified design/evaluation response spectrum (called herein, the Design/Evaluation Basis Earthquake, DBE). Probabilistic seismic hazard estimates are used to establish the DBE. The resulting seismic hazard curves define the amplitude of the ground motion as a function of the annual probability of exceedance P{sub H} of the specified seismic hazard. Once the DBE is defined, the SSC is designed or evaluated for this DBE using adequately conservative deterministic acceptance criteria. To be adequately conservative, the acceptance criteria must introduce an additional reduction in the risk of unacceptable performance below the annual risk of exceeding the DBE. The ratio of the seismic hazard exceedance probability P{sub H} to the performance goal probability P{sub F} is defined herein as the risk reduction ratio. The required degree of conservatism in the deterministic acceptance criteria is a function of the specified risk reduction ratio.