Alternate Seismic Mitigation Measures

DOE-STD-1020-2002

Performance Categories 2, 3, and 4

All aspects of the seismic design or evaluation must include independent peer review.

The seismic design or evaluation review should include design philosophy, structural

system, construction materials, design/evaluation criteria used, and other factors

pertinent to the seismic capacity of the facility. The review need not provide a detailed

check but rather an overview to help identify oversights, errors, conceptual deficiencies,

and other potential problems that might affect facility performance during an

earthquake. The peer review is to be performed by independent, qualified personnel.

The peer reviewer must not have been involved in the original design or evaluation. If

the peer reviewer is from the same company/organization as the designer/evaluator, he

must not be part of the same program where he would be influenced by cost and

schedule considerations. Individuals performing peer reviews must be degreed

civil/mechanical engineers with 5 or more years of experience in seismic evaluations.

Note that it can be very beneficial to have the peer reviewer participating early in the

project such that rework can be minimized.

C.9

Alternate Seismic Mitigation Measures

Seismic Base Isolation - An innovative technology for mitigating the effects of

earthquakes on structures is seismic base isolation. With this technology, a flexible isolation

system is placed between the structure and the ground to decouple the structure from the

potentially damaging motion of an earthquake. Ideally, an isolation system shifts the natural

period of an isolated structure above the predominant period range of an earthquake. In addition

to the period shift, isolation changes the dynamic response of the structure due to nonlinear

hysteretic behavior of the isolation system and the flexibility of the isolation system compared to

that of the structure. An isolation system essentially transforms the large accelerations from

earthquake motion in to large displacements of the isolation system. A main attribute of seismic

base isolation is that it substantially limits damage in a structure by significantly reducing the

forces and interstory drift that are generated during an earthquake. For a design-level

earthquake, the displacements in a structure are essentially limited to a rigid body displacement

with negligible interstory drift. Additionally, the seismic demand is limited to the base shear or

base acceleration transferred through the isolation system. By reducing forces and interstory

drift generated in a structure, seismic base isolation provides protection for the structure and its

contents so that a structure can remain operational during and immediately following an

earthquake. Seismic base isolation may be an earthquake resistant design option that provides

increase structural performance as compared with conventional seismic design. In contrast to

traditional design techniques of strengthening and anchoring, a base isolation system dissipates

seismic energy so that a new or existing SSC can be designed for lower seismic forces.

The UBC (Ref. C-2), beginning with the 1991 edition, contains regulations for the

design of seismic isolated structures. Efforts are currently underway to determine how these

regulations can be adopted within the DOE. Without specific guidance or criteria for the use of

seismic base isolation in the DOE, it is recommended that the regulations in the IBC 2000 be

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