Anchorage and Supports

DOE-STD-1020-2002

nuclear power industry. The references for this work are the Senior Seismic Review and

Advisory Panel (SSRAP) report (Ref. 2-12) and the Generic Implementation Procedure (GIP) for

Seismic Verification of Nuclear Plant Equipment (Ref. 2-13). Note that there are numerous

restrictions ("caveats") on the use of this data as described in the SSRAP report and the GIP. It is

necessary to conduct either seismic analyses or shake table testing to demonstrate sufficient

seismic capacity for those items that cannot be verified by seismic experience data or for items

that are not obviously inherently rugged for seismic effects. Currently, use of experience data is

permitted for existing facilities and for the items specified in the three references, (Ref 2-5), (Ref.

2-12) and (Ref. 2-13).

Anchorage and Supports

Adequate strength of equipment anchorage requires consideration of tension, shear, and

shear-tension interaction load conditions. The strength of cast-in-place anchor bolts and

undercut type expansion anchors shall be based on IBC Chapter 19 provisions (Ref. 2-7) for PC-

1 and

PC-2 SSCs and on ACl 349 provisions (Ref. 2-14) for Performance Category 3 and higher SSCs.

For new design by AC1 349 provisions, it is required that the concrete pullout failure capacity be

greater than the steel cast-in-place bolt tensile strength to assure ductile behavior. For evaluation

of existing cast-in-place anchor bolt size and embedment depth, it is sufficient to demonstrate

that the concrete pullout failure capacity is greater than 1.5 times the seismic induced tensile

load. For existing facility evaluation, it may be possible to use relaxed tensile-shear interaction

relations provided detailed inspection and evaluation of the anchor bolt in accordance with

References 2-5 and 2-15 is performed.

The strength of expansion anchor bolts should generally be based on design allowable

strength values available from standard manufacturers' recommendations or sources such as site-

specific tests or References 2-5 and 2-15. Design-allowable strength values typically include a

factor of safety of about 4 on the mean ultimate capacity of the anchorage. It is permissible to

utilize strength values based on a lower factor of safety for evaluation of anchorage in existing

facilities, provided the detailed inspection and evaluation of anchors is performed in accordance

with References 2-5 and 2-15. A factor of safety of 3 is appropriate for this situation. When

anchorage is modified or new anchorage is designed, design-allowable strength values including

the factor of safety of 4 shall be used. For strength considerations of welded anchorage, AISC

allowable values (Ref. 2-10) multiplied by 1.7 shall be used. Where shear in the member

governs the connection strength, capacity shall be determined by multiplying the AISC

allowable shear stress by 1.4.

Stiffness of equipment anchorage shall also be considered. Flexibility of base anchorage

can be caused by the bending of anchorage components or equipment sheet metal. Excessive

eccentricities in the load path between the equipment item and the anchor is a major cause of

base anchorage flexibility. Equipment base flexibility can allow excessive equipment movement

and reduce its natural frequency, possibly increasing dynamic response. In addition,

flexibility can lead to high stresses in anchorage components and failure of the anchorage or

equipment sheet metal.

2-20