General - STD-102020020146

DOE-STD-1020-2002

interaction, only the mass distribution of the equipment needs to be included in the

model of the structure. The equipment may be analyzed independently. With strong

coupling or if the equipment mass is 10 percent or more of the structure story mass,

the equipment including mass and stiffness properties should be modeled along with

the structure model.

Many equipment items are inherently rugged and can survive large ground motion if

they are adequately anchored.

Many equipment items are common to many industrial facilities throughout the world.

As a result, there is much experience data available on equipment from past

earthquakes and from qualification testing. Equipment which has performed well,

based on experience, does not require additional seismic analysis or testing if it could

be shown to be adequately anchored and representative of the experience data.

The presence of properly engineered anchorage is the most important single item

affecting seismic performance of equipment. There are numerous examples of

equipment sliding or overturning in earthquakes due to lack of anchorage or

inadequate anchorage. These deficiencies can also threaten adjacent safety related

items or personnel through spatial interaction.

Engineered anchorage is one of the most important factors affecting seismic

performance of systems or components and is required for all performance categories. It is

intended that anchorage have both adequate strength and sufficient stiffness to perform its

function. Types of anchorage include: (1) cast-in-place bolts or headed studs; (2) expansion or

epoxy grouted anchor bolts; and (3) welds to embedded steel plates or channels. The most

reliable anchorage will be achieved by properly installed cast-in-place bolts or headed studs,

undercut type expansion anchors, or welding. Other expansion anchors are less desirable than

cast-in-place, undercut, or welded anchorage for vibratory environments (i.e., support of rotating

machinery), for very heavy equipment, or for sustained tension supports. Epoxy grouted

anchorage is considered to be the least reliable of the anchorage alternatives in elevated

temperature or radiation environments.

Evaluation of facilities following past earthquakes has demonstrated that ductile structures

with systems and components which are properly anchored have performed very well. As a

result, properly engineered anchorage of systems and components is a very important part of the

seismic design criteria. Wherever possible, these criteria encourage the use of larger and deeper

embedment than minimum calculated anchorage as well as the use of cast-in-place and

undercut-type expansion anchors. It is recommended that minimum anchor bolt size be 1/2 inch

in diameter regardless of calculated anchorage requirements. Furthermore, it is recommended

that anchorage embedment be longer than needed, wherever practical.

For new design of systems and components, seismic qualification will generally be

performed by analysis or testing as discussed in the previous sections. However, for existing

systems and components, it is anticipated that many items will be judged adequate for seismic

C-46