SSC Functionality Evaluation.
SSCs that are supported by target structures should be evaluated for
aircraft impact-related vibratory loads. Such an evaluation consists of
(1) generation of instructure vibratory motion at SSC support locations
resulting from impact force time-history; (2) structural evaluation of SSC
supports, including anchorage; and (3) evaluation of the SSC
functionality. Both support and SSC functionality evaluation can be
performed either by analysis or by testing.
For evaluation by analysis, the SSCs can be modeled, analyzed, and
evaluated in accordance with the applicable industry-accepted dynamic
analysis methods and acceptance criteria for safety-related SSCs, such
as those given in ASCE-4, ASME Boiler and Pressure Vessel Code,
IEEE-344, and NUREG-0800 (References 12, 13, 14, and 15),
recognizing that impact of some aircraft may generate vibratory loads with
more high frequency contents than those from typical seismic loads.
For evaluation by testing, the SSCs can be subjected to shake table
testing, using the instructure spectra generated from transient response
analysis as input spectra and following the methods described in
Evaluation of Earth-covered Structures.
Penetration of a rigid missile into earth media can be determined using
analytical or empirical formulas, which provide good agreement with test
data. Because most of the tests have been performed using ballistic
missiles, care should be exercised in applying the formulas to aircraft
If the earth cover exceeds 1.2 times the penetration depth calculated by
assuming a rigid missile, the missile should be assumed not to directly