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 Equations (10e) and (11) are valid for T >/= tE
(d) In most cases, for [theta] >/= 5deg., the error is small if
one neglects the effects of tE by assuming tE = 0.
(e) The method is especially useful for predicting maximum
deflection and time to maximum when the response enters into the fully
plastic range of the resistance diagram.
(f) The diagram in Figure 4 assumes a constant effective mass.
In practical cases, this assumption is incorrect and both the load ad
resistance should be adjusted for the appropriate mass; i.e., at t > tE,
use p/mu and ru/mu and for t > t1, use p/mup and rup/mup.
(g) An example problem ad solution is presented at the end of
this section to illustrate the moment-area method.
(3) Response Charts. The previously described methods of accurately
determining the dynamic response of a single degree-of-freedom system can be
very time-consuming. For certain simplified load and resistance functions,
it is much quicker to predict maximum response from certain response charts.
TN 5-858-3, Designing Facilities to Resist Nuclear Weapon Effects -
Structures, contains several such charts which are extremely useful for
design purposes. For a given load function, only the natural period of
the system has to be known in order to determine the maximum DLF (Dynamic
Load Factor) from the charts and, hence, the ratio of maximum
dynamic-to-static stress. The maximum response of a pressure or
pressure-time sensitive system with an elasto-plastic resistance function
subjected to a triangular loading pulse is shown in Figure 6-7 of NAVFAC
P-397.
8. PROTECTION CATEGORIES. The design and siting of protective structures
shall conform to the criteria established in NAVFAC P-397, AMCR 385-100,
DOD 6055.9-STD and 4145.26. For the purpose of analysis, the protection
afforded by a facility can be subdivided into four categories:
a. Category 1. Protect personnel from fragments, falling portions of
the structure ad equipment. Protection should be provided for all
personnel, including personnel performing the activities, personnel in
other occupied areas and all transient personnel. Such protection can be
achieved by controlling debris through suppression, containment, etc., or
by establishing an exclusion area with positive access control.
b. Category 2. Protect equipment and supplies from fragment impact,
blast pressures, structural motions and against the uncontrolled release of
hazardous materials, including toxic chemicals, active radiological, or
biological materials, etc. To control the release of toxic or radioactive
materials, the enclosing structure and its associated ventilation,
electrical, fire protection, and utility systems shall be designed so that
personnel at a specified distance from the structure should not be exposed
to more than a specified level of the toxic or radioactive material.
c. Category 3. Prevent communication of detonation by fragments and
high-blast pressures.
2.08-10
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