UFC 4-150-02
12 May 2003
Resist the maximum probable earthquake likely to occur one or more
times during the life of the structure (50 percent probability of exceedance
in 50 years) with minor damage, without loss of function, and the structural
system to remain essentially linear.
Resist the maximum theoretical earthquake with a low probability of being
exceeded during the life of the structure (10 percent probability of
exceedance in 100 years) without catastrophic failure and a repairable
level of damage.
2-4.3.2
Performance of POL and Hazardous Utilities. Design lifeline service
associated with construction categorized as containing "hazardous materials" with the
same levels of service. In general, hazardous material containment construction is
expected to:
Conform with criteria for essential construction.
Resist pollution and release of hazardous materials for an extreme event
(10 percent probability of exceedance in 250 years).
2-4.3.3
Liquefaction. Design of structures should include provisions to evaluate
and resist liquefaction of the foundation and account for expected potential settlements
and lateral spread deformation. Refer to MIL-HDBK-1007/3, Soil Dynamics and Special
Design Aspects. Special care must be given to buried pipelines in areas subject to
liquefaction to preclude breaks resulting in release of hazardous materials. It is
imperative to avoid areas of landslide and lateral spread. The presence of any
potentially liquefiable materials in foundation or backfill areas should be fully analyzed
and expected settlements computed.
2-4.3.4
Pipelines. Design pipelines to resist the expected earthquake induced
deformations and stresses. In general, permissible tensile strains are on the order of 1
to 2 percent for modern steel pipe. To accommodate differential motion between
pipelines and storage tanks, it is recommended that a length of pipeline greater than 15
pipe diameters extend radially from the tank before allowing bends and anchorage and
should be used on long pipelines. In general, pipes should not be fastened to
differentially moving components; rather, a pipe should move with the support structure
without additional stress. Unbraced systems are subject to unpredictable sway whose
amplitude is based on the system fundamental frequency, damping, and amplitude of
excitation. For piping internal to a structure, bracing should be used for system
components. Additional seismic protection considerations are as follows.
In potentially active seismic areas, no section of pipe should be held fixed
while an adjoining section is free to move, without provisions being made
to relieve strains resulting from differential movement unless the pipe is
shown to have sufficient stress capacity.
2-10
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