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Dynamic analyses include the effect of the structure's inertia.
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The frequency extraction procedure in
Abaqus/Standard
extracts the natural frequencies and mode shapes of the structure.
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The mode shapes can then be used to determine the dynamic response of
linear systems by modal superposition. This technique is efficient, but it
cannot be used for nonlinear problems.
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Linear dynamic procedures are available in
Abaqus/Standard to
calculate the transient response to transient loading, the steady-state
response to harmonic loading, the peak response to base motion, and the
response to random loading.
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You should extract enough modes to obtain an accurate representation of
the dynamic behavior of the structure. The total modal effective mass in the
direction in which motion will occur should be at least 90% of the mass that
can move to produce accurate results.
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You can define direct modal damping, Rayleigh damping, and composite
modal damping in
Abaqus/Standard.
However, since the natural frequencies and mode shapes are based on the
undamped structure, the structure being analyzed should be only lightly damped.
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Modal techniques are not suitable for nonlinear dynamic simulations.
Direct time integration methods or explicit analysis must be used in these
situations.
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Time variation of loads or prescribed boundary conditions can be defined
with an amplitude curve.
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Mode shapes and transient results can be animated in
the Visualization module
of
Abaqus/CAE.
This provides a useful way of understanding the response of dynamic and
nonlinear static analyses.