...
For
...
each
...
joint
...
of
...
a
...
structural
...
model,
...
displacement
...
may
...
either
...
be
...
unknown
...
and
...
solved
...
for,
...
or
...
it
...
may
...
be
...
known
...
and
...
input.
...
Known
...
...
displacement
...
is
...
either
...
zero
...
or
...
nonzero.
...
Zero
...
displacement
...
is
...
specified
...
for
...
fixed
...
DOF
...
at
...
restraint
...
support
...
locations.
...
Nonzero
...
joint
...
displacement
...
is
...
specified
...
for
...
such
...
a
...
condition
...
as
...
given
...
support
...
settlement,
...
or
...
application
...
of
...
displacement
...
time
...
history
...
to
...
specific
...
supports,
...
which
...
is
...
described
...
in
...
the
...
...
...
...
article.
...
When
...
joint
...
displacement
...
is
...
known
...
for
...
a
...
given
...
DOF
...
(whether
...
zero
...
or
...
nonzero),
...
a
...
...
must
...
be
...
assigned
...
along
...
that
...
DOF.
...
A
...
nonzero
...
displacement
...
value
...
may
...
then
...
be
...
assigned
...
using
...
the
...
Assign
...
>
...
Joint
...
Loads
...
>
...
Displacements
...
menu.
...
Numerical
...
solution
...
proceeds
...
by
...
solving
...
the
...
matrix
...
equation
...
K
...
u
...
=
...
F
...
,
...
where:
...
- K represents the stiffness matrix
- u represents joint displacements
- F represents joint forces
Software transfers nonzero joint displacements to the right side of this equation such that equivalent applied loads represent their effect. Unknown displacements on the left side are then solved.
See Also
- Ground motion at specific supports – Manual multi-support excitation