...
An
...
equal
...
constraint
...
is
...
applied
...
to
...
...
such
...
that
...
equal
...
displacement
...
occurs
...
along
...
the
...
translational
...
DOF
...
specified.
...
No
...
coupling
...
occurs
...
between
...
translation
...
and
...
rotation,
...
differentiating
...
an
...
equal
...
constraint
...
from
...
a
...
...
...
.
...
Equal
...
constraints
...
are
...
useful
...
for
...
modeling
...
expansion
...
joints
...
and
...
locations
...
where
...
two
...
elements
...
connect
...
to
...
form
...
a
...
slot-pin
...
connection,
...
as
...
described
...
in
...
the
...
...
...
...
...
...
...
tutorial.
...
To
...
fully
...
connect
...
...
which
...
do
...
not
...
share
...
common
...
joint
...
locations,
...
body
...
constraints
...
should
...
be
...
used,
...
rather
...
than
...
equal
...
constraints.
...
Otherwise,
...
the
...
constraint
...
may
...
restrain
...
the
...
system
...
against
...
certain
...
types
...
of
...
behavior,
...
thus
...
stiffening
...
the
...
model,
...
and
...
generating
...
unrealistic
...
moment
...
values.
...
This
...
will
...
affect
...
analysis
...
and
...
may
...
lead
...
to
...
the
...
reporting
...
of
...
a
...
lack
...
of
...
equilibrium
...
among
...
constraint
...
forces
...
.
...