...
Joints
...
represent
...
points
...
of
...
connection
...
between
...
structural
...
members.
...
Joints
...
are
...
automatically
...
created
...
at
...
the
...
ends
...
of
...
line
...
objects
...
(
...
...
,
...
...
,
...
...
,
...
...
)
...
and
...
at
...
the
...
corners
...
of
...
...
and
...
...
objects.
...
Joints
...
may
...
also
...
be
...
added
...
manually
...
to
...
capture
...
localized
...
behavior,
...
or
...
to
...
simulate
...
...
supports.
...
...
conditions
...
are
...
also
...
applied
...
to
...
joints
...
to
...
establish
...
correlation
...
among
...
their
...
displacement
...
DOF.
Joints are fundamental to numerical solution in that stresses and strains are resolved according to joint displacement. First, an object-based model is created by drawing structural objects which are connected by joints and subjected to loading. Software then generates a finite-element model according to structural geometry and individual-member properties. Users have additional control over mesh refinement and intersecting-object connections. The FEM model then provides for analysis, and results are reported in terms of the object-based model.
Element mass and distributed loading are automatically transferred to joint locations during analysis. Users may assign additional mass to joints. During dynamic analysis, users should also assign mass moment of inertia (MMI) to joints such that inertial forces correlate with joint acceleration. MMI formulation is presented in the Analysis Reference Manual (page 41), and guidelines for dynamic-analysis acceleration are presented in the Time-history output-acceleration accuracy article.