...
A
...
diaphragm
...
constraint
...
creates
...
...
between
...
...
located
...
within
...
a
...
plane
...
such
...
that
...
they
...
move
...
together
...
as
...
a
...
planar
...
diaphragm,
...
rigid
...
against
...
membrane
...
(in-plane)
...
deformation,
...
but
...
susceptible
...
to
...
plate
...
(out-of-plane)
...
deformation
...
and
...
associated
...
effects.
...
Diaphragm
...
constraints
...
relieve
...
numerical
...
accuracy
...
problems
...
which
...
result
...
when
...
floor
...
diaphragms
...
are
...
modeled
...
with
...
very
...
high
...
in-plane
...
stiffness.
...
They
...
also
...
enhance
...
the
...
computational
...
efficiency
...
of
...
dynamic
...
lateral
...
analysis
...
by
...
reducing
...
the
...
size
...
of
...
the
...
eigenvalue
...
formulation.
...
Plate
...
constraints
...
differ
...
from
...
diaphragm
...
constraints
...
in
...
that
...
plate
...
constraints
...
are
...
flexible
...
in-plane
...
and
...
rigid
...
against
...
out-of-plane
...
bending.
...
Plate
...
constraints
...
are
...
useful
...
for
...
connecting
...
...
and
...
...
to
...
...
objects,
...
and
...
may
...
be
...
implemented
...
in
...
detailed
...
beam
...
models
...
to
...
ensure
...
that
...
plane
...
sections
...
remain
...
plane.
...
Reported numerical problems for diaphragm constraints
Software creates a joint at the center-of-mass
...
of
...
a
...
diaphragm
...
constraint
...
to
...
enable
...
lateral-load
...
application.
...
Since
...
this
...
joint,
...
denoted
...
by
...
a
...
~
...
prefix,
...
is
...
constrained
...
against
...
in-plane
...
deformation,
...
the
...
out-of-plane
...
stiffness
...
components
...
are
...
set
...
to
...
zero.
...
Given
...
a
...
diaphragm
...
constraint
...
along
...
the
...
global
...
Z-axis,
...
these
...
components
...
correlate
...
with
...
the
...
UZ,
...
RX,
...
and
...
RY
...
DOF.
...
An
...
error
...
message
...
may
...
occur
...
which
...
informs
...
users
...
of
...
this
...
zero
...
stiffness
...
condition.
...
This
...
message
...
may
...
be
...
ignored
...
in
...
that
...
analysis
...
proceeds
...
accordingly,
...
and
...
results
...
are
...
not
...
affected
...
in
...
any
...
way.
...
Analysis
...
may
...
be
...
run
...
using
...
the
...
Advanced
...
Solver
...
to
...
avoid
...
the
...
reporting
...
of
...
this
...
message.