...
A diaphragm constraint creates links between joints 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
CSI 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.