...
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 frames and shells to solid 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.