...
What
...
is
...
the
...
"Col_Stiff"
...
category
...
and
...
why
...
does
...
it
...
appear
...
upon
...
import
...
from
...
ETABS?
...
Extended
...
Question:
...
When
...
we
...
import
...
a
...
section
...
of
...
our
...
ETABS
...
model
...
into
...
SAFE
...
using
...
the
...
Floor
...
Loads
...
and
...
Loads
...
Above
...
option,
...
the
...
"Col_Stiff"
...
category
...
automatically
...
appears
...
under
...
Slab
...
Properties.
...
The
...
effect
...
on
...
punching-shear
...
results
...
is
...
significant.
...
What
...
is
...
"Col_Stiff"
...
and
...
why
...
does
...
it
...
appear?
...
Answer:
...
In
...
real
...
structures,
...
there
...
is
...
an
...
extremely
...
stiff
...
region
...
within
...
the
...
connections
...
which
...
join
...
columns
...
and
...
walls
...
to
...
slabs.
...
The
...
"Col_Stiff"
...
elements
...
are
...
stiff
...
area
...
elements
...
in
...
which
...
the
...
software
...
amplifies
...
moment
...
of
...
inertia
...
by
...
100
...
times
...
to
...
capture
...
the
...
increased
...
stiffness
...
of
...
these
...
connections.
...
The
...
effects
...
associated
...
with
...
modeling
...
these
...
increased
...
stiffness
...
properties
...
within
...
connections
...
include
...
the
...
following:
...
- Deflections are more realistic and less conservative in magnitude.
- Rebar design is also less conservative since reinforcement is designed according to response at the face of the column, and not at the centerline of the support.
- Punching-shear results will change since the stiffness of the areas around the punching-shear perimeter change.