December 21, 2021
|
RISAFloor ES,
Concrete,
Slab,
New,
Deflection,
Codes
Since
the
release
of
RISAFloor
v15
and
ADAPT-Builder
v20,
both
which
include
the
latest
update
to
the
ACI
code
(ACI
318-19),
some
customers
have
asked
our
support
team
why
they're
experiencing
increased
slab
deflections.
These
increased
deflections
are
the
result
of
changes
in
the
calculation
of
the
effective
moment
of
inertia,
Ie,
for
slabs
that
was
made
in
ACI
318-19
code,
compared
to
the
previous
ACI
318-14
code.
ACI
318-14
Code
In
the
ACI
318-14
Building
Code
Requirements
for
Structural
Concrete
code
(as
well
as
previous
versions
of
the
ACI
code)
the
calculation
for
the
effective
moment
of
inertia,
Ie
for
nonprestressed
members
was
as
follows:
The
use
of
the
effective
moment
of
inertia,
Ie,
was
developed
to
provide
a
transition
between
the
upper
and
lower
bounds
of
the
gross
moment
of
inertia,
Ig
and
the
cracked
moment
of
inertia,
Icr
as
a
function
of
the
ratio
of
Mcr/Ma.
Updates
to
the
ACI
318-19
Code
By
contrast,
the
ACI
318-19
code
incorporates
a
new
calculation
of
the
effective
moment
of
inertia,
Ie,
which
is
dependent
on
how
the
applied
moment
Ma
compares
to
a
ratio
of
2/3Mcr
(the
cracking
moment).
The
complete
calculation
is
as
shown
below:
These
new
equations…
