October 13, 2011
|
Loads,
RISAFloor,
New
One
of
the
most
overlooked
design
criteria
for
commercial
buildings
is
the
tendency
of
the
floor
system
to
bounce
or
vibrate
due
to
human
footfalls.
Excessive
vibration
of
the
floor
system
is
a
serviceability
issue,
and
can
lead
to
annoyance
or
concern
from
the
building’s
occupants.
Fortunately,
RISAFloor
has
the
ability
to
check
the
floor
system’s
performance
in
this
regard,
based
on
the
criteria
defined
in
AISC
Design
Guide
#11.
When
you
define
area
loads
in
RISAFloor,
one
of
the
definitions
is
for
Vibration
Load
(VL).
This
represents
the
actual
live
load
anticipated
to
be
present
on
the
floor.
While
typical
design
live
loads
can
be
upwards
of
80
psf,
the
true
live
load
(which
will
assist
in
dampening
the
floor
vibration)
in
a
commercial
building
is
typically
less
than
20
psf.
During
solution
the
program
determines
the
natural
frequency
of
the
floor
system,
considering
the
self
weight
of
the
beams
and
deck,
as
well
as
the
additional
Vibration
Load,
and
compares
that
against
a
dynamic
excitation
caused
by
a
person
walking.
The
result
is
an
expected
floor
system
acceleration
(%g),
which
can
be
compared
against
allowable
accelerations
for
different
building
types.
You
can
review
the
vibration
results
either
through…