November 20, 2013
|
RISA-3D,
New,
Torsion
When
solving
a
RISA-3D
model
you
may
find
you
have
a
Shear
UC
(unity
check)
much
higher
than
expected
from
bending
shear
alone.
If
you
open
the
detail
report
and
compare
the
shear
demand
to
the
shear
capacity
you
may
see
that
the
demand/capacity
is
less
than
the
Max
Shear
Check
reported.
What
is
likely
occurring
is
that
the
member
has
torsion
in
it.
In
RISA-3D
both
the
bending
and
shear
demands
are
affected
by
torsion,
though
it
is
shear
that
usually
causes
the
most
problems.
If
you
look
at
the
detail
report
and
in
the
Member
Torsion
spreadsheet
results
you
can
see
this
torsion.
Warping
Member
(Wide
Flange,
Channel,
etc):
Non-Warping
Member
(Tube,
Pipe,
etc):
Generally
speaking
wide
flanges
and
channels
work
very
poorly
in
torsion,
while
tube
sections
are
much
more
efficient.
Eliminating
torsion
or
using
a
more
efficient
section
are
common
ways
to
eliminate
this
problem.
Note
that
this
torsion
problem
can
happen
for
all
material
types…