...
The
...
cyclic
...
plastic
...
moment
...
of
...
...
and
...
...
...
will
...
lead
...
to
...
ratcheting
...
behavior,
...
or
...
accumulation
...
of
...
plastic
...
deformation
...
in
...
the
...
axial
...
direction.
...
According
...
to
...
plasticity
...
theory
...
and
...
observed
...
structural
...
element behavior,
...
this
...
type
...
of
...
...
response
...
is
...
expected.
...
Ratcheting
...
is
...
a
...
real
...
effect
...
in
...
which
...
the
...
length
...
of
...
a
...
reinforced-concrete
...
member
...
tends
...
to
...
grow
...
in
...
each
...
direction
...
under
...
cyclic
...
bending.
...
On
...
the
...
tension
...
side,
...
steel
...
yields
...
and
...
concrete
...
cracks
...
such
...
that
...
load
...
transfers
...
only
...
through
...
steel
...
reinforcement.
...
On
...
the
...
compression
...
side,
...
both
...
steel
...
and
...
concrete
...
carry
...
load,
...
causing
...
less
...
compressive
...
deformation
...
than
...
tensile.
...
If
...
restraint
...
prevents
...
the
...
member
...
from
...
axial
...
elongation,
...
additional
...
compressive
...
forces
...
will
...
result.
...
Otherwise,
...
with
...
each
...
displacement
...
excursion,
...
axial
...
lengthening
...
(on
...
the
...
tension
...
side
...
of
...
the
...
neutral
...
axis)
...
will
...
exceed
...
axial
...
shortening
...
(on
...
the
...
compressive
...
side),
...
leading
...
to
...
the
...
accumulation
...
of
...
plastic
...
axial
...
strain.
...
Axial
...
ratcheting
...
occurs
...
because
...
plastic
...
yielding
...
keeps
...
some
...
tensile
...
deformation
...
from
...
being
...
recovered
...
upon
...
unloading.
...
...
...
capture
...
this
...
effect
...
directly
...
by
...
evaluating
...
the
...
localized
...
behavior
...
of
...
longitudinal
...
concrete
...
and
...
steel
...
fibers.
...
...
...
capture
...
ratcheting
...
through
...
formulation
...
associated
...
with
...
plasticity
...
theory
...
and
...
the
...
assumption
...
that
...
plastic
...
deformation
...
occurs
...
normal
...
to
...
the
...
yield
...
surface.
...
This
...
normal
...
includes
...
an
...
axial
...
component
...
except
...
at
...
the
...
balance
...
point,
...
where
...
pure
...
bending
...
occurs.
...
Ratcheting
...
can
...
be
...
observed
...
in
...
other
...
structural
...
configurations,
...
such
...
as
...
with
...
pile-foundation
...
sinking
...
under
...
cyclic
...
bending.
...
See Also
- Hinge response when yield point changes test problem, load cases 4a, 4b, and 4c
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