...
Could
...
you
...
tell
...
me
...
about
...
the
...
values
...
used
...
in
...
interactive
...
concrete
...
frame
...
design?
...
Extended
...
Question:
...
I
...
am
...
trying
...
to
...
compare
...
the
...
moment
...
required
...
by
...
ASCE
...
31-03
...
load
...
combinations
...
to
...
the
...
moment
...
capacity
...
of
...
reinforced-concrete
...
columns.
...
How
...
do
...
I
...
find
...
moment
...
capacity?
...
Answer:
...
Section
...
3.4.2.3
...
of
...
the
...
...
Concrete
...
Frame
...
Design
...
Manual
...
(ACI
...
318-08)
...
describes
...
capacity-ratio
...
formulation
...
in
...
detail.
...
Additional
...
notes
...
are
...
as
...
follows:
...
- Moment
...
- capacity
...
- may
...
- be
...
- back-calculated
...
- from
...
- capacity
...
- ratio
...
- and
...
- design
...
- moment.
...
- Ensure
...
- that
...
- the
...
- capacity
...
- ratio
...
- is
...
- less
...
- than
...
- 1.0.
...
- If
...
- the
...
- column
...
- is
...
- failing,
...
- increase
...
- reinforcement
...
- until
...
- this
...
- condition
...
- is
...
- met.
...
- As
...
- an
...
- alternative,
...
- you
...
- may
...
- use
...
- the
...
- maximum
...
- probable
...
- moment,
...
- but
...
- keep
...
- in
...
- mind
...
- that
...
- maximum
...
- probable
...
- capacity
...
- is
...
- calculated
...
- using
...
- phi=1.
...
- Design
...
- Mu2
...
- and
...
- Mu3
...
- are
...
- factored
...
- moments
...
- which
...
- result
...
- from
...
- the
...
- higher
...
- of
...
- governing
...
- load
...
- combinations
...
- or
...
- Mu
...
- min
...
- .
...
- Capacity
...
- moment
...
- (maximum
...
- probable
...
- moment)
...
- is
...
- for
...
- columns
...
- defined
...
- as
...
- special
...
- seismic
...
- .
...
- The
...
- shear
...
- in
...
- special
...
- seismic
...
- columns
...
- is
...
- checked
...
- according
...
- to
...
- maximum
...
- probable
...
- moments
...
- (Mpr+
...
- and
...
- Mpr-)
...
- under
...
- the
...
- influence
...
- of
...
- axial
...
- force
...
- Pu
...
- using
...
- phi=1,
...
- as
...
- required
...
- by
...
- code.
...
- Maximum
...
- probable
...
- moment
...
- is
...
- per
...
- shear
...
- detailing
...
- for
...
- special
...
...
- .
- To factor moment (per ACI 318 Section 9.3.2),
...
- phi
...
- varies
...
- from
...
- 0.7
...
- for
...
- compression
...
- control
...
- to
...
- 0.9
...
- for
...
- tension
...
- control.
...
- Minimum
...
- Mu
...
- is
...
- based
...
- on
...
- minimum
...
- eccentricity
...
- and
...
- is
...
- calculated
...
- according
...
- to
...
- ACI
...
- 318
...
- 10.10.6.5.
...
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