...
What
...
are
...
E
...
c (S),
...
E
...
c (D),
...
and
...
E
...
c (V)
...
in
...
composite
...
beam
...
design?
...
Answer:
...
Values
...
for
...
E
...
c (S),
...
E
...
c (D),
...
and
...
E
...
c (V)
...
are
...
given
...
as
...
follows:
...
- Ec (S)
...
- is
...
- the
...
- modulus
...
- of
...
- elasticity
...
- for
...
- strength
...
- design.
...
- For LRFD,
...
- E
...
- c (S)
...
- is
...
- taken
...
- directly
...
- as
...
- the
...
- modulus
...
- of
...
- elasticity
...
- of
...
- the
...
- material
...
- assigned
...
- to
...
- the
...
- composite
...
- section.
...
- For ASD,
...
- E
...
- c (S)
...
- is
...
- calculated
...
- as
...
- 33
...
- *
...
- gamma
...
- c
...
- 1.
...
- 5 *
...
- √f
...
- '
...
- c (ksi),
...
- where
...
- gamma
...
- c
...
- is
...
- the
...
- weight
...
- per
...
- unit
...
- volume
...
- (kips/in
...
- 3
...
- )
...
- of
...
- the
...
- material
...
- assigned
...
- to
...
- the
...
- composite
...
- section.
...
- Ec (D)
...
- is
...
- the
...
- deflection
...
- modulus
...
- of
...
- elasticity,
...
- given
...
- as
...
- E
...
- c (S)
...
- /
...
- (creep
...
- factor),
...
- where
...
- the
...
- creep
...
- factor
...
- is
...
- specified
...
- in
...
- the
...
- Preference
...
- menu.
...
- Ec (V)
...
- is
...
- the
...
- vibration
...
- modulus
...
- of
...
- elasticity,
...
- given
...
- as
...
- 1.35
...
- *
...
- E
...
- c (S).
...
- This
...
- amplification
...
- coefficient
...
- is
...
- suggested
...
- in
...
- AISC
...
- Guide
...
- 11,
...
- page
...
- 12.
...
Since
...
these
...
modular
...
ratio
...
are
...
different,
...
transformed
...
inertia
...
varies
...
between
...
strength,
...
deflection,
...
and
...
vibration
...
analysis.
...
| Show if | ||
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Related Incident: Creep factor 195684 - For both LRFD and ASD, Ec should be computed directly from ACI 8.5, though ETABS does not currently follow such process while implementing this formulation. This article reflects the current ETABS application process. Regardless, results are not affected since concrete density is manually input according to that specified for deck material within ACI 8.5. {hidden-content} |