Section 18.9.3.2
Midspan Two Way Minimum Reinforcement
For a cantilever span (as
determined by the declaration of supports in the design strip segment), this
criterion is ignored if the section location is inside of L/3 of the support.
For a regular span (as
determined by the declaration of supports in the design strip segment), this
criterion is ignored if the section location closer than L/6 from a support.
For a span with no supports
(as determined by the declaration of supports in the design strip segment),
this criterion is always applied.
See
"Minimum Reinforcement" above for details regarding
which slab/beam face (top or bottom) that the reinforcement will have the
reinforcement added.
For strict adherence to ACI
318-99 this criterion should only be used for two-way slabs of uniform
thickness ( RAM Concept uses it for all slabs declared as
"two-way"; section 18.9.2 should be used for two-way
slabs that do not have a uniform thickness. Under ACI 318-02 and IBC 2000 it is
acceptable to use this criterion for all two-way slabs.)
Gross-section,
linear-elastic stress calculations are used.
For sections with multiple
concrete strengths, the minimum concrete strength is used to determine the
limiting stress.
For sections with multiple
concrete strengths, approximate extreme fiber stresses and centroid stresses
are calculated and reported.
If is exceeded the entire tensile load, Nc, is taken
by bonded reinforcement.
User defined reinforcement
on the appropriate face and bonded post-tensioning that is in the tension zone
is counted toward the requirement. Vector components are taken of reinforcement
and bonded post-tensioning that are not orthogonal to the cross section. Usable
bonded tendon stresses are limited to the minimum of (fpy-fse), (0.5
fpy) and 30 ksi.
Reinforcing bar stresses
are limited to the minimum of (0.5
fpy) and 30 ksi.
The reinforcement is only provided where stresses
exceed , the minimum length requirements of 18.9.4.1 are considered with code
span detailing requirements.
No check is made to ensure
that the structure is post-tensioned.