Two-Way Concrete Slab - ladbs

Supplemental Structural Correction Sheet
Two-Way Concrete Slab
( 2002 LABC )
Plan Check No.
Checked by:
PLAN DETAILS
9 1. Drop panel shall extend in each direction not less than one sixth the span length in
that direction. (1913.3.7.1).~
9 2. Projection of drop panel below the slab shall be at least one fourth the slab thickness
beyond the drop. (1913.3.7.2).~
9 3. Provide minimum reinforcement ratio of 0.0018 in each direction (1913.3.1).~
9 4. Maximum rebar spacing at the critical sections is 2h, but not more than 18 in.
(1913.3.2).~
9 5. Provide minimum extensions for reinforcement in slabs without beams (flat plates and
flat slabs) per Fig. 19-1.~
9 6. Provide special top and bottom reinforcement at exterior corners in slabs with beams
between supports with a value of a greater than 1.0 (1913.3.6).~
9 7. At least two of the column strip bottom bars in each direction shall pass within column
core and be anchored at exterior supports. (1913.3.8.5).~
9 8. Not more than one eighth the width of column strip shall be interrupted by openings.
(1913.4.2.2)~
9 9. In the area common to one column strip and one middle strip, not more than one
fourth the reinforcement in either strip shall be interrupted by openings.
(1913.4.2.3).~
9 10. The critical slab sections should be modified per section 1912.5 for openings located
less than 10h from a concentrated load or openings in flat slabs within the column
strip. (1911.12.5).~
9 11. Direct Design Method can not be used because:
9 a) Slabs should not be designed as two-way slabs because the ratio of long to short
span is greater than two. (1913.6.1.2).~
9 b) There must be three or more continuous spans in each direction (1913.6.1.1);~
9 c) Successive span lengths center to center supports in each direction must not
differ by more than 1/3 of the longer span (1913.6.1.3);~
9 d) Columns must not be offset more than 10% of the span (in direction of offset)
from either axis between center lines of successive columns. (1913.4.1.4)~
9 e) Loads must be uniformly distributed, with LL # 2DL. (1913.6.1.5)~
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9 f) For two-way beam-supported slabs, relative stiffness of beams in two
perpendicular directions must satisfy the minimum and maximum requirements
in section 1913.6.1.6~
9 h) Redistribution of negative moments is not permitted. (1913.6.1.7)~
CALCULATIONS
9 1. Nominal shear stress Vn shall not be taken greater than 6 /f ’c b o d. (1911.12.3.2).~
9 2. Factored loads should be calculated per section 1612.1 and 1909.2.~
9 3. Special element _______ ______should be designed for special seismic load
combinations due to the irregularity (1612.4).~
9 4. Slab thickness is less than minimum slab thickness required by Code sec.1909.5.3,
provide short and long term deflection calculations using effective moment of inertia
(1909.5.3.4).~
9 5. Deflection should not exceed the limits in Table 19-C-2 in short, long and diagonal
directions where ln is the clear span length.~
9 6. Provide complete calculations for (one-way shear, two-way shear).~
9 7. Unbalanced moment should be transferred by a combination of flexure and
eccentricity of shear (1913.5.3).~
9 8. Effect of slab cracking and reinforcement on stiffness of frame members should be
taken into account for lateral load analysis. (1913.5.1.2).~
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