design for two way slab

1. Two way slab

2. Two way slab
 Two way slab is supported by beams in all four sides.
 The ratio of longer span to shorter span (Ly/Lx) <2
than it is call two way slab.
 Main reinforcement is provided in both direction
incase of two way slab.

3. Cont.
 Load distribution in slab

4. Types of two way slab

6. Design steps for two way slab
 Step 1: Preliminary Design.
 Find depth of slab using deflection control criteria.
 Take span/d = 28 for simply supported slab and 32 for
continuous slab.
 D ≥ Dmin = 100mm for normal design and 125mm for
earthquake resistant design.
 Step 2: Analysis of Slab.
 Slab is analyzed by IS code method. (Ref. Annex D-1
and Annex D-2).

7.  Step 3: Design of Slab.
 Verify depth of slab ‘D’.
 Determine ‘Ast’ and ‘Φ’ and number of bars in shorter direction of
slab.
 Slab section is normally designed as Singly Reinforced Under
Reinforced Rectangular Section.
 Ast = Mu/(0.87fy(d-0.416xu)) which should not be less than
Astmin.
 Check slab for shear in shorter direction.

8.  Step 4: Check slab at limit state of serviceability in
deflection in shorter direction.
 l/d ≤ αβγδγ
 Step 5: Detailing of reinforcement:
 Curtail/bend the surplus bars as per detailing rules of code. (Ref.
Annex)
 Check development length at support.
 Ld ≤ 1.3Ml / Vu + ld
 Provide torsion reinforcement at the discontinuous edge of slab
as per codal provision.