1) The document outlines the preliminary design steps for a slab with inner dimensions of 4x3.6 meters. 2) In step 1, load calculations are performed to determine the factored load of 9 kN/m. 3) In step 2, design moments are calculated at supports and mid-spans along the short and long spans. 4) In step 3, the effective depth is checked and found to be sufficient at 42.56mm, so the total depth is set at 120mm.

1. PRELIMINARY DESIGN OF SLAB
STEP 1:-
LOAD CALCULATIONS
Inner dimensions = (4×3.6) m2
Assuming fy = 415 N/mm2
Fck = 20 N/mm2
Effective span (Lx) = 3.6m
Effective span (Ly) = 4 m
Aspect ratio (Ly/Lx) = [4/ 3.6] = 1.1 < 2
Assume over all depth of slab = 120 m
Effective depth = 120 – 15-10/2 = 100mm
Self weight of slab = 0.12 × 25 =3 kN/m2
Live load = 2kN/m2
Dead load = 1kN/m2
Total weight = 6kN/m2
Load per meter run = 6.0 × 1.0 = 6.0kN/m
Factored load = 1.5 × 6.0 = 9.0 kN/m
Edge condition = Interior panel.
STEP 2:-
DESIGN MOMENTS
Using bending moment coefficients from table – 26 of IS 456:2000, the bending moments are
calculated as follows.
Mx=αxwLx
2 My=αywLx
2
BENDING MOMENTCOEFFICIENTS
AT SUPPORTS AT MID SPAN
ALONG SHORT SPAN (αx) - 0.037 0.028
ALONG LONG SPAN (αy) -0.032 0.024

2. BENDING MOMENTS
AT SUPPORTS (kN-m) AT MID SPANS (kN-m)
ALONG SHORT SPAN Mx (-ve) = -4.3 Mx (+ve) = 3.2
ALONG LONG SPAN My (-ve) = -3.73 My (+ve) = 2.79
STEP:-3
CHECK FOR EFFECTIVE DEPTH
Maximum bending moment (Mu) = 0.138 × fck × bd2
4.3 ×106 = 0.138 × 20 × 1000 × d2
d = 42.56 mm < 100.00mm
Therefore, provide total depth of slab( D) = 120mm
S.NO SPAN(m x m) EDGE CONDITION REQUIRED
DEPTH(mm)
PROVIDED
DEPTH(mm)
1 3 x 6.1 Two Adjacent edges
Discontinuous
51.6 100
2 3 x 3.6 One Long Edge
Discontinuous
39 100
3 2 x 3 One Short Edge
Discontinuous
27.2 100
4 4 x 3.6 One Short Edge
Discontinuous
42 100
5 1.5 x 6.1 One short edge
Discontinuous
27.5 100
6 3 × 6.1 One short edge
Discontinuous
44.6 100
7 4 × 6.1 One short edge
Discontinuous
54 100
8 4 × 3.6 Interior panel 42.56 100
9 4 × 2 Interior panel 29.11 100
10 3 × 3.6 Interior panel 35.5 100
11 1.5× 3.6 Interior panel 33 100
12 3 × 2 Interior panel 26.3 100
13 1.5 × 2 Interior panel 18.15 100