4 · Cantilever Slab Design
Fixed at the support, free at the tip — maximum moment and top steel at the support face.
Average depth
(D,support + D,free)/2
150mm
Self weight
γc × D,avg = 25 × 0.150 m
3.75kN/m²
Total dead load
self weight + SDL
5.75kN/m²
Design load, wuTable 18
1.5 (DL + LL)
13.13kN/m²
Effective depth at support, d
D,support − cover − ø/2
174mm
Effective span, leffCl. 22.2(c)
clear projection + d/2
1.587m
Design moment, Mu
wu · leff² / 2 = 13.13 × 1.587² / 2
16.528kN·m/m
Mu,lim
0.1336 · fck · b · d²
101.126kN·m/mOK
Ru = Mu/(b·d²)
0.546N/mm²
pt required
0.1288%
pt minimumCl. 26.5.2.1
0.12 % of b·D
0.12%
Ast required — TOP face
240mm²/m
Spacing required
471.2mm
Maximum spacingCl. 26.3.3
min(3d, 300 mm)
300mmOK
Ast provided
905mm²/mOK
Main steel must be at the TOP face and anchored into the supporting member for a development length beyond the point of support (Cl. 26.2.1).
Vu
wu · leff = 13.13 × 1.587
20.829kN/m
τv = Vu/(b·d)
0.120N/mm²
100·Ast/(b·d)
0.520
τcTable 19
0.497N/mm²
k · τcCl. 40.2.1.1
0.596N/mm²
Verdict
No shear reinforcement required (Cl. 40.2.3)OK
Basic l/d for cantileversCl. 23.2.1
7
pt provided
0.520%
fs
0.58·fy·(Ast,req/Ast,prov)
76.9N/mm²
Modification factorFig. 4
2.0000
Allowable l/d
14.000
Provided l/d
9.121OK
| Location | Bar | Spacing | Ast req. | Ast prov. | Status |
|---|---|---|---|---|---|
| Main steel — TOP, along the projection | ø12 | 125 mm c/c | 240 mm²/m | 905 mm²/m | OK |
| Distribution steel — transverse | ø8 | 200 mm c/c | 240 mm²/m | 251 mm²/m | OK |