DESIGN OF A R.C.C MOUNTABLE DRAIN SLAB COVER :
200
200 1700
A
B
C
Design Data: Overall width of Slab Slab type Support width Effective span Exposure condition Clear cover Grade of Concrete 'fck' Grade of Steel 'fy' Unit wt of concrete, Live load over Slab Desgn of Slab: Tr T rial Slab thickness Re R eqd. min effective slab thick, 'd' Ef Effective cover consd. 12mm dia bar Ov O verall Slab thick. Ov Overall Slab thick 'D' considered Ef Effective Slab thick 'd' considered Loads Dead Load, WDL (self wt of Slab) Factored Total Load Wu
: : : : : : : : : : : : : : : : :
a) Ult. Dead Load BM, M uD
1700 mm On One-way/simply supported over drain walls. 200 mm 1500 mm Mo Moderate 30 mm 25 Mpa 415 Mpa 25 kN/m^3 IRC Class-B Class-B Considering Considering 1m wide strip strip of Slab Slab 75 36 1 11 120 84
mm mm mm mm mm mm mm mm mm
: :
3.00 kN/m^2 4.50 kN/m^2
:
1.27 kN-m/m
b) Ult. Ult. Live Load BM : For max. live load BM, one wheel load of 34 kN of IRC Class 'B' is placed at the center of the span, as shown below. 1000
X I.R.C. CLASS-B LOADING ONE-WHEEL LOAD OF 34 KN
0 0 5 1 = l
bB
w 34KN W
W
B
Conc. Axle load, P Wheel contact area, bxw Load dispersed area, B x W Dist. 'X' of C.G. of conc. Load Constant 'k' effective width,
= 34 = 200 x 380 = 425 x 605 = 750 = 2.07
X kX 1 W l
kN mm x mm mm x mm mm
=
1.38 m
=
1.00 m
be/2+X
=
1.44
Effective width, be considered
=
1.00 m
Max. B.M at the center of Span, M 0
=
10.18 kN-m
Max. B.M per unit width, M 0/be
=
10.18 kN-m/m
Design live load Moment, M uL
=
15.27 kN-m per m width
Design DL + LL Moment, M u
=
16.53 kN-m per m width
be
width of the Slab
Minimum eff. depth reqd. = 77.40 mm < consd. Eff. Depth, Safe Required Main Steel, Ast = 621.85 mm^2 Min. Steel, Ast,min 144 mm^2 for # 12 mm dia bar, spacing reqd., 182 mm Maximum Spacing allowed 252 mm < reqd. spacing Maximum dia of main bar allowed 15 mm > 12mm O.K. Provide, #12mm @ 150 mm c/c as main Steel at bottom with alternate bar bent up at support Distrbution Steel required Resisting Moment 4.83 kN-m Required dist. steel, Ast = 164.82 mm^2 for # 8mm dia bar, spacing reqd., 305 mm Maximum Spacing allowed 300 mm Provide, # 8mm @ 250 mm c/c as dist Steel at bottom & at top near support.
2
150
150 1 1700 CROSS-SECTION OF SLAB
THICKNESS OF SLAB= 120mm CLEAR COVER= 30mm BAR-MARK 1= # 12 @ 150mm c/c, Alternate bar bent up at support. BAR-MARK 2= # 8 @ 250mm c/c.
250
Provide 02 NOS. # 16 mm U-clip for lifting & transporting the Slab strip of size-1.00m x 1.70m
0 6
300 0 6
300 TYP. DETAIL OF U-CLIP
B/l 0.60 0.67 0.70
k 1.96 2.07 2.12