This document summarizes the analysis and design of a slab bridge. It outlines the design process, considerations, and calculations for the deck slab and abutments. For the deck slab, calculations are shown for bending moment, shear force, reinforcement requirements, serviceability checks for cracking and deflection. The abutment design process involves calculating loads, earth pressure coefficients, and designing the stem, return wall, dirt wall, and cap while checking design requirements.

1. ADICHUNCHANAGIRI INSTITUTE OF TECHNOLOGY
“ANALYSIS AND DESIGN OF SLAB BRIDGE”
BATCH NUMBER : 09
Sri Adichunchanagiri Shikshana Trust
Chikkamagaluru – 577102, Karnataka
(Affiliated to Visvesvaraya Technological University, Belagavi,
Approved by AICTE, New Delhi and Recognised by Govt. of Karnataka)
ACCREDITED BY NAAC,NBA, ISO 9001:2008 CERTIFIED
Department of Civil Engineering
Presentation on
Hemanth BT - 4AI20CV414
Rachel Shareen - 4AI19CV051
Bharath AG - 4AI19CV086
TD Karthik - 4AI19CV075
CO-ORINATORS
Mr. Abhilash D T & Mr. Goutham D R
Assistant Professor
Civil Department
UNDER THE GUIDANCE OF
Mr. Naveen kumar S M
Assistant professor
Civil department

2. Design Of Deck Slab
Following are data's considered for deck slab design
Carriage way – 2
Foot Paths – 1m on either side
Clear span – 6m
Wearing Coat – 80mm
Width of bearing – 400mm
Materials – M25 Grade concrete & Fe-415 Grade HYSD bars
Loading – IRC Class AA tracked vehicle
Design will be done based on limit state of serviceability considerations of
limiting deflections

3. Procedure:
1) Depth of slab & Effective Span
Ratio of span/depth (L/d) = 12-15
 For (L/d) = d = Span/15 , d = 400 mm
 For (L/d) = d = Span/12 , d = 500 mm
 Depth of slab = (80x6) = 480 mm
 Adopt overall depth of slab, h = 500 mm = 0.5 m
 Clear Cover = 40 mm
 Effective Depth = 450 mm = 0.45 m
Effective Span
Least of the following
a) Clear span + Effective depth = 6.45 m
b) Centre to Centre of Bearings = 6.4 m
Clear span = 6.4 m

4. 2) Calculation of Bending Moment
Calculation of Dead Load Bending Moment
For IRC Class AA tracked vehicle loading
Dead Load Bending Moment
Total Dead load = 14 KN/m2
Dead load Bending Moment = 72 KN-m
Live Load Bending Moments
Impact factor for IRC Class AA tracked vehicle
For 5m span = 25%
For 9m span = 10%
For 6.4m span
Impact Factor = 19.70%
The tracked vehicle is placed symmetrically on the span.

5. Effective length of load = 4.76 m
Effective width of slab perpendicular to span is expressed as, be=Kx(1-x/L)+bw
be = 5.55 m
The tracked vehicle is placed close to the kerb with the required minimum clearance
as shown in fig.
Net effective width of dispersions = 7.455 m
Total load of 2 tracks with impact = (700x1.197) = 838 KN
Avg Intensity of load = (838/(4.76x7.455)) = 24.02 KN/m2
Maximum Bending Moment due to live load = 114 KN-m
Total design bending moment = (113+72) = 186 KN-m
Ultimate moment = (1.35Md+1.5Ml) = 267.9 KN-m/m

6. Shear due to class AA Tracked Vehicle
Effective width of dispersion is given by be = Kx 1 −
x
L
+ bw
be = 5.256 m
Width of dispersion = 7.303m
Avg Intensity of load = (838/(4.76x7.303)) = 24.52 KN/m2
Shear Force = VA = ((24.1x4.76x4.02)/6.4) = 72 KN
Dead Load Shear = (0.5(14x6.4) = 45 KN
Total Design Shear Force = (72+45) = 117 KN
Total design ultimate shear force = (1.35Vd+1.5VL) = 169 KN/m
Design of Deck Slab
Using M25 grade concrete & Fe 415 HYSD bars
d =
𝑀𝑢
0.138𝑓𝑐𝑘𝑏
d = 279 mm

7. Area of Reinforcement is calculated using the equation, Mu = 0.87fyAstd(1 −
Astxfy
bdfck
)
Ast = 1758 mm2
Using 20mm dia bars
d= 20 mm
ast = 314.2 mm2
Spacing, S= 178.7 mm
Provide 20mm dia @ 150mm c/c
Astpro = 2094 mm2
Distribution steel
Transverse moment = (0.3MuL + 0.2MuD)
MuL = (1.5x114) = 171.12 KN-m
MuD = (1.35x72) = 97.3 KN-m
Transverse moment= 70.8 KN-m
Area of steel, Ast =
2094
267
x71 = 553.38 mm2
Provide 12mm @ 200 mm c/c
Check for ultimate flexural strength. Mu = 0.87fyAstd(1 −
Astxfy
bdfck
)
Mu = 314 KN-m > 267 KN-m
Hence Safe.

8. Check for ultimate flexural strength.
Mu = 0.87fyAstd(1 −
Astxfy
bdfck
)
Mu = 314 KN-m > 267 KN-m
Hence Safe.
Check for ultimate shear strength
Ultimate Shear Strength, VRdc = (0.12K(80P1fck)0.33)x bwd
K = 1 +
200
d
≤ 2
K = 1.67
P1 =
Ast
bwd
≤ 0.02
P1 = 0.00465333
VRdc = 187908 = 188 KN
188 KN >169 KN

9. Check for serviceability limit states:
a) Limit state of cracking
Crack width computations by Rigorous Analysis
Width of crack, Wk = Sr max (εsm – εcm)
(εsm – εcm) =
𝜎𝑠−𝐾𝑡(
𝑓𝑐𝑡,𝑒𝑓𝑓
𝑃𝑝𝑒𝑓𝑓
)(1+𝛼𝑒𝑃𝑝,𝑒𝑓𝑓)
𝐸𝑆
≥ 0.6(
𝜎𝑠
𝐸𝑠
)
399(
212−0.4(
2.2
0.0167
)(1+6.66x0.0167)
200x103 ) = 0.26 mm
i.e 0.26 ≥ 0.6
σs
Es
≥ 0.6
212
200x103 ≥ 0.0006 mm
The max crack width is less the permissible value 0.3 mm
Hence safe.

10. b) Limit state of Deflection
The deflection due to shrinkage can be computed by the relation , acs = kψcsL2
K = a constant = 0.125 for SSB
Ψcs = shrinkage curvature = (δcsαe(S/I))
εcs= total shrinkage strain = (εcd + εca)
εcd is the drying shrinkage strain
εca is the autogenous shrinkage strain
The development of drying shrinkage strain with time is expressed as εcd (t) = (βds(t,ts)Knεcd)
where, 𝛽𝑑𝑠 𝑡,𝑡𝑠 =
𝑡−𝑡𝑠
𝑡−𝑡𝑠 +0.04√ℎ𝑜3
acs = (KψcsL2)
acs = ((0.125x69494x10-12)x64002) = 0.355 mm

11. 2) Long term deflection due to sustained dead load
Total dead load = g = 14 N/mm
Effective span = L = 6400 mm
Ec = 30KN/mm2 = 30000 N/mm2
Ieff = 2.82x109 mm4
Max short-term deflection due to load = ag =
5gL4
384EcI
= 3.62 mm
Final creep co-efficient of concrete = depend upon the national size, age at loading
and the atmospheric conditions as given in table 4.12 𝐸𝑐, 𝑒𝑓𝑓 =
𝐸𝑐
1+∅
hence, (1+ɸ)=3.6 & Ec, eff = (Ec/3.6)
long term deflection due to permanent loads = (3.6x3.62) = 13.03 mm

12. Deflection due to live load :
The live load due to the IRC class AA backed vehicle is computed as 23.61 kN/m2
spaced over a length of 4.76m at center of span at 6.4m.
aq =
5gL4
384EcIeff
=
5x23.61x64004
384x30000x2.82x109 = 6.08 mm
Hence the final deflection is computed as the sum of shrinkage, dead load with
creep and live load deflection.
Final deflection = [0.355+13.60+6.08] = 29.46mm
maximum deflection due to L.L (6.08mm) =(aq) ≤ (span/800) ≤ 8mm
Total maximum deflection (22.03mm) ≤ (span/250) ≤ 256mm
Hence serviceability limit state of deflection is well within the
limits specified in the IRC : 112 - 2011 code.

14. Design Of Abutment
Steps involved in Design Process:
 Calculation of Load from Abutments
 Calculating Earth Pressure Co-efficients
 Calculation of loads on the Abutment Self weight, Soil weights & CG of soil,Earth pressure,
Horizontal & Vertical forces, Live load, Load from super structure, longitudinal bearing forces,
wind load, water current, seismic forces.
 Load Combinations
 Design of Abutment Stem
 Design of Return Wall
 Design of Dirt Wall
 Abutment Cap
 Checks