design of 10m clear span slab bridge

Construction of 10.00mts span culvert at 5/6 KM of Vemuladeevi channel

Name of the work:-Construction of bridge across Dharbharevu canalon Gopuram road near Anjaneyaswamy temple in Pedalanka(V)

Design Philosophy:-

The design of 1V-- 10.37m right span culvert is carried as per the procedure out lined

below:-

Step1:-

The design discharge was fixed after arriving discharge based on the following methods:-

and area by considering actual cross-section of the channel.

Step2:-

The vertical clearence and afflux are verified.

below the maximum scour depth

Step3:-

The structural components are desined in the following manner:-

and culverts of medium importance is selected.

designed as per the guide lines given in relevent IRC codes.

a.As per the hydraulic particulars furnished by the Irrigation department

b.By Area-Velocity method using Manning's equation for arriving at the flow velocity

a.Hydraulic particulars like HFL,OFL are obtained from Irrigation department.

b.Bottom of deck level was fixed based on HFL and road formation levels on both sides.

c.Ventway calculations are done for fixation of ventway.

d.Normal scour depth with reference to HFL was calculated using Lacey's equations

e.After arriving at the Maximum scour depth,bottom level of the foundation was fixed

After arriving at bottom of deck level,bottom of foundation level and required ventway,the dimensions of the bridge are finalised.

a.As per the recommendations of IRC 6:2000,IRC class A live load required for bridges

b.Load combination is selected as per IRC 6:2000

c.Based on the trial pit particulars and soil test reports,type of foundation was selected.

d.The structural components like Abutment,raft foundation are

e.The deck slab is proposed as per the MOST drawing Nos.BD 3-74&BD 4-74

f.The dirt wall is proposed as per the drawings given in Plate No.7.25 of IRC:SP20-2002(Rural roads manual)

Design of Abutments

I)Design Parameters:-

Clear Right Span = 10.00m

= 10.740m

Width of the carriage way = 5.50m

= 0.790m

= 0.075m

= 1.200m

Thickness of dirt wall = 0.30m

Sectional area of dirt wall = 0.440sqm

Thickness of RAFT footing = 0.70m

Height of abutments = 1.664m

(As per hydralic calculations)

Top width of abutments = 0.690m

Bottom width of abutments = 2.00m

Sectional area of abutment section = 2.238sqm

Bank side batter of abutment = 1.310m

Stream side batter of abutment = 0.000m

Width of 1st footing = 2.30m

Thickness of 1st footing = 0.30m

= 0.15m

Bank side offset of 1st footing wrt abutment = 0.15m

= 2.45m

= 0.30m

= 0.30m

Bank side offset of 2nd footing wrt abutment = 0.15m

Width of 3rd footing = 0.00m

Thickness of 3rd footing = 0.00m

Canal side offset of 3rd footing wrt abutment = 0.00m

Bank side offset of 3rd footing wrt abutment = 0.00m

Width of VRCC RAFT footing = 6.55m

= 0.60m

Type of bearings = No bearings proposed

= 25KN/cum

= 24KN/cum

= 18KN/Cum

= 10KN/Cum

Deck slab length

Thickness of deck slab as per MOST Dg.BD 3-74

Thickness of wearing coat

Height of railing

Canal side offset of 1st footing wrt abutment

Width of 2nd footing

Thickness of 2nd footing

Canal side offset of 2nd footing wrt abutment

Thickness of VRCC RAFT footing

Unit weight of RCC (yrc)

Unit weight of PCC (ypc)

Density of back fill soil behind abutments (y)

Unit weight of water (yw)

= 30

= 51.81

= 0

= 15

= 1.20m

= 2.862m

= 0.488m

= 1.488m

= -1.512m

= 6.00t/sqm

= 25.00N/sqmm

= 415.00N/sqmm

Cover to reinforcement = 50.00mm

II)General loading pattern:-

As per IRC:6---2000,the following loadings are to be considered on the bridge or slabculvert:-

1.Dead load2.Live load3.Impact load4.Wind load5.Water current6.Tractive,braking effort of vehicles&frictional resistance of bearings7.Buoyancy8.Earth pressure9.Seismic force10.Water pressure force

As per clause 202.3,the increase in permissible stresses is not permissible for theabove loading combination.

III)Loading on the slab culvert for design of abutments:-

1.Dead Load:-

i)Self wieght of the deck slab = 583.32KN

ii)Self wieght of dirtwall over abutment = 60.50KN

iii)Self weight of wearing coat = 55.38KN

699.20KN

There is no need to consider snow load as per the climatic conditions

Angle of shearing resistance of back fill material(Q)

Angle of face of wall supporting earth with horizontal(In degrees)(in clock wise direction)(a)

Slope of back fill (b)

Angle of wall friction (q)

Height of surcharge considered (h3)

Road crest level (RTL)

Low bed level (LBL)

High flood Level (HFL)Bottom of foundation level (BFL) Safe Bearing Capacity of the soil (SBC)

Compressive strength of concrete for RCC Strip footing (fck)

Yield strength of steel (fy)

Self wieght of the abutments upto bottom most footing based on the preliminary section assumed:-

iv)Self wieght of the abutment section = 295.42KN

v)Self wieght of top footing = 91.08KN

vi)Self wieght of 2nd footing = 97.02KN

vii)Self wieght of 3rd footing = 0.00KN

viii)Self wieght of 4th footing = 0.00KN

483.52KN

ix)Calculation of eccentricity of self weight of abutment w.r.t base of abutment

S.No Description Load in KN Moment

1 143.86944 1.127 162.14

2 151.55712 0.345 52.29

3 0 0 0

295.42656 214.43

Location of resultant from toe of abutment = 0.73m

Distance of centroid of load from toe of abutment

Back batter(W1)

Centre portion(W2)

Front batter(W3)

W1W1

Eccentricity wrt centre of base of abutment = 0.270m

x)Calculation of eccentricity of self weight of abutment&1st footing w.r.t bottom of 1st footing


1 Back batter 143.86944 1.277 183.72

2 Centre portion 151.55712 0.495 75.02

3 Front batter 0 0 0

4 1st footing 91.08KN 1.15 104.74

386.50656 363.48


Eccentricity wrt centre of 1st footing= 0.210m

xi)Calculation of eccentricity of self weight of abutment,1st&2nd footings w.r.t bottom of 2nd footing

Distance of centroid of load from toe of 1st footing


1 Back batter 143.86944 1.427 205.3

2 Centre portion 151.55712 0.645 97.75

3 Front batter 0 0.3 0

4 1st footing 91.08KN 1.300 118.4

5 2nd footing 97.02KN 1.225 118.85

483.52656 540.3


Eccentricity = 0.105m

xii)Calculation of eccentricity of self weight of abutment,1st&2nd footings w.r.t bottom of 2nd footing


1 Back batter 0 1.427 02 Centre portion 0 0.645 03 Front batter 0 0.3 04 1st footing 0 1.00 05 2nd footing 0 0.92 06 3rd footing 0 0.00 0

0 0



2.Live Load:-

As per clause 201.1 of IRC:6--2000,the bridges and culverts of medium importance

GENERAL IRC Class-A loading Pattern

Distance of centroid of load from toe of 2nd footing

Distance of centroid of load from toe of 3rd footing

are to be designed for IRC Class A loading.

2.7t

2.7t

11.4

t

11.4

t

6.8t

6.8t

6.8t

6.8t

1.10

1.80

3.20 1.20 4.30 3.00 3.00 3.00

2.7t

2.7t

11.4

t

11.4

t

6.8t

6.8t

6.8t

6.8t

1.10

1.80

3.20 1.20 4.30 3.00 3.00 3.00

clauses 207.1.3&207.4

The ground contact area of wheels for the above placement,each axle wise isgiven below:-

Axle load Ground Contact Area(Tonnes) B(mm) W(mm)

11.4 250 5006.8 200 380

The IRC Class A loading as per the drawing is severe and the same is to be considered as per

Y

X

11.4t

11.4t

6.8t

6.8t

475

5500

Portion to be loadedwith 5KN/m² liveload

10000

35252925

11380

2.7 150 200

Assuming 0.475m allowance for guide posts/kerbs and the clear distance of vehicle from

the edge of guide post being 0.15m as per clause 207.1,the value of 'f' shown in the figure will

be 0.625m

0.625m

3.525m

4.15m

The total live load on the deck slab composes the following components:-

1.Wheel loads----Point loads 364.00KN

2.Live load in remaing portion(Left side)----UDL 33.56KN

2.Live load in remaing portion(Right side)----UDL 189.29KN

586.86KN

Resultant live load:-

Eccentricity of live load w.r.t y-direction(Along the direction of travel of vehicles)

Taking moments of all the forces w.r.t y-axis

S.No Distance from Y-axis Moment

1 57 0.875m 49.88KNm

2 57 0.875m 49.88KNm

3 57 2.675m 152.48KNm

4 57 2.675m 152.48KNm

5 34 0.875m 29.75KNm

6 34 0.875m 29.75KNm

7 34 2.675m 90.95KNm

8 34 2.675m 90.95KNm

9 33.5625 0.313m 10.49KNm

10 189.2925 4.688m 887.31KNm

Hence,the width of area to be loaded with 5KN/m2 on left side is (f) =

Similarly,the area to be loaded on right side (k) =

Wheel Load/UDL in KN

586.855 1543.90KNm

Distance of centroid of forces from y-axis

= 2.631m


Eccentricity of live load w.r.t x-direction(At right angle to the travel of vehicles)

Taking moments of all the forces w.r.t x-axis

S.No Load in KN Distance from X-axis Moment

1 57 11.005m 627.29KNm

2 57 11.005m 627.29KNm

3 57 9.805m 558.89KNm

4 57 9.805m 558.89KNm

5 34 5.505m 187.17KNm

6 34 5.505m 187.17KNm

7 34 2.505m 85.17KNm

8 34 2.505m 85.17KNm

9 33.56KN 5.690m 190.97KNm

10 189.29KN 5.690m 1077.07KNm

586.855 4185.06KN

Distance of centroid of forces from x-axis

= 7.131m


Y

X5500

10000

Location of Resultant

2631

7131

11380

Calculation of reactions on abutments:-

367.74KN

219.12KN

Hence,the critical reaction is Ra = 367.7KN

The corrected reaction at obtuse corner = 367.74KN

Assuming that the live load reaction acts at the centre of the contact area on the abutment,

Reaction due to loads Ra =

Reaction due to point loads = Rb =

300

300

185

815815

740

Y

X5500

10000

Location of Resultant

2631

7131

11380

The eccentricty of the line of action of live load at bottom of abutment = 0.815m

----do----on top of 1st footing = 0.815m

----do----on top of 2nd footing = 0.740m

The eccentricity in the other direction need not be considered due to high section modulus in transverse direction.

3.Impact of vehicles:-

As per Clause 211 of IRC:6--2000,impact allowance shall be made by an increment

of live load by a factor 4.5/(6+L)

Hence,the factor is 0.269

Further as per clause 211.7 of IRC:6--2000,the above impact factor shall be only

50% for calculation of pressure on piers and abutments just below the level of bed block.There

is no need to increase the live load below 3m depth.

As such,the impact allowance for the top 3m of abutments will be 0.1345

For the remaining portion,impact need not be considered.

4.Wind load:-

The deck system is located at height of (RTL-LBL) 2.37m

The Wind pressure acting on deck system located at that height is considered for design.

As per clause 212.3 and from Table .4 of IRC:6---2000,the wind pressure at that hieght is=

59.48

Height of the deck system = 2.065

Breadth of the deck system = 11.38

Kg/m2.

300

300

185

815815

740

The effective area exposed to wind force =HeightxBreadth =

Hence,the wind force acting at centroid of the deck system = 6.97KN(Taking 50% perforations)

Further as per clause 212.4 of IRC:6---2000 ,300 Kg/m wind force is considered to be

acting at a hieght of 1.5m from road surface on live load vehicle.

Hence,the wind force acting at 1.5m above the road surface = 16.50KN

The location of the wind force from the top of RCC raft footing = 4.93m

5.Water current force:-

Water pressure considered on square ended abutments as per clause 213.2 of IRC:6---2000 is

26.286

(where the value of 'K' is 1.5 for square ended abutments)

For the purpose of calculation of exposed area to water current force,only 1.0m

width of abutment is considered for full hieght upto HFL

Hence,the water current force = 0.62KN

Point of action of water current force from the top of RCC raft footing = 3.77m

6.Tractive,braking effort of vehicles&frictional resistance of bearings:-

The breaking effect of vehicles shall be 20% of live load acting in longitudinal

direction at 1.2m above road surface as per the clause 214.2 of IRC:6--2000.

As no bearings are assumed in the present case,50% of the above longitudinal

force can be assumed to be transmitted to the supports of simply supported spans resting on

stiff foundation with no bearings as per clause 214.5.1.3 of IRC:6---2000

Hence,the longitudinal force due to braking,tractive or frictional resistance of

bearings transferred to abutments is

58.69KN

The location of the tractive force from the top of RCC raft footing = 4.63m

7.Buoyancy :-

P = 52KV2 = Kg/m2.

As per clause 216.4 of IRC:6---2000,for abutments or piers of shallow depth,the dead weight of the abutment shall be reduced by wieght of equal volume of water upto HFL.

The above reduction in self wieght will be considered assuming that the back fill behind the abutment is scoured.

For the preliminary section assumed,the volume of abutment section is

i)Volume of abutment section = 12.31Cum

ii)Volume of top footing = 3.80Cum

iii)Volume of 2nd footing = 4.04Cum

iv)Volume of 3rd footing = 0.00Cum

v)Volume of 4th footing = 0.00Cum

20.15Cum

Reduction in self wieght = 201.47KN

8.Earth pressure :-

As per clause 217.1 of IRC:6---2000,the abutments are to be designed for a

surcharge equivalent to a back fill of hieght 1.20m behind the abutment.

The coefficient of active earth pressure exerted by the cohesion less back fill on

the abutment as per the Coulomb's theory is given by

'2Sin(a+Q)

sina sin(a-q) sin(Q+q)sin(Q-b)

sin(a+b)

Sin(a+Q) = SIN[3.14*(51.81+30)/180] = 0.99Sin(a-q) = SIN[3.14*(51.81-15)/180] = 0.599Sina = SIN[3.14*(51.81)/180] = 0.786Sin(Q+q) = SIN[3.14*(30+15)/180] = 0.707Sin(Q-b) = SIN[3.14*(30-0)/180] = 0.5Sin(a+b) = SIN[3.14*(51.81+0)/180] = 0.786

From the above expression,

0.76

The hieght of abutment above GL,as per the preliminary section assumed = 1.664m

Hence,maximum pressure at the base of the wall Pa = 22.76KN/sqm

Ka =

Ka =

The pressure distribution along the height of the wall is as given below:-

Surcharge load = 16.42 KN/sqm

16.42

1.664

22.76 16.42

Area of the rectangular portion = 27.32Area of the triangular portion = 18.94

46.26

Taking moments of the areas about the toe of the wall

S.No Description Area Lever arm Moment

1 Rectangular 27.32 0.832 22.730242 Triangular 18.94 0.55466667 10.50538667

46.26 33.23562667

Height from the bottom of the wall = 0.72m

The active Earth pressure acts on the abutment as shown below:-

0.70

53.191.664m

0.72m

51.81

2.000.57

Total earth pressure acting on the abutment P = 254.43KN

152.54KN

203.63KN

Eccentricity of vertical component of earth pressure = 0.43m

9.Siesmic force :-

As per clause 222.1 of IRC:6---2000,the bridges in siesmic zones I and II need not be

designed for siesmic forces.The location of the slab culvert is in Zone-I.Hence,there is no need to

design the bridge for siesmic forces.

10.Water pressure force:-

The water pressure distribution on the abutment is as given below:-

HFL 1.488m

3.00

BFL -1.512m

Horizontal component of the earth pressure Ph =

Vertical component of the earth pressure Pv =

30.00kn/sqm

Total horizontal water pressure force = 247.50KN

The above pressure acts at height of H/3 = 1.00m

IV)Check for stresses for abutments&footings:-

a)Load Envelope-I:-(The Canal is dry,back fill scoured with live load on span)

i)On top of RCC raft

The following co-ordinates are assumed:-

a)x-Direction-----At right angle to the movement of vehicles

b)y-Direction-----In the direction of movement of vehicles

S.No Type of load

1 Reaction due to dead load from super structure 699.20KN -0.740 0.00

2 Self wieght of abutment&footings 483.53KN 0.105 0.000

3 466.66KN -0.740 0.000

4 Impact load 0.00 0.00 0.00

1649.38

S.No Type of load Direction x or y

1 Wind load 16.50KN x-Direction 4.93

2 Tractive,Braking&Frictional resistance of bearings 58.69KN y-Direction 4.63

3 Water current force 0.62KN x-Direction 3.77

Check for stresses:-

About x-axis:-

Breadth of 2nd footing b = 6.25m

Depth of 2nd footing d = 2.45m

Area of the footing = A = 15.3125

Section modulus of bottom footing 6.25

about x-axis --Zx =

Vertical forces acting on the abutment (P) composes of the following components

Intensity in KN

Eccentricty about x-axis(m)

Eccentricty about y-axis(m)

Reaction due to live load with impact factor---(Wheel loads+UDL)

Horizontal forces acting/transferred on the abutment (H) composes of the following components

Intensity in KN

Location(Ht.from the section considered).(m)

m2

(1/6)bd2 = m3

For M20 grade of concrete permissible compressive stress in direct compreession is 5N/mm2

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load

Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN -0.740 13.222 Self wieght of abutment&footings 483.53KN 0.105 34.763 Reaction due to live load with impact factor 466.66KN -0.740 8.834 Impact load 0.00KN 0.000 0

Horizontal loads:- (Stress = M/Z)5 Tractive,Braking&Frictional resistance of bearings 58.69KN 4.63 -43.46

13.35

S.No Type of load Eccentricity

Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN 0.740 78.12 Self wieght of abutment&footings 483.53KN -0.105 28.393 Reaction due to live load with impact factor 466.66KN 0.740 52.134 Impact load 0.00KN 0.000 0

Horizontal loads:- (Stress = M/Z)5 Tractive,Braking&Frictional resistance of bearings 58.69KN 4.63 43.46

202.08

Stress at heel = P/A(1+6e/b)+M/Z = 13.35 KN/Sqm>-2800KN/sqm.

Hence safe.

Stress at toe = P/A(1+6e/b)+M/Z = 202.08 KN/Sqm<5000KN/sqm

Hence safe.

About y-axis:-

Breadth of 3rd footing b = 2.45m

Depth of 3rd footing d = 6.25m

Area of the footing = A = 15.3125

Section modulus of bottom footing about = 15.95

y-axis--Zy =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

For M20 grade of concrete permissible tensile stress in bending tension is -2.8N/mm2

Intensity in KN (P)

Eccentricity/Lever arm

Stress at heelP/A(1+6e/b)

Intensity in KN (P)

Stress at toeP/A(1+6e/b)

m2

(1/6)bd2 = m3



S.No Type of load

Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN 0.00 45.662 Self wieght of abutment&footings 483.53KN 0.00 31.583 Reaction due to live load with impact factor 466.66KN 0.000 30.484 Impact load 0.00KN 0.00 0

Horizontal loads:- (Stress = M/Z)5 Wind load 16.50KN 4.93 -5.16 Water current force 0.62KN 3.77 -0.15

102.47

S.No Type of load


Horizontal loads:- (Stress = M/Z)5 Wind load 16.50KN 4.93 5.16 Water current force 0.62KN 3.77 0.15

112.97

Stress at up stream side P/A(1+6e/b)+M/Z = 102.47 KN/Sqm>-2800KN/sqm.edge =

Hence safe.

Stress at down stream side P/A(1+6e/b)+M/Z = 112.97 KN/Sqm<5000KN/sqmedge =

Hence safe.

i)On top of 2nd footing




S.No Type of load


2 Self wieght of abutment&cut waters 386.51KN 0.210 0.000

3 Reaction due to live load with impact factor 466.66KN -0.740 0.000

4 Impact load 0.00 0.000 0.00

Intensity in KN (P)


Stress at upstream edgeP/A(1+6e/b)

Intensity in KN (P)


Stress at D/S edgeP/A(1+6e/b)

Vertical load acting on the abutment (P) composes of the following components

Intensity in KN








About x-axis:-

Breadth of 1st footing b = 6.25mDepth of 1st footing d = 2.30mArea of the footing = A = 14.375

Section modulus of base of abutment 5.51

about x-axis--Zx =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load

Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN -0.74 14.092 Self wieght of abutment&footings 386.51KN 0.21 29.243 Reaction due to live load with impact factor 466.66KN -0.74 9.44 Impact load 0.00KN 0.00 0


6.62




206.3

Horizontal load acting/transferred on the abutment (H) composes of the following components

Intensity in KN


m2

(1/6)bd2 = m3



Intensity in KN (P)



Intensity in KN (P)



Hence safe.


Hence safe.

About y-axis:-



about y-axis--Zy =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load



102.75

S.No Type of load



113.23

Stress at up stream side edge of abutment = P/A(1+6e/b)+M/Z = 102.75 KN/Sqm>-2800KN/sqm.

m2

(1/6)bd2 = m3


For M20 grade of concrete permissible tensile stress in bending tension is -2N/mm2

Intensity in KN (P)



Intensity in KN (P)



Hence safe.Stress at down stream side edge of abutment = P/A(1+6e/b)+M/Z = 113.23 KN/Sqm<5000KN/sqm

Hence safe.

i)On top of 1st footing


a)x-Direction-----At right angle to the movement of vehiclesb)y-Direction-----In the direction of movement of vehicles

S.No Type of load

1 Reaction due to dead load from super structure 699.20KN -0.815 0.002 Self wieght of abutment&footings 295.43KN 0.270 0.0003 Reaction due to live load with impact factor 466.66KN -0.815 0.000

4 Impact load 0.00 0.000 0.00


1 Wind load 16.50KN x-Direction 4.332 Tractive,Braking&Frictional resistance of bearings 58.69KN y-Direction 4.033 Water current force 0.62KN x-Direction 3.17


About x-axis:-

Breadth of abutment b = 6.25mDepth of abutment d = 2.00mArea of the footing = A = 12.5


about x-axis--Zx =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load

Vertical loads:-(Stress = P/A(1+6e/b)


Intensity in KN




Intensity in KN


m2

(1/6)bd2 = m3



Intensity in KN (P)



1 Reaction due to dead load from super structure 699.20KN -0.82 12.172 Self wieght of abutment&footings 295.43KN 0.27 26.73 Reaction due to live load with impact factor 466.66KN -0.82 8.124 Impact load 0.00KN 0.00 0


-9.77




240.51

Stress at heel = P/A(1+6e/b)+M/Z = -9.77 KN/Sqm>-2800KN/sqm.

Hence safe.


Hence safe.

About y-axis:-

Breadth of abutment b = 2.00mDepth of abutment d = 6.25mArea of the footing = A = 12.5


about y-axis--Zy =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load

Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN 0.00 55.942 Self wieght of abutment&footings 295.43KN 0.00 23.633 Reaction due to live load with impact factor 466.66KN 0.000 37.33

Intensity in KN (P)


m2

(1/6)bd2 = m3



Intensity in KN (P)



4 Impact load 0.00KN 0.00 0Horizontal loads:- (Stress = M/Z)

5 Wind load 16.50KN 4.33 -5.496 Water current force 0.62KN 3.17 -0.15

111.26

S.No Type of load



122.54



Hence safe.

b)Load Envelope-II:-(The Canal is full,back fill intact with no live load on span)

i)On top of RCC Raft footing




S.No Type of load


Self wieght of abutment&cut waters 483.53KN

Reduction in self weight due to buoyancy -201.47KN

2 Net self weight 282.06KN 0.105 0.000

3 Vertical component of earth pressure 203.63KN 0.430 0.000

Intensity in KN (P)




Intensity in KN








4 Horizontal load due to earth pressure 152.54KN y-Direction 1.32

5 Water pressure force 247.50KN y-Direction 1.00


About x-axis:-

Breadth of bottom footing b = 6.25mDepth of bottom footing d = 2.45mArea of the footing = A = 15.3125


about x-axis --Zx =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load

Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN -0.74 13.222 Net self wieght of abutment&footings 282.06KN 0.10 20.283 Vertical component of Earth pressure 203.63KN 0.43 18.79

Horizontal loads:- (Stress = M/Z)4 Horizontal load due to earth pressure 152.54KN 1.32 -32.175 Water pressure force 247.50KN 1.00 39.6

59.7


Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN 0.74 78.12 Net self wieght of abutment&footings 282.06KN -0.10 16.563 Vertical component of Earth pressure 203.63KN -0.43 7.81

Horizontal loads:- (Stress = M/Z)4 Horizontal load due to earth pressure 152.54KN 1.32 32.175 Water pressure force 247.50KN 1.00 -39.6

95.06


Intensity in KN


m2

(1/6)bd2 = m3



Intensity in KN (P)



Intensity in KN (P)


Hence safe.


Hence safe.

About y-axis:-

Breadth of bottom footing b = 2.45mDepth of bottom footing d = 6.25mArea of the footing = A = 15.3125


about y-axis --Zy =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load

Vertical loads:-(Stress = P/A(1+6e/b)1 Reaction due to dead load from super structure 699.20KN 0.00 45.662 Net self wieght of abutment&footings 282.06KN 0.00 18.423 Vertical component of Earth pressure 203.63KN 0.00 13.3


72.13



Horizontal loads:- (Stress = M/Z)4 Horizontal load due to earth pressure 16.50KN 4.93 5.15 Water pressure force 0.62KN 3.77 0.2

82.63



Hence safe.

m2

(1/6)bd2 = m3



Intensity in KN (P)


Stress at U/S EdgeP/A(1+6e/b)

Intensity in KN (P)


ii)On top of 2nd footing




S.No Type of load


Self wieght of abutment&footings 483.53KN











About x-axis:-

Breadth of 2nd footing b = 6.25mDepth of 2nd footing d = 2.30mArea of the footing = A = 14.375


about x-axis --Zx =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load


Intensity in KN




Intensity in KN


m2

(1/6)bd2 = m3



Intensity in KN (P)





58.95




105.9


Hence safe.


Hence safe.

About y-axis:-



about y-axis --Zy =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load


Horizontal loads:- (Stress = M/Z)4 Wind load 16.50KN 4.63 -5.1

Intensity in KN (P)


m2

(1/6)bd2 = m3



Intensity in KN (P)



5 Water current force 0.62KN 3.47 -0.177.19




87.67



Hence safe.

iii)On top of 1st footing




S.No Type of load


Self wieght of abutment&cut waters 386.51KN








Intensity in KN (P)



Intensity in KN




Intensity in KN





About x-axis:-



about x-axis --Zx =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load



51.03




105.95


Hence safe.


Hence safe.

About y-axis:-

m2

(1/6)bd2 = m3



Intensity in KN (P)



Intensity in KN (P)




about y-axis --Zy =

i.e, 5000KN/sqm

i.e, -2800KN/sqm

S.No Type of load



73.59




83.39



Hence safe.

V)Check for stability of abutments:-

a)Load Envelope-III:-(The Canal is dry,back fill intact with live load on span)



m2

(1/6)bd2 = m3



Intensity in KN (P)



Intensity in KN (P)



S.No Type of load

1 Reaction due to dead load from super structure 699.20KN 0.82 0.00

2 Self wieght of abutments 295.42KN 0.270 0.000

3 Reaction due to live load with impact factor 466.66KN 0.82 0.000

4 Vertical component of Active Earth pressure 203.63KN 0.430 0.00

1664.91KN




3 Horizontal Active Earth pressure force 152.54KN y-Direction 0.72

227.73KN

Check for stability against over turning:-

Taking moments of all the overturning forces about toe of the abutment wrt x-axis,

Moment due to tractive,braking&frictional resistance of bearings = 254.11Kn-m

Moment due to active earth pressure force = 109.60Kn-m

Total overturning moment = 363.70Kn-m

Taking moments of all the restoring forces about toe of the abutment wrt x-axis,,

Moment due to self weight of abutment = 375.18Kn-m

Moment due to live load reaction on abutment = 846.99Kn-m

Moment due to super structure load reaction on abutment = 1269.04Kn-m

Moment due to vertical component of active earth pressure = 291.19Kn-m

Total Restoring moment = 2782.40Kn-m

Factor of safety = 7.65017071 > 2.0 Hence safe


Intensity in KN




Intensity in KN


(As per clause 706.3.4 of IRC:78-2000)

Check for stability against sliding:-

1664.91KN

227.73KN

Coefficient of friction between concrete surfaces = 0.80

5.84879451 > 1.5 Hence safe


b)Load Envelope-IV:-(The Canal is running upto HFL with no live load on span)




S.No Type of load

1 Reaction due to dead load from super structure 699.20KN 0.82 0.00

Self wieght of abutments 295.42KN

-123.10KN

2 Net self wieght 172.32KN 0.270 0.000

3 Vertical component of Active Earth pressure 203.63 0.430 0.00




3 Active Earth pressure force 152.54KN y-Direction 0.72

4 Force due to water pressure 247.50KN y-Direction 0.40

Check for stability against over turning:-

Taking moments of all the overturning forces about toe of the abutment wrt x-axis,

Moment due to tractive,braking&frictional resistance of bearings = 0.00Kn-m

Moment due to active earth pressure force = 109.60Kn-m

Total vertical load acting on the base of the abutment Vb =

Total sliding force,ie,horizontal load on the abutment Hb =

Factor of safety against sliding Fs =


Intensity in KN



Reduction in self weight due to buoyancy


Intensity in KN


Total overturning moment = 109.60Kn-m

Taking moments of all the restoring forces about toe of the abutment wrt x-axis,

Moment due to self weight of abutment = 218.85Kn-m

Moment due to water pressure force on the abutment = 99.00Kn-m

Moment due to super structure load reaction on abutment = 1269.04Kn-m

Moment due to vertical component of active earth pressure = 291.19Kn-m

Total Restoring moment = 1878.08Kn-m

Factor of safety = 17.1362919 > 2.0 Hence safe(As per clause 706.3.4 of IRC:78-2000)

Check for stability against sliding:-

623.45KN

152.54KN

Coefficient of friction between concrete surfaces = 0.80

3.26968769 > 1.5 Hence safe


Total vertical load acting on the base of the abutment Vb =

Total sliding force,ie,horizontal load on the abutment Hb =

Factor of safety against sliding Fs =

DESIGN OF RAFT FOR THE SLAB CULVERT

Name of the work:-Slab culvert on 6/0 Km of Vemuladeevi Channel

Abutment

Abutment

Length of the Raft:- = 14.60m

Width of the Raft:- = 6.85m

Total load on the Raft:-

Dead Load:-

Wt.of Deck slab = 1166.63Kn

Wt.of wearing coat = 110.76Kn

Wt.of bed blocks over abutments = 121.00Kn

Wt.of abutments

Footing-I = 182.16KnFooting-II = 194.04KnWt.of abutments = 590.84Kn

Total 2365.43Kn

Dead load stress = 23.65Kn/Sqm

Live Load:-

Taking IRC Class-A loading

Wheel width in the direction of movement =0.2+0.2+0.25/2 = 0.625m

11.4 11.4 6.8 6.8

1.2 4.3 3.0 5.475

0.625

14.60m

Centre of gravity of loading from 1st 11.4t load =

= 2.99m

Centre of gravity from the end of raft = 3.615m


Stress due to live load = 1xP(1+6e/b)(Taking single lanes) A

Max.stress = 15.08Kn/Sqm

Min.stress = -7.95Kn/Sqm

Total stress due to dead load and live load

Max.Stress = 38.73Kn/Sqm

Min.Stress = 15.70Kn/Sqm

Assuming the depth of raft as 70cm

Stress due to self weight of raft = 17.50Kn/Sqm

Stress due to wieght of base concrete = 3.60Kn/Sqm

Hence,the Max.stress on the soil = 59.83Kn/Sqm

Which is less than 6t/sqm(Soil testing report)

Hence safe.

Net Max.upward pressure acting on Raft = 38.73Kn/Sqm

Net Min.upward pressure acting on Raft = 15.70Kn/Sqm

The design stress = 27.21Kn/Sqm

Hence,the UDL on the raft = 27.21Kn/m

Design of Raft:-

The raft will be analysed as a continuous beam of 1m width with the loadingas shown below:-

1.375 11.85 1.375

UDL of 27.21Kn/m

After analysis the bending moment diagram is as given below:

678

38.6

Max.Negative bending moment Mu = 678.00KNm

Max.Positive bending moment Mu = 38.60KNm

Effective depth required d = 443.31mm

Over all depth provided = 700.00mm

Effective depth provided(Assuming 40mm cover) d = 637.50mm

Top steel:-

1.668

From table 3 of SP 16,percentage of steel required = 0.505

Area of steel required = 3219.38sqmm

Bottom steel:-

0.095

From table 3 of SP 16,percentage of steel required/Minimum steel = 0.12

Area of steel required = 765.00sqmm

Hence provide 12mm dia HYSD bars@ 125mm c/c spacing at bottom and provide 25mm bars at 150mm c/c at top

3270.83sqmm

904.32sqmm

Provide distribution reinforcement of 0.12% both at top and bottom

Area = 840.00sqmm

Mu/0.138fckb =

Mu/bd2 =

Mu/bd2 =

Hence Ast provided at top =

Hence Ast provided at bottom =

Adopting 12mm dia bars,the spacing required is = 134.57mm

Hence provide 12mm dia bars @ 125mm c/c spacing at top& bottom as distribution steel

DESIGN OF RAFT FOR THE SLAB CULVERT

Hydraulic design

Hydraulic Particulars:-

1.Full supply Level 1.488

2.Ordinary Flood level

3.Lowest Bed level 0.488

4.Average bed slope 0.000059(1 in 17000)

0.025(As per table 5 of IRC:SP 13)

6.Vertical clearence proposed 0.509(As per clause 15.5 of IRC:SP 13&as per profile)

6.Bottom of deck proposed 1.997(MFL+Vertical clearence)

7.Road Crest level 2.862(Bottom of deck level+thickness of deck slab)

8.Width of carriage way 5.500

Discharge Calculations:-

1)From the data furnished by the Irrigation Department:-

Design discharge = 3.300Cumecs

2)Area Velocity method:-

Depth of flow w.r.t HFL = 1.000m

Bed width = 8.30m

Assuming side slopes 1:1.5 in clayey soils,top width at HFL = 9.800m

Wetted Area = 9.05sqm

Wetted perimetre = 11.13m

Hydraulic Radius R= Total area/Wetted perimeter = 0.81

Velocity V = 0.27m/sec

Discharge Q = AXV 2.44Cumecs

Design Discharge = 3.300Cumecs

Design Velocity = 0.337m/sec

5.Rugosity Coefficient(n)

1/nX(R2/3XS1/2)

Ventway Calculations(H.F.L Condition):-

Assuming the stream to be truly alluvial,the regime width is equal to linear waterway required for the drain.

8.72m

The actual top width is almost equal to the above regime width.Hence,the stream is almost truly alluvial in nature.As per IRC:SP--13,the ventway calculations for alluvial streams are as given below:-

Assuming afflux = x = 0.15m9.80m

Clear span = 10.00mEffective linear water way = 10.00m

Depth of flow = 1.00m

Head due to velocity of approach = 0.004m

Combined head due to Velocity of approach and 0.154mafflux

1.56m/sec

Linear water way required 2.11m

No.of vents required = = 0.211Say---1 Vent

In alluvial streams,the actual width of the stream should not be reduced,as it results in enhanced scour depth and expensive training works.

Hence No.of vents required as per the width of the stream at H.F.L= 0.98

No.of vents to be provided 1Nos

No.of piers = 0Nos

Scour Depth Calculations:-

As per the clause 101.1.2 of IRC:5--1985,the design discharge should be increased by 30% to ensure adequate margin of safety for foundations and protection works

Hence,the discharge for design of foundations = 1.30XDesign Discharge =

Discharge per metre width of foundations = q =

Hence,as per Lacey's silt theory,the regime width W = 4.8Q1/2 = 4.8*3.30.5 =

Width of channel at H.F.L(b+h) =

di =

(Vmax2/2g)X[di/(di+x)]2

hi =

Velocity through vents Vv = 0.90X(2ghi)1/2 =

LWW = Qd/(VvXdi) =

LWW /LC

Lacey's Silt factor ' f ' = 1.76Xm1/2(For normal silt) =

Normal scour depth D = 1.34(q2/f)1/3 =

Bottom level of foundation =

Depth of foundation below low bed level =

The Minimum Safe Bearing capacity of the soil is considered as 60 KN/m2 at a depth of 2.00m below LBL

Hence open foundation in the form of raft is proposed at a depth of 2.0m below LBL,ie,at a level of

Cut-off walls and aprons are not required from scour depth point of view

Maximum scour depth Dm = 1.5XD =

Depth of foundation = Dm + Max.of 1.2m or 1/3 Dm =

Hydraulic design

The actual top width is almost equal to the above regime width.Hence,the stream is almost truly alluvial in nature.

In alluvial streams,the actual width of the stream should not be reduced,as it results in enhanced scour

As per the clause 101.1.2 of IRC:5--1985,the design discharge should be increased by 30% to ensure adequate

4.39Cumecs

1.00

0.439

0.78m

1.17m

2.37m

-0.88m

1.370m

-1.512m

design of 10m clear span slab bridge

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