Design of syphon aqueduct

DESIGN OF TWO VENT BOX BARREL FOR SYPHON AQUEDUCT Name of the work:-Elamanchili minor drain under Medpadu field channel @ 0/750 Km

F TWO VENT BOX BARREL FOR SYPHON AQUEDUCT

the work:-Elamanchili minor drain under Medpadu field channel @ 0/750 Km

Note on site conditions As per the record the hydraulic particulars of Chilla minor drain&Field channel at proposed site are as given below:-

Hydraulic Particulars Units

Chilla Minor drain

Field channel

Chainage

Km

0.500

----

Discharge

Cumecs

2.950

0.600

Bed level

m

1.200

2.585

OFL

m

2.210

2.910

MFL

m

3.130

3.210

TBL

m

4.130

3.510

RTL

m

4.130

4.130

Bed width

m

1.400

0.600

Top width

m

7.260

0.600

0.000250

0.000250

Bed fall

----

From the above hydraulic particulars,it can be observed that the MFL of Chilla minor drain is above the bed level of field channel.It is proposed to construct Syphon Aqeduct with depressed floor and 1V-RCC barrel of size 2.50mx1.50m for a length of 6m to accommodate the existing village road after the field channel. Further fluming of field channel is not proposed, hence existing width of the channel is not altered. The floor of the aqeduct is proposed to be lowered to a level of +0.485 with vertical drop on upstream side and raising of floor on down stream side in 1V to 5H to ensure clearing of sediments. Wing walls are proposed both upstream&down stream sides of drain along with revetment for slopes and bed protection.Cisterns are also proposed both U/S and D/S as per the requirement.Cut-off walls are proposed both U/S and D/S sides of drain. Similarly,wing walls along with bed and slope protections are proposed for field channel also both U/S and D/S sides. The hydraulic design of syphon aqueduct is carried out as per the guide lines stipulated in IS 7784:Part1--1993.The structural design of the box barrel along with load combinations is carried out as per the guide lines stipulated in IS 7784:Part2--5--1993. In view of the above facts,the box barrel is designed as free flowing vented structure with all possible combinations of loads.Further,the stability of the stucture is also ensured by providing appropriate factors of safety against overturning and sliding.

As,it is not possible propose foundation of box culvert below Max.scour depth,protective works are proposed for the bed of the minor drain as per the guidelines.

3.425

of Chilla minor drain is above

of the channel is not altered.

ertical drop on upstream side

along with revetment for

er the requirement.Cut-off

d for field channel also

ombinations is carried out as

ented structure with all

-2.1 1.325 2.065 -1.325

Design of 1V Box Barrel I)Design Parameters:Over all width of the barrel (WL) Clear vent (b) Clear depth (d) Thickness of top slab (t1) Thickness of side wall (t2) Thickness of raft (t3) Outer span (B) Outer Depth (D) Haunch width Haunch depth Thickness of wearing coat (t4)

= = = = = = = = = = =

6.00m 2.50m 1.50m 0.30m 0.30m 0.30m 3.10m 2.10m 0.15 0.15 0.075m

Height of railing (h2)

=

1.200m

Unit weight of RCC (yrc)

=

25KN/cum

Unit weight of PCC (ypc)

=

24KN/cum

Density of back fill soil behind side walls of Box (y)

=

18KN/Cum

Unit weight of water (yw)

=

10KN/Cum

Angle of shearing resistance of back fill material(Q)

=

30

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

=

90

Slope of back fill (b)

=

0

Angle of wall friction (q)

=

15

Height of surcharge considered (h3)

=

1.20m

Barrel top level (BTL)

=

2.585m

Drain bed level (DBL)

=

1.200m

Drain High flood Level (HFL) Depressed floor level of barrel

= =

3.130m 0.785m

Barrel foundation level (BFL) Channel bed level(CBL) Channel top level(CTL) Road top level (RTL)

= = = =

0.485m 2.585m 3.510m 4.130m

Upstream side breast wall top level

=

4.130m

Downstream side breast wall top level

=

4.580m

Middle breast wall top level

=

4.130m

Thickness of brest walls

=

0.300m

Barrel length in Road portion

=

4.500m

Barrel length in Channel portion

=

0.600m

Safe Bearing Capacity of the soil (SBC)

=

7.50t/sqm

Compressive strength of concrete for Box (fck)

=

20.00N/sqmm

Yield strength of steel (fy) Cover to reinforcement

=

415.00N/sqmm

=

50.00mm

Details of the preliminary structure assumed is as given below :-

300

450

PLAN

1545

300

ROAD PORTION

2500 2100

1500

4500

300

CANAL PORTION

SECTION

300 6000 600

II)General loading pattern:-

As per IRC:6---2000,the following loadings are to be considered on the box barrel in road portion:1.Dead load 2.Live load 3.Impact load 4.Wind load 5.Water current 6.Tractive,braking effort of vehicles&frictional resistance of bearings 7.Buoyancy 8.Earth pressure 9.Seismic force 10.Water pressure force 11.Static water pressure due to water in canal As per clause 202.3,the increase in permissible stresses is not permissible for the above loading combination.

Further as per IS 7784-Part 1---1993,the structure should be designed for the following forces :12.Uplift pressure due to flowing water 13.Uplift pressure due to subsurface flow

III)Loading on the box culvert :1.Dead Load:-

300

3100

i)Self wieght of the top slab =

139.50KN

(3.1*6*0.3*25) = ii)Self wieght of the bottom slab/Raft =

139.50KN

(3.1*6*0.3*25) = iii)Self wieght of side walls =

135.00KN

(2*1.5*6*0.3*25) = iv)Self weight of haunches =

6.75KN

(4*0.5*0.15*0.15*6*25) = v)Self weight of wearing coat =

34.88KN

(3.1*6*0.075*25) = vi)Self weight of U/S side brest wall =

35.92KN

(1*3.1*0.3*1.545*25) = vii)Self weight of D/S side brest wall =

46.38KN

(1*3.1*0.3*1.995*25) = viii)Self weight of middle brest wall =

35.92KN

(1*3.1*0.3*1.545*25) = ix)Weight of earth on barrel in Road portion =

387.95KN

(18*3.1*4.5*1.545) = 961.80KN There is no need to consider snow load as per the climatic conditions Taking moments of all loads about upstream end,we get S.No

Item

Weight

Distance of centroid from U/S end

Moment about upstream end in KN-m

1

Top slab

139.50KN

3.00

418.50

2

Bottom slab

139.50KN

3.00

418.50

3

Side walls

135.00KN

3.00

405.00

4

Haunches

6.75KN

3.00

20.25

5

Wearing coat

34.88KN

3.00

104.64

6

U/S brest wall

35.92KN

0.15

5.39

7

D/S brest wall

46.38KN

5.85

271.32

8

Mid. brest wall

35.92KN

0.75

26.94

9

Earth fill

387.95KN

3.15

1222.04

961.80KN

2892.58

Distance of centroid of above dead load from U/S end =

3.007m

Eccentricity in x- direction =

0.007m

The position of resultant dead load is as shown below:-

6000

X

7 3100

Y 2.Live Load:As per clause 201.1 of IRC:6--2000,the bridges and culverts of medium importance are to be designed for IRC Class A loading. GENERAL IRC Class-A loading Pattern

Position of Live load for Max.Soil pressure 3100

Portion to be loaded with

6.8t

X

The IRC Class A loading as per the drawing is severe for bearing stresses on soil and the same is to be considered as per clauses 207.1.3&207.4

6.8t

3.00

3.00

6.8t

11.4t

3.00

6.8t

4.30

1.20

11.4t

3.20

2.7t

1.80

2.7t

1.10

X

Position of Live load for Max.Soil pressure 3100

Portion to be loaded with live load of 5KN/sqm

1750

4500 1525

11.4t

11.4t

1200 1800

2750

Y

u 0.45

b 375

The ground contact area of wheels for the above placement,each axle wise is given below:Axle load (Tonnes) 11.4 6.8 2.7

Ground Contact Area B(mm)

250 200 150

W(mm)

500 380 200

Assuming 0.3m allowance for guide posts 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 0.45m

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

0.45m

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

1.75m 2.20m

The total live load on the top slab composes the following components:1.Wheel loads----Point loads (114+114)=

3.Live load in remaing portion(Left side)----UDL (0.45*3.1*5)= 4.Live load in remaing portion(Right side)----UDL (1.75*3.1*5)=

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

Wheel Load/UDL in KN

1

57

2

57

3

Distance from Y-axis

(0.3+0.45 +0.5/2)= (0.3+0.45 +0.5/2)

1.00m

57

(0.3+0.45 +0.5/2+1.8)

2.80m

4

57

2.80m

5

6.975

(0.3+0.45 +0.5/2+1.8) (0.3+0.45/2)=

6

27.125

1.00m

(0.3+0.45/2 +1.75) =

0.525m 2.28m

262.100 Distance of centroid of forces from y-axis (498.57/262.1) = = 1.902m Eccentricity = (1.902-6/2)=

1.098m

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

1

57

(3.1-0.38)

2.72m

2

57

(3.1-0.38)

2.72m

3

57

[3.1(0.38+1.2)] =

1.52m

4

57

[3.1(0.38+1.2)] =

1.52m

7

6.98KN

(3.1/2)=

1.55m

8

27.13KN

(3.1/2)=

1.55m

262.1 Distance of centroid of forces from x-axis (536.22/262.1) = = 2.046m Eccentricity = (2.046-3.1/2)=

0.496m

Location of the resultant of live load is as shown in the figure given below:6000

X

3100 496 1098

Y The eccentricty of the line of action of live load wrt centroid in y-direction =

0.496m

The eccentricty of the line of action of live load wrt centroid in x-direction =

1.098m

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 [4.5/(6+3.1)]=

0.495

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 box culvert will be (0.495/2)=

For the remaining portion,impact need not be considered.

4.Wind load:The deck system is located at height of (RTL-LBL) [4.58-(1.20)]=

3.38m

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 height is (52+1.38*(63-52)/2)= 59.59 Kg/m2. Height of the deck system =

3.380

Breadth of the deck system =(3.1) =

3.10

The effective area exposed to wind force =HeightxBreadth = Hence,the wind force acting at centroid of the deck system = (Taking 50% perforations) (0.5*59.59*10.478*10/1000)= 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 = (300*6.0*10/1000)= The location of the wind force from the top of Raft slab of box culvert = (1.5+0.3+1.5+0.075) =

5.Water current force:Water pressure considered on square ended abutments as per clause 213.2 of IRC:6---2000 is 2

P = 52KV = 2 (52*1.5*0.69 )=

37.14 Kg/m2.

(where the value of 'K' is 1.5 for square endedside walls) For the purpose of calculation of exposed area to water current force,only 1.0m width of box is considered for full hieght upto HFL Hence,the water current force = [37.14*1.0*(2.585-(1.20)*10/1000] =

0.51KN

Point of action of water current force from the top of RCC raft slab = [3.13-(1.20)]/3 =

10.478

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 (262.1*0.1)=

26.21KN

The location of the tractive force from the top of RCC raft slab = (1.2+0.075+0.3+1.50) = 7.Buoyancy :As per clause 216.4 of IRC:6---2000,for abutments or piers of shallow depth,the dead weight of the box culvert 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 box is scoured. For the preliminary section assumed,the volume of box section is i)Volume of Raft slab section =

5.580Cum

(186.0/25) = ii)Volume of side walls upto MFL =

5.400Cum

(180/25) = iii)Volume of haunches =

0.140Cum

(9/25) = 11.120Cum Reduction in self wieght = (11.12*10)=

111.20KN

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 box as per the Coulomb's theory is given by

'2 Ka = sina

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

sin(a-q)

sin(a+b)

Sin(a+Q) = Sin(a-q) = Sina = Sin(Q+q) = Sin(Q-b) = Sin(a+b) =

SIN[3.14*(90+30)/180] = SIN[3.14*(90-15)/180] = SIN[3.14*(90)/180] = SIN[3.14*(30+15)/180] = SIN[3.14*(30-0)/180] = SIN[3.14*(90+0)/180] =

0.867 0.966 1 0.707 0.5 1

From the above expression, Ka =

0.3

The hieght of box above GL,as per the preliminary section assumed = Hence,maximum pressure at the base of the wall (0.3*1800*1.80)*10/1000 =

Pa =

The pressure distribution along the height of the wall is as given below:Surcharge load = (0.3*1800*1.2)*10/1000=

6.48 KN/sqm

6.48

1.800

9.72

6.48

Area of the rectangular portion = Area of the triangular portion =

6.48*1.80 = 0.5*9.72*1.8 =

11.66 8.75 20.41

Taking moments of the areas about the toe of the wall S.No 1 2

Description

Area

Rectangular Triangular

11.66 8.75

Lever arm Moment 0.9 0.6

20.41 Height from the bottom of the wall = (15.744/20.41)

10.494 5.25 15.744

0.77m

The active Earth pressure acts on the box culvert is as shown below:-

Earth Pressure on Box culvert 3100

Pv

P 15°

1500

Ph 770

Inclination of earth pressure force with horizontal

15.00 Deg.

Total earth pressure acting on the wall P = (6.48*1.8+0.5*9.72*1.8)*8 =

122.47KN

Horizontal component of the earth pressure Ph = (PCos150 ) Vertical component of the earth pressure Pv = (PSin150 ) Eccentricity of vertical component of earth pressure = (3.1/2-0.0) = 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 sidewall is as given below:-

HFL 3.130m

1.93

LBL 1.200m

19.30kn/sqm

Total horizontal water pressure force = 0.5*19.3*1.93*8 = The above pressure acts at height of H/3 =1.93/3 = Static water pressure force (Vertical) = (1.93+0.16)*10 =

111.75KN 0.64m 20.90kn/sqm

11.Static water pressure due to water in canal Height of water in channel above bed level = The static water pressure on top slab of box barrel = Total load due to static water pressure = Eccentricity of the above load in x-direction =

0.725m 7.25kn/sqm 13.49KN 2.40m

12.Uplift pressure due to flowing water:Level of bottom of the top slab of box barrel = MFL of the drain =

+2.29m +3.130m

Afflux =

0.160m

Datum head =Height of water above the bottom of top slab of box barrel =

1.005m

Kinetic head = v2/2g =

0.040m

Total head causing uplift on the top slab of box barrel =

1.045m

Hence uplift pressure on the top slab = Total uplift force =

10.45kn/sqm 156.75KN

13.Uplift pressure due to subsurface flow Afflux =

0.160m

The difference between subsoil hydraulic gradient line h' = and the bottom of floor just at entry section when the water is held up.

2.090

Hence,the theoritical max.uplift pressure = yw x h' =

20.90kn/sqm

Uplift force due to sub surface water =

194.37KN

IV)Check for stability of Box Barrel:a)Load Envelope-I:-(The drain is dry,back fill intact with live load on span) 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 Vertical load acting on the Box barrel (P) composes of the following components S.No

Type of load

1

Self wieght of Box culvert

2

Live load with impact factor---(Wheel loads+UDL) [262.1*(1+0.495)] = Vertical component of Active Earth pressure

3

Intensity in KN

Eccentricty about xaxis(m)

961.80KN

0.000

391.84KN

-0.496

31.68KN

1.550

1385.32KN

Horizontal load acting/transferred on the box (H) composes of the following components S.No

Type of load

Intensity in KN

Direction x or y

1

Wind load

18.00KN

x-Direction

2

Tractive,Braking&Frictional resistance of bearings

26.21KN

y-Direction

3

Horizontal Active Earth pressure force

118.30KN

y-Direction

162.51KN Check for stability against over turning(Assuming that the earth fill on toe side is scoured):Taking moments of all the overturning forces about toe of the box wrt x-axis, Moment due to tractive,braking&frictional resistance of bearings = (26.21*3.38)=

Moment due to active earth pressure force = (118.3*0.77)= Total overturning moment = Taking moments of all the restoring forces about toe of the box wrt x-axis,, Moment due to self weight of box = [961.8*(3.1/2+0.0)]= Moment due to live load reaction on box = [391.84*(3.1/2-0.496)]= Moment due to vertical component of active earth pressure = [31.68*(3.1/2+1.55)]= Total Restoring moment =

Factor of safety = (2002/171.98)=

11.6407156

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

Check for stability against sliding:Total vertical load acting on the base of the box culvert Vb = Total sliding force,ie,horizontal load on the box Hb = Coefficient of friction between concrete surfaces = Factor of safety against sliding Fs = (0.8*1385.32/162.51)=

6.81957361 > 1.5 Hence safe (As per clause 706.3.4 of IRC:78-2000)

b)Load Envelope-II:-(The Canal is running upto HFL with no live load on span) 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 Vertical load acting on the box (P) composes of the following components S.No

1

Type of load

Intensity in KN

Eccentricty about xaxis(m)

Self wieght of box

961.80KN

Reduction in self weight due to buoyancy

-111.20KN

2

Net self wieght

850.60KN

0.000

3

Uplift force due to flowing water

-156.75KN

0.000

4

Uplift force due to subsurface water

-194.37KN

0.000

5

Static water force due to water in drain

388.74KN

0.000

6

Static water force due to water in channel

13.49KN

0.000

7

Vertical component of Active Earth pressure

31.68

1.550

Horizontal load acting/transferred on the box (H) composes of the following components S.No

Type of load

Intensity in KN

Direction x or y

1

Wind load

18.00KN

x-Direction

2

Tractive,Braking&Frictional resistance of bearings

0.00KN

y-Direction

3

Active Earth pressure force

118.30KN

y-Direction

4

Force due to water pressure

111.75KN

y-Direction

Check for stability against over turning:Taking moments of all the overturning forces about toe of the box wrt x-axis, Moment due to tractive,braking&frictional resistance of bearings = Moment due to active earth pressure force = (118.3*0.77)= Total overturning moment = Taking moments of all the restoring forces about toe of the box wrt x-axis, Moment due to self weight of box = [850.6*(3.1/2+0.0)]=

Force due to static water pressure need not be considered,as it acts on both side walls in opposite directions

Moment due to vertical component of active earth pressure = [31.68*(3.1/2+1.55)]= Total Restoring moment =

Factor of safety =

15.5238491

Check for stability against sliding:Total vertical load acting on the base of the boxVb = (850.6+31.68) =

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

Total sliding force,ie,horizontal load on the box Hb = Coefficient of friction between concrete surfaces = Factor of safety against sliding Fs = (0.8*882.28/118.3)=

5.96634219 > 1.5 Hence safe (As per clause 706.3.4 of IRC:78-2000)

V)Check for bearing pressure:a)Load Envelope-I:-(The Canal is dry, back fill intact with live load on span) i)At the bottom of RCC raft slab

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 Vertical load acting on the Box (P) composes of the following components S.No

Type of load

Intensity in KN

Eccentricty about xaxis(m)

1

Self weight of box

961.80KN

0.000

2

Self weight of levelling concrete =(3.7*6*0.30*24)

159.84KN

0.00

3

Live load with impact factor---(Wheel loads+UDL) [262.1*(1+0.495)] =

4

Vertical component of earth pressure

391.84KN 31.68KN

-0.496 1.550

Horizontal load acting/transferred on the abutment (H) composes of the following components S.No

Type of load

Intensity in KN

Direction x or y

1

Wind load

18.00KN

x-Direction

2

Tractive,Braking&Frictional resistance of bearings

26.21KN

y-Direction

3

Horizontal load due to earth pressure Safe bearing capacity SBC of the soil =

Check for stresses:About x-axis:-

118.30KN 7.50t/sqm

y-Direction

Breadth of footing b =

6.00m

Depth of footing d =

3.10m 18.6 m2

Area of the footing = A = Section modulus of bottom footing about x-axis --Zx =

(1/6)bd2 =

9.61 m3

For RCC Strip footing permissible bearing pressure is 1.5xSBC =

113KN/sqm

No tension is allowed on soil as per clause 706.3.3.1 of IRC 78:2000 S.No

1 2 3 4 1 2 3

Type of load

Vertical loads:-(Stress = P/A(1+6e/b) Self wieght of Box Self weight of levelling concrete Live load with impact factor---(Wheel loads+UDL) [262.1*(1+0.495)] = Vertical component of Earth pressure Horizontal loads:- (Stress = M/Z) Wind load Tractive,Braking&Frictional resistance of bearings Horizontal load due to earth pressure

S.No

1 2 3 4 1 2 3

Intensity in KN (P)

Type of load

Stress at heel =

961.80KN 159.84KN 391.84KN

0.00 0.00 -0.496

31.68KN

1.55

18.00KN 26.21KN 118.30KN

0.00 3.08 1.07

Intensity in KN (P)

Vertical loads:-(Stress = P/A(1+6e/b) Self wieght of Box Self weight of levelling concrete Live load with impact factor---(Wheel loads+UDL) [262.1*(1+0.495)] = Vertical component of Earth pressure Horizontal loads:- (Stress = M/Z) Wind load Tractive,Braking&Frictional resistance of bearings Horizontal load due to earth pressure

P/A(1+6e/b)+M/Z =

Eccentricity/Lever arm

Eccentricity

961.80KN 159.84KN 391.84KN

0.00 0.00 0.496

31.68KN

-1.55

18.00KN 26.21KN 118.30KN

0.00 3.08 1.07

53.67 KN/Sqm>0

Hence safe. Stress at toe =

P/A(1+6e/b)+M/Z =

Hence safe.

About y-axis:-

112.47 KN/Sqm>113KN/sqm

Breadth of footing b = Depth of footing d = Area of the footing = A =

3.10m 6.00m 18.6 m2

Section modulus of bottom footing about y-axis --Zy =

(1/6)bd2 =

18.60 m3

For RCC Strip footing permissible bearing pressure is 1.5xSBC =

113KN/sqm

No tension is allowed on soil as per clause 706.3.3.1 of IRC 78:2000 S.No

1 2 3 4 1 2 3

S.No

1 2 3 4 1 2 3

Type of load

Intensity in KN (P)

Vertical loads:-(Stress = P/A(1+6e/b) Self wieght of Box Self weight of levelling concrete Live load with impact factor---(Wheel loads+UDL) [262.1*(1+0.495)] = Vertical component of Earth pressure Horizontal loads:- (Stress = M/Z) Wind load Tractive,Braking&Frictional resistance of bearings Horizontal load due to earth pressure

Type of load

Stress at up stream side edge of abutment =

961.80KN 159.84KN 391.84KN

0.007 0.00 -1.098

31.68KN

0.00

18.00KN 26.21KN 118.30KN

3.38 0.00 0.00

Intensity in KN (P)

Vertical loads:-(Stress = P/A(1+6e/b) Self wieght of Box Self weight of levelling concrete Live load with impact factor---(Wheel loads+UDL) [262.1*(1+0.495)] = Vertical component of Earth pressure Horizontal loads:- (Stress = M/Z) Wind load Tractive,Braking&Frictional resistance of bearings Horizontal load due to earth pressure

P/A(1+6e/b)+M/Z =

Eccentricity/Lever arm

Eccentricity

961.80KN 159.84KN 391.84KN

-0.007 0.00 1.098

31.68KN

0.00

18.00KN 26.21KN 118.30KN

3.38 0.00 0.00

35.73 KN/Sqm>0

Hence safe. Stress at down stream side edge of abutment =

P/A(1+6e/b)+M/Z =

Hence safe.

108.77 KN/Sqm0

Hence safe. Stress at toe =

P/A(1+6e/b)+M/Z =

109.24 KN/Sqm>113KN/sqm

Hence safe.

About y-axis:Breadth of footing b = Depth of footing d = Area of the footing = A = Section modulus of bottom footing about y-axis --Zy =

3.10m 6.00m 18.6 m2 (1/6)bd2 =

18.60 m3

For RCC Strip footing permissible bearing pressure is 1.5xSBC =

113KN/sqm

No tension is allowed on soil as per clause 706.3.3.1 of IRC 78:2000 S.No

1 2 3

Type of load

Vertical loads:-(Stress = P/A(1+6e/b) Self wieght of Box Self weight of levelling concrete =(5.5*12*0.30*24) Live load with impact factor---(Wheel loads+UDL) [301.5*(1+0.413)] =

Intensity in KN (P)

Eccentricity/Lever arm

850.60KN

0.01

159.84KN

0.00

391.84KN

-1.098

4

Uplift force due to flowing water

-156.75KN

0.00

5

Uplift force due to subsurface water

-194.37KN

0.00

6

Static water force due to water in drain

388.74KN

0.00

7

Static water force due to water in channel

13.49KN

2.40

8

Vertical component of Earth pressure

31.68KN

0.00

1

Horizontal loads:- (Stress = M/Z) Wind load

18.00KN

3.38

2

Tractive,Braking&Frictional resistance of bearings

26.21KN

0.00

3

Horizontal load due to earth pressure

118.30KN

0.00

4

Force due to water pressure

111.75KN

0.64

S.No

Type of load

Intensity in KN (P)

Eccentricity

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

Self wieght of Box

850.60KN

-0.01

2

Self weight of levelling concrete =(5.5*12*0.30*24)

159.84KN

0.00

3

Live load with impact factor---(Wheel loads+UDL) [301.5*(1+0.413)] =

391.84KN

1.098

4

Uplift force due to flowing water

-156.75KN

0.000

5

Uplift force due to subsurface water

-194.37KN

0.000

6

Static water force due to water in drain

388.74KN

0.000

7

Static water force due to water in channel

13.49KN

-2.400

8

Vertical component of Earth pressure

31.68KN

0.00

Horizontal loads:- (Stress = M/Z) 1

Wind load

18.00KN

3.38

2

Tractive,Braking&Frictional resistance of bearings

26.21KN

0.00

3

Horizontal load due to earth pressure

118.30KN

0.00

4

Force due to water pressure

111.75KN

-0.64

Stress at up stream side edge of abutment =

P/A(1+6e/b)+M/Z =

46.17 KN/Sqm>0

Hence safe. Stress at down stream side edge of abutment =

P/A(1+6e/b)+M/Z =

98.4 KN/Sqm113KN/sqm

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

52.41 8.59 -23.7 1.7 -3.27 0.0 0.0 35.73

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

51.01 8.59 44.2 1.7 3.27 0 0 108.77

KN/Sqm113KN/sqm

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

46.35 8.59 -23.7 -8.43 -10.45 20.9 4.09 1.7 3.27

0.0 0.0 3.9 46.17

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

45.11 8.59 44.2 -8.43 -10.45 20.9 -2.64 1.7

3.27 0 0 -3.85 98.4

KN/Sqm