box culvert load details

1.0 Introduction

2.0

Side wall thickness, Dw = 600 mmThickness of partition walls Dp = 300 mm 2 x 9250Clear height of box = 4835 mm

55

35

Thickness of deck slab Dd = 700 mm

Thickness of base slab Db = 700 mm 800

Base slab projection = 500 mm Idealised Frame (Along the road)

Earth fill over base slab (incidental) = 0 mm inside the waterway.Clear span of each box = 8650Idealised span of each cell L = 9250 mmIdealised height of box H = 4835 + 700 / 2 + 700 / 2 = 5535 mmCantilever length of base slab Lc = 500 + 600 / 2 = 800 mm

CWWidth of the structure , b = 12000 mm Width of footpath (removable) = 0 mm 5535Thickness of crash barrier = 500 mm 12000

Average thickness of fill over deck = 65 mmSection across Road

3.0 Load Calculations

3.1 Dead Loadsa.) Self weight of structure = ( Automatic Input by density command of STAAD Pro)

(Density of RCC is taken as 25

b.) Overburden over deck @ 22 0.065 m = 1.43 KN/m / m width

c.) Load due to crash barrier

C/s area of crash barrier = 0.395 Thus weight of crash barrier = 0.40 x 25.00 = 9.875 kN / m

Width of contact of load, b1 = 500 mm

Effective width of slab bef = (1/2)Ka(1-a/lo)+b1 ------ being edge load4625 mm ; b1 = 500mm (IRC-21 cl.no. 305.16)

b = 12000 mm 2.595K = 2.600 For continuous slabs; a = 2313 mm

2003 mm Thus load intensity due to crash barrier = 9.88 / bef

= 4.93 KN/m / m width

Thus total overburden load over deck slab = 1.43 + 4.93 = 6.36 KN/m / m

c.) Overburden over base slab:

Inside the cells = @ 20 0.000 m = 0.00 KN/m / m width

Over base slab heel = @ 20 5.600 m = 112.00 KN/m / m width

This design note includes the design and analysis of minor bridge at chainage CH.129+912 which is a box type having two cells.

Basic Data : As per client data / IRC requirements / Assumptions

KN/m3)

KN/m3 x

m2

lo = L = b/lo =

bef =

KN/m3 x

KN/m3 x

3.2 LIVE LOAD: (1 lane of 70R+1 lane of Class-A / 3 lane of Class-A is considered)3.3.1 Live Loads over DeckStructure is modelled in STAAD-PRO and analysed for 70R & Class-A loading to find position of loadingfor maximum bending moment and shear force. STAAD Input is attached in annexure-A & B.3.3.1.a. Impact Factors (IRC-6, Cl.no. 211)Span L = 9.25 mAs per IRC : 6, Basic impact factors are as below1. For 70R tracked vehicles = 10.00 %2. For 70R wheeled vehicles = 25.00 %3. For class A vehicle = 29.51 %Thickness of fill over deck < 600mm, hence impact fraction = 1

Design impact factors are:1. For 70R tracked vehicles = 10.00 %2. For 70R wheeled vehicles = 25.00 %3. For class A vehicle = 29.51 %

Width of carriageway at location of structure = 11000 mmThis is 3 lane as per IRC : 6 - 2000

3.2.1.b IRC Class 'A' vehicle along span

1.8 M c/c Ww Traffic Direction B

6.80 6.8 6.8 6.8 11.4 11.4 2.7 2.7Axle Loads

Axle spacing3 3 3 4.3 1.2 3.2 1.1

Dispersed Wheel Length

Tyre contact width along traffic direction, wtt = BTyre contact length after dispersion through slab & fill,Tyre contact width across traffic direction, =Width of load over wheels, W = mm

Width after dispersion through fill, b1 = mmThe various values are tabulated below.

Axle Load (T) B(mm) W(mm) b1(mm)11.4 250 500 1780 2300 24306.8 200 380 1730 2180 23102.7 150 200 1680 2000 2130

Part UDL intensity corresponding to each wheel load = Wheel Load / wtd

The load values for different axles are tabulated below.

11.4 64.0456.8 39.312.7 16.07

Effective width of slab bef = Ka(1-a/lo)+b1 Where K = 2.600 Same as that obtained above

Min clearance from slab edge to wheel outside, C = 650 mm

wtd

wtd = wtt+2(Tf + t) = B+2(Tf+ t) WwWw+1800

W+2Tf

Ww(mm) Wtd(mm)

Axle Load (T)

Part UDL intensity without impact (KN/m)

3.2.1.b.i. Load position for maximum moment at support

Impact factor = 29.51 %

Axle a (mm)

1750 5999 4333 4800 3933 3933 9.993 12.942

4500 8318 5106 5959 4320 4320 9.099 11.784

1500 5578 4193 4589 3863 3863 10.175 13.178

2800 7506 4835 5553 4184 4184 15.306 19.822

4000 8333 5111 5966 4322 4322 14.818 19.190

2050 6279 4426 4939 3980 3980 4.038 5.230

950 4346 3782 3973 3658 3658 4.394 5.690

3.2.1.b.ii. Load position for maximum mid span moment

The effective width values and load intensities are tabulated below. Impact factor = 29.51 %

Axle a (mm)

250 3062 3354 3331 3444 3354 11.719 15.177

3250 7911 4970 5756 4252 4252 9.244 11.9723rd 6.8T 3000 7400 4800 5500 4167 4167 9.433 12.2174th 6.8T 0 2130 3043 2865 3288 3043 12.915 16.7271st 11.4T 4300 8113 5038 5856 4285 4285 14.945 19.3552nd 11.4T 3750 7927 4976 5764 4255 4255 15.053 19.4951st 2.7T 550 3475 3492 3537 3512 3492 4.603 5.961

3.2.1.b.iii. Load position for maximum shear force

The eff. width values and load intensities are tabulated below. Impact factor = 29.51 %

Axle a (mm)

2000 6506 4502 5053 4018 4018 9.783 12.670

4250 8403 5134 6001 4334 4334 9.070 11.746

50 2439 3146 3020 3340 3146 20.355 26.361

bef for load at centre of carriageway (mm)

bef for one train at edge

bef for 3 trains at edge of

carriageway

bef for design

Load in KN/m2

without impact

Load in (KN/m2) wiith

impactfor single train befc

for 3 trains bef2

befc/2 + W/2

1st 6.8T

2nd 6.8T

3rd 6.8T

1st 11.4T

2nd 11.4T

1st 2.7T

2nd 2.7T


bef for load at edge


carriageway

bef for design

Load in KN/ M2

without impact

Load in (KN/M2) wiith


for 3 trains bef2

befc/2 + W/2

1st 6.8T

2nd 6.8T


bef for load at edge


carriageway

bef for design

Load in KN/ M2

without impact



for 3 trains bef2

befc/2 + W/2

1st 6.8T

2nd 6.8T

1st 11.4T

1250 5121 4040 4360 3787 3787 16.913 21.903

4450 8314 5105 5957 4319 4319 3.721 4.819

3700 8082 5027 5841 4280 4280 3.755 4.863

3.2.1.c. 70R wheel load along span

Tyre contact length = (5000/5.273)/(41-5) = 26.34 cm =2.79 Traffic Direction 263mm = Wtt

8 12 12.0 17.0 17.0 17.0 17.0 Axle Loads (Ton)

3.96 1.52 2.13 1.37 3.05 1.37 Axle Spacings (M)

Tyre contact length after dispersion through slab & fill1793 mm Dispersed

Width of load over wheels, W = 2790 mm Wheel Length2920 mm

1793Part UDL intensity without impact corresponding to each wheel load

= Wheel Load / wtd = Load / 1793 mmThe load values for different axles are tabulated below.

17.0 94.79212.0 66.9128.0 44.608

Effective width of slab Where K = 2.600 Same as that for Class-A

Min. clearance from slab edge to wheel outside, C = 1700 mm

i. Load position for maximum shear force

The effective width values and load intensities are tabulated below. Impact factor = 25.00%

Axle a (mm)

3400 8511 7350 7350 12.896 16.120

4770 8927 7558 7558 12.541 15.677

1430 6063 6127 6063 15.634 19.542

60 3075 4632 3075 30.827 38.533

2070 7098 6644 6644 10.071 12.589

3590 8631 7411 7411 9.029 11.286

1700 6528 6359 6359 7.015 8.769

2nd 11.4T

1st 2.7T

2nd 2.7T

along span wtd = wtt+2(Tf + t) =

Width after dispersion through fill, b1 = W+2Tf =

Axle Load (T)

Part UDL intensity Without impact (KN/m)

bef = Ka(1-a/lo)+b1


- befc

bef for load at edge of carriageway befe = (befc/2 + W/2 +C)

bef for design

Load in KN/m2

without impact

Load in (KN/m2) wiith

impact

1st 17T

2nd 17T

3rd 17T

4th 17T

1st 12T

2nd 12T

1st 8T

ii. Load position for maximum mid span moment

The effective width values and load intensities without impact are tabulated below. Impact factor = 25.00%

Axle a (mm)

950 5136 5663 5136 18.455 23.069

2320 7439 6815 6815 13.910 17.388

3880 8776 7483 7483 12.667 15.834

2510 7675 6933 6933 13.673 17.092

380 3867 5029 3867 17.301 21.627

iii. Load position for maximum support moment

The effective width values and load intensities without impact are tabulated below. Impact factor = 25.00%

Axle a (mm)

3250 8401 7296 7296 12.993 16.241

1880 6815 6502 6502 14.578 18.223

1170 5577 5884 5577 16.996 21.245

2540 7711 6950 6950 13.639 17.048

4580 8932 7561 7561 8.850 11.062

3060 8244 7217 7217 9.271 11.589

3.2.1.f. Live Load braking effect

Live load braking effect = 20% of LL on first two lanes + 5% of LL on remaining lanes.

The structure will be maximum loaded when 70R wheel loads and a Class A wheel loadare placed over the structure.

Thus total load over deck = 100 T load from 70R wheel= 55.4 T load from Class A wheel

Total braking effect force on structure = 22.77 T = 22.77x10 / 12.000 / 3.000 = 6.32 KN/m/wall

3.3 Seismic ForcesThe dynamic pressure increments are calculated as per IS: 1893 – 1984.

= 0.04x1.0x 1.2 = 0.048 For seismic Zone III0.024


- befc


bef for design

Load in KN / m2

without impact


impact

1st 17 T

2nd 17 T

3rd 17 T

4th 17 T

1st 12 T


- befc


bef for design

Load in KN / m2

without impact


impact

1st 17 T

2nd 17 T

3rd 17 T

4th 17 T

1st 12 T

2nd 12 T

Live Load Calculations for 70 R Track load and Boggie load is given in Annexure IV.

ah = abc av = 0.048/2 =

F =

= 0.0468 Rad And 0.0491 Rad

28° = 0.488692 Rad

0 0 0

0.448 And 0.447

2.098 And 2.094Ca = 0.400 And 0.383

Dynamic increment 0.103 And Ca' = 0.086

The earth pressures are calculated below. The static component is same as already calculated.

Saturated Backfill E.P. at slab top level = = 7.13 KN/M / M widthE.P. at founding level = = 95.96 KN/M / M widthDynamic increment = = 8.16 KN/M / M width

Thus the seismic effect is very small as the dynamic earth pressure, which is only about 15.8%of the static component whereas the permissible stresses can be increased by 50% . Thus not considered in further analysis.

Active pressure coeficient; Ca = (1+/- av)cos2( -f l – a)

Cosl cos2a cos(d + a + l) *(1+ F0.5)2

Sin (f + d ) Sin ( f – t – l ) Cos (a - t ) Cos ( +d +a l )

l = tan-1(ah/(1+/- av))

f =

a = t = d =

Thus, F0.5 =

(1+ F0.5)2 =

KarHs/1000Kar(Hs+H) /1000Ca'r(Hs+H/2) /1000

4.0 Modulus of Subgrade ReactionJoseph E. Bowles in book named "Foundation analysis and design" recommends a value range of

Adopt a value of say 8,000 Providing springs at every 0.450 m spacing, Value of spring constant = 8000 x 1.000 x 0.450 = 3600 KN/M Value of spring constant = 8000 x 1.000 x 0.525 = 4200 KN/M (For supports below wall) Value of spring constant = 8000 x 1.000 x 0.350 = 2800 KN/M (For supports next to support below wall) Value of spring constant = 8000 x 1.000 x 0.4000 = 3200 KN/M (For extreme support)

5.0 Bearing capacity requirement. 4.1 Due to Dead Loads Weight of base slab = 20.10m x 0.70 m x 25 = 351.75 KN/m width Weight of top slab = 19.10m x 0.70 m x 25 = 334.25 KN/m width Weight of side walls = 2x4.84 x 0.60 m x 25 = 145.05 KN/m width Weight of partition wall = 4.84 x 0.30 m x 25 = 36.26 KN/m width Weight of key = 1.00 m2 x 25 = 25.00 KN/m width Weight of haunch = 1.44 m2 x 25 = 36.00 KN/m width Wt. of soil fill inside box = 6x0.00 x 0.00 m x 0 = 0.00 KN/m width Soil fill on base slab projn = 2x0.50 x 5.54 m x 22 = 121.77 KN/m width Wt of fill on deck slab = 19.10m x 0.07 m x 22 = 27.31 KN/m width

Total 1077.40 KN/m width

Thus bearing pressure due to DL = 1077.40 / 20.10m = 53.60

4.2 Due to crash barrier. Wt of crash barrier = 2x19.10x 9.88 = 377.23 KN

0.00 m , 20.10 m 12.00 m

Thus, Pmax = 1.56 Pmin = 1.56

4.3 Due to Live Loads Considering 3 lanes of Class-A near crash barrier,

P = 2152.4262 KN, 0.33 m 0.15 m

12.00 m 20.10 m

Thus, Pmax = 10.78

Considering one 70R + 1 Class-A wheel load near crash barrier,

P = 1967.4743 KN, 1.38 m 2.85 m

12.00 m 20.10 m

Thus, Pmax = 20.74

Thus maximum bearing pressure due to Live load = 20.74

Thus bearing capacity requirement = 53.60 + 1.56 + 20.74

= 75.90

Say 8

6.0 Temperature Forces

1.17E-05 Permissible stresses can be increased by 15% under temperature effects.

9,600 to 80,000 KN/M3 for medium dense sand stratas.

KN/m3 on a conservative side.

KN/m2

et = LL = , Lt =

KN/m2 KN/m2

et = eL =

Lt = LL =

KN/m2

et = eL =

Lt = LL =

KN/m2

KN/m2

KN/m2

T/m2 < 10 T/m2 Hence OK

Temperature variation = + 17o

Coeficient of thermal expansion , a = / oC

box culvert load details

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