Substructure_Final_.pdf

2.0 Design of Substructure 2.1 Design of Abutment Section of Abutment 0.25

0.3

1.00

288.3 Deck Level 0.2 A6 A7

1.0

0.5

2.3

0.5 A5

0.18

0.0

A2

1

0.0

284 HFL

0.1 A3

3.00 5.30 Y

0.6294

A1

280.32 MSL

0.1706 3.438 A4

x

A

279.52 SBL 1.20

1.70

0.20

A8

T

277.82 FBL

This prelimanry section is defined by considering hydrological analysis and geotechnical recommendation

SBL = Stem Bottom Level FBL = Footing Bottom Level MSL = Maximum Scour Level

Material Properties Concrete grade Steel grade Allowable stress of steel in tension and shear Allowable stress of steel in direct compression Allowable compressive stress in concrete in flexure Allowable comp. stress in concrete in direct compression Modular ratio (m) Neutral axis factor The resisting moment coefficient

(fck) (fe) Sst = Ssc = Scbc = Scc = m=

20 500 240 205 6.67 5 11

k

0.32

j

0.89

R

0.95

N/mm² N/mm² N/mm² N/mm² N/mm² N/mm²

IRC:21-2000, 303.2.1, Table 9,10 Levels High Flood Level Maximum Scour level for abutment Total depth of longitudinal Girder including Slab Provided Clear free board Level of Deck Surface Thickness of abutment cap Top level of Footing (SBL) Thickness of Footing/Cap Bottem level of Footing/Cap (FBL) Thickness of Bearing Hence the total height of abutment H=

284 280.32 2.3 2.00 288.30 1.00 279.52 1.70 277.82 0.18 8.78

m m m m m m m m m m m

Substructure Kamala Khola_Bridge Project

As per IRC : 6-2000, 217.1 for Equivqlent live load Surcharge Equivalent Height of Abutment Length of Abutment Span Length

1.2 9.98 7.2 36.95

H eq= L=

m m m m

Approach Slab Diamensions Thickness of approach slab Length of Approach Slab Width of Approach Slab Ballast Wall Width of Ballast wall Length of Ballast wall Wing Wall Thickness of wing wall

0.2 m 3.00 m 7.2 m 0.3 m 7.2 m 0.4 m

Soil Data & Seismic Data Unit weight of backfill soil Unit weight of concrete Horizontal seismic coefficient Vertical seismic coefficient

γ ω_conc αΗ αν

16 kN/m³ 24 kN/m³ 0.120 0.060 Degree

Angle between the wall and earth Angle of internal friction of soil Angle of friction between soil and wall

α φ δ

0 30 16

Analysis and Design of Abutment Stem Area and C.G Calculation with respect to bottom of stem point A 2

Area (m ) CG-X CG-Y Weight (KN) Symbol A1 2.63 0.15 4.39 455.16 A2 1.00 0.80 5.80 172.80 A3 5.830 0.78 2.65 1007.42 A4 0.53 1.27 1.77 91.58 A5 0.00 0.00 7.78 0.00 A6 0.00 0.00 8.28 0.00 A7 0.13 -0.13 8.33 21.60 Total 10.12 1748.56 C.G from A 0.6294 3.438 Position of C.G From Superstructure Load Point 0.1706

Substructure Kamala Khola_Bridge Project

Forces on the Abutment Total Dead Load from superstructure Total Critical Live load including impact

2222.4 KN 1302.9 KN

Earth Pressure force (Including live load surcharge)

[IRC:6-2000, 217.1]

Total Static earth pressure = 0.5* γ * Heq² * tan²(45° - φ/2)*L =

411.89685 KN

Which act at a distance from abutment base (0.42*Heq)

Effect of buyoncy

4.1916 m

[IRC:6-2000, 216.4 (a)]

Area of stem at top = Depth of submerged part of abutment = Area of stem at base = Area of stem at HFL = Volume of submerged part of abutment = Taking 1/2 of the volume, Net upward force due to buyoncy =

8.64 4.48 10.08 9.8572075 44.659345 -223.2967

m² m m² m² m³ kN

Frictional force due to resistance of bearings (temperature effect) Coefficient of thermal expansion of concrete (C) = Length of main girders (L) Width of girder (a) Assume width of elastomeric bearing (parallel to span) (b) Assume thickness of elastomeric bearing (T) Differential temperature in celcius (dt) Number of main girders = Assume Shear modulus of elastomer (G) (range 0.6 to 1.2) Elongation of the girder (D) = C*L*dt Plan area of the bearing (A) = Longitudinal force transmitted to the pier F = G*A*D / T = Total force from all bearings Lateral force due to frictional resistance of bearings,

0.000009 36950 400 300 50 30 3 1.2

mm mm mm mm degree N/mm²

9.9765 mm 120000 mm² 28.73232 kN per bearing 86.20 kN 86.20 kN

(From S. Sir) Breaking Force:( As Per IRC:6-2000, 214.2) Braking force = 20% of the weight of the design vehicle (Class A) And this force acts along the bridge at 1.2m above the road level Total weight of the IRC Class A vehicle = Therefore braking force length =

9.98 m from base 543.29 kN 54.329 kN

Seismic Forces on Abutment [IRC : Seismic Forces Due to back fill and Approach Slab are also considered.

Horizontal seismic forces: Superstructure: Abutment: Backfill soil mass: This forces will act at 0.5 Heq

266.69 209.83 49.43 4.99

kN kN kN m

Vertical seismic forces: Superstructure: Abutment:

133.34 kN 104.91 kN

Substructure Kamala Khola_Bridge Project

Loads and Moment Calculation The transverce forces and moments are not calculated since it will not be critical due to high moment of inertia. Load Horizon Vertical Coefficient Moment Vertical Horizontal Lever arm, Particular tal force Lever arm, (kN.m) force (kN) (m) IRC:6-2000, (m) (kN) 202.3 combination I

Dry case, Non-seismic

Increment factor for allowable stresses*

1

Superstructure dead load

1

2222.40

Live load

1

1302.87

0.80

1042.30

Abutment

1

1748.56

-0.63

-1100.57

Soil mass

1

411.90

4.19

Tractive/Braking force

1

54.33

9.98

542.20

Frictional force

1

86.20

6.30

543.04

552.42

20.47

4531.40

Total combination VI Non seismic forces Superstructure dead load

0.80

5273.84 Dry case, Seismic

1777.92

Increment factor for allowable stresses*

1726.51

1.5

1

2222.40

0.80

1777.92

0.5

651.44

0.80

521.15

Abutment

1

1748.56

-0.63

Soil mass

1

411.90

4.19

Tractive/Braking force

0.5

27.16

9.98

271.10

Frictional force

0.5

43.10

6.30

271.52 1834.82

Live load

-1100.57 1726.51

Additional seismic forces Superstructure

1

133.34

0.800

266.69

6.48

Abutment

1

104.91

-0.629

209.83

3.44

655.38

Soil mass Total

1

49.43 1008.10

4.99

246.64 6204.47

4860.66

combination I-a Flooded case, Non-seismic

Increment factor for allowable stresses*

1

Superstructure dead load

1

2222.40

Live load

1

1302.87

0.80

1042.30

Abutment

1

1748.56

-0.63

-1100.57

Soil mass

1

411.90

4.19

Tractive/Braking force

1

54.33

9.98

542.20

Frictional force

1

86.20

6.30

543.04

Buyoncy

1

552.42

20.47

4531.40

Total combination VI-a Non seismic forces Superstructure dead load Live load Abutment Soil mass

0.80

1777.92

1726.51

-223.30 5050.54

Flooded case, Seismic

Increment factor for allowable stresses*

1.5

1

2222.40

0.80

0.5

651.44

0.80

1777.92 521.15

1

1748.56

-0.63

-1100.57

1

411.90

4.19

Tractive/Braking force

0.5

27.16

9.98

271.10

Frictional force

0.5

43.10

6.30

271.52

Buyoncy

1

1726.51

-223.30

Additional seismic forces Superstructure

1

133.34

0.80

266.69

6.48

1834.82

Abutment

1

104.91

-0.63

209.83

3.44

655.38

Soil mass

1

49.43

4.99

Total

4637.36

Maximum Loads

5273.84

Increment factor for allowable stresses*

246.64

1008.10

6204.47

1008.10

6204.47

IRC:6-2000, 202.3

Substructure Kamala Khola_Bridge Project

2.1.1 Design of abutment stem Section Abutment Stem will be designed as compression member with uniaxial moment. Overall Thickness of Stem at base Length of the abutment Gross cross sectional area of the stem percentage of longitudinal tensile reinforcement the percentage of longitudinal compressive reifnrocement Percentage of steel to be provided as per IRC:21-2000, 306.2.2 Total percentage of longitudinal reinforcement = Then the initial total area of reinforcement Net area of concrete Let the effective cover (referring to the CG of bars) Hence the effective depth

D= L= Ag =

1400 mm 7200 mm 10080000

pst psc

Asc = Ac = cover (d')= d_eff =

0.25 0.11 0.3 0.36 36288 10043712 65 1335

Moment of inertia I = 1.428.E+12 Section modulus Z = 2.139.E+09 Radius of gyration SQRT(I/Z*L) k= 385 Height of the abutment (upto abutment cap) 6300 Effective length (height) factor (IRC:21-2000, 306.1.2, Table 13) = 1.75 Effective height of the abutment 11025 Ratio of Effective length : Radius of gyration = 28.61 Hence it is treated as a Short Column The direct comp. stress, Scc_cal = P/(Ac+1.5*m*Asc) N/mm² The comp. stress in bending Scbc_cal = M/Z N/mm² Interaction Condition to be satisfied: [Scc_cal/Scc] + [Scbc_cal/Scbc] =