Bridge Abutment Pier Design as Per IRC

Design Abutment Foundation

Page 1

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

0.4

40 m Standard DoR Superstructure 10 Nos of Span 215.5 Deck Level Concrete Grade 3 All Concrete M30

1.5

0.3 A6 A7

1.0

0.5 0.61

A5

0.5

3.4

A2

0.9

3.5

210.5 HFL

0.00 A3

3.50 6.50 Y

1.0020

A1

206.7 AGL 203.00 LBL

0.01 4.005 A4

x

0.4

A

204.60 SBL 1.50

1.50

0.30

A8

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

T

SBL = Stem Bottom Level CTL = Cap Top Level AGL = Average Ground 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=

30 500 240 205 10.00 7.5

N/mm² N/mm² N/mm² N/mm² N/mm² N/mm²

10

k

0.29

j

0.90

R

1.33

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

Abutment_openFoundation

210.5 206.7 3.00 1.5 215.50 0.9 204.60 1.50 203.10 0.3 0.2 10.90

m m m m m m m m m m m m

Rapti Bridge Design 5_3_Pile.xls

Design Abutment Foundation

Page 2

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

1.2 12.1 11 40

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

0.3 m 33.50 50 m 11 m 0.4 m 11 m 0.4 m

Soil Data & Seismic Data Unit weight of backfill soil Unit weight of concrete Horizontal seismic coefficient Vertical seismic coefficient 0.36 Zone Factor (z) Importance Factor(I) 1

 conc  

A l b t th th Angle between the wallll andd earth Angle of internal friction of soil Angle of friction between soil and wall

  

16 kN/m³ 24 kN/m³ 0.150 0.075

Degree 0 35 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 1.76 0.20 5.45 464.64 A2 1.35 1.15 6.95 356.40 A3 9.750 1.13 3.25 2574.00 A4 0.98 2.00 2.17 257.40 A5 5.95 -1.17 8.77 57.12 A6 3.50 -1.75 10.40 33.60 A7 0.13 -0.13 10.35 33.00 Total 23.41 3776.16 C G ffrom A C.G 1 0020 1.0020 4 005 4.005 Position of C.G From Superstructure Load Point 0.0080

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

4280.00 KN 1186.00 KN

Earth Pressure force (Including live load surcharge) Total Static earth p pressure = 0.5*  * Heq² * tan²(45° ( - / /2)*L ) = Which act at a distance from abutment base (0.42*Heq)

Effect of buyoncy

I.F

1.0978

1282.6 KN

[IRC:6-2000, 217.1] 3491.4575 KN 5.082 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 =

Abutment_openFoundation

16.5 5.90 19.8 19.495385 115.92138 -579.6069

m² m m² m² m³ kN

Rapti Bridge Design 5_3_Pile.xls

Design Abutment Foundation

Page 3

Frictional force due to resistance of bearings For Pot Bearing Vertical dead Load Total No of Bearing Per Abutment

2140 kN 2 2 250000 mm 8.56 kN/mm2

Contact area of Pot Bearing (Assuming size 500mmX500mm) Contact Stress (sp) Pot bearing constant (k) Maximum i Friction i i C Coefficient ffi i μmax =

1.00 0.065

Maxmimum Frictional Force Total Lateral force due to frictional resistance of bearings, Lateral force due to frictional resistance of bearings,

138.36 kN 276.72 kN 276.72 kN

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 =

12.10 m from base 543.29 543 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

642.00 566.42 523.72 6.05

kN kN kN m

Vertical seismic forces: Superstructure: Abutment:

321.00 kN 283.21 kN

Loads and Moment Calculation The transverce forces and moments are not calculated since it will not be critical due to high moment of inertia. Taking Moments on C.G of Abutment Load Horizon Vertical H i V i l Coefficient Vertical force Horizontal Lever arm, Particular tal force Lever arm, (kN) (m) IRC:6-2000, (kN) (m) 202.3 combination I Superstructure dead load

Dry case, Non-seismic 1

Increment factor for allowable stresses*

4280.00

Moment (kN.m) 1

0.01

34.17 10.24

Live load

1

1282.55

0.01

Abutment

1

3776.16

0.00

Soil mass

1

0.00 3491.46

5.08

17743.59

Tractive/Braking force

1

54.33

12.10

657.38

Frictional force

1

276.72

7.40

2047.76

3822.51

24.58

20493.14

Total combination VI

9338.71 Dry case, Seismic

Increment factor for allowable stresses*

Abutment_openFoundation

1.5

Rapti Bridge Design 5_3_Pile.xls

Design Abutment Foundation Non seismic forces Superstructure dead load Live load Abutment Soil mass

Page 4 1

4280.00

1.01

0.5

641.28

0.01

4322.80 5.12

1

3776.16

0.00

0.00

1

3491.46

5.08

Tractive/Braking force

0.5

27.16

12.10

17743.59 328.69

Frictional force

0.5

138.36

7.40

1023.88 5074.36

Additi l seismic Additional i mi forces f r Superstructure

1

321.00

0.008

642.00

7.90

Abutment

1

283.21

0.000

566.42

4.01

2268.63

Soil mass Total

1

523.72 5389.13

6.05

3168.50 33935.57

9301.65

combination I-a Flooded case, Non-seismic

Increment factor for allowable stresses*

1

Superstructure dead load

1

4280.00

0.01

34.17

Live load

1

1282.55

0.01

10.24

Abutment

1

3776.16

0.00

Soil mass

1

0.00 3491.46

5.08

17743.59

Tractive/Braking force

1

54.33

12.10

657.38

Frictional force

1

276.72

7.40

2047.76

Buyoncy

1

3822.51

24.58

20493.14

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

-579.61 8759.10

Flooded case, Seismic

Increment factor for allowable stresses*

1.5

1

4280.00

0.01

0.5

641.28

0.01

34.17 5.12

1

3776.16

0.00

0.00

1

3491.46

5.08

Tractive/Braking force

0.5

27.16

12.10

328.69

Frictional force

0.5

138.36

7.40

1023.88

Buyoncy

1

17743.59

-579.61

Additional seismic forces Superstructure

1

321.00

0.01

642.00

7.90

5074.36

Abutment

1

283.21

0.00

566.42

4.01

2268.63

Soil mass

1

523.72

6.05

Total

8722.04

Maximum Loads

9338.71

Increment factor for allowable stresses*

3168.50

5389.13

29646.94

5389.13

33935.57

IRC:6-2000, 202.3

Abutment_openFoundation

Rapti Bridge Design 5_3_Pile.xls

Design Abutment Foundation

Page 5

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, IRC:21 2000 306.2.2 306 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 =

1800 mm 11000 mm 19800000

pst psc

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

0.25 0.13 03 0.3 0.38 75240 19724760 65 1735

mm² % % % % OK mm² mm² mm mm 4

Moment of inertia I = 4.788.E+12 mm Section modulus Z = 5.519.E+09 mm³ Radius of gyration SQRT(I/Z*L) k= 501 mm Height of the abutment (upto abutment cap) 6500 mm Effective length (height) factor (IRC:21-2000, 306.1.2, Table 13) = 1.75 Effective height of the abutment 11375 mm Ratio of Effective length : Radius of gyration = 22.71 Hence it is treated as a Short Column Th di t The directt 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] =