chapter 8 rehabilitation and retrofitting of existing bridges

CHAPTER 8

REHABILITATION AND RETROFITTING OF

EXISTING BRIDGES

THE KANCHPUR, MEGHNA, GUMTI 2ND BRIDGES CONSTRUCTION AND EXISTING BRIDGES REHABILITATION PROJECT

Final Report

8-1

8. REHABILITATION AND RETROFITTING OF EXISTING

BRIDGES

8.1 Background

8.1.1 General

Having examined the survey results described in the previous chapter, it can be said that the

deteriorations of Kanchpur Bridge, Meghna Bridge and Gumti Bridge were only a result of

normal aging except those of the expansion joints in all the bridges and the hinges in Megna

Bridge and Gumti Bridge.

The reasons for the damages on the hinges and expansion joints in Meghna Bridge and Gumti

Bridge were described in the last clause of this chapter. It is considered the reasons for the

damages on the expansion joints in Kanchpur Bridge were the same as the other two bridges;

Heavily overloaded trucks,

Inappropriale maintenance.

8.1.2 Additional Information

RHD, consulting BUET, has requested the Army to execute emergency repair works such as;

for Meghna Bridge

Protection of P7 or P8 against the river bed scouring,

Replacement of the expansion joints, 9 nos.,

THE KANCHPUR, MEGHNA, GUMTI 2ND BRIDGES CONSTRUCTION AND EXISTING BRIDGES REHABILITATION PROJECT Final Report

8-2

Repair of the hinges involving 36 pot bearings,

for Gumti Bridge

Replacement of the expansion joints, 15 nos.,

Repair of the hinges involving 60 pot bearings.

The budget for the works planned is considered to be 1.5 billion BDT.

On 19 May 2012, RHD, BUET and the Army held a meeting and it was decided that the

works will start after the rainy season has finished, around 3 months later.


Final Report

8-3

8.2 Configuration of Existing Bridges

8.2.1 Existing Kanchpur Bridge

Basic data of existing Kanchpur Bridge are shown in Table 8.2.1.

Table 8.2.1 Basic Data of Existing Kanchpur Bridge

Bridge Existing Kanchpur Bridge

Consultant Anman and Whitny

Contractor Obayashi Corporation

Period of Construction September 1973 to September 1977

River Lakhya River

Bridge length 396.5 m (4×42.7 m+54.9 m+ 73.2 m+ 54.9 m+ 42.7 m)

Bridge width 14.64 m (12.81 m(road) + 2×0.686 m(sidewalk) + 2×0.229 (Railing)) Pre-stressed concrete I girder, continuous type (54.9 m+ 73.2 m+ 54.9 m)

Superstructure Pre-stressed concrete I girder, simply supported type (42.7 m5 spans)

Abutment Inverted T-type Pier Rigid frame-type

Bridge components

Substructure Foundation

Abutment: Spread foundation Pier: RC open caisson

Construction method Erection by staging

Loads Live load AASHOTO (HS20-44 ASD) (available at the time of construction)

Concrete

Slab: 21 N/mm2 Girder: 35 N/mm2 Abutment and pier: 21 N/mm2 Caisson: 18 N/mm2

Reinforcing bar ASTM A 615, Grade 60 (available at the time of construction)

Materials

Pre-stressing steel SWPR7A 12S12.4 (assumed for restoration design)

TH

E K

AN

CH

PU

R, M

EG

HN

A, G

UM

TI 2N

D B

RID

GE

S C

ON

ST

RU

CT

ION

A

ND

EX

IST

ING

BR

IDG

ES

RE

HA

BILIT

AT

ION

PR

OJE

CT

F

inal Report

8-4

φ4550

▽RL+2.000 117472124

9623

-10.000

-20.000

-30.000

20.000

0.000

10.000

▽RL-17.812

▽RL+1.000

▽RL-18.812

1866

12451

2124

14575 1866

2124

15854

13730

▽RL+1.000

▽RL-20.336

▽RL+1.000

▽RL-23.384

1950 14687

16811

2124

12534

15115

2581

2065

▽RL+1.000

▽RL-27.956

12681

15262

2581

▽RL+1.000

▽RL-27.956

2065

16828

14704

2124

▽RL+1.000

1950

▽RL-20.336

P1 P2 P3 P4 P5 P6 P7

2562 2562

2562

2562

4923

4923

2562

19812

19812

φ4550 φ4550

21336 φ4550

24384

1866

φ6510

28956

φ6510

28956

φ4550

21336

42700 42700 42700 42700 54900 73200 54900 42700

396500

4550

13590

4550 4550 4550 6510

15550

6510 4550

42700 42700 42700 42700 54900 73200 54900 42700

396500

15250 42700 15250

P1 P2 P3 P4 P5 P6 P7

PROFILE

PLAN

915

14640

915 12810

CL

915 12810 915

229 14182 229

686 12810 686

14640

915

229

176

8381297

838

176

2286

P3 PIER

GRADIENT

PROPOSED HEIGHT

STATION

DISTANCE

GROUNO HEIGHT

i=3.32%

L= 21.185

3416 1829 1905

9141067

341618291905

1981

13730 15854

143

15550

13590

13590

13590

13590

13590

68323379 3379

6@2135=12810

-SH WL=+5.00 12000

61000（航路）5

700

1388 517

1113 366

A1

A2

A1 A1

A114.431

P1

16.309

P2

18.137

P3

19.416

P4

20.373

P5

21.038

P6

21.185

P7

20.990

A2

19.467

CROSS SECTION

SECTION

（PC I GIRDER）

i=L=

M FFM F

F F MFF

To Dhaka

To Chittagong

Figure 8.2.1 General View of Existing Kanchpur Bridge


Final Report

8-5

8.2.2 Existing Meghna Bridge

Basic data of existing Meghna Bridge are shown in Table 8.2.2.

Table 8.2.2 Basic Data of Existing Meghna Bridge

Bridge Existing Meghna Bridge

Consultant Pacific Consultants International in consortium with Nippon Koei Co., Ltd.


Period of Construction March 1987 to February 1991

River Meghna River

Bridge length 930 m (48.5 m+ 9x87.0 m+ 48.5 m+ 2x25.0 m)

Bridge width 9.2 m (7.2 m(road) + 2×1.0 m(Sidewalk +Railing)) Pre-stressed concrete box girder, continuous rigid frame type (48.5 m+ 9×87.0 m+ 48.5 m)

Superstructure Pre-stressed concrete T girder, simply supported type (2×25.0 m)

Abutment Inverted T-type Pier Columnar type

Bridge components


Abutment: RC pile (φ1500) Pier: RC pile (φ1500)

Construction method Balanced cantilever erection

Live load AASHOTO HS20-44 ASD

Seismic load Horizontal load coefficient taken as 0.05 g

Wind load Without live load (V=140 MPH): 0.479 T/m2 With live load (V=100 MPH): 0.244 T/m2

Loads

Thermal force Temperature range: 26 °C±17 °C

Concrete

Cylinder compressive strength at 28 days Pier, Abutment, Pile cap: 240 kgf/cm2 PC box girder, PC- T beam, PC slab: 350 kgf/cm2 RC pile: 300 kgf/cm2

Reinforcing bar Tensile strength: 4,950 kgf/cm2 Yield stress: 4,250 kgf/cm2

Materials

Prestressing steel

SWPR7A (12T12.4) SWPR19 (1T19.3) SWPR19 (1T21.8) SBPR 95/110 (φ32)

TH

E K

AN

CH

PU

R, M

EG

HN

A, G

UM

TI 2N

D B

RID

GE

S C

ON

ST

RU

CT

ION

A

ND

EX

IST

ING

BR

IDG

ES

RE

HA

BILIT

AT

ION

PR

OJE

CT

F

inal Report

8-6

1500 4000 1500

2000

5200

2000

▽RL-52.000

RL 0.000

300

(RL±0)

RL+10.000

RL+20.000

RL+30.000

RL+40.000

RL-10.000

RL-20.000

RL-40.000

RL-30.000

RL-60.000

RL-50.000

CAST-IN-SITU RC PILEφ1.5m N=4 L=48.0m

9200

9200

7000

11000

8000

4000 2022

M

48500

11000

1500

2X4000

=8000 1500

1500

11000

15002X4000

=8000

2700

750

5000

750

3200

1500

2X4000

=8000

1500

11000

1500

11000

1500

2X4000

=8000

87000

750

6000

750

A1 P1 P2

▽RL-52.900

A1

P1

17433

14933

500

▽RL+12.433

5922

2700

100 11000 100


24543

▽RL-53.400

φ1.5m N=9 L=44.0mCAST-IN-SITU RC PILES

P2

2000

1500

45711000457

5922

▽RL+15.043

3200

▽RL-5.000

▽RL-9.500

500

3500

3500

P3

3200

1500

1500

2X4000

=8000 1500

11000

1500

2X4000

=8000

11000

7505000

750

87000

3200

P3

▽RL-52.400

CAST-IN-SITU RC PILE

457 45711000

φ1.5m N=9 L=43.0m

5922

▽RL-9.500

1500

27153

3500

2000 50024653

▽RL+17.653

P4

3200

1500

1500

11000

1500

2X4000

=8000

15007505000

750

11000

2X4000

=8000

87000

φ1.5m N=9 L=43.0mCAST-IN-SITU RC PILES

27063

29763 3200

P4

▽RL-52.400

11000 457457

500

2200

1500 ▽RL-9.500

3500

5922

▽RL+20.263

P5

3200

1500

1500

11000

2X4000

=8000

1500

11000

1500

2X4000

=8000

7505000

750

87000

29194

31894

P5

▽RL-52.400

φ1.5m N=9 L=43.0m

▽RL-9.500

CAST-IN-SITU RC PILES

11000 457457

500

2200

1500

3200

▽RL+23.000

5922

3500

15004000

4000 1500

▽RL+22.394

4750 4750

P6

1500

3200

2X4000

=8000

11000

1500

750

5000

750

87000

3200

31894

29194

457

▽RL-54.400

457 11000

1500

2200 500

P6

5922

▽RL+22.394

3500

RL 0.000

RL +5.000

75000

▽SHW▽RL+5.900

100 7000 100

930000

930000

48500 87000 87000 87000 87000 87000

4844060

48000420

43440 120 43440 43420 160 43420 43420 160 43420 43420 160 43420 43420 160 43420

2022

2022

2022 2022

2022

18

19

20

21

22

23

24

25

26

27

28

15.850

GRADIENT

PROPOSED HEIGHT

GROUND HEIGHT

ELEVATION OF BOTTOM

FACE OF PILE CAP

DISTANCE

18 19 20 21 22 23 24 25 26 27 28

17.350

18.850

20.350

21.850

23.350

24.850

26.350

27.756

28.506

28.506

RL-5.500

+18.500

P6

RL-9.500

28.376

RL-7.000

+31.500

P5

RL-9.500

28.316

RL-8.255

+44.500

P4RL-9.500

26.185

RL-8.255

+7.500

RL-9.500

23.575

P3

RL-5.500

+20.500

P2

RL-9.500

20.965

18.355

RL-0.500

+33.500

RL-5.000

P1

RL+4.300

RL+5.900

+35.000

A1

16.900

+25.000

28.600

31.100

27.100

i=3.000%

PROFILE

PLAN

（航路） 18000

P6P5P4P3P2P1

A1

To Dhaka

TH

E K

AN

CH

PU

R, M

EG

HN

A, G

UM

TI 2N

D B

RID

GE

S C

ON

ST

RU

CT

ION

A

ND

EX

IST

ING

BR

IDG

ES

RE

HA

BILIT

AT

ION

PR

OJE

CT

F

inal Report

8-7

11000

φ1.5m N=9 L=43.0m

L-9.500

CAST-IN-SITU RC PILES

L+23.000

P6

1500

2X4000

=8000

11000

1500

1500

3200

2X4000

=8000

11000

1500

750

5000

750

87000

3200

31894

29194

457

▽RL-9.500

▽RL-54.400

457 11000

1500

2200500

P6


5922

▽RL+22.394

3500

RL 0.000

RL +5.000

75000

W

P7

3200

1500

7505000750

1500

11000

2X4000

=8000

1500

1500

11000

2X4000

=8000

87000

3200

P7

▽RL-54.400

11000457 457


▽RL-9.500

5922

1500

29763

3500

2200500

27063

▽RL+20.263

750

5000

750

P8

1500

3200

1500

1500

2X4000

=8000

11000

1500

2X4000

=8000

11000

87000

3200

▽RL-9.500

▽RL-50.400

P8

φ1.5m N=9 L=41.0mCAST-IN-SITU RC PILE

5922

27153

24653

500

1500

2000

3500

457 11000 457

▽RL+17.653

P9

3200

1500

1500

11000

2X4000

=8000

1500

1500

11000

2X4000

=8000

7505000750

87000

22043

24543

3200

▽RL-52.400

2000

1500

P9

457457 11000

▽RL-9.500

500

3500

5922

φ1.5m N=9 L=43.0mCAST-IN-SITU RC PILE

▽RL+15.043

RL 0.000

P10

2700

1500

2X4000

=8000

11000

1500

87000

11000

15002X4000

=8000

1500

5000

750

780

17433

14933

▽RL-5.000

100 11000 100

P10

5922

▽RL+12.433

3500

2700


▽RL-44.900

500

485002000

2501500 250

7000

1500 4000 1500

7000

1500

40001500

P11

1007000100

P11

2422

1140

▽RL-0.500

10700

14700

500

1500

▽RL-35.500

1500

10001000

M F

1500

100 7000

P12

▽RL-0.5001500

1000

1000

500

15080

11080

M F

100

P12

15001500 4000

7000

CAST-IN-SITURC PILEφ1.5m N=4 L=35m

▽RL-38.000

8000

4000

M


▽RL+5.900

7000

4000 1500

A2

1500

i=12.0

25000 25000

930000

930000

87000 87000 87000 87000 87000 48500 25000 25000

0 160 43420 43420 160 43420 43420 160 43420 43420 160 43420 43440 120 43440 48470 60 24950 40 24960 40

350242403503602424035047048000

2022

2022

2022

2022

2022

1472

28

29

31

30

32

33

34

35

36

37

28

29

30

31

32

33

34

35

36

37

28.506

27.756

26.350

24

23.350

21.850

20.350

18.850

17.350

15.850

A2

+15.000

RL+5.900RL+3.100

15.400

+40.000

RL-0.500RL+3.500

16.150

P12

RL+3.500

RL-0.500

+15.000

P11

16.900

18.355

+16.500

RL-5.000RL-0.500

P10

RL-6.000

RL-9.500

+29.500

P9

20.965

RL-7.000

RL-9.500

+42.500

P8

23.575

RL-6.000

+5.500

RL-9.500

26.185

P7

RL-5.500

+18.500

P6

RL-9.500

28.376

+25.000

28.600

31.100

27.100

i=3.000%

i=12.0

100 7000 100

A2

PROFILE

PLAN

（航路） 18000

A2P12P11P10

P9P8P7P6

To Chittagong


8-8

Figure 8.2.2 General View of Existing Meghna Bridge

PIERP12

800 7200

9200

11200

2@4000=8000

2150

9200

580

0

250

1800

3500

800

1950150

9200

1108

0

1508

0

▽RL-0.500

Φ1,5m,LENGTH:P12=35mCAST-IN-SITU R.C.PILE

500

150

0

100

200

▽RL+14.580

192

100

0100

0

4000

4000

7000

▽RL+5.100

5001000

1500

▽RL+0.620

▽RL+3.500

1000

1500

500

72001000

1200

135

0▽RL+6.990

1000

1600

▽RL-5.000

SHW▽RL+5.100

HWL▽RL+6.990

▽RL-2.500

▽RL+0.628

288

030

06498

LENGTH=55.0m,NOS=4CAST-IN-SITU R.C.PILE Φ1,500

1500

100

11178

200

▽RL+5.900

11000

9200

5200

ABUTMENT

2000

100

A1

100

2000

9200

7200

▽RL+16.900

1000

▽RL+17.078

1000 200

2550

1200

1350

1500

1050

100

9200

8800 200

800

150

900

i 2%

300

120

800

i 1%

300

7200

350

PC T GIRDER

4X1850=7400

150 1500

500

AT PIER

900200

600

AT CENTER

ASPHALT CONCRETE PAVEMENT

200

CL

ADJUSTING CONCREETE

1200

250

200

5000 1950 150

14933

1743

3

2000

200

100

1600

P1 PIER

CAST-IN-SITU R.C.PILEΦ1,5m,LENGTH:48m

500

6700 2150

▽RL+0.880

5800

1200

200800

▽RL+12.433

PC BOY GIRDERAT PIER AT ABUTMENT

1200

2300

250

250

300

2.0%

800

2.0%

300 50

300

70

7200

1300

140

60

100

600

5001000100

800

100

1950

400

300

100

500

750

600300

550


ADJUSTING CONCREETE

LC

200

CROSS SECTION

SECTION


Final Report

8-9

8.2.3 Existing Gumti Bridge

Basic data of existing Gumti Bridge are shown in Table 8.2.3.

Table 8.2.3 Basic Data of Existing Gumti Bridge

Bridge Existing Gumti Bridge

Consultant Pacific Consultants International in consortium with Nippon Koei Co., Ltd.


Period of construction March 1992 to February 1996

River Meghna River and Gumti River

Overall length 1410 m (52.5 m + 15x87.0 m + 52.5 m)

Overall width 9.2 m (7.2 m (road) + 2×1.0 m (Sidewalk +Railing)

Superstructure Pre-stressed concrete box girder, continuous rigid frame type


Bridge components


Abutment: RC pile (φ1500) Pier: RC pile (φ1500)

Construction method Balanced cantilever erection

Live load AASHOTO HS20-44 ASD

Seismic load Horizontal load coefficient taken as 0.05

Wind load Without live load (V=150 MPH): 0.513 T/m2 With live load (V=100 MPH): 0.244 T/ m2

Loads

Thermal force Temperature range: 26 °C±17 °C

Concrete

Cylinder compressive strength at 28 days Pier, Abutment, Pile cap: 240 kgf/cm2 PC box girder, PC T beam, PC slab: 350 kgf/cm2 RC pile: 300kgf/cm2

Reinforcing bar Tensile strength: 4,950 kgf/cm2 Yield stress: 3,000 kgf/cm2 Allowable stress: 2,100kgf/cm2

Materials

Prestressing steel

SWPR7A (12T12.4) SWPR19 (1T19.3) SWPR19 (1T21.8) SBPR 95/110 (φ32).

TH

E K

AN

CH

PU

R, M

EG

HN

A, G

UM

TI 2N

D B

RID

GE

S C

ON

ST

RU

CT

ION

A

ND

EX

IST

ING

BR

IDG

ES

RE

HA

BILIT

AT

ION

PR

OJE

CT

F

inal Report

8-10

9000

7200

300

A1

▽RL-62.195

M

2422

▽RL+3.705

φ1.5m N=5 L=66.0mCAST IN SITU RC PILE

-70.000

-50.000

-60.000

-30.000

-40.000

-20.000

-10.000

10.000

0.000

20.000

N

1500

7500

22501500

14

1500

A1

9200

1500

3100

3100

1500

2250

52500

10500

1500

3750

3750

1500

10500

15003750

3750 1500

4900

15001500 3750

10500

15003750 3750

1500

10500

4900

3750

87000

10500

SEAL CONCRETE


▽RL-2.500 12358

8358

2500

1500

5922

▽RL-65.400

P1

P1 P2

16957

20957

15002500▽RL-8.500

10500

φ1.5m N=8 L=59.5m

▽RL-67.900

CAST IN SITU RC PILE

5922P2

N

3750

4900

10500

37501500 1500

P3

10500

1500

3750

3750

1500

87000

10500

▽RL-8.500

22903

18903

CAST IN SITU RC PILEφ1.5m N=8 L=65.0m

▽RL-73.400

15002500

5922P3

15001500 3750

10500

P4

15003750 3750

1500

10500

4900

3750

87000


19828

23828

▽RL-8.500

▽RL-72.900

2500

1500

10500

5922P4

24100

20100


▽RL-76.900

10500

▽RL-8.500

15002500

5922

P5

10500

37501500 1500

P5

3750

4900

10500

1500

3750

3750

1500

87000

MG 9

15001500 3750

10500

15003750 3750

1500

10500

P6

4900

3750

87000

20361

24361

▽RL-74.400

2500

1500▽RL-8.500

10500

5922

P6


5922

▽RL-70.900

10500

▽RL-6.500

22622

2500

1500


18622

P7

P7

4900

375015003750

10500

1500

1500

15003750 3750

10500

87000

P8

1500

1500

10500

3750 15003750

4900

10500

3750

3750

1500

87000

5922

▽RL-2.500

▽RL-70.400


18380

2500

1000

10500

14880

P8

▽RL-2.500

1500

87000

1410000

DL=-80.000

52500 87000 87000 87000 87000 87000 87000 87000 87000

BRIDGE LENGTH L=1410000m

52440

60 420 52020

43440 120 43440 43440 120 43440 43440 120 43440 43440 120 86880 120 43440 43440 120 43440 43440 120 43440 43440 120 43440

1900 1900

1900

1900

1900

1900

1900

1900

DISTANCE

GROUNO HEIGHT

PROPOSED HEIGHT

STATION

GRADIENT

14

10.905

13.905

A1

+10

12.705

14.280

15.405

18.133

19.036

19.601

19.841

19.991

20.141

20.291

20.441

20.591

20.741

20.865

20.915

i=600

i=600

VCL = 200 R = 7400 VCL = 200 15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

700.000

2.25

12.405

2.62

750.000

760.000

i=3.0%

L=416.660

800.000

2.15

P1

812.500

5.60

5.60

2.40

-2.50

-4.80

-5.80

-5.80

-5.60

850.000

P2

899.500

900.000

-5.60

16.879

16.893

950.000

-5.60

-6.00

P3

986.500

18.825

-6.00

19.500

1000.000

1050.000

1073.500

P4

19.750

-6.00

1100.000

-6.00

-5.80

1150.000

-5.70

1160.500

P5

20.022

-5.30

-5.00

1200.000

-4.80

1250.000

1247.500

P6

20.283

-4.65

-4.40

1300.000

-3.60

1350.000

-2.60

1334.500

20.544

-3.10

P7

1400.000

-0.40

1421.500

P8

20.802

-0.20

1450.000

1.99

2.34

L=522.000

i=3.0%

2.95

2.67

3.31

1500.000

MEGHNA RIVER

N N N N N

N N N

PROFILE

PLAN

（航路）75000

7500

To Dhaka

TH

E K

AN

CH

PU

R, M

EG

HN

A, G

UM

TI 2N

D B

RID

GE

S C

ON

ST

RU

CT

ION

A

ND

EX

IST

ING

BR

IDG

ES

RE

HA

BILIT

AT

ION

PR

OJE

CT

F

inal Report

8-11

CAST IN SITU RC PILEφ1.5m N=8

5922

▽RL-72.400

10500

15025

0014994

17644

▽RL-2.500

P9

P9

4900

375015003750

10500

1500

1500

15003750 37

50

1050

0

70.0m75.0m

CHAR LAND

N=4 L=70.0m

N=4 L=75.0m

▽RL-77.400

5922

▽RL-69.900

1753

0

14880

15025

00


10500

-SH WL =+5.25

▽RL-2.500

P10

P10

1050

0

1500

1500

10500

3750 15003750

4900

3750

3750

1500

87000

P11

15003750 37

50

1500

1500

1050

0

4900

37503750

10500

1500

87000

5922

14622

1812

2

2500

1000

10500

▽RL-2.500

▽RL-67.400


P11

5922

▽RL-67.400

▽RL-2.500

1000

10500


17861

14361

2500

P12

P12

1500

10500

37503750

4900

1500

1500

1050

0

3750

3750

1500

87000

P13

1500

1500

4900

37503750

10500

1500

15003750 37

50

1050

0

87000

5922

▽RL-67.400


10500

1500

1610

0

20100

2500

▽RL-4.500

P13

5922

21828


▽RL-68.400

1500

2500

10500

▽RL-6.500

17828

P14

P14

1500

10500

37503750

4900

1500

1500

1050

0

3750

3750

1500

87000

5922

▽RL-66.900

1690

3

20903

2500

1500▽RL-6.500

10500


P15

P15

15003750 37

50

1050

0

1500

1500

4900

37503750

10500

1500

87000

GUMTI RIVER

P16

10500

▽RL-4.500

5922

▽RL-68.900

16951

1500

2500


12951

1500

10500

37503750

4900

P16

1500

1500

1050

0

3750

3750

1500

87000 52500

9200

1500

3100

3100

1500

150022502250

7500

1500

A2

300

7500

1500

1100

0

9200

▽RL-61.585


M

▽RL+4.315

1900

87000 87000 87000 87000 87000 87000 87000 52500

00m

43440 43440 120 43440 43440 120 43440 43440 120 43440 43440 120 43440 43440 120 43440 43440 120 43440 43440 120 43440 52500

1900

1900

1900

1900

1900

1900

1900

20.915

20.891

20.462

20.791

VCL = 200 R = 34000 VCL = 200 R = 7400

30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

2.67

3.31

1500

.000

1508

.500

P920.916

3.10

21.066

2.25

2.28

2.79

2.66

1550

.000

1.93

2.23

1.17

1600

.000

1595

.500

P10

20.802

1.75

1.78

2.17

1650

.000

1700

.000

20.492

2.23

2.69

1682

.500

P11

20.544

2.65

2.58

3.12

1750

.000

20.342

2.79

1769

.500

P12

20.283

2.77

i=0.3%L=522.000

2.77

2.84

2.60

1800

.000

20.192

1850

.000

20.042

2.37

1.30

1856

.500

P13

20.022

1.20

1.00

1900

.000

19.892

0.00

-1.10

1943

.500

P14

19.750

-1.20

-1.30

1950

.000

19.716

2000

.000

19.266

-1.20

2030

.500

P15

18.825

-1.30

19.500

2050

.000

18.748

2100

.000

17.352

-1.40

2117

.500

P16

16.879

0.20

0.50

2150

.000

15.915

1.88

2.34

3.54

3.95

2170

.000

15.315

A2+20

2200

.000

14.415

4.10

4.21

4.16

4.06

5.47

2250

.000

12.915

2300

000

11415

i=3.0%L=432.300

4.14

4.08

4.12

5.48

STONE DAUDKANDI

A2

N N N

N N

N N

N

N

ILE

To Chittagong


8-12

Figure 8.2.3 General View of Existing Gumti Bridge

1501950150 1950 5000

ADJUSTING CONCRETE


7200

9200

300

800

2.0%

200

CL

1500300

800

250

2.0%

250

2300

200

42250

72300

140050

1800

50

400100

300600

AT ABUTMENT

200

250

250

1900

1400

150

1500300

800

622

500

7250

300

800 7200

50001950150 1950

2.0% 2.0%

AT CENTER

9200

200

CL


ADJUSTING CONCRETE

50

150 960 960150

100 400 100 800

300

100

600

100

200

250

250

5800

5300

150

1500300

800

422

300

7250

300

800 7200

500

5000

50

1950150

50

1950

2.0% 2.0%

AT PIER

9200

200

CL


ADJUSTING CONCRETE

500

1400

300

100

800

1000

500

600

100

100

110

00

11178

2878

ABUTMENT

1500

6500

300

1500

A1

1500 3100

9200

CAST IN SITU PILEφ1.5m N=6 L=66.0m

▽RL+1.705

10001000

▽RL+12.703

7200

9200

▽RL+12.883

3100

3750 3750

10500

1500 1500

PIERP6

4900

▽RL+20.283

7200

9200

2800

▽S W WL RL+5.250

1000

5800

7000

2800

20361

1500

2500

φ1.5m N=8, L=66.0mCAST IN SITU RC PILE

▽RL-10.00

1000

▽RL+14.361

1500

1000

123

61

CROSS SECTION

1000

9200

72001000

▽RL+14.280

1500

5800

▽RL+8.358

8358

2500

1500

2800 4900 2800

▽RL-4.000

10500

1500 3750 3750 1500

CAST-IN-SITU RC PILEφ1.5m N=8, L=63.0m

7358

1000

▽S W WL RL+5.250

P1 PIER

SECTION


Final Report

8-13

8.3 Scope of the Retrofitting and Rehabilitation Works

8.3.1 Observation of the Damages

As shown in detail in 2.5.1 the damages to the three bridges have been observerd as follows;

Table 8.3.1 Observation of the Damages (Structures)

Kanchpur Meghna Gumti

Sub-structure Cracks and water leakage Cracks Small dents No rebar deteriorations.

Cracks Water leakage Small dents No rebar deterioration.

Girders & Cross beams

No visible cracks. Rebar exposures Cracks over 0.2 mm Water leakage

Deck slab No visible cracks. A crack over 0.2 mm width with small amount of isolated lime

No visible cracks.

State Normal Normal Normal

Causes of Deterioration

Aging Aging Aging

Table 8.3.2 Observation of the Damages (Accessories)

Kanchpur Meghna Gumti Expansion

joints Damaged. Damaged.

Damaged.

Hinges N/A Damaged.

State Serious Serious Serious

Possible causes of damages

Overloaded trucks Insufficient maintenance




8-14

8.3.2 Scope of the Retrofitting and Rehabilitation Works

From the above mentioned background the scope of the rehabilitation works shall be defined

as the repair works for the damaged expansion joints in Kanchpur Bridge, Meghna Bridge

and Gumti Bridge and the repair works for the damaged hinges in Meghna Bridge and Gumti

Bridge.

The retofitting works shall be defined as the works to renew the bridge structures to conform

to the current bridge design standards and to cope with the current and future scouring

conditions. As mentioned in the previous chapter the changes of the design seismic force

should be reflected in all the bridges and the changes of the live load should be reflected in

Kanchpur Bridge.

The repair works for the damaged hinges shall be connecting two cantilever girders to be

monolithic, eliminating the hinge and expansion joint at each hinge section. As the hinge

section shall remain in every 5 or 6 spans to avoid excessive restraint forces from being

generated by the temperature change, the hinges and expansion joints at such sections shall

be replaced by new ones.

To prevent the bridge from collapsing during earthquake the steel brackets will be attached to

the substructures at the girder ends. At the halving joint of Kanchpur Bridge the girder ends

are connected to each other.

Consequently, the scope of the retrofitting and rehabilitation works for Kanchpur Bridge,

Meghna Bridge and Gumti Bridge are summarized below.

Table 8.3.3 Scope of the Rehabilitation and Retrofitting Works


Repair of cracks/rebar exposures ○ ○ ○

Connecting girders (eliminating hinges/joints) - ○ ○

Center hinge rehabilitation - ○ ○ Repair

Expansion joint replacement ○ ○ ○

Steel brackets on the substructures ○ ○ ○

Fail-safe connection ○ - -

Deck strengthening ○ - -

RC-lining ○ ○ ○ Piers

Diaphragm wall ○ - -

Pile cap integration P1, P3, P5, P6 P1 to P10 P1 to P8

Steel pipe sheet piles P1 to P6 P3 to P10 P1 to P8

Retrofit

Foundations

Bored RC piles - P1, P2 -


Final Report

8-15

8.4 Loads Applied in the Original Design and to be Applied in the Current Design

The difference between the original design standards and the current design standards is

found to be changes in magnitude of;

Earthquake loads

Live loads

8.4.1 Earthquake Loads

According the existing records (as-built drawings and design calculation report of existing

Meghna and Gumti Bridges), it is found that the seismic acceleration coefficient of 0.05 was

used to calculate the horizontal seismic forces. But, that value according to BNBC (2006) has

been increased to 0.15, which results in increasing the coefficient of response of spectral

acceleration to 0.08~0.33. Therefore, it may necessitate revising the original design of the

existing bridges.

Figure 8.4.1 Seismic Zoning Map of Bangladesh

Legend

Border

River and Lake

Acceleration zone (0.25)

Acceleration zone (0.15)

Kanchpur Bridge

Meghna Bridge

Gumti Bridge


8-16

Due to the change of the seismic acceleration coefficient, the magnitude of the horizontal

seismic force will be increased to 1.6~6.6 times the original seismic force.

Table 8.4.1 Horizontal Seismic Coefficient

Figure 8.4.2 Earthquake Load Application

8.4.2 Live load Combination

As is mentioned in Chapter 6, special consideration will be given to the design of the floor

slab system due to accommodating the heavily loaded trucks. Accordingly, the live load

combination from Japanese standards B-type live load will be followed, while the live load

combination from AASHTO HS20-44 will be followed for girder design.

(1) Slab design

The restoration design by reverse analysis method shall be followed particularly for the

existing Kanchpur Bridge. This is due to lack of information and no as-built drawings

available. The floor slab design is recovered by restoration method applying the AASHTO

ASD based HS20-44 live load. The computed results hereinafter are referred to as the

11200

2@4000=8000

2150

1600

14933

17433

2000

200

100

1600


500

6700 2150

5800

1200

H Original design standard

H=0.05 V

Current standard

H=0.08～0.33 V

H

Original design standard (1) Current standard (2) (2) / (1)

0.05 0.08～0.33 1.6～6.6


Final Report

8-17

capacity of the existing Kanchpur Bridge considering the bridge time span from construction.

On the other hand, the results computed with B-type live loads are considered as the

requirements for the exiting bridges. However, the rehabilitation plan along with retrofitting

is finalized based on these two results.

Furthermore, the retrofitting plan for the floor slab system of the existing Meghna and Gumti

Bridges is finalized considering the B-type live loads.

Table 8.4.2 Live Loads for Slab Design

(a) AASHTO HS20-44 truck load (b) JRA B-type truck load

Figure 8.4.3 Truck Live Load Comparison

(2) Girder design

The differences in lane live loads, based on different AASHTO versions, are mainly focused

on their magnitude, which are shown in Table 8.4.3 side by side. The lane load specification

corresponding to AASHTO LRFD HS20-44 will be used for retrofitting of the existing bridge

girders.

Original design standard

(AASHTO HS20-44 ASD) Current standard

(Japanese standard B-type live load)

Truck Wheel Load

72 kN 100 kN

Load applica-

tion

72kNSlab

Transverse direction

100kN

Slab



Tire area

Unit: mm


8-18

Table 8.4.3 Live Loads for Girder Design

Figure 8.4.4 Live Loads (AASHTO HS20-44)

※1: Live load for moment calculation

※2: Live load for shear calculation


(AASHTO ASD, HS20-44) Current standard

(AASHTO LRFD, HS20-44)

Live loads Concentrated load: 208 kN ※1 or 302 kN※2

(4 Lanes) Uniform load: 24 kN/m (4 Lanes)

Concentrated load: 845 kN (4 Lanes) Uniform load: 24 kN/m (4 Lanes)

Load applicat-

ion

24kN/ 208kN or 302kN

Girder

Longitudinal direction

24kN/845kN

Girder



Final Report

8-19

8.5 Kanchpur Bridge

8.5.1 Evaluation and Recommendations for Slab Design

As is also discussed in the previous section, the slab strength of the existing Kanchpur Bridge

shall be assessed by applying the restoration design concept. Then, the strength assessment in

both longitudinal and transverse directions is compared with the allowable stress

recommended by JRA. It can be found that the slab strength retained does not meet the

allowable criteria when subjected to current design standards.

Table 8.5.1 Slab Strength Evaluation

Table 8.5.2 Retrofitting Method for Slabs

Center span Support Center span

- kN・m 13.80 -25.24 8.25 -

Concrete 8.0 N/mm2 4.41 7.12 3.75 OK

Reinforcement 165 N/mm2 128.00 155.30 138.50 OK

- kN・m 19.42 -38.61 13.43 -

Concrete 8.0 N/mm2 6.20 10.88 6.10 OUT

Reinforcement 165 N/mm2 180.10 237.60 225.50 OUT

CheckUnitAllowable

Stress

Stress

Moment

Moment


Current standard

Transversedirection

Longitudinaldirection

D13ctc250 (assumed) D16ctc150 (assumed)

180

30

30

D13ctc250 (assumed) D13ctc150 (assumed)


◎ △ ◎

△ △ △

Construction period ◎ △ ◎

Legend: ◎excellent, ○good, △poor

1.111.11

Need traffic restriction

(Overlay and waterproof) (waterproof)

A little

(Upward construction)

Weight is increasedGirder, pier and foundation need retrofittingabout slab retrofitting

Weight is increasedGirder, pier and foundation need retrofittingabout slab retrofitting

△

△△

Long

Need scaffolding

Better

Need traffic restriction

○◎

Many

Evaluation

Image

ConstructabilityConstruction

Traffic restriction

Cost

Crack rehabilitation

Feature

Record of usage

C plan:Carbon fiber

Many

Short

Need scaffolding

Best

(Downward construction)

B plan: Overlay method on the under of slabA plan: Overlay method on the top of slab

Better○

(Upward construction)

Need scaffolding

◎

◎

Crack width under 0.2mm shall be coated

Crack width over 0.2mm shall be crack grout△

1.00

No weight increase ◎△

△ △

Crack rehabilitation isn't required ◎△

Short

traffic restriction isn't required◎

Crack width under 0.2mm shall be coated

Crack width over 0.2mm shall be crack grout

△△

Existing slab

Additional slab(100mm)

Pavement

Existing slab

Additional slab(70mm)

Pavement


8-20

8.5.2 Evaluation and Recommendations for PC Girder Design

Based on the original design standards, the arrangement and profile of PC-bars are decided

from the restoration design. Then, the computed results are compared with the results

computed by current design standards specification in Table 8.5.3 - Table 8.5.4. It shows that

the capacity of the PC-girder does not meet the requirements as per current design standards.

Therefore, it requires retrofitting /additional reinforcement. On the other hand, PRC girder

seems to be quite safe under current design standards and thereby, no further retrofitting is

necessary.

Table 8.5.3 Restoration Design of PC Girder Based on Original Design Standards

Table 8.5.4 State of Strength of PC-Girder

Unit Allowable Results Check Remarks

N/mm2 0.00<σ<12.5 3.82 OKN/mm2 -1.35<σ<12.5 1.32 OKN/mm2 -1.35<σ<14.3 1.57 OK

Ultimate moment Mu kNm - 17213 -Moment capacity Mr kNm - 22846 -

Mr/Mu - F>1.0 1.33 OK

N/mm2 σi>-0.9 -0.05 OKN/mm2 σi>-1.85 -0.16 OK

Ultimate share Sh kN - 1299 -Crushing capacity Suc kN - 2405 -

Suc/Sh - F>1.0 1.85 OK

Moment Center span

SWPR7A 12S12.4-6PC bar

From girder end to 4.6m

Compound stress due to

Flexural safety

Live loadDead load

Shear

Diagonal tensile stress due to

Web crushing capacity

Temperature load

Live loadDead load

Moment checkShear check

Unit Allowable Results Check Remarks

N/mm2 0.00<σ<12.5 3.82 OKN/mm2 -1.35<σ<12.5 -1.45 OUTN/mm2 -1.55<σ<14.3 -1.21 OK

Ultimate moment Mu kNm - 20816 -Moment capacity Mr kNm - 22846 -

Mr/Mu - F>1.0 1.10 OK

N/mm2 σi>-0.9 -0.05 OKN/mm2 σi>-1.85 -0.35 OK

Ultimate share Sh kN - 1581 -Crushing capacity Suc kN - 2405 -

Suc/Sh - F>1.0 1.52 OK

From girder end to 4.6mShear

Diagonal tensile stress due to

Web crushing capacity

Dead loadLive load

Center span

Live loadTemperature load

Compound stress due to

Flexural safety

Dead load

PC bar SWPR7A 12S12.4-6

Moment

Moment checkShear check


Final Report

8-21

Table 8.5.5 State of Strength of PRC-Girder

There are two cantilever sections in the span between pier P5 and P6. It is found from the

survey results that these cantilever sections are not severely damaged and the existing traffic

can easily move over these cantilever sections without any hindrance. Therefore, it is planned

not to rehabilitate and leave them unchanged.

8.5.3 Evaluation and Recommendations for Pier Design

In order to assess the state of strength of the bridge piers, the pier P5 is analyzed with the

seismic loading specified by the original and current design standards. From the computed

results, it can be seen that pier P5 does not meet the requirements for its resistance capacity.

Therefore, it will lose its resistance capacity when subjected to strong earthquake excitation.

Table 8.5.6 State of Strength of Pier P5

It is necessary to increase the strength of the existing bridge piers so that they can withstand

strong seismic excitation. Accordingly, the JICA study team adopted three plans;

ReinforcementUnit Results Check

Compound stress Live load N/mm2 -1.45 -N 99180 -

N/mm2 200.00 -mm2 495.90 -mm2 506.80 -

F>1.0 - 1.02 OK

Tensile force

Available reinforcementReinforcement requiredAllowable tensile stress

SD390-4

600

150 150 150 150

69 210 43 210 69

250

240

90

120

120

120

50

180

PC鋼材　6-12φ12.4

D13

PC bar

Moment kNm 18420 17434 OUT

Shear kN 1290 1838 OK0.081.89


CheckCapacityDemandSpectral

accelerationcoefficient

Periodictime

Unit

1600

838

16762057

3429 3429

2057

1676

143

12534

15115

2438

15550

68584346 4346

1573572

12534

15115

2581

2065

4923

φ6510


8-22

A-plan: RC-lining + Wall

B-plan: Steel plate lining

C-Plan: Polymer mortar lining

A comparative study of the four plans with their construction cost is shown in Table 8.4.7.

From this comparison, the JICA study team recommends that the A-plan (RC-lining + Wall)

is most preferable for seismic retrofitting of the existing Kanchpur Bridge piers. This is due

to the least construction cost.

TH

E K

AN

CH

PU

R, M

EG

HN

A, G

UM

TI 2N

D B

RID

GE

S C

ON

ST

RU

CT

ION

A

ND

EX

IST

ING

BR

IDG

ES

RE

HA

BILIT

AT

ION

PR

OJE

CT

F

inal Report

8-23

Table 8.5.7 Seismic Retrofitting of Existing Bridge Piers

Record of usage ◎ ○ △

△ △ △

Construction period △ ◎ △

Painting ◎ △ ◎

Inspection ◎ △ ◎


△

◎

(No space in the wall)

Poor Poor

(No space in the wall)

Poor

Structural performance

Constructability

Maintenance

Long

Extra provision No need protection from heavier floating bodies

Many

◎

△(No space in the wall)

Need cofferdam

Need No need

Need cofferdam

Short

Cost ◎ △1.491.261.00

Evaluation

A plan: RC lining + Wall

Easy

◎

Image

Landscape △

B plan: Steel plate lining C plan: polymer mortar lining

◎ △

△Need protection from heavier floating bodies◎No need protection from heavier floating bodies

DifficultConstruction

No need

Need cofferdam

Easy

△

Few

○

○

Not so many

Difficult

Long

Easy

Easy

Effect on acquaticenvironment

Good ◎ ◎Good ◎ Good

Anchor

14324

1600

838

1758 3429 3429 1758

2145

1253

4

2565

2065

250

250

1573572

286 2502145

250

250 286

250

Existing pier

100 150

a part

A-A

250

100 150

286

A A

a

500

Wall

Anchor

Existing pier

a part

14324

1600

838

1758 3429 3429 1758

2145

1511

5

2137

2065

36

36

1573572

41 362145

36

36 41

A-A

36

306

41

36

30 6

Steel

Less-shrinkage

Concrete

A A

a

36

500

Wall

mortar t=30mm

Anchor

Existing pier

a part

14324

1600

838

1758 3429 3429 1758

2145

1511

5

2181

2065

5858

1573572

66 582145

58

58 66

A-A

58

66

58

58

A A

a

500

Wall


8-24

8.5.4 Evaluation and Recommendations for Foundation Design

As per the original design standards, the capacity of the existing bridge pier foundation is

assessed by applying the restoration design concept. Then, the computed results are compared

with the results computed by the current design specifications in Table 8.5.8. The current

design specifications consider the seismic force as per BNBC along with the higher scouring

level that is expected. It shows that the capacity of the foundation corresponding to pier P5

does not meet the requirements as per current design standards. Therefore, it requires

retrofitting /additional reinforcement.

Table 8.5.8 State of Strength of Foundation Corresponding to Pier P5

Displacement mm 29 50 OK

Subgrade shearing action kN 7707 8292 OK

Displacement mm 92 50 OUT

Subgrade shearing action kN 7967 5860 OUT

OUT637833kN/m2Subgrade reactionin axial direction

Subgrade reactionin axial direction



OUT7341894kN/m2

0.151.89

0.150.89

Demand Capacity CheckUnitPeriodic

time

Spectralaccelerationcoefficient

11150

2070

15550

6510

1740

1740

4350 3430 3430 4350

Caisson foundation（φ15.550mx6.510m L=28.956m）

1570570

15120

28960

▽RL+1.000

Design scouring depth RL=-15.00

H.W.L ▽RL+5.000

3000

Projected length 16000

4000


Final Report

8-25

Based on the above results, it is necessary to increase the strength of the foundation for the

existing bridge piers so that they can withstand strong seismic excitation. Accordingly, the

JICA study team has adopted two plans;

A-plan: Steel Pipe Sheet Pile

B-plan: Additional RC-Pile

A comparative study of the two alternative plans highlighting their construction cost and

scouring effect on the river bed is shown in Table 8.5.9. From this comparison, the JICA

study team recommends that the A-plan (Steel Pipe Sheet Pile) is the most preferable option

for retrofitting of the existing Kanchpur Bridge pier foundations. This is due to the least

construction cost and small scouring effect on the river bed.

Table 8.5.9 Foundation Retrofitting

SP

Plan A: SPSP Plan B: RC pile

Image

Foundation size Small Large

Not requiredCofferdam

Evaluation ◎

Cost 1.921.00

RL=+16.115

15120

1322 436

14640

28960

Dc1

Dm2

As

▽RL+1.000

800

S.H.W.L ▽RL+5.08

Protected height 19010

4500

13990

4648

18400

15300

2.0％

16200

2.0％

155504545 1500 7000 1500

10000

14324

1000 1596

H.H.W.L ▽RL+6.37

Retrofitted wall1000 4858 1000

Scouring RL=-18.01

9950

3000

Supporting layer

New bridgeExisting bridge

P5

RC LINING

500

River bed

34940

14640

11150

2065

15550

9980

4540

13730

3000

Retrofitted wall

10000 2720

4120

4110

11230

56205620

2120

2360

6510

2360

11230

2360

2360

1000

17320

Steel pipe sheet pile

φ1000 L=37.5

3000

6510

5×3750=18750

21750

9×3750=33750

1500

1500

1500 1500

36750

15550

10000

10980

99207400

￡

7620

7620

17320 8450

CAST-IN-SITU R.C.PILE

Φ1,5m,n=52,LENGTH:30.5m

1500

36750

18400

15300

2.0％

3100 3100

2.0％

2060 10000

▽RL-2.000

H.H.W.L ▽RL+6.37

Supporting layer

P5

S.H.W.L ▽RL+5.08

500

River bed

1600

838

4346 3429 3429 4346

1676 2057 3429 3429 1790 1943

143

Caisson

φ15.550mx6.510m L=28.956m

1573 572

4350 3430 3430 4350

Caisson

（φ15.550mx6.510m L=28.956m）

14620

14640

Dc1

Dm2

▽RL+1.000

Scouring RL=-18.01

800

3000


3500

13990

4650

RC LINING

New bridgeExisting bridge


8-26

8.5.5 Evaluation and Recommendations for Work to prevent the Bridge from collapsing

The end of the girder must be constructed in a way of preventing bridge from collapsing. The

following are options for such prevention works. In the case of the halving joints section C

plan will be recommended.

A plan: Steel brackets

Steel brackets are attached to the pedestal so as to ensure the foolproof length for

preventing the girder’s falling off the pedestal

B plan: Additional pedestal

Pedestal is extended so as to ensure the foolproof length for preventing the girder’s falling

off the pedestal

C plan: Fail-safe connection

Ends of the adjacent girders are connected by PC bars for preventing the girder’s falling

off the pedestal

Table 8.5.10 Prevention Work above the Substructure to prevent bridge collapse

◎ ◎ ◎

○ ○ ○

△ △ △


△

Nomal Nomal

△Not good Not goodNot good

Nomal

Need scaffolding

△

△

△

Nomal ○

1.62○

○

Connect the ends of the adjacent girders byPC bars so as to prevent the girder's fallingoff if the end of the girder deviates from thepedestal

C plan: Fail-safe connection

Many

Evaluation

Image

Aesthetic appearance

Cost

Maintenance

Structure

Record of usage

Constructability

B plan: Additional pedestalA plan: Steel brackets

Attach the steel bracket to the pedestal so asto ensure the foolproof length of the end ofthe girder against the girder's falling off thepedestal

Extend the pedestal so as to ensure thefoolproof length of the end of the girderagainst the girders falling off the pedestal

Many Many

○◎

Need scaffolding

Nomal

Need scaffolding

Nomal

◎1.00 1.07

○


Final Report

8-27

8.6 Meghna Bridge

8.6.1 Evaluation and Recommendations for Girder Design

The JICA study team assumed that the reduction in the number of expansion joints and

hinged shoes will increase the servicability of the existing bridges and reduce the maintenace

cost in the future. This can be achieved by connecting the simply supported girders into the

continuous girder at hinged sections. The computed results are shown in Figure 8.6.1.

Figure 8.6.1 Concept of Continuity in Meghna Bridge Girder

In order to reduce the number of expansion joints and hinges in the floor slab, the existing

cantilever box girder system is being planned to be continuous with a rigid frame at the

hinged sections. The lengths of the two continuous sections for Meghna Bridge are shown in

Figure 8.6.1. The lengths of the continuous sections is determined to meet the requirements

that the stress due to change of temperature shall be less than the stress generated from

horizontal earthquake excitation.

PC-continuous box girder (5.5-span) PC-continuous box girder (5.5-span)


8-28

In order to rehabilitate the central hinges of Meghna and Gumti bridges, the JICA Study

Team has considered three plans;

A plan: Entire change

B plan: Additional hinge

C plan: Partly change

Meghna bridge has one joint for this rehabilitation and the Gumti bridge has two joint for this

rehabilitation. Among the three plans, C plan is more preferable. This is due to the fact that it

is possible to manufacture and procure.

Table 8.6.1 Retrofitting by Center Hinge


Image

Procurement

Evaluation

Impossible to manufacture Impossible to manufacture

◎△△

C plan: Partly changeB plan: Addition at hingeA plan: Entire change

Possible to manufacture

All change

Change

Additional


Final Report

8-29


In order to assess the state of strength of the bridge pier, pier P8 is analyzed with the seismic

loading specified in the original and current design standards. From the computed results, it

can be seen that pier P8 does not meet the requirements for its resistance capacity. This state

of strength is similar to Kanchpur Bridge. Therefore, the Meghna Bridge pier will lose its

resistance capacity when subjected to strong earthquake excitation.

Table 8.6.2 Strength Check for Pier P8


Shear kN 12691 9923 OUT0.170.6


UnitPeriodic

time


Demand Capacity Check

750

5000

750

1500

3200

1500

1500

2X4000

=8000

11000

1500

2X4000

=8000

11000

11200

2@4000=8000

2150

1600

24653

27153

2000

200100

1600


500

6700 21505800

1200


8-30

Similar to Kanchpur Bridge, three of four plans are also considered for retrofitting of Meghna

Bridge pier.

A-plan: RC-lining



A comparative study of the three plans with their construction cost is shown in Table 8.6.3.

From this comparison, the JICA study team recommends that the A-plan (RC-lining) is most

preferable for seismic retrofitting of the existing Meghna Bridge piers. This is due to the least

construction cost.

Table 8.6.3 Retrofitting by Pier


◎ ◎ ◎


◎ ◎ ◎


◎Effect on acquaticenvironment

Good ◎ Good

△◎◎Extre provisionNo need protection from heavierfloating bodies

Need protection from heavier floatingbodies

No need protection from heavierfloating bodies

Easy ◎ ◎

△

C plan: Polymer mortar lining

Difficult △

Inspection

B plan: Steel sheet liningA plan: RC lining

Structual performance

Need cofferdam

Evaluation

Cost △

Constructability

Maintenance

No need

Easy

Good Good

Construction

Construction period

△△◎

○◎

Need cofferdam

Easy

Need cofferdam

LongLong ◎△

◎◎ △ EasyDifficult

Image

Landscape

No needNeed

Many Not so many Few

Short

1.00 1.84 2.34

Good

◎ Good

24653

500

5000

5800

750 750

6500276 276

5000750276

867 5318

3200

250

250

750 276

867

Anchor

250

Existing pier

100 150

A-A

a partA A

a

250

100 150

276

mortar t=30mm

8

24653

500

5000

5800

750 750

650042 42

500075042

768 5048

3200

38

38

750 42

768

A-A

A A

a

30

42

Anchor

38

Existing pier

30 8

Steel

Less-shrinkage

Concrete

a part

Existing pier

24653

500

5000

5800

750 750

6500276 276

500075087

787 5100

3200

79

79

750 87

787

A-A

A A

a

79

87

Anchor

79

a part

79


Final Report

8-31


Following a method similar to that stated above for Kanchpur Bridge, the capacity of the

Meghna Bridge foundations is verified under load specifications by current design standards.

The current design specification considers the seismic force as per BNBC along with the

higher scouring level that is expected. The decision is similar to Kanchpur Bridge. The

capacity of the foundation corresponding to pier P8 does not meet the requirements and

requires retrofitting /additional reinforcement.

Table 8.6.4 Strength Check for Foundation of Pier P8

Similarly, two retrofitting plans are also considered for Meghna Bridge foundation.



mm 65 15 OUT

Max kN 29149 26733 OUT

Min kN -21582 -21432 OUT

Moment Mmax kNm 71482 1920 OUT

mm 27 15 OUT

Max kN 16862 26733 OK

Min kN -6136 -21432 OK



Displacement

0.8 0.27

Axial force 0.330.6

Displacement


Axial force

Capacity CheckUnitPeriodic

time


Demand

3200

6500

11000

2@4000=8000

11000

2@4000=8000

11000

2@4000=8000

2150

▽RL-9.500

▽RL+5.00

24650

27150

2000

1500

1500

CAST-IN-SITU R.C.PILE

Φ1,5m,LENGTH:48m

500

5000

2250

5800

11910

750 750

6500

▽RL-33.00 Design scouring depth

Ds2

As


8-32

A comparative study of the two alternative plans highlighting with their construction cost and

scouring effect on the river bed was carried out as already seen in Table 7.3.1. From this

comparison, the JICA study team recommends that the A-plan (Steel Pipe Sheet Pile) is the

most preferable option for retrofitting of the existing Meghna Bridge pier foundations. This is

due to the least construction cost and small scouring effect on the river bed.

The comparison shown in Table 7.3.1 as described above was for the severe scouring zone.

In the cases of the shallow and medium scouring zones results of the comparison are as

shown in Table 8.6.5 and Table 8.6.6 Retrofitting the foundation, respectively. The piled

foundation is advantageous in the shallow scouring zone.

Table 8.6.5 Retrofitting the foundation

1.00 0.66


Small

Image

Evaluation ◎

Cost

Cofferdam Not required SP

Foundation size Small

1500

800

3950

17750

2.0％2.0％

23100

517

1000 13600 10001075 1075

S.H.W.L ▽RL+5.05

H.H.W.L ▽RL+6.31

3846

Existing bridgeNew bridge

2250 6500 2250

15600

14600

Ac

Dc

Ds2

▽RL+20.965

As

Scouring ▽RL-4.60

22043

6500

1475

CAST-IN-SITU RC PILEφ1500 L=44.00m n=9

3993011550

41950

Supporting layer

3000

1500

500


L=57.00m n=88

φ1000 SKY490 t=16mm

（Navigation clearance n=20）

2500

1500

▽RL-11.00

11550

500

500

74875368

Design level

57000

9200

11000

2@4000=80001500

▽RL-9.500

7505000750

3700

14600

3000

250

3725

7297

24956 74877487

14974

9200

6978

1987

1987

（Existing bridge width）

39930

11000

11000


φ1000 L=57.00m n=88

SKY490 t=16mm

Navigation clearance

n=20

9200

11000

2@4000=80001500

▽RL-9.500

1500

800

3950

17750

2.0％2.0％

23100

517

1000 13600 10001075 1075

S.H.W.L ▽RL+5.05

H.H.W.L ▽RL+6.31

3846


2250 6500 2250

15600

50014600

Ac

Dc

Ds2

▽RL+20.965

As

Scouring ▽RL-4.60

43900

22043

6500

2500

1500

▽RL-11.00

500

11550

11550

3000

1500

Supporting layer

1475

CAST-IN-SITU RC PILE

φ1500 L=44.00m n=9

CAST-IN-SITU RC PILEφ1500 L=44.00m n=12

27575

Design level

2700

7505000750

3000

372514600500 2250

250

7300 7300 3725 3250 3250 2250

5987 8288

13788 13788

1500

4000

4000

1500

11000

500

7800

2@4000=8000

27575

1500 3@4200=12600 1500

1100016575

3975

5500


Final Report

8-33

Table 8.6.6 Retrofitting the foundation

Evaluation ◎

Cost 1.00 1.07

Foundation size Small Large

Image


Cofferdam Not required SP

11000

2@4000=80001500

▽RL-9.500

1500

800

650

17750

2.0％2.0％

468

1000 13600 10001075 1075

H.H.W.L ▽RL+6.31

3846


2250 6500 2250

15600

5343 14600

Ac

Dc

Ds2

▽RL+28.316

As

2919430500

2700

1500

▽RL-11.00

11550

300


Scouring ▽RL-14.90

11550

35550

Supporting layer

3000

1500

1475

39930

7512

CAST-IN-SIUT RC PILE

φ1500 L=43.00m n=9

S.H.W.L ▽RL+5.05500

500

φ1000 SKY490 t=16mm

6500

（Navigation clearance n=20）

56000

9200

11000

2@4000=80001500

▽RL-9.500

2700

1500

800

1500

17750

2.0％2.0％

468

1000 13600 10001075 1075

S.H.W.L ▽RL+5.05

H.H.W.L ▽RL+6.31

3846


2250 6500 2250

▽RL-11.00

15600

14600


Ac

Dc

Ds2

▽RL+28.316

As

River bed

Scouring ▽RL-14.90

11050

37500

30000

Supporting layer

29194

11050

33500

800

3500

1500

37502675 1475

CAST=IN-SIUT RC PILE

φ1500 L=43.00m n=9

6500

CAST=IN-SIUT RC PILEφ1500 L=43.00m n=36


L=56.00m n=88

9200

7505000750

3700

14600

3000

250

3725

7297

24956 74877487

14974

9200

6978

1987

1987

（Existing bridge width）

39930

11000

11000


φ1000 L=56.00m n=88

SKY490 t=16mm

Navigation clearance

n=20

7505000750

3700

14600

3000

2@4000=8000 3750

33500

3750

250

2675 3725

2675 7300 3449 3526 57247300 3526

1500 5@3750=18750 1500

6775 7500

16750 16750

6000

9975 9250

1500

3750

4000

4000

3750

18500

1500

11000

3750

11000 375018750


8-34

8.6.4 Evaluation and Recommendations for Work to prevent Bridge collapse

The work to prevent bridge collapse that was already explained for Kanchpur Bridge in

subsection 8.5.5 will also be used for Meghna Bridge.

8.7 Gumti Bridge

8.7.1 Evaluation and Recommendations for Girder Design

Similar to Meghna Bridge, the number of expansion joints and hinged shoes will be

decreased in order to increase the serviceability of the existing bridges and reduce the

maintenance cost in the future. This can be achieved by connecting the simply supported

girders to become a continuous girder at the hinged sections. The computed results are shown

in Figure 8.7.1

Figure 8.7.1 Concept of Continuity in Gumti Bridge Girder

The concept to determine the length of the continuous section of Gumti Bridge is the same as

that used for Meghna Bridge. The existing cantilever system will be rehabilitated and

converted into three continuous box sections so that the number of expansion joints and

hinged shoes will be decreased and thereby increase its serviceability. The lengths of the

three continuous sections for Gumti Bridge are shown in Figure 8.7.1.

PC-continuous box girder (5.5-span) PC-continuous box girder (5.5-span)PC-continuous box girder (6-span)


Final Report

8-35

Meghna bridge has one joint for this rehabilitation and the Gumti bridge has two joint for this

rehabilitation.

Table 8.7.1 Retrofitting Center Hinge


A plan: Entire change B plan: Addition at hinge C plan: Partly change

Image

Procurement Impossible to manufacture Impossible to manufacture Possible to manufacture

Evaluation △ △ ◎

All change

Change

AdditionaAll change

Change

Additional


8-36


In order to assess the state of the strength of the bridge piers, pier P6 is analyzed with the

seismic loading specified in the original and current design standards. From the computed

results, it can be seen that pier P6 does not meet the requirements for its resistance capacity.

This state of strength is similar to Kanchpur and Meghna Bridges. Therefore, the Gumti

Bridge piers will lose their resistance capacity when subjected to strong earthquake excitation.

Table 8.7.2 Strength Check for Pier P6


Shear kN 12691 8587 OUT

Demand Capacity Check

0.170.6Longitudinal

direction

UnitPeriodic

time


2800

▽S W WL RL+5.250

1000

5800

7000

2800

20361

1500

2500

φ1.5m N=8, L=66.0mCAST IN SITU RC PILE

▽RL-10.00

1000▽RL+14.361

1500

1000

12361

10500

2@3750=7500

?4900

10500

3750 3750

10500

1500 1500

4900

▽RL+20.283

7200

9200


Final Report

8-37

Similar to Meghna Bridge, three plans are also considered for retrofitting of Gumti Bridge

piers.

A-plan: RC-lining



A comparative study among the three plans with their construction cost is shown in Table

8.7.3. From this comparison, the JICA study team recommends that the A-plan (RC-lining) is

the most preferable for seismic retrofitting of existing Meghna Bridge piers. This is due to the

least construction cost, which is the same reason considered for Meghna Bridge.

Table 8.7.3 Retrofitting Piers


◎ ◎ ◎


◎ ◎ ◎


◎Effect on acquaticenvironment

Good ◎ Good

△◎◎Extre provisionNo need protection from heavier floatingbodies

NeedNo need

Easy ◎ ◎

△

C plan: polymer mortar casting reinforcement

Difficult △

Inspection

B plan: Steel casting reinforcementA plan: RC casting reinforcement

Structural performance

Need cofferdam

Evaluation

Cost △

Constructability

Maintenance

No need

Easy

Good Good

Construction

Construction period

△△◎

○◎

Need cofferdam

Easy

Need cofferdam

LongLong ◎△

◎◎ △ EasyDifficult

Image

Landscape

No needNeed

Many Not so many Few

Short

1.00 2.04 2.43

Good

◎ Good

4900

5800

20361

1000

19361

250 250

4900250 250

Anchor

250

Existing pier

250

100150

100 150

A A

A-A

a part

a

39

Existing pier

39

309

30 99 30 94900

5800

20361

1000

19361

30

490039 39

Anchor

A A

a

A-A

a part

Steel

Less-shrinkage

Concrete

mortar t=30mm

4900

5800

20361

1000

19361

82 82

490082 82

Anchor

82

Existing pier

82A A

A-A

a part

a


8-38


Following a method similar to that stated above for Kanchpur and Meghna Bridges, the

capacity of Gumti Bridge foundations is verified under load specifications in the current

design standards. The current design specifications consider the seismic force as per BNBC

along with the higher scouring level that is expected. The computed result shows a similar

tendency that has been verified for Kanchpur and Meghna Bridges. The capacity of the

foundation corresponding to pier P6 does not meet the demand requirements and requires

retrofitting /additional reinforcement.

Table 8.7.4 Strength Check for Foundation of Pier P6

Similarly, two retrofitting plans are also considered for Meghna Bridge foundation.



mm 53 15 OUT

Max kN 24327 43479 OK

Min kN -15814 -38177 OK


mm 22 15 OUT

Max kN 15256 43479 OK

Min kN -3438 -38177 OK


Demand

Displacement

Capacity CheckUnit


Axial force

Naturalperiods


0.6 0.33

Displacement

0.270.8


Axial force

10500

2@3750=7500

2@3750=7500

Φ4900

10500

37503750

10500

15001500

Φ4900

9200

2800

▽S W WL RL+5.250

5800

7000

2800

20360

1500

2500

φ1.5m N=8, L=66.0m


1000

12360

11914


▽RL-8.500


Final Report

8-39

A comparative study of the two alternative plans highlighting their construction cost and

scouring effect on the river bed is shown in Table 8.7.5. From this comparison, the JICA

study team recommends that the A-plan (Steel Pipe Sheet Pile) is the most preferable option

for retrofitting of existing Gumti Bridge pier foundation. This is due to the least construction

cost and small scouring effect on the river bed.

Table 8.7.5 Retrofitting the Foundations

Image

B plan: Additonal RC pileA plan: Steel pipe sheet pile

◎

1.481.00

Cofferdam

Foudation size Large

SP

Small

Not required

Evaluation

Cost

φ1.5m N=8, L=66.0m


▽RL-10.00

▽RL+14.361

▽RL-8.500

5922

20400

15600

4000

S.H.W.L ▽RL+5.14

▽RL-72.10

800 17750

Φ4900

9200

2800

5800

7000

2800

20360

1000

12360

Clearance 8220

9640


PIERP6

New BridgeExisting Bridge


56350

1500 3750 3750 1500

10500

11910

φ1.5m N=54, L=65.0m


4900 4525 14600

7500 6775

6550 2425

2500

33000

9@5000=300001500

25500

1500

6@3750=22500

1500

1500

φ1.5m N=8, L=66.0m


▽RL-10.00

▽RL+14.361

▽RL-8.500

5922

21400

15600

3000

S.H.W.L ▽RL+5.14

▽RL-72.10

▽RL-5.50

800 17750

Φ4900

9200

2800

5800

7000

2800

20360

1000

12360

Clearance 8220

10640


3000

PIERP6

New BridgeExisting Bridge


50450

1500 3750 3750 1500

10500

11910

14600

7300

249607490 7490

14970

9200

6980

39930

10500

10500

C L

2500

Φ4900

φ1000 L=73.5mSteel pipe sheet pile

Clearance

Existing Bridge New Bridge


8-40

8.7.4 Evaluation and Recommendations for Work to Prevent Bridge Collapse

The work to prevent bridge collapse that was already explained for Kanchpur Bridge in

subsection 8.5.5 will also be used for Gumti Bridge.

8.8 Consideration of Damages on Meghna Bridge and Gumti Bridges

8.8.1 General

Meghna Bridge and Gumti Bridge are multi span continuous prestressed concrete rigid frame

bridges having, in the middle of each span between piers, hinges and expansion joints where

no bending moments occur. The hinges are fixed in the vertical direction to transmit the

shearing forces between the cantilevers projecting from the piers whereas they are free in the

horizontal direction to eliminate restraint forces due to creep, shrinkage and temperature

change in the structures and thus greatly reduce the sizes of the substructures / foundations.

8.8.2 What Happened to the Hinges and Expansion Joints

(1) Damages to the hinges

It has been observed that the hinges lost their proper function to transmit the shearing forces

between the cantilevers projecting from the piers, generating noises and unfavorable impact

forces on the expansion joints when vehicles move from one cantilever to the other cantilever.

Recent investigations showed the deteriorated rubber plates in the hinges as below.

Rubber plate (Originally 20 mm thick)

Damaged rubber plate (Thickness 0 to 8 mm)

Damaged rubber plate (Plan view)

Figure 8.8.1 Deterioration in Hinges

(2) Damages to the expansion joints

As shown on the right in Figure 8.8.1 the expansion joints also deteriorated as a result of

unfavorable impact forces acting frequently on them caused by the loss of proper function of

the hinges.


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8-41

Plane touch type

Line touch type

Figure 8.8.2 Deterioration in Expansion Joints

8.8.3 Possible Causes of the Damages

(1) Possible causes of the damages to the hinges

Historically, the common types of hinges used to be the line touch type shown in Figure 8.8.3.

As this type is vulnerable to abrasion from the steel components in the contact points due to

the horizontal movement, there were many cases where the line touch type was replaced by

the plane touch type shown in Figure 8.8.3 as the repair works.

Conceptual drawing of the hinge Mechanism of the hinge

Figure 8.8.3 Types of Hinges

Stainless steel plate

R i

Movement

Tightly contained rubber Bearing

Movement

Rotation


8-42

As can be seen in the figure, the plane touch type has improved resistance to abrasion due to

horizontal movement. On the other hand, it should be noted that the plane touch type may

have less capacity to accommodate the rotation than the line touch type.

When used for the repair works of an existing bridge where the creep deflection has finished

and the rotation of the hinge will be relatively small because it is generated mainly by the live

loads, adopting the plane touch type will cause no major problems due to the rotation.

In the case of a newly constructed bridge, however, a pre-camber is prescribed in the girder to

accommodate the creep deflection and as a result of it a considerable amount of rotation will

be generated between at the time of completion and at the time of reaching the permanent

condition―the creep is finished. See Figure 8.8.4.

Pre-camber = creep deflection = profile at the time of closure – planned permanent profile

Figure 8.8.4 Creep Deflection of the Bridge Girders

Meghna Bridge and Gumti Bridge adopted the plane touch type of hinges as shown in Figure

8.8.5. There could have been a possibility that the rubber plates in the hinges had a distorted

deformation due to the rotation caused by the creep deflection with an amount exceeding the

planned value, since the actual magnitude of the creep could have been larger than the

planned depending on various conditions such as not only the actual mix proportion and

characteristics of the materials used for the concrete but also the climate or environmental

conditions. If that was the case then the rubber plates which had already been stressed some

amount could have been excessively stressed when they were subjected to the live loading

effects.

Figure 8.8.5 Hinge of Gumti Bridge

According to the current observations, strict control of the axle load of the trucks, with a limit

of 20 tons, has just recently become effective at the entrance to the toll gate of Meghna

Precamber Profile at the time of closure

Planned permanent profile


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Bridge. It was observed before then that a number of trucks with remodeled suspension and

tires which appeared to carry an axle load well over 20 tons, namely 30 or even 40 tons were

passing over the roads and bridges.

In this way Meghna Bridge and Gumti Bridge have been often occupied by trucks heavily

overloaded in comparison with the design truck so as to further increase the excessive

stresses in the rubber plates.

Consequently, complex factors as described above may have hastened deterioration of the

rubber plates in the hinges, gaps between the female (concaved) parts and the male (convex)

parts having been formed accordingly.

(2) Possible causes of the damages in the expansion joints

Following the above consideration, it can be said that;

Once a gap was formed in the hinges, unfavorable impact forces were generated when

the vehicles move from one cantilever to the other cantilever over an expansion joint,

which would be rapidly deteriorated, since such impact forces were considerably larger

than the forces envisaged in the design.

The heavily overloaded trucks further increased the unfavorable impact forces, which

again further deteriorated the expansion joints.

The type of the expansion joint adopted, consisting of steel and rubber, would have

been appropriate if the gap in the hinge was not formed and the trucks moving over it

were not overloaded. But in the case of a gap having been formed for reasons described

above, this type would be much more vulnerable than a type like the steel finger joint.

In addition, it can be said that inappropriate maintenance, which might have not been done in

a timely manner, spurred the deterioration of the expansion joints. It looks from the

observation of the image on the right that the fixing bolts, crucial components, might have

not been adequately taken care of.

8.8.4 Conclusions

(1) Possible causes of the damages to the hinges and expansion joints

It can be said that the damages to the hinges and expansion joints on Meghna Bridge and

Gumti Bridge have been caused by;


8-44

Creep deflection of the girder which may have been unexpectedly larger than the

planned,

Heavily overloaded trucks,

Inappropriate maintenance, which might not have been done in a timely manner.

(2) Appropriateness of the design and construction

As described in Figure 8.8.4 the adoption of a structural system with the hinges in the mid

span eliminated restraint forces due to creep, shrinkage and temperature change in the

structures and thus greatly reduced the sizes of the substructures / foundations. Adoption of

the continuous girder with sliding bearings on the piers to eliminate the restraint forces would

have greatly increased the cost because of the expensive bearings. Adoption of the continuous

girders with neither the mid span hinges nor the sliding bearings on the piers would have also

increased the cost because of the increased substructures / foundations due to the restraint

forces. Consequently it can be said the design was the most appropriate at the time.

From the viewpoint of constructability, there have been no particular observations showing

any sign of faulty construction.

CHAPTER 9

OUTLINE OF THE DESIGN


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9. OUTLINE OF THE DESIGN

9.1 Road

9.1.1 Geometric Design

(1) Design Principles

The following design principles were considered for setting alignment.

Compliance with the required parameters of the adopted design speed

Balancing the size and length of curves

Balancing the horizontal, vertical and cross-sectional parameters

Method of construction

Constraints due to natural conditions such as terrain, geological features and existing

property

The horizontal alignment is finalized considering mobility, safety and comfort which are

derived from balanced design parameters. In addition to the above, the following conditions

are taken into account for the vertical alignment design.

Start point and end point of the horizontal alignment follow the existing NH-1 center

line.

New alignment is next to and parallel to the existing road and bridges, therefore, the

new vertical alignment is set to almost the same level as the existing to secure adequate

navigation clearance under the bridge section.


9-2

(2) Geometric Design Outline

The application of the design parameters are shown in Table 9.1.1.

Table 9.1.1 Geometric Design Outline

Parameters Unit Applied Kanchpur Meghna Gumti

Length m

STA 0+0.0 -

STA 1+100.0 Road L=703,5

(Bridge L=396.5 m)

STA 0+0.0 -

STA 1+800.0 Road L=870

(Bridge L=930.0 m)

STA 0+0.0 -

STA 2+420.0 Road L=1010.0

(Bridge L=1410.0 m) Maximum Slope Height

m 12.6 10.5 6.3

Design Speed km/h 80 80

Lane Width m 3.65 3.65

Outer Shoulder m 1.8 1.8

Inner Shoulder m 0.3 0.3

Cross fall of Travel Way

% 3.0 3.0

Maximum Super Elevation

% 7.0 7.0 7.0 7.0

Minimum R. of Horizontal Curve

m 250 340 390 350

Maximum Gradients

% 5.0 4.5 3.0 3.0

Minimum Vertical Curve K Value

m 35 37 35 74


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9.1.2 Pavement Design

(1) Introduction

Pavement design is carried out based on the consideration of the constraints of the three

bridge sites.

(2) Equivalent Single Axle Load (ESAL) Calculations

For pavement design, all heavy commercial vehicles are expressed in the terms of the

equivalent number of standard axles that they represent. 8,160 kg is taken for a standard axle.

Based on axle load studies previously undertaken in Bangladesh, the following equivalence

factors have been determined.

Table 9.1.2 Vehicle Equivalent Factor

The cumulative ESAL for design is calculated using the following equation;

ESAL = Traffic volume of vehicle type for 20 years x DDF x LDF x VEF

DDF: Directional Distribution Factor = 0.5

LDF: Lane Distribution Factor = 0.7 for 3-lanes, 0.6 for 4-lanes

VEF: Vehicle Equivalent Factor

Table 9.1.3 Summary of ESAL

Section 10 years (million)

20 years (million)

Kanchpur site 102 207

Meghna, Gumti site 97 229

(3) Flexible Pavement Design

Flexible Pavement Design is carried out by two methods namely;

Vehicle Category Equivalence Factor

Large Truck 4.8

Medium Truck 4.62

Small Truck 1.0

Large Bus 1.0

Mini Bus 0.5


9-4

AASHTO Guide for the Design of Pavement Structures

RHD’s Pavement Design Manual

(4) AASHTO Design Method

The AASHTO method for the design of pavement structure is based on the consideration that

a pavement life is a function of;

Traffic loading

Pavement strength

Pavement serviceability

Sub-grade strength

The relationship between the above factors can be mathematically represented as;

Log ESAL = Z.S. + f1 (SN) – 0.20 + f (P0 – P1) / f2 (SN) + f (MR)

Where

ESAL: Cumulative Equivalent Single Axle Loads

Z.S.: Adjustment factor to offset unreliability of traffic volumes and serviceability

SN: Structural Number

P0: Initial Serviceability

P1: terminal serviceability

MR: resilient modulus of sub-grade

SN: a1D1 + a2D2m2 + a3D3m3

a: layer coefficient

D: layer thickness in inches

m: drainage coefficient of base and sub-base


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The structural number (SN) is represented by the sum total of the multiplication of the layer

coefficient, the thickness in inches, and drainage coefficient of each layer in the pavement

structure.

The AASHTO equation can be solved by mean of a nomograph include in the AASHTO

Guide for Design of Pavement method that involves certain input variables, which are as

follows;

Traffic or Cumulative Equivalent Single Loads (ESAL)

Reliability (R)

Standard Deviation (S0)

Resilient Modulus of Subgrade (MR)

△Loss in Serviceability ( PSI)

Structural Layer Coefficients

1) Design Life

Design life is the number of years reckoned from the completion of pavement construction

and application of traffic load until the time when major maintenance is required so that it can

continue to carry traffic satisfactorily for a further period. A design life of 20 years is adopted

for this project and is recommended in general as per Pavement Design Guide (RHD). For

comparison of design life between 20 years and 10 years refer to Appendix 8.

2) Design CBR

A CBR value of 5 % is recommended in general as per the Pavement Design Guide (RHD).

The CBR values at the site surveyed range from 4 to 8 and the average CBR at the site is

beyond 5 %.

The soil parameter used in the AASHTO Guide for Pavement Design is the Modulus of

Resilience (MR). Therefore the design CBR needs to be converted into the corresponding MR

value. There is a widely used correlation for CBR and MR up to 10. The correlation is below.

MR=1500*CBR


9-6

3) Thickness Design

Design Parameters

20 years ESAL = 229 Million

Modulus of Resilience (MR) = 12000 Psi

Reliability (R) = 95 %

Standard Deviation (So) = 0.45

Initial Serviceability Index (Po) = 4.2

Terminal Serviceability Index (Pt) = 2.5

Design Thickness

Bituminous Wearing Course 5 cm

Bituminous Binder Course 20 cm

Aggregate Base Course 35 cm

Aggregate Subbase 40 cm

For detailed calculations, refer to Appendix 8.

(5) RHD Design Manual

The subject design guide is a simplified version of various international standards with due

modifications keeping in view local conditions and practices. The thickness design shown in

the table provides variable thicknesses of bituminous pavement, base and subbase for discrete

ranges of ESAL from 3-4 million to 60-80 million. The target ESAL is beyond the range of

ESAL value in the RHD Design Manual, therefore pavement thickness is adopted from the

AASHTO Design Method.

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9.1.3 D

rawing

Figure 9.1.1 Plan and Typical Cross Section at Kanchpur

Project area L=1100m

Approach Road L=327.0m Approach Road L=376.5m Bridge L=396.5m

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Figure 9.1.2 Plan and Typical Cross Section at Meghna


Approach Road L=438m Bridge L=930.0m Approach Road L=m432.0

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Figure 9.1.3 Plan and Typical Cross Section at Gumti


Approach Road L=695.0m Bridge L=1410.0m

Approach Road L=315.0m


9-10

9.2 The 2nd Bridges

As per the clarification letter No.35.033.014.00.00.007.2012 -161 issued by Ministry of

Communication (MoC) of Bangladesh on 13th August 2012, the type of the 2nd Bridges would

be ‘Steel Narrow Box Girder Bridge’. The reason behind this bridge type selection is its

relatively least construction cost, least construction period and constructability. The Steel box

girders have been chosen for the superstructure of the 2nd bridges; therefore the span for the

2nd Kanchpur Bridge will be larger than that of the existing one. But, for the 2nd Meghna and

2nd Gumti Bridges, the span allocation is kept the same as the existing one. This is because

the same span allocation will ensure the same number of foundations for the 2nd and existing

bridges. Therefore, it will be easier to unify the new foundations with the adjacent existing

foundations, which will secure the least construction cost and minimize the scouring in the

riverbed.

(1) Superstructure design

For the superstructure, steel narrow box girders is chosen in order to reduce the

superstructure weight and increase the earthquake resistance capacity of the bridges.

(2) Foundation design

In order to determine the foundation type for the 2nd bridges, the following factors are taken

into consideration.

-Design scouring level is revised in consideration of new research results and a river study.

-Cost factor

Cast-in-place RC pile foundation and Steel Pipe Sheet Pile (SPSP) foundation are taken into

consideration and they are compared with respect to the cost aspect. These factors are studied

for the respective 2nd Bridges and the computed results are shown in the following sections.


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9-11

9.2.1 The 2nd Kanchpur Bridge

(1) Design Scouring Level

Using the bathymetric survey results, the scouring level along the river cross-section at the

bridge center line is estimated and graphically shown as blue line in Figure 9.2.1. This figure

also shows the design scouring level at each respective pier. The design scouring levels (red

line) are categorized as follows;

Shallow scouring: RL= - 1.4m

Severe scouring: RL= - 18.0 m

It can be observed that piers P1, P2 and P3 are located in shallow scouring zones (RL=-1.4m),

whereas piers P4, P5 and P6 are located in severe scouring zones (RL=-18.0m). The

foundation type for each pier is examined in accordance with the design local scouring level.

Design Scouring Level

Estimated Scouring Level

RL=-1.39m RL=-18.01m

P1 P3 P5 P6 P7P2 P4

Figure 9.2.1 Riverbed Scouring and Design Scouring Level for the 2nd Kanchpur Bridge

(2) Foundation type selection

It can be seen from Figure 9.2.1 that the foundations of piers P4, P5 and P6 of 2nd and the

existing bridges are located in severe scouring zones. A cast-in-place RC pile foundation and

Steel Pipe Sheet Pile (SPSP) foundation are examined considering the severe scouring level

(RL=-18.0m) parameter and then, their construction cost is compared as already seen in

Table 8.5.9. It can be found that the construction of SPSP foundation in a severe scouring

zone is cost effective. Moreover, implementing SPSP technology is a countermeasure to

scouring.

It is also decided that the foundations for piers P1, P2 and P3, which are located in areas with

shallow riverbed scouring should also be SPSP type. This is just to maintain conformity with

the existing caisson foundation that needs to be retrofitted. Therefore, for the 2nd Kanchpur

Bridge, the foundation of piers P1-to-P6 will be the SPSP type and their foundations will be

unified with those of the adjacent existing foundations. On the other hand, the foundation of


9-12

pier P7 only will be a cast-in-place RC pile type which is designed as a single type

foundation that means that there will be no interference with the existing foundation.

(3) Results of the Study

The general outline of the design is summarized in Table 9.2.1. Consequently, the general

view of the 2nd Kanchpur Bridge is schematically shown in Figure 9.2.2.


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9-13

Table 9.2.1 Outline of Design (The 2nd Kanchpur Bridge)

Bridge type Continuous steel narrow box girder

Configuration of bridge superstructure

Bridge length = 396.5 m Girder length = 396.0m Span = 41.6 m + 85.4 m + 97.6 m + 73.2 m + 54.9 m + 41.6 m

Number of lanes 4-lanes

Cross section

18.4 m (1.1 m (sidewalk ) + 14.6 m (road) + 2.7 m (sidewalk))

18400

CL

7300 500 2000 2001100 7300

2700 6500 6500 2700

2.0%1.0%

100

3300

1200

250

80

Superstructure 3-box girders (1.2 m x 3.3 m) with PC floor slab (t=25 cm)

Abutment Inverted T-type

Number: 2 Height: 7.5 m

Piers Columnar type

Number: 5 Height: 10.64 m - 15.55 m

Abutment Cast-in-place RC pile (φ1.5 m): A1&A2; n=6, L=36.0 m

Cast-in-place RC pile (φ1.5 m): P7; n=8, L=18.0 m

Bridge components Substructure

Foundation Piers

SPSP (φ1.0 m) P1 to P5; max 34.94 m x 11.23 m (including existing)

min 33.7 m x 8.74 m (including existing) L = 33.0 m

Live load JRA B-type (only for floor slab system) AASHTO HS20-44 (for girder and substructure)

Seismic load 2/3

1.22.5sm

m

ZSC Z

T ; where Z=0.15 and S=1.5

Wind load 3.0 kN/m2

Loads

Thermal force Temperature range: +10 oc to +50 °c

Specification

Steel Grade-SM490A (JIS)

u = 490 MPa, y = 315 MPa

PC steel bar Grade-SWPR7BL (JIS)

u = 1,850 MPa, y = 1,600 MPa Superstructure

Concrete (Precast)

JIS

c = 50 MPa

Concrete (cast-in-place)

RHD

c = 25 MPa

Rebar Grade-60 (ASTM)

u : 620 MPa, y : 420 MPa

Construction materials

Substructure

SPSP

SKY400 and SKY490 (JIS)

u = 400 MPa and 490 MPa

y = 235 MPa and 315 MPa

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Figure 9.2.2 General View of Kanchpur Bridge

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Figure 9.2.3 CG of Completed the 2nd Kanchpur Bridge (Dhaka side)


9-16

9.2.2 The 2nd Meghna Bridge


Using the bathymetric survey results, the scouring level along the river cross-section is

estimated and graphically shown as blue line in Figure 9.2.4. This figure also shows the

design scouring level for each respective pier. The design scouring levels (red line) are

categorized as follows;

Shallow scouring : RL=-4.6 m

Medium scouring : RL=-14.90 m

Severe scouring : RL=-26.2 m

It can be observed that piers P1 and P2 are in shallow scouring zones (RL = -4.6 m), whereas

piers P3-P5 are in medium scouring zones (RL = -14.90) and P6-P11 are in severe scouring

(RL = -26.2 m) zones. The foundation type for each pier is examined in accordance with

these three categorized design scouring levels.

23



RL=-4.6m RL=-14.90m

RL=-26.19m

P1 P2 P3 P4 P5

P6 P7 P8 P9 P10P12

P11

Figure 9.2.4 Riverbed Scouring and Design Scouring Level for the 2nd Meghna Bridge


1) In case of shallow scouring

The foundation of pier P2 (new bridge) is close and parallel to that of P2 (existing bridge).

Their foundations will be combined so as to secure the least construction cost. It is also


Final Report

9-17

observed from Figure 9.2.4 that they are located in a shallow scouring zone. A cast-in-place

RC pile foundation and Steel Pipe Sheet Pile (SPSP) foundation are examined considering

the shallow scouring zone (RL = -4.6 m) and then, their construction costs are compared as

already seen in Table 8.6.5. The construction of cast-in-place RC pile foundation in a shallow

scouring zone is cost effective.

2) In case of medium and severe scouring

It can be observed from Figure 9.2.4 that the foundations of pier P5 (2nd and existing bridges)

are located in a medium scouring zone. A cast-in-place RC pile foundation and Steel Pipe

Sheet Pile (SPSP) foundation are also examined considering the medium scouring level

(RL=14.90 m) and then, their construction costs are compared as already seen in Table 8.6.6.

From this comparison, it can be seen that the construction of an SPSP foundation in a

medium scouring zone is cost effective. This is because no temporary cofferdam is required

to construct an SPSP foundation and thereby it secures the least construction cost.

The foundation selected for a medium scouring zone is the SPSP type, therefore, the

foundation for a severe scouring zone undoubtedly will be evaluated as an SPSP type.

Therefore, no additional comparison between the said foundations in severe scouring zones

needs to be shown.

(3) Remarks on foundation type

From the above results, it can be concluded that where the riverbed scouring level is medium

to severe, the SPSP type foundation will be economical and additionally it will act as a

scouring countermeasure. On the other hand, where the riverbed scouring level is shallow, a

cast-in-place RC pile foundation will be cost effective.


The general outline of the design and the obtained output results are summarized in Table

9.2.2. Consequently, the general view of the 2nd Meghna Bridge is schematically shown in

Figure 9.2.5.


9-18

Table 9.2.2 Outline of Design (The 2nd Meghna Bridge)



Bridge length= 930.0 m Girder length= 929.1 m Span= 47.4 m [email protected] m + 73.5 m + 23.9 m


Cross section

17.75 m (1.1 m (sidewalk) + 15.55 m (road) + 1.1 m (sidewalk))

17750

CL

11001100

2675 6200 6200 2675

100

3310

1200

240

65010950 3950

2.0％ 2.0％

80




Pier Columnar type


Abutment Cast-in-place RC pile (φ1.5 m): A1&A2; n=6, L=48.0 m

Cast-in-place RC pile (φ1.5 m): P1,P2&P12; n=6-12, L=35.0 m-44.0 m


Foundation Pier SPSP (φ1.0 m)

P3-P10; 39.93 m x 14.97 m (including existing) L = 42.65 - 44.15 m


Seismic load 2/3

1.22.5sm

m

ZSC Z


Wind load 3.0 kN/m2

Loads

Thermal force Temperature range: +10 oc to +50 °c Specification


u = 490 MPa, y = 315 MPa



Concrete (Precast)

JIS

c = 50 MPa

Concrete (cast-in-situ)

RHD

c = 25 MPa


u : 620 MPa, y : 420 MPa

Construction Materials

Substructure

SPSP




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Figure 9.2.5 General V

iew of M

eghna Bridge

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Figure 9.2.6 CG

of Com

pleted the 2nd M

eghna Bridge (C

hittagong side)


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9.2.3 The 2nd Gumti Bridge


Using the bathymetric survey results, the scouring level along the river cross-section is

estimated and graphically shown as blue line in Figure 9.2.7. This figure also shows the

design scouring level (red line) for each respective pier. The design scouring levels are

categorized as follows;

Shallow scouring : RL= -0.7 mto -2.8 m

Severe scouring : RL= -17.1 m

It can be observed that the piers P1-P8 are in severe scouring zones (RL = -17.1 m), whereas

piers P9-P16 are located in shallow scouring zones (RL = -0.7 to -2.8 m). The foundation

type for each pier is examined in accordance with these two categorized scouring levels.



P1 P2 P3 P4 P5

P11 P12 P13 P14 P15 P16

P6 P7 P8 P9

P10

RL=-0.69m

RL=-17.05m

RL=-2.75m

Figure 9.2.7 Riverbed Scouring and Design Scouring Level for 2nd Gumti Bridge


As is already stated for the 2nd Meghna Bridge, a combined cast-in-place RC pile foundation

will secure least construction cost where the riverbed scouring is shallow, whilst the

combined SPSP foundation is cost effective where the riverbed scouring is severe. The same

results are also observed for the 2nd Gumti Bridge. Therefore, it is decided that the

foundations for piers P1-P8 in severe scouring zones will be designed as SPSP foundations

and that for piers P9-P16 in shallow scouring zones will be designed as cast-in-place RC pile

foundation. The foundations of piers P1-to-P8 of the new bridge will be unified with that of

the corresponding existing pier. But, the remaining foundations will be single type

foundations and there will be no interference with the existing foundations.


9-22


The general outline of the design and the design outputs are summarized in Table 9.2.3.

Consequently, the general view of 2nd Gumti Bridge is schematically shown in Figure 9.2.8.

Table 9.2.3 Outline of Design (The 2nd Gumti Bridge)



Bridge length = 1,410 m Girder length = 747.75 m + 660.75 m Span = 51.4 m + [email protected] m + 86.15 m, 86.15 m + [email protected] m + 51.4 m


Cross section

17.75 m (1.1 m (sidewalk) +15.5 5m (road) + 1.1 m (sidewalk))

17750

CL

1100 1100

2675620062002675

100

3310

1200

240

650 109503950

2.0％2.0％




Pier Columnar type


Abutment Cast-in-place RC pile (φ1.5 m): A1&A2; n=6, L=66.0-m Cast-in-place RC pile (φ1.5 m): P9-P16; n=8, L=62.0 m-


Foundation Pier SPSP (φ1.0 m)

P1-P8; 34.93 m x 14.97 m (including existing) L=62.0 m - 70.0 m


Seismic load 2/3

1.22.5sm

m

ZSC Z


Wind load 3.0 kN/m2

Loads

Thermal force Temperature range: +10 oc to +50 °c Specification


u = 490 MPa, y = 315 MPa



Concrete (Precast)

JIS

c = 50 MPa

Concrete (cast-in-situ)

RHD

c = 25 MPa


u : 620 MPa, y : 420 MPa

Construction Materials

Substructure

SPSP




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9-23

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9-24

Figure 9.2.8 General View of Gumti Bridge

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9-25

Figure 9.2.9 CG of Completed the 2nd Gumti Bridge (Dhaka side)


9-26

9.2.4 Bridge Accessories

As the bridges are planned as the steel structure, therefore the bridge accessories should be

considered as water proof at the design stage in order to avoid corrosion in the girders.

(1) Expansion joints

Table 9.2.4 Horizontal Movement of Expansion Joint

Bridge Horizontal movement Type

Kanchpur ±170 mm

Meghna ±400 mm

Gumti ±300 mm

Finger non-drainage type

The expansion joints should be designed as non-drainage type in order to avoid the water

leakage into the end of girder and also near the abutment. The water will be passed through

drainage system from the outside of the girder and from the water tight rubber drain under the

fingers.

The finger type is chosen from the view point of durability against heavy loading trucks. In

that case, the steel finger is more durable than the rubber top expansion joints.

(2) Water drain system

The road surface catchment should be located at the end of surface and the collected water

will directly drop to the river. The pipe end is set 1 m below the girder in order to avoid water

spray back to the girder.

Table 9.2.5 Drainage System (Direct Drop)

Item Material Remarks

Catchment drain Cast Steel Buried in the PC deck

pipe Vinyl chloride pipe

Pipe support Steel Directly fixed to the girder

(3) Bearing shoes

The bearing shoes are rubber bearings for the movement and seismic resistance. The

durability of rubber bearing is secured by a lapping layer over the rubber against ultraviolet

for 100 years. And the rust prevention for bearing accessories should be achieved by metallic

thermal spraying which is expected to be lasting as 100 years.

Table 9.2.6 Bearing Movement

Bridge Movement Maximum Reaction Force

Kanchpur ±170 mm 1250 t

Meghna ±400 mm 1150 t

Gumti ±300 mm 1300 t


Final Report

9-27

(4) Inspection way

The inspection ways should be made of galvanized steel structure in order to inspect the piers

and the girders at some time intervals.

Type: Girder with railing

Size: Width 60 cm, railing height 120 cm

Material: Galvanized steel


9-28

9.3 Existing Bridges

9.3.1 General

The present conditions observed and investigated have been examined and the latest design

criteria to be conformed to have also been considered. As a result, the existing bridges,

Kanchpur Bridge, Meghna Bridge and Gumti Bridge have been determined to need to be

retrofitted and rehabilitated in the manner described as follows.

9.3.2 Scope of the Retrofitting and Rehabilitation Works

It has been determined that the scope of the rehabilitation works shall be defined as the repair

works for the damaged expansion joints in Kanchpur Bridge, Meghna Bridge and Gumti

Bridge and the repair works for the damaged hinges in Meghna Bridge and Gumti Bridge.

The retrofitting works shall be defined as the works to renew the bridge structures to conform

to the current bridge design standards and to cope with the current and future scouring

conditions. As mentioned in the previous chapter the changes of the design seismic force

should be reflected in all the bridges and the changes of the live load should be reflected in

Kanchpur Bridge.

The repair works for the damaged hinges shall be connecting two cantilever girders to

become monolithic, eliminating the hinge and expansion joint, at each hinge section. As the

hinge section shall remain in every 5 or 6 spans to avoid excessive restraint forces to be

generated by the temperature change, the hinges and expansion joints at such sections shall

be replaced by new ones.

To prevent the bridge from collapsing during earthquake the steel brackets will be attached to

the substructures at the girder ends. At the having joint of Kanchpur Bridge the girder ends

are connected to each other (Fail-safe connection).

Consequently, the scope of the retrofitting and rehabilitation works for Kanchpur Bridge,

Meghna Bridge and Gumti Bridge are summarized below.


Final Report

9-29

Table 9.3.1 Scope of the Rehabilitation and Retrofitting Works


Repair of cracks/rebar exposures ○ ○ ○

Connecting girders (eliminating hinges/joints)

- ○ ○

Center hinge rehabilitation - ○ ○

Expansion joint replacement ○ ○ ○

Steel brackets on the substructures ○ ○ ○

Fail-safe connection ○ - -

Deck strengthening ○ - -

RC-lining ○ ○ ○ Piers

Diaphragm wall ○ - -

Pile cap integration P1, P3, P5, P6 P1 to P10 P1 to P8

Steel pipe sheet piles P1 to P6 P3 to P10 P1 to P8 Foundations

Bored RC piles - P1, P2 -


9-30

9.3.3 Retrofitting and Rehabilitation Works

(1) Existing Kanchpur Bridge

The general outline of the design and the design outputs are summarized in Table 9.3.2.

Table 9.3.2 Outline of Design (Existing Kanchpur Bridge)

Bridge data Length = 395.6 m : [email protected] m + 54.9 m + 73.2 m + 54.9 m+42.7 mWidth = 14.64 m

Superstructure

Pre-stressed concrete I girder, continuous type (54.9 m + 73.2 m + 54.9 m) Pre-stressed concrete I girder, simply supported type (42.7 m5 spans)

915 12810 915

229 229686 12810 686

14640

915

229

176

838 1297 838

176

2286

6@2135=12810


Pier Rigid frame-type

Bridge components

Substructure

Foundation Abutment: Spread foundation Pier: RC open caisson


Seismic load 2/3

1.22.5sm

m

ZSC Z


Wind load 3.0 kN/m2

Loads

Thermal force Temperature range: 26 17c c

Repair of cracks/rebar exposures

N/A Girder and deck

Deck strengthening Carbon fiber sheet adhering A1 to A2

Expansion joint replacement A1 to P4, P7, A2 Bridge accessories Steel brackets A1 to P4, P7, A2

RC-lining P1 to P7 Pier

Diaphragm wall P1 to P7

Foundation Steel pipe sheet piles P1 to P6


Final Report

9-31

(2) Existing Meghna Bridge

The general outline of the design and the design outputs are summarized in Table 9.3.3. The

connection of the hinges should be the same as Figure 9.3.1.

Table 9.3.3 Outline of Design (Existing Meghna Bridge)

Bridge data Length = 930 m : 48.5 + [email protected] + 73.5 + 25.0 m Width = 9.2 m

Superstructure

Pre-stressed concrete box girder, continuous rigid frame type (48.5 m + 9*87.0 m + 48.5 m) Pre-stressed concrete T girder, simply supported type (2*25.0 m)


Bridge components


Abutment: Cast-in-place RC pile (φ1,500) Pier: Cast-in-place RC pile (φ1,500)

Live load AASHTO HS20-44 (for girder and substructure)

Seismic load 2/3

1.22.5sm

m

ZSC Z


Wind load 3.0 kN/m2 Loads


Repair of cracks/rebar exposures P12 to A2 Girder and deck Connecting girders (eliminating

hinges/joints) All except P5 to P6

Center hinge rehabilitation P5 to P6 Expansion joint replacement A1, P5 to P6, A2 Bridge

accessories Steel brackets A1, A2

Pier RC-lining P1 to P12

RC casting reinforcement P1 to P10

Steel pipe sheet piles P3 to P10 Foundation

Bored RC piles P1,P2

9200

5800

250

1800

3500

800

1950

250

200

5000 1950

2300

250

250

2.0%

800

2.0%

50

300 70

7200

600

5001000

1950

400

500

750

600

550

LC

200

2550 1200

1350

9200

200800

900

2%120

800

2%

7200

350

4X1850=7400

1500

500

900

200

CL


9-32

STEP-1: Removal of expansion joint in top slab and chip bottom slab.

Weld rebars for connecting to longitudinal rebar in top and bottom slab.

Drill holes for external cables and PC bars.

Arrange steel pipes for external cables and PC bars for connecting.

STEP-2: Cast concrete for connecting.

Having confirmed hardened concrete strength, PC bar to be connected

STEP-3: Arrange and stress the external cables.

Adhere carbon fiber sheets on the bottom slab

Figure 9.3.1 Hinge Connection of Existing Meghna Bridge

STEP-1:

STEP-2:

STEP-3:


Final Report

9-33

(3) Existing Gumti Bridge

The general outline of the design and the design outputs are summarized in Table 9.3.4. The

connection of the hinges should be the same as Figure 9.3.1.

Table 9.3.4 Outline of Design (Existing Gumti Bridge)

Bridge data Length = 1,410 m: 52.5 + [email protected] + 52.5 m Width = 9.2 m

Superstructure

Pre-stressed concrete box girder, continuous rigid frame type


Bridge components


Abutment: Cast-in-place RC pile (φ1,500) Pier: Cast-in-place RC pile (φ1,500)

Live load AASHTO HS20-44 (for girder and substructure)

Seismic load 2/3

1.22.5sm

m

ZSC Z


Wind load 3.0 kN/m2

Loads


Repair of cracks/rebar exposures P5 to P7, around P10 Girder and deck Connecting girders (eliminating

hinge/joints) All except P5 to P6 and P11 to P12

Center hinge rehabilitation P5 to P6, P11 to P12

Expansion joint replacement A1, P5 to P6, P11 to P12, A2 Bridge accessories

Steel brackets A1, A2

Pier RC-lining P1 to P16

RC casting reinforcement P1 to P8

Steel pipe sheet piles P1 to P8 Foundation

Bored RC piles N/A

200

250

250

2300

1800

800

300

7250

800 7200

500

50001950 1950

2.0% 2.0%

9200

200

CL

1000

500

600

600

250

250

5300

chapter 8 rehabilitation and retrofitting of existing bridges

Documents