case study on historical steel bridge in ahmad nagar maharashtra india

A

SEMINAR REPORT

ON

CASE – STUDY ON HISTORICAL STEEL BRIDGE

OVER RIVER 'SEENA' AT AHMEDNAGAR

PRESENTED BY

SOHEL AHMED QUADRI

GUIDED BY

PROF. M. D. SHINDE(H.O.D. Civil Engg.)

JNEC AURANGABAD

CERTIFICATE

This is to certify that the seminar entitled Case–Study on

Historical Steel Bridge Over River 'Seena' At Ahmednagar

Submitted by Mr. sohel ahmedquadri

A student of B. E. Civil, JNEC aurangabad Exam. No. BT - 450022

for the partial fulfillment for the award of degree of civil Engineering,

University of Aurangabad is approved for the year 2002 – 2003

Guide

Prof. M. D. Balte Prof. P. R. Wani (H.O.D. Civil Engg. Dept.) (Principal P.D.V.V.P.C.O.E.

Ahmednagar)

Examiner

ACKNOWLEDGEMENT

I have great pleasure in presenting this seminar report I take this

opportunity to express my profound thanks to Prof. G. P. Dhotre my

guide and inspiration and moving spirit behind my seminar, who made

a valuable contribution.

I wish to thank Prof. P.R. Wani, (Principle of P.D.V.V.P.C.O.E.) and

Prof. M.D. Shinde, (H.O.D. of Civil Engineering Dept.) for helping me to

avail the various facilities required towards my seminar.

Thanks are also to library Staff member of P.D.V.V.P.C.O.E. for

their kind co-operation towards the completion of my seminar.

INDEX

Synopsis

1) History and details of the bridge

2) Technical details

3) Present status (damaged)

4) Aim of the case study

a) To find the strength

b) To find the load carrying capacity

c) To check the feasibility of the bridge .

5) Accident – Failure Analysis

6) Remedies for damages

7) Why to Adopt Such Type of Bridge-Structures ?

Conclusion

References

SYNOPSIS

The curiosity behind the case study of the ' Seena Steel Bridge' is

that the bridge suffered a fatal accident first time in the 130-year

history of the bridge.

The 1873 constructed bridge when we were been ruled by British

has very different characteristics of steel structures in the sense it has

the curved shape of its main super structure (i.e. curved arch Pratt

truss) also the deck type carriage way without stringers. As this type

bridges are not constructed in this modern era of civil Engineering.

Bridge makes any civil engineer to think something about it.

The case study aims to find out the strength to check its

feasibility and to suggest remedies for the damages so as to reutilize

the bridge. Also provides sense to improve the urban beauty of the

city by using such type of bridges.

Case study also aims to find out the reasons behind the failure

due to the 30th July accident.

CHAPTER – 1

HISTORY & DETAILS OF THE BRIDGE

In 1878, when British Government completed construction of

Daund – Manmad broad – gauge railway line project Ahmednagar

railway station was established nine year before that British

Government constructed this bridge over ' Seena ' river to facilitate

army vehicles going from Nagar to Pune. This was to avoid the

obstacle causing by river 'Seena' in rainy days. This work was started

in 1869 under the supervision of 'Major Gambiar' & was completed by

1873 January. The steel bridge with curved arch frame was topic of

astonishment in those days.

130 years before this bridge was constructed with cost of Rs.

90,311/- having different characteristics of steel structures. The

157.2m length of bridge consists of 8 sections of 19.65 m. For

foundation trenches were excavated & constructed in stone masonry in

the riverbed, which were filled by pouring foundation blocks. On this

base 7 number M.S. pipe piers of 500-mm diameter are erected. The

abutment consists of stone masonry. The main girder consists of M.S.

plates on which cross girders rest. Each section of bridge consist of 4

no of supports. 8 no of c/s girder supports the deck – slab which in

made up of 7 no of curved mild steel sheeting on which lime concrete

slab is casted to form carriage way.

The bridge is situated on the old Nagar – Pune road going

towards railway station, which is the shortest route. The transportation

of heavy goods by railway is connected to the city by this road.

Ahmednagar city has many & different important defense offices,

camps, battalions & tank training areas for their transportation this

road is of prime importance. Also the residential population around

station road especially the 'Agarkar Mala' area is increasing day by day

therefore this road & the bridge contribute a major part of

transportation activities of the city, from the city & to the city.

Location

CHAPTER – 2

TECHNICAL DETAILS

1) Type : Bow – string girder (Deck type) bridge.

2) Length : 157.2m.

3) No of sections : 8 nos.

4) Span of each sections : 19.65m.

5) Carriage way : 5.5m.

6) Foundation : 5.18m below G.L. with double – pier support

7) Ground clearance : At abutment = 2.75m, At river bed = 5.6m.

8) Span of c/s girder trusses : 5.6m.

9) Span of Pratt truss : c/c distance between 8 no of cross girder

trusses

= 2.29 x 8

= 18.31m

10) Total length of each section :

= Span of Pratt truss + c/c distance between piers

= 18.32 +2 (1.35) 2

= 19.67m.

11) No of piers : = no of support x 2

= 7 x 2

= 14 nos. (on one side)

Total no of piers = 14 x 2

= 28 nos. (on both side)

DETAILS OF COMPONENT PARTS:

1) DECK :-

2) CROSS – GIRDER TRUSS

3) PRATT TRUSS:-

Main Girder :-

Main girder which acts as the bottom chord for the Pratt truss

consist of M.S. plates of size 150 x 13.14 mm provided with

combination of 2,3 & 4 nos. As the bending moment changes from

mid-point of the span towards end at the support these rests on pier

table & at the end of the bridge anchored into abutments for length of

2.3m from face of the wall with hold fast by pouring concrete around it.

DETAILS OF JOINTS:-

1) End portion of c/s girder truss & the Racker.

2) Connection of inclined member with main girder:-

CHAPTER – 3

PRESENT STATUS (DAMAGED)

1) The stones of abutment wall at station side have loosened as the

binding mortar in deteriorated. The main –girders resting into it

have slipped out of position. Due to which station side section is in

more dangerous condition.

2) The M.S. sheeting of the deck is completely corroded & broken,

even through – holes are created.

3) The M.S. sheeting of the deck on the both sides of the carriage way

is completely corroded & torned.

4) Except piers, main girder & Pratt – truss the c/s girder trusses are

corroded & in present status it's upper crust is getting removed

layer by layer due the which the steel – sections have become

week.

5) The compression member of the c/s girder trusses are buckled.

CHAPTER – 4

AIM OF THE CASE STUDY

A) To find the strength :-

Tensile strength test on specimens acquired from debris at site.

Result Table :-

Sr

.

N

o

Size of specimen

mm

Wt.

Kg/

m

Equivalen

t c/s area

mm2

Yield

stress

N/ mm2

Ultimate

tnsile

stress N/

mm2

Actual

thick

mm2

1. Tension member

300 x 30.92 x

13.12

2.98 379.5 236.26 370.68 14 mm

2. Compression

member

307 x 30.54 x

6.72

1.45 184.65 251.32 355.95 8 mm

3. T section

307 x 28.82 x

10.61

2.10 267.4 247.26 364.66 12 mm

4. Angle section

304 x 30.82 x

11.22

2.36 300.5 226.56 314.05 12 mm

The corrosion has made all the sections weak thickness are

reduced by 1.5 to 2 mm. Which reduces the cross sectional area by

about 10.68% therefore test results are not satisfactory as the

structural steel.

The minimum yield stress we got from test is 226.56 N/mm2.

Therefore we will consider 226 N/mm2 as yield strength of the steel

member of the bridge for the analysis.

B) To find the Load carrying capacity :-

As we know the cross – girders have suffered much of the corrosion,

obviously the max. load carrying capacity will be defined by the

max. load carried by the members of c/s girder truss.

C/s girder trusses are provided in 8 panels of Pratt truss with c/c

distance of 2.29m.

The c/s girder carries load of the deck in form point load due to

the curved arch action of M.S. sheeting.

Dead load on deck :-

1) 100 mm thick tar Macadam finish = 2.2 kN/m

2) Thickness of lime concrete = 260 + 160 2

= 210mm

D.L. for 1 m strip = 0.21 x 1 x 25 = 5.25 KN/m

3) M.S. sheeting thk = 8mm

Curved length = 835 mm

D.L. = (0.835 x 2.29 x 0.008) 7854 x 9.81

= 1178.61 N

= 10178 KN

4) Self weight of cross girder truss = 3.5 KN

5) Stringer = 0.0156 KN/m

6) Point load =

1) = 2.2 x 0.8 x 2.29 = 4.03 KN

2) = 5.25 x 0.8 x 2.29 = 9.61 KN

3) = 1.178 KN

4) = 0.0358 KN

Total Dead load at a point = 14.85 KN

Geometrical Properties For The Cross Girder Truss Sections :-

1) For Double angle 75 x 75 x 10.34 mm

r min = 21.11 mm, Iyy = 594.62 x 103 mm4 , A = 2667.04 mm2

L eff = 0.7 x 1.34

= 0.938 m

L eff = 0.7 x 1.46

= 1.008 m

2) For T sections 70 x 70 x 12.94 mm

r min = 12.95mm, Iyy = 195.95 x 103 mm4 , A = 1167.1 mm2

L eff = 0.7 x 0.53

= 0.374 m

3) Tension member : 80 x 13.02 mm

A eff = 682.23 mm2

4) Compression member : 80 x 7.64 mm

r min = 1.93mm Iyy = 2023.09 mm4 , A = 537.6 mm2

Analysis of Cross Girder Truss For Dead Load

Force Table :-

S

r.

Membe

r

P Kn A mm2 6 N/

mm2

6 a

Fy=226

N/mm2

6a – 6

Remaining

caring capacity

P=(6a – 6) x A

KN

1

)

AB, DE - 107.75 2667.0

4

40.4

0

124.

5

84.10 224.29 C

2

)

BC,CD - 138.53 2667.0

4

51,9

4

95,9

5

44.01 117.37 C

3

)

AH,FE 116.01 1916.4

5

60.5

3

135.

6

75.07 143.86 T

4

)

BH, DF -39.38 1167.1 33.7

4

131.

92

98.18 114.58 T

5

)

CG -22.59 1167.1 19.3

5

131.

92

112.57 131.37 C

6

)

CH, CF -10.53 537.6 19.5

8

122.

81

103.23 55.490 C

7

)

HG,GF 117.61 2384.3

4

43.3

2

135.

6

86.24 205.720 T

8

)

BG,DG 32.78 682.23 48.0

4

135.

6

87.55 59.730 T

The feasibility will be defined by the remaining load carrying

capacity. The feasible load will be that which will not exceed

remaining load carrying capacity.

Type of loading for checking the feasibility :-

As per the importance of the bridge, type of bridge & the area in

which the bridge is situated the Indian road congress has provided 3

types of loading for checking the feasibility of bridges.

1) I.R.C. class 'AA' – certain municipal limits, existing on

contemplated industrial areas. Some specified highways used for

tracked – vehicle with total load of 70 tones & maximum point load

of 6.25 tones.

2) I.R.C. class 'A' – on all roads for permanent bridges & culverts

used for train of vehicles with total load of 55.4 Tones & maximum

point load of 11.4 Tones.

3) I.R.C. class 'B' – for temporary structures and bridges with timber

span used for train of vehicles with total load of 33.2 Tones &

maximum point load of 6.8 Tones.

So considering the situation of 130-years life span &

importance of the structure, we will adopt I.R.C. class - B type of

loading.

I.R.C. Class ‘B’ type of loading

Force Table :-

Sr. No.

Members Force generated Kn

Carrying capacity Kn

1. AB 89.20 C < 224.292. DE 56.66 C < 224.293. BC 106.13 C < 117.374. CD 94.16 C < 117.375. AH 96.05 T < 143.866. FE 61.01 T < 143.867. HG 101.36 T < 205.728. GF 80.79 T < 205.729. BH 31.15 C < 114.58

10. CG 19.97 C < 131.3711. DF 13.83 C < 114.5812. BG 18.19 T < 59.7313. CH 12.9

7 C < 55. 49

14. CF 25.73

C < 55. 49

15. DG 39.99

T < 59.73

As the member forces are not exceeding maximum load carrying

capacity class 'B' loading is feasible.

Geometrical Properties of Pratt Truss Sections :-

Vertical members :-

A = 1508.06 mm2

I yy = 18.147 x 103 mm2

r yy = 18.26 mm

Inclined member :-

A = 1117.8 mm2

I yy = 18.147 x 106 mm4

I yy = 127.4 mm

Bottom Chord :-

L3 – L5 L5 – L7 L7 – L8

A = 7884 mm2

I yy = 1.815 x 106

mm4

r yy = 15.17 mm

A = 5913 mm2

Iyy = 0.765 x 106

mm4

r yy = 11037 mm

A = 3942 mm2

Iyy = 226.87

x 103 mm4

r yy = 7.58 mm

Top Chord :-

A = 9598.28 mm2

I yy = 40.42 x 106 mm4

r yy = 64.89 mm

Force Table :-

Sr

.

Member L mm A mm2 6 a

N/mm2

Safe load

KN

Max Member

Force KN

1. U5 U6 & U6 U7 1150 9598.2

8

131.76 1264.6 > 330.54 C

2. U7 U8 & U4 U5 1150 9598.2

8

131.76 1264.6 > 263.42 C

3. U3 U4 & U8 U9 1200 9598.2

8

131.70 1264.09 > 265.5 C

4. U U3 & U9 U10 1150 9598.2

8

131.76 1264.09 > 226.41 C

5. U1 U2 & U10 U11 1200 9598.2

8

131.7 1264.09 > 235. C

6. U0 U1 & U11 U12 2350 9598.2

8

129.4 1242.01 > 115.17 C

7. U0 L0 & U12 L8 1500 9598.2

8

130.0 1247.77 > 144.28 T

8. L4 L5 & L3 L4 2290 7884 135.6 1069.0 > 215.41 T

9. L5 L6 & L2 L3 2290 5913 135.6 801.80 > 178.84 T

10

.

L6 L7 & L1 L2 2290 5913 135.6 801.80 > 165.56 T

11

.

L7 L8 & L0 L1 2290 3942 135.6 534.5 > 124.95 T

12

.

L4 U6 2250 1508.0

6

135.6 204.5 > 101.13 T

13 L4 U 7 & L3 U 5 2400 1508.0

6

135.6 204.5 > 101.13 T

14 L5 U 7 & L3 U 5 2350 2235.6 131.08 293.04 > 80.92 C

15 L5 U 8 & L3 U 8 1850 1508 135.6 204.48 > 6.12 T

16 L5 U 9 & L3 U 3 2200 2235.6 135.6 303.06 > 86.65 T

17 L6 U 9 & L3 U 3 2100 2235.6 131.7 294.42 > 139.44 C

18 L6 U 10 & L2 U 2 1500 1508 135.6 204.4 > 35.7 T

19 L6 U 11 & L2 U 1 1700 2235.6 131.7 294.42 > 15.24 C

20 L1 U1 & L7 U 11 1650 2235.6 131.7 294.42 > 15.24 C

21 L1 U0 & L7 U 12 1150 2235.6 135.6 303.14 > 42.25 T

The member forces are not exceeding the maximum load

carrying capacity. Hence the bridge if feasible for I.R.C. class 'B' type of

loading.

CHAPTER – 5

ACCIDENT

The bridge has completed 100 years of its life time in 1973. The

British construction company which has constructed the bridge sent a

letter to Ahmednagar Collector, saying that last 100 years the bridge is

giving good service but then the guarantee period of the bridge is over

& better you should construct a new bridge. Further saying that the

contract of construction should be given to them.

When railway fly over on Nagar – Pune road was completed in

1980, permission was granted to construct a new bridge on river

Seena. Accordingly an alternative 100 m long R.C.C. bridge was

constructed in 1982. After this new bridge the old steel bridge was

used as secondary mode of transportation. To restrict heavy vehicles

to move from this bridge steel portal frames of 2m above G.L. were

provided.

Even after giving the precautionary warning given from time to

time by authorities that this bridge is dangerous to use any more

people did not stopped using it for heavy transportation. Few days ago

an unknown vehicle damaged the portal frame of the city end. Before

the notice was issued to repair this portal frame, at the night of 29 th

July 2002 between 12:30 to 01:00 a Volvo trailer carrying load of steel

– pipes, weighing about 70 Tones going from Chhatisgarh – Banglore

via Nagar.

Instead of going along R.C.C. bridge started going through the

old steel bridge. The weak bridge was not able to bear the heavy load

the bottom side of the 3rd section fractured & collapsed into the

riverbed.

Sr. No. Member Member force KN Carrying capacity KN

1. AB 346.92 C > 224.292. DE 183.9 C > 224.293. BC 337.37 C > 117.374. CD 278.45 C > 117.375. AH 373.74 T > 143.866. FE 198.0 T > 143.867. HG 348.84 T > 205.728. GF 244.74 T > 205.729. BH 137.76 C > 114.58

10. CG 31.22 C < 131.3711. DF 51.14 C < 114.5812. BG 10.16 C < 59.7313. CH 2.057 C < 55.4914. CF 64.87 C > 55.4915. DG 100.71 T > 59.73

The heavy sudden load due to depression exceeded the member

forces in the cross girder truss too much beyond the remaining load

carrying capacity.

Therefore the failure

Force Table :-

Sr

.

Member L mm A mm26 a

N/mm2

Safe load

KN

Max Member

force KN

1. U5 U6 & U6 U7 115

0

9598.2

8

131.76 1264.6 > 1101. 04

C

2. U7 U8 & U4 U5 115

0

9598.2

8

131.76 1264.6 > 1182.47

C

3. U3 U4 & U8 U9 120

0

9598.2

8

131.70 1264.09 > 1178.35

C

4. U2 U3 & U9 U10 115

0

9598.2

8

131.70 1264.6 > 1111.6 C

5. U1 U & U10 U11 120

0

9598.2

8

131.70 1264.09 > 1158.47

C

6. U0 U1 & U1 U12 235

0

9598.2

8

129.40 1242.01 > 672.75 C

7. U0L0&U12L8 150

0

9598.2

8

130.0 1247.77 > 821.42 C

8. L4 L5 & L3 L4 229

0

7884 135.6 1069.0 < 110.19 T

9. L5 L6 & L2 L3 229

0

5913 135.6 801.80 > 621.72 T

10

.

L6 L7 & L1 L2 229

0

5913 135.6 801.80 > 750 T

11

.

L7 L8 & L0 L1 229

0

3942 135.6 534.5 > 711.37 T

12

.

L4 U6 225

0

1508.0

6

135.6 204.5 < 378.6 T

13 L4 U 7 & L3 U 5 240

0

1117.8 135.6 151.57 > 663.13 T

14 L5 U 7 & L3 U 5 235 1117.8 131.08 146.52 > 371.78 C

0

15 L5 U 8 & L3 U 4 185

0

1508 135.6 204.48 > 25.46 C

16 L5 U 9 & L3 U 3 220

0

1117.8 135.6 151.57 < 547.8 T

17 L6 U 9 & L2 U 3 210

0

1117.8 131.7 147.21 < 664.72 C

18 L6 U 10 & L2 U 2 150

0

1508 135.6 204.4 > 199.06 T

19 L6 U 11 & L2 U 1 170

0

1117.8 135.6 151.57 < 669. T

20 L7 U11 & L1 U 1 165

0

1117.8 135.6 151.57 > 45.78 T

21 L7 U12 & L1 U 0 115

0

1117.8 135.6 151.57 < 199.05 T

The comparison between last two columns shows that some of

the member forces generated due to 70 tones of train of vehicle

loading are exceed in safe load capacity.

Conclusion of Failure Analysis

The analysis proves that the third bay of the bridge has suffered

accident due to the heavy load beyond its capacity as the bridge has

lost its initial strength due to corrosion through out the life span.

The bridge was not able to withstand the sudden loading of 70

Tones train of vehicles from which we can conclude that –

The depression on the carriage way provided the impact load

which was in multiple greater than sudden loading, first made the

failure of cross girder truss the debris of the cross girder truss shows

some of the members are broken due to which the whole section

suffered excessive bending. The bending enables the end portion of

the cross girder resting on the main girder to slip out of the slot from

one side of the bridge and the whole section came down providing

torque on the other side.

CHAPTER – 6

REMEDIES FOR THE DAMAGES

1) The deck is completely corroded even torned & has through holes.

The depression on carriage way makes water to percolate which

causes deterioration of the lime concrete. So the complete

renovation of the deck has to be done. Deck should replaced by

new one with thick and corrosion resistant material of sheeting or

the modern type of flat slab supported with stringers should be

provided.

2) The cross girders have suffered too much corrosion that we can

remove about 1 to 1.5 mm rust by simply scratching over the

surface which reduces the cross sectional area by about 10.68%

also the test results does not give satisfactory values as a structural

steel.

If we observe the gap between cross members of the cross

girder truss it has widened due to buckling of the compression

member which is indication of initial failure. If we provide

intermittent welding to make it as a joint it will reduce the effective

lengths of the members and the cross girders truss can be

strengthened.

3) The masonry construction of the abutment wall has becomes so

weak that the stones are getting loosed and the anchorage of the

main girder are slipped out of the abutment. Though the authorities

have provided I-section support at the abutment wall to

hold the main girder in position but it is not providing anchorage so

the reconstruction of the abutment wall has to be done.

4) The Pratt trusses and pier supports have not suffered much from

corrosion that even after accident they withstood intact in position

so they don't require any alterations only regular maintenance is

required like painting.

CHAPTER – 7

Why to Adopt Such Type of Bridge-Structures ?

1) As an attractive feature for tourist centre :-

a) If the bridge-structure get blended with attractive landscape for

example lawns , trees and footpaths. It can be attractive feature

harmonizing and adding dignity and beauty of the spot.

It is well said by 'Ruskin'

" All forms of beauty are composed

exclusively of curves ".

And this type of bridge has such characteristics of continuous

curvilinear from to create magnificent effect.

b) Light and shed determines the third dimensions of an object.

They also emphasize the colour and texture of the object. At

night lights can play dramatic role. It can become an attractive

element of expressions –

- For this if the bridge steel is provided with protective coating

of stain-less steel, the steel arches will start glittering to speak

their special qualities of Aesthetics & Architecture.

- So this bridge can become a main feature for a tourist

centre.

2) As a crossing remedy for a busy & fast road :-

Now a days many big cities require to provide cross-over bridges on

rush traffic road for pedestrians. If we provide such type of single

arch cross over bridge instead of foot over bridge it will improve the

urban beauty of the area.

3) As an everlasting conveyer :-

In this modern era civil engineering with improved techniques of

precast and prestressed bridges, steel bridges are not constructed

just because of the problem of corrosion. This can be solved by

using alloy steel (e.g. addition of some percentage of Nickel &

chromium with proper guidance of metallurgists) such improved

corrosion resistant steel structure can be proved as an everlasting

conveyer.

CONCLUSION

The observations shows that the bridge structure has lost its

capacity due to corrosion throughout its life span of 100 years. And

now after 130 years the analysis shows that still it is feasible to

withstand the loading of IRC class B that is it can be utilized for

transportation of routine vehicles within the city, if the suggested

alterations are done and regular maintenance is provided.

The analysis of the failure concludes that the 70 Tones vehicle

was already heavy beyond the feasible loading. And the impact load

due to the depression on the carriage way made the third bay of the

bridge to collapse in to the river.

REFERENCES

1) Steel Structures : By V.N. Vazirani &

M. M. Ratwani

2) Designs of Steel structures : By L. S. Negi

3) Theory of Structure : By S. Ramamrutham

4) Brief Investigation Report : By P.W.D. Ahmednagar

5) I.S. Code : 800 - 1984