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from 4740m/sec to 5060m/sec(Table 20). 5.2.2 As per IS-13311(Part-1)-1992 if the pulse velocity is above 4500 m/sec indicates “Excellent” quality grading of ...

INDEX SN

DESCRIPTION

PAGE NO. BRIDGE NO. 1474

1 2 3. 4 5. 6. 7. 1 2 3. 4 5. 6. 7. 1 2 3. 4 5. 6. 7.

Introduction Objective History of Bridges Tests conducted & Parameters observed Analysis of data Conclusion Recommendation BRIDGE NO. 1674 Introduction Objective History of Bridges Tests conducted & Parameters observed Analysis of data Conclusion Recommendation BRIDGE NO. T-7 Introduction Objective History of Bridges Tests conducted & Parameters observed Analysis of data Conclusion Recommendation

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NDT TESTING OF BRIDGE NO. 1474 PSC GIRDER NEAR MADURAI IN SOUTHERN RAILWAY 1.0

INTRODUCTION

1.1 The study was undertaken as per advise of CBE/SRly letter No. W71/W/277 dt. 8.01.03 1.2 The bridge no. 1474(15x21.34m) PSC girder was built over river Vaigai river near Madurai between the MDU-DG section of S.Rly. The spans of bridge having 4 nos. of ‘I girders each. 2.0

OBJECTIVES

2.1 Objectives of the testing was to ascertain reasons of the cracks and to recommend remedial measures. 3.0

HISTORY OF BRIDGE

3.1 The bridge was constructed in 1987 parallel to MG bridge for new BG line.. Both MG & BG lines (Bridges exists parallel to each other). 3.2

During the periodical bridge inspection on 4.3.2000 the crack was noticed.

3.3 Span No.3 – Both outer ‘I’ girder of the span having longitudinal hair cracks of about 15m at centre location at the bottom of girder. 3.4 Span no. 15 – Two longitudinal cracks on both outer girder of the span at bottom of the girder. In ‘I’ 1 girder the length of crack is about 14 m and 5m and in ‘I’ 4th girder the length piece about 15m and 16m at centre. The widths of the crack is about 1.5 to 2.0mm. The top of bottom sofit have longitudinal crack in entire length of girder in the west face of the girder. The tressel beam of pier no.8 have crack below bearing plate. The tressel beam of pier no. 12 also having crack. 4.0

TEST CONDUCTED AND PARAMETERS OBSERVED

4.1

Test were conducted to observe following parameters:

4.1.1 Corrosion of embeded steelThe corrosion monitoring of the structures was done by CANIN instrument. The corrosion monitoring was done on 4th girder of span no.15 west face and at bottom side and at center of bottom side of Ist and 3rd girder of span no. 15.

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4.1.2

Quality Of Concrete,

4.1.2.1 To measure the quality of concrete, the pulse velocity meter was used. Test by pulse velocity meter was conducted on bottom flange of 4th girder, 3rd girder and Ist girder of the span no.15. 4.2

Compressive Strength Of Concrete

To measure compressive strength of the concrete rebound hammer was used. The rebound hammer test was conducted for bottom side of 1st, 3rd and 4th girder of span no. 15 and side face of 3rd and 4th girder of span no.15..

5.0

ANALYSIS OF DATA

5.1

Corrosion monitoring by CANIN

5.1.1 The corrosion measurement was done by using CANIN Instrument. The grid area for recording was selected 20 cm x 20 cm each for effective area of corrosion. 5.1.2 4th Girder:- There was no corrosion activity taking place at west face of the girder no 4 of span no.15. The potential measured was more than -200mv, which indicates that there is a more than 90% probability that no corrosion is occurring in that area at the time of measurement ( Table 1 to 8 ). 5.1.3 On the bottom side of the girder no.4 of span no. 15 at the distance of 4.6m and from 10.8 to 11.8m from DG end the recorded potential is between the range of -200mv to -350mv which indicate that at these places corrosion activity is uncertain (Table 9 to 15). 5.1.4 3rd Girder:- On 3rd girder the recording of potential is done from 9.1m to 12.3m from DG end at bottom side of the girder. Values of potential are positive which indicates that there is no corrosion (Table 16). 5.1.5 Ist girder:On 1st girder the recording of potential is done from 9.1m to 12.3m from DG end at bottom the corrosion potential recorded varies from -125mv to -55mv which indicate that corrosion activity not taking place (Table 17 ). 5.2

Quality Of Concrete,

5.2.1 The pulse velocity measurement was recorded on the girder no. 4,3 & 1 of span no.15 at bottom flange. The pulse velocity recorded at 14 locations on bottom flange of the 4th girder and velocity recorded in the range of 4750m/sec to 5240m/ sec ( Table 18).On the bottom flange of 3rd girder the pulse velocity varies from 4520 m/sec to 4820m/sec Table 19 on the bottom flange of Ist girder the velocities varies from 4740m/sec to 5060m/sec(Table 20). 5.2.2 As per IS-13311(Part-1)-1992 if the pulse velocity is above 4500 m/sec indicates “Excellent” quality grading of concrete. 2

5.3

Compressive Strength Of Concrete

5.3.1 The rebound hammer test was conducted to know the compressive strength of the concrete. The rebound hammer recording was done on 4th girder on west face and bottom side, on 3rd girder on west face and bottom side, on Ist girder on west face and bottom side. 5.3.2 Except few values of rebound hammer recorded on the girder of span no 15 all values are above 55. In the manual of rebound hammer upto rebound no.55 the corresponding compressive strength of concrete is given which is 61.0 N/mm2 In case of horizontal position of rebound hammer during recording. In case of vertical upward position of rebound hammer the rebound no.55 is equivalent to 63.0 N/mm2

6.0

CONCLUSION

6.1 If the corrosion meter results are seen then it appears that at the bottom of 4th girder of span no. 15 at a distance of 10.8m to 11.8m from Dindigul (DG) end corrosion is uncertain. If results of pulse velocity meter and rebound hammer values are correlated then it appears that corrosion is either not occurring or if occurring then it must be at very much primitive stage hence corrosion does not appears to be the reason for the cracks.. 6.2 At other test locations no corrosion activity appears to be taking place at the time of recording. The pulse test meter indicates that the quality of concrete appears to be very good. 7.0

RECOMMENDATIONS

7.1 It appears that such cracks may be simple plastic shrinkage cracks which occurs due to congestion of reinforcement or improper compaction. 7.2 It is recommended that for the time being the cracks can be grouted by epoxy and kept under watch. There after, the performance may be reported back to RDSO for further study. 7.3 Since corrosion does not appear to be the probable reason of the crack, the activeness of crack also need to be checked by some other equipment like Acoustic Emission Technique (AET). But before going for further advance testing, the design of the girder, load testing history if any, otherwise deflection of girder under load need to be examined and measured than the deflection shall be correlated with the designed deflection.

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II

BRIDGE NO. T-7 BETWEEN YANCHI MANIYANCHI - TUTICORIN

1.0

INTRODUCTION

1.1 The study was taken as per letter No. W/71/U/277 dt. 8.1.2003 from CB/SR, who also indicated the probable cause of crack may be corrosion of reinforcement. 1.2 The bridge no. T-7 (6x7.5m skew RCC slab) was built in the year 1984 for the new BG line between Yanchi Maniyachi – Tuticorin section of Madurai Division of S.Rly. The super structure consist of 6x7.5m skew RCC slab. The traffic was allowed in the year 1990-91 over the bridge. 2.0

OBJECTIVES

2.1 Objectives of the testing was to ascertain reasons of the cracks and to recommend remedial measures. 3.0

HISTORY OF BRIDGE

3.1 The cracks on the piers were noticed oh 7.5.02 during the inspection of Sr.DEN South/MDU. 3.2 The column of the pier having hair cracks and most of the cracks are upto the height of 1 to 1.5m from ground level. Hollow sound is produced when hammered by small hammer on columns at isolated locations. ƒ ƒ ƒ ƒ ƒ

Pier No1. Hair cracks in columns Pier No.2 cracks in column Pier no.3 Columns having vertical cracks and tressel beam also having cracks. Pier No.4 Columns having cracks Pier No.5 columns having cracks.

3.3 Due to circumferential cracks in columns of pier no.3 the tressel beam was supported by CC cribs, to avoid shear failure.

4.0

TEST CONDUCTED & PARAMETERS OBSERVED

4.1

Tests were conducted to observe following parameters:

4.1.1 Corrosion - The corrosion monitoring of the structure was done by CANIN Instruments. The corrosion monitoring was done on tressel beam and columns of pier no.3.

4.1.2 Quality of Concrete 4

4.1.2.1 To measure the quality of concrete the pulse velocity meter was used. Pulse velocity test was conducted on the columns of pier no.1 and pier no.3 4.1.2.2 Compressive Strength of Concrete 4.1.2.3 To measure compressive strength of the concrete, rebound hammer was used. The rebound hammer test was conducted on the tressel beam and columns of pier no.3 and columns of pier no.1 5.0

ANALYSIS OF DATA

5.1

Corrosion Monitoring by CANIN

5.1.1 The grid area was selected 20cmx20cm each for effective area of corrosion. The corrosion monitoring was done on pier no.3. 5.1.2 Tressel beam of pier no.3 - The monitoring of tressel beam was done in the area of 60cm x 3.20m by dividing area x the grid of 20cm x 20cm. The corrosion potential recorded was -55mv to -220mv in all the area. In one grid of area of 20cm x 20 cm the corrosion potential was between -200mv to -250mv which indicates the transient phase and or the corrosion activity is uncertain. (Table 1). 5.1.3 North Column of pier no.3 – The corrosion monitoring of north column of pier no.3 was done from 10cm from top of column and upto 2.5m in whole circumference in the width of 20cmx20cm. 5.1.4 At the upper half area the corrosion potential varies from -200mv to positive value which indicates that corrosion activity at that area not taking place. 5.1.5 At the lower half area scanned the corrosion potential varies between -250mv to less than -450mv. Area where corrosion activity un certain the corrosion potential varies between -200mv to -350mv and the area having corrosion potential less than -350mv indicates that at that area corrosion occurring positively (Table 2). 5.1.6 South Column of pier no.3 - The corrosion monitoring of south column of pier no.3 was done from 1m from top of column upto 3m in whole circumference in the grid of 20x20cm. In the scanned area from 1m to 1.6m the corrosion potential recorded positive which indicate no corrosion. In the distance of 1.6m to 3.0m the corrosion potential was less than -350mv which indicates corrosion occurring positively at that area (Table 3).

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5.2

Quality of Concrete

5.2.1 Pier No.1 – Pulse velocity recording was done at five locations on north columns and at five locations of south column. On north column the pulse velocity recorded was varies between 400m/sec to 1590m/sec. On the south column the pulse velocity was varies between 1920m/sec to 4110m/sec. at on locations no.7 no recording done by instrument( Table 4) . 5.2.2 Pier No.3 - Pulse velocity recording was done at seven locations on north column and six locations on south column. On north column the pulse velocity varies from 260m/sec to 1720m/sec. On south column the pulse velocity varies from 400m/sec to 1580m /sec. At one location no recording was recorded by instrument (Table 5). 5.2.3 As per IS13311(Part-I):1992 the concrete quality divided in 4 categories in terms of pulse velocity. SN 1 2 3 4

Pulse velocity(KM/sec) Above 4.5 3.5 to 4.5 3.0 to 3.5 Below 3.0

Concrete quality grading Excellent Good Medium Doubtful

5.2.4 As per specification in case of “Doubtful” quality of concrete it may be necessary to carry out further tests. 5.3 Compressive Strength 5.3.1 The rebound hammer test was conducted to know that the compressive strength of concrete. 5.3.2 Pier no.1 - The rebound hammer recording was done at 12 locations on north column and at 12 locations on south column. The compressive strength varies from 17.5N/mm2 to 25.1N/mm2. Average strength was 21.76 N/mm2 (Table 6). On South column the compressive strength was varies from 20.5n/mm2 to 30.1N/mm2 Average compressive strength was 26.8 N/mm2 ( Table 7). 5.3.3 Pier no.3The rebound hammer test was conducted on north and south column pier and at tressell beam of pier. 5.3.4 At tressell beam rebound hammer recording was done on 18 locations on face towards Yanchi Maniyanch and on 18 locations face towards Tuticorin. On the face towards Yanchi Maniyanch compressive strength varies from 30.1N/mm2 to 48.0N/mm2 (Table 8) and average value of compressive strength is 37.35 N/mm2 and on the face towards tuticorin the compressive strength varies from 30.1m2. to 51.0 N/mm2 (Table 9). And average value is 38.6N/mm2. On the north column

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5.3.5 compressive strength varies from 13.2 n/mm2 to 26.8N/mm2 (Table-10) and average value is 18.1N/mm2. On the South column compressive strength varies from 14.6N/mm2 to 30.1N/mm2 ( Table 11)and average value is 17.89 N/mm2.

6 CONCLUSION 6.1 The pulse velocity meter recording at most of the places indicates that the quality of concrete is poor & in doubtful category. 6.2 Both columns of piers no.3 having corrosion positively at the lower side beginning from the middle. At the top of the tressel beam corrosion activities not taking place. The results shows that quality of concrete is poor and same might have triggered the corrosion, so strength of the structure has to be reassessed, based on the test results. 7.0

RECOMMENDATIONS

7.1 Checking of design calculation should be done based on the test results however chemical analysis of the spalled concrete can also be done to know the composition of concrete. 7.2 Strengthening measures like jacketing of sub structures shall be done immediately to restore full traffic potential & than the structure shall be kept under watch, there after the feed back shall be sent to RDSO, for further analysis.

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III

BRIDGE No. 1674 BETWEEN YANCHIMANIYANCHI – TIRUNEVELI IN MADURAI DIVISION OF SOUTHERN RAILWAY

1.0

INTRODUCTION

1.1 The study was undertaken as per letter No. W/71/U/277 dt. 8.1.2003 from CB/SR, who also indicated the probable cause of crack is corrosion of reinforcement. 1.2 The bridge no. 1674 (20x10.0m plate girder) was built in the year 1983 for BG line between Yanchimaniyanci-Tirunaveli sec of Southern Railway. The super structure consist of 20x10.0m plate girder. The sub structure consist of Twin RCC column with tressel beam on well foundation. 2.0

OBJECTIVES

2.1 Objectives of the testing was to ascertain reasons of the cracks and to recommend remedial measures. 3.0

HISTORY OF PROBLEM

3.1 The cracks on the piers was noticed during the inspection of CBE/SRly on 25.10.2000. 3.2 Pier No.1 having circumferential crack. Crack surface gives hollow sound on hammering by hammer. Honey combing of concrete also visible. Similar type of defect also exists on pier no.18. Cracks in other piers also exists and at some locations honey combing also visible.

4.0

TEST CONDUCTED & PARAMETERS OBSERVED

4.1

Tests were conducted to observe following parameters.

4.1.1 Corrosion - The corrosion monitoring of the structure was done by CANIN instrument. The corrosion monitoring was done on pier no.1 on the column. 4.1.2. Compressive Strength Of Concrete - To measure compressive strength of the concrete rebound hammer was used. The rebound hammer test was conducted on both column of pier no. 1 and on top of tressel beam of pier no.1. 5.0

ANALYSIS OF DATA

5.1

Corrosion Monitoring by CANIN

5.1.1 The corrosion measurement was done by using CANIN instrument. The grid area for recording was selected 20cmx20cm each for effective area of corrosion. The corrosion monitoring was done on left and right column starting from 40cm and 8

50cm below from top of column and at the broken cover of concrete where bar was exposed for connection of lead of CANIN instrument. 5.1.2 In the left column Table 1 the corrosion potential recorded are positive in about half area and the corrosion potential is between – 200mv to -50mv in about nearly half area monitored, all this values of corrosion potential indicates that no corrosion activity taking place . In 16 grid area of 20cm x 20cm the corrosion potential recorded is below -200mv which indicates that over this area corrosion activities are uncertain. 5.1.3 At the place of broken concrete cover for exposing the bar and surrounding area the recorded corrosion potential is greater than -200mv which indicates corrosion activity not taking place over that area (Table-2). positive 5.1.4 On the right column of pier about 1/4th monitored area gives positive potential and rest area recorded corrosion potential above -200mv which indicates that no corrosion activity is taking place. 5.2

Compressive Strength

5.2.1 The rebound hammer test was conducted to know the compressive strength of the concrete. The rebound hammer test conducted on both column and top of tressel beam of pier no. 1. 5.2.2 Right column The rebound hammer test conducted at 12 location on right column of pier no.1. The compressive strength varies from 23.5N/mm2 to 30.0N/mm2 (Table 6) and average value is 26.8 N/mm2. 5.2.3 Left Column At 12 location rebound hammer recording was done. The compressive strength varies from 23.5N/mm2 to 40.6N/mm2 ( Table 7) and average value is 32.49 N/mm2. 5.4 Top of tressel beam The rebound hammer recording was done at 21 locations each on both faces of the tressel beam. On the face towards Yanchiminyachi the compressive strength varies from 48.0N/mm2 to 61.0N/mm2 (Table 4) and average value is 56.14 N/mm2 and on the face towards Tiruneveli the compressive strength varies from 48.0 N/mm2 to 61.0N/mm2 (Table 5) and average value is 26.8 N/mm2. 6.0

CONCLUSION

6.1 On right column corrosion activity not taking place. On left column at some area, corrosion activities are uncertained

7.0

RECOMMENDATIONS

7.1 The cracks may simply be grouted and shall be kept under observation. There after feed back shall be given to RDSO for repetition of tests, if necessary. 9