UNDER WATER INSPECTION OF BRIDGES

1. UNDER WATER INSPECTION OF BRIDGES

2. UNDER WATER INSPECTION OF BRIDGES • References • IRBM • RDSO report no BS-96 on UWI • IRICEN book on “Under Water Inspections” • RDSO report no BS-48 on NDT

3. KADALUNDI TRAIN MISHAPCalicut – Shoranur Section of Palghat Division on 22-6-2001 due to failure of pile

4. KADALUNDI TRAIN MISHAP • Br. No. 924 • Span 12X 19.51 m steel girders • Bridge sub structure built in 1861 • Train involved-6602 Manglore – Chennai Exp • Dead 52 • Grievously Injured 105 • Cause • Collapse of screw pile of pier no. 3 • CI pile thickness reduced to 6 mm from original 28 mm • Density reduced to 2.5 from 7.5 gm/cm3

5. BRIDGE INSPECTION • Systematic observation of condition and behaviour of various components/ parts of a bridge is called bridge inspection • Underwater portion of bridge is also a component to be inspected

6. Indian Railways Bridge Manual • Clause 102 - AEN to inspect once a year, by a date specified by Chief Engineer after monsoon - this inspection shall include foundation, flooring and substructure • Clause 1107(d) – The substructure of the bridges which are normally under water should be inspected by adopting suitable methods which may include engaging of divers and special equipment. [Old]

7. Schedule of inspections Para 1107 (d) New as per CS 21 • The sub-structure of the bridges which are normally under water should be inspected by adopting suitable methods which may include engaging of divers and special equipments: (i) Routine/swim by inspection should be done once a year (ii) Detailed inspection should be done once in five years. (iii) Special inspection- as considered necessary” 

8. Inspection Levels (BS – 96) Routine Inspection or Level I inspection • Visual, tactile inspection. Swim by. Any obvious major damage or deterioration should be detected. • Conducted over 100% exterior surface of each underwater element. • Can indicate the need for detailed inspection • To be done once every year

9. Routine inspection Visual Inspection or swim by inspection to be done by experienced diver • Water depth sounding and scour around piers and abutments. • Verification of the continuity of the piers in full length. • Registration of spalling. • Registration of corrosion. • Registration of cracks larger than 0.2mm. • Registration of severe damage in general.

10. Report for Routine inspection • Method and extent of investigation • Background material • Recording of deficiencies/important aspects requiring notice of higher authority • Assign condition rating number of the underwater bridge components. • Need for further inspections (Level II or III) – if required • Photos and video recordings(Not mandatory). • Specific requirement, if any, for photo/video recording should be ascertained by Chief Bridge Engineer of the Railway.

11. Detailed Inspection or Level II inspection • More detailed and directed towards obtaining limited measurements of damaged or deteriorated areas • Detail Inspection to be done on those structures where problems have been identified/ encountered during Routine or level I Inspection OR Once in five years. • If damage is there, level III inspection may be required • Sectional Sr.DEN/DEN should ascertain the necessity of carrying out Level III inspection

12. Detailed Inspection • Marine growth needs to be cleaned for surface inspection • Cleaning is restricted to sample areas of the entire underwater structures. • Damage should be measured and the extent and severity of the damage should be documented. • Cleaning for inspections • Bands for cleaning of piers and abutments should be approximately 30 cm wide • Cleaning of the substructure components is to be performed in three different water depths

13. Detailed Inspection • Cleaning for inspections Contd.. • Bands shall normally be located in the splash zone (low waterline), the mud line (bottom of river) and at construction joints or other structural details. • If no joints exist the area could be placed mid-way between the low waterline and mud line. • Thoroughness of cleaning should be governed by what is necessary to identify the condition of the underlying material. • Water jet cleaning equipment may be used if necessary

14. Detailed Inspection : Results • Registration of spalling. • Registration of corrosion. • Registration of cracks. • Registration of severe damage in general.

15. Detailed Inspection : Report • Photos and video recordings to be taken • Method and extent of investigation. • Background material. • Recording of Deficiencies/important aspects requiring notice of higher authority • Assign condition rating number of the underwater bridge components • Need for further inspections (Level III) – if required

16. Special or Level III Inspection • After unusual floods. • After vessel impact (unless it is obvious that no damage has occurred). • Build-up of debris at piers and abutments (horizontal forces on the structures and scour because of reduced cross section of the river). • Unusual prop wash from vessels. • In case of settlements or other evidence of excessive scour. • As a result of Level I/II inspections

17. Special or Level III Inspection • Highly detailed inspection to detect hidden or interior damage and loss in cross sectional area. • This involves extensive cleaning, detailed measurements, selected NDT &/or partially destructive techniques. • Basically for a member where extensive repair or possible replacement is contemplated.

18. Special Inspection • Planned using information from • Drawings, • Previous underwater inspections of this bridge • Underwater inspections of similar bridges • Knowledge and experience • A “hypothesis” concerning the cause of damage, the total damaged area and the condition of the damaged area may be formulated.

19. Special Inspection • If the test results do not confirm the hypothesis regarding the cause of damage, the hypothesis must be revised. • Perform supplementary tests to confirm the revised hypothesis. • Inspection must be sufficient to determine need for • Speed Restrictions OR • Closure of bridge to traffic and • To assess the Level of effort necessary to repair the damage • Must give section loss, misalignment of members, and loss of foundation support etc

20. Non –destructive tests • Equipment and calibration different from normal NDT • Ultrasonic Thickness Gauge - Steel • Ultrasonic Testing - Concrete and steel • Cover-meter – Concrete • Schmidt Hammer - Concrete and masonry • Chloride Content - Concrete • Coring Equipment - Concrete and masonry • Evaluation of Concrete Cores – Concrete • Crack Measuring Gauge - Concrete and masonry • Impulse Response Equipment – Concrete • Impact-Echo Equipment - Concrete and masonry • Half-Cell Potential – Concrete

21. Other issues • Level I and II inspections to be done in presence of AEN and report to be sent to SrDEN • Level III inspections to be done in presence of SrDEN and report to be sent to CBE • List of agencies for Under water Inspections given in Annexure I of the report BS-96 (20 agencies) • Only indicative and can choose other agencies from market also

22. Limitation of underwater inspection • During heavy scour there is high velocity of water and divers can not operate and when velocity is low, cavity is refilled. • Some underwater portion of structures exposed during some part of year cannot be inspected by the present methods • This is serious limitation specially in case of alluvial soils

23. What to see in UWI: General • Tilting • Permanent deformations (Settlement/ bulging) • Abnormal vibrations • Material defects

24. What to see in UWI: Concrete • Spalling • Sulphate Attack • reaction of magnesium sulphate with tricalcium sillicate • Chlorides- attacks steel • Alkali aggregate reaction • Alkali in cement reacts with minerals in certain aggregates • Honeycombing • Effects of Contaminants

25. What to see in UWI: Steel • Corrosion particularly in low water areas • Cracks • Impact damage • Loose connections etc

26. What to see in UWI: Masonry • Washout of joints • Cracks in joints • Weathering of masonry • Debonding of bricks/ stone pieces forming cavity • Deterioration of stones/ joints • Impact damage etc

27. Anaerobic bacterial growth

28. Spalling

29. Scaling

30. Disintegration

31. Cavitation

33. Planning an Underwater Inspection • Factors to be considered – • Type of Inspection • Method of underwater inspection • Inspection Level • Qualification of divers Inspectors available • Its possible that different levels may be required at various locations on the same bridge. • Compare inspection results of homogeneous areas • e.g. similar chloride content, depth from water level etc

34. IMPORTANT POINTS • Divide the periphery into equal intervals– Chainages. • Give notations to the chainages. • Entire surface is divided in equal grids. • Drop a Wire rope with weight as guide line. • Diver descends along the chainage covering each grid. • Distresses shall be located & measured grid wise.

35. B C A D E H G F Record Keeping and Documentation 1 1 HWL C A B D 2 3 E F G H 4 PIER 5 6 7 LWL 8 9 10 MUD LEVEL WELL

36. Inspection of a pile in a spiral motion

37. Methods of Underwater Inspection • Wading Inspection – substructure units and waterway are evaluated using a probing rod, sounding rod, hammers, picks etc. • SCUBA Diving – Self Contained Underwater Breathing Apparatus • Hard Hat Diving – uses a body suit, a hard hat helmet covering the head and a surface supplied air system.

39. Scuba diving • Weighs about 30 kg • 1 hour at 18 m • 10 minutes at 36 m • As depth increases, diving time decreases • One tank holds about 2m3 of air • At least 3 divers required • No communication with std. Equipment • Communication possible with scuba full mask • Full mask gives protection against cold and contaminated water

40. Surface Supplied Air Diving or Hard Hat Diving

41. Surface Supplied Air Diving or Hard Hat Diving • Surface air compressor tank • Suited in adverse conditions • Jack Brown mask • 60 mts at 18 m • 30 mts at 27 m • MK1 mask • 10 mts at 40 m • unlimited up to 18m • Nitrox and heliox gases for longer and deeper dives

43. Surface supplied air diving • Advantages • Long duration dives • Unlimited air supply • Safety line attached • Better in high velocity/ turbid water • Disadvantages • Large size operation. Boat, air compressor, hoses & lines are reqd.

46. GENERAL • Most of the Inspection using Touch & Feel. • Most of the assessment through CCTV system • Needs to communicate with diver continuously. • Calls for experience Divers. • Surface Crew needs to be Patient.

47. Record Keeping and Documentation • On site, recording of all conditions is essential • Sketches in detail • Logs describing the inspection • Tape recording the divers observation when significant damage is observed • Underwater photographs • Underwater Videotapes

48. Equipment for inspection

49. Operate in 0 lux light conditions • Self contained unit or one with control and monitor at tope • 5 MPx • 10 x Optical Zoom • Wide lens • Use of clear water box and suitable lighting, if required