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UNDER WATER INSPECTION OF BRIDGES

UNDER WATER INSPECTION OF BRIDGES. VINEET GUPTA SPB-1. KADALUNDI TRAIN MISHAP Calicut – Shoranur Section of Palghat Division on 22-6-2001 due to failure of pile. KADALUNDI TRAIN MISHAP. Br. No. 924 Span 12X 19.51 m steel girders Bridge sub structure built in 1861

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UNDER WATER INSPECTION OF BRIDGES

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  1. UNDER WATER INSPECTION OF BRIDGES VINEET GUPTA SPB-1

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

  3. 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

  4. BRIDGE INSPECTION SYSTEMATIC OBSERVATION OF CONDITION AND BEHAVIOUR OF VARIOUS COMPONENETS/ PARTS OF A BRIDGE IS CALLED BRIDGE INSPECTION UNDERWATER PORTION OF BRIDGE IS ALSO A COMPONENT TO BE INSPECTED

  5. Frequency Of Under Water Routine & Detail Inspections • Intervals between scheduled inspections depend on: • The condition of the riverbed (hard rock / sand / mud…) • The amount and speed of water flow • The aggressiveness of the water (steel structures or reinforced concrete structures in salt water call for attention) • The condition and “sturdiness” of the structures • No fixed rules for intervals, only: should never exceed 5 years

  6. Unscheduled Under Water Inspection • After unusual floods • After vessel impact • Build-up of debris at piers and abutments • Settlements or other evidence of scour

  7. 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.

  8. Indian Roads CongressSP 35 - Guidelines for Inspection and maintenance of Bridges - Clause 3.5.3 • Visual examination of the surface may be done by minimum cleaning to remove marine growth • Detailed inspection for obtaining more information of deteriorated areas • special investigation shall be carried out which shall utilize selected non destructive methods. • should be entrusted to only competent agencies experienced in underwater inspection. • Close circuit TV should be used where the water is clear • Portable echo sounding equipment can be used where visibility is poor

  9. ONGC Offshore Structures Inspection, Maintenance and Repair methodologies – • Categories of Inspection • Level I - above water • Level II - underwater visual survey • Level III - detailed underwater visual survey with cleaning performed at regular intervals • Level IV - underwater NDT survey of pre-selected areas.

  10. UNDERWATER INSPECTION OF BRIDGES • Methods of Underwater Inspection • Defects to be looked for • Concrete • Steel • Masonry • Intensity Level of Inspection • Types of Inspection • Bridge Selection Criteria • Planning an Underwater Inspection • Documentation

  11. Methods of Underwater Inspection • Wading Inspection – substructure units and waterway are evaluated using a probing rod, sounding rod, hammers, picks etc. (Not Underwater in strict sense) • 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.

  12. 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

  13. Surface supplied air diving • Surface air compressor tank • Suited in adverse conditions • Jack Brown mask • 60 min at 18 m • 30 min at 27 m • MK1 mask • 10 min at 40 m • unlimited up to 18m • Nitrox and heliox gases for longer and deeper dives

  14. Surface supplied air diving • Advantages • Long deed dives • Unlimited air supply • Safe line attached- one diver is sufficient • Better in high velocity/ turbid water • Disadvantages • Large size operation. Boat, air compressor, hoses & lines are reqd.

  15. S.No. Equipment Use Photograph 1 Kirby Morgan Band Helmet Enables uninterrupted breathing & communication over radio. 2 Diving Mask Protects the eyes from current for good view. 3 L.P. Compressor For supply of air 4 Air Filter To filter moisture from air supplied by compressor 5 Umbilical Air pipe connecting the air filter and KMB helmet. 6 Underwater Camera To shoot the proceedings of inspection. 7 Radio Equipment Enables to communicate with the diver. 8 CCTV Set. Enables watching the proceedings from shore.

  16. Other equipment • Boats with oars, motor and life preservers, if required • Inspection documents, paper, clip board and pencils etc. • Concrete or steel tool kit, depending upon type of piers/abutments to be inspected. • Sounding equipment and marking pencils, if required, to determine scour. • Safety Equipment

  17. QUALIFICATION OF DIVERS AND SUPERVISORS • IS 10291-1982 LAYS DOWN • MINIMUM AGE 18 YEARS • FITNESS BY DOCTOR IN LAST SIX MONTHS • FITNESS TESTED FOR WORK AT REQUIRED DEPTH OR EQUIVALENT PRESSURE IN COMPRESSION CHAMBER • KNOWLEDGE OF DIVING SIGNALS • TRAINED FOR WORK IN NO VISIBILITY CONDITIONS • GOOD PHISIQUE, CAPABLE OF SUSTAINING STRAIN • FREE FROM CARDIAC PROBLEM • FREE FROM MID EAR PROBLEM ETC • NOT ADDICTED TO ALCOHOL AND EXCESS SMOKING • NOT MORE THAN 45 YEARS FOR DEEP DIVING

  18. SAFETY - General safety precautions • Make sure that each diving operation is thoroughly planned in advance and properly supervised • All diving personnel must be thoroughly trained in the equipment being used and physically fit for diving operation • Equipment must be first quality and thoroughly tested and inspected before use

  19. SAFETY MANUAL • The working agency should have its own diving safety manual and this manual should include • Safety procedures and checklists for diving operations • Assignments and responsibilities of dive team members • Equipment procedures and checklists • Emergency procedures for equipment failures, adverse environmental conditions and diver illness or injury

  20. Structural Deficiencies • Settlements and displacements of piers and abutments because of scour. • Structural damage to piles and piers causedby overload, impact of debris, logs etc. or by ship impact. • Structural damage because ofinadequate design or poor workmanship. • Deterioration of materials Eccentricity in pile bent

  21. Defects • Scaling-Gradual and continuous loss of surface material • Cracking • Spalling-circular or oval falling out of material • Disintegration-small pieces falling out • Abrasion • Cavitation-collapse of vapour bubbles

  22. Material Defects - Concrete • 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

  23. Material Defects - Steel Steel structures are highly susceptible to corrosion particularly in low water areas.Wherever possible thickness of steel should be measured to determine if section loss has occurred.

  24. Relevant Damage Types Material Defects - Steel Corrosion is worst: • primary in the splash zone (ample supply of water and oxygen) • secondary right below the mean low water

  25. Material Defects - Steel • Abrasion • Exposure to wave actions in areas with a sandy bottom. • Overloading • Impact / collision • Compression overloading damage.

  26. Defects- Masonry • Erosion of masonry structures is mainly caused by • Particles in flowing water (and wind) • Wash out of the joints • Falling of bricks/stones • Frost attacks • Salt crystallization • Plant root action • Increased earth or hydrostatic pressure • Scouring at the base because of wave and current actions

  27. Anaerobic bacterial growth

  28. Spalling

  29. scaling

  30. Abrasion

  31. disintegration

  32. cavitation

  33. GENERAL • Depth is inversely proportional to effective Diving time. • Upto 30m normal diving conditions apply. • Beyond 30m – Diving with High precision. • More Turbidity means less Visibility. • Less Visibility - Diver Unable to Assess Visually • Clear water box can help • 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.

  34. Inspection Intensity Levels • Level I • 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 Level II or Level III.

  35. Inspection Intensity Levels Level II • Requires that portions be cleaned. • Intended to detect and identify damaged and deteriorated areas hidden by surface growth. • Normally cleaning restricted to critical areas – near low water line, near mud line and midway between the low water line and mud line. • About 30 cm bands are cleaned and observed.

  36. Level II Where to clean surfaces for closer inspection • Piles: • 25-30 cm high bands • ¾ of the perimeter • in 3 different levels • Splash zone (low waterline) • Mudline (bottom of river) • Midway between low waterline and mudline • Concentrate on damaged and suspicious areas, but also include apparently undamaged areas

  37. Inspection Intensity Levels contd.. • Level III • Highly detailed inspection • To detect hidden or interior damage and loss in X area. • Involves extensive cleaning, detailed measurements • NDT &/or partially destructive techniques. • Basically for a member where extensive repair or possible replacement is contemplated.

  38. Non –destructive tests • Rebound hammer • Magnetic rebar locator • Ultrasonic testing • Ultrasonic thickness meters • Frequency 3-5 Mhz for steel • 20 – 250 KHz for concrete • Not suitable for cast iron

  39. Non –destructive tests • Echo sounders • Magnetic particle examination • Radiography • Corrosion analyzing equipment

  40. Levels of Under Water Inspection References • FHWA-DP-80-01, Underwater Inspection of Bridges, US Department of Transportation, Federal Highway Administration, November 1989(Basis for the inspections to be performed for Indian Railways) • FHWA-DP-98-01, Underwater evaluation and repair of bridge components, US Department of Transportation, Federal Highway Administration, November 1995. • Shawn, K., “Underwater Inspection Criteria”, Naval Facilities Engineering Service Center, 1999.

  41. Bridge Selection Criteria • A bridge must receive routine underwater inspection maximum within 5 yrs. More frequent inspections may be desirable based on - • Age • Type of construction materials • Configuration of substructure

  42. Bridge Selection Criteria contd.. • Susceptibility of streambed material to scour • Maintenance history • Saltwater environment • Waterway pollution • Damage due to waterborne traffic, debris etc.

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