SurfZone Eng. Info. Hub

Pile Inspection

Timber Pile Repair

Timber Piling issues and problems

  • Age
  • Stream Bed Degradation
  • Reduced Pile Cross Section
  • Cap Condition

Repair Method

  • Attach steel channels to timber piles using through bolts or lag bolts as shown
  • Addition of Reinforced Concrete Jackets to Piles
  • Encapsulation of Pile Groups
  • Posting/Splicing

Addition of steel sisters for pile reinforcement (Manual for Repairs of Timber Bridges in Minnesota, Minnesota Department of Transportation)

Addition of Pile Jackets (Manual for Repairs of Timber Bridges in Minnesota, Minnesota Department of Transportation)

Pile encapsulation at abutment (Manual for Repairs of Timber Bridges in Minnesota, Minnesota Department of Transportation)

Posted piles using steel W shapes (Dahlberg et al. 2012 )

UNDERWATER INSPECTION Levels (Underwater Bridge Inspection; Publication number: FHWA-NHI-10-027 )

  • Level I : Visual, tactile inspection
  • Level II : Detailed inspection with partial cleaning
  • Level III : Highly detailed inspection with Non-Destructive Testing (NDT) or Partially Destructive Testing (PDT)

Defect Documentation

Divers will note any defects during an underwater inspection

  • Scour
  • Exposed footings
  • Voids in substructure
  • Undermining
  • Decay/Section Loss
  • Cracks

UNDERWATER ELEMENTS

The following are guidelines for areas of concern during underwater inspections.

Footing or Foundations

  1. Type
    • Spread
    • Pile supported
  2. Material
    • Concrete
    • Timber cribbing
    • Stone masonry
  3. Condition
    • Timber
        • Decay
        • Marine borer attack
    • Concrete
        • Deterioration
        • Cracking (location and size)
    • Stone Masonry
        • Check for missing stones
        • Measure depth of penetration between stones if mortar is missing
        • Check for significant cracks
        • Check for misalignment or displacement
        • Check for signs of settlement

4. Exposed dimensions

    • Location (stations)
        • Exposed length
        • Exposed height
        • Offset from abutment or pier stem (toe)

5. Covered footing

      • Probe, dig, etc. to determine the bottom of footing

Scour

1. Indicate location and depth

2. Define limits with soundings

3. Soil deposition

      • Location
      • Height

4. Elevation of water during flooding noted by:

      • Discoloration of concrete
      • Debris deposited on bridge seats

Undermining

  1. Dimensions (L x H x Pen.)
  2. Location

Sheeting

  1. Type
      • Steel
      • Timber
  2. Condition
  3. Height of exposure above footing or mudline
  4. Thickness
  5. Measure one section of sheeting to determine size and shape
  6. Measure offset from abutment or pierwall
  7. Measure any separation from footing

Piles

  1. Type
      • Vertical
      • Battered
  2. Material
      • Timber
      • Concrete
      • Steel (concrete filled)
  3. Condition
      • Timber piles
          • Inspect for marine borer activity
          • Inspect bolt connections for corrosion
          • Probe wood to detect decay
          • Take caliper measurement to document section loss
          • Inspect for other deterioration, delamination
          • Locate and measure size of any splits or checks
          • Core a sample of wood pile (if necessary)
      • Concrete piles
          • Determine condition of concrete
          • Measure cross-sectional loss
          • Check for erosion of concrete and spalls
          • Check condition of any protective jackets
          • Check for exposed reinforcement
          • Check for cracks
          • Inspect for abrasion or delamination
      • Steel piles
          • Check for collision damage
          • Measure cross-section loss
          • Inspect for deterioration
          • Inspect the condition of any protective jackets
      • Collision Damage
          • Inspect for broken piles
          • Inspect for missing piles
          • Inspect for cracks and splits
          • Inspect channel bottom for indication of movement o Spacing (center to center)

Pile Bents

  1. Condition
          • Piles
          • Bracing
              • Horizontal bracing
              • Diagonal bracing
          • Fasteners
          • Impact damage
          • Missing piles

Fender System

Inspect for material defects and collision damage on the following elements (see inspection procedures for bents):

  1. Piles
  2. Diagonal bracing
  3. Horizontal bracing
  4. Fasteners
  5. Wales
  6. Ladders

Scour Countermeasures

  1. Type
      • Riprap
      • Dumped stone
      • Cement/grout bags, sand bags
      • Other
  2. Location
      • Condition
      • Size (dimensions)

Previous Underwater Repairs

  1. Type Bridge
      • Location
      • Condition

Soil – Bottom Material

  1. Visual classification
  2. Location
  3. Depth
      • Probe with steel bar or rod

Marine Growth

  1. Type
  2. Location
  3. Thickness

Debris

      • Determine amount, type and location
      • Estimate reduction of waterway opening
      • Note hazards to divers

Photographs

  1. Visibility, camera availability, and dive conditions permitting (if helpful)

Sketches

  1. Plan view
  2. Elevation (if helpful)
  3. Section (if helpful)

Types of Piers and its structural elements (civil+structural engineering magazine)

  1. Timber pier (most common)
    • Structural elements
      • Pile bents
          • A pile bent consists of a line of timber piles that can vary in size, with a typical minimum diameter of 12 inches for industrial piers. As part of each pile bent there are typically two large beams – one on each side of the piles – at the top of the pile bents called pile clamps or headers. Pile bents are typically spaced at 10 to 15 feet on center along the length of a pier, allowing water and marine organisms to pass under the structure, which is why it is referred to as an open structure.
      • stringers
          • Bearing on top of the headers are closely spaced heavy rectangular timber stringers that span between the pile bents.
      • decking
          • Laid flat on top of the stringers are more heavy rectangular timbers called decking.
      • Pile:
        • Batter Pile/timber brace:
            • The lateral resistance for timber piers typically consists of batter piles and/or timber braces within or beside the pile bents. These batter piles are driven at an angle to resist horizontal loads from ship berthing and wave action and to provide the load path for the transfer of those loads to the ground.
  2. Pier consists of concrete slabs on precast concrete or steel piles. (handle heavier loadings than timber piers; consequently, the piles are driven significantly deeper than the timber piles of timber piers).
    • Structural elements
        • The structures of concrete piers are relatively similar to the timber piers described above, with pile bents at variable spacing and decks spanning between these bents.
        • Most commonly, the piles consist of square or hollow cylindrical precast concrete or steel pipe piles.
        • The decks can consist of monolithic cast – in – place concrete slabs or concrete slabs on various concrete beam elements.
  3. Pier consists of concrete slabs and beams on fill material and timber piles surrounded by a series of large steel sheet pile cells. (less common)
    • These types of piers do not allow for water to pass below and are thus called closed piers.

Deterioration

The primary enemy of timber structures is marine borers (mollusc or crustacean) that attack the timber structures in the splash zone and at the mudline. As the name implies, these organisms bore holes into the structural elements. Some borers attack the outer surface, while some borers destroy the cores of the elements. When the borers attack the outer surfaces, the weak material left at the surface is easily removed by waves and other forces, eventually causing an hourglass – like shape of the piles or brace members. Most commonly, timber elements are protected from these organisms by pressure – treating with preservatives. These preservatives are very similar to those used in residential applications – applied in much heavier doses. Some states prohibit the use of pressure – treated lumber and other materials susceptible to leaching. Alternative, non – polluting materials include plastic, greenheart or other untreated wood, polymer coated pressure – treated wood, concrete or other inert products.

Deterioration of concrete occurs most often when the reinforcing steel inside the concrete corrodes, which is caused by moisture and chlorides penetrating the concrete and reaching the steel. When the steel corrodes, it expands and causes the concrete to spall off. Concrete can be protected from this type of deterioration with admixtures, increased cement content and various types of cement and cement substitutes (like silica fume) that help reduce the penetration of moisture and chlorides. Alternative or additional protection can be provided with coatings on the steel reinforcing, such as epoxy paints or hot – dip galvanizing. Adequate cover over the steel reinforcing, an adequate amount and spacing of reinforcing and proper curing to control cracking are the most cost – effective ways of protecting the concrete from deterioration.