2015-03-31 I&S Committee - Item 5 - Attachment 1 - Munna Pt Bridge Repairs Level 3 Bridge Report

the point of having little or no safety factor. Without commencing repairs now, the repair
bill will exceed the cost of a replacement bridge in a few years and the public are likely to
be in danger within 1 year (by mid 2015).

Tod Consulting’s bridge condition assessment (2014) can be quickly understood by
looking at drawing 02600-SK1 in Appendix F. From our review and investigation, we infer
that:

1. Deck Units
      • 4 deck units per span are suffering from ASR, and the prestressing strands
         and reinforcement in these may have corroded. It is conservative to assume
         these deck units are now structurally ineffective.
      • The rest of the deck units are likely to have prestressing strands and
         reinforcement that are 100% intact.
      • Deck units in good condition typically have a large factor of safety for
         structural capacity, so that the good units will compensate for the lost strength
         in the ones suffering from ASR.
      • The good deck units are likely to suffer ASR cracking and reinforcement
         corrosion sometime between now and 2016. The repair bill for the deck units
         will grow exponentially, unless action is taken soon.

2. Headstocks
      • Headstock reinforcement is likely to be 100% intact

3. Columns
      • Column reinforcement is likely to be 100% intact

4. Pilecap Beams
       • The top and side reinforcement cover exceeds the 75mm shown on the
          original drawings, which provides beneficial protection to reinforcement.
       • 75-85% of the top reinforcement is likely to still be intact; 50-80% of the
          bottom reinforcement is likely to still be intact, and 66% of the shear
          ligatures/stirrups are likely to still be intact
       • ASR cracking will continue, and we anticipate that reinforcement will corrode
          heavily, making the bridge dangerous by 2015.

5. Piles
       •   All piles have cracks caused by ASR
       •   The majority of the reinforcement in the piles is likely to be intact, based on
           the two piles where we removed concrete and observed the reinforcement
           condition. This is because most of each pile is underwater; with reduced
           oxygen making the rate of corrosion slower. However, at the pile tops (in the
           tidal zone), it’s probable that the reinforcement has corroded, but it hadn’t
           spalled (broken) off the concrete faces at the time of the February 2014
           inspections.



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