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

Table of contents

Table of contents ............................................................................................................................. 2	
  
Glossary of Terms ........................................................................................................................... 2	
  
Executive Summary ........................................................................................................................ 5	
  
1.0 Introduction and Background .................................................................................................. 11	
  
2.0 Review of Existing Reports & Site Observations ..................................................................... 12	
  
3.0 Condition Assessment ............................................................................................................. 21	
  
4.0 Repair Options – Cost Comparison ......................................................................................... 23	
  
5.0 Conclusions ............................................................................................................................. 26	
  
References .................................................................................................................................... 28	
  
Appendix A – Locality plan ............................................................................................................ 29	
  
Appendix B – Original drawings of bridge ..................................................................................... 30	
  
Appendix C – Design loads ........................................................................................................... 30	
  
Appendix D – Risk Assessment methodology ............................................................................... 30	
  
Appendix F – Bridge Condition & Repair staging drawings (not for construction) ......................... 31	
  



Glossary of Terms
      •     Abutment = a structure at each end of the bridge, that supports the bridge deck.
            The components of an abutment include ballast wall, wingwalls, pilecap beam,
            and piles.

      •     ASR = Alkali Silica Reaction. ASR is sometimes known as AAR (Alkali Aggregate
            Reaction). Many Queensland aggregates (gravels) that are used for concrete
            manufacture contain silicates, which react with alkalis in the cement. ASR causes
            concrete structures to expand and crack. Cracks usually run in the same direction
            as the main reinforcement. If little or no reinforcement is present, then cracks will
            run in all directions.

            ASR only occurs in the presence of water. Unfortunately, seawater contains water
            and alkalis, which supplement the concrete alkalis and worsen ASR reactions.
            Modern concretes are often batched with a blend of Portland cement and flyash
            (and/or other pozzolanics) to prevent ASR problems. TMR tests showed the
            Munna Point bridge pilecap beams don’t contain flyash.

      •     Cast-insitu concrete = concrete poured on a construction site

      •     Carbonation = a process where carbon dioxide from the atmosphere penetrates
            into concrete and lowers the concrete pH level (more acidic, less alkaline). Once
            carbonation penetrates in far enough to reach the reinforcement, the
            reinforcement usually starts corroding.

      •     Cathodic Protection = electrical cabling and titanium anodes are connected to the
            reinforcement that needs protection from corrosion. A direct (DC) electrical
            current is passed through the cabling to put a negative charge into the
            reinforcement, which stops the corrosion reaction. Cathodic protection Contractor
            (Freyssinet) advises that the system uses relatively small amounts of electricity –



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