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

1.0 Introduction and Background
In early 2014, the new Noosa Council (NSC) required a Level 3 structural report for the
Munna Point road bridge along Noosa Parade. Noosa Parade is a principal connector
road between the Noosaville and Hastings St business districts. The road also serves
significant residential and holiday-stay areas. NSC engaged Tod Consulting to prepare
the report.

The bridge is approximately 1.5 kilometres southwest of Hastings St, and crosses a wide
saltwater canal connecting Weyba Creek and the Noosa River. Bridge details are as
follows:

• Developers built the 105 metre long concrete bridge (according to an NSC report
  dated 6 Aug 2002).
• Estimated construction date is 1979 (according to TMR reports for the bridge).
• Some original drawings are available, and these can be seen in Appendix B.
• The bridge deck is composed of precast deck units. These are tied together with
  tensioned stressing bars.
• The 7 spans of the bridge deck are supported on cast-insitu headstocks (except at
  each bridge end, where each abutment provides the support). Each headstock is
  supported by two columns, which rest on pilecap beams. There are 10 precast piles
  underneath each pilecap beam. These piles were driven into canal’s bed during
  construction. See figure 1.
• The bridge was originally designed for T44 semi-trailer trucks (see Appendix C),
  based on the thickness of the precast deck units.
• A posted speed limit of 50 km/hour was observed in the vicinity of the bridge.
• Traffic volumes in 2011 were 5300-7100 vehicles per day in each direction, per study
  prepared by Hayes traffic engineering in 2011.
• TMR have a number of bridges in similar saltwater environments of similar age, with
  similar problems. These environmental conditions have contributed significantly to
  many of the bridge structures requiring significant repairs within the first 50 years with
  1% or less reaching a 100 year design life (Humphreys et al, 2007). The reason is that
  industry knowledge of reinforced concrete corrosion was less advanced before the
  1990s, and is still being heavily researched now. This issue has resulted in significant,
  costly repairs for TMR. For example, the 2.74 kilometre long Houghton Highway
  bridge at Redcliffe (opened 1979) suffered ASR cracking of the piles, and in 1991, 500
  piles were concrete encased below water level, and wrapped with composite fibre
  wraps above water level.




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