BRIGHTON JETTY

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BRIGHTON JETTY

• LEIGH DAWSON
• PETER HEFFERNAN

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HISTORY

• Original jetty built in 1886
• Constructed of timber supported on timber piles
  and crossheads.
• 206 metres long.
• Tee-head at western end.
• Destroyed on 24 May 1994 by heavy storms.

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DESTRUCTION OF JETTY
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HISTORY (2)

• New jetty constructed in 1995/96.
• Deck, beams, crossheads piles constructed of
  concrete.
• 209 metres long with jetty head.
• Mobile phone tower placed at centre of jetty head.

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NEW JETTY
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AIMS OF PRESENTATION

• Model jetty deck under following conditions
• Dead live load distributed over entire deck.
• Dead load distributed over entire deck, live load
  distributed on half of deck.
• Model one concrete pile under following
  conditions
• Stresses due to normal loading.
• Displacements in z direction.

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ASSUMPTIONS

• Concrete Strength fc 50 MPa
• (AS3600, Table 4.3 in tidal or splash zone,
  Exposure classification C)
• Fixed at abutments.
• Live load 5 kPa (AS1170.1, Table 3.1, C3).
• Dead Load 7.6 kPa.
• Deck not constructed as a T-beam, but is a plate
  connected to two parallel beams.

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DECK LAYOUT
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MODELLING OF DECK

• Constructed by using 23 deck sections, each of
  length 8.54 m long.
• Consists of a deck connected to two beams that
  run below and in the same direction as the deck.
• These sit on cross heads that are in turn
  connected to two piles.

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MODELLING OF DECK
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MODELLING OF DECK
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DECK MODEL

• First analysis involves the dead live load
  distributed over the entire deck.
• Analysed using concrete and also wood, to compare
  roughly how the jetty would have performed prior
  to being destroyed.
• Conclusions stresses remained approximately the
  same, displacements were different but
  displacement shape was the same.

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DECK DISPLACEMENTS
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DECK STRESS 11
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DECK STRESS 22
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BEAM DISPLACEMENTS
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BEAM STRESSES
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DECK MODEL

• Second analysis involved the dead load being
  distributed over entire deck and live load
  distributed on one half of the deck only.
• Analysed for concrete only.
• Conclusions Displacements greater on the side
  with the live load applied, but stresses slightly
  less.

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DECK DISPLACEMENTS
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DECK STRESS 11
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DECK STRESS 22
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MODDELLING OF PILE
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PILE MODEL

• octagon cross section with a width of 406
  millimetres.
• 50 MPa concrete
• Length 13.5 metres
• Driven into sand assumed pressure onto pile of 17
  kN/m
• Load on top of pile taken as 16.6Kpa

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PILE MODEL

• Displacement of the pile into the sand

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PILE MODEL

• Brick Stress 11 22

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PILE MODEL

• Plate Stress

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MOBILE PHONE TOWER
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MOBILE PHONE TOWER

• Analysis is difficult.
• It is expected that there will be a greater
  concentration of stresses and displacements
  around the base of the phone tower.
• Some resistance to these will be provided by the
  thicker deck section.

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THATS ALL FOLKS!

• Thankyou and we hope you enjoyed the presentation
  brought to you by a concrete deck, a concrete
  beam and 16 kPa!