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BRIGHTON JETTY LEIGH DAWSON PETER HEFFERNAN 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. DESTRUCTION OF JETTY 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. NEW JETTY 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. ASSUMPTIONS Concrete Strength f’c = 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. DECK LAYOUT 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. MODELLING OF DECK MODELLING OF DECK 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. DECK DISPLACEMENTS DECK STRESS 11 DECK STRESS 22 BEAM DISPLACEMENTS BEAM STRESSES 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. DECK DISPLACEMENTS DECK STRESS 11 DECK STRESS 22 MODDELLING OF PILE 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 PILE MODEL Displacement of the pile into the sand PILE MODEL Brick Stress 11 & 22 PILE MODEL Plate Stress MOBILE PHONE TOWER 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. THAT’S ALL FOLKS! Thankyou and we hope you enjoyed the presentation brought to you by a concrete deck, a concrete beam and 16 kPa!
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