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Full Scale Design

Scale-Up Considerations

When scaling, different considerations of similarity must be considered to calculate an accurate

prototype design to simulate the real-world functionality of the design. As certain properties of the

flow cannot be translated directly between scales, different important considerations must be usedto calculate scaled attributes. These considerations include:

Geometrical similarity Linear dimensions must have same scale ratio

Kinematic similarity Velocities and motions models must have same scale ratio

Dynamic similarity Combination of the same scale ratios of geometrics and forces acting

on the structure

In the scaling down of forces and dimensions for the prototype model, the dominating force

controlling flow properties relative to the inertial fluid forces is gravity. Therefore the Froude

Number is used in scaling, representing the ration of inertial forces to the weight of the fluid.

However, when scaling up, gravity is no longer dominant and viscous forces of water are more

dominant. Because of this, the Reynolds Number can be used to accurately up-scale the dimensions

and forces on the structure, representing the ratio between inertial and viscous forces of the flow

around the pontoon.

Materials

A real-world model of the ferry terminal would not only experience different conditions, but would

also be constructed from different materials as scaling restraints on the scaled pontoon make usingaccurate materials unreasonable. Materials used in a full-scale structure would have a much larger

environmental impact, making the use of sustainable materials very important. Ideally they would

have the following attributes.

Use as few materials as possible

Reduce quantity of materials

Renewable and recyclable if possible

Materials with recycled content

Avoid hazardous materials

Some important design attributes crucial to an effective and long-lasting terminal include the

following properties which will be used primarily in deciding on materials used in the full-scale

structure.

Corrosion resistance

Strength to overcome loads

Lightweight

It must also be noted that dissimilar metals should be separated from direct contact with eachother

to eliminate the possibility of galvanic corrosion in the presence of elecreolytes which may bepresent in the Brisbane River.

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Piles:

Constructed from plastic, reinforced with steel rods. Plastic is corrosion resistant, otherwise

steel would need galvanising/paint/sacrificial anodes. Plastic has less strength, but will be

reinforced.

Pontoon: Constructed from steel reinforced concrete filled with expanded polyethylene, with a

stainless steel casing. Rubber fenders will be positioned along the serviceable edge of the

pontoon.

The top platform will be finished with a non-slip polyurethane surface.

Gangway:

Aluminium main frame and rails with stainless steel fittings to increase strength of hinges

from shear stresses and breakage. Testing shows aluminium and stainless steel to be an

acceptable combination.

Non-slip polyurethane surface with high durability, and abrasion and corrosion resistance.

Waiting Area:

On land waiting area, reducing need for geotechnical drilling of riverbed to test soil strength

and rock depth. Drilling is still necessary for foundations as the structure will be close to

trhe river with unstable clay soils and high water saturation levels.

Decking constructed from treated wood for aesthetic look as well as lower embodied energy

source than concrete/steel/plastics and can be sourced locally. It is also a non-slip surface.

Main structure will be steel reinforced concrete

Design Details

Pontoon and Piles:

Streamlined shape of pontoon limits fluid drag forces on the pontoon, reducing the load on

the two piles anchoring and restricting the pontoon's vertical and horizontal movement.

Two parallel floats will support the pontoon featuring a slight curve to each float to negate

the possibility of negative lift, pulling the leading edge into the water and sinking the

pontoon.

Downstream pilon features a spring dampening system, pivoting around the upstream pilon

and damping forces experienced during the docking of CityCat's, as well as normal waves

and debris hitting the pontoon to a lesser extent. The springs must have a high stiffness to

prevent the pontoon from moving too much during normal use. The serviceable edge of the

pontoon will also utilise rubber fenders able to compress, transferring the load to the

pontoon and piles and lessening the strain on the main suspension system.

Both piles protrude a minimal distance out of the water allowing the pontoon to rise and fall

with tide levels under normal conditions.

Both piles are telescopic allowing the pontoon to continue rising with the water level by

pushing upwards on the top of each pilon which are able to rise telescopically. This adds anexrta downward force on the pontoon so it must be buoyant enough to float with the weight

of the structure, as well as the additional downward force.

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Gangway:

The gangway is secured to the river bank on another pilon, similar the the upstream pilon on

the pontoon, sitting on a fixed stopper preventing the gangway from moving below a certain

height.

Under normal conditions the gangway will not move vertically where it is fixed to the river

bank using a simple hinge allowing 90 degree movement.

The gangway will be connected to the pontoon with a rail system allowing it to move

horizontally along the pontoon due to the change in the distance from the pontoon to the

fixed pilon on the river bank as the water rises and falls.

As the height of the water increases the distance will decrease. The length of the gangway is

fixed so as the water rises it will move horizontally along the side of the pontoon. For this to

happen the gangway attachment to the river bank must be above the level of the pontoon.

The gangway must also be angled relative to the pontoon in order for it to slide freely

instead of pusing against the pontoon. This could also be overcome by angling the rail

system on the pontoon.

In flood conditions or when the water level rises enough to position the pontoon at the same

height as the gangway the gangway will slide off the end of the rail and float in the river,

being guided inline with the flow of water around the pivot of the pilon. There must be

floats on the bottom of the gangway for this to happen.

This minimises the fluid drag force experienced by the river bank pilon in flood conditions.

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