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Asuperstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such asbuildings,bridges, orships.[1]
On water craft, the superstructure consists of the parts of the ship or aboat, includingsailboats,fishing boats,passenger ships, andsubmarines, that project above her main deck. This does not usually include itsmasts or anyarmamentturrets. Note that, in modern times, turrets do not always carrynaval artillery. They can also carrymissile launchers and/orantisubmarine warfare weapons.
The size of a watercraft's superstructure can have many implications in the performance of ships and boats, since these structures can alter their structural rigidity, their displacements, and/or stability. These can be detrimental to any vessel's performance if they are taken into consideration incorrectly.
The height and the weight of superstructure on board a ship or a boat also affects the amount offreeboard that such a vessel requires along its sides, down to herwaterline. In broad terms, the more and heavier superstructure that a ship possesses (as a fraction of her length), the less the freeboard that is needed.
Thespan of a bridge, the portion that directly receives the live load, is referred to as the superstructure. In contrast, theabutment,piers, and other support structures are called the 'substructure'.[2]
In order to improve theresponse during earthquakes of buildings and bridges, the superstructure may be separated from itsfoundation by variouscivil engineeringmechanisms ormachinery. All together, these implement the system of earthquake protection calledbase isolation.
