Lesson Ten The Function of Ship Structural Components The strength deck, bottom, and side shell of a ship act as a box girder in resisting bending and other loads imposed on the structure. The main deck, bottom, and side shell also for envelope to withstand the sea locally. The remaining structure contributes either directly to these functions or indirectly by maintaining the main members in position so that they can act efficiently The bottom plating is a principal longitudinal member providing the lower flange of hull girder It is also part of the watertight envelope, and subject to the local water head. At the forward end, it must withstand the dynamic pressure associated with slamming and plating thickness is usuall increased to provide the necessary strength When fitted the inner bottom also makes a significant contribution to the strength of lower flange. It usually forms a tank boundary for the double bottom tanks and is subject to the local pressure of the liquid contained therein. In addition, it must support the loads from above, usually from cargo placed in the holds The strength deck forms the principal member of the upper flange, usually provides the upper water tight boundary, and is subject locally to water, cargo, and equipment loadings The remaining continuous decks, depending on their distance from the neutral contribute to a greater or lesser extent in resisting the longitudinal bending loads. Certain decks hich are not continuous fore and aft and not contribute to the longitudinal strength. Locally internal decks are subject to the loads of cargo, equipment, stores, living spaces, and, where they form a tank boundary or barrier against progressive flooding, liquid pressure The side shell provides the webs for the main hull girder and is an important part of the watertight envelope. It is subject to static water pressure as well as the dynamic effects of pitching, rolling, and wave action Particularly forward, the plating must be able to withstand the impact of the seas. Aft, extra plate thickness is beneficial in way of rudders, shaft structure and propellers for strength, panel stiffness, and reduction of vibration Additional thickness is necessary at the waterline for navigation in ice Bulkheads are one of the major components of internal structure. Their function in the hull girder depends on their orientation and extent Main transverse bulkheads act as internal stiffening diaphragms for the girder and resist racking loads, but do not contribute directly to longitudinal strength. Longitudinal bulkheads, on the other hand, if extending more than about one-tenth the length of the ship, do contribute to longitudinal strength and in some ships are nearly as effective as the side shell itself Bulkheads generally serve structural functions such as forming tank boundaries, supporting decks and load-producing equipment such as kingposts, and adding rigidity to produce vibration In addition, transverse bulkheads provide subdivision to prevent progressive flooding. All applicable loads must be considered during design The foregoing structural elements of a ship are basically large sheets of plate whose thicknesses are very small compared with their other dimensions, and which, in general, carry loads both in and normal to their plane. These sheets of plate may be flat or curved but in either case they must be stiffened in order to perform their required function efficientlyLesson Ten The Function of Ship Structural Components The strength deck, bottom, and side shell of a ship act as a box girder in resisting bending and other loads imposed on the structure. The main deck, bottom, and side shell also form a tight envelope to withstand the sea locally. The remaining structure contributes either directly to these functions or indirectly by maintaining the main members in position so that they can act efficiently. The bottom plating is a principal longitudinal member providing the lower flange of hull girder. It is also part of the watertight envelope, and subject to the local water head. At the forward end, it must withstand the dynamic pressure associated with slamming and plating thickness is usually increased to provide the necessary strength. When fitted, the inner bottom also makes a significant contribution to the strength of lower flange. It usually forms a tank boundary for the double bottom tanks and is subject to the local pressure of the liquid contained therein. In addition, it must support the loads from above, usually from cargo placed in the holds. The strength deck forms the principal member of the upper flange, usually provides the upper water tight boundary, and is subject locally to water, cargo, and equipment loadings. The remaining continuous decks, depending on their distance from the neutral axis, contribute to a greater or lesser extent in resisting the longitudinal bending loads. Certain decks which are not continuous fore and aft and not contribute to the longitudinal strength. Locally internal decks are subject to the loads of cargo, equipment, stores, living spaces, and, where they form a tank boundary or barrier against progressive flooding, liquid pressure. The side shell provides the webs for the main hull girder and is an important part of the watertight envelope. It is subject to static water pressure as well as the dynamic effects of pitching, rolling, and wave action. Particularly forward, the plating must be able to withstand the impact of the seas. Aft, extra plate thickness is beneficial in way of rudders, shaft structure and propellers for strength, panel stiffness, and reduction of vibration. Additional thickness is necessary at the waterline for navigation in ice. Bulkheads are one of the major components of internal structure. Their function in the hull girder depends on their orientation and extent. Main transverse bulkheads act as internal stiffening diaphragms for the girder and resist racking loads, but do not contribute directly to longitudinal strength. Longitudinal bulkheads, on the other hand, if extending more than about one-tenth the length of the ship, do contribute to longitudinal strength and in some ships are nearly as effective as the side shell itself. Bulkheads generally serve structural functions such as forming tank boundaries, supporting decks and load-producing equipment such as kingposts, and adding rigidity to produce vibration. In addition, transverse bulkheads provide subdivision to prevent progressive flooding. All applicable loads must be considered during design. The foregoing structural elements of a ship are basically large sheets of plate whose thicknesses are very small compared with their other dimensions, and which, in general, carry loads both in and normal to their plane. These sheets of plate may be flat or curved, but in either case they must be stiffened in order to perform their required function efficiently