SHELLS - SINGLE CURVATURE
keywords : Shells, Structure, Single Curvature, Construction, Architecture, Struktur, Shell, Konstruksi, Arsitektur
1. DEFINITION
Shells can be defined as curved structures capable of transmitting loads in more than two directions to supports. Loads applied to shell surfaces are carried to the ground by the development of compressive, tensile, and shear stresses acting in the in-plane direction of the surface. Thin shell structures are uniquely suited to carrying distributed loads and find wide application as roof structures in building. They are, however, unsuitable for carrying concentrated loads.(Shodeck)
2. STRUCTURAL CHARACTERISTICS
The behavior of any shell surface under the action of a load is analogous to a membrane, a surface element so thin that only tension forces can be developed (e.g. a soap bubble). Of primary importance is the existence of two sets of internal forces in the surface of a membrane that act in perpendicular directions. Also in existence is a type of tangential shearing stress which is developed within the membrane surface which helps carry the applied load. The shell tends to act in a fashion sim ilar to a two-way plate structure. (Schodeck)
3. SUPPORT CONDITIONS
Support conditions in both shells of revolution (spherical) and shells of translation (cylindrical) are a major design consideration. Some device must be employed to gather forces at the lower edges of the shell. In domes, common methods include circular buttressing systems or a tension ring. Cylindrical shells are usually supported by edge beams.
4. CONSTRUCTION CHARACTERISTICS
A consequence of carrying loads by in-plane forces (primarily tension and compression) is that shell structures can be very thin in comparison to their spans. Span to thickness ratios of 400 or 500 are not uncommon. (e.g. A 3 in. thickness is possible for domes spanning 100-125 ft.) Reinforced concrete has become the ideal material used for these types of three dimensional surfaces, however, they may also be made of assemblies of short, rigid bars. In concrete structures, the careful laying and specification of reinforcement is key to the success of the structure. (Shodeck)
5. TYPICAL MATERIALS
Shells can be made of almost any material -- cold formed steel, wood, reinforced concrete, plastics. Structures made of short, rigid bars of wood or steel are technically not shell structures since they are not surface elements, however, thei r structural behavior can still be conceptualized in this fashion.
6. Author
Matt Rumbaugh, University of Oregon. 1995
7. Adapted from
http://darkwing.uoregon.edu
1. DEFINITION
Shells can be defined as curved structures capable of transmitting loads in more than two directions to supports. Loads applied to shell surfaces are carried to the ground by the development of compressive, tensile, and shear stresses acting in the in-plane direction of the surface. Thin shell structures are uniquely suited to carrying distributed loads and find wide application as roof structures in building. They are, however, unsuitable for carrying concentrated loads.(Shodeck)
2. STRUCTURAL CHARACTERISTICS
The behavior of any shell surface under the action of a load is analogous to a membrane, a surface element so thin that only tension forces can be developed (e.g. a soap bubble). Of primary importance is the existence of two sets of internal forces in the surface of a membrane that act in perpendicular directions. Also in existence is a type of tangential shearing stress which is developed within the membrane surface which helps carry the applied load. The shell tends to act in a fashion sim ilar to a two-way plate structure. (Schodeck)
3. SUPPORT CONDITIONS
Support conditions in both shells of revolution (spherical) and shells of translation (cylindrical) are a major design consideration. Some device must be employed to gather forces at the lower edges of the shell. In domes, common methods include circular buttressing systems or a tension ring. Cylindrical shells are usually supported by edge beams.
4. CONSTRUCTION CHARACTERISTICS
A consequence of carrying loads by in-plane forces (primarily tension and compression) is that shell structures can be very thin in comparison to their spans. Span to thickness ratios of 400 or 500 are not uncommon. (e.g. A 3 in. thickness is possible for domes spanning 100-125 ft.) Reinforced concrete has become the ideal material used for these types of three dimensional surfaces, however, they may also be made of assemblies of short, rigid bars. In concrete structures, the careful laying and specification of reinforcement is key to the success of the structure. (Shodeck)
5. TYPICAL MATERIALS
Shells can be made of almost any material -- cold formed steel, wood, reinforced concrete, plastics. Structures made of short, rigid bars of wood or steel are technically not shell structures since they are not surface elements, however, thei r structural behavior can still be conceptualized in this fashion.
6. Author
Matt Rumbaugh, University of Oregon. 1995
7. Adapted from
http://darkwing.uoregon.edu
