BC PPT SHELLED STRUCdvdvdvdvTURES (1).pptx
- 2. SHELLED STRUCTURES A shell is a thin-structural element used in a building composed of curved sheets of materials dividing the interior space of the structure from its exterior. The shell elements are typically curved and assembled into a large structure. It is made of reinforced concrete and serves both as a structure and covering. Shell structures are self-supporting and used to cover a large area of span without any supports of beams, columns, and walls. Its efficiency is based on its curvature (single or double), which allows different stress paths and gives the optimum form for transmission of many different load types. A single curvature shell is monoclastic, which can be curved in one direction and comes in the form of barrel vaults or conoid shells. Double curvature is synclastic and anticlastic which comes in the form of a sphere or hyperboloid.
- 3. SINGLE OR DOUBLE CURVATURE SHELLS Single curvature shell(monoclastic): are curved on one linear axis and are a part of a cylinder or cone in the form of barrel vaults and conoid shells. Double curvature shell: are either part of a sphere, or a hyperboloid of revolution. The terms single curvature and double curvature do not provide a precise geomoetric distinction between the form of shell because a barrel vault is single curvature but so is a dome
- 4. DOUBLY CURVED SHELLS They are mainly classified as: 1) synclastic 2) anticlastic Synclastic shells: These shells are doubly curved and have a similar curvature in each direction. A dome is a good example of a synclastic shell, it is doubly curved and can be formed by rotating a curved line around an axis. A dome can be split up into two different directions; vertical sections separated by longitudinal arch lines (also called meridians), and horizontal sections separated by hoops or parallels. Structural behavior: Similar to arches under a uniform loading the dome is under compression everywhere, and the stresses act along the arch and hoop lines.
- 5. Anticlastic shells: are doubly curved but each of the two curves have the opposite direction to the other. E.G. Saddle points. Conoids, hyperbolic paraboloid and hyperboloids are all considered to be anticlastic shell because they are saddled shape with different curvature in each direction and straight lines can be drawn of the surface. Conoids: formed by moving a one end of a straight line along a curved path and the other along a straight path. Hyperboloids: formed by rotating a straight line around a vertical axis.
- 6. CENTRING OF SHELLS Centering is the term used to describe the necessary temporary support on which the curved R.C.C shell structure is cast. The centering of a barrel vault, which is part of a cylinder with same curvature along its length; is less complex. The centering of conoid, dome and hyperboloid of revolution is more complex due to additional labour and wasteful cutting of materials to form support for shapes that are not of uniform linear curvature. The attraction of shell structures lies in the elegant simplicity of curved shell forms that utilise the natural atrength and stiffness of shell forms with great economy in the use of materials. The disadvantage of shell structure is their cost. The shell structure is more expensive due to considerable labour required to construct the centering on which the shell is cast.
- 7. Components of a shell structure; The structural skeleton and foundation Base plant Building cladding The building envelope Fire barriers Fire detection system Electrical and plumbing systems Pathways, boundary walls, Pavement, and fencing Landscaping Signage The main purpose of constructing the shell structure is that it will cover a larger area of the building.
- 8. Advantages of Shell structures A light form of construction Faster construction An easy method of fabrication Waste reduction as no requirement of fittings Covers a large area Aesthetic in appearance Energy efficient Lesser material usage
- 9. Disadvantages of Shell structures Since concrete is a porous material, concrete domes often have issues with sealing. If not treated, rainwater can seep through the roof and leak into the interior of the building. On the other hand, the seamless construction of concrete domes prevents air from escaping, and can lead to buildup of condensation on the inside of the shell. Shingling or sealants are common solutions to the problem of exterior moisture, and dehumidifiers or ventilation can address condensation.
- 10. Types of Shell Structure Cylindrical Shell Asymmetrical Cylindrical Shells Faced Folded Plate of Shell Structure Folded Plate Dome of Shell Structure Multiple Cylindrical Shells North Light Shells Barrel Shells Barrel Vaults Short Shells and Long Shells Domes Intersection Shell Structure Shell Arches Translation Shells Combination Shells
- 11. Cylindrical Shell: These shells are the primary structural component of both aquatic and airborne systems. Frames or ribs are also used to stiffen these structures. Some examples of typical cylindrical shells include the : Semi-ellipse. Arch circle. Cycloid catenary. Horseshoe form. Multiple Cylindrical Shells: These cylindrical shells comprise a of cylindrical shells that are parallel and transversely continuous.
- 12. Barrel Vaults: A barrel vault is a continuous vaulted form that could be semi-circular in shape, resembling the roof of a cave, or pointing at the apex. It is usually built by a sequence of edge arches or vaults. Short Shells and Long Shells: Short shells are those with a short period of length and long shells Where the period length is greater than the width, the shell shape is referred to as a long shell. North Light Shells: A barrel shell is a collection of very thin arches that have the same compressive power. It can withstand very large quantities of weight as long as the weight is spread proportionally.
- 13. Domes: A dome is a structured framework that occupies an area that is somewhat square or circular. The domes are connected to a surface formed by some curve rotating around a vertical line. Intersection Shell Structure: The structural effects of the intersection shell are dependent upon the angle of intersection of the surface. Shell Arches: Small shell thicknesses can be rendered much smaller than an arc if the stresses are mostly compressive. Shells are not a very effective framework for high bending moment values.
- 14. Translation Shells: A translation shell is created by moving a vertical curve over another vertical curve. Combination Shells: It is a combination of shell, solid, and frame construction. A sturdy foundation beneath a home supports the weight of the structure. A brick, concrete, or other material shell is supported by a wood or metal frame. The frame is the skeleton of the house. It provides stability and support for the walls and roof.
- 15. Faced Folded Plate of Shell Structure: Folded plate structures are assemblies of flat plates, or slabs, inclined in different directions and joined along their longitudinal edges. Modern folded plate structures are typically made of cast in situ or precast reinforced concrete, or steel plate. It consists of triangular or polygonal planar thin slabs joining along their edges to form a thin plate structure. Folded Plate Dome of Shell Structure: In this category are included all domes made with plane slabs and plates. There are many variations and only a few of them can be shown here. Domes may be constructed with small angles between the plates or with large angles between plates and the structural action may be considerably different for each type.
- 16. Applications of shell structures The shell structure is typically found in nature as well as in classical architecture. The shell structure is commonly used in seismic zones where structures undergo seismic loads.The reason of using the shell structures in the earthquake-prone areas is that it has high strength with respect to its self-weight. Shell Structures are generally used to cover the larger area of the building where the interior of the building has no columns and walls to support the flat slabs Industrial structures: – silos, tanks, cooling towers, reactor vessels etc. Auditoriums and food courts Architectural special structures
- 17. Examples of shell structures in India Lotus Temple,Delhi Matrimandir, Auroville, Tamil Nadu Kanteerava Indoor Stadium, Bangalore