![REFERENCE
Shell Structures for Architecture - Form Finding and Optimization
Edited by Sigrid Adriaenssens, Philippe Block, Diederik Veenendaal and Chris Williams
Shell Structures for Architecture [PDF] (pdfroom.com)
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Module - III.pptx shell structures and folded plates
- 1. MMBC – V MODULE – III SHELL STRUCTURES & FOLDED PLATES Lecture by Ar. Poornima Magesh
- 2. EVOLUTION OF STRUCTURES A structure is something that will support an object or a load. A structure must be strong enough to support its own weight and whatever load is put on it ! A structure is a group of elements somehow united to support a load with stability. Everything has a structure. For example: humans have skeleton, bicycles have a frame, houses have columns, beams and a roof.
- 3. There are four types of structure : Mass Structures Frame Structures Shell structures. Suspension structures CLASSIFICATION OF STRUCTURES Solid structures which rely on their own weight to resist loads. Components and various membranes to carry and resist load A thin, curved plate structure shaped to transmit applied forces by compressive, tensile, and shear stresses that act in the plane of the surface. . A suspension structure holds an elements by cables that are held from the top of a tall column. The space between one column and the next is called the span.
- 4. Shell structures are by no means a modern invention. Evidence of the earliest vaulted structures comes from Mesopotamia in 3000BC: a 5000-year-old Mesopotamian burial chamber with a barrel vault of approx. 1m span is on display at the Berlin Museum of Prehistory and Ancient History HISTORICAL BACKGROUND OF SHELL STRUCTURE Nubian vaulting technique
- 5. If we tried to stiffen it from its primary state, it couldn't support its own weight. However, if we bend it, the sheet achieves a new structural quality. The shells act in the same way. "You can't imagine a form that doesn't need a structure or a structure that doesn't have a form. Every form has a structure, and every structure has a form. Thus, you can't conceive a form without automatically conceiving a structure and vice versa". The importance of the structural thought that culminates in the constructed object is then, taken by the relationship between form and structure. The shells arise from the association between concrete and steel and are structures whose continuous curved surfaces have a minimal thickness; thus they are widely used in roofs of large spans without intermediate supports. Working of shell structure with paper
- 6. SHELL STRUCTURES Introduction Concept Function Structure Materials Construction Techniques • A shell is a thin structure composed of curved sheets of material, so that the curvature plays an important role in the structural behaviour, realizing a spatial form • A thin curved membrane or slab usually of reinforced concrete that functions both as structure and covering • The essential function of a shell structure are continuity and curvature • Their continuity transmit forces in a number of different directions in the surface of the shell • Open shell structure is deformable
- 7. Tree structure spider web conch shell Spine bone SHELL STRUCTURES - CONCEPT FORM: The sorting of natural inspiration forms is; living models and non- living models. FUNCTION: In structural context, nature’s structures and forms motivate architectural innovation either in aesthetic, functional or structural ways for electing optimal morphology, functional integration, and efficiency. Introduction Concept Function Structure Materials Construction Techniques
- 8. Introduction Concept Function Structure Materials Construction Techniques FUNCTION: LOAD TRANSFER Types of Gaussian Curvature Due to its structural continuity, the shells can transmit the loads in a number of different directions.
- 9. STRUCTURAL BEHAVIOUR OF SHELLS Introduction Concept Function Structure Materials Construction Techniques • Shells are form based structures where the shape influences the shell’s load carrying capacity. • This structural geometry largely dictates the development of stresses in the shell elements. • This has to kept in mind to avoid unwanted deformations and structural failure. They transfer these loads by generating in-plane membrane forces, a fact that separates them from plates. Shells, unlike membranes, stretch and contract without producing significant bending or changes in local curvature. Membrane behaviour - Curvature To secure the high structural efficiency of a thin shell, select a shape, proportions, and supports for the specific design conditions that come as close as possible to satisfying the membrane theory
- 10. CLASSIFICATION OF SHELL STRUCTURE SINGLE CURVED DOUBLE CURVED Surface of revolution Surface of translation Synclastic Anticlastic Circular cylinders Conical Circular or non circular cylinders Conical Surface of revolution Surface of translation Circular domes Ellipsoid Paraboloid Elliptic paraboloid Paraboloids Hyperboloids Hyperbolic paraboloids Conoids Hyperboloids Monoclastic
- 11. The terms single and double curvature are used to distinguish the comparative rigidity of the two forms and complexity of centering necessary to construct the shell form. Barrel vault conoid dome hyperboloid paraboloid CLASSIFICATION OF SHELL STRUCTURE SINGLE CURVATURE SHELL: 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 geometric distinction between the form of shell because a barrel vault is single curvature but so is a dome. BARREL VAULT CONOID HYPERBOLOID PARABOLOID DOME
- 12. CLASSIFICATION OF SHELL STRUCTURE Introduction Concept Function Structure Materials Construction Techniques Classification based on Gaussian curvature A sphere has positive gaussian curvature, and so the circumference of a circle drawn on a sphere is less than ππ times its diameter The circumference of a circle is longer than ππ times its diameter, and so, to make a flat sheet lie along such a surface, you either have to tear it to increase the circumference, or wrinkle it in the middle to reduce the radius.
- 14. CLASSIFICATION OF SHELL STRUCTURE Introduction Concept Function Structure Materials Construction Techniques Classification based on Shape Surface of revolution: Produced by rotating a plane around the axis MONOCLASTIC Surface of translation: Obtained by translating a plane curve parallel to the plane containing the curve Ruled surface: Translating a line along two end curves – Hyperbolic & Hyperboloid Form of curvature
- 15. CLASSIFICATION OF SHELL STRUCTURE Classification based on surface DEVELOPABLE SURFACES: Smooth surface with zero Gaussian curvature. It can be reduced to a planer surface without stretching or deforming the surface Conversely it is a surface that can be deformed by transforming a plane Eg A cylindrical panel is a developable because it can be unfolded to a rectangular plate. NON - DEVELOPABLE SURFACES: It requires stretching, cutting or deforming to collapse it into a planer surface. That requires additional forces to collapse as compared to developable surface. Eg – Spherical dome represents a non developable surface
- 16. Developable surfaces (singly curved): developable surface is a surface that can be unrolled onto a flat plane without tearing or stretching it. It is formed by bending a flat plane, the most typical shape of a developable shell is a barrel, and a barrel shell is curved only in one direction. Barrel : arch action & beam action together make a barrel. There are mainly two types of barrel : - long barrels , arch action is prominent - short barrels, beam action is prominent structural behavior of short barrel shells: these shells are typically supported at the corners and can behave in one or a combination of the following ways: structural behavior of long barrel shells: these are typically supported at the corners and behave structurally as a large beam.
- 17. Surface of translation Surface of revolution Ruled surface CASES OF SHELL STRUCTURE
- 18. Surface translation Doubly curved – Anticlastic Surface translation +Doubly curved + Synclastic
- 19. SHELL STRUCTURE – MATERIALS & CONSTRUCTION Compressed earth + Reinforced concrete + Steel + Aluminium alloys + Glass + Timber Foam Formwork for a Curved Section, This formwork would be used on ¼ of a hyberbolic paraboloid, and would then be removed and reused on the remaining portions. It is a foam curved shape supported with an inner brace of wooden 2x4’s. Span is shorter than its width Span is 12-30 m with its width ½ of the span and rise is 1/5 of its width SPAN STIFFENING ARCHES
- 21. TYPES AND FORMS OF SHELL STRUCTURE • Folded Plates • Barrel Vaults • Short Shells • Domes (surfaces of revolution) • Folded Plate Domes • Translational Shells • Warped Surfaces • Combinations • Folded plates are assemblies of flat plates or slabs inclined in different directions and rigidly joined along their longitudinal edges that can carry loads without the need for additional supporting beams along mutual edges • Folded plate = Slab action + Beam action In length direction they act like thin inclined beams of great depth, stabilized against buckling at the top and bottom by adjoining plates.
- 22. • Bending in folded plates cause top compression and bottom tension • Folded plates tend to flatten out under load that can be prevented by walls or frames at end supports • End panel buckling can be resisted by edge beams Flat paper deforms under its own weight Folding paper increases strength & stiffness Paper buckling under heavy load Secured end support helps resist buckling STRUCTURE AND THE LOAD
- 23. STRUCTURE AND THE LOAD Folded plate concept Slab action in width direction Beam action in length direction Bending as external compression & tension forces Gravity load Buckled end panels End panels stabilised with edge beams • The external forces are transferred to shorter end of one folding element • The axial force is then divided between adjacent elements • Later forces are transferred to the supporting columns
- 24. TYPES – FOLDED PLATES
- 25. FOLDED PLATES APPLICATIONS • Roof structure • Wall structure • Floor structure • Staircase
- 29. REFERENCE Shell Structures for Architecture - Form Finding and Optimization Edited by Sigrid Adriaenssens, Philippe Block, Diederik Veenendaal and Chris Williams Shell Structures for Architecture [PDF] (pdfroom.com) Shell Structures for Architecture - PDF Drive