1. Shell Structures
Presented by Melissa Martinyak, Nelson Perello and Kelsey BakerAmsterdam Maritime Museum. Dok Architecten
2. Exploring Shell Forms
āShell Structures are constructed systems described by
three-dimensional curved surfaces, in which one dimension is
signiļ¬cantly smaller compared to the other two. They are
form-passive and resist external loads predominantly through
membrane stresses.ā
āShell structures for architecture : form ļ¬nding and optimizationā
ā Freeform
- Free-curved or sculptural shells
ā Mathematical
- Geometrical or analytical shells
ā Form-found
- Natural, hanging shapes, strained gridshells
āThe shell designer seeks forms to carry the applied loads in
axial compression with minimal bending forces.ā
āShell structures for architecture : form ļ¬nding and optimizationā
Figure 1
Figure 2
Figure 3
3. Forms of Shell Curvature
ā Singly Curved Shells (Developable)
- Curved on one linear axis
ā Ex. Barrel Shells
- Uses arch or beam action to transfer stresses
ā Doubly Curved Shells (Non - Developable)
- Synclastic: same sided curvature
ā Ex. Domes use hoop stresses and arch lines to transfer
forces, under compression
- Anticlastic: opposite sided curvature
ā Ex. Hyperbolic Paraboloids (Hypars) have simultaneous
tension and compression
Figure 10
Figure 11
Figure 12 Figure 13
5. Construction Techniques & Manufacturing
Continuous surface
ā Thin concrete
- Traditional timber formwork
- CNC moulds
- Fabric formwork
- Inļ¬atable structures
Discrete elements following that surface
ā Gridshell
- Prefabricated elements
Figure 8
Figure 9
6. Structural Premise & Basic Structural Formulas
ā Membrane Theory of Shells
- Loads distributed through in-plane axial and moment
forces known as Membrane Stresses
- Three Partial Differential equations describe membrane
stresses, require shape and boundary conditions
- Shell roofs, have compressive stresses following convex
curvature and tensile stresses following concave curvature
- Arch action often involved in structures with convex
curvature
ā Bending Theory of Shells
- Bending stiffness necessary to prevent buckling
- Different from form-active tensile systems
- Inextensional deformations introduce undesirable
bending stresses
Figure 14
Figure 14
7. Pros Cons
ā Very lightweight and efficient
ā Dead load can be reduced economizing
foundation system
ā Uses geometries that can span longer
distances, allows for large open spaces
ā Aesthetic
ā Double Parabola shape allows for large
stresses using thin shapes
ā Sudden collapse for shell structures
ā Great labor, supervision, and skill necessary
due to complexity
ā Environmental issues such as sealing,
leaking, condensation
ā Efficient structures may fail
catastrophically
Pros and Cons of Shell Structures
8. Mannheim Multihalle
Frei Otto and Architects Carlfried Mutschler and Winfried Langner
Structural Engineers Edmund Happold and Ian Liddell
1974
Gridshell Structure
Figure 1
9. "two kinds of artiļ¬cial hill - one of earth, one of grid shell"
Material: Hemlock
Span: 60m x 60m
Lath Size: 50 x 50mm at 0.5m
Bracing: Twin 6mm cables every 6th node
Deļ¬nition: āa double curved surface
formed from a lattice of timber laths
bolted together at uniform spacing in
two directionsā
Gridshell or Lattice Shell
Structure
Figure 2
12. Construction
Equal mesh square grid readily bent into shape
Deformation of grid squares into rhombi created a doubly curved surface
Continuous Shell: resists normal and shear forces
Lattice Shell: only resists forces in direction of the lath
Figure 7
Figure 9
Figure 8
23. Structure
- Hyperbolic Paraboloid shapes transfer
loads and create symmetry
- V beams transfer membrane stresses
from shell to points of supports
- Arch action is common in shell
structures in order to transfer forces to
supports
- Stresses in thin shells low compared to
strength of materials
25. Metal Dome Shell Structure
Modern Dome Proposal
ā 7,000 tonnes
ā 180 meters in diameter
Design Idea
ā Emphasis on light and shadow, reļ¬ection and
calm
ā Aesthetic matches its role as a sanctuary for
works of art
ā A shelter of light
ā Geometric design that relates to the local
culture
ā Floating atmosphere
Figure 2
Figure 3
26. Filtering Light
ā Superimposed layers of repeated pattern at
various sizes
ā Four outer layers clad in stainless steel and
four inner layers clad in aluminum separated
by a steel frame ļ¬ve meters high
ā 10,000 structural components pre-assembled
into 85 supersized elements
Construction Assembly
Figure 4
Figure 5
27. Structure
ā Supported by four symmetrically spaced,
nine-meter high concrete piers topped by a
single steel bearing
ā Bearing allows movement when the dome
expands and contracts during temperature
ļ¬uctuations
ā Dome shape allows forces to be
transferred to concrete piers through
combination of hoop stresses and arch
action in dome
Figure 6
Figure 7