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F2018abnMembrane, Nets & Shells 1
Lecture 13
Applied Architectural Structures
ARCH 631
thirteen
membrane, net &
shell structures
lecture
Denver Airport – Birdair.com
APPLIED ACHITECTURAL STRUCTURES:
STRUCTURAL ANALYSIS AND SYSTEMS
ARCH 631
DR. ANNE NICHOLS
FALL 2018
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Lecture 13
Applied Architectural Structures
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Membrane and Net Structures
• form follows
pressure or
tension
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Membrane and Net Structures
• types
– fabric
– cables
– pneumatic
– inflated
http://nisee.berkeley.edu/godden
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Membrane and Net Structures
• sensitive to aerodynamic effects of wind
– fluttering
• stabilization
– rigid supporting framework
– prestressing of surface
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Membrane and Net Structures
• tensile stress and
tangential shear stresses occur
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Applied Architectural Structures
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Pneumatic Structures
• internal pressure
– air-supported:
entire volume
– air-inflated: cavities
• ribs
• dual walls
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Air-Supported Structures
• pressure slightly
higher than
atmospheric
• light loads
• greater spans than
air-inflated
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Applied Architectural Structures
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Air-Inflated Structures
• higher degree of
pressurization
• pressure doesn’t
directly balance
loads
• buckling or folding
results in collapse
• flexibility in space
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Loads & Behavior
• snow accumulation
– shape
– heat loss
• avoid large
concentrated loads
• wind loads
– suction
– tension
– “buckling”
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Applied Architectural Structures
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Membrane Stresses
• pressure is constantly applied stress
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Applied Architectural Structures
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Membrane Stresses• enough pressure to prevent folding
• large radius, large stress
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Applied Architectural Structures
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Supports
• air-supported
– need airtight
seal
– resists uplift
and thrust
– “inverted” arch
– containment
rings
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Applied Architectural Structures
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Profile Selection
• lower profile
– higher stresses
– lower air volume
– can be used to avoid
wind pressure effects
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Applied Architectural Structures
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Air-Inflated Members
• prestressed in
tension
• structural stresses
added
• increase in tension
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Applied Architectural Structures
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Punctures
• fracture or rip from redistribution of
stresses
• air-supported
– low pressure
– gradual deflation
• air-inflated
– isolated cells deflate
• design in suspension
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Applied Architectural Structures
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Net and Tent Structures
• low curvatures, high stress (big radius)
• avoid flat areas
• carefully place high & low points
Basic Types of Tensile Structures (© Tentech)
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Applied Architectural Structures
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Support Conditions
• compression masts
• uplift at ground
• free edges can
be stiffened with
cables
• stress reduction
at high points
by a cable ring
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Applied Architectural Structures
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Form Development
• modeling
• software
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Applied Architectural Structures
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Materials
• strength
– tear resistant
– bi-directional
• durability
– ultraviolet
effects
– creep
– corrosion in metals
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Applied Architectural Structures
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Shells
• similar to membranes, domes & vaults
• THIN
• rigid
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Shells
Empire State Performing Arts Center, Ammann & Whiney
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Applied Architectural Structures
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Shell Types
• shape classifications
– developable: • singly curved (vault)
– synclastic• doubly curved
• same direction
– anticlastic: • doubly curved
• opposite curvature
– free form
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Synclastic
• surface of revolutions
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Applied Architectural Structures
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Shell Stresses
• in-plane
– tension
– compression
– shear
• insignificant
bending
• suitable for distributed loads
• can’t handle concentrated loads well
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Applied Architectural Structures
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Spherical Shells
• arch of revolution
• compression
• some tension
– “bow”
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Applied Architectural Structures
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Forces in Spherical Shells
• similar to plates
– two directions of forces
– shear
– maintain curvatures
• meridional– arch direction
• hoop – radial direction
– can see tension
• holes redistribute stresses
– edges need reinforcement
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Applied Architectural Structures
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Meridional and Hoop Forces
• meridional force per unit length:
• hoop force per unit
length:
22 sinRπ
WN
cos
cosRwN θ
1
1
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Lecture 13
Applied Architectural Structures
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Distribution and Concentrated Forces
• size distributions
• concentrated force
causes
R.
R)'cos(
620
4951
N
0.6
2 R
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Applied Architectural Structures
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Support Conditions
• absorb horizontal thrust
– tension ring
– being pushed out
– need to be continuous
– can be used as foundation
• top (crown) rings
– in compression
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Applied Architectural Structures
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Support Conditions
• buttresses
• edge restraint effects
– deformations different
– fixed edges• bending stress
• deep section
– pinned edges• still induces bending
– post-tensioning helpsstiffen
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Applied Architectural Structures
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Buckling & Lateral Loading
• instability
– compression
– moment of inertia
– low stress levels
• local
• snap-through
• lateral loading
– shear
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Annunciation Greek Orthodox Church
• Wright, 1956
http://www.bluffton.edu
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Applied Architectural Structures
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Annunciation Greek Orthodox Church
• Wright, 1956
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Applied Architectural Structures
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Cylindrical Shells
• can resist tension
• shape adds “depth”
• not vaults
• barrel shells
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Applied Architectural Structures
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Kimball Museum, Kahn 1972
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Applied Architectural Structures
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Kimball Museum, Kahn 1972
• outer shell edges
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Applied Architectural Structures
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Kimball Museum, Kahn 1972
• skylights at peak
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Applied Architectural Structures
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• saddle or “ruled” shapes
• surface generated with straight lines
• tension follows “cable drape”
• compression follows “arch”
Anticlastic Shells (Hyperbolic Paraboloid)
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Applied Architectural Structures
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Anticlastic Shell Behavior
• edge conditions offer restraint
– tie rods useful
– shears
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Applied Architectural Structures
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Zarzuela Hippodrome, Torroja 1935
http://www.arch.mcgill.ca
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Applied Architectural Structures
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Zarzuela Hippodrome, Torroja 1935
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Applied Architectural Structures
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Heilmajer Memorial Bandstand
• Kramer, 2002
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Lecture 13
Applied Architectural Structures
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Heilmajer Memorial Bandstand
• Kramer,
2002
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Lecture 13
Applied Architectural Structures
ARCH 631
Heilmajer Memorial Bandstand
• Kramer, 2002
F2018abn
Videos
Membrane, Nets & Shells 45
Lecture 13
Applied Architectural Structures
ARCH 631
BC Place roof replacement
Canada Place roof rehabilitation