timber structures - myoops.org · timber structures! review of masonry mechanics! merits of wood as...
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Timber StructuresTimber Structures
! Review of masonry mechanics
! Merits of wood as a structural material
! Possibilities in wood structure
! Technical concepts:– Modulus of Elasticity (stiffness)– Bending moment diagrams
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Masonry StructureMasonry Structure
! Must act in compression (no resistance to tension)
! Very high compressive strength– Design is a problem of form– Stability and not strength limits masonry
! Thrust line: line of forces acting within a masonry structure to ensure that compression is maintained
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Construction ProcessConstruction Process
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Construction ProcessConstruction Process
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Construction ProcessConstruction Process
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Construction ProcessConstruction Process
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Masonry Design: Line of Thrust Masonry Design: Line of Thrust must be within the masonry must be within the masonry
P
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EladioEladio DiesteDieste (1917(1917--2000)2000)
! Trained as a civil engineer in Uruguay
! 1947: Completed Casa Berlingieri with his first use of reinforced brick
! 1960: Completed Church of Atlantida
! 1995: Retrospective of his career held in Spain
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The Future of Brick VaultingThe Future of Brick Vaulting
! Reasons for superiority of brick over reinforced concrete for thin shells:– Less cement– Formwork is removed much more quickly– Vaults are more lightweight– Easier to achieve double curvature with brick
! Low stresses in well-designed shells
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The Future of Brick VaultingThe Future of Brick Vaulting
The things that we build must have something that we could call cosmic economy, that is to be in accord with the profound order of the world.
-Eladio Dieste
! The need for sustainable structures will require us to combine traditional methods of construction with new technologies.
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Only one primary building material comes from a renewable resource, cleans the air and water; utilizes nearly 100% of its resource for products; is the lowest of all in its energy requirements for its manufacturing; creates fewer air and water emissions than any of its alternatives; and is totally reusable, recyclable and 100% biodegradable. And it has been increasing in US net reserves since 1952, with growth exceeding harvest in the US by more than 30%.
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American Wood CouncilAmerican Wood Council
Only one primary building material comes from a renewable resource, cleans the air and water; utilizes nearly 100% of its resource for products; is the lowest of all in its energy requirements for its manufacturing; creates fewer air and water emissions than any of its alternatives; and is totally reusable, recyclable and 100% biodegradable: WOOD. And it has been increasing in US net reserves since 1952, with growth exceeding harvest in the US by more than 30%.
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Properties of TimberProperties of Timber
! Cellular structure is very efficient! Handles both compression and
tension well! Different strengths with and against
the grain! Inhomogeneous material with
imperfections
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Progress Ideology of MetalProgress Ideology of Metal
! Airplane designers from 1920-1940 neglected wood, though it was superior to metal in many design considerations.
! Engineers linked metal with technical progress: “wood was anathema to the ideals of precision and power”.
! Article by Schatzberg, Technology & Culture, January, 1994.
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Stiffness (E) per unit weightStiffness (E) per unit weight
0
5
10
15
20
25
30
Wood Brick Concrete Steel Aluminum
(MN
-m/k
g)
Source: Biggs (1991)
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0
200
400
600
800
1000
1200
1400
1600
1800
Wood Brick Concrete Steel
Embodied Energy per StiffnessEmbodied Energy per Stiffness(k
J/M
N-m
)
Source: Biggs (1991)
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Embodied Energy per StiffnessEmbodied Energy per Stiffness
Wood Brick Concrete Steel Aluminum
(kJ/
MN
-m)
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
Source: Biggs (1991)
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Japanese Pavilion, Hanover, 2000Japanese Pavilion, Hanover, 2000
Image courtesy Nicolas Janberg, http://www.structurae.de/en/photos/img418.php
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Expo Pavilion, Hanover, 2000Expo Pavilion, Hanover, 2000
Image courtesy Nicolas Janberg, http://www.structurae.de/en/photos/img696.php
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ConclusionsConclusions! Wood is a highly engineered, sustainable
material– Underused: many possibilities for wood as a
structural material
! Stiffness (modulus of elasticity) measures the deformation in relation to an applied load
! Bending moments for simply-supported beams can be derived from the hanging cable for the given loading
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Material PropertiesMaterial Properties
269180238000270070000Al
271597430007800210000Steel
117388300240027000Concrete
171682800180030000Brick
2253117050011000Wood
Energy/stiffnessEnergy
kJ/kgDensitykg/m3
StiffnessMN/m2
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17010000Al
49029000Steel
1503000Concrete
1303100Brick
3011000Wood
Densitylb/ft3
Stiffness ksi
Material PropertiesMaterial Properties