John A. Roebling and the Design of Suspension Bridges 1. Methods of stiffening suspension bridges 2. Evolution of form in Roebling's suspension bridges 3. Wind and dangerous oscillations in suspension bridges 4. Ambiguity of form vs. structural redundancy in suspension bridges 5. Artistic representations of the Brooklyn Bridge Eiffel Eiffel Brunel
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John A. Roebling and the
Design of Suspension Bridges
1. Methods of stiffening suspension bridges
2. Evolution of form in Roebling's suspension bridges
3. Wind and dangerous oscillations in suspension bridges
4. Ambiguity of form vs. structural redundancy in suspension bridges
5. Artistic representations of the Brooklyn Bridge
Eiffel
Eiffel Brunel
Load Paths in Suspension Bridges
Weight of Bridge Deck
T
C C
TT
Shape of cable?
Parabola
Load Paths in Suspension Bridges
Vehicle on Bridge Deck
T
C C
T
T
C C
Bending
Deck or Truss
Cable
Force
1. Cables have Stiffness2. Force Follows Stiffness
StiffnessResistance to Deformation
Load Paths in Suspension Bridges
Vehicle on Bridge Deck
T
C C
T
T
C C
Bending
The Historical Record
Severely Damaged by Wind
Excessive Wind-Induced Motion
Longest Span
Buffalo Creek Bridge (1917) 113 ft span
Union Bridge (1820) 449 ft spanSamuel Brown England
Brighton Chain Pier (1823) 225 ft spansSamuel Brown England
Severely Damaged by Wind
Excessive Wind-Induced Motion
Longest Span
Menai Straits Bridge (1826) 580 ft spanThomas Telford Wales
C.L.M.H. Navier
Deformation !Weight
1Cable Stiffness:
Severely Damaged by Wind
Excessive Wind-Induced Motion
Longest Span
Wheeling Bridge (1849) 1010 ft spanCharles Ellett West Virgina
Niagara Railroad Bridge (1849) 822 ft spanJohn A. Roebling Niagara River
Severely Damaged by Wind
Excessive Wind-Induced Motion
Longest Span
John Augustus Roebling1806-1869
“The means employed are:
Weight, Girders, Trusses, and Stays.
With these any degree of stiffness can be insured, to resist
either the action of trains or the violence of storm . . .”
J.A. Roebling, Final Report, Niagara Bridge
Niagara Railroad Bridge (1849) 822 ft spanJohn A. Roebling Niagara River