stress ribbon bridges

1. STRESS RIBBON BRIDGE
Presented By:
TONY ROSE
Roll :1523009
NIT PATNA

2. OVERVIEW
• Introduction
• Form of a stress ribbon bridge
• Construction techniques
• Modified stress ribbon bridge
• Advantages
• Applications
• Recent advances
• Conclusion
• References
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3. Introduction
What is stress ribbon bridge?
 Special type of suspension bridge where in the cables are
embedded in the deck just below the walking surface.
 Bridge follows a catenary (funicular) profile and sags
between supports.
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Catenary profile of a stress ribbon bridge

4. Introduction(Contd.)
 Uses the theory of a catenary transmitting loads via tension in the deck to
abutments which are anchored to the ground.
 Concept was first introduced by a German engineer Ulrich Finsterwalder.
 Prestressing the deck segments stiffens the structure, providing stability to
the cables.
 The first stress ribbon bridge was constructed in Switzerland in the
1960s.
 The new bridge at Lake Hodges is the sixth ribbon bridge in North
America, with three equal spans of 330 feet is the longest of this type.
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Stress ribbon bridge: Modern analogy of ROPE BRIDGE

6. Finsterwalder’s Stress Ribbon
Bridge Theory :
 Stress ribbon bridge combines a suspended concave span
(radius= 8200ft) and a supported convex span (radius
9800ft,based on design speed of bridge).
 The stress ribbon itself is a reinforced concrete slab
(thickness=25.4cm).
 Reinforcement consists of three to four layers of 1 inch (2.5cm) to
1 ¼ inch (1.2cm) diameter, high strength steel.
 Layers are spaced so that the prestressing pipe sleeve
couplings can be used as spacers both vertically and horizontally.
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 To resist bending moments from traffic, the slab is heavily
reinforced at the top and bottom in the transverse direction.
 The high strength steel tendons are stressed piece by piece
during erection to produce the desired upward deflection .
 A temporary catwalk is provided to stress the first tendons.
 Concrete is placed from the middle of the freely hanging 63
suspended concave part and continues without interruption to
the supports .

8. Form of a Stress Ribbon Bridge
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Form of a stress ribbon bridge

9.  Superstructure
1. Stress ribbon bridge deck consists of precast concrete planks with bearing
tendons to support them during construction and separate prestressing
tendons which are tensioned to create the final designed geometric form.
2. The prestressing tendons transfer horizontal forces in to the abutments
and then to the ground most often using ground anchors.
 Substructure
1. The abutments are designed to transfer the horizontal forces from the
deck cables into the ground via ground anchors.
2. The ground anchors are normally tensioned in 2 stages, the first step is
tensioned before the deck is erected and the rest, after the deck is complete.
3. The soil pressure, overturnings and sliding has to be checked for
construction.
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10.  Ground Conditions
1. The ideal ground condition for resisting large horizontal forces from the
ribbon is a rock base.
2. In some cases where soil conditions do not permit the use of anchors,
piles can also be used.
3. Battered micropiling is another alternative which can resist the load from
the ribbon because of its compression and tension capacity.
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deck Lake Hodges Bridge, USA

11. Construction Techniques
• Abutments and piers are built.
• Bearing cables are stretched from abutment to abutment and
draped over steel saddles that rested atop the piers.
• Precast panels are suspended via support rods located at the four
corners of each panel. At this point the bridge sagged into its
catenary shape.
• Post tensioning ducts are placed directly above the bearing cables
and support rods .
• The cast-in place concrete was placed and is allowed to harden
before the final tensioning is carried out.
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12. • Once the concrete is cured and achieved its full strength, the bridge
is post tensioned.
• The post tensioning lifts each span, closes the gap between the
panels, puts the entire bridge in to compression and transforms the
bridge in to continuous ribbon of prestressed concrete.
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Construction Techniques(Contd.)

13. Modified stress ribbon bridges
Stress ribbon bridges stiffened by arches
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14. Modified stress ribbon bridges(Contd.)
Stress ribbon bridges suspended on arches
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15. Static loading test
• 1.Vehicles were placed on the entire length of the
bridge
• 2.Vehicles placed on each span
• During the test only the deformations in the middle
of the spans and the horizontal displacements of all
supports were measured
» Prague troja bridge ,Czech Republic
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16. Comparison with simple suspension bridge
• Similar in many ways to simple suspension bridge
• But the suspension cables are embedded in the deck
slab
• In suspension bridge cables carry the load, but in
stress ribbon bridges the highly stiffened deck
shares the axial tension
• Comparing to simple suspension bridges,both sway
and bounce are less in stress ribbon bridges
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17. Advantages
• Stress ribbon pedestrian bridges are very economical,
aesthetical
• Minimal environmental and visual impact
• Can be erected without falsework or shoring
• Minimal long-term maintenance is required
• Are highly desirable at places as shown below:
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18. Applications
Ecoduct Stuttgart trade fair hall roof
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19. Recent Advances
• Innovative design uses unidirectional
solid carbon fibre cables (TSC).
• Unsupported spans were
significantly increased
• Supporting structure was
reduced
• Installation time and cost
were reduced by over 80%
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World’s longest stress ribbon bridge in Cuenca ,Spain

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21. Conclusion
• Stress ribbon bridges are a versatile form of bridge.
• Slender decks are visually pleasing and have a visual
impact on surroundings giving a light aesthetic
impression.
• Post tensioned concrete minimises cracking and
assures durability.
• Bearings and expansion joints are rarely required
minimising maintenance and inspections.
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22. References
• Roma Agrawal, (2009), Stress ribbon bridges, The structural
engineer, pp 22-27
• Tomas Kulhavy, (1998), Stress ribbon bridges stiffened by arches or
cables, 2nd Int’l phd symposium in civil engineering, Budapest.
• Tony Sanchez, (2010), Path to safety, ASCE journal, pp 68-76.
• Stress Ribbon Bridges: Mechanics of the Stress Ribbon on the
Saddle Arndt Goldack1; Mike Schlaich2; and Moritz Meiselbach
• . Preliminary design of prestressed concrete stress Ribbon bridge
By Diego Cobo del Arco,1 A´ ngel . Aparicio,2 and Antonio R. Marı´,3
Member, ASCE
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23. THANK YOU..
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