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STRESS RIBBON BRIDGE

Presented By:TONY ROSE

Roll :1523009NIT PATNA

OVERVIEW• Introduction

• Form of a stress ribbon bridge

• Construction techniques

• Modified stress ribbon bridge

• Advantages

• Applications

• Recent advances

• Conclusion

• References

2SEMINAR ON STRESS RIBBON BRIDGE

IntroductionWhat 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.

3SEMINAR ON STRESS RIBBON BRIDGE

Catenary profile of a stress ribbon bridge

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.

SEMINAR ON STRESS RIBBON BRIDGE 4


Stress ribbon bridge: Modern analogy of ROPE BRIDGE

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.



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 .

Form of a Stress Ribbon Bridge


Form of a stress ribbon bridge

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.



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.

deck Lake Hodges Bridge, USA

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.


• 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.


Construction Techniques(Contd.)

Modified stress ribbon bridgesStress ribbon bridges stiffened by arches


Modified stress ribbon bridges(Contd.)

Stress ribbon bridges suspended on arches



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


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

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:


ApplicationsEcoduct Stuttgart trade fair hall roof


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%


World’s longest stress ribbon bridge in Cuenca ,Spain

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.


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


THANK YOU..


THANK YOU..

tony

Engineering