Erection of CableStayed Bridges Having Composite Decks with

Erection of Cable-Stayed Bridges Having Composite Decks with Precast Concrete Slabs

Erection of Cable-Stayed Bridges • Overview of cable-stayed bridges • Types of cable-stayed bridge decks • Erection methods and analysis • Conclusion

Cable-Stayed Bridges • The known use of cable “stays” dates back to ancient Egyptian times

Cable-Stayed Bridges • Modern use of cable-stayed bridges evolved in 1950’s (Germany)

Advantages of Cable-Stayed Bridges • Economical choice for spans between 200 and 1000 meters • Self-anchoring during construction • React to live loads with only small deformations • Easily constructed by cantilever method

Concrete Bridge Decks • Used for spans up to 350 m • Axial forces induced into the deck by cable stays serve as a cost-free prestress

Composite Bridge Decks • Advantageous for spans from about 350 m to 700 m • Axial forces induced into the deck by cable stays serve as a cost-free prestress

Steel Girder w/ Orthotropic Decks • Advantageous for spans greater than 700 m

Erection of Cable-Stayed Bridges • Cantilever style construction • Goal is to prevent locked in curvature and bending moments in bridge deck

Pure Concrete Deck Cable Tensioning • Proper one-step tensioning will yield this dead load configuration Dead Load Configuration: Full deck loads, w, and deck moments, M

Pure Concrete Deck Cable Tensioning 1 2 3 4

Pure Concrete Deck Cable Tensioning

Erection of Cable-Stayed Bridges. . • Methods of erecting cable-stayed bridges having concrete or orthotropic decks are fairly well established. • However, erection methods/analysis of composite decks with precast concrete slabs are not well published.

Composite Deck Cable Tensioning • One-step tensioning processes lock in initial deck curvature and moments

Construction Stages for Two-Step Composite Deck Cable Tensioning Steel stage • Erection of pre-fabricated steel grid

Construction Stages for Two-Step Composite Deck Cable Tensioning Panel stage • Placement of precast concrete slabs on steel grid • Cables are tensioned as the first step of tensioning

Construction Stages for Two-Step Composite Deck Cable Tensioning Freeze stage • Survey is conducted to check precision of grid geometry and cable forces • Joints between precast concrete slabs are cast; resulting deck acts continuously and compositely

Construction Stages for Two-Step Composite Deck Cable Tensioning Final stage • After sufficient deck strength is realized, cables are stressed to their final lengths (second step of tensioning)

Two-Step Composite Deck Cable Tensioning Deck shape with zero overall curvature

Two-Step Composite Deck Cable Tensioning

Further Considerations

In Conclusion…