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CHAPTER 4: THE CONSTRUCTION PROCESS OF SEGMENTAL BRIDGES - page 24 / 47

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Chapter 4: The Construction Process of Segmental Bridges

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Two different techniques for launching the bridge superstructure from the casting bed exist. Hydraulic jacks can pull the superstructure with steel rods, as it was done for the Rio Caroní Bridge (Podolny and Muller 1982). The second, more common method is to employ a pair of hydraulic jacks acting vertically and horizontally. Continuous repetition of lifting the superstructure off the abutment and then pushing it forward as far as the jack allows will achieve the launching in incremental steps. Figure 4-7 shows the launching process schematically. Podolny and Muller (1982) caution to design the jack capacity for more than the usual friction coefficient of 2 % because of imperfections that can occur during construction.

Incremental Launching, Step 1

Direction of Advancing

Casting Yard

Launching Nose

Temporary Support

Incremental Launching, Step 2

Direction of Advancing

Figure 4-7: Incremental Launching

In front of the cantilevering superstructure a lightweight steel launching nose is attached with tendons that reaches the next support before the bridge superstructure itself arrives. Its purpose is

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