998

FIGURE 25.33 Caltrans precast standard T'-girder (Caltrans 2001).

FIGURE 25.33 Caltrans precast standard T'-girder (Caltrans 2001).

girders can be taken as twice the structural depth. It is used mostly for spans of 100 to 600 ft (30.5 to 182.9 m). Structural depth-to-span ratios are 0.045 for simple spans and 0.04 for continuous spans. These sections are used frequently for simple spans of over 100 ft (30.5 m) and are particularly suitable for widening in order to control deflections. About 70 to 80% of California's highway bridge system is composed of prestressed concrete box girder bridges.

25.5.3.4 Segmental Concrete Bridge

The segmentally constructed concrete bridges have been successfully developed by combining the concepts of prestressing, box girder, and the cantilever construction (Podolny and Muller 1982; AASHTO 1999). The first prestrssed segmental box girder bridge was built in West Europe in 1950. California's Pine Valley Bridge as shown in Figure 25.37 and Figure 25.38 (composed of three spans of 340 ft (103.6 m), 450 ft (137.2 m), and 380 ft (115.8 m) with the pier height of 340 ft (103.6 m)) is the first cast-in-place segmental bridge built in the United States in 1974.

The prestressed segmental bridges with precast or cast-in-place segmental can be classified by the construction methods (1) balanced cantilever, (2) span-by-span, (3) incremental launching,

Section properties

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