Info

ft (m)

ft(m)

a

b

c

4 (1.219) 5.5 (1.676) 7 (2.134)

4 (1.219) 5.5 (1.676) 7 (2.134)

12 (3.658) 16.5 (5.029) 21 (6.401)

2 (0.610) 2.75 (0.838) 3.5 (1.067)

6 (1.829) 8.25 (2.515) 10.5 (3.200)

1 (0.305) 1.375 (0.419) 1.75 (0.533)

Notes:

1. Square shape S section is only for Column type 1.

2. Flare curve is parabolic and dimension C is only for Column type 3.

1. Square shape S section is only for Column type 1.

2. Flare curve is parabolic and dimension C is only for Column type 3.

FIGURE 25.41 Caltrans standard architectural columns: (a) Column types 1, 2, 3; (b) Column types 1W, 2W, 3W; (c) side view; and (d) front view (Caltrans 1990).

Diaphragm

Seat

Cantilever

Strutted

Rigid frame

Cantilever

Strutted

Rigid frame

FIGURE 25.42 Typical types of abutments: (a) open end; (b) closed end — backfilled; and (c) closed end — cellular (Caltrans 1990).

independently from the abutment while the diaphragm abutment does not. Since they have lower height of abutment walls, there is less settlement in the road approaches than that experienced by higher backfilled closed abutments. These also provide more economical widening than closed abutments.

25.6.3.2 Closed End Abutments

Closed end abutments include cantilever, strutted, rigid frame, bin, and closure abutments. These are less commonly used, but are used for bridge widenings of the same kind, unusual sites, or in tightly constrained urban locations. Rigid frame abutments are generally used with tunnel-type single-span connectors and overhead structures that permit passage through a roadway embankment. Because the structural supports are adjacent to traffic these have a high initial cost and present a closed appearance to approaching traffic.

25.6.4 Design Consideration

During the recent 1989 Loma Prieta and the 1994 Northridge Earthquakes in the United States and the 1995 Kobe Earthquake in Japan, major damages have been found in substructures. Special attention, therefore, must be paid to seismic effects and the detailing of the ductile structures. Boundary conditions and soil-foundation-structures interaction in seismic analyses should also be carefully considered. Chapter 20 addresses the seismic considerations.

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