South Watt Avenue LRT Grade Separation

Sacramento, Calif.

This five-span, 539-ft-long bridge carries two light rail tracks over a heavily congested corridor and is in close proximity to a freight rail line. The all-precast through-girder superstructure consists of three precast/prestressed girders spanning in the longitudinal direction, and precast/prestressed concrete slabs spanning between adjacent girders in the transverse direction. The longitudinal girders were post-tensioned following the erection and stressing of the transverse slab tendons.

The sides of the trough are formed by allowing the supporting girders to project above the deck; this is in contrast to conventional deck sections that are supported from below. As a result, the structure depth required for a trough section is substantially less than for the conventional types. This allows the profile grade to be lowered, and avoids all costs associated with a raised profile. The structure highlights an important benefit of precast concrete that is often overlooked: how the all-precast cross section itself was transversely integrated into a “super girder.”

This concept opens the door for a new generation of all-precast super girders that are fabricated in segments, transported, and then field assembled into a single deck element. The additional flexibility afforded by such systems enables them to economically meet a wider range of functional requirements than conventional precast systems.

Precaster: Con-Fab California Corp.
Website: www.confabca.com

Engineer of record: AECOM Transportation
Website: www.aecom.com

Deck area: 14,014 ft²
Bridge length: 539 ft 0 in.
Longest span: 117 ft 0 in.
Bridge width: 36 ft 4 in.
Components:
(2)  6’-0” deep x 3’-0” wide x 77’-0” long voided box girder
7’-0” deep x 3’-0” wide x 77’-0” long voided box girder
(6)  6’-0” deep x 3’-0” wide x 115’-0” long voided box girder
(3) 7’-0” deep x 3’-0” wide x 115’-0” long voided box girder
(2) 6’-0” deep x 3’-0” wide x 117’-0” long voided box girder
7’-0” deep x 3’-0” wide x 117’-0” long voided box girder
(120)  precast deck slab units
MSE wall, 14’-0” high x 25’-0” long panels
(12)  MSE wall, (6’ thru 14’ high) x 37’-6” long panels
MSE wall, 12’-0” high x 50’-0” long panels
(2)  MSE wall, 8’-0” high x 62’-6” long panels