The newly completed cable-stayed box girder bridge over the James River near Richmond, Virginia, has a 630-foot main span that is expected to set a new trend in the development of cable-stay bridges. Historically the cable-stay concept has been used for long spans of 800 feet or more--a range in which the unstayed box girder cross section is too heavy to be competitive. Now, however, bid results on the James River Bridge suggest that the cable-stay concept may have considerable merit in the 500- to 700-foot span range.
WHY SO COST EFFECTIVE?
Simplified design concepts and construction processes provide the key to success of this moderate span cable-stay. Cost-effectiveness of the project rests on maximum repetitiveness in both casting and erection operations. Identical precast box girder sections--a trapezoid with wide flanges or wings at the top--were used for the entire bridge, including approach spans and the cable-stayed center section.
The concept of repetition was carried through from the pile foundations to the main span erection cycle. In precasting, only four basic shapes--box piers, box girder segments, pylons, and delta frames--were produced.
SUBSTRUCTURE AND PYLONS
Foundations for the bridge rest on 24-inch-square prestressed driven piles with 250-ton service load capacity. The combined footings for the main span piers and pylon are supported by 88 piles.