Prestressed Precast Concrete Railroad Bridges

Abstract

Prestressed, precast hollow concrete box girder units are now being used extensively for underpasses, trestle renewal and stream bridges by major Western U.S. railroads. Historical development and current details of design, fabrication and methods of erection are presented, with special attention to 34 bridges totaling 2,350 linear feet on Southern Pacific's 78-mile Palmdale-Colton line in Los Angeles and San Bernardino Counties, completed in 1067. Girders were fabricated in Arizona and transported by rail to site. Double-cell box girders form spans to 45 ft, and multiple single cell girders, weighing up to 70 tons each, for spans to 86 ft. Epoxy grout joins the boxes together longitudinally. The upper surface of the box serves as the floor for the railroad-ballasted track section. The boxes are supported on elastometric pads. Most economical bridges were 45-ft spans with open-end abutments. This type of construction expected to be economical for spans substantially in excess of 86 ft.