This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
In Figs. 234 and 235 are shown the details and sections of two reinforced-concrete arches having fixed abutments, which have been recently erected. The first bridge has a nominal span of 60 feet between the , two faces of the abutments. On account of the great thickening of the arch rib near the abutment, the virtual abutments are practically at points which are approximately 2G feet on each side of the center. The method of reinforcing the spandrel and parapet walls is clearly shown in the figure. The side view also gives an indication of some buttresses which were used on the inside of the retaining walls above the abutments in order to reinforce them against a tendency to burst outward.
Fig. 235 shows a bridge which is slightly oblique, and which spans a double-track railroad. The perpendicular span between the abutments is 34 feet, but the span measured on the oblique face walls is 35 feet 8 inches. In this case, similarly, the arch is very rapidly thickened near the abutment, so that the virtual abutment on each side is at some little distance out from the vertical face of the abutment wall. In both of these cases, the arch rib was made of a better quality of concrete than the abutments.
The arch of Fig. 234 was designed for the loading of a country highway bridge; that of Fig. 235 was designed for the traffic of a city street, including that of heavy electric cars.