Railroad Gazette/Volume 38/Number 5/Reinforced Concrete Floor
Reinforced Concrete Floor for Deck Girders.
Several of the more important bridge designs used on the Eastern Illinois & St. Louis R. R., the connecting link by which the Frisco’s Chicago–St. Louis line was established, were described in these columns when the road was being built (Railroad Gazette, June 12, 1903). Since that time an interesting design of reinforced concrete
Reinforced Concrete Floor for Deck Girders.
Details of Bent Reinforcing Bars.
deck floor has been applied at Villa Grove, a drawing of which is shown herewith. The bridge consists of three 30-ft. and one 40-ft. span. When the design was prepared the intention was to build the floor in slabs 6 ft. wide at some convenient point and place them on the girders afterward but before beginning the work this plan was changed. Instead of a series of 6-ft. slabs side by side, each track floor was built in place on the girders, and made continuous, with expansion joints coinciding with those of the girders beneath.
For each track, the floor is 10 in. thick at the center and 7 in. thick at each side, with a straight bottom and crowned top, the side-drainage drop being therefore 3 in. A parapet 1 ft. 9 in. high and 1 ft. thick is formed at the outer edge with 2-in. iron pipe drains spaced 6-in. centers, at the inner corners. Between tracks a 1-in. space is left for drainage. Johnson corrugated bars are used for reinforcement, ¾-in. bars transversely and ½-in. bars longitudinally. The top transverse bars are 6 in. on centers, 1½ in. below the surface and parallel thereto. The bottom bars are 4½ in. on centers, with every other bar bent as shown in the detail sketch, to take care of the shearing stresses. The parapet has short vertical lengths of ½-in. bars close to the inner face and laid to 12 in. centers. The longitudinal bars are also spaced 12 in. Gravel concrete was used, the mixture being in the proportion of one barrel of cement to each cubic yard of concrete.
The bridge is designed for Cooper’s E-50 loading. The total dead load per lineal foot of track above the girders is 3,000 lbs., one-half of which is in the concrete deck. The estimated cost of this deck is $5.25 per lineal foot of single track. The bridge was designed by Mr. T. L. Condron, M. Am. Soc. C. E., Consulting Engineer, Chicago, under the direction of Mr. W. S. Dawley, Engineer Maintenance of Way of the Chicago & Eastern Illinois. The bridge is located at the end of a switching yard and in order to permit switchmen to pass across freely when cars are on the bridge, a sidewalk is being built on each side of it, supported by cantilever beams running over the parapet and bolted to the deck.