WING ABVTnz rrs. Cooper's Standard. Fig. 131, page 541, shows an abutment with splayed wings recommended for country highway and electric railway bridges.t The variable dimensions of the top of the abutment are given in Table 80, page 540. This form is intended to be built of either masonry or plain concrete.
New York Central Standard. Fig. 132, page 541, shows the standard straight and also the splayed-wing, plain-concrete abutments of the New York Central and Hudson River Railroad.* Ordinarily the form with straight wings is used for street crossings and that with splayed wings for stream crossings. Notice that the wing has a coping and that the top face is curved. Compare the finish of this wing with that of Fig. 130.
The following are notes from the official drawing: "1. The dimen sion y, see top of Section, varies with the superstructure, but is not less than 3 feet for girders and trusses or 2 feet 6 inches for solid floors. 2. The dimension x, see top of Section, is at least half the distance from the bridge seat to the base of the rail. 3. The frost batter, see upper right-hand corner of Section, is to slope 6 inches in 5 feet. 4. The angle of the face of the wing with the face of the abutment is varied to suit the local conditions. 5. The foundation is made to suit local conditions, but must not be less than 4 feet deep unless good rock is found. 6. Old rails 10 to 12 inches center to center are to be used where a soft foundation is found; and where piles are not used, the base of the rails is to be 6 inches from the bottom. Where splicing of rails in the foundation is necessary, they shall be fully bolted with two splice bars, and be laid with broken joints. 7. The back filling is to be cinders or other porous material.
8. All exposed corners and edges are to be rounded to a 1-inch radius.
9. The bridge seat is reinforced with a sheet of Clinton galvanized wire cloth, having 3-.by 8-inch mesh, made of No. 8 and 10 wires, or with No. 8 Clinton wire netting having 1- by 2-inch mesh." Wing Abutment. Fig. 133 shows a typical form of reinforced-concrete bridge abutment built by the Wabash Railway at Monticello, Ill.* The figure shows the dimen
sions and the general form of construction. On the face of the abut ment proper and of the wings is a little ornamentation, in the shape of a rectangle, produced by nailing a half-round strip on the inside of the forms. This ornamentation is not shown in Fig. 133. In this particular structure the counterforts (the vertical walls behind the face wall) are parallel to the roadway, but sometimes the coun terforts to the wings are perpendicular to the face wall.
One of the two abutments like that shown in Fig. 133 contains 160 cu. yd. of concrete and 9,581 lb. of i-inch square corrugated steel reinforcing bars, and the other 182 cu. yd. of concrete and 13,043 lb. of steel, both being practically 60 lb. per cu. yd.
In § 1065 is a discussion of the relative cost of plain- and reinforced-concrete retaining walls, all of which is applicable to abutments; but the more complicated form of the reinforced-concrete abutment makes the additional cost of forms and the extra trouble of depositing concrete around the reinforcement greater for abutments than for retaining walls; and hence it is probable that under ordinary conditions the plain-concrete abutment is the cheaper. Further, on account of the possibility of the rusting of the reinforcement, the plain-concrete abutment is more durable.