Fig. 160.—Front View of Center for Short Elliptical Arch Spans.
Fig. 161.—Form for Parapet Wall for Arch Bridge.
For the five spans the total amount of lumber in the centers was in round figures 28 M. ft., distributed about as follows:
| Item. | Ft. B. M. |
| 1×6-in. sheeting | 5,600 |
| 2×6-in. longitudinal stringers | 2,600 |
| 2×6-in. cross stringers | 2,600 |
| 2×6-in. posts | 4,000 |
| 3×8-in. sills | 1,500 |
| 1×4-in. braces | 3,000 |
| Outer forms for spandrel walls | 4,000 |
| Inner forms for spandrel walls | 4,000 |
| ——— | |
| Total | 27,300 |
The aggregate span length of the arches was 276 ft., so that a little less than 100 ft. B. M. of lumber was used for centering per lineal foot of span. The superintendent at $5 per day and five carpenters at $3.50 per day erected the five centers in 18 days at a cost of $400, or a trifle more than $14 per M. ft. B. M.; the cost of taking down the centers was $2 per M. ft. B. M., and the lumber for the centers cost $24 per M. ft. B. M. making a grand total of $40 per M. ft. B. M. for materials and labor. As there were 1,000 cu. yds. of concrete in the arches and spandrels, the cost of centers and forms was $1.12 per cu. yd. This form lumber was, however, after taking down, used again in erecting a reinforced concrete building. Assuming that the lumber was used only twice, the cost of centers and forms for these five arches was less than 80 cts. per cu. yd. of concrete.
Shaping and Placing Reinforcement.—The 60 and 87-ft. spans were reinforced with 32 1-½-in. round longitudinal rods held in place by ½-in. square transverse rods wired at the intersections; the reinforcement of the smaller spans was exactly the same except that 1-in. diameter rods were used. To bend the longitudinal rods to curve, planks were laid on the ground roughly to the curve of the arch; the exact curve was marked on these planks and large spikes were driven part way into the planks along this mark. The end of a rod was then fastened by spiking it against the first projecting spike head and three men taking hold of the opposite end and walking it around until the rod rested against all the spikes on the curve. It took three men two 8-hour days to bend 46,000 lbs. of rods. Their wages were $2.50 each per day, making the cost of bending 0.03 ct. per pound, or 60 cts. per ton. It took a man 5 mins. to wire a cross rod to a longitudinal rod. With wages at $2.50 per day the cost of shaping and placing the reinforcement per ton was as follows:
| Item. | Per ton. |
| Bending rods | $0.60 |
| Shearing rods to lengths | 0.40 |
| Carrying rods onto bridge | 0.40 |
| Placing and wiring rods | 2.35 |
| —— | |
| Total | $3.75 |
Including superintendence the labor cost was practically $4 per ton, or 0.2 cts. per lb. Altogether 66,000 lbs. of steel was used for reinforcing 1,000 cu. yds. of concrete, or 66 lbs. per cu. yd. The cost of steel delivered was 2 cts. per lb., and the cost of shaping and placing it 0.2 ct. per lb., a total of 2.2 cts. per lb. or 2.2 × 66 = $1.45 per cu. yd. of concrete.