57a and 57d of "Bridge Engineering" are to be employed, except that the cost for concrete in arch ribs is to be taken as $17.00 per cubic yard.

Problem C

Given the profile for a crossing, as shown in Fig. 17c, to determine the economic layout and the total weight of structural steel required for a double-track, steam-railway trestle to carry Class 55 live load.

Problem D

Given the profile for a crossing, as shown in Fig. 17d, to determine the economic span-lengths and to prepare a complete estimate of cost for a reinforced-concrete-girder structure to carry a thirty-six (36) foot roadway and two (2) sidewalks each six (6) feet wide in the clear, the roadway being paved with creosoted-wood blocks. An earth fill is to be used at each end, but the toes of the front slopes are not to extend beyond the points marked A and B on the profile. Abutments will not be employed, the end columns being buried completely in the embankments. The live loads are to be Class A for the roadway and Class B for the sidewalks. The permissible pressure on the foundations is to be three (3) tons per square foot. The depths of the footings below ground are to average six (6) feet.

The slopes for the fills are to be one and a half (1.5) horizontal to one vertical.

For unit prices of materials in place, the average costs given in Tables 57a and 57d of "Bridge Engineering" are to be employed.

These four problems were specially chosen for the purpose of making the competitors proficient in the quick computation of approximate quantities of materials and costs of structures, and to train their judgment in the important matter of the determination of best possible layouts for bridges.