There are no restrictions as to span-lengths or locations of piers, because the river is not navigable.

The type of floor is the ordinary one of untreated wooden ties and
guards with eighty (80) pound rails.

The live load is Waddell's Class 60.

The following are the costs of the various materials delivered at site:

Cement two dollars ($2.00) per bbl.

Broken stone and gravel, one dollar and fifty cents ($1.50) per cubic
yard.

Sand (clean and ready for use), one dollar ($1.00) per cubic yard.

Timber, twenty-two dollars ($22.00) per M. feet B. M.

Piles, twenty (20) cents per lineal foot.

Structural steel, 4.5 cents per pound for truss spans and 4.2 cents per
pound for plate-girder spans.

Rails, forty-two dollars ($42.00) per long ton.

The following are the schedule costs of the erection work:

Sinking of pneumatic caissons, five dollars ($5.00) per cubic yard.

Sinking by open-dredging, three dollars and fifty cents ($3.50) per cubic
yard.

Driving piles for trestle, twenty (20) cents per lineal foot.

Driving piles for foundations, forty (40) cents per lineal foot.

Erection of metal, including cost of falsework and painting, 1.2 cents per
pound for truss spans and 0.8 cent per pound for plate-girder spans.

The problem is to determine the extreme high-water profiles both before and after the structure is completed, to make an economic layout of spans, piers, and abutments for the proposed bridge, and to prepare an estimate of cost of the finished structure, exclusive of the earth embankments.

Problem B

Given the profile for a dry-gulch crossing, as shown in Fig. 17b, to determine, for a combined highway-and-electric-railway, reinforced-concrete arch bridge, having a clear roadway of forty-four (44) feet and two sidewalks each eight (8) feet wide in the clear, the quantities of all the materials in the structure and an estimate of its cost excluding the earth fills.

The live loads are to be taken as follows:

     For the electric railway, Class 25.

     For the wagonways, Class B

     For the sidewalks, Class C.

Permissible pressure on foundations, five and a half (5.5) tons per square foot.

Arches are to be of the ribbed type with two (2) lines of ribs.

Average depth of excavation for foundations is to be six (6) feet.

For unit prices of materials in place, the average costs given in Tables