| 48 | ECONOMICS OF BRIDGEWORK | Chapter V |
Nichro Steel
| 95,7 lbs. Steel | @ 8.5¢ = $8.13 |
| 1.0 lb. Chromium | @ 25¢ = 0.25 |
| 3.3 lbs. Nickel | @ 43¢ = 1.42 |
| 100.0 lbs. Alloy | @ 9.80 = $9.80 |
|
Nichromol Steel |
| Working tensile stress for heat-treated steel | = 47,300 lbs. |
| Ditto untreated (approximately) | = 37,500 lbs. |
| Average= 1/3 (2 X 37,500 + 47,300) | = 40,800 lbs. |
Nichro Steel
| Working tensile stress for heat-treated steel | = 45,000 lbs. |
| Ditto untreated (approximately) | = 35,500 lbs. |
| Average = 1/3 (2 X 35,500 + 45,000) | = 38,700 lbs. |
|
and r r' = 1.094 X 0.949 = 1.038
Referring to Figs. 5a and 5b, it is seen that the simple-span length corresponding to this product is about 600 feet and the main opening for a Type A cantilever is about 1,600 feet; and as most spans are below this limit, it appears probable that there is seldom any economy in adding molybdenum to chrome-nickel steel for the manufacture of bridges; but the data used for this investigation are so crudely approximate that this conclusion requires corroboration. It would need some elaborate and expensive experimenting to determine this economic point with accuracy. The addition of the molybdenum, though, would undoubtedly improve the quality of the alloy by increasing its resistance to shock. Chrovanmol Steel versus Chrovan SteelReferring to Tables 5e and 5f, we have the following: Chrovanmol Steel |
| 97.92 lbs. Steel | @ 8.5¢ = $8.32 |
| 1.06 lbs. Chromium | @ 25¢ = 0.27 |
| 0.17 lb. Vanadium | @ $10.00 = 1.70 |
| 0.85 lb. Molybdenum | @ $2.53 = 2.15 |
| 100.00 lbs. Alloy | @ 12.44¢= $12.44 |