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Competition for students on
cost estimating, 141
Compressed air for bridge operation, 311
Compression flanges of beams,
intensities for, 137
Compression members,
box sections for, 261
economic sections of, 199
Computations, checking of, 359
Computing, short cuts in, 92
Concluding suggestion by
author, 487, 488
Conclusion, 486
Concrete (see also Reinforced
Concrete)
aggregate, prices of, 23
volume of voids in, 386
amount of water for mixing, 392
arch-spans, erection of, 406
best proportion of materials
for, 387-389
bridges, water-proofing of, 451
cracks in, 455
depositing under water, 382
encasement, 442
fluidity of mixture, 391
forms, steel versus
timber for, 170
girder bridges, erection of, 406
jigging of freshly-made, 392, 393
leaching of by percolation
of water, 454
light aggregate for, 198
manufacture, economic problems
in, 387
military bridges, 476
mixing, economics of, 386-395
manner and time of, 391
one-man stones in, 386
pavements, 188
payment for, 386
pier-shafts, reinforcing of, 167
plain versus reinforced,
for pedestal bases, 173
protection of, 394
stone masonry for piers,
comparison, 167
stones, large, use of, 392
timber decks for highway
bridges, comparison, 187
working stresses for, 219
Condemnation of old bridges,
ruling for, 407
Conditions affecting layouts of
bridges, 116
Congestion of traffic at entrance
and exit, 54
Connections, entering, 216
Conscientious contractors, 342
Conscientious workmen, 342
Construction, Engineer of, 383
Construction facilities, 123
Continuity of trusses, summary of
conclusions from investigation, 81
Continuous trusses
divided-triangular trusses, 78, 80
economics affected by semi-
cantilevering, 81
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effect of reversing stresses on, 77
highway bridges, 78
Continuous trusses,
legitimate use of, 75
non-continuous trusses,
comparison, 75, 82
Petit trusses for, 78, 81
Continuous versus simple reinforced-
concrete girders, 221, 222
Contract-letting, economics in, 337-357
ideal system of, 343, 344
advantages of, 352-354
objections raised to, 354-356
importance of, 337
unit prices, 340
various methods of, 339
Contractor,
economic subjects for study, 383
salary on cost-plus jobs
objectionable, 348, 349
Contracts, expediting finishing of, 173
Conveyance of power, 312
Copying surveys from field books, 381
Corners, round, in plate-girders, 207
Corrective ratio, 346, 347
Corrosion, 415
prevention of, 421
Corthell, Dr. Elmer L., 12
Cost,
bridges and tunnels, 57, 58
estimates for bridges, economics
in, 141
estimating, examples of, 142-145
first, 16
movable spans, 297
operation, 55
problems for solution by
students, 146-149
records, 360
shopwork on pins and holes, 73
total annual, contrasting of, 14
Cost-plus method, objections to, 343
author's experience with, 343
eliminates competition, 342
Cotton drilling for water-proofing
decks, 183
Council Bluffs Bridge, 21
Counterforted versus cantilevered
walls, 231
Counters, over-stress of, 423
Counterweights, materials for, 294
Covell, V. R., 407, 424
Covering power of paint, 436
Cover-plates for top flanges, 200
Cracks in concrete, 455
Cranes, 366, 376, 381
Creosoting, 188
Crescent trusses, 272
Cribs and caissons, building
up of, 382
Cribs for foundations, 173
military bridging, 469
Criterion,
clearance for bascules and
vertical lifts, 309
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