Criterion,

economics of primary

truss members, 26

military bridge criterion

is victory, 462

Crooked stringers, 466

Cross girders, spacing of, 192

Cross-section of deck, 128

Crown-hinge, location of, 235

Crowning of roadway, 426

Crystallization of metal, 416

Curbs, 189

Current, swiftness of, 483

reversal, 122

Curving ends of girders, 211

Cut-stone masonry versus

concrete for piers, 167

Cutting metal, 374

Cylinder piers, 168

repairs to, 421

D

Damages, 382

failure to water-proof, 453

faulty inspection, 362

Danger from fire, 310

Data,

collection of, 359

concerning bridge approaches

in "Bridge Engineering," 114

Davies, J. Vipond, 8

Decisions by resident engineer, 381

Decks,

arrangement of, to accom-

modate several lines of

traffic, 128

ballasted, 182, 183, 185, 186

drainage of, 183

economics of, 182-198

highway bridges, 187

concrete versus timber

for, 187

military bridges, 474

open timber, 182, 184

open-web, riveted spans,

economies of, 70

plate-girder spans, economics

of, 68

timber, 195

weight reduced to minimum, 194

width of, 127

Defensibility of military bridges, 484

Definition of economics, 6

Delaware River bridge between

Philadelphia and Camden,

proposed, 318

Depositing concrete under water, 382

Depths,

descent into a tunnel, 54

economic, of trusses, 176

floor beams, economic, 185

foundations, 122

girders in viaducts, 203

pier shafts below water, 170

Depths,

plate-girders, economic, with

riveted end connections, 179, 180

stringers, economic, 185

water, 483

Derrick cars, 398

Descent into a tunnel, depth of, 54

Design,

details, 203

economics of, 199-201

shop considerations, 366

Destruction due to neglect of

water-proofing, 457

Detailing, economics of, 199-201

vertical lifts, economics in, 294

Details, designing of, 203

skimping of, 133, 201

Deterioration,

paint, causes of, 444

steel structures due to wear, 423

Determination,

economic span-lengths, 158

layouts, 116-124

time for repainting, 445

Detroit River proposed bridge,

estimating cost for, 111, 146

Detroit Superior Graphite paint,

438, 439

Development of true economy, 2

Diagrams, 18

Direct current versus alternating, 312

Discharging employees, 381

Disruptive force of freezing water, 455

Distance from springing to bottom

of base, 226

Diversion of traffic during

replacement, 405

Divided-triangular trusses for

continuous spans, 78, 80

Division of bonus among employees, 348

Dogs, 476

Double-leaf versus single-leaf bascule, 289

Double tracking, future, 21

Double-track railway trestles, 252

Doubling of trusses, future, 21

Doubling-up of old bridges, 407

Drainage,

deck, 183

roads, 454

Drawings,

changes, 359

unchecked, 359

Drawing temperature, best, 44

Driers, use of, 435

Drift bolts in military bridges, 477

Drift, protection against, 485

Drifting ice, 122

Drilling (cotton) for water-

proofing decks, 183

Drilling from solid, 208, 375

Drills, portable, 379

Drippings from brine, 415

Duluth proposed lift bridge, 310

"Dumb bell" pier-shafts, 168