beams. — True economic investigation for plate-girders. — Considerations tending to offset the advantage of employing economic web-depth. — Old rule of making weight of flanges equal to that of web and its stiffening is just about right. — Economic panel-lengths. — Comparative economics of Warren with Pratt and Petit trusses. — Economic limiting span-lengths for polygonal chords ............. 175

Possible types of deck for railway bridges. — Open-floor. — Trough floor. — Bal-

lasted decks. — Ballast resting directly on steel plate. — Ballast resting on reinforced-concrete slab. — Resting ties on bottom-flange angles or on special shelf-angles. — Depth and number of beams and stringers. — Encasing the said beams in concrete. — Floor systems. — Standard floor system. — Jack-stringers versus four lines of carrying stringers per track. — Economic panel length. — Cut-away ends of floor-beams. — Economic depths for stringers. — Economic depths for floor-beams. — Effect on economics of under-clearance requirements. — Floors for half-through, plate-girder spans. — Economic spacing of deck trusses for double-track bridges. — Electric-railway bridges. — Highway-bridge decks. — Timber deck versus concrete deck.b-Danger to timber deck from fire. — Deck for bascule bridges. — Pavings for roadways. — Plank floors. — Creosoted planks. — Concrete base. — Wooden block pavement. — Brick pavement. — Asphalt and bituminous pavements. — Concrete wearing surface. — Sidewalks. — Sub-paving or base. — Curbs. — Handrails. — Electric-railway tracks. — Floor systems. — Spacing of I-beams. — Omission of floor-system in deck spans. — Economic number of girders in deck, plate-girder spans. — Standard floor-system in deck, plate-girder spans. — Stringer spacing. — Sidewalk slabs. — Number of girders in half-through spans. — Stringerless floor versus floor with stringers. — Cantilever brackets. — Floor of minimum weight. — Stiffened-buckle-plate floor. — Haydite concrete. ......... 182

Simple details are economic. — Carry stresses by shortest route. — Reduction of

number of rivet holes in a section to a minimum. — Largest practicable radii of gyration for compression members. — H sections for posts. — Compression members carrying shear. — Non-use of cover plates in railway, deck, plate-girder spans. — Batten plates. — Turning flanges of post channels in. — Must consider all panels of compression chord simultaneously when designing any length thereof. — Use metal to best advantage in detailing. — False economy to skimp details. — Details and joints frequently defy exact analysis. — Consider possible rusting when detailing. — All parts to be easily accessible to paint brush. ....................... 199

Designs to be made so as to facilitate shopwork. — Sub-punching and reaming

versus punching full size. — Drilling solid. — Sheared edges. — End stiffeners