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Adequate drainage of the deck is important for safe operation during rainstorms, to prevent accumulation of rainwater or snowmelt that could freeze and cause skidding, and to prolong the life of the deck by removing standing water, which would otherwise contribute the water element necessary for corrosion. Transverse drainage of the deck should be provided […]

Repainting of bridges over highways or railroads may necessitate use of protective covers, or require traffic lanes to be diverted or work interrupted during passage of trains, while existing paint is removed and new paint applied. These factors all favor use of a bridge material or protection system that does not require maintenance reapplication of […]

Shoulders were not always provided on bridges in the past. This in itself can be a reason for widening an existing bridge. More frequently, widening is necessitated by the addition of lanes to the highway, at which time a full shoulder can be provided. The design and preparation of plans for bridge widening usually require […]

Where the spans are not controlled by features crossed—such as roads, railroads, streams, or existing buildings—and there is freedom to locate piers, the lengths of spans will be controlled by aesthetic, economic, and structural requirements. Generally, from an aesthetic standpoint, spans should have a length at least 3 or 4 times the pier height. The […]

The steel box girder bridge is depicted in Fig. 4.10. The steel elements are fabricated and erected as “tubs,” and the composite concrete deck is placed in the field. This con­figuration has some advantages over plate girder construction. Visually, it is “cleaner,” and it does not provide surfaces for birds to perch. For high-visibility bridges, […]

In regard to efficiency in the number of lines of girders in bridges consisting of multiple girders connected by cross frames, cursory cost comparisons almost always conclude that the widest spacing of girders is the most economical. Savings result not only from the reduced number of main members but also from the reduced number of […]

The concrete deck for steel beam and girder bridges may be designed and constructed on the basis of either composite or noncomposite behavior. With composite construction, the effective area of the slab can be calculated and used in determining the moment resistance of the section in positive moment regions. In negative moment regions, ten­sile stresses […]

The welded steel plate girder bridge (Fig. 4.9) extends the span range of deck-type bridges (bridges having all the structural support below the deck slab) well beyond the range of rolled steel beams or precast prestressed-concrete beams. 37-0" Whereas haunched girders were economical in the past for long spans, the current practice, strongly advocated by […]

The steel-beam bridge uses rolled steel beams as shown in Fig. 4.8. Beam depths of 44, 40, and 36 in (1118, 1016, and 914 mm) are available, as well as shallower sections. Check with producers on current availability of the deeper sections from domestic sources because federal law applicable to federally aided projects, as well […]

Prestressed-concrete beams of the basic I-shape, but with variations, can be used over approximately the same range of spans as steel beams. The deepest AASHTO standard prestressed beams (72 in or 1828 mm) have a somewhat greater simple-span capacity than 36-in-deep (914-mm) rolled steel beams, although deeper rolled beams are avail­able. This type of bridge […]