Page 35 - Bridge and Highway Structure Rehabilitation and Repair

10 SECTION 1 ADMINISTRATIVE ISSUES

Table 1.2 Shows the overlap of bridge types for a variety of span lengths.
Approximate
S. No. Range of Span Length (feet) Bridge Type Selection
CONCRETE
1 20–50 RC/PS slab
2 50–140 PS box
3 30–150 PS I/bulb girder
4 140–200 PT box girder
5 130–750 PT segmental box
6 6–36 Precast concrete culvert
STEEL
7 40–110 Composite beams
8 60–300 Steel plate girder
9 100–600 Steel box girder
10 500–1700 Steel arches
11 500–1800 Steel truss
FLEXIBLE CABLE
12 500–1500 Cable stayed box
13 600–2000 Steel cable stayed
14 1000–6500 Steel suspension

For practical considerations, the selection of bridge types may be classified broadly as:
1. Small span (20 to 40 feet): Economical examples are reinforced concrete slab and T-beam
bridges, precast prestressed cellular deck bridges, timber bridges, prestressed concrete ad-
jacent and spread box beam bridges. Bridges with steel stringers have relatively higher life
cycle costs for small spans when compared to timber or modern precast concrete bridges.
2. Medium span (over 40 to 120 feet): Economical examples are prestressed concrete adjacent
and spread box beams and steel girder bridges.
3. Long span (over 120 to 240 feet): Economical examples are steel girder bridges (50W or
hybrid 70W and 50W grades), steel deck and through trusses, and prestressed concrete
arches.
4. Very long span (over 240 feet): Economical examples are steel arches, prestressed concrete
segmental boxes, cable stayed, and suspension cable bridges.

1.3.4 Deck Geometry, Components, and Materials

1. Geometric shape of deck: Common deck shapes are rectangular, skew, or curved. There are
separate AASHTO bridge design specifi cations for curved girder bridges. Super elevation
and sight distance requirements would reduce accidents.
2. Deck joints, deck grooves, longitudinal and cross slopes, drainage inlets.
3. Deck material: Timber, concrete, and steel have been largely used for decks. Concrete is

widely used for all types of traffic. FRP (fiber reinforced polymer) decks are now being
used. Exodermic (grillage) and orthotropic decks are also being used.
4. Prefabricated decks and composite steel-concrete I-beams are popular for small and me-
dium spans. Examples of proprietary products are CONSPAN and former INVERSET
techniques.
5. Deck width is based on traffic volume and number of lanes. It should match with approach

roadway width and acceleration and deceleration lane widths.