Page 23 - Bridge and Highway Structure Rehabilitation and Repair

xxii SYMBOLS, NOTATIONS, AND TERMINOLOGY

Bridge Terminology
Abutment—Abutment has dual purpose, earth retaining and supporting all or part of the bridge. The two abut-
ments defi ne the beginning and end of bridge and serve as anchors.
Approach—Approach or approach slab interfaces with the abutment to provide continuity to the roadway. The road-
way is capped by a slab resting on unyielding soil to prevent differential settlement after a heavy downpour.
Backwall—Backwall or the stem separates the approach slab from the bridge. They interface with wingwalls.
Barrier—Barrier is a railing or reinforced concrete parapet which serves as a protective dwarf wall placed over
the deck to guide vehicles and prevent collisions.
Beam—Beam or girder is a very important primary member which supports the deck. It spans over the river width
or the interchange. It is supported by pier and abutments and is held in position by bearings resting over
substructure. It is made of timber, aluminum, steel, reinforced or prestressed concrete.
Bearing—Bearing is a mechanical device which permits expansion, contraction and rotation of beams. They also
transfer heavy reactions over the superstructure over a wider area.
Bracing—Bracing is a secondary member placed in between beams to resist wind load in horizontal direction.
Deck—Deck is the most important part of superstructure. It supports the moving loads and can be built in reinforced
concrete, timber or open grid steel. It is usually made composite with the supporting beams.
Deck joint—A joint in transverse or longitudinal direction helps to release thermal stress in the deck slab. They
are placed before the abutment backwall. Deck Joint consists of steel angles with vertical leg anchored into
the deck concrete to shield the corners of concrete edges from any damage resulting from the impact of
wheels.
Diaphragm—Diaphragm is a secondary member which interconnects the beam in transverse direction and enables
lateral distribution of vertical and horizontal loads. They are usually spaced at twenty feet or less.
Embankment—Embankment is body of earth which transitions from deck elevation to the lower ground and is
given a gentle slope using fi ll material for that purpose.
Footing—Footing serves as the fi xed feet of bridge. It is the most important part of the bridge family. Shallow
footings transfer the loads from the bridge over the wider area of compacted sub-soil. Deep footings are
bearing or frictional piles or caissons driven to the required depth deep into soils.
Haunch—Haunch is a concrete transition member placed over the fl ange of beam and under the deck slab. Like
a pedestal, its height is adjusted to achieve the required deck elevation. Haunches over 4 inch depth require
reinforcement.
Integral abutment—Abutment wall resting on piles in which top stub is made integral with the deck slab and the
approach slab. Bearings or deck joints are not required. Special boundaries of beam serve as a longitudinal
frame. Structural performance of bridge under seismic conditions is also improved.
Maintenance—Routine or regular activities, which are intended to preserve and maintain a structure’s original
serviceability and functionality.
Parapet—Parapet is a barrier placed at the edges of deck slab. It also supports lighting poles or sign panels.
Pedestal—Pedestal supports the bearings as very short concrete columns. They maintain the required bridge
seat elevations and their adjustable heights in concrete are varied to suit.
Pier—Pier is a wide column which supports the intermediate parts of the longer span bridge and shares the loads
with abutments. They may be placed in the middle of a river.
Pile—Pile serves as a stiff nail driven into a hard soil media. Acting in a group, it provides stability to the bridge.
Rehabilitation—Comprehensive repair of a bridge structure’s most deteriorated elements that are intended to
restore and signifi cantly extend its original serviceability and functionality.
Repair—Activities, usually isolated to a portion of one element of a structure, that are necessary to restore
serviceability or functionality due to distress from things such as vehicle impact damage, observed scour or
severe localized deterioration.