1. In-situ reinforced concrete deck(most common type) 2. Pre-cast concrete deck(minimize the use of local labor) 3. Steel grid deck 4. Orthotropic steel deck 5. Timber deck
the major advantages is its relatively low costease of construction and extensive industry use
Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place
By producing precast concrete in a controlled environment the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees.The production process for Precast Concrete is performed on ground level, which helps with safety throughout a project. . There is a greater control of the quality of materials and workmanship in a precast plant rather than on a construction site. Financially, the forms used in a precast plant may be reused hundreds to thousands of times before they have to be replaced, which allows cost of formwork per unit to be lower than for site-cast production
This allows the deck both to directly bear vehicular loads and to contribute to the bridge structure's overall load-bearing behavior. The same is also true of the concrete slab in a composite girder bridge, but the steel orthotropic deck is considerably lighter, and therefore allows longer span bridges to be more efficiently designed.The Akashi-Kaikyō Bridge's orthotropic deck allowed the Japanese to build the longest span at about 6000 ft or 50% longer than the Golden Gate Bridge
Cooling and heating of decks causes deckcontraction and expansion, respectively• When contraction is restrained, cracking can occurwhen the tensile stress exceeds the tensile strength• When expansion is restrained, distortion or crushingcan occur• Joints are often specified to accommodate deckmovements without compromising the structuralintegrity of the bridge
A bridge is a structure providing
passage over an obstacle without
closing the way beneath.
bridge is a structure for carrying
the road traffic or other moving
loads over a depression or
obstruction such as channel, road
Classification of Bridges
According to functions :
aqueduct, viaduct, highway, pedestrian etc.
According to materials of construction : reinforced
concrete, prestressed concrete, steel, composite, timber etc.
According to form of superstructure :
slab, beam, truss, arch, suspension, cable-stayed etc.
According to interspan relation :
simple, continuous, cantilever.
According to the position of the bridge floor relative to the
superstructure : deck, through, half-through etc.
According to method of construction : pin-
connected, riveted, welded etc.
Classification of Bridges
According to road level relative to highest flood
level : high-level, submersible etc.
According to method of clearance for navigation :
movable-bascule, movable-swing, transporter
According to span : short, medium, long, right,
According to degree of redundancy : determinate,
According to type of service and duration of use :
permanent, temporary bridge, military
According to the flexibility of
FIXED SPAN BRIDGES .
MOVABLE SPAN BRIDGES.
• The most common and basic type
• Typical spans : 10m to 200m
• Truss is a simple skeletal structure.
• Typical span lengths are 40m to 500m.
Forces in a Truss Bridge
In design theory, the individual members of a simple truss are
only subject to tension and compression and not bending
forces. For most part, all the beams in a truss bridge are
Arches used a curved structure
which provides a high resistance
to bending forces.
Both ends are fixed in the
horizontal direction (no
horizontal movement allowed in
Arches can only be used where
ground is solid and stable.
Hingeless arch is very stiff and
suffers less deflection.
Two-hinged arch uses hinged
bearings which allow rotation
and most commonly used for
steel arches and very economical
Two hinged Arch
The three-hinged arch adds
an additional hinge at the
top and suffers very little
movement in either
foundation, but experiences
more deflection. Rarely
The tied arch allows
construction even if the
ground is not solid enough
to deal with horizontal
Forces in an Arch
Arches are well suited
to the use of stone
because they are
Many ancient and
of stone arches still
stand to this today.
A typical cable-stayed bridge is a continuous deck with
one or more towers erected above piers in the middle of
Cables stretch down diagonally from the towers and
support the deck. Typical spans 110m to 480m.
Cable Stay Towers
Cable stayed bridges may be classified by the
number of spans, number and type of towers, deck
type, number and arrangement of cables.
A typical suspension bridge is a continuous deck with one or
more towers erected above piers in the middle of span. The deck
maybe of truss or box girder.
Cables pass over the saddle which allows free sliding.
At both ends large anchors are placed to hold the ends of the
Unpleasant ride quality
Possible safety issues
Allows debris and salt laden water through
TYPICALLY ONLY USED
REPLACEMENT IN KIND.
Full-depth grid was introduced by engineers in the 1930
s to speed up construction on large bridge projects
Can be precast or cast-in-place for very quick
installation; high performance to cost ratio
High durability and longevity are demonstrated by the
great service history
FullyFILLED GRID SYSTEMS
Partially filled grid – first used in the 1950 s to further
reduce weight by eliminating concrete in bottom tension
Can be precast or cast-in-place offering rapid
good strength to weight ratio
Proven performance, this LW system offers similar span
capabilities to Full-Depth
Half filled grid decks
• Cooling and heating of decks causes deck
contraction and expansion, respectively
• When contraction is restrained, cracking can occur
when the tensile stress exceeds the tensile strength
• When expansion is restrained, distortion or crushing
• Joints are often specified to accommodate deck
movements without compromising the structural
integrity of the bridge
• Bridge deck joints should protect the interior edges
of concrete decks from vehicle loads, seal the joint
openings, and accommodate movements resulting
from temperature changes and creep and
shrinkage of concrete
• Joint failure is a internationwide problem in the
• Failure is not necessarily caused by the joint
material itself but also by careless design, improper
installation, and inadequate maintenance
Accommodate less than 1- in. movements or minor
Are sometimes installed with armor angles to protect
Are effective only under the assumption that the
passage of water and debris through the opening will
not have adverse effects on the supporting