Bridges

Bridges
BRIDGE
The connecting structure, creates bonding between different disconnected
parts of a country, two banks of the ocean or parts of two countries. A Bridge
is a structural marvel which is generally used to pass any type of obstruction
that can slow the life of people. From the very beginning, engineers were
trying to win over nature and consequently, they have invented bridge
structure which can use to overcome the mentioned natural obstacles.
Main Parts of a Bridge
There are different types of bridge. Different bridge types contain
different parts. Followings are the main parts of a bridge:
• Deck
• Abutment
• Pile
• Pier
• Girder
• Rail Track
To give a preliminary idea of these bridge parts a brief description of each part is
given below.
Deck
• A deck is a fundamental part of any bridge to pass vehicle, goods, people etc.
from one side to another.
Abutment
• The support provided at the two ends of a bridge is known as an abutment.
Pile
• For the bridge with pier, the pile is a fundamental component. Pile type
foundation is generally needed when the upper soil layer is loose. Pile depth
depends on the soil layer. To find the hard soil layer which will make the
structure stable, the pile is usually extended to some depth into the hard soil
layer.
Pier
• Pier is the compression member which stay above the pile and make the
structure stable. Pier generally provides for span at intermediate points.
• Piers perform two main functions:
• Transferring superstructure vertical loads to the foundation.
• Resisting to the horizontal forces acting on the bridges.
• For bridge pier to pier, distance is the span. Water pressure is the extra
pressure which acts onto the pier laterally.

Girder (Box or I-joist)
Just like the beam, girder is used in the bridge. It can be two types I-joist
and Box. This name has been given because of their shape. I-joist girder
type is commonly used in bridges. Box girder can be precast or cast in place
and it is generally existing in prestressed condition.
• Rail Track
• Normally Road traffic is the main vehicle onto the bridge but if the train
needs to be passed through that bridge rail track is the extra component.
Types of Bridges
• Followings are the main types of bridges.

• Truss Bridge
• Arch Bridges
• Suspension Bridges
• Cable-Stayed Bridges
• Slab Bridges
• Box Girder Bridges
Truss Bridges
Bridges with truss are made by steel two force member with only
tension and compression. No bending moment is allowed in this
structure. Most stable structural shape for truss is triangular.
Arch Bridges
• Arch bridge mainly exists in compression. Utilizes an

aerodynamic system with torsional rigidity.
Suspension Bridges
• In suspension bridges, long spans can be provided which is essential in
many situations. It gives freedom to the engineer to provide a long span
with the help of a cable. Followings are the Basic components of a
suspension bridge Structural system:
• Stiffening Girder/ Trusses: Longitudinal structures support and distribute
moving vehicle loads. Secure aerodynamic stability of the structure.
• Main Cables: Main cables are connected to girders through hanger rope.
These hanger ropes transfer the loads from girder to the main cables. The
main function of these main cables to carry these loads to the main
towers.
• Main Towers: Main cables are supported by these intermediate vertical
structures and transfer the total load of the bridge to the foundation.
Advantages of Suspension Bridges
• Economic Advantage: The realm spanned by a bridge is extremely long
in proportion to the number of materials needed to construct bridges.
• Height Advantage: Built over waterways, suspension bridges are

engineered high, permitting the passage of tall ships unrestrained by the
bridge.
• Construction Advantage: Throughout construction, temporary central

supports do not have to be compelled to be engineered, and access to the
development is not needed from below. This implies busy roadways and
waterways do not have to be compelled to be discontinuous.
Disadvantages of Suspension Bridges
• Heavy Loads: Flexibility also becomes an obstacle once significant, focused
loads are concerned. Suspension bridges do not seem to be usually used for
regional rail crossings that carry most weight loads that add dangerous stress to
the structure.
• Loss of Income: Despite the low prices of constructing suspension bridges and
therefore the job opportunities they provide, the length of your time required to
complete building these bridges are long. Taking a longer time may be the result
of the loss of income that may be full of the economy site.

Disadvantages of Suspension Bridges
• Foundation pitfalls: Once inbuilt soft ground, suspension bridges need in-
depth and high-ticket foundation work to combat the results of the significant
load on foundation towers.
• Load Limitations: Another pitfall of a suspension bridge is that the material
used is the cables. These cables have limitations once it involves bearing the
burden of masses. Though it will enable a minimum weight with relevant
vehicles passing through, an excessive amount of weight will cause the
breaking of cables.
• Restricted Applications: Suspension bridges, despite their cost-effectiveness
in construction and adaptability once it involves site location, have limitations
once it involves its use. This can be as a result of they will be destroyed by
sturdy winds and not sturdy enough to carry limitless weight, careful thought
ought to be taken before construction.
Suspension bridges have preserved quality around the world.
Along with benefits and pitfalls, engineers building these bridges
ought to study the look and ensure necessities in building these
bridges.
Suspension Bridges
Cable-Stayed Bridges
• It has a lot of similarities to the suspension bridge. But there are
few differences between a suspension bridge and cable-stayed
bridge. In this case, bridge mainly carries the vertical loads
acting on the girder. The purpose of the stay cables is to
provide intermediate support for the girder and it helps to span
a long distance.
Cable-Stayed Bridges
Box Girder Bridges
It's a box type girder different from normal I girder and it can easily resist
more amount of torsion. This type of bridge contains top deck, vertical
web, bottom slab. Box girder bridge can be subdivided into three basic
categories:
1.Single cell box.
2.Multicell box.
3.Box with struts supporting a cantilever deck.
Box Girder Bridges
Beam bridges
• It is the most common type of bridge. Use in every place where the span is not
so long.
Beam bridges
Advantages of Beam Bridges
There are situations when the beam bridge has more advantages than other types
of bridges. Followings are the major advantages of beam bridges:
i. A beam rests simply on the supports.
ii. The effects of thermal expansion and movements of the ground are easily
sustained.
iii. A beam could also be engineered removed from the ultimate position and
raised fleetly into place with the least disruption of traffic or navigation.
iv. Beam bridges are easy to construct.
v. In comparison to other bridge types, beam bridges are less costly.
vi. Mostly used widely in urban and rural zones
Beam bridges
Disadvantages of Beam Bridges
•Beam Bridge contains forces, which are much larger than the load, and it needs to
be relatively massive.
•Beam Bridges have a limited span and do not allow large boats or vehicles to pass
underneath.
•Mostly heavy boat traffic or large ships cannot pass underneath.
•People may not find the design of beam bridges spectacular.
Difference between Bridge and Culvert
The purpose of both bridges and culvert is providing a transportation route over
obstructions, which is why they may seem the same, but the span length chiefly
differentiates between the two structures. Other factors also set culverts and
bridges apart from each other, like terrain and design.
Some other differences between bridges and culverts are given below:
Bridge Culvert
1 A bridge is a passage of transportation A culvert is generally a tunnel-like
(for people or vehicles) over a large structure that allows water to pass under
body of water or physical obstruction. a roadway or railway.
2 The basic components of a bridge are The components of a culvert are
superstructure (supports load), substructure comparatively simpler and include
(transfers load to foundation soil) and deck concrete boxes or cells (single or
(transfers surface load to other multiple), pipes, a top deck or slab and
components). supporting parts.
3 Bridges are constructed at a height more Culverts are built at less than 20 feet high over the
than 20 feet. obstruction.
4 A bridge spans from 6 meters (minor The length of culverts is typically not more than 6 meters.
bridges) to more than 120 meters.
5 Piers and abutments are the supporting Culverts are usually embedded in the soil which bears
structures of a bridge. the major portion of the culvert load.
6 A bridge contains no floor. A culvert is an enveloping structure that consists of two

sides, a roof, and a floor.
7 The construction of a strong and deep No deep foundation is required for a culvert.
foundation is very important in building a
bridge. The foundation along the entire
breadth supports the bridge.
8 A bridge is usually a linear and straight Culverts are totally enclosed structures that can be semi-
passage. circular, rectangular, elliptical or pear-shaped.
9 The structure and design of a bridge are The construction of a culvert can be done
elaborate and complex, hence its with a low budget.
construction requires a substantial
budget.
10 Bridges are usually constructed at the Culverts can be pre-constructed or built at the
site or pre-constructed in smaller parts. site (in situ culverts).
11 Construction of bridges generally Culverts are simpler in structure and design,

requires a lot of time and manpower. so it can be constructed with less time and
labor.
12 Bridges provide an easier route of Culverts prevent water logging, flood, and
transportation that saves time and erosion, and allows water to flow its natural
reduces distance. course under a roadway or railway.
13 A bridge is built over a body of A culvert is constructed when water needs to be
water that is large and has conveyed through tunnels or channels under a
variable flow. roadway.
14 Bridges can withstand heavy Some culverts, like box culverts, have sharp corners
and speeding vehicles. that are unsuitable for high-velocity vehicles.
15 The only way of transportation A culvert can be constructed to accommodate

is over the deck of the bridge. roadways both over and under the deck (e.g. a culvert
built over another road or railway).

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Bridges

structure stable. Pier generally provides for span at intermediate points.

• Piers perform two main functions:

• Transferring superstructure vertical loads to the foundation.

• Resisting to the horizontal forces acting on the bridges.

pressure which acts onto the pier laterally.

• Followings are the main types of bridges.

• Arch bridge mainly exists in compression. Utilizes an

• Height Advantage: Built over waterways, suspension bridges are

• Construction Advantage: Throughout construction, temporary central

of the loss of income that may be full of the economy site.

6 A bridge contains no floor. A culvert is an enveloping structure that consists of two

11 Construction of bridges generally Culverts are simpler in structure and design,

15 The only way of transportation A culvert can be constructed to accommodate

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