Bridge Engineering: by Dr. Ramesh P S Professor

Bridge Engineering
By
Dr. Ramesh P S
Professor
Introduction
• The basic purpose of a bridge is to carry traffic
over an opening or discontinuity in the
landscape.
• Various types of bridge traffic can include
pedestrians, vehicles, pipelines, cables, water,
and trains, or a combination thereof.
• An opening can occur over a highway, a river,
a valley, or any other type of physical obstacle
Introduction
Seto Great Bridge

Japan
• A bridge should be “safe, functional, economical, and
good looking.” Safety cannot be compromised. A bridge
must be safe under all of the loads it is designed for.
• Functionality should not be compromised
• Cost varies from place to place, time to time, and
situation to situation
• Because both economy and aesthetics are relative,
there is no “perfect” design, but only a “suitable”
design for a bridge
IMPORTANCE OF BRIDGES
▪Connects Difficult Terrains
▪Easy Trade and Transportation of Goods
▪Reduces Travelling Time
▪Military use
▪Political and Economic importance
▪Less Emission due to displacement
COMPONENTS OF A BRIDGE
CLASSIFICATION OF BRIDGES
According to the According to According to According to the

flexibility of the position of the inter- span form or type of
superstructure bridge floor relations superstructure
According to Flexibility
• Fixed-span bridges
• Movable bridges
According to the position of Bridge Floor
The bridges are classified as
deck bridges or semi bridges
according to the position of
bridge floor.
Deck Slab
Through Slab
According to Inter- Span Relations
Simple
Continuous
Cantilever Bridges
According to the form or type of
superstructure
• Slab bridge
• Beam bridge
• Truss bridge
• Arch bridge
• Cable stayed (or )suspension bridge
Thoraikkam, Chennai
Tulsa Bridge
Highway
Beam Bridges
Railway Bridge
Simple truss Bridge

Single Arch Bridge
Continuous Arch
Bridge
Golden Gate
Bridge, San
Francisco, USA
Clifton Suspension
Bridge
Bridge Classification Based on Span
• Types of Bridges based on Span
– Culvert bridge
– Minor bridge
– Major bridge
– Long span bridge
Culvert Bridge : When
the bridge span length is
below 6meters then it is
called as Culvert Bridge.
• Minor Bridges - When
the bridge span length
is below 6meters then
it is called as
Culvert Bridge.
• Major
Bridges-
60m to
120m
Span
Assam-Meghalaya Bridge
• Long span
Bridges >
120m span
According to function
• Aqueduct bridge(canal over a river)
• Viaduct(road or railway over a valley or river)
• Pedestrian bridge
• Highway bridge
• Railway bridge
• Road-cum-rail or pipe line bridge
According to material of construction
of superstructure
• Timber bridge
• Concrete bridge
• Stone bridge
• R.C.C bridge
• Steel bridge
• P.C.C bridge
• Composite bridge
• Aluminium bridge
According to Degree of Redundancy
• Statically determinate bridge
• Statically indeterminate bridge

According to anticipated type of
service and duration of use
• Temporary bridge : is a lay term for any floating,
modular structure. They’re generally used during
periods of construction, when regularly-
available pedestrian or vehicular bridges have
become inaccessible. They can also be used for
events, and come in particularly handy when
goods need to be transported
• Permanent bridge : are constructed for a long
time period for use. Permanent bridges are
maintained at a high level.
According to Clearance for Navigation
• High level
bridge
• Movable -
bascule bridge
• Movable -swing
or transporter
bridge
Four Stages of a Bridge Design
• The design process of a bridge can be divided
into four basic stages:
• Conceptual,
• Preliminary,
• Detailed and
• Construction design.
AESTHETICS OF BRIDGES
External appearance
Internal view
Sequential View
GUIDELINES:
1) Beauty and Stability

2) Bridge and Environment
Integration
3) Material Choice
4) Moderate Lightings
Figure 4: Aesthetics of a bridge 8

STEEL BRIDGE
• Steel is largely used in construction of bridge for short as
well as long spans.
• Steel has been recognized as economic option for a
range of bridges; for long span bridges, railway bridges,
footbridges, and medium span highway bridges.
• The world’s first cast iron bridge was built at Telford, in
1779, by Abraham Darby .
• Steel bridges now have a proven life span extending to
well over 100 years.
9
Classification of steel bridges
Steel bridges are classified according to:
the type of traffic carried
the type of main structural system
the position of the carriage way relative to the main
structural system
Figure 5: Steel Bridge 1

REINFORCED CONCRETE BRIDGE
RCC bridges are the earliest form of bridges. They are easy
to construct.
Arches are preferable where Bending moment is more
and they are easy to design.
Site Selection for RCC Bridge

1) Straight reach of the stream
2) Good foundation
3) Well defined firm banks
4) Minimum width of crossing
5) Approaches
Figure 6: RCC Bridge 1

Its not always possible to provide straight deck, when
horizontal curves are to be provided the following design
speed is to be considered:
33
SUSPENSION BRIDGE
• A suspension bridge is a type of bridge in which the deck (the
load-bearing portion) is hung below suspension cables on
vertical suspenders.
• First Suspension bridge was built in 1433, in eastern Bhutan
by Thangtong Gyalpo.
• Suspension bridge is generally preferred when the span is
more than 200 m for roadway or 300 m for light traffic like
motors.
There are two types of suspension bridge:

Un-stiffened deck type suspension bridge
Stiffing girder type suspension bridge
34
Components of a suspension bridge
Figure 7: Components of a suspension Bridge
35
Comparison of RCC, Steel & Suspension bridges :
Suspension Bridge Steel Bridge RCC Bridge
Steel Cables, concrete or Steel frames and concrete Reinforced cement
steel deck used as deck. concrete
construction materials.
Better to withstand Steel can fully meet the Arches are preferred
earthquake movements structural requirement where more bending
than heavier and more with even small sections. moments occur.
rigid bridges.
Maintenance cost is high Maintenance against the Their cost of maintenance

as the cables needs to be rusting of steel has to be is very small.
changed done regularly which
increases the cost of
maintenance
Installation takes time. Quick Installation. Takes longest time for
installation.
1 January 2014 36
BRIDGE FAILURE
When a bridge collapses , many lives are put at risk.

Bridge collapse is one of the most dangerous types of
structural failure that can occur.
Causes of Bridge failure
1. Earthquake
2. Fire
3. Boat impact
4. Flood
5. Construction accidents
6. Manufacturing defects
1. Design defects Figure 8: Bridge Failure

2. Poor maintenance
37
MAINTENANCE OF BRIDGES
1. The bearings of girders should be coated with oil

from time to time.
2. The floor system of approaches and bridges should
be properly maintained.
3. The entire drainage system should be inspected
for its proper functioning.
4. The movement of foundations, if any, should be
carefully inspected and all attempts should be
made to stop such further movement.
38

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Bridge Engineering

Seto Great Bridge

According to the According to According to According to the

Simple truss Bridge

• Statically determinate bridge

• Statically indeterminate bridge

1) Beauty and Stability

Figure 4: Aesthetics of a bridge 8

Figure 5: Steel Bridge 1

Site Selection for RCC Bridge

Figure 6: RCC Bridge 1

There are two types of suspension bridge:

Figure 7: Components of a suspension Bridge

Maintenance cost is high Maintenance against the Their cost of maintenance

When a bridge collapses , many lives are put at risk.

1. Design defects Figure 8: Bridge Failure

1. The bearings of girders should be coated with oil

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