Introduction to Bridges a complete guideline.pdf

This is a slide on bridge design

1. A bridge is a structure that permits us to cross over an obstacle.
Suppose we lay a plank across a brook. If we have a bridge. If the plank is thin in
relation to
its length , it will sag. In fact, if it is too long, it will collapse. This shows that we
must consider the
weight of a bridge itself---the “dead load”.
If we stand at the middle of the plank, it sags even more. So, we
must provide for the weight of whatever our bridge is designed to
carry--- the “live load”.
Also, when you walk across the plank, it bounces under you,
illustrating the effect of a “moving live load”.
Finally, there is a “wind load”. A strong wind pushes against the
sides, lifts the deck, shakes the whole structure. Certainly the force of
the wind is something to keep in mind.
Bridges help us to connect to each other and the world.
There are four main types of physical bridges. They are arch, beam,
suspension and cable-stayed.

2. 
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Functions : aqueduct, viaduct, highway, pedestrian etc.
Materials of construction : reinforced concrete, pre-
stressed concrete, steel, composite, timber etc.
Form of superstructure : slab, beam, truss, arch,
suspension, cable-stayed etc.
Inter-span relation : simple, continuous, cantilever.

Span : short, medium, long, skew, curved.
Type of service and duration of use : permanent,
temporary bridge, military

3. The two basic parts are:
Substructure - includes the piers, the abutments and the
foundations.
Superstructure - consists of the deck structure itself, which
support the direct loads due to traffic and all the other
permanent and variable leads to which the structure is
subjected.
The connection between the substructure and the
superstructure is usually made through bearings. However,
rigid connections between the piers (and sometimes the
abutments) may be adopted, particularly in frame bridges
with tall (flexible) piers.

4. Bridge is a structure which provides a passage over
a gap without closing the opening which is beneath that gap. The passage
may be due to railway , roadway , canal & natural river etc. Initially the
naturally available materials such as stone and timber were extensively
used for bridges but now days artificial materials such as cement concrete
& steel are utilized more in the construction of bridge.

5. 700 A.D. Asia700 A.D. Asia
1,304 years 1,304 years
agoago
100 B.C. Romans100 B.C. Romans
2,104 years ago2,104 years ago
Clapper Bridge
Tree trunk
Stone
Arch design
evenly distributes
stresses
Natural concrete
made from mud
and straw
Roman Arch Bridge
Great Stone Bridge in China
Low bridge
Shallow arch
Allows boats
and water to pass
through

6. Truss Bridges
Mechanics of
Design
Wood
Suspension Bridges
Use of steel in
suspending cables
1900 1900
1920 1920
Prestressed
Concrete
Steel
2000 2000

7. MASONARY ARCH BRIDGE
Probably first category of bridge to be involved.
Aesthetically superior to slab bridges.
Consist of a arch shape slab supported on two apposite wall & it
was adopted earlier for small of 3 to 15m in masonry & extended
up to 519m in steel & 305m in concrete has been built in the world.

8. Beam Bridge
When something pushes down on the beam, the beam bends.
Its top edge is pushed together, and its bottom edge is pulled
apart.
Beam bridges are horizontal beams supported at each end by
substructure units and can be either simply supported when the
beams only connect across a single span, or continuous when
the beams are connected across two or more spans.

10. PIPE CULVERT
Consist of a pipe barrel under the embankment with protection
works at the entry and exit.
It is suitable for cross drainage flow on relatively flat terrain & in
this discharge is limited & it has negligible maintenance

11. Hydraulically short conduit which
conveys stream flow through a roadway
embankment or past some other type of
flow obstruction

12. SLAB BRIDGE
Simplest type of construction.
Adopted for small bridges and culverts.
Span is between 10-20m.
Concrete slab cast monolithically over longitudinal girder.
No. of longitudinal girders depends upon the width of road

13. PLATE GIRDER BRIDGE
Span ranges 10 to 60m.
Can be extending up to 250m in
continuous construction

14. TRUSS BRIDGE
Span 30 to 375m in simply supported
case.
Span 30 to 550m in cantilever
combination case

15. SUSPENSSION BRIDGE
Made up of high tensile steel cables strung in form of a
centenary to which the deck is attached by steel
suspenders which are made up of steel
rods/members/cables.
Deck can be of timber , concrete or steel spanning
across the stiffening girders transmitting loads to
suspenders.

16. The arch has great natural strength. Thousands of years
ago, Romans built arches out of stone. Today, most arch
bridges are made of steel or concrete, and they can
span up to 800 feet.

17. A movable bridge, is a bridge that moves to
allow passage usually for boats or barges.

19. Based upon structural action or nature of
superstructure action
Simply supported span bridge
Continuous span bridge
Cantilever bridge
Arch bridge
Rigid frame bridge

20. Based upon movement of structural parts of
the bridge
Fixed(permanent) bridge
Movable bridge: Can opened either
horizontally or vertically so as allow the
river or channel traffic to pass

21. Based upon purpose of bridge
Road bridge
Railway bridge
Pedestrian bridge

22. Base upon span length
Culvert – up to span length 6m
Minor bridge – up to span length 6 to
30m.
Major bridge – up to span length over
30m

29. • The most common and basic type
• Typical spans : 10m to 200m