Bridge Engineering

1. Rewa Engineering College
Prepared By
Bicky Agarwal

2. Introduction
A bridge is a structure which provides
passage facilities over an obstacle without
closing the way underneath.
The required passage may be for a railway
The required passage may be for a railway
track, road or pedestrians etc.
The obstacles to be crossed may be deep
valley full of water, river etc.
2

3. Requirements of An Ideal Bridge
Economical
Safe and convenient
Proper design of bridge to
ensure strength & durability
Aesthetically pleasing
3

4. Terminology
 Foundation:
component which carry the total weight of
bridge and transfer to subgrade.
 Substructure:
components such as abutments , piers & wing
walls which are up to the level of bearings.
Substructure supports superstructure.
 Superstructure :
components such as beams , girder, arches,
cables flooring , guard rails etc. which are
above the level of bearings. 4

5. 5

6.  Span - the distance between two bridge supports
 Deck- bridge floor directly carrying traffic loads.
 Beam / Girder: Beam or girder is that part of
 Beam / Girder: Beam or girder is that part of
superstructure which is under bending along the span.
It is the load bearing part which supports the deck.
6

7. 7

8.  Abutment: The end support of the supper structure of a
bridge are called abutments. They transmit the load from the
super structure of the bridge to the foundation.
 Pier :It is an intermediate support of an multi span
bridge. Its height is kept usually equal to the abutment.
 Pier Cap :Pier Cap is the component which transfers
loads from the superstructure to the piers. Pier cap provide
sufficient seating for the Bridge girders.
8

9. 9

10.  Bearing : Bearing transfers loads from the
girders to the pier caps.
10

11. Factors
Factors Affecting
Affecting Choice Of
Choice Of Bridge
Bridge
Type
Type
• Volume & Nature Of Traffic :- Volume of traffic passing over
the bridge and its nature whether light, medium or heavy is
to studied depending upon which loadings are determined.
• Hydraulic Data :- Data such as flood discharge, Highest flood
level, velocity of flow, catchment area.
• Nature Of River & Soil :- Nature of river is studied. The soil
present in river bed is studied for its strength properties.
present in river bed is studied for its strength properties.
Depending upon these properties foundation condition are
determined.
• Physical Features :- Site conditions should also considered
while selecting type of bridge . Whether the channel is used
for navigation or not.
• Dimension Of Bridge :- The length and width of bridge
required also affect the selection of bridge type.
• Availability of funds for construction.
• Availability of labor and construction material near the site.
11

12. Types of Bridges
Types of Bridges
Types of Bridges
Types of Bridges
12

13. TYPES OF BRIDGE
Bridge are classified into so many types based on
different criteria’
 Types of bridge Based on Types of superstructure
 Types of bridge Based on materials
Types of bridge based on span
 Types of bridge based on span
 Types of bridge based on level crossing
 Types of bridge based on function
 Types of Bridges based on Utility

14. Types of Bridge based on Type of Super
Structure
 Arch bridge
 Girder bridge
 Truss bridge
Truss bridge
 Suspension bridge
 Cable Stayed Bridge
 Cantilever Bridge

15. Arch
Arch Bridge
Bridge
• Arch Bridge is curved shaped Bridge
• These are adopted for small span bridges
• The are aesthetically superior.

16. 16

17. Girder bridge
 In case of Girder Bridge, the deck slab is supported
by means of girders.
The girder may be of rolled steel girder or plate
girder or box girder.
Load coming from the deck are taken by girder and
transferred them to the piers and abutments.

18. Truss Bridge
Truss Bridge
 Truss is member consisting connected
elements to form triangular units.
 In case of truss bridge the super structure is
provided with trusses.
 Generally, trusses are made of steel.
18

19. 19

20. Suspension
Suspension Bridges
Bridges
• It consist of a hanging cable which is anchored at two ends.
• The flooring of bridge is supported by cable
• The vertical member are known as suspenders and are
provided to transfer load from bridge to suspension cable.

21. 21

22. Suspension Bridge
Suspension Bridge
22

23. Cable
Cable Stayed
Stayed Bridge.
Bridge.
 A cable stayed bridge consist of one or
more pillar/ tower in the middle.
 Cable stretch diagonally between these
pillars
pillars
23

24. 24

25. 25

26. 
 A cantilever bridge is a bridge built using
cantilevers, structures that project
horizontally into space, supported on only
one end.
one end.

27. Types of bridge based on material
 Timber Bridge
 Masonry bridge
 Steel bridge
 R.C.C bridge
 Pre stressed concrete bridge
 Pre stressed concrete bridge

28.  Timber Bridge
 Bridges constructed using timber are
called timber bridges.These are generally
constructed for short spans or as
temporary bridges.They are not useful
for heavy loads.

29. Masonry Bridge
Masonry Bridge
 Masonry Bridge constructed by using
bricks or stones.
29

30. Steel Bridge
Steel Bridge
 Steel bridges are constructed using steel
bars or trusses or steel cables.These are
more durable and bear heavy loads
30

31. R.C.C Bridge
R.C.C Bridge
 R.C.C bridges are constructed using reinforced
cement concrete.These are more stable and
durable.They can bear heavy loads and are
widely using nowadays
31

32. Prestressed
Prestressed Concrete Bridge
Concrete Bridge
 If concrete material is placed under
compression before applying the loads,
then it is called as prestressed concrete
32

33. Types of Bridges based on Span
Types of Bridges based on Span
 Culvert bridge
 Minor bridge
 Major bridge
 Long span bridge
 Long span bridge
33

34. Culverts
Culverts
• It is defined as small bridge constructed
over a stream which remains dry for most
part of year.
• It is a cross drainage work having a total
length not exceeding 6 m between the face of
abutment.
abutment.
• Types of Culvert :-
1. Arch Culverts
2. Box Culverts
3. Pipe Culverts

35. Arch
Arch Culvert
Culvert
• An arch culvert of stone masonry may be
adopted for span ranges of 2m to 6m.

36. Box
Box Culvert
Culvert
• They are rectangular boxes and are formed
of masonry RCC or steel.
• They may be consist of one or more
number of rectangular or square openings

37. Pipe
Pipe Culvert
Culvert
37

38. Minor Bridge
Minor Bridge
If the bridge span length is in between 8 to
30 meters, then it is called minor bridge.
38

39. Major Bridge
Major Bridge
For major bridge, the span is generally
about 30 to 120 meters
39

40. Long Span Bridge
Long Span Bridge
When the span of bridge is more than 120
meters then it is termed as long span
bridge
40

41. Types of Bridges based on Level
Types of Bridges based on Level
of Crossing
of Crossing
 Over bridge
 Under bridge
41

42. Over Bridge
Over Bridge
 To pass over another route (railway or
highway), a bridge is constructed to allow
traffic.This is called over bridge or fly
over bridge
over bridge
42

43. Under Bridge
Under Bridge
 If over bridge is not possible, an
underground type bridge is constructed
to pass another route.This is called under
bridge.
bridge.
43

44. Types of Bridges based on
Types of Bridges based on
Function
Function
 Foot bridge
 Highway bridge
 Rail way bridge
 Aqueduct bridge
 Aqueduct bridge
 Road cum railway bridge
44

45. Foot Bridge
Foot Bridge
 Foot Bridge is generally constructed for
humans to cross the roads or rail route
or any canal by foot.Vehicles are not
allowed in this bridge
allowed in this bridge
45

46. Highway Bridge
Highway Bridge
 High way or roadWay Bridge is used for
road transportation.
46

47. Railway Bridge
Railway Bridge
 Rail bridges are constructed for rail
transportation.
47

48. Aqueduct Bridge
Aqueduct Bridge
 Aqueduct bridges are nothing but water
carrying bridges
48

49. Road cum Railway Bridge
Road cum Railway Bridge
 This type of bridge is useful for both road
way and railway transport.
49

50. Types of Bridges based on
Types of Bridges based on
Utility
Utility
 Temporary bridge
 Permanent bridge
50

51. Temporary Bridge
Temporary Bridge
Temporary bridges are constructed at low
cost for temporary usage
51

52. Permanent Bridge
Permanent Bridge
 These bridges are constructed for long
term use and maintained at high level.
Steel or R.C.C bridges are come under
this category.
this category.
52

53. FIELD SURVEYS
FIELD SURVEYS
53

54. FIELD SURVEYS
FIELD SURVEYS
Before a highway alignment is finalized in highway project,
the engineering surveys are to be carried out.
And these surveys are carried out in four stages.
The first three stages consider all possible alternate
alignment i.e. various requirements of highway alignment
and fourth stage is meant for detailed survey of the selected
alignment.
54

55. STAGES OF ENGINEERING SURVEYS
Map study
Reconnaissance
survey
Reconnaissance
survey
Preliminary surveys
Final location and
detailed surveys
55

56. MAP STUDY
It is a kind of
study of
topographic
The main
features like
By careful study
of such maps ,
it is possible to
topographic
map of an area,
so as to suggest
the possible
routes of the
road.
features like
river , hills ,
valley etc. are
also shown in
this map.
it is possible to
have an idea of
several
alternate
routes of the
road.
56

57. RECONNAISSANCE SURVEY
It is a second stage of surveys and used
to examine the general character of
the area for deciding the most feasible
routes for detailed studies.
routes for detailed studies.
A field surveyor may inspect a fairly
broad stretch of land along the
proposed alternative routes of the
map in the field.
57

58. Objectives of
Objectives of Reconnaissance Survey
To obtain general knowledge of the entire
territory.
To obtain specific information of salient
features of the area.
To obtain specific information of salient
features of the area.
To collect information about the soil type
along the route.
To collect information about sources of
construction materials.
58

59. PRELIMINARY SURVEY
• To conduct the survey for
alternate alignments propose
after reconnaissance.
• To compare the different
proposals in view of the
• To compare the different
proposals in view of the
requirement of a good
alignment.
• To collect necessary physical
information and details of
topography, drainage and soil.
• To estimate quality of earth
work materials.
OBJECTIVES
59

60. Procedure of preliminary survey
1. Primarytraverse.
The first step in the preliminary survey is to establish the primary
traversefollowingthelinerecommendedinthereconnaissance.
2. Topographicalfeatures.
All geographical and other man made features along the transverse and
foracertainwidtharesurveyedandplotted.
foracertainwidtharesurveyedandplotted.
3. Levellingwork.
 Levelling work is also carried out side by side to give the center line
profilesandtypicalcrosssection.
4. DrainagestudiesandHydrologicaldata.
Drainage investigations and hydrological data are collected so as to
estimate the type, number and approximate size of cross drainage
structures.
60

61. Preliminary survey continued…
6. MATERIALSURVEY
This survey is done for naturally occurring materials like stone
aggregatesandidentificationofsuitablequarries.
7. TRAFFICSURVEY
7. TRAFFICSURVEY
This survey is conducted in the region for deciding the
number of traffic lanes and roadway width, pavement design
andeconomicanalysisofhighwayproject.
8. DETERMINATIONOF FINALCENTERLINE
After completing the preliminary survey and conducting the
comparative studies of alternate alignments the final center line of
the road is to be decided before the final locationsurvey.
61

62. FINAL LOCATION AND DETAILED SURVEY
 The alignment finalized after the preliminary survey and then detailed
surveyiscarriedoutforthepreparationofplansandconstruction details.
 Thelocationsurveyiscarriedoutintwostages;
1. On paperlocation
2. Fieldlocation
1. On paperlocation.
 Thefinalrouteisputonthedrawingsanddetailssuchasgradient ,radius
ofcurvesetc.aremarkedclearly.
2. Fieldlocation
 On paper location is transferred to the field with the help of transit
theodoliteandpreciselevel.
62

63. DETAILED SURVEY
 Temporary bench marks are fixed at the interval
of 250m.
 Vertical alignment, earth work and drainage
details areworkedoutfromlevelnotes.
details areworkedoutfromlevelnotes.
 A detailed soil survey is carried out and soil
profileis established.
 All rivers and valley are surveyed in detail up
toconsiderable distance on eithersides.
63

64. Waterway
 The area through which the water flows
under a bridge superstructure is known
as the waterway of the bridge.
 The linear measurement of this area along
 The linear measurement of this area along
the bridge is known as the linear
waterway.
 This linear waterway is equal to the sum
of all the clear spans.
64

65. Waterway Continued…
 Due to the construction of a bridge, the
natural waterway gets contracted thereby
increasing the velocity of flow under a
bridge.
bridge.
 This increased velocity results into
heading up of water on the upstream of
the river known as Afflux.
65

66. Waterway Continued…
While fixing the waterway of a bridge, the following
principles must be kept in mind.
 The increased velocity due to afflux should not exceed the
permissible velocity under the bridge
S.No Nature of Bed Permissible velocity in
66
S.No Nature of Bed Permissible velocity in
m/sec
1 Clay 2.10
2 Sandy Clay 1.50
3 Very fine sand 0.60 to 0.90
4 Fine sand 0.90 to 1.50
5 Fine Gravel 1.50 to 1.80
6 Rocky Soil 3.00
7 Rock 4.20 to 6.00

67.  There should not be too much heading
up of water surface above the bridge,
when it is necessary to restrict the
waterway to such an extent that the
waterway to such an extent that the
resultant afflux will cause the stream to
discharge at erosive velocity.
 The freeboard for high level bridge should
not be less than 600 mm.
67

68. Economic Span
 The economic span of a bridge is the one
which reduces the overall cost of the bridge
to be a minimum.
 The overall cost of a bridge depends upon
 The overall cost of a bridge depends upon
1. Cost of material and its nature
2. Availability of skilled labour
3. Span length
4. Nature of stream
5. Climatic and other conditions
68

69. Economic Span
 The most economic span length is that
which satisfies the following
The cost of super-structure= The
cost of sub-structure
cost of sub-structure
69

70. Assumptions of Economic Span
 The bridge has equal span length.
 The cost of the supporting system of super-
structure varies as the square of the span
length.
Cost of flooring and parapets varies directly
 Cost of flooring and parapets varies directly
as the span.
 Cost of one pier and its foundation is
constant.
 Cost of the abutments and their foundations
is also constant.
70

71. Derivation of Economic Span
71

72. Derivation of Economic Span
72

73. Numerical on Economic Span
73

74. Scour Depth
 Scouring can be defined as a process due to which
the particles of the soil or rock around the
periphery of the abutment or pier of the bridge
spanning over a water body, gets eroded and
removed over a certain depth called scour depth.
removed over a certain depth called scour depth.
 Scouring usually occurs when the velocity of the
flowing water increases or crosses the limiting
value that the soil particles can easily handle
74

75. Scour Depth Continued…
 Estimation of scour depth is very
important for the design of foundation for
abutment or pier.
 It has been estimated that over 60 % of
 It has been estimated that over 60 % of
the bridges are being collapsed due to
scouring.
75

76. Scour Bridge Failures
76

77. Scour Depth
77

78. Scour Depth
78

79. 79

80. Depth of Foundation
 The depth of foundations for substructures
shall be determined from the consideration
of the safe bearing capacity of the soil after
taking into account the effect of scour.
taking into account the effect of scour.
 The safe bearing capacity of the soil is
ascertained by actual field load test.
80

81. Depth of Foundation

81

82. Depth of Foundation for Hard Beds
 Where a substantial stratum of solid rock or other
inerodable material at anticipated maximum
velocity and of adequate safe bearing capacity is
encountered on or at a shallow depth below the
surface,the foundation should be securely anchored
into it.
into it.
 The Rock should be benched by chiseling and a
number of bars of approx. 38 mm dia at about 0.8
m spacing should be provided to anchor the
foundation.
 Then a levelling course with lean cement concrete
is laid. Over this, the foundation is built.
82

83. Depth of Foundation for Erodable Strata
 When only erodable strata is available, the
foundation may be designed either as a deep
foundation or as shallow foundation given below.
In either case, the safe bearing capacity of sub soil
is not exceeded.
 Deep Foundation: The foundation should be
 Deep Foundation: The foundation should be
taken down to a depth below the maximum high
flood level one third greater than the calculated
maximum scour depth.
 Shallow Foundation: In case of sandy bearing
stratum, the foundation is laid down to a
comparatively shallow depth.
83

84. Afflux
 When a bridge is constructed, the structures
such as abutment and piers cause the
reduction of the natural waterway area.
And because of this contracted area,
 And because of this contracted area,
velocity under a bridge increases.
 This increased velocity gives rise to a
sudden heading up of water on the upstream
side of the stream.
84

85. Afflux Continued…
 This phenomenon of heading up of water
on the upstream side of the stream is
known as Afflux.
 Greater the afflux greater will be the
velocity under the downstream side of the
bridge and greater will be the depth of
scour and consequently greater will be the
depth of foundation required.
85

86. Afflux Continued…
 Afflux is calculated by one of the following
formula:
86

87. Numerical on Afflux
87

88. Free Board
 Free Board is the vertical distance
between the designed high flood level and
the level of the crown of the bridge at its
lowest point.
 It is required to allow floating debris,
 It is required to allow floating debris,
fallen tree trunks to pass under the
bridge.
 It is also required to allow for the afflux
during the maximum flood discharge due
to contraction of waterway.
88

89. Free Board
S.No Type of Bridge Free Board
1 High Level
Bridge
600 mm
89
2 Arch Bridge 300 mm
3 Girder Bridge 600 to 900 mm
4 Navigational
Streams
2400 to 3000
mm

90. Loadings for
Loadings for
Railway Bridge
90

91.  Indian Railways use the following three
types of RailwayTracks
1. Broad Gauge- 1676 mm
2. Metre Gauge- 1000 mm
3. Narrow Gauge- 762 mm
These Railway tracks are also known as Main
Line and Branch line according to traffic
intensities
91

92. Loads Considered in Railway Bridge
 Dead Load
 Live Load
 Impact Load
 Loads due to curvature of track
 Loads due to curvature of track
 Loads on parapet
 Wind Load
 Seismic Load
92

93. Dead Load
 Dead Load is the weight of the structure
itself.
 The Dead load stresses generally form
 The Dead load stresses generally form
about 15% of the total stresses
93

94. Live Load
 For Broad Gauge(1676 mm)
1. Standard M.L (main line)- 22.9 tonnes
axle loads and a train of 7.67 tonnes per
metre run behind the engines.
metre run behind the engines.
2. Standard B.L ( Branch line)- 17.3 tonnes
axle loads and a train of 5 tonnes per
metre run behind the engines.
94

95. Live Load
 For Metre Gauge(1000 mm)
1. Standard M.L (main line)- 13.2 tonnes
axle loads and a train of 3.87 tonnes per
metre run behind the engines.
metre run behind the engines.
2. Standard B.L ( Branch line)- 10.7 tonnes
axle loads and a train of 3.87 tonnes per
metre run behind the engines.
95

96. Live Load
 For Narrow Gauge( 762 mm)
1. A class (main line)- 8.1 tonnes axle loads
and a train of 2.83 tonnes per metre run
behind the engines.
behind the engines.
2. B class ( Branch line)- 6.1 tonnes axle
loads and a train of 2.83 tonnes per
metre run behind the engines.
96

97. Impact Load
 The Impact load should be taken as equal
to the live load giving the maximum stress
under the member under consideration
multiplied by an impact factor.
multiplied by an impact factor.
97

98. Load due to Curvature of Track
 The Load due to the centrifugal force is
considered when the track is undergoing a
horizontal curve
98

99. Loads on Parapet
 Loads of Railings or Parapets have to be
considered.
 They are to be designed to resist a
horizontal force and a vertical force each of
horizontal force and a vertical force each of
150 kg/m applied simultaneously at the top
of the railing or parapet.
99

100. Wind Load
 Wind load on a bridge will act
Horizontally, transverse to the direction
of span.
 Wind load effect is not generally
 Wind load effect is not generally
significant in short-span bridges but the
super structure design is affected by wind
in long spans.
 A wind load of 2.40 kN/m2 is adopted for
the span.
100

101. Seismic load
 If a bridge is situated in an earthquake prone
region, the earthquake or seismic forces are
given due consideration in structural design.
 Earthquakes cause vertical and horizontal
forces in the structure that will be
proportional to the weight of the structure.
forces in the structure that will be
proportional to the weight of the structure.
 Both horizontal and vertical components
have to be taken into account for design of
bridge structures.
 IS:1893 – 1984 may be referred to for the
actual design loads
101

102. BRIDGE
BRIDGE
FOUNDATION
102

103. Bridge Foundation
 A Foundation is that part of the structure which
is in direct contact with the ground.
 It transfers the load of the structure to the soil
below.
 Before deciding upon its size, it must ensure that
 Before deciding upon its size, it must ensure that
1. The bearing pressure at the base does not
exceed the allowable soil pressure.
2. The settlement of the foundation is within
reasonable limit.
3. Differential settlement is so limited as not to
cause any damage to the structure.
103

104. TYPES OF FOUNDATIONS
The different types of foundations for
bridges are following.
Shallow Foundation (D<B)
 Spread Foundation and Raft foundation
 Spread Foundation and Raft foundation
Deep Foundation (D>B)
 Pile and Well foundation
104

105. SHALLOW FOUNDATION
 A shallow foundation is sometimes defined
as one whose depth is smaller than its width.
 Shallow foundations can be laid using open
excavation by allowing natural slopes on all
sides.
This is normally convenient above the water
sides.
 This is normally convenient above the water
table and is practicable upto a depth of
about 5m.
 Shallow foundation transfers the load to the
ground by bearing at the bottom of the
foundation.
105

106. SPREAD FOUNDATION
 It is an enlargement at the bottom of a
column that spreads the applied structural
loads over a sufficiently large soil area.
 It is also known as footing
 It is also known as footing
 Each column has its own spread footing.
106

107. SPREAD FOOTING
107

108. RAFT FOUNDATION
 Raft foundation (sometimes known as Mat
Foundation) are a large concrete slab which
can support a number of columns.
 The slab is spread out under the entire
structure or at least a large part of it which
lowers the contact pressure compared to
structure or at least a large part of it which
lowers the contact pressure compared to
the traditionally used single footings.
 When the allowable soil pressure is low or
the bridge loads are heavy, the use of spread
footings would cover more than 50% of the
area and it may prove economical to use raft
foundation.
108

109. RAFT FOUNDATION
109

110. RAFT FOUNDATION
110

111. PILE FOUNDATION
 The Pile foundation is a construction for the
foundation of a bridge pier or abutment
supported on a pile is an element of
construction composed of concrete or steel.
 This type of construction is adopted when
 This type of construction is adopted when
the loose soil extends to a great depth.
 The load of the bridge is transmitted by the
piles to hard stratum below or it is resisted
by the friction developed on the sides of the
piles.
111

112. Classification of Piles
 Piles are broadly classified into two
categories
1. Classification based on the function
2. Classification based on materials and
2. Classification based on materials and
composition
112

113. Classification based on the function
 Bearing pile
 Friction Pile
 Screw Pile
 Compaction Pile
 Compaction Pile
 Uplift Pile
 Batter Pile
 Sheet Pile
113

114. (i) End bearing piles:
 The piles which transfer its load to a hard
and relatively incompressible stratum like
rock or dense sand are called end bearing
piles. These piles derive its bearing
capacity from end bearing at the pile tip.
(ii) Friction piles:
(ii) Friction piles:
 The piles which do not rest on hard
stratum but derives its carrying capacity
from skin friction or adhesion between
the pile surface and surrounding soil are
called friction piles.
114

115. 115

116. (iii)Tension pile:
 Tension piles are also called uplift piles.
These piles are used to anchor down the
structures subjected to uplift due to
hydrostatic pressure.
(iv) Compaction piles:
(iv) Compaction piles:
 These piles are used to compact loose
granular soil to increase its bearing capacity.
Compaction piles do not carry load and
hence they can be of weaker material. Sand
piles can be used as compaction piles
116

117. (V)Screw piles:
Sometimes referred to as screw
anchors, screw-piles, helical piles,
and helical anchors are a steel screw-in
piling and ground anchoring system used
for building deep foundation.
for building deep foundation.
117

118. Classification based on material and
composition
 Cement concrete piles
 Timber Piles
 Steel Piles
 Sand Piles
 Sand Piles
 Composite Piles
118