Bridge and location of bridge, Drawing required for highway project ,Factors affecting selection of Bridge Site,Field survey, etc.

1. WHAT IS BRIDGE ??
-WHEN THE WATER WAY IS MORE THAN 6 METER THE CROSS-DRAINAGE
STRUCTURE IS PROVIDED TO CROSS STREAMS AND OTHER BODIES OF WATER
IS CALLED BRIDGE.
-A BRIDGE SHOULD BE DESIGNED TO CARRY IRC STANDARD LOADING WITH
REASONABLE AMOUNT OF SAFETY, AND SHOULD FIT INTO THE SURROUNDING
LANDSCAPE.
Highway Engineering
Bridge and Location of a Bridge

2. Ideal Location For a Bridge Site
 A straight reach of a river, so that the piers of
the bridge can be located parallel to the direction
of flow.
 There should be steady regime of a river and
absence of serious whirls or cross-currents.
 Availability narrow and well defined channel.
 Absence of a sharp curve e in approaches, so that
Scouring(erosion) and Silting(deposition) action
can be prevented.

3. Ideal Location For a Bridge Site
 Preferring reasonable
proximity(availability) to the direct
alignment of road to be served .
 Rocky or other compact and non-erodable
bed is preferrable.

4. Factors affecting selection of Bridge
Site
 Width of a River:- The site at which there is least width of
the river is available is suitable for construction of a
bridge.
 A Straight Approach:- Cross-section of a bridge should be
straight as far as possible, because a straight bridge is far
more stable than a curved bridge.
 River Banks:-
 Velocity of the Flow:- The place where the velocity of the
water flow is min. considering the width of the river is
suitable for bridge cons.

5. Factors affecting selection of Bridge
Site
 Free Board:-
 Absence of Scouring and Silting:- There
should be no erosion and deposition of the
rock and other materials like sand, silt, gravel,
on either side of the river. This can cause a
failure to the piers of the bridge..
 No confluence of large Tributaries:-
Construction of a bridge should be carried out
at such a site where no large tributaries of
rivers meet.

6. Data to be collected for location of a
Bridge Site
 Type of soil:- Necessary information about the soil type and its
condition should be collected by the geologist/engineer and should
ensure that the soil bed conforms the I.S. for the particular bridge const.
 Avail. of Electricity:-Ample amount of electricity and its sources and
substitutes should be made available in const. of a bridge site.
 Avail. of Skilled&Unskilledlabours:- Construction of different
components of bridge needs different type of labours in considerable
amount .
 Hydrological Data:- Collection of info. about the Rainfall, Run-off,
Infiltration by soil, Evaporisation, Velocity of flow etc .
 Avail. of Const. Material:- More than ample amount of const. material
should be available at all time.

7. Data to be collected for location of a
Bridge Site
 Possibility of Navigation Facilities:- Navigation of heavy
machinery should be possible at site.
 Possibility of Earthquake:- A site for bridge const. should be
least prone to earthquake, and necessary data of past EQ should
be collected and acc. to it bridge should be designed.
 Present and Future Traffic Volume:- The width of a carriage
way of bridge should fulfill the traffic requirements of the
present and future conditions of the surrounding areas.

9. FIELD SURVEY.
Before a highway alignment is finalised 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.

10. STAGES OF ENGINEERING SURVEYS.
THE FOUR STAGES OF ENGINEERING
SURVEYS:-
1. Mapstudy
2. Reconnaissance
3. Preliminarysurveys
4. Finallocationanddetailedsurveys

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

12. Details from the map.
 Alignment avoiding valleys , ponds or lakes.
 In hills , possibility of crossing through a
mountain pass.
 Approximate location of bridge site for
crossing rivers.
 Alternate route with permissible gradient.

13. RECONNAISSANCE
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. A field surveyor may inspect a
fairly broad stretch of land along the proposed alternative
routes of the map in the field.

14. OBJECTIVES
 To obtain general knowledge of the entire
territory.
 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.

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

16. Procedure of preliminary survey
1. Primary traverse.
The first step in the preliminary survey is to establish the primary
traverse following the line recommended in the reconnaissance.
2. Topographical features.
All geographical and other man made features along the transverse
and for a certain width are surveyed and plotted.
3. Levelling work.
Levelling work is also carried out side by side to give the center line
profiles and typical cross section.
4. Drainage studies and Hydrological data.
Drainage investigations and hydrological data are collected so as to
estimate the type, number and approximate size of cross drainage
structures.

17. 5. SOIL SURVEY
It is an essential part of preliminary survey and by help of this
survey final location is being decided.
6. MATERIAL SURVEY
This survey is done for naturally occurring materials like
stone aggregates and identification of suitable quarries.
7. TRAFFIC SURVEY
This survey is conducted in the region for deciding the
number of traffic lanes and roadway width, pavement
design and economic analysis of highway project.
8. DETERMINATION OF FINAL CENTER LINE
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
location survey.

18. FINAL LOCATION AND DETAILED SURVEY
The alignment finalised after the preliminary survey then detailed
survey is carried out for the preparation of plans and construction
details.
The location survey is carried out in two stages;
1. On paper location
2. Field location
1. On paper location.
The final route is put on the drawings and details such as gradient
, radius of curves etc are marked clearly.
2. Field location
On paper location is transferred to the field within help of transit
theodolite and precise level.

19. DETAILED SURVEY
 Temporary bench marks are fixed at the at the interval
of 250m.
 Vertical alignment , earth work and drainage details
are worked out from level notes.
 A detailed soil survey is carried out and soil profile is
established.
 Work on all rivers and valley are surveyed in detail up
to considerable distance on either sides.

20. DRAWING REQUIRED FOR HIGHWAY
PROJECT
 IN A HIGHWAY PROJECT,THE FOLLING
DRAWING ARE REQUIRED:-
 KEY PLAN
 INDEX MAP
 PRELIMINARY SURVEY PLANS
 DETAILED PALNS
 LONGITUDINAL SECTION
 CROSS SECTION
 LAND ACQUISITION PLANS
 DEAWING OF ROAD INTERSECTION

21. KEY MAP
 It shows how actually the project has to be
done
 Map showing proposed and existing roads
 Importatant places to be connected
 Size of the map should not exceed
240x330mm(A4 size)
 Scale should be chosen depending upon the
area

22. INDEX MAP
 It shows how actully the highway project
looks like
 It shows the general topography of the area
 Details are symbolically represented
 Size of the map should not exceed
240x330mm(A4 size)
 The usual scale is 1cm=0.5km

23. PRELIMINARY SURVEY PLANS
 It shows the details of various alternative
alignments
 It shows all the information collected during
preliminaery survey
 Its size from 240x330mm(A4 size) to
880x1230mm(A0).
 Scale 10cm=1km

24. DETAILED PALNS
 It shows the ground plan with alignment and
boundaries,countour at interval 1 to 2 m in
plain country and 3 to 6 m in hilly areas.
 Size of the drawing may b 625x880 mm
 It should also the existing structures ,rivers
,physical features ,etc.

25. LONGITUDINAL SECTION
 The Longitudinal section(L-section) should be
drawn to a horizontal scale of 1:2000 and a
vertical scale of 1:2000
 The levels should be taken at 50m intervals for
plain and rolling terrain and at 25m interval for
hilly terrain.
 The L-section should have information like
chainages ,horizontal and vertical alignment
,datum level ,ground level ,formation level
,depth of cutting ,height of filling ,posiotion of
cross-roads etc

26. CROSS-SECTION
 It should be drawn at to nstural scale of 1cm=2-
2.5 m
 It should be drawn in every 100m or where
abrupt changes in level
 It should include cross-section number,the
reduced distances and the area of cutting and
filling.
 In hill roads cross section should be drawn at
closer intervals.

27. LAND ACQUISITION PLANS
 It shows the land acquisition details.
 Generl details like building, wells, nature of
gradients and others details required for
assessing the values.
 The scale adpoted may b 1cm=40m or less.
 Drawing of road intersections should be
prepared showing all details of pavement ,
islands etc.