A Project Report

OnDESIGN AND ESTIMATION OF HIGH LEVEL BRIDGE

A project report submitted in partial fulfillment of the requirement for the award of Bachelor in Technology in Civil Engineering

By

M. NAGARAJU 09671A0126

S.CHANDRA SEKHAR 09671A0145

V.NITIN SANTHOSH 09671A0148

B.VENKATESH 09671A0152

Under the esteemed guidance ofSmt. G.ARUNA LATHA (M. Tech, Ph. D)

Professor

DEPARTMENT OF CIVIL ENGINEERINGJ.B.INSTITUTE OF ENGINEERING AND TECHNOLOGY

(AFFILIATED TO JNTUH)YENKAPALLY, MOINABAD, HYDERABAD-500075

2012-2013

DEPARTMENT OF CIVIL ENGINEERING

CERTIFICATE

This is to certify that the project entitled “DESIGN AND ESTIMATION OF HIGH LEVEL BRIDGE” has been carried out by students mentioned below in partial fulfillment of the degree of bachelor of technology in civil engineering. J.B.INSTITUTE OF ENGINNERING AND TECHNOLOGY during the academic year 2012-2013.

BY

M.NAGARAJU 09671A0126

S.CHANDRA SEKHAR 09671A0145

V.NITIN SANTHOSH 09671A0148

B.VENKATESH 09671A0152

INTERNAL GUIDE EXAMINER HEAD OF THE

DEPARTMENT

ACKNOWLEDGEMENT

We are extremely beholden and own an irredeemable debt of

gratitude to and we shall never be able to express our gratefulness in words to

our guide who not only shared technical knowledge but has a constant source of

inspiration throughout our project work. We express our sincere gratitude to

Smt. G.ARUNA LATHA, Professor, Department of Civil Engineering,

J.B.I.E.T.

We express our deep sense of gratitude, respect and indebtedness to

Er. T.L. RAMADASU, Head of Department, Civil for providing a good

environment for completing our project work. We express our sincere thanks to

Dr. K.V.J RAO, Principal, Dr. G. JAGMOHAN DAS, Advisor and Dr.

KOTHARI, Director General, J.B.I.E.T for providing us the beloved lectures,

parents and friends for their encouragement and well wishes during our project

work.

We here by express our profound sense of gratitude to my external

guide Mr. V.NIRANJAN RAO, ASSISTANT ENGINEER in Tribal Welfare

Department Bhadrachalam (ITDA),” for taking pain in helping us to

accomplish our project successfully.

DECLARATION

We, the following students of J.B.I.E.T

M. NAGARAJU 09671A0126

S.CHANDRA SEKHAR 09671A0145

V.NITIN SANTHOSH 09671A0148

B.VENKATESH 09671A0152

Studying IV year II semester B.Tech Civil Engineering hereby declare that the project entitled “DESIGN AND ESTIMATION OF HIGH LEVEL BRIDGE” has been carried out by us under the guidance of Smt. G.ARUNA LATHA. This work has been submitted in partial fulfillment of the requirements for the award of Bachelor of Technology in Civil Engineering by Jawaharlal Nehru Technological University during the academic year 2012-2013

Name of the candidate Signature of the candidate

M. NAGARAJU

S.CHANDRA SEKHAR

V.NITIN SANTHOSH

B.VENKATESH

CONTENTS Pg. No.

ABSTRACT

1. INTRODUCTION 1

2. PURPOSE 2

3. LOCATION OF THE PROJECT 3

4. HISTORY 4

5. CLASSIFICATION OF BRIDGES 5

6. TERMINOLOGY AND NOMENCLATURE 11

6.1 SUPER STRUCTURE 11

6.1 .1 Wearing surface 11

6.1.2 Lateral Bracing 12

6.1.3 Deck 13

6.1.4 Primary members 13

6.1.5 Secondary Members 14

6.2 SUB STRUCTURE 14

6.2.1 Abutments 14

6.2.2 Piers 15

6.2.3 Bearings 16

6.2.4 Pedestals 16

6.2.5 Wing wall 17

7. DATA COLLECTION 19

7.1 Preliminary data to be collected 19

7.2 Selection of Bridge site 20

7.3 Stages of Investigation 22

7.4 Bridge Alignment 24

7.5 Traffic Requirement of Highway Bridges 25

7.6 Waterway of a Bridge 26

7.7 Maximum Flood Discharge 27

7.8Loads and Load Combinations 29

7.9Foundations 36

7.10 Cofferdams 38

8. DESIGN DATA 39

8.1 Design procedure Adopted 42

8.2 Live Load eccentricity calculations 43

9. CALCULATIONS 44

9.1Calculation of Discharge 44

9.2 Calculation of Linear Waterway 49

9.3 Calculation of Scour Depth 50

9.4 Span Arrangement 52

9.5 Salient features 53

10. INITIAL PREPARATION 54

10.1 Removal of structures and obstructions 54

10.2 Excavation and embankment 56

10.3 Rock Blasting 64

11. AUTO CADD VIEWS 70

12. ESTIMATE DATA 76

13. BRIDGE ACCESSORIES 81

13.1 Parapets 81

13.2 Expansion joints 82

13.3 Drainage 84

13.4 Water Proofing 86

13.5 Bearings 86

14. CONCLUSION 89

15. REFERENCES 90

ABSTRACT

This project we have done is under the aegis of Integrated Tribal Development

Agency (ITDA), Government of Andhra Pradesh. The site is located in Yellandu Mandal

about 14.80 km from the town. It is located at a distance of 64.80 km from Khammam town

of Khammam District. Its satellite location on map is given as Latitude 17° - 65’

Longitude 80° - 25’.

The careful investigation at the preliminary stage avoids many expensive

errors at a later stage. We have collected preliminary data which helps in arriving at the

design procedure to be selected.

1. INTRODUCTION

A bridge is an arrangement made to cross an obstacle in the form of a low ground

or a stream or a river or over a gap without closing the way beneath. The bridges are required for

the passage of railways, roadways, footpaths and even for the carriage of fluids.

It is quite evident that the development of the science of bridge engineering has

taken place with the development of human civilization. In the beginning, the men used fallen

trees or wooden logs to function as bridges. The bridges serve as the most useful links on the land

connecting big towns and cities and hence, in case of war or calamities, the destruction of bridges

stops the mobility of army or essential goods. The site of a bridge should therefore be properly

selected with respect to strategic considerations and all proper precautions and measures should

be taken to maintain the bridges in the perfect working order.

The construction of bridge in a road or rail project is the costliest part and hence, it

calls for the utmost economy. It takes the longest time for completing and requires careful

planning, considerable amount of forethought and detailed study of various aspects. It may also be

noted that the bridges across rivers and streams are the most vulnerable because any major

damage to the structure can completely upset the total communication system. It is for this reason

that no undue risk can be taken in their design and construction. The economy in bridge

construction as well as its long life can be successfully achieved only by the use of proper

materials, effective supervision and economic method of construction.

2. PURPOSE

A bridge is a structure built to span physical obstacles such as a body of

water, valley, or road, for the purpose of providing passage over the obstacle. There are many

different designs that all serve unique purposes and apply to different situations. Designs of

bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is

constructed, the material used to make it and the funds available to build it.

Mainly to achieve more direct paths of circulation between two points, sorting out

obstacles such as gaps, treacherous terrain, bodies of water, etc.

Strategical View of the bridge

3. LOCATION

The site is located in Yellandu Mandal about 14.80 km from the town. It is located at

a distance of 64.80 km from Khammam town of Khammam District. Its satellite location on

map is given as

Latitude 17° - 65’ Longitude 80° - 25’

The bridge was constructed by Integrated Tribal Development Agency (ITDA)

Department, recognized by Govt. of Andhra Pradesh.

Location of bridge

4. HISTORY

The earliest construction of permanent bridges started around 4000 B.C. The lake

dwellers of Switzerland are said to be the pioneers of timber-trestle construction. The Indians also

developed the prototype of the modern suspension bridge at about the same time.

The Arthashastra of Kautilya mentions the construction of dams and

bridges a Mauryan bridge near Girnarwas surveyed by James Princep. The bridge was swept

away during a flood, and later repaired by Puspa gupta, the chief architect of

Emperor Chandragupta I. The bridge also fell under the care of the Yavana Tushaspa, and

the Satrap Rudradaman. The use of stronger bridges using plaited bamboo and iron chain was

visible in India by about the 4th century. A number of bridges, both for military and commercial

purposes, were constructed by the Mughal administration in India.

The science of bridge engineering developed with varied degrees in different

countries. Some of the Roman bridges in Italy are among the fine bridges of the past. In the

eighteenth century, France was the most powerful country of continental Europe and because of

its prosperity and taste in art, it has produced numerous and the finest bridges during this period.

It is really a pleasure to see the existing century bridges in France. The bridge over the river Nile

built by Means, the king of Egypt about 2650 B.C. was the earliest bridge on record. After five

centuries, another bridge was built by Queen Semiramio of Babylon across the River Euphrates.

The oldest existing arch dating back to about 350 B.C. and consisting of 20 pointed arches each of

7.5m span is at Khorsbad in Babylonia. The Roman arch bridges date back to 200 B.C. The Chao-

Chow Bridge situated at a distance of about 350 km from Beijing is supposed to be built around

600 A.D. and is perhaps the longest single span of 37.4 m vehicular bridge at present. Timber

gave place to iron as building material in eighteenth century. The first iron bridge of 30.5 m span

was built in 1779 over the Severn in Coalbrookdale, England.

5. CLASSIFICATION OF BRIDGES

The bridges can be classified by many ways with respect to particular quality or

condition. Following are such various classifications of the bridges:

CRITERIA TYPES OF BRIDGES

FLEXIBILITY OF SUPER STRUCURE

FIXED SPAN BRIDGE

MOVABLE BRIDGE

POSITION OF BRIDGE FLOOR DECK BRIDGES

THROUGH BRIDGES

SEMI-THROUGH BRIDGES

INTERSPAN RELATIONS

SIMPLE BRIDGES

CONTINUOUS BRIDGES

CANTILEVER BRIDGES

TYPE OF SUPERSTRUCTURE

ARCH BRIDGE

BOW-STRING BRIDGE

RIGID FRAME BRIDGE

SUSPENSION BRIDGE

MATERIALS OF CONSTRUCTION

CEMENT CONCRETE BRIDGES

MASONRY BRIDGE

STEEL BRIDGE

TIMBER BRIDGE

METHOD OF CLEARANCE FOR

NAVIGATION

BASCULE BRIDGE

CUT-BOAT BRIDGE

LIFT BRIDGE

SWING BRIDGE

TRAVERSING BRIDGE

MAIN FUNCTION OF BRIDGE

ROAD BRIDGE

RAILWAY BRIDGE

ROAD-CUM-RAILWAY BRIDGE

PIPE-LINE BRIDGE

METHOD OF CONNECTIONS

ADOPTED

RIVETED BRIDGE

WELDED BRIDGE

PIN-CONNECTED BRIDGE

LENGTH OF SPAN

CULVERT

MINOR BRIDGE

MAJOR BRIDGE

LONG SPAN BRIDGE

DEGREE OF REDUNDANCY DETERMINATE BRIDGE

INDETERMINATE BRIDGE

LEVEL OF CROSSING OVER BRIDGES

UNDER BRIDGES

ALIGNMENT OF BRIDGE STRAIGHT BRIDGES

SKEW BRIDGES

Bridges may be classified by how tension, bending, compression, and shear are

distributed through their structure. Most bridges will employ all of the principal forces to some

degree, but only a few will predominate. The separation of forces may be quite clear. In a

suspension or cable-stayed span, the elements in tension are distinct in shape and placement. In

other cases the forces may be distributed among a large number of members, as in a truss, or not

clearly discernible to a casual observer as in a box beam.

Beam

Bridge 

Beam bridges are horizontal beams supported at each end by substructure units and can be either simply when the beams only connect across a single span or continuous when the beams are connected across two or more spans. When there are multiple spans, the intermediate supports are known as piers. The earliest beam bridges were simple logs that sat across streams and similar simple structures. In modern times, beam bridges can range from small, wooden beams to large, steel boxes. The vertical force on the bridge becomes a shear and flexural load on the beam which is transferred down its length to the substructures on either side. They are typically made of steel, concrete or wood. Beam bridge spans rarely exceed 250 feet (76 m) long, as the flexural stresses increase proportional to the square of the length (and deflection increases proportional to the 4th power of the length). However, the main span of the Rio-Niteroi Bridge, a box girder bridge, is 300 meters (980 ft).The world's longest beam bridge is Lake Pontchartrain Causeway in southern Louisiana in the United States, at 23.83 miles (38.35 km), with individual spans of 56 feet (17 m). Beam bridges are the most common bridge type in use today.

Truss bridge 

A truss bridge is a bridge whose load-bearing superstructure is composed of a truss. This truss is a structure of connected elements forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges.

Cantilever

bridge 

Cantilever bridges are built using cantilevers—horizontal beams supported on only one end. Most cantilever bridges use a pair of continuous spans that extend from opposite sides of the supporting piers to meet at the center of the obstacle the bridge crosses. Cantilever bridges are constructed using much the same materials & techniques as beam bridges. The difference comes in the action of the forces through the bridge.

The largest cantilever bridge is the 549-metre (1,801 ft)

Quebec bridge in Quebec, Canada.

Arch bridge 

Arch bridges have abutments at each end. The weight of the bridge is thrust into the abutments at either side. The earliest known arch bridges were built by the Greeks, and include the Arkadiko Bridge.

With the span of 220 meters (720 ft), the Solkan Bridge over

the Soca River at Solkan in Slovenia is the second largest stone

bridge in the world and the longest railroad stone bridge. It was

completed in 1905. Its arch, which was constructed from over

5,000 tonnes (4,900 long tons; 5,500 short tons) of stone blocks

in just 18 days, is the second largest stone arch in the world,

surpassed only by the Friedensbrucke (Syratalviadukt)

in Plauen, and the largest railroad stone arch. The arch of the

Friedensbrücke, which was built in the same year, has the span

of 90 m (300 ft) and crosses the valley of the Syrabach River.

The difference between the two is that the Solkan Bridge was

built from stone blocks, whereas the Friedensbrücke was built

from a mixture of crushed stone and cement mortar.

The world's current largest arch bridge is the Chaotian Bridge

over the Yangtze River with a length of 1,741 m (5,712 ft) and

a span of 552 meters (1,811 ft). The bridge was open April 29,

2009 in Chongging, China.

Tied arch Tied arch bridges have an arch-shaped superstructure, but differ from conventional arch bridges. Instead of transferring the weight of the bridge and traffic loads into thrust forces into the abutments, the ends of the arches are restrained by tension in the bottom chord of the structure. They are also called

bridge 

bowstring arches.

Suspension bridge 

Suspension bridges are suspended from cables. The earliest suspension bridges were made of ropes or vines covered with pieces of bamboo. In modern bridges, the cables hang from towers that are attached to caissons or cofferdams. The caissons or cofferdams are implanted deep into the floor of a lake or river. Sub-types include the simple suspension bridge, the stressed ribbon bridge, the under spanned suspension bridge, the suspended-deck suspension bridge, and the self-anchored suspension bridge

The longest suspension bridge in the world is the 12,826 foot

(3,909 m) Akashi Kaikyo Bridge in Japan.

Cable-stayed

bridge 

Cable-stayed bridges, like suspension bridges, are held up by cables. However, in a cable-stayed bridge, less cable is required and the towers holding the cables are proportionately shorter. The first known cable-stayed bridge was designed in 1784 by C.T. Loescher]

The longest cable-stayed bridge is the Sutong bridge over the

Yangtze River in China.

According to the road engineers, the bridges are classified on the linear waterway as follows: 1)

Culverts (Up to 6m) 2) Minor bridges (6 to 30 m) 3) Major bridges (over 30m)

According to the Indian Railways, the bridges are classified as follows:

1) Major bridges : Total waterway more than 18m or having any span of clear water way of 12m or over.

2) Minor bridges : Total waterway less than 18m or having any span of clear waterway less than 12m.

3) Important bridges : Those major bridges having total waterway of 18m and more.

6. TERMINOLOGY AND NOMENCLATURE

As is the case with any profession, bridge engineering possesses its own unique

language which must first be understood by the designer in order to create a uniform basis for

discussion. A span is defined as of bridge from support to support. The following offers a

brief overview of some of the major bridge terms we will be using throughout the text.

6.1 Superstructure

The superstructure comprises all the components of a bridge above the supports.

The basic superstructure components consist of the following:

6.1.1 Wearing Surface

The wearing surface (course) is that portion of the deck cross section which resists traffic

wear. In some instances this is a separate layer made of bituminous material, while in some

other cases it is a of concrete deck. The integral wearing surface is typically 1/2 to 2 in(13 to

51 mm). The bituminous wearing course usually varies in thickness from 2 to 4 in (51 to 102

mm).

FIG: WEARING COAT

6.1.2 Lateral Bracing

Lateral bracing is a type of secondary member used to resist lateral deformation

caused by loads acting perpendicularly to a bridge's longitudinal axis. Wind forces are an

example of this type of loading. In addition to these inherit structural benefits, lateral bracing

also simplifies the construction process by allowing girders to be connected prior to erection

and installed as a unit larger due to resurfacing of the overpass roadway, which occurs

throughout the life cycle of a bridge.

FIG: LATERAL BRACING

6.1.3 Deck

The deck is the physical extension of the roadway across the obstruction to

be bridged. In an orthotropic bridge, the deck is a stiffened steel plate. The main function of

the deck is to distribute loads transversely along the bridge cross section. The deck either

rests on or is integrated with a frame or other structural system designed to distribute loads

longitudinally along the length of the bridge.

FIG: DECK SLAB

6.1.4 Primary Members

Primary members distribute loads longitudinally and are usually designed

principally to resist flexure and shear. In some instances, the outside or fascia primary

members possess a larger depth and may have a cover plate welded to the bottom of them to

carry heavier loads. Beam type primary members such as this are also called stringers or

girders. These stringers could be steel wide flange stringers, steel plate girders (i.e., steel

plates welded together to form an I section), pre stressed concrete, glued laminated timber, or

some other type of beam. Rather than have the slab rest directly on the primary member, a

small fillet or haunch can be placed between the deck slab and the top flange of the stringer.

The primary function for the haunch is to adjust the geometry between the

stringer and the finished deck. It is also possible for the bridge superstructure to be formed in

the shape of a box (either rectangular or trapezoidal). Box girder bridges can be constructed

out of steel or pre stressed concrete and are used in situations where large span lengths are

required and for horizontally curved bridges.

6.1.5 Secondary Members

Secondary members are bracing between primary members designed to

resist cross-sectional deformation of the super structure frame and help distribute part of the

vertical load between stringers. They are also used for the stability of the structure during

construction. A detailed view of a bridge superstructure shows channel-type diaphragms used

between rolled section stringers. The channels are bolted to steel connection plates, which are

in turn welded to the wide flange stringers shown. Other types of diaphragms are short depth,

wide flange beams or crossed steel angles. Secondary members, composed of crossed frames

at the top or bottom flange of a stringer, are used to resist lateral deformation. This type of

secondary member is called lateral bracing.

6.2 Substructure

The substructure consists of all elements required tosupport the

superstructure and overpass roadway. this would be Items 3 to 6. The basic substructure

components consist of the following

6.2.1 Abutments

Abutments are earth-retaining structures which support the superstructure and

overpass roadway at the beginning and end of a bridge. Like a retaining wall, the

abutmentresist the longitudinal forces of the earth underneath the overpass roadway.

Fig: Abutment

6.2.2 Piers

Piers are structures which support the superstructure at intermediate points

between the end supports (abutments). Like abutments, piers come in a variety of forms,

some of which are illustrated in the sidebar. From an aesthetic standpoint, piers are one of the

most visible components of a highway bridge and can make the difference between a visually

pleasing structure and an unattractive one.

Fig: Piers under construction

The bridge pier itself can vary in size and shape. This part of the bridge is

essentially a supporting pylon, and it can be shaped like a beam, or it may feature a more

sweeping shape, like a V. Generally, modern piers are made from concrete, though some can

be made of stone or even metal. A bridge pier designed to be submerged in water is likely to

be made of concrete, as metal can rust or otherwise corrode due to the constant exposure to

moisture. Before the bridge pier can be installed into the water, the river bottom or bottom of

the waterway must be dredged so the soil can support the weight of the pier and bridge

surface.

6.2.3 Bearings

Bearings are mechanical systems which transmit the vertical and horizontal

loads of the superstructure to the substructure, and accommodate movements between the

superstructure and the substructure. Examples of bearings are mechanical systems made of

steel rollers acting on large steel plates or rectangular pads made of neoprene. The use and

functionality of bearings vary greatly depending on the size and configuration of the bridge.

Bearings allowing both rotation and longitudinal translation are called expansion bearings,

and those which allow rotation only are called fixed bearings.

6.2.4 Pedestals

A pedestal is a short column on an abutment or pier under a bearing which

directly supports a superstructure primary member. The term bridge seat is also used to refer

to the elevation at the top surface of the pedestal. Normally pedestals are designed with

different heights to obtain the required bearing elevations.

6.2.5 Wing wall

In a bridge, the wing walls are adjacent to the abutments and act as retaining

walls. They are generally constructed of the same material as those of abutments. The wing

walls can either be attached to the abutment or be independent of it. Wing walls are provided

at both ends of the abutments to retain the earth filling of the approaches. Their design period

depends upon the nature of the embankment and does not depend upon the type or parts of

the bridge.

The soil and fill supporting the roadway and approach embankment are retained by the wing

walls, which can be at a right angle to the abutment or splayed at different angles. The wing

walls are generally constructed at the same time and of the same materials as the abutments.

Fig: Wing walls

Classification of wing walls

Wing walls can be classified according to their position in plan with respect to banks and

abutments. The classification is as follows:

1.Straight Wing walls: They are used for small bridges, on drains with low banks and for

railway bridges in cities (weep holes are provided).

2. Splayed Wing walls: These are used for bridges across rivers. They provide smooth entry

and exit to the water. The splay is usually 45°. Their top width is 0.5 m, face batter 1 in 12

and back batter 1 in 6, weep holes are provided.

3. Return Wing walls: They are used where banks are high and hard or firm. Their top width

is 1.5 m and face is vertical and back battered 1 in 4. Scour can be a problem for wing walls

and abutments both, as the water in the stream erodes the supporting soil.

7. DATA COLLECTION

7.1 Preliminary Data To Be Collected

The careful investigation at the preliminary stage avoids many expensive errors at a

later stage. Hence, the investigation process should be carried out diligently and with extreme care

to avoid the occurrence of serious mistakes in the bridge project. Following data should be

collected and suitably analyzed by the engineer-in-charge of the investigation of a bridge site:

Availability of electric power;

Availability of materials of construction;

Availability of skilled and unskilled labor for different jobs of bridge construction;

Characteristics and hydraulic data of stream or river;

Details of public utility services such as telephone cables, water supply lines, etc. to be

accommodated in the bridge cross-section;

Details of existing bridges on the same river;

Facilities required for housing labor during bridge construction;

Location of the nearest G.T.S. bench mark with its reduced level;

Means of transport to carry the materials;

Name of the river and location of the bridge site;

Navigational requirements;

Need for large scale training works;

Possibility of earthquake disturbances

Present and future traffic;

Reasons for constructing the bridge;

Safety and aesthetic considerations;

Subsoil conditions; etc.

7.2 Selection of Bridge Site

Following are the factors to be carefully considered while selecting the ideal

site for a proposed bridge:

Connection with roads: The bridges are constructed to connect the roads on either side

of the river. The bridge site should therefore form a proper link between the roads on

either side of a river. The bed of approaches connecting ends of bridge with the roads

should be dry and hard. The approaches at the bridge site should be such that they do

not involve heavy expenditure. The approaches should avoid the cutting across the

built-up area or religious structures because the acquisition of the land and structures

will be expensive, time-consuming and sometimes may cause social problems.

Firm embankments: The embankments on the upstream side and downstream side of

bridge site should be firm, high, permanent, solid, straight and well-defined. Such

embankments are not disturbed at the time of heavy floods and they do not allow the

course of river to alter.

Foundations: The nature of soil at the bed of river at bridge site should be such that

good foundations are available at reasonable depths for the substructures of bridge.

The site subject to minimum scour preferably is chosen.

Materials and labor: The site of the proposed bridge should be located that the

materials and labor required for the reconstruction of bridge are easily available. The

transport charges for materials and labor at bridge site should be minimum.

Right angle crossing: At bridge site, the direction of flow of water should be nearly

perpendicular to the centre-line of bridge. Such a crossing is known as the right-angle

crossing or square crossing or normal crossing and it is desirable to have such a

crossing as far as possible because of the following facts:

It grants a smooth flow of water.

It permits the construction of segmental wing walls and return walls with

minimum sharp angled structures and thereby, the formation of eddies and

cross currents are avoided,

It provides the shortest length of the bridge span as well as the length of the

pier and abutments.

The skew or slanting bridges are not desirable and they are usually avoided for the

following reasons:

It is difficult to construct the skew bridges, especially the skew arch bridges.

The depth of bridge foundations is likely to be more as foundations are to be

subjected to the scour.

The design of skew bridges is complicated.

The maintenance of skew bridges is difficult.

The passage of water under the skew bridges is not smooth and whirls or

currents are produced.

The piers of skew bridge have to resist excessive water pressures.

Straight stretch of river: The River should have a straight stretch over reasonable long

distance on the upstream side and downstream side of the bridge site. Such a straight

stretch of river ensures smooth and uniform flow of water and it allows smooth

navigation. The curved stretch of river is not desirable as it creates problems during

construction and maintenance of bridge.

Velocity of flow: It is very important to check that the velocity of flow at bridge site

is proper. If velocity of flow is less than a particular value, the silting will occur and

on the other hand, if it is more than a particular value, the scouring will occur. As a

matter of fact, the velocity of flow at bridge site should be between the range of non-

silting and non-scouring velocities.

Width of river: It is quite evident that the width of river indicates length of bridge. It

is desirable to have minimum width of river at the bridge site. The smaller the width

of river, the cheaper will be the bridge.

The conditions stated above are for an ideal site of a bridge. But in practice, it

is difficult to obtain a site which full fulfill all these conditions. Hence, every case has to be

studied independently and out of a number of alternatives, that site is to be recommended

which satisfies most of the conditions for an ideal site.

7.3 Stages of Investigation

The investigations for important or very major bridges are carried out in the

following three stages:

Reconnaissance or technical feasibility stage: In this stage, the entire length of the entire

length of the river within the area to be interconnected has to be studied so as to find out a

number of probable sites satisfying the various considerations for locating a bridge. The

numbers of factors satisfied by each site are noted and those sites which satisfy most of the

favorable factors are selected for further considerations in the next stage.

The factors to be studied in this stage can be mentioned as follows:

Estimating the benefits that will accrue from the likely traffic to pass over the bridge;

Gathering data about the behavior of the river at such sites by studying the valuable

reports;

Holding discussions with local knowledgeable people;

Making an assessment of construction problems;

Study of available maps;

Studying the existing pattern of traffic;

Visits to various possible sites so as to understand local features; etc.

It should be possible at this stage to narrow down the choice to three or four alternative

sites for the proposed bridge.

Preliminary or techno-economic feasibility stage: In the second stage, an attempt is made

to bring out in full detail the comparative merits and demerits of the various alternative

sites which are considered feasible in the first stage. The study of such a table would help

in choosing the best site of the bridge. It is also necessary to work out the estimated costs

of various alternative sites and such estimation should be done carefully so that final cost

may be within a range of plus or minus 15 per cent of the final cost. For this purpose,

some minimum field measurements are taken and detailed study maps of the area is made.

The details to be obtained for each site should be tabulated with respect to the following

aspects:

Construction and maintenance problems;

Distance from important city or town;

Expected duration of construction;

Length of approaches;

Length of bridge;

Nature of flow at site;

Nature of foundation strata;

Rate of return or benefit cost ratio;

Saving in detours involved, if any;

Total construction cost of bridge;

Volume of anticipated traffic; etc.

Depending upon the length of the river to be covered, the techno-economic

feasibility study can generally be completed in a period of about four to five months.

Detailed survey and project report stage: Out of possible alternatives, the final selection of

bridge site is made and in this stage, full investigations with respect to all items are carried

out for the selected site. The detailed studies are made for ground survey, hydrological

data, soil exploration, period of construction, volume of traffic, structural design, detailed

estimate, return on investment, construction schedule, etc.

Finally, the project report containing large number of drawings and necessary

details is prepared in such a shape that the sanction to the project can be issued; funds can

be allotted; field organization can be set up; and the work regarding the preparation of

tenders can be immediately started.

In case of very major bridges, it is necessary to carry out the model studies

because it is difficult to predict behavior of the river after a structure is put up across it. A

scale model prepared in a hydraulic research station is helpful in forecasting the behavior

of the river due to obstructions caused by embankment on either side and by piers.

7.4 Bridge Alignment

After the site of bridge is decided, the next step is to set out of align the center-

line of bridge. Following aspects of the bridge alignment should be carefully studied:

Alignment on curve: In hilly areas, it is not possible to avoid the alignment of bridge on a

curve. In such cases, it is necessary to adopt R.C.C or steel girders for the superstructure

and it should be seen that the axis of each pier is nearly parallel to the centre-line of river.

Control of highest flood level: The highest flood level or H.F.L. of river plays a great role

in fixing the height of the bridge. It is possible to control H.F.L. either by diverging the

extra flood water or by constructing a storage reservoir on upstream side of the river. It is

found that with controlled H.F.L., the design of bridge with adverse alignment can be

accurately made.

Effects of silting and scouring: The necessary precautions should be taken along the bridge

alignment to bring down the effects of silting and scouring to the minimum possible

extent.

Layout of approaches: If the existing road alignment is such that it results in an inclined

alignment, the curved approaches may be adopted to form right-angle or square crossing.

The layout of approaches is made with suitable curve radii so as to cause least

inconvenience to the traffic using such approaches.

River training works: If necessary, the river training works should be carried out to form

what are known as nodal points i.e., points of minimum displacement in a system of

stationary waves, along the bridge alignment. A nodal point is defined as the location

where the river regime does not normally shift. The natural nodal points are established by

the river flow over the years. The channels of the river shifting its course at the nodal

points will be minimum and thus, the stability of the structure is insured. For this purpose,

it is desirable to carry out experiments on models to decide the exact location of artificial

river training works along the river.

Skew bridges: As far as possible, the skew bridges should be avoided. However, if it is not

possible to adopt the right-angle crossing, great care should be taken in the design and

execution of skew bridges. The analysis and design of a skew bridge, especially when the

skew angle is more than 15 degrees, are more complicated and rigorous than those of a

right-angled bridge. The conditions which force the adoption of skew bridges are

excessive cost of land, acquisition for approaches, existing road alignment, length of

bridge, nature of flow, importance of bridge, etc.

Following precautions should be invariably taken in the design of skew bridges:

It is preferred to arrange the piers parallel to the axis of river.

The entry and exit of water below the skew bridge should be smooth.

The skew alignment should not be curved as it is difficult to construct and maintain

the curved bridge. The additional force due to the centrifugal action will come into

play in case of the curved bridge.

The skew should be restricted to 30 degrees.

7.5 Traffic Requirement of Highway Bridges

Following are the requirements of traffic which are to be considered in the design of

highway bridges:

Alignment: The sitting or location of bridge should fit in with the general road alignment.

It may require the adoption of skew bridges. It is the general practice to adopt the skew

bridges of small angle for small bridges and to adopt square crossings with suitable

approaches for long bridges.

Central verge: In interest of safety and traffic flow, it sometimes becomes desirable to

segregate or separate traffic flow of two directions by the provision of central verge. The

width of this strip should be kept low from the economic point of view. But it should not

be less than 1200 mm.

Footpath: The provision of footpaths on either side of the bridge will make movements of

pedestrian safe on the bridge and it will result in the reduction of fatal accidents on the

bridge. The width of the footpath will be decided by the volume of pedestrian traffic and

importance of the bridge. For rural areas, the minimum width of footpath should be kept as

1500 mm and it should be suitably in the case of urban areas. The capacity of 1500 mm

wide footpath can taken as 108 persons per minute and it should be increased at the rate of

600 mm for every additional capacity of 54 persons per minute.

Lighting: The lighting on bridge should be carefully designed with respect to distance

between adjacent posts, height of post, surrounding environment, importance of bridge,

etc.

Parapets and handrails: The provision of solid parapets or handrails should be made on

either side of the bridge to grant safety to the bridge users and to define the width of

bridge.

Roadway width: The minimum roadway widths required for vehicular traffic are

mentioned in codes. General roadway width for a two-lane bridge for vehicular traffic is

7.5m.

Safety kerbs: It is desirable to provide a safety kerb of size about 600 mm x 225 mm on

either side of roadway.

Sight distance: The provision of enough site distance on the highway bridges will ensure

the stopping of vehicles without collision. It is measured between points 1200 mm above

the roadway along the centerlines of both the nearside and offside lanes of the bridge. It

should be seen that the sight distance is not reduced below the minimum limit due to

obstructions such as shrubs, piers, abutments, etc. This precaution is necessary especially

in case of underpasses

7.6 Waterway of A Bridge

The most important factor to be decided in the design of bridges is the determination

of the waterway required for the bridge or culvert. The area under a bridge through which the

water flows is called the natural waterway of a bridge. For important and big bridges, it should be

designed to carry water at the time of maximum flood discharge.

The length of bridge available between the extreme edge of a water surface at the

highest flood level, measured at right angles to the abutment faces is known as linear waterway.

Following is the relation between waterway, maximum flood discharge and

permissible velocity:

A= Q / V

where A= waterway in m2

Q=Maximum flood discharge in m3 per second

V=Permissible velocity in m per second.

The linear waterway is obtained as follows:

L=A / d

Where L=Length of linear waterway

d= Average depth of water at bridge site.

The value of linear waterway so obtained is provided under a bridge. If piers or

intermediate supports are provided for the bridge, the sum total of spans between successive

supports should be equal to the linear waterway. The natural waterway is thus the total of linear

waterway and widths of supports of bridge.

To workout waterway of a bridge, it is necessary to arrive at a suitable value of

maximum flood discharge of the river.

7.7 Maximum Flood Discharge

Wherever possible, the maximum flood discharge at bridge site is found out

from at least two different methods and the higher of the two values is adopted as the

discharge for designing the bridge. If the values by two different methods differ by more than

50% than maximum design discharge is limited to 1.5 times the lower estimate. This is due to

the fact that from point of view of economy, it is not desirable to design the bridge for flood

of extraordinary high intensity which will rarely occur due to reasons such as failure of dam

or tank on the upstream side of bridge site.

It is considered reasonable to design bridges for floods occurring once in 100

years and to design culverts for floods occurring once in 20 years. The design aspects should

however ensure that the likely damages due to rarer floods are brought down to the minimum

possible extent.

Following are the two methods of calculating the maximum flood discharge:

Direct method: In direct method, the area of cross section upto the H.F.L. and the

velocity of flow are determined. The multiplication of area and velocity gives the

maximum flood discharge.

Following procedure is adopted to measure the area of cross-section

upto the H.F.L. at bridge site:

The information regarding height of the highest flood level is carefully gathered and it

is confirmed, wherever possible, by flood marks. If there is railway track near the

bridge site, the signs of the highest flood discharge would usually be available in the

form of markings on railway cross-drainage works. However, in case of new road

formation in undeveloped or sparsely inhabited areas, the engineer during

investigation has to decide the height of the highest flood discharge by contacting

elderly inhabitants of the area and by observing the river banks, deposits of debris on

tree trunks, etc.

Usually, three widths of river are selected. In addition to one at bridge site, one extra

is selected on upstream side as well as on downstream side. The distance between the

bridge site and the position of extra width is about 1600 m.

Along the widths so marked, the levels of bed of river are taken. These levels are

plotted to a scale and cross-sections are obtained. The hydrographic surveying is used

for measuring the soundings which are vertical downward distances from the surface

of water to the river bed. The soundings are located by observations entirely from

boat or entirely from the shore or from boat as well as from shore. The sounding

machines in the form of battery-operated and electronic echo sounders are now

available. They directly measure the depth of water.

The height of H.F.L. is marked on the cross-sections. The areas of cross-sections upto

H.F.L. are then worked out. If A1, A2 and A3 represent the areas of cross-sections 1-1,

2-2 and 3-3 respectively, the average area of cross-section is obtained as follows:

Average area of cross-section=( A1+ A2+ A3)/3

Measurement of velocity of flow is done by the following methods:

By using Chezy’s formula,

V=C (m i)1/2;

where V=velocity of flow in m per second

C= Chezy’s constant

m= hydraulic mean depth

i= slope of hydraulic grade line.

By direct observation also the velocity is obtained by following some methods:

The time taken by a surface float or velocity rod to travel from one line to the other is

noted. The surface float is to be adopted for small rivers. The velocity rod is adopted for large

rivers. The surface floats are made of light materials such as cork or drift wood and they are

generally of diameter varying from 80 mm to 160 mm. The velocity rods are made of hollow

metal tube or wood and they are generally of diameter varying from 30 mm to 50 mm. The

velocity rods are provided with weight at their bottom so that they can float vertically with

their top just above water surface. They are made of adjustable lengths to suit different depths

of water. The velocity rods directly measure the mean velocity hence no correction is

necessary, when they are used. But, when surface floats are used, they give surface velocity

and hence, to obtain mean velocity a correction factor is applied which varies from 0.8-0.9.

Indirect method: There are two indirect ways of estimating the maximum flood

discharge. They are rational method and by the use of empirical formulae.

7.8 Loads and Load Combinations

The following are the various loads to be considered for the purpose

of computing stresses, wherever they are applicable.

· Dead load

· Live load

· Impact load

· Longitudinal force

· Thermal force

· Wind load

· Seismic load

· Racking force

· Forces due to curvature.

· Forces on parapets

· Frictional resistance of expansion bearings

· Erection forces

Dead load – The dead load is the weight of the structure and any permanent load fixed

thereon. The dead load is initially assumed and checked after design is completed.

Live load – Bridge design standards specify the design loads, which are meant to

reflect the worst loading that can be caused on the bridge by traffic, permitted and

expected to pass over it. In India, the Railway Board specifies the standard design

loadings for railway bridges in bridge rules. For the highway bridges, the Indian Road

Congress has specified standard design loadings in IRC section II. The following few

pages brief about the loadings to be considered. For more details, the reader is

referred to the particular standard.

Railway bridges: Railway bridges including combined rail and road bridges are to be

designed for railway standard loading given in bridge rules. The standards of loading

are given for:

· Broad gauge - Main line and branch line

· Metre gauge - Main line, branch line and Standard C

· Narrow gauge - H class, A class main line and B class branch line

The actual loads consist of axle load from engine and bogies. The actual standard

loads have been expressed in bridge rules as equivalent uniformly distributed loads

(EUDL) in tables to simplify the analysis. These equivalent UDL values depend upon

the span length. However, in case of rigid frame, cantilever and suspension bridges, it

is necessary for the designer to proceed from the basic wheel loads. In order to have a

uniform gauge throughout the country, it is advantageous to design railway bridges to

Broad gauge main line standard loading. The EUDLs for bending moment and shear

force for broad gauge main line loading can be obtained by the following formulae,

which have been obtained from regression analysis:

For bending moment:

EUDL in kN = 317.97 + 70.83l + 0.0188l2 ≥ 449.2 kN (7.1)

For shear force:

EUDL in kN = 435.58 + 75.15l + 0.0002l2 ≥ 449.2 kN (7.2)

Fig: IRC AA Loading

Highway bridges: In India, highway bridges are designed in accordance with IRC

bridge code. IRC: 6 - 1966 – Section II gives the specifications for the various loads

and stresses to be considered in bridge design. There are three types of standard

loadings for which the bridges are designed namely, IRC class AA loading, IRC class

A loading and IRC class B loading. Fig.7.10 IRC AA loading

IRC class AA loading consists of either a tracked vehicle of 70 tonnes or a wheeled

vehicle of 40 tonnes with dimensions as shown in Fig. 7.10. The units in the figure are

mm for length and tonnes for load. Normally, bridges on national highways and state

highways are designed for these loadings. Bridges designed for class AA should be

checked for IRC class A loading also, since under certain conditions, larger stresses

may be obtained under class A loading. Sometimes class 70 R loading given in the

Appendix - I of IRC: 6 - 1966 - Section II can be used for IRC class AA loading.

Class 70R loading is not discussed further here.

Class A loading consists of a wheel load train composed of a driving vehicle and two

trailers of specified axle spacing’s. This loading is normally adopted on all roads on

which permanent bridges are constructed. Class B loading is adopted for temporary

structures and for bridges in specified areas.

For class A and class B loadings, reader is referred to IRC: 6 - 1966 – Section II.

Foot Bridges and Footpath on Bridges – The live load due to pedestrian traffic should

be treated as uniformly distributed over the pathway. For the design of footbridges or

footpaths on railway bridges, the live load including dynamic effects should be taken

as 5.0 kN/m2 of the footpath area. For the design of footpath on a road bridges or

road-rail bridges, the live load including dynamic effects may be taken as 4.25 kN/m2

except that, where crowd loading is likely, this may be increased to 5.0 kN/m2.

The live load on footpath for the purpose of designing the main girders has to be taken

as follows according to bridge rules:

(i) For effective spans of 7.5 m or less - 4.25 kN/m2

(ii) The intensity of load is reduced linearly from 4.25 kN/m2 for a span of 7.5 m to

3.0 kN/m2 for a span of 30m

(iii) For effective spans over 30 m, the UDL may be calculated as given below:

Where, P = Live load in kN/m2

l = Effective span of the bridge in m.

W = Width of the foot path in m.

Where foot-paths are provided on a combined rail-road bridge, the load on foot-path

for purpose of designing the main girders should be taken as 2.0 kN/m2.

Impact load

Fig :Impact percentage curve for highway bridges for IRC class A and

IRC class B loadings

The dynamic effect caused due to vertical oscillation and periodical shifting of the

live load from one wheel to another when the locomotive is moving is known as

impact load. The impact load is determined as a product of impact factor, I, and the

live load. The impact factors are specified by different authorities for different types

of bridges. The impact factors for different bridges for different types of moving loads

are given in the table.

Fig. shows impact percentage curve for highway bridges for class AA loading. Note

that, in the above table l is loaded length in m and B is spacing of main girders in m.

Longitudinal forces – Longitudinal forces are set up between vehicles and

bridge deck when the former accelerate or brake. The magnitude of the force F,

is given by

Where, W – weight of the vehicle

g – Acceleration due to gravity

δV – change in velocity in time d t

This loading is taken to act at a level 1.20 m above the road surface. No increase in

vertical force for dynamic effect should be made along with longitudinal forces. The

possibility of more than one vehicle braking at the same time on a multi-lane bridge

should also be considered.

Thermal forces – The free expansion or contraction of a structure due to changes in

temperature may be restrained by its form of construction. Where any portion of the

structure is not free to expand or contract under the variation of temperature,

allowance should be made for the stresses resulting from this condition. The

coefficient of thermal expansion or contraction for steel is 11.7 x

10-6 / oC

Wind load – Wind load on a bridge may act

· Horizontally, transverse to the direction of span

· Horizontally, along the direction of span

· Vertically upwards, causing uplift

· Wind load on vehicles

Wind load effect is not generally significant in short-span bridges; for medium spans,

the design of sub-structure is affected by wind loading; the super structure design is

affected by wind only in long spans. For the purpose of the design, wind loadings are

adopted from the maps and tables given in IS: 875 (Part III). A wind load of 2.40

kN/m2 is adopted for the unloaded span of the railway, highway and footbridges. In

case of structures with opening the effect of drag around edges of members has to be

considered.

Racking force – This is a lateral force produced due to the lateral movement of rolling

stocks in railway bridges. Lateral bracing of the loaded deck of railway spans shall be

designed to resist, in addition to the wind and centrifugal loads, a lateral load due to

racking force of 6.0 kN/m treated as moving load. This lateral load need not be taken

into account when calculating stresses in chords or flanges of main girders.

Forces on parapets - Railings or parapets shall have a minimum height above the

adjacent roadway or footway surface of 1.0 m less one half the horizontal width of the

top rail or top of the parapet. They shall be designed to resist a lateral horizontal force

and a vertical force each of 1.50 kN/m applied simultaneously at the top of the railing

or parapet.

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. 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.

Forces due to curvature - When a track or traffic lane on a bridge is curved

allowance for centrifugal action of the moving load should be made in designing

the members of the bridge. All the tracks and lanes on the structure being

considered are assumed as occupied by the moving load.

This force is given by the following formula:

Where, C - Centrifugal force in kN/m

W - Equivalent distributed live load in kN/m

V - Maximum speed in km/hour

R - Radius of curvature in m

Erection forces – There are different techniques that are used for construction of

railway bridges, such as launching, pushing, cantilever method, lift and place. In

composite construction the composite action is mobilised only after concrete hardens

and prior to that steel section has to carry dead and construction live loads. Depending

upon the technique adopted the stresses in the members of the bridge structure would

vary. Such erection stresses should be accounted for in design. This may be critical,

especially in the case of erection technologies used in large span bridges.

Load combinations

Stresses for design should be calculated for the most sever combinations of loads and

forces. Four load combinations are generally considered important for checking for

adequacy of the bridge. These are given in below table and are also specified in

IS 1915 - 1961.

7.9 Foundations

Foundations of the bridges have always been a matter of great concern to Civil

Engineers. In many instances actual strata met with at the foundation level turned out to be

quite different than that found at the time of geological and geotechnical investigation. The

experiences of the past serve as a guide for the future.

Spread footings

Spread footings shall be proportioned and designed such that the supporting

soil or rock provides adequate nominal resistance, considering both the potential for adequate

bearing strength and the potential for settlement, under all applicable limit states in

accordance with the provisions of this Section.

Spread footings shall be proportioned and located to maintain stability under

all applicable limit states, considering the potential for, but not necessarily limited to,

overturning (eccentricity), sliding, uplift, overall stability and loss of lateral support.

When sound soil materials exist near the surface, shallow foundations in the form of spread

footings are commonly used. For foundation units situated in a stream, spread footings may

be used when they can be placed on non-erodible rock. Spread footings used as bridge

foundations shall not be supported by embankment fill material including embankments

consisting of mechanically or otherwise stabilized earth systems.

Pile foundations

Piling should be considered when spread footings cannot be founded on rock,

or on competent soils at a reasonable cost. At locations where soil conditions would

normally permit the use of spread footings but the potential exists for scour, liquefaction or

lateral spreading, piles bearing on suitable materials below susceptible soils should be

considered for use as a protection against these problems. Piles should also be considered

where right-of-way or other space limitations would not allow the use of spread footings, or

where removal of existing soil that is contaminated by hazardous materials for construction

of shallow foundations is not desirable. Piles should also be considered where an

unacceptable amount of settlement of spread footings may occur.

The geotechnical engineer is responsible for recommending when driven piles

can be considered, the type of driven pile to be used, the service, strength or extreme event

limit states capacity of the pile. The geotechnical engineer is also responsible for

recommending the estimated pile tip elevation and any special requirements necessary to

drive the piles. When steel piles are used, the corrosive life of the pile should be reported in

the geotechnical report.

Driven piles could be classified as follows:

• Battered Pile: A pile driven at an inclined angle to provide higher resistance to lateral loads.

• Friction Pile: A pile whose support capacity is derived principally from soil resistance

mobilized along the side of the embedded pile.

• Point Bearing Pile: A pile whose support capacity is derived principally from the bearing

resistance of the foundation material on which the pile tip rests.

• Combination Friction and Point Bearing Pile: A pile that derives its capacity from

contribution of both friction resistance mobilized along the embedded pile and point bearing

developed at the pile tip.

7.10 Coffer Dams

A cofferdam is defined as a temporary structure which is constructed so as to

remove water and soil from an area and make it possible to carry on the construction work

under reasonable dry conditions.

Following are the requirements of a cofferdam:

The cofferdam should be reasonably water tight. It may either rest on impervious soil

or may extended to impervious strata through pervious soils.

It should be noted that absolute water tightness is not desired in a cofferdam.

The cofferdam should be designed for the maximum water level and other destructive

forces.

The coffer dams are constructed with advantage where a large area of site is to be

enclosed and hard bed is at reasonable depth

Fig: Example of coffer dam

8. DESIGN DATA

1. Overview

1. Type of crossing = Normal

2 Design Discharge = 1120.37 cum / sec

3. MFL = +100.000 M

4. Sill Level = + 93.500

5. Velocity of flow = 1.408 m/sec

6. Afflux = 0.15

7. Vertical clearance = 1.20 M

8. Silt Factor, Ksf = 2.00

9. Normal Scour depth, dsm = 7.5 m (MFL-Soft rock level)

10. Foundation Levels = Soft rock level -1.5m

For piers = + 91.000 m

For abutments = + 91.000 m

L.W.W and Vents Provided

1. L.W.W required = 80 M

2. Vent Way Provided = 5 Vents of 16.5 m (eff) without footpaths

3. Length of bridge (Back to Back of abutments) = 86.23 m

(5*17.07+6*.03+2*.35= 86.23 m)

Foundation Strata, SBC and Type of foundations adopted:

Soft Rock/SDR is available at a shallow depth of 1.0 m below sill level as per excavation carried at site for piers and abutments. The SBC considered is 25.0 t/m2. Open Foundations are adopted.

Piers

Open foundations in VCC M 15 are provided duly fixing the foundation level with 1.5 m embedment in SDR/Soft Rock

Abutments:

Open foundations in VCC M 15 are provided duly fixing the foundation level with 1.5 m embedment in SDR/Soft Rock

Wing Walls:

Box wings in VCC M 15 are proposed.

Foundation Levels and strata of resting:-

All the Piers = (+) 91.000 (resting in SDR/SR)

Abutments A1, A2 = (+) 91.000 (resting in SDR/SR)

Substructure:-

Abutments: Wall type abutments in VCC M 15 mix with skin reinforcement.

Piers: Wall type piers in VCC M 15 mix with skin reinforcement.

Wingwalls: Box wings in VCC M 15 mix with skin reinforcement.

R.C.L Calculations:-

MFL = + 100.0

V.C = 1.2

Afflux = 0.15

Deck Th. = 1.675

Wearing coat = 0.100 +103.125 M

Bearings:- Neoprene Rubber bearings of size 630X220X061 mm.

Type of Superstructure and Drawings adopted) :

RCC T beam girder and RCC slabs of 16.5 m (eff) span , without footpaths are provided as per MOST BD drawing Nos. BD / 13-76,14-76A,15-76A.

Expansion Joints :- Single Strip Seal Expansion Joints of standard make

Wearing Coat :- As per BD drawing No. BD / 1- 69 A in VRCC M 30. Thickness = 100mm at center and 50mm at edges Approach Slabs

:- As per CE drawing No. 4- 71 in VRCC M30

Length = 4.0m, Width = 7.5m, Thickness =0.30m

Hand Rails: As per drawing no. BD / 5-69 , type II in RCC M20

Data adopted from Standard Superstructure drawings for Design Purpose

Drawing Nos. referred (without footpaths)

a. BD/13-76b. BD/14-76A

c. BD/15-76A

Dead Load :

@ Pier = 174 T @ Abutment = 87 T

Live Load :

LL = (DL+LL) - DL

@ Pier = 82.25 T @ Abutment = 70.0 T

Concrete Quantity / Span: 61.2 cum

Steel Quantity / Span

(ii)Reinforcing steel: 10.373 T

(Including 5 % extra for wastage and laps)

8.1 Design Procedure adopted

Substructure including foundations :

Abutments and their foundations: Abutment: Wall type in VCC M 15 concrete with open foundations is designed as per IRC codes for 2 lanes.

Piers and their foundations : pier: Wall type in VCC M15 with open foundations is designed as per IRC codes for 2 lanes.

Wing walls and their foundation: Box wing wall in VCC M15 with open foundations as per IRC codes.

Bed blocks over abutments and piers: Computer MS EXCEL program is used for design of Bed block over abutment.

Backing walls: Computer MS EXCEL program is used for design of backing wall over abutment.

8.2 Live Load eccentricity calculations

(As per BD drawings of MORTH)

Transverse:-

(7.5/2) - ( 1.2 + (2.79/2) )

= 1.155m

Longitudinal: .285+.015

= .3 m

9. CALCULATIONS

9.1 Calculation of Discharge

AS PER CA MAP SEPERATELY DRAWN

Area = 325.000 Sqkm approximate.

Calculation of Discharge by Catchment Area Method

Q = c x M 3/4

where Q = Discharge in cumecs

c = Constant = 14

M = Catchment Area in Sqkm = 325.000

Q = 14 x 325 3/4 = 1071.62 Cumecs

Reduced level at 150.000 m Upstream = 93.259 m

Reduced level at 100.000 m Downstream = 92.983 m

Total Distance = 250.000 m

Slope = ( 93.259 - 92.983 ) = 0.00100

Catchment Area Calculations

Calculation of Bed Slope

250.00

Calculation of Discharge by Area Velocity Method :

Cross section @ Site of crossing MFL = + 100.000 m

HFL G.L Depth of Flow Distance Mean Depth Area Perimeter

100.000 100.000 0.000 0.000 0.000 0.000 0.000

100.000 98.981 1.019 10.000 0.510 5.095 10.052

100.000 98.295 1.705 10.000 1.362 13.620 10.024

100.000 97.983 2.017 10.000 1.861 18.610 10.005

100.000 97.929 2.071 10.000 2.044 20.440 10.000

100.000 97.952 2.048 10.000 2.060 20.595 10.000

100.000 98.055 1.945 10.000 1.997 19.965 10.001

100.000 98.183 1.817 10.000 1.881 18.810 10.001

100.000 98.337 1.663 10.000 1.740 17.400 10.001

100.000 98.411 1.589 10.000 1.626 16.260 10.000

100.000 98.428 1.572 10.000 1.581 15.805 10.000

100.000 98.389 1.611 10.000 1.592 15.915 10.000

100.000 98.350 1.650 10.000 1.631 16.305 10.000

100.000 98.054 1.946 10.000 1.798 17.980 10.004

100.000 97.538 2.462 10.000 2.204 22.040 10.013

100.000 96.909 3.091 10.000 2.777 27.765 10.020

100.000 96.388 3.612 10.000 3.351 33.515 10.014

100.000 95.101 4.899 10.000 4.256 42.555 10.082

100.000 94.227 5.773 10.000 5.336 53.360 10.038

100.000 93.295 6.705 10.000 6.239 62.390 10.043

100.000 93.351 6.649 10.000 6.677 66.770 10.000

100.000 94.116 5.884 10.000 6.267 62.665 10.029

100.000 94.837 5.163 10.000 5.524 55.235 10.026

100.000 95.683 4.317 10.000 4.740 47.400 10.036

100.000 96.541 3.459 10.000 3.888 38.880 10.037

100.000 97.453 2.547 10.000 3.003 30.030 10.042

100.000 98.365 1.635 10.000 2.091 20.910 10.042

100.000 99.277 0.723 10.000 1.179 11.790 10.042

100.000 100.000 0.000 10.000 0.361 3.615 10.026

795.720 280.577

Mean Radius, R = A / P = 795.720 = 2.836 m280.577

Slope of drain bed, S = 0.0010

Rugosity Coefficient, n = 0.045

Velocity V = 1 / n x R 2/3 x S 1/2 = 1.408 m / sec`

Discharge, Q = A * V = 1120.374 Cumecs

Cross section at 100m Upstream MFL = + 100.100 m

HFL G.L Depth of Flow Distance Mean Depth Area Perimeter

100.100 100.100 0.000 0.000 0.000 0.000 0.000

100.100 98.361 1.739 100.000 0.869 86.950 100.015

100.100 97.909 2.191 5.000 1.965 9.825 5.020

100.100 96.478 3.622 5.000 2.906 14.533 5.201

100.100 94.345 5.755 5.000 4.689 23.443 5.436

100.100 93.276 6.824 5.000 6.290 31.448 5.113

100.100 94.325 5.775 5.000 6.299 31.498 5.109

100.100 95.444 4.656 5.000 5.215 26.078 5.124

100.100 97.926 2.174 5.000 3.415 17.075 5.582

100.100 98.427 1.673 5.000 1.923 9.617 5.025

100.100 100.100 0.000 100.000 0.836 83.650 100.014

334.115 241.639

Mean Radius, R = A / P = 334.115 1.383 m241.639

Slope of drain bed, S = 0.0010

Rugosity Coefficient, n = 0.045

Velocity V = 1 / n x R 2/3 x S 1/2 = 0.872 m / sec

Discharge, Q = A * V = 291.348 Cumecs

Cross section at 100m Downstream MFL = +99.900 m

HFL G.L Depth of Flow Distance Mean Depth Area Perimeter

99.900 99.900 0.000 0.000 0.000 0.000 0.000

99.900 96.985 2.915 100.000 1.458 145.750 100.042

99.900 95.235 4.665 5.000 3.790 18.950 5.297

99.900 94.866 5.034 5.000 4.850 24.248 5.014

99.900 93.434 6.466 5.000 5.750 28.750 5.201

99.900 92.983 6.917 5.000 6.692 33.458 5.020

99.900 93.399 6.501 5.000 6.709 33.545 5.017

99.900 94.883 5.017 5.000 5.759 28.795 5.216

99.900 95.323 4.577 5.000 4.797 23.985 5.019

99.900 97.015 2.885 5.000 4.676 23.378 6.150

99.900 98.960 0.940 5.000 1.913 9.563 5.365

99.900 99.900 0.000 100.000 0.470 47.000 100.004

417.420 247.346

Mean Radius, R = A / P = 417.420 = 1.688 m247.346

Slope of drain bed, S = 0.0010

Rugosity Coefficient, n = 0.045

Velocity V = 1 / n x R 2/3 x S 1/2 = 0.996 m / sec

Discharge, Q = A * V = 415.750 Cumecs

S.No HFL (m) Discharge

1 100.100 291.348 Cumecs

2 100.000 1120.374 Cumecs

3 99.900 415.750 Cumecs

SUMMARY OF DISCHARGE

Location

100m U/ S

Site of crossing

100 m D/S

The Discharge obtained from Area velocity method at upstream, site of crossing

and downstream are mentioned above.

The Discharge obtained from Catchment area is = 1071.62 Cumecs.

Hence, the design dishcarge is considered as = 1120.37 Cumecs

Design Discharge

9.2 Calculation of Linear Waterway

Discharge Q = 1120.374 Cumecs

HFL = 100.000 m

Sill level = 93.500

Velocity of flow = 1.408 m / Sec

Depth of flow d = 100 - 93.5 = 6.500 m

Afflux (x)= 0.15 m ( Assumed)

Head due to Afflux ha = V2 d2] / [(d+x)2 * 2 * 9.81]

= ( 1.408 ^ 2 ) x ( 6.5 ^ 2 ) ( 6.5 + 0.15 ) ^ 2 x ( 2 x 9.81 )

= 0.097 m

Combined Head (ha + x) = 0.15+ 0.097 = 0.247

Velocity through vents Vv = 0.9 v [2*g*(ha+x)]

= 0.9 x SQRT { 2 x 9.81 x ( 0.247 ) }

= 1.981 m / Sec

Linear Water Way = Q / (Vv * d) = 1120.374 = 87.009 m

( 1.981 x 6.5 )

Skew Angle is = 0 o

Linear water way in skew is = 87.009 SAY 87.000 m

PROVIDE LWW = 80 as per site condition

9.3 Calculation of Scour Depth

Normal Scour Depth

HFL = 100.000 m

Sill level = 93.500

Db = Q / L = 1120.37 = 12.878 m80.00

dsm = 1.34 * (Db2 / ksf)1/3

Silt factor ksf = 2.00

dsm = 1.34 x ( 12.878 ^ 2 / 2 )1/3 = 5.835 m

Normal Scour Depth = dsm = 5.835 m below HFL

Pier

Max Scour Depth = 2.0xdsm = 11.670 m

Grip length = ( 1 / 3 ) x 11.67 = 3.890 m

Max Scour Depth including grip length = 11.67 + 3.89 = 15.560 m

Foundation Level =HFL - Max Scour Depth including grip length

= 100 - 15.56 = 84.440 m

Say 84.400 m

Depth below sill level= Sill level - Foundation Level

= 93.5 - 84.4 = 9.100 m

ABUTMENT

Max Scour Depth = 1.27xdsm= 7.410 m

Grip length = ( 1 / 3 ) x 7.41 = 2.470 m

Max Scour Depth including grip length = 7.41 + 2.47 = 9.880 m

Foundation level =HFL - Max Scour Depth including grip length

= 100 - 9.88 = 90.120 mSay 90.100 m

Depth below sill level= Sill level - Foundation Level

= 93.5 - 90.1 = 3.400 m

Soft Rock is availble at shallow depth of 1.0m below sill

Propose OPEN FOUNDATION with 1.5 m embedment in soft rock

FOUNDATION LEVEL =93.5 - 2.5 = 91.000 m

9.4 Span Arrangement

Linear Water way requried in normal direction = 80.000 m

Economical span = 1.5 ( HFL + 1.2 + 0.15 - 91 )

= 1.5 ( 100 + 1.2 + 0.15 - 91 )

= 15.525 m

Provide 5 Vents of 16.5 m (eff.) with Open foundation

HFL = 100.000 m

Vertical Clearance = 1.200 m

Afflux = 0.15 m

Deck slab thickness = 1.675 m

Bottom of Deck = HFL + AFFLUX + VC

= ( 100 + 1.2 + 0.15 ) = 101.350 m

RCL = Bottom of Deck + Deck thickness + wearing coat

= ( 101.35 + 1.675 + 0.100 ) = 103.125 m

FIXING OF RCL

9.5 Salient Features

1) Design Discharge, Q = 1120.37 Cumecs

2) HFL = 100.000 m

3) Velocity = 1.408 m/sec

4) Sill Level = 93.500 m

5) Carriage way width = 7.50 m

6) Span arrangement = 5 vents of 16.5 m ( eff )without footpath

7) RCL = 103.125 m

8) Bottom of Deck = 101.350 m

9) Type of Sub Strcuture

Pier = VCC M15 WALL TYPE with skin rft

Abutment = VCC M15 Wall Type with skin rft

Return Wall = VCC M15 BOX Type with skin rft

10) Type of Foundation = Open foundation for Piers, Abutments and wingwalls

11) Foundation Levels

Pier = 91.000 m SR-1.5m

Abutment = 91.000 m SR-1.5m

Return wall = 94.500 m GL-3.0m

10. INITIAL PREPARATION

10.1 Removal of structures and obstructions

This work consists of salvaging, removing, and disposing of buildings, fences, structures,

pavements, culverts, utilities, curbs, sidewalks, and other obstructions.

Material

Conform to the following Section and Subsection:

Backfill material

Concrete

Construction Requirements

Salvaging Material. Salvage, with reasonable care, all material designated to be salvaged.

Salvage in readily transportable sections or pieces. Replace or repair all members, pins, nuts,

plates, and related hardware damaged, lost, or destroyed during the salvage operation. Wire

all loose parts to adjacent members or pack them in sturdy boxes with the contents clearly

marked. Match mark members of salvaged structures. Furnish one set of drawings identifying

the members and their respective match marks.

Stockpile salvaged material at a designated area on the project.

Removing Material. Saw cut sidewalks, curbs, pavements, and structures when

partial removal is required.

Construct structurally adequate debris shields to contain debris within the construction

limits. Do not permit debris to enter waterways, travel lanes open to public traffic, or areas

designated not to be disturbed. Raze and remove all buildings, foundations, pavements,

sidewalks, curbs, fences, structures, and other obstructions interfering with the work and not

designated to remain. Where part of an existing culvert is removed, remove the entire culvert

upstream from the removal. The remaining downstream culvert may be left in place if no

portion of the culvert is within 4 feet of the subgrade, embankment slope, or new culvert or

structure; and the culvert ends are sealed with concrete. Remove structures and obstructions

in the roadbed to 3 feet below subgrade elevation. Remove structures and obstructions

outside the roadbed to 2 feet below finished ground or to the natural stream bottom. Abandon

existing manholes, inlets, catch basins, and spring boxes Except in excavation areas, backfill

and compact cavities left by structure removal with backfill material to the level of the

finished ground. Backfill excavated areas . Compact backfill

Disposing of Material. Dispose of debris and unsuitable and excess material as

follows:

(a) Remove from project. Recycle or dispose of material legally off the project.

Furnish a statement documenting the nature and quantity of material processed or sold

for recycling. Otherwise, furnish a signed copy of the disposal agreement before

disposal begins.

(b) Burn. Obtain necessary burning permits. Furnish a copy of the burning permits

before burning begins.

Burn using high intensity burning processes that produce few emissions. Examples

include incinerators, high stacking, or pit and ditch burning with forced air supplements.

Provide a competent watchperson during the burning operations.

When burning is complete, extinguish the fire so no smoldering debris remains.

Dispose of unburned material according to (a) above.

(c) Bury. Bury debris in trenches or pits in approved areas within the right-of-way.Do not

bury debris inside the roadway prism limits, beneath drainage ditches, or inany areas subject

to free-flowing water. Place debris in alternating layers of 4 feet of debris covered with 2 feet

of earth material. Distribute stumps, logs, and other large pieces to form a dense mass and

minimize air voids. Cover the top layer of buried debris with at least 1 foot of compacted

earth. Grade and shape the area. Seed and mulch disposal areas on Government property

(d) Hazardous material. Furnish a copy of all disposal permits. Dispose of material

according to Federal, State, and local regulations

Acceptance. Removal of structures and obstructions will be evaluated under Backfilling and

compacting cavities left by structures will be evaluated Concrete will be evaluated.

Measurement

Measure the items listed in the bid schedule

Payment

The accepted quantities will be paid at the contract price per unit of measurement

for pay items listed in the bid schedule. Payment will be full

compensation for the work prescribed

10.2 Excavation and Embankment

This work consists of excavating material and constructing embankments. This

includes furnishing, hauling, stockpiling, placing, disposing, sloping, shaping, compacting,

and finishing earthen and rocky material.

Definitions:-

(a) Excavation. Excavation consists of the following:

(1) Roadway excavation. All material excavated from within the right-of-way

or easement areas, except subexcavation covered in (2) below and structure

excavation Roadway excavation includes all

material encountered regardless of its nature or characteristics.

(2) Subexcavation. Material excavated from below subgrade elevation in cut

sections or from below the original groundline in embankment sections.

Subexcavation does not include the work required by,

(3) Borrow excavation. Material used for embankment construction that is

obtained from outside the roadway prism. Borrow excavation includes

unclassified borrow, select borrow, and select topping.

(b) Embankment construction. Embankment construction consists of placing and

compacting roadway or borrow excavation. This work includes:

(1) Preparing foundation for embankment;

(2) Constructing roadway embankments;

(3) Benching for side-hill embankments;

(4) Constructing dikes, ramps, mounds, and berms; and

(5) Backfilling subexcavated areas, holes, pits, and other depressions.

(c) Conserved topsoil. Excavated material conserved from the roadway excavation

and embankment foundation areas that is suitable for growth of grass, cover crops, or

native vegetation.

Material

Conform to the following Subsections:

Backfill material

Select borrow

Select topping

Topping

Unclassified borrow

Water

Construction Requirements:

Preparation for Roadway Excavation and Embankment Construction.

Clear the area of vegetation and obstructions according to Sections Conserved Topsoil.

Conserve topsoil from roadway excavation and embankment foundation areas. Stockpile

conserved topsoil in low windrows immediately beyond the rounding limits of cut and

embankment slopes or in other approved locations. Separate topsoil from other excavated

material. Place conserved topsoil on completed slopes.

Roadway Excavation.

(a) General. Do not disturb material and vegetation outside the construction limits.

Incorporate only suitable material into embankments. Replace any shortage of suitable

material caused by premature disposal of roadway excavation. Dispose of

unsuitable or excess excavation material

At the end of each day's operations, shape to drain and compact the work area to a

uniform cross-section. Eliminate all ruts and low spots that could hold water.

(b) Rock cuts. Blast rock Excavate rock cuts to 6 inches

below subgrade within the roadbed limits. Backfill to subgrade with topping or with

other suitable material. Compact the material .

(c) Earth cuts. Scarify earth cuts to 6 inches below subgrade within the roadbed

limits. Compact the scarified material according to Subsection

Subexcavation. Excavate material to the limits designated by the CO. Take cross-sections .

Prevent unsuitable material from becoming mixed with the backfill. Dispose of unsuitable

material according to Subsection Backfill the subexcavation with topping, or other suitable

material. Compact the material.

Borrow Excavation. Use all suitable roadway excavation in embankment construction. Do

not use borrow excavation when it results in excess roadway excavation. Deduct excess

borrow excavation from the appropriate borrow excavation quantity. Obtain borrow source

acceptance. Develop and restore borrow sources Do not excavate beyond the established

limits. When applicable, shape the borrow source to permit accurate measurements when

excavation is complete.

Preparing Foundation for Embankment Construction. Prepare foundation for

embankment construction as follows:

(a) Embankment less than 4 feet high over natural ground. Remove topsoil and

break up the ground surface to a minimum depth of 6 inches by plowing or scarifying.

Compact the ground surface

(b) Embankments over an existing asphalt, concrete, or gravel road surface.

Scarify gravel roads to a minimum depth of 6 inches. Scarify or pulverize asphalt and

concrete roads to 6 inches below the pavement. Reduce all particles to a maximum size of 6

inches and produce a uniform material. Compact the surface.

(c) Embankment across ground not capable of supporting equipment. Dump

successive loads of embankment material in a uniformly distributed layer to construct

the lower portion of the embankment. Limit the layer thickness to the minimum depth

necessary to support the equipment.

(d) Embankment on an existing slope steeper than 1V:3H. Cut horizontal benches

in the existing slope to a sufficient width to accommodate placement and compaction

operations and equipment. Bench the slope as the embankment is placed and compacted in

layers. Begin each bench at the intersection of the original ground and

the vertical cut of the previous bench. Embankment Construction. Incorporate only suitable

roadway excavation material into the embankment. When the supply of suitable roadway

excavation is exhausted, furnish unclassified borrow to complete the embankment. Construct

embankments as follows:

(a) General. At the end of each day's operations, shape to drain and compact the

embankment surface to a uniform cross-section. Eliminate all ruts and low spots that

could hold water

During all stages of construction, route and distribute hauling and

leveling equipment over the width and length of each layer of material. Compact

embankment side slopes with a tamping foot roller, by walking with a dozer, or by over-

building the fill and then removing excess material to the final slope line. For slopes 1V:1¾H

or steeper, compact the slopes as embankment construction progresses. Where placing

embankment on one side of abutments, wing walls, piers, or culvert headwalls, compact the

material using methods that prevent excessive pressure against the structure. Where placing

embankment material on both sides of a concrete wall or box structure, conduct operations so

compacted embankment material is at the same elevation on both sides of the structure.

Where structural pilings are placed in embankment locations, limit the maximum particle size

to 4 inches.

(b) Embankment within the roadway prism.

Place embankment material in horizontal layers not exceeding 12

inches in compacted thickness. Incorporate oversize boulders or rock fragments into the 12-

inch layers by reducing them in size or placing them individually as required by (c) below.

Compact each layer before placing the next layer.

Material composed predominately of boulders or rock fragments too

large for 12-inchlayers may be placed in layers up to 24 inches thick. Incorporate oversize

boulders or rock fragments into the 24-inch layer by reducing them in size or placing them

individually according to (c) below. Place sufficient earth and smaller rocks to fill the voids.

Compact each layer before placing the next layer.

(c) Individual rock fragments and boulders.

Place individual rock fragments and boulders greater than 24 inches in

diameter as follows:

(1) Reduce rock to less than 48 inches in the largest dimension.

(2) Distribute rock within the embankment to prevent nesting.

(3) Place layers of embankment material around each rock to a depth not

greater than that permitted by (b) above. Fill all the voids between rocks.

(4) Compact each layer before placing the next

layer.

(d) Embankment outside of roadway prism. Where placing embankment outside

the staked roadway prism, place material in horizontal layers not exceeding 24 inches

in compacted thickness. Compact each layer

Compaction

For the purpose of compaction, use AASHTO T 27 to determine the amount of

material retained on a No. 4 sieve. Compact as follows:

(a) More than 80 percent retained on a No. 4 sieve. Adjust the moisture content to a level

suitable for compaction. Fill the interstices around rock with earth or other fine material as

practical. Use compression-type rollers at speeds less than 6 feet per second and vibratory

rollers at speeds less than 3 feet per second. Compact each layer

of material full width with one of the following and until there is no visible evidence of

further consolidation.

(1) Four roller passes of a vibratory roller having a minimum dynamic force of

40,000 pounds impact per vibration and a minimum frequency of 1000

vibrations per minute.

(2) Eight roller passes of a 20-ton compression-type roller.

(3) Eight roller passes of a vibratory roller having a minimum dynamic force of

30,000 pounds impact per vibration and a minimum frequency of 1000

vibrations per minute.

Increase the compactive effort for layers deeper than 12 inches as follows:

• For each additional 6 inches or fraction thereof, increase the number of

roller passes in (1) above by four passes.

• For each additional 6 inches or fraction thereof, increase the number of

roller passes in (2) and (3) above, by eight passes.

(b) 50 to 80 percent retained on a No. 4 sieve. Use AASHTO T 99 to determine the

optimum moisture content of the portion of the material passing a No. 4 sieve. Multiply this

number by the percentage of material passing a No. 4 sieve, and add 2percent to determine

the optimum moisture content of the material. Adjust the moisture content of material

classified A-1 through A-5 to a moisture content suitable for compaction. Adjust the moisture

content of material classified A-6 and A-7 to within 2 percent of the optimum moisture

content. Use compression-type rollers at speeds less than 6 feet per second and vibratory

rollers at speeds less than 3 feet per second. Compact each layer of material full width

according to (a) above.

(c) Less than 50 percent retained on a No. 4 sieve. Classify the material according to

AASHTO M 145. For material classified A-1 or A-2-4, determine the maximum density

according to AASHTO T 180, method D. For other material classifications, determine the

optimum moisture content and maximum density according to AASHTO T 99, method C.

.

Ditches. Slope, grade, and shape ditches. Remove all projecting roots, stumps, rock, or

similar matter. Maintain all ditches in an open condition and free from leaves, sticks, and

other debris. Form furrow ditches by plowing or using other acceptable methods to produce a

continuous furrow. Place all excavated material on the downhill side so the bottom of the

ditch is approximately 18 inches below the crest of the loose material. Clean the ditch using a

hand shovel, ditcher, or other suitable method. Shape to provide drainage without overflow.

Sloping, Shaping, and Finishing. Complete slopes, ditches, culverts, riprap, and other

underground minor structures before placing aggregate courses. Slope, shape, and finish as

follows:

(a) Sloping. Leave all earth slopes with uniform roughened surfaces, except as

described in (b) below, with no noticeable break as viewed from the road. Except in

solid rock, round tops and bottoms of all slopes including the slopes of drainage

ditches. Round material overlaying solid rock to the extent practical. Scale all rock

slopes.

(b) Stepped slopes. Where required by the contract, construct steps on slopes of

1⅓V:1H to 1V:2H. Construct the steps approximately 18 inches high. Blend the steps into

natural ground at the end of the cut. If the slope contains nonrippable rockout crops, blend

steps into the rock. Remove loose material found in transitional area.

Except for removing large rocks that may fall, scaling stepped slopes is not required.

(c) Shaping. Shape the subgrade to a smooth surface and to the cross-section required.

Shape slopes to gradually transition into slope adjustments without noticeable breaks. At the

ends of cuts and at intersections of cuts and embankments, adjust slopes in the horizontal and

vertical planes to blend into each other or into the

natural ground.

(d) Finishing. Remove all material larger than 6 inches from the top 6 inches of the

roadbed. Remove unsuitable material from the roadbed, and replace it with suitable

material. Finish roadbeds that are compacted according to Subsection 204.11(b) and

(c) to within ±0.05 feet of the staked line and grade. Finish roadbeds that are

compacted according to Subsection 204.11(a) to within ±0.10 feet of the staked line and

grade. Finish ditch cross-sections to within ±0.10 feet of the staked line and grade. Maintain

proper ditch drainage.

Disposal of Unsuitable or Excess Material.

Dispose of unsuitable or excess material legally off the project. When there is a

pay item for waste, shape and compact the waste material in its final location. Do not mix

clearing or other material not subject to payment with the waste material. Material for

embankment and conserved topsoil will be evaluated. Excavation and embankment

construction will be evaluated under Clearing and removal of obstructions will be evaluated

Placing of conserved topsoil will be evaluated

Measurement

Measure the Section items listed in the bid schedule and the following as

applicable.

(a) Roadway excavation. Measure roadway excavation in its original position as

follows:

(1) Include the following volumes in roadway excavation:

(a) Roadway prism excavation;

(b) Rock material excavated and removed from below subgrade in cut sections;

(c) Unsuitable material below subgrade and unsuitable material beneath embankment areas

when a pay item for subexcavation is not shown in the bid schedule;

(d) Ditches, except furrow ditches measured under a separate bid item;

(e) Conserved topsoil;

(f) Borrow material used in the work when a pay item for borrow is not shown in the bid

schedule;

(g) Loose scattered rocks removed and placed as required within the roadway;

(h) Conserved material taken from stockpiles and used in Section 204 work

except topsoil measured under Section 624; and

(i) Slide and slipout material not attributable to the Contractor's method of

operation.

(2) Do not include the following in roadway excavation:

(a) Overburden and other spoil material from borrow sources;

(b) Over breakage from the back slope in rock excavation;

(c) Water or other liquid material;

(d) Material used for purposes other than required;

(e) Roadbed material scarified in place and not removed;

(f) Material excavated when stepping cut slopes;

(g) Material excavated when rounding cut slopes;

(h) Preparing foundations for embankment construction;

(i) Material excavated when benching for embankments;

(j) Slide or slip out material attributable to the Contractor's method of operation;

(k) Conserved material taken from stockpiles constructed at the option of the Contractor

(3) When both roadway excavation and embankment construction pay items are shown in the

bid schedule, measure roadway excavation only for the following:

(a) Unsuitable material below sub grade in cuts and unsuitable material beneath embankment

areas when a pay item for sub excavation is not shown in the bid schedule;

(b) Slide and slip out material not attributable to the Contractor’s method of operations; and

(c) Drainage ditches, channel changes, and diversion ditches.

(b) Unclassified borrow, select borrow, and select topping. When measuring by the cubic

yard measure in its original position. If borrow excavation is measured by the cubic yard in

place, take initial cross-sections of the ground surface after stripping overburden. Upon

completion of excavation and after the borrow source waste material is returned to the source,

retake cross-sections before replacing the overburden. Do not measure borrow excavation

used in place of excess roadway excavation.

(c) Embankment construction. Measure embankment construction in its final position. Do

not make deductions from the embankment construction quantity for the volume of minor

structures.

(1) Include the following volumes in embankment construction:

(a) Roadway embankments;

(b) Material used to backfill sub excavated areas, holes, pits, and other depressions;

(c) Material used to restore obliterated roadbeds to original contours; and

(d) Material used for dikes, ramps, mounds, and berms.

(2) Do not include the following in embankment construction:

(a) Preparing foundations for embankment construction;

(b) Adjustments for subsidence or settlement of the embankment or of the

foundation on which the embankment is placed; and

(c) Material used to round fill slopes.

(d) Rounding cut slopes. Measure rounding cut slopes horizontally along the

centerline of the roadway.

(e) Waste. Measure waste by the cubic yard in its final position. Take initial crosssections

of the ground surface after stripping over burden. Upon completion of the waste placement,

retake cross-sections before replacing overburden.

(f) Slope scaling. Measure slope scaling by the cubic yard in the hauling vehicle.

Payment

The accepted quantities will be paid at the contract price per unit of measurement for the

Section pay items listed in the bid schedule. Payment will be full compensation for the work

prescribed in this Section.

10.3 Rock Blasting

This work consists of fracturing rock and constructing stable final rock cut faces using

controlled blasting and production blasting techniques. Controlled blasting uses explosives to

form a shear plane in the rock along a specified backslope. Controlled blasting includes

presplitting and cushion blasting. Production blasting uses explosives to fracture rock.

Material:

Conform to the following Subsection:

Explosives and blasting accessories

Construction Requirements

Regulations. Furnish copies or other proof of all-applicable permits and licenses. Comply

with Federal, State, and local regulations on the purchase, transportation, storage,

and use of explosive material. Federal regulations include the following:

(a) Safety and health. OSHA, 29 CFR Part 1926, Subpart U.

(b) Storage, security, and accountability. Bureau of Alcohol, Tobacco, and

Firearms (BATF), 27 CFR Part 181.

(c) Shipment. DOT, 49 CFR Parts 171-179, 390-397.

(d) National Park Service regulations. For projects in National Parks, also comply

with NPS Director’s Order #65, Explosives Use and Blasting Safety.

Blaster-in-Charge. Designate in writing a blaster-in-charge. Submit evidence that the

blaster-in-charge has a valid State blaster’s license or other license accepted by the State

where the project is located and issued by an equivalent licensing body for the type of

blasting required.

Blasting Plans. Blasting plans are for quality control and record keeping purposes and are to

be signed by the blaster-in-charge. The review and acceptance of blasting plans does not

relieve the Contractor of the responsibility for using existing drilling and blasting technology,

and for obtaining the required results. Do not deliver explosives to the project until the

general blasting plan is accepted.

(a) General blasting plan. Submit a general blasting plan for acceptance at least 14 days

before drilling operations begin. Include, as a minimum, the following safety and procedural

details:

(1) Working procedures and safety precautions for storing, transporting, handling, and

detonating explosives.

(2) Proposed product selection for both dry and wet holes. Furnish Manufacturer’s Material

Safety Data Sheets for all explosives, primers, initiators, and other blasting devices.

(3) Typical plan and section views for both production and controlled blasting, including

maximum length of the shot, burden, hole spacing, hole inclination, hole depth, hole

diameter, subdrill depth, and powder factor.

(4) Proposed initiation and delay methods and delay times.

(5) Proposed format for providing all the required information for the site specific blasting

plans.

(b) Site-specific blasting plans. After the general blasting plan is accepted, submit site-

specific blasting plans for acceptance before drilling operations begin. Allow upto three days

for review of these plans. Include the following information in the site specific blasting plan.

(1) Site drawings showing a scaled map of the blast area and cross-sectional views which

indicate beginning and ending stations, free face location, hole spacing, hole diameter, hole

depth, burden, hole inclination, and sub drill depth. Include on the drawings any significant

joints or bedding planes within the blast zone and incorporate this geology into the blast

design.

(2) Where blasting may affect nearby structures or utilities, provide method of monitoring

and controlling blast vibrations

(3) Loading pattern diagram showing the location and amount of each type of explosive to be

used in the holes including primer and initiators and the location, type, and depth of

stemming, column heights, and overall powder factor for each type of loading.

(4) Delay and initiation diagram showing delay pattern, sequence, and delay

times.

205.06 Preblast condition survey and vibration monitoring and control.

When blasting near buildings, structures, or utilities that may be subject

to damage from ground or airblast vibrations, provide a blast vibration specialist. Provide a

specialist with at least 5 consecutive years experience in vibration monitoring for at least 3

projects. Fourteen days before blasting, submit the name and qualifications of the blast

vibration specialist including the following:

(a) Project names, locations, and services performed.

(b) Name and phone number of owner/agency contact who can verify the experience of the

specialist. Before blasting, arrange for a preblast condition survey of nearby buildings,

structures, or utilities, which could be at risk from blasting damage. Use a survey method

acceptable to the Contractor’s insurance company. Damage resulting from blasting is the

Contractor’s responsibility. Make all preblast condition survey records available to the CO.

Notify the CO and occupants of nearby buildings at least 24 hours before blasting. Control

vibrations with properly designed delay sequences and allowable charge weights per delay

when blasting near buildings, structures, or utilities that may be subject to damage from blast-

induced vibrations. Base allowable charge weights per delay by carrying out trial blasts and

measuring vibration levels.

.

Test Blasting. Drill, blast, and excavate one or more test sections as proposed in

the blasting plan before full-scale drilling and blasting. Test blasts may be made away from

or at the final slope line. Space blast holes for the cushion (trim) method of controlled

blasting no more than 60 inches apart for the initial test blast. Space blast holes for the

presplitting method of controlled blasting no more than 30 inches apart for the initial test

blast.

Blasting:

(a) General. Drill and blast according to the blasting plan. Before drilling, remove

overburden soil and loose rock along the top of the excavation for at least 30 feet beyond the

hole drilling limits or to the end of the cut. Cap all holes to prevent unwanted backfill. Place a

stake next to each hole with hole number and total depth drilled. Use the types of explosives

and blasting accessories necessary to obtain the required results. A bottom charge may be

larger than the line charges if no overbreak results. Free blast holes of obstructions for their

entire depth. Place charges without caving the blast hole walls. Stem the upper portion of all

blast holes with dry sand or other granular material passing the 3/8-inch sieve. Repair or

stabilization may include removal, rock bolting, rock dowels, or other stabilization

techniques. Halt blasting operations when any of the following occur and perform additional

test blast:

(1) Slopes are unstable;

(2) Slopes exceed tolerances or overhangs are created;

(3) Backslope damage occurs;

(4) Safety of the public is jeopardized;

(5) Property or natural features are endangered;

(6) Fly rock is generated; or

(7) Excessive ground or air blast vibrations occur in an area where damage to

buildings, structures, or utilities is possible.

(b) Drill logs. Submit drill logs. Include the following:

(1) Blast plan map showing designated hole numbers; and

(2) Individual hole logs completed and signed by the driller that show total depth drilled,

depths and descriptions of significant conditions encountered during drilling that may affect

loading such as water or voids, and date drilled.

(c) Controlled blasting.

When test blasts indicate the need for controlled blasting, use controlled

blasting methods to form the final rock cut faces when the rock height is more than 10 feet

above ditch grade and the staked slope is 2V:1H or steeper. Controlled blasting includes only

those holes drilled on the row furthest from the free face and that are drilled on the design

slope. Use downhole angle or fan drill blast holes for pioneering the tops of rock cuts or

preparing a working platform for controlled blasting. Use the blast hole diameter and hole

spacing established for controlled blasting during the test blasts. Drill controlled blast holes

not greater than 4 inches in diameter along the final rock face line. Drill controlled blast holes

within 3 inches of the proposed surface location. Drill controlled blast holes at least 30 feet

beyond the production holes to be detonated or to the end of the cut.

Use drilling equipment with mechanical or electrical-mechanical devices that

accurately control the angle the drill enters the rock. Select a lift height and conduct drilling

operations so the blast hole spacing and downhole alignment does not vary more than 9

inches from the proposed spacing and alignment. When more than 5 percent of the holes

exceed the variance, reduce the lift height and modify the drilling operations until the blast

holes are within the allowable variance after blasting the nearest production row.

(d) Production blasting. Drill the row of production blast holes closest to the controlled

blast line parallel and no closer than 6 feet to the controlled blast line. Do not drill production

blast holes lower than the bottom of the controlled blast holes. Detonate production holes on

a delay sequence toward a free face.

After Blast Reports.

Within 3 days after a blast and before the next blast, submit an after-blast report

that includes the following:

(a) Results of the blast and whether or not blasting objectives were met. If blasting objectives

were not met, submit proposed changes to future site-specific blasting plans that will produce

acceptable results and proposed repair or stabilization plan for unstable or blast damaged

backslopes.

(b) Blasting logs that include the following:

(1) All actual dimensions of the shot including blast hole depths, hole diameter, burden,

spacing, subdrilling, stemming, powder loads, and timing; and

(2) A drawing or sketch showing the direction of the face, or faces, and the physical shot

layout.

(c) If a seismograph was used, provide the following:

(1) Identification of instrument used;

(2) Name of qualified observer and interpreter;

(3) Distance and direction of recording station from blast area;

(4) Type of ground recording station and material on which the instrument is sitting;

(5) Maximum particle velocity in each direction;

(6) A dated and signed copy of the seismograph readings; and

(7) Post-blast condition survey.

(d) Results of airblast monitoring.

(e) Results of post blast condition survey.

Acceptance. Material for rock blasting will be evaluated under Subsections

Rock blasting work and services will be evaluated.

11. AUTO CADD VIEWS

12. ESTIMATE DATA

S.No Description of Work No Length Bredth Depth Quantity unit Rate/Per Amount1 Earth work in excavation of foundation of structures

as per drawing and technical specification,including setting out, construction of shoring andbracing, removal of stumps and other deleteriousmatter, dressing of sides and bottom andbackfilling with approved material as per MORTHspecification no.304

a In ordinary soils upto SDR soils using Machinery Avg.depthAbutments 2 10.000 7.650 2.000 306.00Piers 4 11.000 6.500 2.000 572.00Wing walls 4 10.000 5.000 2.650 530.00Toe walls (3.14*6.3*2/4) 4 9.891 0.600 0.600 14.24

1422.243say 1430.000 cum 61.20 87516.00

b In ordinary rock using Machinery Avg.depthAbutments 2 10.000 7.650 1.650 252.45Piers 4 11.000 6.500 1.650 471.90

724.350say 725.000 cum 250.00 181250.00

2 PCC (1:3:6) nominal mix in foundation withcrushed stone aggregate 40mm nominal mechanically mixed, Placed in foundation compacted including curing completeas per approved drawing & technicalspecification as per MORT&H spn.no.2100Abutments 2 10.000 7.650 0.150 22.95Piers 4 11.000 6.500 0.150 42.90Wing walls 4 10.000 5.000 0.150 30.00

95.85say 96.00 cum 3342.70 320899.00

3 Vibrated cement concrete in Open foundationcomplete as per Drawing and technicalspecifications as per MORT&H specificationNos.1500, 1700 & 2100 VCC M-15- of abutments, piers & wing wallsAbutments 2 10.000 7.650 1.000 153.00trep footing (3.65+5.65)/2 2 8.450 4.650 2.000 157.17Piers I footing 4 11.000 6.500 1.000 286.00II footing 4 10.000 4.500 0.750 135.00III footing 4 10.000 3.000 0.750 90.00First Footing 4 12.000 5.000 0.500 120.00trep footing (2.5+4.0)/2 4 12.000 3.250 2.000 312.00

1253.17say 1254.00 cum 3606.20 4522175.00

Name of work:- Construction of Bridge across Masivagu on Narayanapuram to Mittapalli road at km 10/800 in Yellandu Mandal of Khammam District

Detailed Estimate and Abstract Estimate

4 Vibrated cement concrete in sub structurecomplete as per Drawing and technicalspecifications as per MORT&H specificationNos.1500, 1700 & 2100 VCCM-15-Substructure for abutmentsspiers & wing wallsAbutments (1.15+3.65)/2 2 8.450 2.400 6.839 277.39Piers 4 7.500 1.500 7.339 330.26cutwaters (22/7/4*1.5*1.5) 4 1.768 1.000 7.339 51.90wing walls (0.5+2.5)/2 4 12.000 1.500 6.125 441.00

1100.54say 1101.00 cum 3814.20 4199434.00

5 Vibrated Reinforced cement concrete in Substructure complete as per approved Drawing andtechnical specifications as per MORT&H nos1500, 1700 & 2200 VRCC M-20-

a For Bed blocks and Backing wallsAbutments 2 8.450 1.200 0.300 6.08Backing wall over Abutments 2 8.450 0.35 1.886 11.16

-2 7.500 0.35 0.300 -1.58Piers 4 7.500 1.800 0.300 16.20cutwaters (22/7/4*1.8*1.8) 4 2.546 1.000 0.300 3.05

34.92 cumSay 35.00 cum 5136.50 179778.00

6 Vibrated Reinforced cement concrete in Substructure complete as per approved Drawing andtechnical specifications as per MORT&H nos1500, 1700 & 2200 VRCC M-30-for Bearing pedastals Bearing pedastals- (5*6) 30 0.930 0.520 0.150 2.18

Say 3.00 cum 5548.30 16645.00

7 Suplying ,fitting and fixing in position true toline and level elastomeric neoprenebearing confirming to IRC: 83 (Part -II ),section IX and Clause 2005 of MoRTHSpecifications complete including allaccessories as per approved drawing andTechnical Specifications and MORTHSpn.2000&2200 size 630x220x61mmOver piers 4 6.000 24.00Over abutments 2 3.000 6.00

30.00 no 5920.00 177600.008 Furnishing and placing reinforced cement concrete

VRCC M20 Super structure as per approvedDrawing and technical specifications as perMORT&HNos.1500, 1600 & 1700 and as perM.O.T DRG No BD/13-76, BD/14-76A & BD/15-76Aexcluding cost of steel and fabrication T-BEAM GIRDER SLABS 5 61.20 306.00

or say 306.00 cum 5136.50 1571769.00

14 Supplying ,fitting and placing uncoated steel reinforcement in foundations complete per drawing approved drawing and Specifications as per MORTHNo. SUB STRUCTUREBed block & backing walls & screen walls 1 34.92 100.00 Kg/cum 3.49Bearing pedastals 1 2.18 100.00 Kg/cum 0.22Skin reinforcement in abutments 2 148.41 5.00 Kg/sqm 1.48(8.45*2*6.839+6.839*(3.65+1.15))Skin reinforcement in wing walls 4 165.38 5.00 Kg/sqm 3.31(12*2*6.125+6.125*(2.5+0.5))Skin reinforcement in Piers 4 144.65 5.00 Kg/cum 2.89(7.5*2*7.339+7.339*3.14*1.5) 11.39

or say 12.00 MT 45141.20 541694.00

15 Supplying ,fitting and placing uncoated steel reinforcement in foundations complete per drawing approved drawing and Specifications as per MORTHNo. FOUNDATIONSSkin reinforcement in wing walls 4 159.936 5.00 Kg/sqm 3.20(12*(2+1+5+1+2*1.414)+5+2*(2.5+4))Skin reinforcement in abutments 2 206.50 5.00 Kg/sqm 2.06(8.45*(2+2*1.414)+2*(3.65+5.65)+10*(2+7.65+2)+7.65*2*2)Skin reinforcement in Piers 4 182.75 5.00 Kg/sqm 3.66(10*2*1.5+4.5*2*0.75+3*2*0.75)+11*(2+6.5+2)+6.5*2*2 8.92

or say 9.00 MT 45141.20 406271.00

16 Providing grouted rough stone revetment300 mm thick with 300mm size rough stonegrouted with0.25 Cum.ofC.C.1:4:8 mix 40mm sizeHBGmetal / chips (SS5)gradedincludingcost,seignorage cess conveyanceofallmaterialstosite, labour charges curing complete.For Revetment3.142*6*6*1.414/4 4 39.985 0.30 47.98

Say 48.00 cum 1676.20 80458.00

17 Providing rough stone revetment 300 mm thickusing 300mm size rough stonevariety includingcost, seigniorage,cess andcon-veyance of allmaterials tosite, labourcharges etc., completeToe wallToe wall(3.142*2*6.3)/4 4 9.90 0.60 0.60 14.25

Say 15.00 cum 0.0018 Providing filter material underneath

slopescomplete as per MOST specification 305, 309 &2504.3.142*6*6*1.414/4 4 39.985 0.15 23.99

Say 24.00 cum 1221.90 29326.0019 Backfilling behind abutments, wing walls

returnwall complete as per drawing andtechnicalas per MORT&H specification No ,Cl 710.1.4 of IRC :78behind abutments 2x1/2 7.450 4.951 8.575 316.28

Say 317.00 cum 351.40 111394.00

20 Providing and laying of filter media with Granular materials /stone crushed satisfyingthe requirements laiddown in 2504.2.2 of MORTH Specifications to a of not less than 600 mm with smaller sizetowards the soil and bigger size towards the and proviede over the entire surface behindabutment, wingwalland return wall to the fullheight compactedto a firmcondition per drawing andTechnicalSpecifications and per MORT&Hspecification Nos.2200and Cl.710.1behind abutments 2 7.450 0.600 10.575 94.54

Say 95.00 cum 1221.90 116081.0021 Providing weep holes in plain/ reinforced

concrete abutment,wing wall/ return wall with 100mm dia AC pipe, extendingthrough the full widthof thestructure with slope of 1V : 20Htowardsdrawing face.Complete as per drawing andtechnicalspecifications and as per MORT&Hspecification No 2706 & 2200 avg.lengthAbutments 2 8.000 6.000 2.400 230.40Wing walls 4 12.000 6.000 1.500 432.00

662.40Say 663.00 Rm

384.00 No 173.40 66586.0022 Drainage spouts complete as per drawing and

technicalspecifications and as per approved drg no.BD/1-69A.as per MORT&H specification No2705Drainage spouts 5 4.00 20.00 no 4592.20 91844.00

23 Providing Strip seal type expansion Joints per manufactures specification including alllabour charges etccompleteOver piers 4 8.45 33.80Over abutments 2 8.45 16.90

50.70

Say 51.00 Rm 8500.00 433500.00

16823380.0024 Provision for Pre survey estimate for taking bores L S

and sub-soil investigation and test results25 Provision for Masticpads L S26 Provision to Pylon construction L S27 Provision to Painting to Railing and rounding off L S

13. BRIDGE ACCESSORIES

Bridge accessories are various additional elements that are so important in bridge design and construction. They are:

Parapets

Expansion joints

Drainage

Waterproofing

13.1 Parapets

Parapets are provided on highway bridges and similar structures such as

retaining walls for the safety of errant vehicles and their occupants, pedestrians and other

road users. They also serve to provide protection to the areas beneath and adjacent to

structures, for example other roads, railways, buildings, etc.

The variation in types of vehicles using highways is considerable and

constantly changing. Vehicles vary in size, both in length and height, overall weight, axle

spacing and weight distribution. A vehicle’s response to an impact can also vary considerably

from model to model due to such features as engine position, provision of crumple zones,

suspension type, etc.

Parapets should be designed to have a reasonable appearance and should

not detract from the overall aesthetics of the structure to which they are attached. They should

further not cause forces to be applied to the supporting structure that would significantly

affect its structural requirements.

Since extensive damage can occur to a parapet during an impact,

structural members of a bridge should not be used as vehicle parapets. Parapets should be

designed such that joints being made from continuous welds of structural quality.

13.2 Expansion joints

Wherever two elements of a structure are moving relative to each other, it is

often necessary to provide an expansion joint which seals the gap between the two elements

while accommodating the relative movements. For bridges the gap is usually that between the

deck end and the abutment ballast wall. However, on long viaducts additional joints will

often be needed between sections of deck in order to limit the movement at any one point.

Expansion joints are by virtue of their function a point of weakness within a bridge and

history has highlighted many examples of joints leaking. As water, laden with de-icing salts,

has leaked onto bearing shelves or pier supports, corrosion of the reinforcement has

frequently resulted. The repairs which are required cost significantly more than the capital

cost of the joint alone, especially when the cost of traffic delays is taken into account. It is

therefore important to give full consideration to the design, detailing and installation of

bridge expansion joints in order to minimize the risk of the bridge owner being faced with

high repair bills in the future.

Fig: An expansion joint provided

An expansion joint must exhibit a number of characteristics for it to perform satisfactorily. It

must sustain loads and movements without being damaged itself or causing damage to other

parts of the structure. It should be water tight, give a good ride quality and not be hazardous

to road users, who could include cyclists, pedestrians and equestrians. The skid resistance of

the joint should match that of adjacent surfacing and noise emission from the joint should be

limited, especially if it is to be used in residential areas. Finally, any joint should be easily

inspected and maintained.

The final choice of joint type will depend on a number of factors. Joint

types should not be mixed on an individual joint, and this will often dictate the form of

maintenance works on an existing joint. For new applications the joint must clearly be able to

accommodate the predicted movements, but there are other factors related to the joints

performance which should be considered. These include the treatment of the verges and

footways, which may contain many services, the road alignment (gradient, cross-fall and

curvature), the proximity of junctions (where longitudinal loads will be more frequent) and

how heavily trafficked the joint will be. All of these factors can affect the performance and

hence life of an expansion joint, and need to be taken into account when considering the

whole-life cost of the joint. While a joint chosen purely on the basis of its initial capital cost

and speed of installation may perform perfectly well, some joints have been shown to fail

prematurely in adverse conditions. Replacing joints can prove to be very expensive once all

the associated traffic management and delay costs are taken into account. Such costs can

easily outweigh the initial capital expenditure in whole-life costing terms.

13.3 Drainage

Expansion joints do not generally fail because their movement capacity is

exceeded. Safety factors built into their design ensure this. Occasionally elements of joints

may deteriorate more rapidly because they are locally subject to higher than expected loads,

perhaps due to increased dynamic factors on wheel loads caused by uneven surfacing. The

main cause of failure is that water starts to leak through the joints. This can arise from poor

detailing of the joint, poor workmanship during its installation and simply the inherent

difficulty of completely sealing any joint between two elements moving relative to each

other. The management of water on the bridge deck is key to the successful functioning of an

expansion joint, and should be addressed early in any bridge’s design and not as an

afterthought.

Back-of-wall drainage is provided to prevent the build-up of hydrostatic

pressure on the rear face of the walls. It usually takes the form of a 150mm diameter porous

drain pipe located on top of the wall base which can be enclosed in no fines concrete. Above

this, for the full height of the wall, a drainage medium is provided.

Weep holes should be provided in all high walls in case the porous

drainpipes become inoperative for any reason. They should outfall just above the external

paved surface and, ideally, have a reverse fall to prevent continual dripping. In urban areas,

small-diameter pipes, say 50mm at 3m centres, should be used; larger pipes often attract

vermin and are also frequently blocked by litter, such as cans and bottles.

Fig: Weep holes

provided in

abutment and

wingwall.

Fig : Drain holes provided on pavement of bridge

13.4 Waterproofing

In the case of bridge decks, waterproofing membranes normally comprise sheet

systems or liquid systems which are bonded to the concrete surface. In addition, mastic

asphalt has been used in the past but is now rarely used and is not recommended. Sheet

systems are mainly bituminized fabrics, polymer- or elastomeric-based membranes. They can

consist of sheets or boards, either incorporated into the membranes, or used to protect them.

Sheet membranes are pre-formed factory manufactured and are generally hand applied by the

pour-and-roll method or by torch or are self-adhesive. They are bonded to the surface in

overlapping strips and must not tear, puncture, rupture, or come apart at the\ seams, corners

and edges of the structure. Liquid systems are mainly acrylic, epoxy, polyurethane or bitumen

based. They are one or two part moisture or chemically curing solutions and can be applied

by brush.

13.5 Bearings

Bridge decks are subject to translational and rotational movements and to forces

from gravity, traffic, wind and friction. In supporting bridge decks, bearings have to cater for

these forces and movements. Translational movements principally arise from temperature

changes, creep, shrinkage and pre stress. Rotational movements arise principally from dead

and superimposed loading and from traffic loading. However, as the deck bends under

loading the bottom chord extends, resulting in additional translational movements on the

bearing. Conversely differential temperature changes through the depth of the deck and

parasitic effects of pre stress cause additional rotational movements at the bearings.

The bearings are usually fixed on a strong support capable of carrying the

longitudinal loads near the middle of the structure, with the remaining bearings free to move

longitudinally to accommodate temperature movements in either direction away from the

fixed pier towards the ends of the viaduct. With river valley crossings this may not be

suitable as the highest piers may be in the middle and due to their flexibility be inappropriate

for carrying the longitudinal forces, unless they are of heavy design to carry much longer

central spans. If the piers are tall and slender, the piers themselves may be capable of flexure

to cater for longitudinal deck movements, enabling fixed bearings to be installed, provided

the resulting eccentricity of vertical loading can be accommodated. Such a design enables the

longitudinal loading to be distributed between a number of supports. If any deck is inclined

longitudinally it is usual to install the fixed bearing at the lower end.

Elastomeric bearings can be vulcanized rubber or neoprene. The

material is essentially incompressible volumetrically, but an elastomeric pad bulges sideways

under vertical pressure and so provides elastic support or rotational capacity. In addition,

elastomeric pads have shearing movement capacity and so can accommodate horizontal

movement. By inserting horizontal steel plates spaced within the height of the pad a

laminated bearing is formed. This restricts the bulging on the sides and provides a stiffer

bearing under vertical load while accommodating similar shearing movement capacity. The

rotational capacity of an elastomeric bearing is limited to the compression applied by the

minimum vertical load to avoid uplift at the edge and is also limited by the maximum

compression. The shearing resistance needs to be taken into account in the design of the

supports.

As a general guide for shorter-span bridges, and particularly those with

concrete decks, where rotations are small, elastomeric bearings are economical. For medium

spans and more particularly for steel–concrete composite bridges, pot bearings are

appropriate and economical. For longer spans, for greater vertical stiffness or to

accommodate greater rotations in relation to the vertical load, spherical bearings are used. For

longer spans where very low friction is required, roller bearings might be used, but see the

caution under the section entitled ‘Roller bearings’ above. For rotation about a single axis

where high vertical loads have to be accommodated, rockers might be used. Where restraints

in the form of down stands would not provide adequate capacity, separate guide or restrain

bearings may be used. Leaf bearings may be used to transmit uplift forces.

Bearings should be installed such that they can be replaced with another

suitable bearing if and when required. The method of so doing needs to be carefully planned

during the original design of the structure. A decision needs to be taken as to what live

loading the structure will be carrying during jacking and bearing replacement. Provision for

jacking to enable replacement requires: adequate clearance between the support and the deck

for jacks of adequate capacity with locking ring facility to be inserted; sufficient space on the

support adjacent to the bearing for jack placement; the support and deck to be strong enough

to carry the jacking loads; the bearing installed by means enabling it to be slipped out with

minimal lifting of the deck; and anchor points provided to which temporary restraints can be

attached to replace fixity lost during bearing replacement. It may also be necessary to provide

temporary bearings in conjunction with the jacks to permit translational and/or rotational

movement during replacement.

Fig: Elastomeric bearings provided

14. CONCLUSION

Main importance of constructing a bridge here is to cross a stream, which

closes the route to many villages during floods. Now the interior villages are easily accessible

in any flood condition. The floods which have occurred

15.BIBILOGRAPHY

Several encyclopedias on the subject of bridge have provided bibliographies of bridge

related publications

TEXT BOOKS

1. Highway Bridge Structures by Tata McGraw hill.

2. Bridge Engineering by S.C. Rang wala.

3. IRC:78-2000 - Standard Specifications and Code of Practice for Road Bridges.

4. IRC:SP:66-2005 - Guidelines for Design and Construction of Continuous Bridges.

WEBSITES

http://en.wikipedia.org/wiki/Bridge

http://www.bridgeweb.com/

http://en.wikipedia.org/wiki/The_Official_Encyclopedia_of_Bridge