Project Report.pdf

Mini Project Report

On

BRIDGE CONSTRUCTION FOR NEW BROAD GAUGE LINE

A Dissertation submitted in partial fulfillment of

the requirement for the award of degree of

Bachelor of Technology

In

CIVIL ENGINEERING

By

LOHITH REDDY D (09241A0174)

T.S. ANURAG (09241A0156)

T. MAHESH (0924A01B5)

PAVAN VARMA K.N.S (09241A0186)

DEPARTMENT OF CIVIL ENGINEERING

GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY

(AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY)

NIZAMPET ROAD, HYDERABAD-500090

DEPARTMENT OF CIVIL ENGINEERING

CERTIFICATE

This is to certify that the project report entitled “BRIDGE CONSTRUCTION FOR

NEW BROAD GAUGE LINE” being submitted by LOHITH REDDY D (09241A0174) in

partial fulfillment for the award of the Degree of Bachelor of Technology to the Jawaharlal

Nehru Technological University. This record is a bona fide work carried out by him under my

guidance and supervision. The results embodied in this project report have not been submitted to

any other University or Institute for the award of any Degree or Diploma

Dr. Mohammed Hussain Dr. G.Venkata Ramana External Examinar

Internal Guide Head of the Department

DECLARATION:

I hereby declare that the work presented in this project titled “Bridge construction

for new broad gauge line” submitted towards completion of mini-project in sixth Semester of

B.Tech (CIVIL ENGINEERING) at the Gokaraju Rangaraju Institute of Engineering and

Technology affiliated to Jawaharlal Nehru Technological University, Hyderabad is authenticate

work and had not been submitted to any University or Institute for any award.

Place: Hyderabad

Date: 29/04/2013

D. LOHITH REDDY (09241A0174)

T.S. ANURAG (09241A0156)

T. MAHESH (0924A01B5)

PAVAN VARMA K.N.S (09241A0186)

ACKNOWLEDGEMENT

I would like to express my gratitude to all the people behind the screen who helped us

to transform an idea into real application.

I would like to express my heart-felt gratitude to my parents with whom I would not

have been privileged to achieve and full fill my dreams. I am grateful to our principal

Mr.Jandyala.N.Murthi who most ably run the institute and has had the major hand in enabling

me to do my project.

I profoundly thank Dr.G.Venkata Ramana, Head of the Department, Civil

Engineering, who has been an excellent guide and also great source of inspiration to my work.

I would like to thank my internal guide Dr. Md.Hussain for his technical guidance,

constant encouragement and support I carrying out my project work.

I would like to thank Mr. Ajay who guided us at the site at the time of execution

The satisfaction and euphoria that accompany the successful completion of task

would be great but in complete with the mention of the people who made it possible with here

constant guidance and encouragement crowns all the efforts with the success. In this context, I

would like thank all the other staff members teaching and non-teaching, who have extended their

timely help and eased my task.

Lohith Reddy D 09241A0174

ABSTRACT

BRIDGE CONSTRUCTION FOR NEW BROAD GUAGE LINE

From the moment human started exploring he started to travel across the world after the

world- war II due to the industrial revolution these became even intense to travel for overseas

human used only ships but to travel in his own country he made only slow means of transport

like bullock cart which not even safe. Then human started thinking about to decrease his travel

time and increase his own safety then they invented railway service which much safe, time

conserving due to the low in expenditure to travesl by trains many middle class and lower middle

class people depended on it a lot and it even cheap to transfer the good for long distance at low

price with lead to growth of importance of railway services. Construction of new railway is

really a tough task which involve in consideration of several parameters and several unexpected

conditions.

When the track is properly aligned it is a very good means of source of revenue to

government and also good means transportation for public.

At both the execution of construction work and even the maintenance it provide huge

opportunity of employment.

CODE AND REGULATIONS

Admixtures: - IS-9103

1. For reduction of water cement ratio:- IS-456

2. Water cement ratio:- IS-10262 ,IS-10264

3. Bridge bed block:- IS-1786-285

All the above specifications should be 2010 modifications and latest.

4. Maximum water cement ratio:- 0.40

5. Minimum cementicious material:-400kg/mt

6. Reinforcement high yield strength deformed bars: IRS-1786-1985

7. Abutments mix:-M25

8. Piers:-M30

CONTENTS

S.No TOPIC Page

1. CHAPTER-1 INTRODUCTION

1.1 Introduction to bridges 1

2. CHAPTER-2 TOPOGRAPHICAL SURVEY

2.1 Topographical survey 2

2.2 Alternative Alignment 2

2.3 Obligatory points 3

3. CHAPTER-3 DISCHARGE THROUGH DRAINAGE AREA

3.1 Discharge through drainage 4

4. CHAPTER-4 TYPES OF BRIDGES

4.1 Arch bridges 6

4.2 Reinforced slab bridges 6

4.3 Beam and slab bridges 7

4.4 Integral bridges 7

5. CHAPTER-5 TYPES OF FOUNDATIONS

5.1 Open foundation 9

5.2 Box foundation 10

5.3 Well foundation 10

5.3.1 Cutting edge 10

5.3.2 Curb 10

5.3.3 Steining 10

5.3.4 Bottom plug 11

5.3.5 Sand filling 11

5.3.6 Intermediate plug 11

5.3.7 Top plug 12

5.3.8 Reinforcement 12

5.3.9 Well cap 12

5.4 Sinking of wells 13

6. CHAPTER-6 PIER CONSTRUCTION

6.1 Pier construction 15

7. CHAPTER-7 PRE-STRESSED CONCRETE SLAB

7.1 Bonded post tensioned concrete 20

8. CHAPTER-8 POST-TENSIONED SLAB

8.1 post-tensioned concrete 22

9. CHAPTER-9 LAUNCHING OF PRE-STRESSED SLAB

9.1 Pre-tensioned slab 23

10. CHAPTER-10 INFLUENCING OF BUILDING MATERIALS

10.1 Building materials 24

10.1.1 Natural stone 24

10.1.2 Artificial stone, bricks, clinker 25

10.1.3 Reinforced and pre-stressed concrete 25

10.1.4 Steel and aluminum 27

10.1.5 Timber 29

10.2 Bridge construction technology 29

11. CHAPTER-11 TYPES OF BRIDGE CONSTRUCTION MACHINERIES

11.1 Construction machineries 31

11.1.1 Bridge cranes 31

11.1.2 Gantry cranes 32

11.1.2.1 Gantry cranes size and marking 32

11.1.2.2 Types of Gantry cranes 32

11.1.2.3 Renting gantry cranes 32

11.1.3 Floating cranes 33

11.1.3.1 Floating crane working 33

11.1.3.2 Floating crane uses 34

12. CHAPTER-12 TOTAL STATION

12.1 Coordinate measurement 35

12.2 Angular measurement 35

12.3 Distance measurement 35

12.4 Data processing 35

12.5 Applications 36

12.6 Mining 36

12.7 Stone block 36

13. CHAPTER-13 SLEEPERS

13.1 Wooden sleepers 37

13.2 Concrete sleepers 38

13.3 Steel sleepers 39

14. REFERENCES 40

15. LIST OF FIGURES

Figure 6.1 Parts of a pier

Figure 6.2 Machine for drilling a pier

Figure 6.3 Tay Bridge

Figure 6.4 Erection of a pier

Figure 7.1 Pre-stressed slab

Figure 7.2 Pre-stressed post tensioned anchor

Figure 11.1 Bridge crane

Figure 11.2 Gantry crane

Figure 11.3 Renting gantry crane

Figure 11.4 Floating crane

Figure 13.1 Wooden sleeper

Figure 13.2 Concrete sleeper

Figure 13.3 Steel sleeper

1

CHAPTER-1

INTRODUCTION

1.1 Introduction to Railway bridges:

Our mini project is totally concreted on railway bridge construction. In general rail

way track is aligned in most economical way but sometimes railway line come across several

obligatory points like holy places, schools, areas with high land value and even tributaries of

river or streams in such cases bridges and designed and constructed. It is done by following

methods. At first and foremost step followed align the railway line is topographical survey. In

this part a topographical map is used to check the possibilities of alignment of track and from

that the best possible path is finalized. Then the field test is carried out to get a clear idea about

the site condition. Which consist of total station survey for central line alignment, leveling works

which also results in finding the RL at different point and even useful to transfer them to

required location to avoid obstruction in visibility, then followed by soil exploration works

which involves in lab work.

Once these work is done the next procedure of work continues i.e. land acquisition as

a part of these the railway authority make contact with local revenue department officials for

land purchase from the respective owners.

Then it is followed by earth work where excavation work for different types of

foundation, as we know different methods of foundations are followed based on the ground

condition. When the main excavation work is done the bridge construction starts ex foundation,

piers to get all the piers in exact alignment total station is used. Once the piers are done then the

bed block marking is done over which precast girders are place. All these processes go into the

sub tenders form. When the construction of bridges is done, sleepers are placed at the site for the

next process i.e. track alignment along the center marked line.

2

CHAPTER-2

TOPOGRAPHICAL SURVEY

2.1 Topographical survey

A topographic map is a type of map characterized by large-scale detail and

quantitative representation of relief, usually using contour lines in modern mapping, but

historically using a variety of methods. Traditional definitions require a topographic map to show

both natural and man-made features. A topographic map is typically published as a map series,

made up of two or more map sheets that combine to form the whole map. A contour line is a

combination of two line segments that connect but do not intersect; these represent elevation on a

topographic map.

The Canadian Centre for Topographic Information provides this definition

“A topographic map is a detailed and accurate graphic representation of cultural and

natural features on the ground.”

Other authors define topographic maps by contrasting them with another type of map;

they are distinguished from smaller-scale "chorographic maps" that cover large regions, "plan

metric maps" that do not show elevations, and "thematic maps" that focus on specific topics.

However, in the vernacular and day to day world, the representation of relief

(contours) is popularly held to define the genre, such that even small-scale maps showing relief

are commonly (and erroneously, in the technical sense) called "topographic".

The study or discipline of topography, while interested in relief, is actually a much

broader field of study which takes into account all natural and manmade features of terrain.

2.2 Alternative alignment

As part of topographical survey all the possible alignment of railway line is examined.

3

2.3 Obligatory points

As a part of topographical survey we come across several obstruction like, holy place,

rivers streams, which leads to change the direction or bridge construction.

4

CHAPTER-3

DISCHARGE THROUGH DRINAGE AREA

3.1 Discharge through drainage area

The catchment of a river above a certain location is determined by the surface area of

all land which drains toward the river from above that point. The river's discharge at that location

depends on the rainfall on the catchment or drainage area and the inflow or outflow of

groundwater to or from the area, stream modifications such as dams and irrigation diversions, as

well as evaporation and evapo-transpiration from the area's land and plant surfaces. In storm

hydrology an important consideration is the stream's discharge hydrograph, a record of how the

discharge varies over time after a precipitation event. The stream rises to a peak flow after each

precipitation event, then falls in a slow recession. Because the peak flow also corresponds to the

maximum water level reached during the event, it is of interest in flood studies. Analysis of the

relationship between precipitation intensity and duration, and the response of the stream

discharge is mm by the concept of the unit hydrograph which represents the response of stream

discharge over time to the application of a hypothetical "unit" amount and duration of rain, for

example 1 cm over the entire catchment for a period of one hour. This represents a certain

volume of water (depending on the area of the catchment) which must subsequently flow out of

the river. Using this method either actual historical rainfalls or hypothetical "design storms" can

be modeled mathematically to confirm characteristics of historical floods, or to predict a stream's

reaction to a predated storm.

The relationship between the discharge in the stream at a given cross-section and the

level of the stream is described by a rating curve. Average velocities and the cross-sectional area

of the stream are measured for a given stream level. The velocity and the area give the discharge

for that level. After measurements are made for several different levels, a rating table or rating

curve may be developed. Once rated, the discharge in the stream may be determined by

measuring the level, and determining the corresponding discharge from the rating curve. If a

continuous level-recording device is located at a rated cross-section, the stream's discharge may

be continuously determined.

5

This is done based on the records of last 10 years if fluctuation is more it can be made

up to 20 years. Based on the analyses data for the discharge of drainage the bridges are finalized

based on the acting on them due to discharge of water, All the forces acting on pier, additional

that can be acted on bridges, span, reinforcement, amount of concrete is estimated at these stage.

6

CHAPTER-4

TYPES OF BRIDGES

4.1 Arch bridges

Arch bridges derive their strength from the fact that vertical loads on the arch generate

compressive forces in the arch ring, which is constructed of materials well able to withstand

these forces.

The compressive forces in the arch ring result in inclined thrusts at the abutments, and

it is essential that arch abutments are well founded or buttressed to resist the vertical and

horizontal components of these thrusts. If the supports spread apart the arch falls down. The

Romans knew all about this.

Traditionally, arch bridges were constructed of stone, brick or mass concrete since

these materials are very strong in compression and the arch could be configured so that tensile

stresses did not develop.

Modern concrete arch bridges utilize prestressing or reinforcing to resist the tensile

stresses which can develop in slender arch rings.

The shape attracted the attention of many of the early pioneers of concrete

construction. In 1930, Freyssinet was responsible for a spectacular arched bridge at Plougastel in

France and three years later, Swiss engineer, Robert Maillart created the famously elegant

Schwandbach bridge in which slender cross-walls tie the arch to the horizontally curved

roadway.

4.2 Reinforced slab bridges

For short spans, a solid reinforced concrete slab, generally cast in-situ rather than

precast, is the simplest design. It is also cost-effective, since the flat, level soffit means that false

work and formwork are also simple. Reinforcement, too, is uncomplicated. With larger spans,

the reinforced slab has to be thicker to carry the extra stresses under load. This extra weight of

the slab itself then becomes a problem, which can be solved in one of two ways. The first is to

use pre-stressing techniques and the second is to reduce the deadweight of the slab by including

7

'voids', often expanded polystyrene cylinders. Up to about 25m span, such voided slabs are more

economical than pre-stressed slabs.

4.3 Beam and slab bridges

Beam and slab bridges are probably the most common form of concrete bridge in the

India today, thanks to the success of standard precast pre-stressed concrete beams developed

originally by the Pre-stressed Concrete Development Group (Cement & Concrete Association)

supplemented later by alternative designs by others, culminating in the Y-beam introduced by the

Pre-stressed Concrete Association in the late 1980s.

They have the virtue of simplicity, economy, wide availability of the standard

sections, and speed of erection.

The precast beams are placed on the supporting piers or abutments, usually on rubber

bearings which are maintenance free. An in-situ reinforced concrete deck slab is then cast on

permanent shuttering which spans between the beams.

The precast beams can be joined together at the supports to form continuous beams

which are structurally more efficient. However, this is not normally done because the costs

involved are not justified by the increased efficiency.

Simply supported concrete beams and slab bridges are now giving way to integral

bridges which offer the advantages of less cost and lower maintenance due to the elimination of

expansion joints and bearings.

4.4 Internal bridges

One of the difficulties in designing any structure is deciding where to put the joints.

These are necessary to allow movement as the structure expands under the heat of the summer

sun and contracts during the cold of winter.

Expansion joints in bridges are notoriously prone to leakage. Water laden with road

salts can then reach the tops of the piers and the abutments, and this can result in corrosion of all

reinforcement. The expansive effects of rust can split concrete apart.

8

In addition, expansion joints and bearings are an additional cost so more and more

bridges are being built without either. Such structures, called 'integral bridges', can be

constructed with all types of concrete deck. They are constructed with their decks connected

directly to the supporting piers and abutments and with no provision in the form of bearings or

expansion joints for thermal movement. Thermal movement of the deck is accommodated by

flexure of the supporting piers and horizontal movements of the abutments, with elastic

compression of the surrounding soil.

Already used for lengths up to 60m, the integral bridge is becoming increasingly

popular as engineers and designers find other ways of

9

CHAPTER-5

TYPES OF FOUNDATIONS

5.1 Open foundation

An open caisson is similar to a box caisson, except that it does not have a bottom

face. It is suitable for use in soft clays (e.g. in some river-beds), but not for where there may be

large obstructions in the ground. An open caisson that is used in soft grounds or high water

tables, where open trench excavations are impractical, can also be used to install deep manholes,

pump stations and reception/launch pits for micro tunneling, pipe jacking and other operations.

A caisson is sunk by self-weight, concrete or water ballast placed on top, or by

hydraulic jacks. The leading edge (or cutting shoe) of the caisson is sloped out at a sharp angle to

aid sinking in a vertical manner; it is usually made of steel. The shoe is generally wider than the

caisson to reduce friction, and the leading edge may be supplied with pressurized bentonite

slurry, which swells in water, stabilizing settlement by filling depressions and voids. An open

caisson may fill with water during sinking. The material is excavated by clamshell excavator

bucket on crane.

The formation level subsoil may still not be suitable for excavation or bearing

capacity. The water in the caisson (due to a high water table) balances the up thrust forces of the

soft soils underneath. If dewatered, the base may "pipe" or "boil", causing the caisson to sink. To

combat this problem, piles may be driven from the surface to act as:

Load-bearing walls, in that they transmit loads to deeper soils.

Anchors, in that they resist floatation because of the friction at the interface

between their surfaces and the surrounding earth into which they have been driven.

H-beam sections (typical column sections, due to resistance to bending in all axes)

may be driven at angles "raked" to rock or other firmer soils; the H-beams are left extended

above the base. A reinforced concrete plug may be placed under the water, a process known

10

as Tremie concrete placement. When the caisson is dewatered, this plug acts as a pile cap,

resisting the upward forces of the subsoil.

5.2 Box foundation

A box caisson is a prefabricated concrete box (it has sides and a bottom); it is set

down on prepared bases. Once in place, it is filled with concrete to become part of the permanent

works, such as the foundation for a bridge pier. Hollow concrete structures float (seeWWII

concrete ships), so a box caisson must be ballasted or anchored to prevent this phenomenon until

it can be filled with concrete (indeed, elaborate anchoring systems may be required in tidal

zones); adjustable anchoring systems, combined with a GPS survey, allows engineers to position

a box caisson with pinpoint accuracy.

5.3 Well foundation

This work consists of construction of well foundation, taking it down to the

founding level through all kinds of sub-strata, plugging the bottom, filling the inside of the well,

plugging the top and providing a well cap in accordance with the details shown on the drawing.

Well may have a circular, rectangular, or D-shape in plan and may consist of one, two or more

compartments in plan.

Well Components & their Function

In brief the function of various elements is as follows:

5.3.1 Cutting edge

The mild steel cutting edge shall be made from structural steel sections. The cutting

edge shall weigh not less than 40 kg per meter length and be properly anchored into the well

curb, as shown in the drawing.

When there are two or more compartments in a well, the bottom end of the cutting

edge of the inner walls of such wells shall be kept at about 300 mm above that of outer walls.

5.3.2 Curb

The well curb may be precast or cast-in-situ. Steel formwork for well curb shall be

fabricated strictly in conformity with the drawing. The outer face of the curb shall be vertical.

11

Steel reinforcements shall be assembled as shown on the drawings. The bottom ends of vertical

bond rods of staining shall be fixed securely to the cutting edge with check nuts or by welds.

The formwork on outer face of curb may be removed within 24 hours after

concreting. The formwork on inner face shall be removed after 72 hours. It is made up of

reinforced concrete using controlled concrete of grade M-35.

5.3.3 Steining

The dimensions, shape, concrete strength and reinforcements of the well shall

strictly conform to those shown on the drawings. The formwork shall preferably be of M.S.

sheets shaped and stiffened suitably. In case timber forms are used, they shall be lined with

plywood or M.S. sheets. The steining of the well shall be built in one straight line from bottom

to top such that if the well is tilted, the next lift of steining will be aligned in the direction of the

tilt. After reaching the founding level, the well steining shall be inspected to check for any

damage or cracks

5.3.4 Bottom plug

Its main function is to transfer load from the steining to the soil below. For bottom

plug, the concrete mix shall be design (in dry condition) to attain the concrete strength as

mentioned on the drawing and shall contained 10 per cent more cement than that required for the

same mix placed dry.

5.3.5 Sand filling

Sand filling shall commence after a period of 3 days of laying of bottom plug.

Also, the height of the bottom plug shall be verified before starting sand filling. Sand shall be

clean and free from earth, clay clods, roots, boulders, shingles, etc. and shall be compacted as

directed. Sand filling shall be carried out up to the level shown on the drawing or as directed by

the Engineer.

5.3.6 Intermediate plug

The function of the plug is to keep the sand filling sandwiched & undisturbed. It

also act as a base for the water fill, which is filled over it up to the bottom of the well cap.

12

5.3.7 Top plug

After filling sand up to the required level a plug of concrete shall be provided over

it as shown on the drawing, It at least serves as a shuttering for laying well cap.

5.3.8 Reinforcement

It provides requisite strength to the structure during sinking and service.

5.3.9 Well cap

It is needed to transfer the loads and moments from the pier to the well or wells

below. A reinforced cement concrete well cap will be provided over the top of the steining in

accordance with the drawing. Formwork will be prepared conforming to the shape of well cap.

Concreting shall be carried out in dry condition. A properly designed false steining may be

provided where possible to ensure that the well cap is laid in dry conditions

After water filling, pre-cast RCC slabs shall be placed over the RCC beams as per

the drawings, as non-recoverable bottom shuttering for well cap. Initially built false wall shall act

as outer shuttering for well cap casting. In case, there is no false wall, then steel shuttering is to

be put from outer side.

For well Steining and well cap shuttering, permissible tolerances are as follows: -

Variation in dimension : +50 mm to –10mm

Misplacement from specified Position in Plan: 15mm

Variation of levels at the top : +/- 25mm

Depth of Well Foundation

As per I.R.C. bridge code, the depth of well foundation is to be decided on the following

considerations:

The minimum depth of foundation below H.F.L should be 1.33D, where D is the

anticipated max. Depth of scour below H.F.L depth should provide proper grip according to

some rational formula.

The maximum bearing pressure on the subsoil under the foundation resulting from

any combination of the loads and forces except wind and seismic forces should not exceed the

13

safe bearing capacity of the subsoil, after taking into account the effect of scour. With wind and

seismic forces in addition, the maximum bearing pressure should not exceed the safe bearing

capacity of the subsoil by more than 25%

While calculating maximum Bearing pressure on the foundation bearing layer

resulting from the worst combination of direct forces and overturning moments. The effect of

passive resistance of the earth on the sides of the foundation structure may be taken into account

below the maximum Depth of the scour only.

The effect of skin friction may be allowed on the portions below the maximum

Depth of scour. Accordingly for deciding the depth of well foundation we require correct

estimation of the following:

Maximum Scour depth.

Safe bearing capacity.

Skin friction.

Lateral earth support-below maximum scour level.

It is always desirable to fix the level of a well foundation on a sandy strata bearing

capacity. Whenever a thin stratum of clay occurring between two layers of sand is met with in

that case well must be pierced through the clayey strata. If at all foundation has to be laid on a

clayey layer it should be ensured that the clay is stiff.

5.4 Sinking of Wells

In case of well sinking on dry grounds, an open excavation up to half a meter

above subsoil water level is carried out and the well curb is laid. In case the wells are to be sunk

in mid-stream, a suitable cofferdam is constructed around the site of the well and islands are

made.

The islands in shallow water are formed by an edging of sand bags forming an

enclosure filled with sand or clay. When the water depth is of the order of 3 to 5 m. the site is

surrounded by sheet piling and the enclosure so formed is filled with clay or sand. The centre

point of well is accurately marked on the island and the cutting edge is placed in a level plain.

The wooden sleepers are inserted below the cutting edge at regular intervals so as to distribute

the load and avoid setting of the cutting edge unevenly during concreting. The inside shuttering

of the curb is generally made of brick masonry and plastered. The outer shuttering is made of

wood or steel.

Initially the well steining should be built to a height of 2m. Only. Later steining

should not allowed to be built more than 5m. at a time. For this bridge the subsequent lifts were

of 2.5 m. each.

The well is sunk by excavating material from inside under the curb. Great care

should be taken during well sinking in the initial stages because the well is very unstable.

Excavation of the soil inside the well can be done by sending down workers inside the wells.

14

When the depth of the water inside the well becomes more than one meter, the excavation is then

carried out by a Jham or a Dredger.

The sump position at 8 equidistant locations along dredge hole sides & at well

center are taken & recorded. The dredge water level is also recorded.

Vertical reinforcement of steining shall be bent & tied properly to facilitate the

grab movement during sinking operations.

The position of the crane shall be such that the operation shall be able to see the

signalman on the well top at all the times, & the muck is safely deposited away from the

intermediate vicinity of the well.

Grabbing process shall commence normally with the grabbing at the above

designated sounding positions.

If the well is not sinking after reasonable amount of grabbing is done, say after

two rounds of grabbing, the sump position shall be checked accordingly, in combination with the

tilt position, the grabbing pattern shall vary. The sump should not normally exceed 1.75m

average. And thereafter, air jetting or water jetting shall be resorted to.

The sinking operation shall be done in two shifts, day & night. In normal course,

the sump and the dredge hole water levels shall be observed twice in each shift, and the cutting

edge reduced level shall be checked by level at four positions at the end of the shift.

As the well sinks deeper, the skin friction on the sides of the well progressively

increases. To counteract the increased skin friction and the loss in weight of the well due to

buoyancy, additional loading known as kentledge is applied on the well. The kentledge is

comprised of iron rail, sand bags concrete blocks etc.

Pumping out of water from the inside of the well is effective when the well has

gone deep enough or has passed through a clayey stratum so that chances of tilts and shifts are

minimized during this process. When the well has been sunk to about 10 m. depth, sinking

thereafter should be done by grabbing, chiseling and applying kentledge. Only when these

methods have failed dewatering may be allowed up to depressed water level of 5 m. and not

more.

In case of sandy strata frictional resistance developed on the outer periphery is

reduced considerably by forcing jet of water on the outer face of the well all round.

15

CHAPTER-6

PEIR CONSTRUCTION

6.1 Pier construction

The dimensions and detailed construction of the cast-iron piers are shown in. A

single pier consisted of six columns of cast iron tied together by struts, bars and rods made from

wrought iron. Each pier in the high girders section was built up by bolting together seven flanged

cast-iron columns, giving seven tiers. The ends of the flanges were fastened together with eight

1.125 inch (1⅛) wrought iron bolts as shown in Figures 16 and 17, below.

(Figure 6.1 Parts of a pier)

16

Figure 6.2 machine for drilling a well

17

Figure 6.3 Tay Bridge

18

The four columns, forming a rectangle in plan view, had an outside diameter of 15 inches and a

wall thickness of 1 inch. The two outside columns had a diameter of 18 inches as shown in.

The bracing bars were secured to lugs cast as one with the column. The

horizontal bars (referred to in this unit as struts) were made from channel section wrought iron

and were secured at each end with two wrought iron bolts. The diagonal bars (referred to in this

unit as tie bars) were made from iron flats with a cross-section of 4.5 × 0.5 inches.

Each diagonal tie bar was held by a 1.125 inch bolt at one end and was jointed

into two sling plates at the other. The sling plates were attached by another 1.125 inch bolt going

through 1.25 inch (1¼) holes in the lugs. The tie bar could then be tensioned at the joint by two

cotters (opposed wedges) hammered into a slot that also housed a gib (metal pad), as shown.

As a pier was erected, the inside of each column was filled with Portland

cement, apparently to protect it against corrosion. The total weight of a pier complete with

cement filling, bars and top plinth was about 120 tons.

Figure 6.4 Erection of pier

19

CHAPTER-7

PRESTRESSED CONCRETE SLAB

Pre-stressed concrete is a method for overcoming concrete's natural weakness

in tension. It can be used to produce beams, floors or bridges with a longer span than is practical

with ordinary reinforced concrete. Pre-stressing tendons (generally of high tensile steel cable

or rods) are used to provide a clamping load which produces a compressive stress that balances

the tensile stress that the concrete compression member would otherwise experience due to a

bending load. Traditional reinforced concrete is based on the use of steel reinforcement

bars, rebars, inside poured concrete.

Pre-tensioned concrete is cast around already tensioned tendons. This method produces a good

bond between the tendon and concrete, which both protects the tendon from corrosion and allows

for direct transfer of tension. The cured concrete adheres and bonds to the bars and when the

tension is released it is transferred to the concrete as compression by static friction. However, it

requires stout anchoring points between which the tendon is to be stretched and the tendons are

usually in a straight line. Thus, most pre-tensioned concrete elements are pre-fabricated in a

factory and must be transported to the construction site, which limits their size. Pre-tensioned

elements may be balcony elements, lintels, floor slabs, beams or foundation piles. An

innovative bridge construction method using pre-stressing is the stressed ribbon bridge design.

Figure 7.1 Pre-stressed slab

20

7.1 Bonded post-tensioned concrete

Fig (7.2) Pre-stressed post-tension anchor on display at Instituto Superior Técnico's

civil engineering department

Bonded post-tensioned concrete is the descriptive term for a method of

applying compression after pouring concrete and the curing process (in situ). The concrete is cast

around a plastic, steel or aluminum curved duct, to follow the area where otherwise tension

would occur in the concrete element. A set of tendons are fished through the duct and the

concrete is poured. Once the concrete has hardened, the tendons are tensioned by hydraulic

jacks that react (push) against the concrete member itself. When the tendons have stretched

sufficiently, according to the design specifications (see Hooke's law), they are wedged in

position and maintain tension after the jacks are removed, transferring pressure to the concrete.

The duct is then grouted to protect the tendons from corrosion. This method is commonly used to

create monolithic slabs for house construction in locations where expansive soils (such

as adobe clay) create problems for the typical perimeter foundation. All stresses from seasonal

expansion and contraction of the underlying soil are taken into the entire tensioned slab, which

supports the building without significant flexure. Post-tensioning is also used in the construction

of various bridges, both after concrete is cured after support by false work and by the assembly

of prefabricated sections, as in the segmental bridge.

Among the advantages of this system over un-bonded post-tensioning are:

� Large reduction in traditional reinforcement requirements as tendons

cannot

� De-stress in accidents.

� Tendons can be easily "woven" allowing a more efficient design approach.

� Higher ultimate strength due to bond generated between

21

CHAPTER-8

POST TENSIONED CONCRETE

8.1 Post tensioned concrete

Un-bonded post-tensioned concrete differs from bonded post-tensioning by

providing each individual cable permanent freedom of movement relative to the concrete. To

achieve this, each individual tendon is coated with grease and covered by a plastic sheathing

formed in an extrusion process. The transfer of tension to the concrete is achieved by the steel

cable acting against steel anchors embedded in the perimeter of the slab. The main disadvantage

over bonded post-tensioning is the fact that a cable can de-stress itself and burst out of the slab if

damaged (such as during repair on the slab). The advantages of this system over bonded post-

tensioning are:

1. The ability to individually adjust cables based on poor field conditions

2. The procedure of post-stress grouting is eliminated

3. The ability to de-stress the tendons before attempting repair work.

Picture number 6.1 (below) shows rolls of post-tensioning (PT) cables with the

holding end anchors displayed. The holding end anchors are fastened to rebar placed above and

below the cable and buried in the concrete locking that end. Pictures numbered 6.2, 6.3 and

6.4 shows a series of black pulling end anchors from the rear along the floor edge form. Rebar is

placed above and below the cable both in front and behind the face of the pulling end anchor.

The above and below placement of the rebar can be seen in picture number three and the

placement of the rebar in front and behind can be seen in picture number four. The blue cable

seen in picture number four is electrical conduit. Picture number 6.5 shows the plastic sheathing

stripped from the ends of the post-tensioning cables before placement through the pulling end

anchors. Picture 6.6 shows the post-tensioning cables in place for concrete pouring. The plastic

sheathing has been removed from the end of the cable and the cable has been pushed through the

black pulling end anchor attached to the inside of the concrete floor side form. The greased cable

can be seen protruding from the concrete floor side form. Pictures 6.7 and 6.8show the post-

tensioning cables protruding from the poured concrete floor. After the concrete floor has been

poured and has set for about a week, the cable ends will be pulled with a hydraulic jack.

22

CHAPTER-9

LAUNCHING OF PRE-TENSIONED SLAB

9.1 Pre-tensioned slab

The technique of incremental launching has been well developed. It is used for

constructing multi span bridges across valleys and where it is desirable to minimize interference

with traffic. Typical span lengths are 20 to 40 m (65 to 130 ft), although span lengths up to 140

m (459 ft) have been used with steel girders. The launching of a steel box girder on a horizontal

curve has been successfully completed.

One example of an incrementally launched bridge is the Wupper Valley Bridge

on Autobahn 1. This project involved expanding the existing expressway from four to six lanes,

plus adding an emergency shoulder in each direction. The only solution was to build a second

bridge parallel to the existing one. The new bridge is a seven-span structure with span lengths

ranging from 44 to 72.8 m (144 to 239 ft) for a total length of 4,18.3 m (1,372 ft). The cross

section of the bridge consists of a rectangular steel U-shaped box beam (shown in figure 21a)

with deck cantilevers beyond the webs supported by inclined struts (shown in figure 21b).

Partial-depth, precast concrete deck slabs were used to eliminate the need for false work. The

slabs were placed on soft polymer strips to seal the joints. Shear studs from the steel beams

projected into openings in the precast slabs. These openings were filled with high-strength

concrete before placing a CIP concrete deck. The structure was incrementally launched using

hydraulic jacks that pushed on the end of the steel box beam. The piers were equipped with

sliding bearings to facilitate the launching. The nose at the front of the structure was equipped

with a hydraulically controlled lifting device that was used to raise the front of the structure as it

reached each pier. Before launching, the precast concrete slabs in the mid-span region were

placed. The slabs over the supports were then placed from the other slabs. If the steel

construction had been moved without the concrete slabs, the slabs would have had to be placed

on the bridge from the side—resulting in additional impact on traffic. If all concrete slabs had

been placed before launching the structure, the existing hydraulic equipment would not have had

sufficient capacity. This structure was reported to be the first to use precast deck slabs of this

size.

23

CHAPTER-10

INFLUENCE OF BUILDING MATERIALS

10.1 Building materials

The traditional building materials for bridges are stone, timber and steel, and more

recently reinforced and pre-stressed concrete. For special elements aluminum and its alloys and

some types of plastics are used. These materials have different qualities of strength, workability,

durability and resistance against corrosion. They differ also in their structure, texture and color or

in the possibilities of surface treatment with differing texture and color.

For bridges one should use that material which results in the best bridge regarding

shape, technical quality, economics and compatibility with the environment.

10.1.1 Natural stone:-

The great old bridges of the Etruscans, the Romans, the Fraters Pontific of the Middle

Ages (since about 1100) and of later master builders were built with stone masonry. The arches

and piers have lasted for thousands of years when hard stone was used and the foundations

constructed on firm ground. With stone one can build bridges which are both beautiful, durable

and of large span (up to 150 m). Unfortunately, stone bridges have become very expensive, if

considered solely from the point of view of construction costs.

Over a long period, however, stone bridges, which are well designed and well built,

might perhaps turn out be the cheapest, because they are long-lasting and need almost no

maintenance over centuries unless attacked by extreme air pollution. Stone is nowadays usually

confined to the surfaces, the stones being preset or fixed as facing for abutments, piers or arches.

Of course, sound weather-resisting stone must be chosen, and fundamental rock like granite,

gneiss, porphyry, diabas or crystallized limestone are especially suitable. Caution is necessary with

sandstones, as only siliceous sandstone is durable.

In Western Germany basalt-lava from the Eifel Mountains is popular. In choosing the

stone one should respect any local experience gained from old buildings and bridges. Stone is

worked upon in different ways, depending upon the direction of the natural strata occurring in the

quarry and on the requirements in the bridge Very different effects can be produced with stone by

the choice of the type of masonry, the height of the courses, the proportion of the stones (length to

height), the arrangement of the joints, the surface treatment etc., and especially the overall scale.

The choice of colors of the stone is also relevant. Granite of a uniform grey color and

sawn surface can look as dull as simple plain concrete. A harmonious mixture of different colors

and slightly embossed surfaces can look very lively, even when the masonry areas are extensive.

Surfaces can also be enlivened by bright or dark joint-filling. The sizes of the stone blocks and the

roughness of their surfaces must be harmonized with the size of the structure, the abutments, the

24

piers etc. Coarse embossing does not suit a small pier only 1 m thick and 5 m high, but large sized

ashlars masonry is suitable for large arch bridges such as the Saalebrucke Jena or the

Lahntalbrucke Limburg. Granite masonry was preferred for piers of bridges across the River

Rhine, because it resists erosion by sandy water much better than the hardest concrete.

10.1.2 Artificial stones, clinker and bricks:-

Amongst the artificial stones, clinker and hard-burned brick are used in bridges both

as liners and for bearing vaults. They were often used in northern Germany, the Netherlands,

Belgium and Denmark, because there is no suitable natural stone available. The warm colors of

clinker or brick blend happily into the landscape. Also in an urban environment, they are

preferable to plain concrete, if brick is the regional construction material.

The sizes of these stones are standardized, and one can only choose between different

types of joint arrangements. Small differences in color and a pleasing treatment of the joints can

embellish the surfaces. Finally, one can also use split concrete blocks for facing. If the concrete is

made with colorful aggregates, which break when being split, then masonry-work produced with

these artificial blocks can also look good - similar to masonry of natural conglomerates, which are

in fact nothing else but natural concrete.

10.1.3 Reinforced and pre-stressed concrete

Concrete is an all-round construction material. Almost every building contains some

concrete, but its questionable application in certain buildings-for example in its use in the style of

brutalism - has brought it into discredit. Its dull grey color has contributed to the fact that the word

concrete has become a synonym for ugly. In the field of bridges, concrete deserves a more

favorable judgment.

Not all concrete bridges have turned out to be beauties, but pleasing bridges can be

built with concrete if one knows the art. Concrete is poured into forms as a stiff but workable mix,

and it can be given any shape; this is an advantage and a danger. The construction of good durable

concrete requires special know-how - which the bridge engineer is assumed to have.

Good concrete attains high compressive strength and resistance against most natural

attacks though not against de-icing saltwater, or CO2 and SO2 in polluted air. However, its tensile

strength is low, and the use of concrete alone is therefore limited to structures which are only

subject to compressive stresses. But tensile stresses also occur in abutments and piers due to earth

pressure, wind, breaking forces and to internal temperature gradients.

To resist these tensile forces, steel bars must be embedded in the concrete, the so-

called reinforcing bars, and this has led to the development of reinforced concrete. The steel bars

only really come into play after the concrete cracks under tensile stresses. If the reinforcing bars

are correctly designed and placed, then these cracks remain as fine "hair cracks" and are harmless.

A second method of resisting tensile forces in concrete structures is by pre-stressing.

25

The zones of concrete girders which are under tensile stress due to loads or other

actions are first put under compression - are pre-compressed - so that the tensile forces must first

reduce these compressive stresses before actual tensile stresses come into being. This pre-

compression is obtained by tensioning high strength steel bars or wire bundles, which are in ducts

inside the concrete girder.

Tensioning elongates the steel bars and they are anchored in this state at the ends of

the girder, transferring this tensioning force as a compressive force onto the girder. These girders,

pre-stressed with 'active steel" (pre-stressing steel) are in addition reinforced with "passive steel"

(non-stressed steel bars) for various reasons. Pre-stressed concrete revolutionized the design and

construction of bridges in the fifties. With pre-stressed concrete, beams could be made more

slender and span considerably greater distances than with reinforced concrete.

Pre-stressed concrete - if correctly designed - also has a high fatigue strength under

the heaviest traffic loads. Pre-stressed concrete bridges soon became much cheaper than steel

bridges, and they need almost no maintenance - again assuming that they are well designed and

constructed and not exposed to de-icing salt. So as from the fifties pre-stressed concrete came well

to the fore in the design of bridges.

All types of structures can be built with reinforced and pre-stressed concrete:

columns, piers, walls, slabs, beams, arches, frames, even suspended structures and of course shells

and folded plates. In bridge building, concrete beams and arches predominate. The shaping of

concrete is usually governed by the wish to use formwork which is simple to make. Plain surfaces,

parallel edges and constant thickness are preferred. This gives a stiff appearance to concrete

bridges, and avoiding this is one task of good aesthetic design.

The extra cost for one-way curved surfaces, for tapering piers, for varying depth of

beams or arch ribs is as a rule comparatively small. Therefore one should not hesitate to choose

such divergences from the most primitive and simple forms in order to improve appearance.

There is one great disadvantage to concrete as it emerges from the forms: the

inexpressive, dull grey color of the cement skin. The surfaces frequently show stains, irregular

streaks from placing the concrete in varying layers, and pores or even cavities from deficient

compaction, which ire then patched more or less successfully. These deficiencies have lead to a

widespread aversion to concrete, As well as to efforts for improvement. Some of the methods used

to achieve a good concrete finish in buildings, like profiles and patterns on the formwork, ribs or

accentuated timber veins etc. are not generally suitable.

The best effect is obtained by bush hammering as was usual between 1934 and 1945

for the bridges of the German autobahn system. The concrete coating of the reinforcement is

increased by 10 to 15 mm, so that a thin layer together with the cement skin can be taken off by

fine or coarse bush hammering. The aggregate is then exposed with its structure and color.

26

The protection of the embedded steel is not damaged, because the exterior cement

skin is in any case the worst part of concrete. It is very porous, because mixing water collects at

the forms of vibrating the concrete, and it is the porosity of the cement skin which makes it so

susceptible to collecting the dirt of polluted air. With bush hammering one can adapt the degree of

roughness to the size of the surfaces. Piers of viaducts, for example, were chiseled very roughly,

taking off pieces 20 to 30 mm in depth by oblique chisel work.

The color can be favorably influenced by the choice of colored aggregates like red

porphyry or yellow limestone. Such surfaces age as well as natural stone masonry, and they retain

their texture over a long period of time. The cement skin can also be washed off by special means

after the concrete has hardened - such "exposed aggregate" surfaces can look pleasing, depending

on the color and size of the aggregates. Bush hammering was given up after about 1950 due to the

high labour cost. At that time suitable machines were not yet available, but with modern

machinery this treatment should now be taken up again to embellish concrete surfaces.

Another possibility is coloring the concrete it has been well developed during the last

decade. By the use of mineral color pigments natural warm tones can be attained - earthy colors

with tones of ochre, reddish-brown sepia. Umber, greyish-green, slate-grey. Dark toned piers of a

viaduct often look better in the landscape than with a light grey color. Bright colored concrete-

with white cement-can for example be chosen to emphasize a fascia beam.

Fritz Leonhardt has often recommended the painting of bridges in the same way that

steel bridges are painted for corrosion protection. At the same time the dreary grey of normal

concrete is converted into a harmonious colorful statement. For painting, soft colors should again

be chosen and not bright loud colors. Before painting, the porous cement skin must be removed, so

that the paint will not peel off later.

Mineral colors, especially those with flour- or siliceous compounds, can also give an

additional protection to the concrete. The colour film must be hygroscopic, so that it does not

prevent the change of moisture content in the concrete. If the choice of color and type of paint is

based on the most up-to-date information, then these paints can last long and keep their color like

the paintwork of many old houses and churches, particularly in the Alps, which is often more than

200 years old and still beautiful. Color painting of concrete bridges has already been used in

several places. A most striking example is that of the long bridges along the riverbanks in

Brisbane, Australia.

10.1.4 Steel and aluminum

Amongst bridge materials, steel has the highest and most favorable strength qualities,

and it is therefore suitable for the most daring bridges with the longest spans. Normal building

steel has compressive and tensile strengths of 370 N/mm2, about ten times the compressive

strength of a medium concrete and a hundred times its tensile strength. A special merit of steel is

its ductility due to which it deforms considerably before it breaks, because it begins to yield above

27

a certain stress level. This yield strength is used as the first term in standard quality terms.

For bridges high strength steel is often preferred. The higher the strength, the smaller

the proportional difference between the yield strength and the tensile strength, and this means that

high strength steels are not as ductile as those with normal strength.

Nor does fatigue strength rise in proportion to the tensile strength. It is therefore

necessary to have a profound knowledge of the behavior of these special steels before using them.

For building purposes, steel is fabricated in the form of plates (6 to 80mm thick) by means of

rolling when red hot. For bearings and some other items, cast steel is used. For members under

tension only, like ropes or cables, there are special steels, processed in different ways which allow

us to build bold suspension or cable-stayed bridges.

The high strengths of steel allow small cross-sections of beams or girders and

therefore a low dead load of the structure. It was thus possible to develop the light-weight

"orthotropic plate" steel decks for roadways, which have now become common with an asphalt

wearing course, 60 to 80 mm thick.

The pioneers of this orthotropic plate construction called it by the less mysterious and

less scientific name "stiffened steel slabs". Plain steel plate, stiffened by cells or ribs, forms the

chord of both the transverse cross girders and the longitudinal main-girders. Simultaneously it acts

as a wind girder. This bridge deck owes its successful application mainly to mechanized welding,

which is now in general use and which has greatly influenced the design of steel bridges.

So plate girder construction now prevails, in which large thin steel plates must be

stiffened against buckling. Previously, vertical stiffeners were placed by preference on the outer

faces; longitudinal stiffeners were then arranged on the inside.

Today all stiffeners are placed on this inside so as to achieve a smooth outer surface

allowing no accumulation of dust or dirt deposits that retain humidity and promote corrosion - the

"Achilles heel" of steel structures. Modern steel girder bridges now hardly differ from prestressed

concrete bridges in their external appearance - except perhaps in their color. This is perhaps

regrettable, because stiffeners on the outside enliven the plate-faces, give scale and make the

girder look less heavy. In addition to plate girders, trusses also take full advantage of the material

properties of steel. Very delicate looking bridges can be built by joining slender steel sections

together to form a truss.

Again welding has improved the potential for good form, because hollow sections

can be fabricated and joined without the use of big gusset plates. In this way smooth looking

trusses arise without the "unrest" which occurs by joining two or four profiles of rolled section

with lattice or plates. Steel must be protected against corrosion and this is usually done by

applying a protective paint to the bare steel surface. Painting of normal steels is technically

necessary and can be used for color design of the bridge.

28

The choice of colors is an important feature for achieving good appearance. There are

steels which do not corrode in a normal environment (the stainless steels V2A and V4A to DIN

17440), but are so expensive that they are used only for components that are either particularly

susceptible to the attacks of corrosion or that are very inaccessible.

From the USA came Tentor steel, alloyed with copper, its 'first corrosion layer being

said to protect it against further corrosion. This protective rust has a warm sepia-toned color which

looks fine in open country. This type of protection, however, does not last in polluted air and the

corrosion continues. For steel bridges, good use should be made of the technical necessity of

protecting the steel with paint to improve appearance and to achieve harmonious integration of the

structure within the landscape.

Aluminum was occasionally used for bridges and the same form was used as for

steel girders. Aluminum profiles are fabricated by the extrusion process which allows many varied

hollow shapes to be formed, so that aluminum structures can be more elegant than those of steel.

Aluminum profiles are popular for bridge parapets because they need no protective paint.

10.1.5Timber:-

Timber has favorable qualities of strength for resisting compression, tension and

bending. Rough tree trunks or sawn timber beams have been used since primitive times for beam

bridges; raking frames and arches soon allowed larger spans. The Swiss carpenters, the brothers

Grubennann reached a 100 m span with the timber bridge across the River Rhine near

Schaffhausen. Timber should be protected against rain and therefore covered bridges with a roof

and sidewalls with windows evolved, and many of these are rightly preserved in the Alpine

countries, testifying to the high standard of their craftsmanship.

Many now only serve pedestrians. Recently timber bridges have been given a new

impetus by glue technology which allows larger cross-sections and larger lengths of beams to be

made than grow naturally. Moreover timber can now be better protected against weather and insect

attack. So new possibilities have arisen or the choice of structure, for its shaping and for the size.

Large timber trusses and even folded space trusses have been built using steel gusset plates for

jointing the members. Timber bridges, however, have limits of span and carrying capacity,

confining them mainly to bridges for pedestrians or for secondary roads.

10.2 Bridge construction technology

Bridge construction technology has evolved over the years. In this age of advanced

science, technology and machines, bridges have undergone various changes and different types

of bridges are being constructed in major countries of the world. Construction techniques like

slurry walls, post-tensioning, soil freezing, reinforced earth walls, suspension, folding etc. are

being used. Bridge construction is changing. New construction techniques and new materials are

29

emerging and accordingly the construction machinery industry has played a pivotal role.

30

CHAPTER-11

TYPES OF BRIDGE CONSTRUCTION MACHINERIES

11.1 Construction machineries

The various machineries for constructing bridges are:

Bridge Crane

Gantry Crane

Floating Crane

11.1.1 Bridge cranes:-

Bridge crane is a heavy machinery that is designed to build or fix a bridge. It operates on two

tracks and has four way horizontal movement. Bridge cranes cover rectangular area and can be

floor supported or hung from the ceiling. The main components of bridge cranes are bridge,

trolley, hoist drum, hoist cable, hoist block, hook bumpers, pendant and limit switches. On-off

switch is on control pendant for taking emergency steps, in the event of failure of any of the

control-panels.

Bridge cranes are either double girder or single girder. Double girder bridge crane can be utilized

at any capacity where extremely high hook lift is required because the hook can be pulled up

between the girders. For high speeds and heavy services too, double girder bridge cranes are very

useful. In bridge crane rigid box girder construction and durable trolley design are well suited for

heavy service applications.

Figure 11.1 Bridge crane

31

11.1.2 Gantry cranes

Gantry cranes are those cranes which are generally used for moving heavy loads. They are a

common type of portable material handling equipment used in job station or secondary task

areas. Gantry cranes are quite similar to overhead cranes except that the bridge which carries

trolley is rigidly supported on two or more legs running.

11.1.2.1 Gantry crane sizes and marking:-

Though gantry cranes are known for its huge models but, there happen to be smaller

cranes as well that are found in small industries and warehouses etc. The cranes are available in

both, adjustable as well as fixed height. Its making too is either of steel or aluminum, depending

upon the application of the crane. Each gantry crane is designed with two upright beams and a

cross beam. It has an A-frame shaped set of two legs with wheels beneath to render maximum

mobility and portability.

11.1.2.2 Types of gantry cranes:-

Gantry cranes can be of different range like single girder, double girder, double leg,

single leg, and cantilever styles for indoor or outdoor service. It is also available in fixed height

steel and adjustable steel. Gantry crane is an economical device for lifting materials anywhere in

a facility. Gantry cranes are also supplied with four roller-bearing steel wheels for easy

maneuverability.

Uses of gantry cranes:-

Gantry cranes or bridge cranes are useful machinery which find its application in

constructing bridges. Lifting heavy industrial devices, lifting containers in seaports, and are ideal

for use in air craft, automotive, and marine repair shops.

Figure 11.2 Gantry crane

32

11.1.2.4 Renting Gantry Crane

For companies that cannot afford to buy a whole new gantry crane, it would be most

cost effective to get a gantry crane on rent. Getting used gantry cranes have many advantages,

the best being that one does not have to shell out a big amount upfront to get the required

equipment.

A floating crane refers to a type of sea vessel which has a crane mounted on it. In

earlier days, floating crane designs were nothing more than old ships transformed to include a

huge crane mounted over the deck. Eventually, catamaran, semi-submersible designs changed

the face of floating cranes. Read on to know more about these cranes.

11.1.3 Floating Cranes

Floating cranes are those heavy-duty cranes which are frequently used for building

bridges, and constructing ports. Fleeting applications in ports etc. They also have great utility in

loading and unloading of heavy weights on and off ships. The floating cranes are generally self-

propelled. They have the powerful diesel generators to work the crane winches, which can be

switched to propel the craft.

11.1.3.1 Floating Cranes Working

Floating cranes can be mounted on a swing base installed on the deck of a pontoon

and can swing in a circular motion both in a clockwise and anticlockwise direction. Apart from

pontoon mounted cranes, some floating cranes barges with a lifting capacity exceeding 10,000

tones and are used to transport entire bridge sections.

11.1.3.2 Floating Cranes Uses

There are various uses of a floating crane. These vessels are able to lift and

maneuver huge and heavy sub-assemblies into position. Floating cranes also felicitate the

assembly of massive projects out of numerous smaller assemblies in most weather conditions.

Figure11.3Renting gravity crane

33

Apart from drilling and construction purposes, floating cranes are used for sunken ship retrieval

purposes also.

Used Floating Crane

Since these are one of the most expensive types of construction cranes, the trend of

hiring used floating cranes for a given time period is quite popular among builders and

construction workers. One can find a number of floating crane suppliers online to set hiring or

purchasing deals.

For building bridges launching girder is an important machinery. With sophisticated equipment,

launching girder itself is a normal structure. With different launching capacities and heights,

launching girders are used for making different kinds of bridges. Launching girder itself is a steel

structure which moves forward on the bridge piers span by span. As launching girder can handle

cast-in place concrete, as well as prefabricated elements, it is highly adaptable for a wide range

of spans and types of superstructure

Figure 11.4 Floating crane

34

CHAPTER-12

TOTAL STATION

12.1 Coordinate measurement

Coordinates of an unknown point relative to a known coordinate can be determined

using the total station as long as a direct line of sight can be established between the two points.

Angles and distances are measured from the total station to points under survey, and

the coordinates (X, Y, and Z or northing, easting and elevation) of surveyed points relative to the

total station position are calculated using trigonometry and triangulation. To determine an

absolute location a Total Station requires line of sight observations and must be set up over a

known point or with line of sight to 2 or more points with known location.

For this reason, some total stations also have a Global Navigation Satellite

System Interface which does not require a direct line of sight to determine coordinates. However,

GNSS measurements may require longer occupation periods and offer relatively poor accuracy

in the vertical axis.

12.2 Angle measurement

Most modern total station instruments measure angles by means of electro-optical

scanning of extremely precise digital bar-codes etched on rotating glass cylinders or discs within

the instrument. The best quality total stations are capable of measuring angles to 0.5 arc-second.

Inexpensive "construction grade" total stations can generally measure angles to 5 or 10 arc-

seconds.

12.3 Distance measurement

Measurement of distance is accomplished with

modulated microwave or infrared carrier signal, generated by a small solid-state emitter within

the instrument's optical path, and reflected by a prism reflector or the object under survey. The

modulation pattern in the returning signal is read and interpreted by the computer in the total

station. The distance is determined by emitting and receiving multiple frequencies, and

determining the integer number of wavelengths to the target for each frequency. Most total

stations use purpose-built glass corner cube prism reflectors for the EDM signal. A typical total

station can measure distances with an accuracy of about 1.5 millimeters (0.0049 ft) + 2 parts per

million over a distance of up to 1,500 meters (4,900 ft).

Reflector less total stations can measure distances to any object that is reasonably light in color,

up to a few hundred meters.

12.4 Data processing

Some models include internal electronic data storage to record distance, horizontal

angle, and vertical angle measured, while other models are equipped to write these

measurements to an external data collector, such as a hand-held computer.

When data is downloaded from a total station onto a computer, application software

can be used to compute results and generate a map of the surveyed area. The new generation of

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total stations (e.g. Hilti POS 15/18) can also show the map on the touch-screen of the instrument

right after measuring the points.

12.5 Applications:-

Total stations are mainly used by land surveyors and Civil Engineers, either to

record features as in Topographic Surveying or to set out features (such as roads, houses or

boundaries). They are also used by archaeologists to record excavations and by police, crime

scene investigators, private accident re-constructionists and insurance companies to take

measurements of senesce

12.6 Mining

Total stations are the primary survey instrument used in mining surveying.

A total station is used to record the absolute location of the tunnel walls (stopes),

ceilings (backs), and floors as the drifts of an underground mine are driven. The recorded data

are then downloaded into a CAD program, and compared to the designed layout of the tunnel.

The survey party installs control stations at regular intervals. These are small steel

plugs installed in pairs in holes drilled into walls or the back. For wall stations, two plugs are

installed in opposite walls, forming a line perpendicular to the drift. For back stations, two plugs

are installed in the back, forming a line parallel to the drift.

A set of plugs can be used to locate the total station set up in a drift or tunnel by

processing measurements to the plugs by intersection and resection

12.7 Stone block

The type of sleeper used on the predecessors of the first true railway (Liverpool and

Manchester Railway) consisted of a pair of stone blocks laid into the ground, with the chairs

holding the rails fixed to those blocks. One advantage of this method of construction was that it

allowed horses to tread the middle path without the risk of tripping. In railway use with ever

heavier locomotives, it was found that it was hard to maintain the correct gauge. The stone

blocks were in any case unsuitable on soft ground, where timber sleepers had to be used.

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CHAPTER-13

SLEEPERS

13.1 Wooden sleepers

Figure 13.1 Wooden sleeper

A variant fastening of rails to wooden ties .

A variety of softwood and hardwoods timbers are used as ties, oak, jarrah and karri being

popular hardwoods, although increasingly difficult to obtain, especially from sustainable sources.

Some lines use softwoods, including Douglas fir; while they have the advantage of

accepting treatment more readily, they are more susceptible to wear but are cheaper, lighter (and

therefore easier to handle) and more readily available. Softwood is treated, historically

using creosote, but nowadays with other less-toxic preservatives to improve resistance to insect

infestation and rot. New boron-based wood preserving technology is being employed by major

US railroads in a dual treatment process in order to extend the life of wood ties in wet areas.

Some timbers (such as sal, mora, jarrah or azobé) are durable enough that they can be used

untreated.

Problems with wood ties include rot, splitting, insect infestation, plate-cutting

(known as chair shuffle in the UK), (abrasive damage to the tie caused by lateral motion of the

tie plate) and spike-pull (where the spike is gradually loosened from the tie). For more

information on wood ties the Railway Tie Association maintains a comprehensive website

devoted to wood tie research and statistics.

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13.2 Concrete sleepers

Figure 13.2 Concrete sleeper

In concrete railroad ties increased after World War II following advances in the design, quality

and production of pre-stressed concrete. Concrete ties were cheaper and easier to obtain than

timber and better able to carry higher axle-weights and sustain higher speeds. Their greater

weight ensures improved retention of track geometry especially when installed with continuous-

welded rail. Concrete sleepers have a longer service life and require less maintenance than

timber due to their greater weight which helps them remain in the correct position longer.

Concrete sleepers need to be installed on a well-prepared sub grade with an adequate depth on

free-draining ballast to perform well.

In 1877, M. Monnier, a French gardener, suggested that concrete could be used for

making ties for railway track. Monnier designed a tie and obtained a patent for it, but it was not

successful. Designs were further developed and the railways of Austria and Italy used the first

concrete ties around the turn of the 20th century. This was closely followed by other European

railways.

Major progress was not achieved until World War II, when the timbers used for ties

were scarce due competition from other uses, such as mines. Following research carried out on

French and other European railways, the modern pre-stressed concrete tie was developed.

Heavier rail sections and long welded rails were also being installed, requiring higher-quality

ties. These conditions spurred the development of concrete ties in France, Germany and Britain,

where the technology was perfected. On the highest categories of line in the UK (those with the

highest speeds and tonnages) pre-stressed concrete sleepers are the only ones permitted

by Network Rail standards.

Most European railways also now use concrete bearers in switches and crossing

layouts due to the longer life and lower cost of concrete bearers compared to timber, which is

increasingly difficult and expensive to source in sufficient quantities and quality.

On November 8, 2011, the US Federal Railroad Administration (FRA) put into

effect new regulations on concrete ties, with notices published by the FRA in the April 1 and

September 9, 2011 U. S. Federal Register. The FRA notices say that the need for the new rules

was shown by the derailment of an Amtrak train near Home Valley, Washington on April 3,

2005, which according to the U.S. National Transportation Safety Board was caused in part by

38

excessive concrete tie abrasion. To be counted as a good tie under FRA regulation 213.109(d)(4),

a concrete ties shall not be deteriorated or abraded under the rail to a depth of one-half inch or

more. Limits on other types of concrete tie deterioration are also given.

13.3 Steel sleepers

Figure 13.3 Steel sleeper

Steel sleepers are formed from pressed steel and are trough-shaped in section. The

ends of the sleeper are shaped to form a "spade" which increases the lateral resistance of the

sleeper. Housings to accommodate the fastening system are welded to the upper surface of the

sleeper. Steel sleepers are now in widespread use on secondary or lower-speed lines in the UK

where they have been found to be economical to install due their ability to be installed on the

existing ballast bed. Steel sleepers are lighter in weight than concrete and able to stack in

compact bundles unlike timber. Steel sleepers can be installed onto the existing ballast, unlike

concrete sleepers which require a full depth of new ballast. Steel ties are 100% recyclable and

require up to 60% less ballast than concrete ties and up to 45% less than wood ties.

Historically, steel ties (sleepers) have suffered from poor design and increased

traffic loads over their normally long service life. These aged and often obsolete designs limited

load and speed capacity but can still be found in many locations globally and performing

adequately despite decades of service. There are great numbers of steel ties with over 50 years of

service and in some cases they can and have been rehabilitated and continue to perform well.

Steel ties were also used in specialty situations, such as the Hejaz Railway in the Arabian

Peninsula, which had an ongoing problem with Bedouins who would steal wooden ties for

campfires.

Modern steel ties handle heavy loads, have a proven record of performance in

signalized track, and handle adverse track conditions. Of high importance to railroad companies

is the fact that steel ties are more economical to install in new construction than creosote-treated

wood ties and concrete ties. Steel ties are utilized in nearly all sectors of the worldwide railroad

systems including heavy-haul, class 1’s, regional, short lines, mining, electrified passenger lines

(OHLE) and all manner of industries.

39

Notably, steel ties (bearers) have proven themselves over the last few decades to be

advantageous in turnouts (switches) and provide the solution to the ever-growing problem of

long timber ties for such use.

40

REFERENCES

1. Soil mechanics by Gopal Ranjan

2. Advanced foundation engineering by B.M.Das

3. http://www.nptel.iitm.ac.in/video.php?subjectId=105107123

4. http://www.nptel.iitm.ac.in/video.php?subjectId=105107137

5. http://www.cdeep.iitb.ac.in/nptel/Civil%20Engineering/Transportation%20Engg%20I/T

OC.html

6. wiki.iricen.gov.in/doku/lib/exe/fetch.php?media=bridge...code.pdf

7. Mitchell, J.K., and Soga, K. (2005) Fundamentals of soil behavior, Third edition, John

Wiley and Sons, Inc., ISBN 978-0-471-46302-7.

8. Santamarina, J.C., Klein, K.A., & Fam, M.A. (2001). Soils and Waves: Particulate Materials

Behavior, Characterization and Process Monitoring. Wiley. ISBN 978-0-471-49058-6.

9. http://en.wikipedia.org/wiki/Rail_transport_in_India.

10. Powrie, W., Spon Press, 2004, Soil Mechanics - 2nd ed ISBN 0-415-31156-X

11. A Guide to Soil Mechanics, Bolton, Malcolm,Macmillan Press, 1979. ISBN 0-333-18932-0

12. Fang, Y., Spon Press, 2006, Introductory Geotechnical Engineering

13. Lambe, T. William & Robert V. Whitman. Soil Mechanics. Wiley, 1991; p. 29. ISBN 978-0-

471-51192-2

14. Holtz, R.D, and Kovacs, W.D., 1981. An Introduction to Geotechnical Engineering.

Prentice-Hall, Inc. page 448

15. Wood, David Muir, Soil Behavior and Critical State Soil Mechanics, Cambridge University

Press, 1990, ISBN 0-521-33249-4

16. Disturbed soil properties and geotechnical design, Schofield, Andrew N.,Thomas Telford,

2006. ISBN 0-7277-2982-9

17. ASTM Standard Test Methods for Minimum Index Density and Unit Weight of Soils and

Calculation of Relative Density. http://www.astm.org/Standards/D4254.html

18. Cedergren, Harry R. (1977), Seepage, Drainage, and Flow Nets, Wiley. ISBN 0-471-

14179-8

41

19. Jones, J. A. A. (1976). "Soil piping and stream channel initiation". Water Resources

Research 7 (3): 602–610. Bibcode:1971WRR.....7..602J. doi:10.1029/WR007i003p00602.

20. Terzaghi, K., Peck, R.B., and Mesri, G. 1996. Soil Mechanics in Engineering Practice. Third

Edition, John Wiley & Sons, Inc. Article 18, page 135.

21. Terzaghi, K., 1943, Theoretical Soil Mechanics, John Wiley and Sons, New York