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CONTENTS

SERIAL NO TOPIC PAGE NO Introduction

History

Cement Test

Casting Yard

Geotechnical Interpretive Report (G.I.R)

Total GPS Station

Process of Bored Cast In-Situ Pile

Detailing of Pile

Clear cover

Use of Bentonite Solution

Flushing

Pile Reinforcement Cage Lowering into the Bore Hole Concreting of Pile

Pile Cap

Reinforcement Detail of a Pile Cap

Total Mechanism of Pier

Segment Launching

Gluing of Segment

Post Tensioning

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INTRODUCTION:

The Kolkata Metro or Calcutta Metro is a metro system serving the city of Kolkata and the districts of South and North 24 Parganas in the Indian state of West Bengal. It is the first Underground

metro railway system in India. The network consists of one operational line (Line 1) and one under

construction (Line 2), with four further lines in various stages of planning. It was the first such form of

transport in India, opening for commercial services in 1984. It is the 17th zone of the Indian

Railways system.

HISTORY: After Independence in 1947, the transport problem of Kolkata drew the attention of the

city planners, the state government and also the government of India. It was soon realized that something

had to be done and quickly in order to cope with the situation. It was Dr. Bidhan Chandra Roy, the then

Chief Minister of West Bengal, who for the first time conceived the idea in 1949, of building an

Underground Railway for Kolkata to try to solve the problems to some extent.

A survey was done by a team of French experts but nothing concrete came of this. Efforts to

solve the problem by augmenting the existing fleet of public transport vehicles hardly helped since roads

account for only 4.2% of the surface area in Calcutta, and this is compared to 25% in Delhi and even 30% in

other cities. With a view to finding out an alternative solution to alleviate the suffering of the Calcuttans,

the Metropolitan Transport Project (Rlys) was set up in 1969. The MTP (Rlys), with help of Soviet specialists

(Lenmetroproekt), prepared a master plan of providing five rapid-transit (metro) lines for the city of

Kolkata, totalling a route length of 97.5 km in 1971, but only three were selected for construction. These

were:

Dum Dum - Tollygunge

Salt Lake City - Ramrajatala (truncated till Howrah Maidan)

Dakshineshwar - Thakurpukur (route changed to Joka - BBD Bagh)

Of these, the highest priority was given to the busy north-south axis between Dum Dum and Tollygunge

over a length of 16.45 km, and the work on this project was sanctioned on 1 June 1972. The foundation

stone of the project was laid by Indira Gandhi, the then Prime Minister of India, on 29 December 1972 and

the construction work started in 1973-74. From the start of construction, the project had to contend with

several problems including, insufficient funds (until 1977-78), a shifting of underground utilities, court

injunctions, and an irregular supply of vital materials. Despite the difficulties faced, services began on

October 24, 1984, with the commissioning of a partial commercial service covering a distance of 3.40 km

with five stations served in between Esplanade and Bhowanipur. The first metro was driven by Tapan

Kumar Nath and Sanjoy Sil. The service was quickly followed by commuter services on another 2.15 km

stretch in the north between Dum Dum and Belgachhia on November 12, 1984. The commuter service was

extended up to Tollygunge on April 29, 1986 covering a further distance of 4.24 km making the service

available over a distance of 9.79 km and covering 11 stations. However, the services on the north section

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were suspended with effect from October 26, 1992, as this isolated small section was little used. After a

gap of more than eight years, the 1.62 km Belgachhia-Shyambazaar section, along with the Dum Dum-

Belgachhia stretch, was opened on August 13, 1994. Another 0.71 km stretch from Esplanade to Chandni

Chowk was commissioned shortly afterwards, on October 2, 1994. The Shyambazaar-Shobhabazar-Girish

Park (1.93 km) and Chandni Chowk-Central (0.60 km) sections were opened on February 19, 1995. Services

on the entire stretch of the Metro were introduced from September 27, 1995 by bridging the vital gap of

1.80 km in the middle.

In the final stage, the extension of Line 1 to an elevated corridor from Tollygunge to New Garia was

constructed and opened in two phases, Mahanayak Uttam Kumar to Kavi Nazrul in 2009 and Kavi Nazrul to

Kavi Subhash in 2010. The latest extension constructed was the 2.59 km elevated corridor from Dum Dum

to Noapara on 10 July 2013.

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The cement that are used in metro construction are undergone various test as

mentioned below:-

1) CEMENT TEST : As we know, testing of cement can be brought under two categories those are:-

I. FIELD TESTING.

II. LABORATORY TESTING.

But, in case of any constructional project field testing is not at all sufficient for assurance of the

quality requirement of the cement, so that the laboratory testing of cement will be necessary to have the

100% assurance of the quality requirement of the cement, the tests which are performed in laboratory are

:-

a) CONSISTENCY TEST.

b) INITIAL SETTING TIME TEST.

c) FINAL SETTING TIME TEST.

d) FINENESS.

e) COMPRESSIVE STRENGTH TEST.

f) SOUNDNESS TEST.

g) CHEMICAL COMPOSITION TEST.

a) STANDARD CONSISTENCY TEST:

For finding out initial setting time, final setting time, soundness and strength of cement

a parameter known as standard consistency has to be used, it is pertinent at this stage to describe the

procedure of conducting standard consistency test. The standard consistency of a cement paste is defined

as that consistency which will permit a Vicat apparatus having 10mm diameter and 50mm length to

penetrate to a depth of 33-35mm from the top of the mould .This apparatus is called the Vicat apparatus.

This apparatus is used to find out the percentage of water required to produce a cement paste of standard

consistency. The standard consistency of a cement is sometimes called normal consistency (CPNC).

Fig: Vicat apparatus for determining the normal consistency and setting time for cement.

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b) INITIAL SETTING TIME:

Initial time of Cement is the time required by the cement for its

early setting. Cement must be applied to the place of its use before its

initial setting so it is necessary to find out the initial setting time that is

available with us. The cement paste of normal consistency is formed and is

filled in the mould. Now the needle is made just touch the top surface of

the cement paste and made freely fall in it. Initial setting time is the time

from the mixing

of the cement and the water to the time when the penetration of the

needle is just above 5 mm from the bottom of the base plate or mould.

The period elapsing between the time when water is added to the cement

and the time at which the needle penetrates the test block to a depth

equal to 33-35mm from the top is taken as initial setting time. Fig: Vicat apparatus and accessories

Generally the initial setting time of the ordinary Portland cement is 30 minutes. For Slow setting cement this time may be increased by

Adding the admixtures or Gypsum up to 60 minutes.

c) FINAL SETTING TIME:

Place the test block and the non- porous plate under the rod bearing the

needle with the annular attachment for final setting time. Lower the needle gently till the needle makes an

impression there on, while the attachment fails to do so. In the beginning the needle will completely pierce

the block. Repeat the procedure. The period elapsing between the time when water is added to the

cement and the time at which the needle fails to make an impression on the surface of the test block shall

be the final setting time. In other words the paste has attained such hardness that that the needle does not

pierce through the paste more than 0.5mm.

d) FINENESS TEST:

This experiment is carried out to check the

proper grinding of cement. The cement which is produced by

an industry is checked for its quality, that either it is good for

certain type of construction or it doesnt possess that much

strength. For example, for RCC and other heavy load bearing

structures such as bridges it is essential that the cement

which is being used in the concrete should have the ability to

provide the required strength, while in the PCC structures it is

not so much critical.

Fig: Set of sieves used for Fineness Test.

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The ability to provide strength of a certain type of cement is checked by finding the fineness of

that cement, because the fineness of cement is responsible for the rate of hydration and hence the rate of

gain of strength and also the rate of evolution of heat. If the cement is fine then greater is its cohesiveness,

which is the property, required in the concrete because it gives compactness to the concrete. Usually

cement loses 10% of its strength within one month of its manufacturing. Fineness is tested in two ways

1. BY SIEVING.

2. BY DETERMINATION OF SPECIFIC SURFACE BY AIR-PERMEABILITY APPARATUS.GENERALLY

BLAINE AIR PERMEABILTY APPARATUS IS USED.

But here in the project, we have only showed the sieve test to find the fineness of the cement.

SIEVE TEST:

Weight correctively 100 gms of cement and take it on a standard IS Sieve NO.9

(90 MICRON). Break down the air set lumps in the sample with fingers. Continuously sieve the

sample giving circular and vertical motion for a period of 15 minutes. Weight the residue left on the

sieve. This weight shall not exceed 10% for ordinary cement.

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e) COMPRESSIVE STRENGTH OF CEMENT:

The compressive strength of hardened cement is the most

important of all the properties. Therefore, it is not surprising that the cement is always tested for its

compressive strength at the laboratory before the cement is used in important works. Strength test are not

done on neat cement paste because of difficulties of excessive shrinkage and subsequent cracking of neat

cement. Strength of cement is indirectly found on cement sand mortar in specific proportion. The cubes

are prepared for this purpose. The cubes are then tested in compression testing machine at the end on

three days and seven days. Testing of cubes is carried out on their three sides without packing. Thus the

cubes are tested at each time. Take 555 gms of standard sand, 185gms of cement (i.e. Ratio of cement to

sand is 1:3) in a non-porous enamel tray and mix them with a trowel for one minute. Add water quantity

(P/4 + 3.0) % of combined weight of cement and sand and mix the three ingredients thoroughly until the

mixture is of uniform colour. The time of mixing should be less than three minutes and not more than four

minutes. Immediately after mixing fill the mortar into a cube mould of sizes 7.06cm. Immediately after

mixing fill the mortar into a cube mould of sizes 7.06cm. Compact the mortar either by hand compaction in

a standard specified manner or on the vibrating table. Place the moulds in cabin at a temperature of 27

2 C for 24 hours. Remove the specimen from the moulds and submerge them in clean water for curing.

f) SOUNDNESS TEST:

Soundness of cement is determined by Le-Chatelier method as per IS: 4031

(Part 3) 1988. Apparatus The apparatus for conducting the Le-Chatelier test should conform to IS:

5514 1969.

Balance, whose permissible variation at a load of 1000g should be +1.0g and

Water bath. Place the mould on a glass sheet and fill it with the cement paste formed by gauging

cement with 0.78 times the water required to give a paste of standard consistency. Cover the mould

with another piece of glass sheet, place a small weight on this covering glass sheet and immediately

submerge the whole assembly in water at a temperature of 27 2oC and keep it there for 24hrs.

Measure the distance separating the indicator points to the nearest 0.5mm (say d1) Submerge the

mould again in water at the temperature prescribed above. Bring the water to boiling point in 25 to 30

minutes and keep it boiling for 3hrs.

Remove the mould from the water, allow it

to cool and measure the distance between

the indicator points (say d2). (d2 d1)

represents the expansion of cement.

Fig: Le-Chatelier apparatus for finding soundness test.

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2) CASTING YARD:

Fig: CASTING YARD OF A METRO RAIL

In recent technology as metro goes over the ground surface due to economical reason, the construction process which is used in the metro project is PRE-CAST SEGMENTAL CONSTRUCTION.

Balanced cantilever construction is an economical method when access from below is expensive or

practically impossible. The cross-section is normally a box. Segments may be cast in-situ or precast.

Construction starts from the top of a pier, with the segment normally fixed to the pier either

permanently or temporarily during the construction. (Construction can be carried out from an

abutment provided there is a balancing weight to counteract the segments in the span.

Subsequent segments are post-tensioned to the previous sections on alternate sides of the pier

so that the out-of-balance moment is kept to a minimum. A temporary support is sometimes added on

one side of the pier; if the pier/deck connection is fully fixed this is not necessary.

In segmental balanced cantilever construction the precast segments are transported to the

bridge and placed and held at the right position before post-tensioning back to the rest of the bridge. A

moving gantry with lifting capability for the heaviest segment is required to lift and hold the segment in

position. The precast segments normally have a shear key and match cast in a casting yard.

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Epoxy resin is normally used in the joint. In this process the one span distance between one

pier to another is divided into some specified length of segment, which are as follows:

a) S1-length is 1.95m(Generally taken as 2)

b) Other segments are namely S2, S3, S4, S5, S6, S7 and all are of same length i.e., of 3m.

The length of a span may be of several length like (22, 25, 28, 31, 34, 37, 40, 43) metres etc. In this

project maximum span length which is used is of 34m.The span distribution by segment is made in such a

way i.e. In case of 34m, span distribution is:-

[S1(2M)+S2(3M)+S3(3M)+S4(3M)+S5(3M)+S6(3M)+S5(3M)+S4(3M)+S3(3M)+S2(3M)+S1(2M)]

This segments are precasted in the casting yards and then move to the project site to construct the span.

S1, S2, S4 requires different casting mould where S2 AND S4 requires same casting mould due to a

component called future prestressing part. But all the other segments like S3, S5, S6 and S7 require same

mould for casting.

First the segment mould is set then the reinforcement cage of steel is driven into the mould and the

reinforcement cage is made as per as R.C.C design drawing mentioned, then a specified graded concrete

like M-35, M-40 etc. are filled into the cage and then shuttering are provided on the mould and left it

10days for setting, then the completed segments are joined with candle as per span distribution, which is a

temporary joining called matching of one segment to the next one. It is required to ensure and also to

make good permanent joining with glue during erection of segment in the site.

A head, is attached with every casting mould to provide the segments the anchor head, is called bulk

head, without this anchor head, the segments cant be joined with each other.

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3) GEOTECHNICAL INTERPRETIVE REPORT (G.I.R):

GIR is a report which contains the whole geotechnical investigation of soil taken from the project site by making bore hole and by using standard penetration test.

The standard penetration test (SPT) is an in-situ dynamic penetration test designed to provide

information on the geotechnical engineering properties of soil.

A thick-walled sample tube is used in preforming this test, with an outside diameter of 50 mm

and an inside diameter of 35 mm, and a length of around 650 mm. This is driven into the ground at the

bottom of a borehole by blows from a slide hammer with a mass of 63.5 kg (140 lb) falling through a

distance of 760 mm (30 in). The sample tube is driven 150 mm into the ground and then the number of

blows needed for the tube to penetrate each 150 mm (6 in) up to a depth of 450 mm (18 in) is recorded.

The sum of the number of blows required for the second and third 6 in. of penetration is termed as the

"standard penetration resistance" or the "N-value". In cases where 50 blows are insufficient to advance it

through a 150 mm (6 in) interval the penetration after 50 blows is recorded. The blow count provides an

indication of the density of the ground, and it is used in many empirical geotechnical engineering formulae.

The main object of this test is to collect the undisturbed soil 450mm below the ground

surface and finally to find the sand layer, at that surface which is ideal layer to rest down the concrete pile.

The purpose of this test is to provide an indication of the relative density of granular deposits,

such as sands and gravels from which it is virtually impossible to obtain undisturbed samples. The great

merit of the test, and the main reason for its widespread use is that it is simple and inexpensive. The soil

strength parameters which can be inferred are approximate, but may give a useful guide in ground

conditions where it may not be possible to obtain borehole samples of adequate quality like gravels, sands,

silts, clay containing sand or gravel and weak rock. In conditions where the quality of the undisturbed

sample is suspect, e.g. very silty or very sandy clays, or hard clays, it is often advantageous to alternate the

sampling with standard penetration tests to check the strength. If the samples are found to be

unacceptably disturbed, it may be necessary to use a different method for measuring strength like the

plate test. When the test is carried out in granular soils below groundwater level, the soil may become

loosened. In certain circumstances, it can be useful to continue driving the sampler beyond the distance

specified, adding further drilling rods as necessary. We also identify the colour of the soil, 5% of sand, silt

and clay and in the lab using unconfined compression test (UCT), consolidation test and triaxial

compression test, we find the cohesive strength of each layer.

Finally we use all the above notification through appropriate specified way by making some column and

nomenclature in a page and in this way, we make the GEOTECHNICAL INTERPRETIVE REPORT (GIR) before

the project to start.

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4) TOTAL GPS STATION: The Term GPS stands for Global Positioning System. The GPS is used to locate a

location with the help of Latitude and Departure with the help of GPS it's possible to locate a point very

precisely. GPS consist of two main ends, the one is the Locating Satellites and the other is the Receiver.

Most of the people now a days are familiar with GPS due to the

huge use of Smart Phones.

Global Positioning System was first evolved for

the defence of countries, and it's controlled from the California. It

was used for locating various places which are important from the

Defence point of view. Later on it was opened for public use. But

the Same GPS System with more powerful receivers it can be used

in the Civil Engineering Field.

This System provides us with accurate horizontal

and vertical measurements and gives us the position of observer in

terms of Latitude and Longitude.

Advantages:

This system is fast replacing with conventional methods of

surveying like Triangulation, Traversing etc.

It no longer requires the inter-visibility of station points. The

conventional techniques are still required for detail surveying.

The horizontal and vertical control can easily be

Established with the help of GPS. Fig: Total GPS station.

Instrument:

This system basically requires the receiver which is setup at the point of observation. The

second part of the equipment is no of satellites which are 18, launched into 6 different orbits. Each orbit

have three satellites with 120 degrees interval. The height of satellite is about 20,000 km with orbiting

velocity of 11hr 58min.

Procedure:

The GPS position is achieved by the precise measurement of the distance between the satellite &

the receiver at an instant of time.

For a three dimensional measurements three or four satellites will be needed depending upon the

quality of receiving equipment.

It requires highly accurate clocks both in the transmitter and in the receiver to measure the precise

distance between them.

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Applications:

This system gives us the accurate geographic position required for land surveying.

It is used for navigation purposes in Aircraft, Ships and Submarines etc.

It is now exceedingly used to locate the enemy targets and subsequently hitting them by GPS

information guided missiles.

For public use simpler version are available for locating the vehicles, the individuals and the parties,

in hiking and mountaineering expeditions and other number of applications.

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5) PROCESS OF BORED CAST IN-SITU PILE:

INTRODUCTION:

At first pile centre is considered by taking the reference from the pier centre, the hole

boring is started at that mentioned specified place after centring the pile after about 3-4 m of boring

completion, a cylindrical shaped iron case is driven into the hole by Casagandra de apparatus, which is also

needed first to make the hole, after the completion of casing again the hole boring is started and

continued up to the specified shaft length of that particular pile. The length between the founding level

and the cut off level of a pile is known as shaft length of a pile.

BENTONITE SOLUTION:

After placing of casting into the hole, a solution called Bentonite solution is poured

into the hole through a pipe which is driven through the top of the casing. Bentonite is an absorbent

aluminium phyllosilicate, impure clay consisting mostly of montmorillonite. There are different types of

bentonite, each named after the respective dominant element, such as potassium (K), sodium (Na),

calcium (Ca), and aluminium (Al). Experts debate a number of nomenclatorial problems with the

classification of bentonite clays. Bentonite usually forms from weathering of volcanic ash, most often in the

presence of water. However, the term bentonite, as well as a similar clay called tonstein, has been used to

describe clay beds of uncertain origin. For industrial purposes, two main classes of bentonite exist: sodium

and calcium bentonite.

Three tests are to be performed before using it in the work, due to check the quality requirement,

those are as follows:-

a) DENSITY TEST

b) VISCOSITY TEST

c) PH-LEVEL TEST

o DENSITY TEST: Density test of bentonite is necessary and is

done using hydrometer apparatus, at first the bentonite is

poured into a cylindrical shaped measurable jar and the let

the hydrometer to suspend into the solution in this way the

hydrometer will give the density of bentonite which must

not exceed 1.07g/cc.

Fig: Hydrometer Apparatus.

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o VISCOSITY TEST:

It is also required to check the quality reinforcement of the bentonite solution, there is a

specified funnel to measure the viscosity of the solution. At first the small diameter hole end of

the funnel is made close by using the finger and then the bentonite is poured into the funnel up

to the top and is filled completely. The remove the finger and let the bentonite to fall from the

tunnel and at the same time a stopped watch is started to note the elapsed time between the

time when the bentonite is allowed to fall and the time elapsed when bentonite is completely

fallen through the funnel. The time should not exceed 30 seconds. We find this value at the

project side 22 seconds.

o PH-TEST:

Ph. test is also necessary for the quality requirement of bentonite, as we know, by knowing the

ph value we can determine that whether the solution is acid or alkali. If the ph value is >1 &

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6) DETAILING OF PILE:

Reinforcement detailing of pile is done as per as provided by designer, i.e. the designer

provide the r.c.c design drawing and then as per the drawing pile reinforcement cage is exactly made

(made in yard). Pile reinforcement cage consists of some vertical main steel bars and the horizontal

stirrups. In this project the pile is designed with 18mm diameter bars in 12 nos. as vertical reinforcement

and 8mm diameter stirrup bars in whole bottom to top of the pile cage as shear reinforcement. As the

natural length of a vertical steel bar is 12m hence to produce a 30 m, they have to join one bar with the

other one vertically using welding process and the joining is called lap joint/lapping. As per I.S code

maximum allowable lap joint is 76D [where, D is the diameter of the steel bar]. Lap joint is provided using

alternative way of leaving one bar after another. A thick diameter circular bar is provided at the joint to

give shear strength at that part.

Within the vertical bars 4 bars of 20 mm diameter are provided in the project and it is done

usually to transit the excess load to the earth and it is known as earthing bars. At the top of the pile cage

the horizontal stirrups are provided in many numbers at 90mmc/c, it is due to resist the seismic effects

which are provided during earthquakes or any kinds of soil vibrations at that layer, just below the ground

surface, it is provided upto a specified length from the top towards the bottom as per design drawing

mentioned, otherwise after that part the stirrups are provided @ 250mmc/c more or less upto the bottom

of the pile cap.

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7) CLEAR COVER:

A circular motor made clear cover of diameter 150mm is provided in the pile reinforcement cage. A small hole is made at the centre of the clear cover and let the horizontal stirrups get

through that hole. This clear covers are provided the whole the pile cage from bottom to top. In this way

the half dia. of the clear cover i.e. the one radius stand inside the pile cage and the other half diameter

outside the cage. This is done due to two reasons-

Fig: Clear cover

a) The half part of the clear cover inside the pile cage provide the steel bars to make good bonding

with the concrete, so that the concrete and steel bonding become strong enough.

b) The half part of the clear cover outside the pile cage provide the steel cage to go into the bore hole

without making any inclination with the vertical axis, i.e. to provide the exact centering of the pile

cage and also to fit in the hole exactly without any difficulty. It also saves the bars from the moisture

which is struck at the inner side of the hole.

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8) USE OF BENTONITE SOLUTION:

A very fine grained powdered material

called bentonite is used for the purpose of flashing the

bore hole after the required length of boring is completed.

The powdered bentonite is first mix with water with a

specified proportion and thus the bentonite solution is

made is made to pour into the bore hole through

cylindrical plastic made pipe which I fixed at one end to

the outlet tap of the bentonite containing truck and the

other end is left open into the bore hole.

Fig: Bentonite solution

The reason of using bentonite into the bore hole is to resist the tripping of soil from the hole side into

the bottom of the bore hole.

The bentonite solution has a density less than water and greater than air and so it makes a

membrane over the soil of the hole side so that the loose soil cannot fall at the bottom of the hole. The

bottom does not get collapsed and the required pile shaft is thus maintained.

9) FLUSHING: Flushing is the process of taking out the

same proportion of the collapsed soil from the bottom

of the hole to the out of the hole by pouring the

bentonite solution from the bottom to the top of the

hole and thus the whole collapsed soil is flushed out

from the bottom of the bore hole. Thus the accurate

value of pile shaft is maintained.

Fig: Bentonite Flushing

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10) PILE REINFORCEMENT CAGE LOWERING INTO THE

BORE HOLE: Using the crane the bottom pile cage

is first lifted and then the cage is lowered into the hole

properly and keep some top portion of the cage outside

the hole by using a support which keep the cage at

suspending condition into the hole, then the top pile

cage is lifted by the crane and bring it to that portion of

the bottom pile cage which is kept outside the hole and

then the bottom portion of the top pile cage and the top

portion of the bottom pile cage are welded properly

maintaining the 76D condition and the stirrups along the

clear cover are also provided to that welded portion. The

support is moved and whole pile cage is lowered into the

hole.

Fig: Lowering of a cage into bore hole

11) CONCRETING OF PILE:

After flashing is completed, an iron made pipe called trimming pipe is driven into the bore hole.

One single trimming pipe is about 4m in length and so a number of pipes is fixed with each other

to get the required length of the pile shaft length. The trimming piles are fixed using a chain and range. The

chain is first bind around the pipe then tightened with the range and then rotates 360 degrees to fix one

pipe to another.

Then a specified graded concrete, here we used (M-40) grade concrete which is made in the

batching plant and then the mix concrete is transported from the batching plant to the site through miler

vehicle. Then the funnel is placed over the last pipe which is out of the ground. after funnel is placed over

the funnel hole before the concrete is poured into the hole to avoid the making of void within the concrete

so that it cannot choke the trimming pipe, this process is called charging.

The cover plate is removed from the funnel hole and the miler outlet is accurately brought over

the funnel opening end, over the ground, then the concrete is poured at a length of 5-6m above the

bottom of the hole and soon after one single trimming pipe is removed from the top so that at least 1-2m

length of the last pipe should remain immerged into the concrete which is already poured into the hole.

Thus the concrete is poured to the top of the bore hole and along with one pipe is removed from the top.

Thus the concreting of pile is done at the site.

The whole process of construction of the pile is known as the process of cast in-site pile construction.

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12) PILE CAP:

Definition:

A pile cap is a thick concrete mat that rests on concrete or timber piles that have been driven into soft or unstable ground to provide a suitable stable foundation. It usually forms part of the foundation of a building, typically a multi-story building, structure or support base for heavy equipment. The cast concrete pile cap distributes the load of the building into the piles. A similar structure to a pile cap is a "raft", which is a concrete foundation floor resting directly onto soft soil which may be liable to subsidence .

Design:

A geological survey must be carried out first to establish the stability of the proposed site for the support cap. The cap thickness will be determined by the load that it has to support and the number of piles used to distribute the load into the underlying soil. Other considerations, such as any localised loading that any part of the mat must support are taken into account.[2] Some soil is so fluid in nature (such as clay and sand), that screw shaped piles are used, these resist the tendency for the pile to sink under the added weight of the cap and the load placed upon it. Standard engineering practice is followed with regard to the square area of the cap, thickness, and its design loading. From a set of appropriate calculations the sizes will be determined and the quantity of concrete required calculated.

Construction:

The mat is made of concrete which is an aggregate of small rocks and cement. This mixture has to be supported by a

framework to avoid sagging and fracture whilst setting. This process is known as shuttering and reinforcing. The materials used are long twisted steel bars between the piles held in shape by thinner tie wires. Once this steel mat is laid, timber is attached around the perimeter to contain the wet concrete mixture. Once poured, (usually as a series of small loads), the concrete is stirred to remove any air pockets that might weaken the structure when set. The concrete undergoes a chemical change as it hardens and this produces a lot of heat. Sometimes, if the mass of concrete is very large, pipes carrying refrigerant coolant are used in the mass to assist the setting process to prevent the concrete from cracking.

13) REINFORCEMENT DETAIL OF A PILE CAP:

The pile cap reinforcement is done by designer as per requirement. Basically the reinforcement

cage is looked like a 3D rectangular box. The reinforcement bars provided along the X-axis are known as

horizontal reinforcement and the bars provided along the transverse direction are called transverse

reinforcement.

Then according to the number of pile and also the position of the pile over which the particular pile cap will

be fixed are marked on the pile cap reinforcement box through the bars. Which are bend circularly at the

same diameter of the pile and also maintaining the same spacing of each file from each other, by fixing

these with the pile cap cage by welding.

Then the pile cap is moved over the particular set of piles for which it is designed and before this, each pile

are chiselled out to its cut off level few inches below the ground level, so that each pile reinforcement can

be extended to the ground and pile cap can be made exactly over this reinforcement. The pile

reinforcement bars are cut to the marking points (as mentioned in the design) of the pile cap. The pier

reinforcement cage is connected to pile cap cage following the same process as done in pile

reinforcement.

20

14) TOTAL MECHANISM OF PIER:

The pier centre is taken with respect to each pile centre over which it will be constructed. The pier

reinforcement cage is embedded into the pile cap reinforcement cage and then welded, followed by

shuttering around the pier reinforcement. Pedestal reinforcement is made at the four corners of the pier

cap, and then shuttering takes place.

A special arrangement at the centre over the pier cap is prepared which is called Shear Box. It serves an

important purpose which are as follows:-

When the metro rail travels over the track, a horizontal component force is created in the

pier which is restricted by these shear block.

At the time of earthquake the seismic force gets transmitted to the pier from the soil,

experiencing certain jerk in the pier which also gets transmitted to the girder. In order to

avoid this dislocation a special offset is provided.

Another important aspect of shear box is pipe channel provided during the construction,

whose outlet is made in the bottom side of the pier and inlet at the mouth of the shear box

so as to drain out the rain water from the pipe channel collected at the segment.

Process of checking the centering of the pier from GPS

station using the instrument TOTAL STATION:

Total Station is nothing but advanced Theodolite instrument, which has some advance technology

compared to the Vernier Theodolite.

It has a digital display screen at the top which shows the distance of the target object along with its bearing

from a particular reference point.

First, the instrument is centred over the reference point, which is a GPS station, by using the same process

of bubble centring in the Theodolite. When the cantering is done, then one person will hold the prismatic

staff at the centre on the top of the constructed pier. The staff has a cross on the prismatic screen, now

another person, who is operating the total station, has to target the centre of that cross-hair centre of total

station lens.

Then the distance & bearing is noted down for that position, then the instrument is moved from that

position towards the GPS station with an interval of 2m from the current GPS station. The instrument is

then again centred by the same process. Then, the previous GPS station is targeted using the prismatic

staff by the same process and observations are noted down, it will be the reference point for the current

station. The instrument is then rotated from that bearing value of the reference point to the centre of the

pier. Again one person will hold the staff at the centre on the top of pier and another will target that

through the instrument, the centre of the cross of the prism screen is again targeted through the centre of

cross-hair of Total Stations lens. The distance & bearing value is deducted to get the actual bearing value

of the pier centre from the GPS station. This process of checking is carried out for all GPS station for

respective pier near the GPS stations.

21

15) SEGMENT LAUNCHING:

Introduction:

After a days production, the previous days match cast segment is ready to be finished and set for

storage. Depending on the design, some segments can be lifted and placed in storage prior to any post-

tensioning. This will be a factor of strength gained during the initial cure of the segment and the

dimensional properties of the bridge. Otherwise some design post-tensioning will be needed in the casting

cell prior to load out.

An organized storage plan must be formulated early in the casting process. Not only should the

location of each segment be established in an orderly manner for storage, but also for documenting the

various stages of completion and acceptance, as well as, availability to deliver the segments to the bridge

site when needed. Time and efficiency losses caused by searching for segments will add up quickly

especially if multiple movements are needed for access.

While in storage any pointing, patching, and architectural finishes can be applied (care must be

taken when any repairs are made to the match-cast face to ensure the fit is not jeopardized). The post-

tensioning rods and strands are stressed, anchored, and grouted. The Anchorages are sealed and poured

back with like concrete. Any bond-breaking agents applied during casting must be power-washed off and

the match face must be clean.

Loading and Transporting:

Depending on the location of the storage area to the bridge erection site, the method of

transportation will differ. Whether it is by trucks (on and off road), rail, or barge, several factors apply to

all: hauling restrictions time and weight, permits, environmental and noise ordinances, and distance. The

most direct routes might not be the most cost effective or available. A necessary decision will also include

whether to purchase, rent, or subcontract the loading and transporting. The lifting and handling of these

large castings is specialized work and any errors can be catastrophic therefore, the services of

professionally experienced subcontractors are advised.

Note: the segments must be transported to the bridge for erection in the same relation as they were cast.

22

Precast match-cast structures are usually associated with superstructure elements in bridge

construction but where economy of scale, scheduling, and access issues support the use, this method of

construction is very effective for substructure pier elements.

The construction for piers is very similar to the deck except the segments are stacked vertically then

anchored to each other and the foundation with a vertical post-tensioning system.

Although they are usually cast-in-place and not precast, the erection process begins with the pier

footings. Ductwork and anchors must be cast in the footing for the post-tensioning system. High strength

rods are used in the epoxy squeeze activities and draped tendons (high-strength steel cables or

strands) are used for the permanent compressive loads required to join the individual segments together

in order to act as a single pier unit. Finally, a keyway is recessed in the top of the footing to receive the first

or base segment.

The base segment is set in the recess of the footing, and shimmed to line and grade.

The post-tensioning ductwork and embeds from the footing are lined-up through the recess

continuing into the segment with a grout tight connection. Lastly, the rest of the recess void is filled with

grout, then the grout is allowed to set, and when strength is approved, erection is continued with

subsequent segments.

23

After the grout has achieved the required strength, the intermediate segments can be erected with

the following procedure:

1. Place epoxy on match-cast faces (epoxy acts as a lubricant and sealer to facilitate a tight fit

between segments),

2. Connect high strength rods between segments,

3. Lower the segment onto the top of the previous segment,

4. Stress rods to provide epoxy squeeze to seat the segments to their match-cast (this step is

performed every one to three segments placed),

5. Check survey control for line and grade on multiple faces to control plumpness and rotation,

6. If survey shows any signs of deviation from the as-cast geometry the next segment will need

shimming to correct the error,

7. Repeat procedure to cap segment. Any epoxy that oozes or drips out during the squeeze will

need to be cleaned (check the post-tensioning ductwork for epoxy that squeezes into the duct

and restricts the diameter).

The ducts for the rods can be grouted as the erection proceeds but this is a time consuming step.

Most times access is provided to grout the rods once fully erected.

Production rates of six segments per day can be regularly achieved; this is dependent on shimming

and other quality control issues.

The last steps are the erection of the pier cap section, permanent post-tensioning, and setting of

bearing pads. Setting the pier cap segment is very similar to the intermediate segments. Steps 1 through 5

above are followed with any survey deviations accounted with revised bearing pad locations. Since the cap

contains the anchorages for the post-tensioning tendons and is the seat to support the spans, it must be a

massive segment in proportion to the other segments of the pier. This means it will be the heaviest and

tallest pick of the pier and therefore the most difficult to set. Once the segment is set, the post-tensioning

strand can be installed. The strand is threaded through the ducts making a loop down the pier through the

footing and back up the pier. Depending on the design, the number of strands per duct and the number of

ducts per pier will vary and a stressing sequence will be provided in order to transfer a uniform load. The

strand is stressed using high strength hydraulic jacks. When the jacks reach the required pressure

(compressive loads will be calculated in terms of hydraulic pressure in the jacks) the strands will be

anchored in places with wedges to retain the loaded energy. The stresses applied to the strand will stretch

the steel. Elongations will be measured to ensure the stresses occurred over the entire length of the strand

(a shortened elongation will mean the strand is pinched somewhere along its length and repairs may be

necessary). The ducts are then pressure grouted to both protect the strand from corrosion and to

permanently contain the stresses from the jacks. Concrete is then poured around the anchor blocks for

further corrosion protection. Lastly, a final survey is performed and the bearing pads are set per the

asbuilts .

Other precast concrete items found in bridge substructures include: concrete piling, precast

cofferdams, pile cap soffits, and pier bent headers or caps.

24

Superstructure Erection Span by Span Method:

Span by span superstructure erection is a method of construction where the span

elements are temporarily held in place until they are self-supporting and once capable of self-support the

erection procedure advances to the subsequent span. The completion of one span at a time is the defining

character for which the name span-by-span is derived from. This method is very repetitive and can be

economical for spans ranging from 80 to 180 feet (150 ft. spans are generally accepted as the most

economical span length based on typical substructure types vs. typical truss). As with the previous sections

of the course, efficiency is gained due to the repetitive assembly line nature of the work. Items that can

affect productivity include: variations in span length and especially span height, the terrain being spanned

(land vs. water, urban or industrial vs. open areas), and changes in alignment (curves and transitions).

In order to make this erection method as efficient as the name span by span would imply, the operations

have been simplified to become repetitive. This however is aided/accomplished with some very specialized

equipment. First the segments of the span must be temporarily held in place until they are self-supporting.

Common temporary structures used for this function are: individual shoring towers, underslung carrying

devises like trusses or box beams (these can support the segments under the soffit or under the wing (only

if the segments are designed with a cantilever wing support condition)), the trusses can be supported from

erected towers or brackets at the piers, or an overhead gantry can hang the segments from above. Second

the segments must be lifted into position on the temporary supports. Where access permits, ground based

or barged cranes can be used to lift the segments. Excessive heights or height restrictions may limit the use

of cranes so specialized gantry transports have also been used. Lastly, rollers, jacks, winches, cable pushers

and taggers, stressing platforms, and C-brackets are a partial listing of miscellaneous equipment and

fabrications that need to be procured prior to beginning the erection.

25

To begin erection, the support structures must be erected. If individual shoring towers are used, the

ground must have a suitable bearing capacity, if not, stabilize with stone and/or use crane mats. If an

underslung truss or overhead gantry is used, erect supports at piers and place truss to the correct line and

grade off the pier supports. The length of the underslung or overhead trusses will need to be twice the

structures span length if they are to be self-launching, otherwise they can be shorter if a crane will be used

to pick and set them in place at each span.

The procedures for the end spans are slightly different because of the location of the abutment

stem and back wall, but for typical mid-spans the first step is to load segments on to the supports (assume

underslung truss for narrative) starting from one location and launch them longitudinally to their

approximate location. Typically the segments are set from the down station end and are rolled up the truss

(using Hillman rollers or alternate methods of launching) so the span segments need to be delivered in

reverse order (last span segment firstfirst span segment last). Fully load the truss with all of the span

segments prior to surveying to allow the truss deflection to occur. Survey and align segments for line and

grade making sure chord offsets are correct for curved structures.

Next the segments will be aligned to the bridge geometry and joined. Sometimes it is helpful to

dry fit the segments together before epoxy joining, especially if the epoxy is a rapid set type. This is usually

an unnecessary step if adequate survey control was used in the casting yard during the match casting. A

gap should be left between segments over the piers and the mid segments of the span. This gap will be

closed with cast-in- place concrete as a closure pour to correct any unaccounted field conditions.

26

This will help ensure that errors wont be cumulative through the structure but rather each span will

start as corrected to the proper line and grade. After epoxy is applied to the match cast faces, apply

pressure with temporary high strength rods for an epoxy squeeze to seal the joints (the epoxy is used as

a lubricant/sealant to aid construction and increase long term durability of the structure). Last complete

the closure pours to make the span continuous.

After the setting and joining of the span is complete, the post-tensioning operations will begin.

Install permanent internal and external post-tensioning strand and rod longitudinally through the span.

Similar to the post-tensioning of the previous section (horizontal post-tensioning rather than vertical), the

number of strands per duct and the number of ducts per span will vary and a stressing sequence will be

provided in order to transfer a uniform load. The strand is stressed using high strength hydraulic jacks.

When the jacks reach the required pressure (compressive loads will be calculated in terms of

hydraulic pressure in the jacks) the strands will be anchored in places with wedges to retain the loaded

energy. The stresses applied to the strand will stretch the steel. Elongations will be measured to ensure the

stresses occurred over the entire length of the strand (a shortened elongation will mean the strand is

pinched somewhere along its length and repairs may be necessary). The ducts are then pressure grouted

to both protect the strand from corrosion and to permanently contain the stresses from the jacks.

Concrete is then poured around the anchor blocks for further corrosion protection.

After post-tensioning, the span is self-supportive and complete. The trusses and other support

devices are advanced to the next span to be erected and the process is repeated. Trusses can be advanced

with cranes using a pick, move, & place method or can be self-launching using a launch, slide, & pivot

method. Note: Design and manoeuvring of trusses through curved spans takes tremendous consideration

and potential losses in time and efficiency are significant if not properly planned.

27

Fun Facts from the Internet:

The first segmental concrete bridge, built in 1950, was cast-in-place across the Lahn

River in Balduinstein, Germany.

The first precast segmental concrete bridge, built in 1962, crossed the Seine River in

France

Eugne Freyssinet (13 July 1879 8 June 1962) was a French structural and civil

engineer and was the major pioneer of prestressed concrete

Hoover Dam Bypass has the worlds tallest precast columns.

Longest Cable Stayed Bridge Span in the world is the Sutong Bridge in China - 3,570

ft, Longest in United States is the John James Audubon Bridge 1,583 ft Highest

Cable Stayed Bridge Baluarte Mexico 1,321 ft in height

16) GLUEING OF SEGMENT:

CHOOSING THE RIGHT RESIN EPOXY RESIN

Epoxy Resins are thermosetting resins, which cure by internally generated heat. Epoxy systems consist of

two parts, resin and hardener. When mixed together, the resin and hardener activate, causing a chemical

reaction, which cures (hardens) the material.

Epoxy resins generally have greater bonding and physical strength than do polyester resins. Most epoxies

are slower in curing, and more unforgiving in relation to proportions of resins and hardener than

polyesters. Superior adhesion is important in critical applications and when glassing or gluing surfaces

such as steel, redwood, cedar, oak and teak as well as other non-porous surfaces.

Evercoat Epoxy resins are superior to polyester resins in that they impart exceptional strength in stress

areas. Epoxies will adhere to surfaces where polyesters may ruin them. Examples of areas where epoxy

resins products must be used are redwood, hardwoods, Styrofoam, some plastic surfaces, and metal. They

are generally higher in cost than polyester resins. Epoxy resins may be mixed with various fillers to thicken

them for special applications.

Fig: Application of epoxy glue between Fig: Epoxy glue

Segments.

28

In working with epoxies, the resin to hardener ratio is very important and should never be adjusted in an

attempt to slow down or speed up the curing process.

EPOXY RESIN IS IDEAL:

Where superior adhesion is necessary; Evercoat epoxies will bond permanently to wood, fiberglass,

metal, concrete, glass, and many plastics

As a tough coating for protection on window sills, concrete floors, stair treads, shower stalls, and

down spouts.

To protect metal from rusting.

To repair gutters, drain pipes (metal or plastic), pools, roofs, boats, decks, and auto bodies.

To repair blister problems on fiberglass surfaces, i.e. blistering on fiberglass boat hulls.

To repair aluminium boats and equipment.

TYPES OF EVERCOAT EPOXY RESIN:

EVERFIX RESIN (100642, 100643) A 1:1 mixing ratio epoxy resin. Performs superior as a finish-coating on the repair projects. This resin is thicker than EVERSTAR resin. One application of EVERFIX is equal to 50

coats or varnish. Can be used as an adhesive, excellent in decoupage systems, in fiberglass boat repair,

wood repair and many general repairs. Everfix resins are not listed under the code of Federal Regulations

(21 CFR), and, therefore, cannot be used for food contact applications.

POLYESTER RESIN VERSUS EPOXY RESIN

Characteristics Polyester Resin Epoxy Resin

Flexural Strength Good Best

Tensile Strength Good Best

Elongation % Good Lowest

Water Absorption Good Lowest/Excellent

Hardness Good Best

Pot Life 4 7 Minutes 14 20 Minutes

Working Time 20 30 Minutes - 6 Hours

Above Waterline Yes Yes

Below Waterline Yes Yes

Major Construction Yes Yes

General Repairs Yes Yes

Shelf Life 18 24 Months 2 Year +

Catalyst MEKP 2-Part System

Cure Time 6 8 Hours 5 7 Days

29

Mixing the Material

Carefully measure both Part A and Part B of the epoxy resin in the

separate measuring containers. Combine both parts in a third container,

making sure to scrape all sides thoroughly. The proper mixing ratio is

critical to ensure complete and uniform cure. ). Please note that

proportions of epoxies are parts by volume not by weight. Epoxy

hardeners do not disperse and mix easily into the resin side. When mixing

epoxies, the two-cup method should be used. Measure and stir

vigorously. Be sure to stir into the corners of the container, scraping the

sides, bringing it up from the bottom to be mixed. Never mix more than a

quart at a time as it starts setting up in about hour and should not be

used after it starts to gel.

Take care to mix in all directions, and scrape sides, and bottom of

container. Note: Improperly mixed product will cause curing problems.

If air is whipped into mixture it, it must be removed before curing. To

remove large air bubbles at the surface simply prick them with any sharp

object, such as a toothpick, or paper clip. Smaller clusters of air bubbles

can be removed by passing a blow dryer or heat gun 6 to 10 above the

surface from side-to-side in a sweeping motion. Taking care not to blow

ripples into the epoxy.

A test patch is recommended prior to glassing below 60F. The temperature of the surface being coated is

as critical as the surrounding air temperature.

Application

Application should only be made on a perfectly dry surface. Pre-cut the cloth to fit the

surface to be patched. When using Epoxy Resin on wood, first apply a thin coat or resin over the surface.

Then while resin is still in liquid stage, apply Sea-Glass Cloth. Make sure to work out all air bubbles and

wrinkles as you go with a short nap disposable roller, squeegee, or resin roller.

Epoxies are generally more viscous (thicker) than polyester and tend to wet-out (penetrate) fiberglass

reinforcements more slowly. After the Resin Has Cured (Hardened)

Epoxies are not air-inhibited and therefore the surface cures without a surfacing agent (wax). Sand cured

surface to remove all imperfections and excess cloth. A second coat may be applied for extra protection.

Note: Amine Blush: may form over the cured surface. This is a by-product of a fast cure and will appear at

the surface as a slippery film. If present it must be removed prior to adding additional layers of epoxy or

top coating. If an amine blush appears, this should be removed with water before sanding and recoating.

To prevent deterioration from the weather and the sun, paint the finished product. You can also add

Evercoat Colouring Agent into the resin directly to tint it and increase resins UV resistance. Use pigment

sparingly to prevent inhibition of cure. Do not exceed one ounce of pigment per quart of resin.

30

17) POST TENSIONING:

Introduction:

Prestressing systems have developed over the years and various companies have patented their products. Detailed information of the systems is given in the product catalogues and brochures published by companies. There are general guidelines of prestressing in Section 12 of IS 1343: 1980. The information given in this section is introductory in nature, with emphasis on the basic concepts of the systems. The prestressing systems and devices are described for the two types of prestressing, pre-tensioning and

post-tensioning, separately. This section covers post-tensioning. Section 1.3, Pre-tensioning Systems and

Devices, covers pre-tensioning. In post-tensioning, the tension is applied to the tendons after hardening

of the concrete. The stages of post-tensioning are described next.

Stages of Post-tensioning: In post-tensioning systems, the ducts for the tendons (or strands) are placed along with the reinforcement before the casting of concrete. The tendons are placed in the ducts after the casting of concrete. The duct prevents contact between concrete and the tendons during the tensioning operation. Unlike pre-tensioning, the tendons are pulled with the reaction acting against the hardened concrete.

If the ducts are filled with grout, then it is known as bonded post-tensioning. The grout is a neat cement paste or a sand-cement mortar containing suitable admixture. The grouting operation is discussed later in the section. The properties of grout are discussed in Section 1.6, Concrete (Part-II). In unboned post-tensioning, as the name suggests, the ducts are never grouted and the tendon is held in

tension solely by the end anchorages. The following sketch shows a schematic representation of a grouted

post-tensioned member. The profile of the duct depends on the support conditions. For a simply

supported member, the duct has a sagging profile between the ends. For a continuous member, the duct

sags in the span and hogs over the support.

Fig: Post-tensioning.

31

Among the following figures, the first photograph shows the placement of ducts in a box girder of a simply

supported bridge. The second photograph shows the end of the box girder after the post-tensioning of

some tendons.

Fig: Post-tensioning ducts in a box girder.

The various stages of the post-tensioning operation are summarized as follows. 1) Casting of concrete. 2) Placement of the tendons. 3) Placement of the anchorage block and jack. 4) Applying tension to the tendons. 5) Seating of the wedges. 6) Cutting of the tendons.

32

The stages are shown schematically in the following figures. After anchoring a tendon at one end, the

tension is applied at the other end by a jack. The tensioning of tendons and pre-compression of concrete

occur simultaneously. A system of self-equilibrating forces develops after the stretching of the tendons.

Indian Institute of Technology Madras

Fig: Stages of post-tensioning (shown in elevation)

Devices: The essential devices for post-tensioning are as follows.

Casting bed Mould /Shuttering Ducts Anchoring devices Jacks Couplers (optional) Grouting equipment (optional).

33

Casting Bed, Mould and Ducts The following figure shows the devices.

Fig: Casting bed, mould and duct.

Anchoring Devices: In post-tensioned members the anchoring devices transfer the prestress to the concrete. The devices are based on the following principles of anchoring the tendons.

1) Wedge action 2) Direct bearing 3) Looping the wires

Wedge action: The anchoring device based on wedge action consists of an anchorage block and wedges.

The strands are held by frictional grip of the wedges in the anchorage block. Some examples of systems

based on the wedge-action are Freyssinet, Gifford-Udall, and Anderson and Magnel-Blaton anchorages.

The following figures show some patented anchoring devices.

Fig:Freyssinet T system anchorage cones.

34

Fig: Anchoring devices.

Direct bearing: The rivet or bolt heads or button heads formed at the end of the wires directly bear against a

block. The B.B.R.V post-tensioning system and the Preston system are based on this principle.

The following figure shows the anchoring by direct bearing.

Fig: Anchoring with button heads.

Looping the wires:

The Baur-Leonhardt system, Leoba system and also the Dwidag single-bar anchorage system, work on this

principle where the wires are looped around the concrete. The wires are looped to make a bulb. The

following photo shows the anchorage by looping of the wires in a post-tensioned slab.

35

Sequence of Anchoring: The following figures show the sequence of stressing and anchoring the strands. The photo of an anchoring

device is also provided.

Fig: Sequence of anchoring

Fig: Final form of an anchoring device

36

Jacks: The working of a jack and measuring the load were discussed in Section 1.3, Pre-

tensioning Systems and Devices. The following figure shows an extruded sketch of the anchoring

devices.

Fig: Jacking and anchoring with wedges

Fig: Jacking and anchoring with wedges

37

Couplers: The couplers are used to connect strands or bars. They are located at the junction of the members, for example at or near columns in post-tensioned slabs, on piers in post-tensioned bridge decks. The couplers are tested to transmit the full capacity of the strands or bars. A few types of couplers are

shown.

Fig: Coupler for strands

Fig: Couplers for strands

38

Grouting:

Grouting can be defined as the filling of duct, with a material that provides an anti-corrosive alkaline environment to the prestressing steel and also a strong bond between the tendon and the surrounding grout.

The major part of grout comprises of water and cement,

with a water-to-cement ratio of about 0.5, together with

some water-reducing admixtures, expansion agent and

pozzolans. The properties of grout are discussed in

Section 1.6, Concrete (Part-II). The following figure

shows a grouting equipment, where the ingredients are

mixed and the grout is pumped.

Fig: Grouting equipment

39

TRAINING DONE BY

MOYUKH ROY AGNAYA SUBBA RAKESH GUPTA SHANKAR SHING BHADURIA

SHIDDHRATH GHOSH SHARMISTHA DEY SARKAR ARPAN MITRA SOUMIK SUR

TATHAGATA ROY DARIKH NATH BAI SHARTHAK CHOWDHURY MRINMOY MONDAL

SUBHADIP BISWAS SOURADIP SAHA SAIKAT GHOSH LEZONG LEPCHA GOUTAM ROY

DEEPAK KUMAR

DONE UNDER

RAIL VIKAS NIGAM LIMITED

KOLKATA