Bamboo Project

 

	6. Demo constructions
	List of figures in section 6
Fig. 6.1.1	A photograph of the school building with bamboo mat
	boards
Fig. 6.1.2	Interior of the school building, shelves of plastered half split
	bamboos below the window level
Fig. 6.1.3.a	A photograph of the interior of the school building, gable
	wall from inside
Fig. 6.1.3.b	A photograph of the interior of the school building, landings
	of the Twin arch supported A frame
Fig. 6.1.4	A sketch of the 7.3m Span A frame supported by the twin
	bamboo arches vertically separated by ferro cement bands
	with three vertical bamboo ties and Centre 2 cross GI wire
	ties
Fig.6.1.5	A photograph of the school building: Plastering of the half
	split bamboo that make up the gable walls
Fig. 6.2.1	A view of the small house with ferro cement band twin
	bamboo arch supported  A frames
Fig. 6.2.2	A view of the small house with ferro cement band twin
	bamboo arch supported  A frames
Fig. 6.2.3	An inside  view of the A frames supported by Twin arches
	with ferro cement band ties
Fig. 6.2.4	A plan  of the small house with ferro cement band twin
	bamboo arch supported  A frames and bamboo mat boards as
	roof
Fig. 6.3.1	A plan  of the small house with near horizontal roof
Fig. 6.3.2	A view  of the small house with near horizontal roof of light
	weight cellular concrete from the top of a building on the
	south
Fig. 6.3.3	A view   of the small house with near horizontal roof from
	the north-east
Fig. 6.3.4	A view   of the small house with near horizontal roof during

 

 

 

 

 

 

 

 

 

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108

 

 

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110

 

 

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111

 

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101

 

	construction
Fig. 6.3.5	Floor plan	of the small house with near horizontal roof
Fig. 6.4.1.a	An interior	view	of the small house with  thatched  roof
	over bamboo bows
Fig. 6.4.2	A view  of the small house with thatched roof from the north
Fig. 6.4.3	A view  from the east of the small house ready to on the
	thatch for the roof
Fig. 6.4.4	A plan of the small house with thatched roof
Fig. 6.5.1	A view   of the 30m long sheds from east
Fig. 6.5.2	A view   of the two long sheds from the south
Fig. 6.5.3.a	An interior view		of the long shed  with vertically separated
	twin     bamboo arches with bamboo ties and ferro cement
	band ties
Fig. 6.5.3.b	An interior view   of the long shed: landings of the bows
	with ferro cement band ties
Fig. 6.5.3.c	An interior view   of the long shed : 3 ties for each bow
	between the horizontal tie and lower arch – enables one  to
	use the space between the horizontal ties and roof bottom as
	a huge storage area

 

 

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117

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

102

 

6.1              7.3 m span bamboo mat board sloped roof over bamboo bow supported ‘A’ frames for a primary school building in HET campus.

 

Size of the building: **10.6 m long and 7.3m wide** Figs. 6.1.1 to 6.1.3 show the photographs of the building.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.1.1         A photograph of the school building with bamboo mat boards

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.1.2 Interior of the school building, shelves of plastered half split bamboos below the window level

 

 

 

 

 

103

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.1.3.a A photograph of the interior of the school building, gable wall from inside.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.1.3.b A photograph of the interior of the school building, landings of the Twin arch supported A frame

 

 

 

 

 

104

 

Columns:

 

There are three columns separated by 3.6 m in the central part of each long wall Each of the columns is of 2m high spun cement pipe of outer dia 30cm and inner dia 26 cm. Only 1m of the pipe stands above the floor level while the rest goes down into the foundation and elevation of close to 45 cm.. It is filled with sand cement mortar all the way to the top but for the last 30cm. A 10cm x 10cm cross section RCC garden post is put into the spun pipe from the top to a depth of 30 cm and the inside of the pipe is completely grouted with cement concrete.

 

Arch foundations:

 

In the space between the columns is built an arch with RR masonry except for the last 15cm which is of brick masonry. This is referred to as arch foundation.

 

Walls:

 

The long walls: These are built with fly ash bricks to a thickness of 22.5cm up to the lentil level and 10cm thickness for about 75cm above the lentil level.

The short walls: These are 10 cm thick single brick walls that meander providing cup boards two on either side of the black board in the North side wall and three on the South side wall up to the lentil level or the black board level.

Above that it is a a single brick 10cm thick wall. All the walls are plastered on both sides.

 

Lentil tie beam cum sun shade:

 

On three sides around the building, a single thin beam of thickness 5cm and width of 110cm is casted out of which we get sun shades to a width of 45cm on the out side of the walls and 55cm wide slabs on to the inside of the walls to act as luggage storage bin. The fourth side(North facing short wall) has a big black board and hence the lentil beam does not have either the projection into the room or sun shade out side. The steel reinforcement is 6 nos of 6mm dia steel rods along the length and 8 mm dia steel rods in the transverse direction every 20 cm.

 

There is another thin RCC tie at the top of the wall linking the steel rods that come out of the top of the RCC garden posts through two 6mm dia steel rods.

 

The twin vertically separated twin bow arches supporting the ‘A’ frames:

 

The ‘A’ frames are supported by the twin vertically separated bamboo arches with ferro cement band ties with a span of 7.3m(24 ft) which are described earlier in section 5.5. These are further strengthened by three vertical ties of half split bamboos that go up all the way from bottom horizontal tie to the A frame sides at the top. Two cross GI wire ties from center of the horizontal tie to ferro cement band ties at the quarter span points further reinforce the frame.

A sketch of the ‘A’ frame supported by the bamboo arches is shown in Fig. 6.1.4.

 

 

 

 

 

 

 

 

 

 

 

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Ferroceemnt band ties

 

Bamboo

 

 

 

 

 

 

 

Brick walls

 

GI wire ties

 

Fig. 6.1.4 A sketch of the 7.3m Span A frame supported by the twin bamboo arches vertically separated by ferro cement bands with three vertical bamboo ties and Centre 2 cross GI wire ties.

 

Note: The two bamboos in the middle of the 2 GI wire ties are used to twist the GI wires, originally in the form a loose loop, locally called “Bisi”. Upon twisting, the GI wire loop reduces in length and becomes tight.

 

The advantage is that holes and bolts & nuts are not necessary. Traditionally the coconut fibre ropes are used for the purpose. With time, if the tie becomes loose, then the bamboo is twisted a little further to make the tie tight.

 

 

In all, 10 such A frames are used out of which 8 are evenly spaced in the centre with about 1.15m spacing while the last one on either side rest directly over the short walls.

 

The large ferro cement band ties at the ends of the A frames rest on the brick work that is raised from the lentil beam slab that projects into the room doubling as luggage storage utility.

Originally this brick work became necessary as the distance between the top of the long walls is so much that the end ferro cement bands of the ‘A’ frame got a bearing of just a few cm on the wall. This is probably due to a mistake in the measurement of the wall separation. But for this mistake, the end bands of the ‘A’ frame should have rested over the top of the long walls directly with about 10 cm bearing on each wall with out the additional brick work over the lentil slab beam.

 

Purlins and cross ties:

 

Both the arches and the sloping sides are tied with several round bamboos as purlins parallel to the long walls but obviously at different vertical planes.

Two giant X ties are made with bamboos and these have eight edges in all: four of these edges start from the four corners of the room; two each of the other four edges start from the two mid points of the long walls. The bamboos of these X crosses curve around the different arches of the A frames and are tied to the same at several places with binding wire ties. Further, three bamboos on each side start from the top of the short walls and lean against the fourth arch from the short wall

 

 

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and are tied to these securely with several binding wire ties. These help in keeping the A frames in vertical position even when the gable walls are subjected to wind loads.

 

Gable walls:

 

Over the short walls, the ‘A’ frames have a big triangular opening. It was decided to close these openings with what are called gable walls.

Round bamboos are tied at three different levels horizontally over the short wall. These are tied to different vertical and cross ties of the over lying ‘A’ frames. Half split bamboos of suitable lengths are then vertically placed above the short walls next to each other with their troughs facing out side closing the triangular space. Chicken mesh is then stretched on the out side of the half split bamboos and tied to the bamboos. This is then plastered with sand cement mortar.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig.6.1.5 A photograph of the school building: Plastering of the half split bamboo that make up the gable walls

 

6.2              3.5 m span bamboo mat board sloped roof over bamboo bow supported ‘A’ frames for a small house.

 

This is located in the second campus of Haritha Ecological Institute.

This has six columns each of 3.35 m long RCC garden post out of which 2.45 m is above the floor level which itself has an elevation of about 0.4m above the natural ground. These are in two rows of three each separated by 3.5m and their tops are joined by 6 round wood beams of dia about 15 cm.

7 of the twin arch bow beams supported ‘A’ frames rest over the wooden beams directly. The walls are of single brick and 10 cm thick.

The roof is of bamboo mat boards which by themselves give an eve of 60 cm on all sides.

 

 

 

 

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Figs. 6.2.1 to 6.1.3 show some photographs of the house while Fig. 6.2.4 shows a sketch of the plan of the house.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.2.1 A view of the small house with ferro cement band twin bamboo arch supported A frames.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.2.2 A view of the small house with ferro cement band twin bamboo arch supported A frames.

 

 

 

 

 

 

 

 

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Fig. 6.2.3 An inside view of the A frames supported by Twin arches with ferro cement band ties

 

Shelves, 2m high

 

Verandah,

 

Room, with 6 windows and two doors

 

North

 

 

Doors(2)

 

Shelves up to kitchen top

 

Fig. 6.2.4 A plan of the small house with ferro cement band twin bamboo arch supported A frames and bamboo mat boards as roof.

 

 

 

6.3            3m & 3.4 m Span ‘Flat Roof’ small house over bamboo bow supported beams: bamboo roof panels with ferro cement over lay, in HET campus.

 

This small house has two portions, one with aspan of 3m and the other with a span of 3.4 m.

The smaller portion is a single room while the larger portion has a verandah and bath cum toilet in it.

Fig. 6.3.1 shows the plan of the house while figs 6.3.2 to 6.3.4 show the photographs of the house.

 

 

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Shelves, 2m high

Dressing

Roof over hang

Bamboo arches

with 3m span

Bath &Toilet

Room, with 6

windows and

North

two doors

3.3m span

Bamboo arches,

Doors(2)

FerCem band ties

Shelves up to kitchen

Verandah,

top

Fig. 6.3.1

A plan

of the small house with near horizontal roof.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.3.2 A view of the small house with near horizontal roof of light weight cellular concrete from the top of a building on the south.

 

 

 

 

 

 

 

 

 

 

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Fig. 6.3.3	A view   of the small house with near horizontal roof from the
	north-east.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.3.4 A view of the small house with near horizontal roof during construction.

 

 

 

 

 

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Shelves, 2m high	Dressing
	room	Bath &Toilet

 

Room, with 6 windows and two doors

 

Verandah,

 

 

North

 

Doors(2)

 

Shelves up to kitchen top

 

 

 

 

Fig. 6.3.5         Floor plan of the small house with near horizontal roof

 

 

 

 

6.4          4.2 m span simple bamboo bow supported ‘A’ frames with a thatched roof house of 30 sq.m area, in Paloncha. (Not covered under the project)

 

Figs 6.4.1 to 6.4.3 show the photographs of the house while Fig. 6.4.4 shows the plan of the house.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6.4.1.a      An interior  view   of the small house with  thatched  roof

 

over bamboo bows

 

 

 

 

 

 

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PDF to Word

Father Of Civil Engineering - Mokshagundam Visvesvarayya

Sir Mokshagundam Visvesvaraya was a popular Indian Civil Engineer, scholar, and statesman born in 15 September 1860 at Muddenahalli, Karnataka. He is a recipient of the Bharat Ratna in the year 1955. He was also knighted as a Commander of the Indian Empire by King George V for his multiple contributions to the public good. 15 September is celebrated as the Engineer’s Day every year in India in his memory.

Career as Engineer

After graduated as engineer, he works for the Public Works Department (PWD) of Bombay, and later he was invited to join the Indian Irrigation Commission. He started an extremely elaborate system of irrigation in the Deccan area. He also designed and clear cut a system of autonomic embankment water floodgates which were first installed in the year 1903 at the Khadakvasla reservoir near Pune. These gates were employed to raise the flood supply level of storage in the reservoir to the highest level likely to be attained by its flood without any damage to the dam. On the successful of this project, the same system was installed at the Tigra Dam in Gwalior and the Krishnaraja Sagara (KRS) Dam in Mandya. He achieved celebrity status when he designed a flood protection system to protect the city of Hyderabad from floods.

Sir M. V. supervised the construction of the KRS Dam across the Cauvery River from concept to inauguration. This Dam created the biggest reservoir in Asia at the time. He was rightly called the “Father of Modern Mysore State” .During the time of his services with the Government of Mysore state, he was responsible for the founding of the Mysore Soap Factory, the Parasitoide, the Sri Jayachamaranjendra Polytechnic Institute, the Mysore Iron & Steel Works (now called Visvesvaraya Iron and Steel Limited) in Bhadravathi, the Bangalore Agricultural University, the State Bank of Mysore, The Century Club, Mysore Chambers of Commerce and other several ventures. He was also instrumental in charting out the plan for construction of road between Tirumala and Tirupati.

He retired in 1908. After his retirement, He left India for a foreign tour and study industrialized nations and then worked for Nizam of Hyderabad. He gives a measure suggestion of flood relief for Hyderabad town. In 1909, he was appointed as Chief Engineer of Mysore State, and in 1912, he was appointed as Diwan or First Minister of the princely state of Mysore. With the support of king of Mysore Krishnaraja Wodeyar IV, he made a contribution as Diwan to all round development for the state. Not only the Krishnaraja Sagara Dam and Reservoir, the steel works at Bhadravathi, the Sri Jayachamarajendra Polytechnic Institute at Bangalore, the University of Mysore, Bank of Mysore Limited (now State Bank of Mysore) at Bangalore [1913]Karnataka Soaps & Detergents Limited (KSDL) – Govt Soap Factory [1916] and many other industries and public works owe their inception or active nurturing to him. He was instrumental in the founding of the “Government Engineering College” at Bangalore in 1917, one of the first engineering institutes in India. This institution was later named the “University Visvesvaraya College of Engineering” (UVCE) after its founder. It remains one of the most reputed institutes of engineering in Karnataka. He also commissioned several new railway lines in Mysore states.

Some of the awards and honours donated on Sir Mokshagundam Visvesvaraya are:

• 1959: Fellowship of the Indian Institute of Science, Bangalore


• 1958: 'Durga Prasad Khaitan Memorial Gold Medal' by the Royal Asiatic Society Council of Bengal


• 1955: Conferred ' BHARATHA RATNA'


• 1953: Awarded the Honorary Fellowship of the Institute of Town Planners, India


• 1953: D.Litt - Andhra University


• 1948: Doctorate - LLD, Mysore University


• 1944: D.Sc. - Allahabad University


• 1943: Elected as an Honorary Life Member of the Institution of Engineers (India)


• 1937: D.Litt - Benaras Hindu University


• 1931: LLD - Bombay University


• 1921: D.Sc. - Calcutta University


• 1915: K.C.I.E. (Knight Commander of the Order of the Indian Empire)


• 1911: C.I.E. (Companion of the Indian Empire) at the Delhi Darbar


• 1906: "Kaisar-i-Hind" in recognition of his services


• 1904: Honorary Membership of London Institution of Civil Engineers for an unbroken period of 50 years.

Targeting new Possibilities in KLRT

The promoters of the institution, KLR INSTITUTIONS has its origin way back in 1999. With a commitment of providing higher education to this rural part of Khammam District, KLR INSTITUTIONS, under the chairman ship of Late Dr.K.Lakshma Reddy, has established variety of institutions right from School to PG College.

With an aim to work for higher education in emerging areas, Sri KLR has proposed to start the institution in the academic year 2008-09 with Electronic & Communication Engineering , Civil Engineering, Computer Science & IT Engineering departments. The vision of the institute is to become a center for research and education in Electrical & Electronic, Automobile and Mechanical Engineering.

 

2010 - 2011 FRESHERS PARTY...

M.APUROOP - 2008-12 Batch

 

NAME      : M.APUROOP


REGD.NO: 08QT1A0104


BATCH     : 2008-2012


MOB NO   : 9000955916


E-Mail       : apuroop.civil@gmail.com

Minor Bridge Project

 

 

CONTENTS
1. INTRODUCTION
1.1 DEFINITION OF A BRIDGE	2
1.2 OTHER IMPORTANT DEFINITIONS	2
2. SITE INSPECTION
2.1 SELECTION OF SITE	5
2.2 EXISTING DRAINAGE STRUCTURES	5
3. COMPONENTS OF BRIDGE
3.1 FOUNDATION	6
3.2 SUB - STRUCTURE	9
3.3 BEARINGS	11
3.4 SUPER STRUCTURE	12
4. DESIGN OF STRUCTURE
4.1 DESIGN LOADS & STRESSES	17
4.2 HYDROLOGY	18
4.3 SUB-SOIL INVESTIGATION	18
4.4 TEMPORARY WORKS	18
4.5 DESIGN	19
4.6 REINFORCED EARTH RETAINING	21
STRUCTURES
4.7 SAFETY BARRIERS	23

 

 

 

 

 

 

 

[1]

 

 

 

 

 

1.INTRODUCTION

 

1.1 DEFENITION OF A BRIDGE

 

A bridge is a structure providing passage over an obstacle without closing the way beneath. The required passage may be for a road, a railway, pedestrians, a canal or a pipeline. The obstacle to be crossed may be a river, a road, railway or a valley.

 

In other words, bridge is a structure for carrying the road traffic or other moving loads over a depression or obstruction such as channel, road or railway.

 

A bridge is an arrangement made to cross an obstacle in the form of a low ground or a stream or a river without closing the way beneath.

 

For bridges having length more than 60m, detailed estimate is required to be submitted to Govt. for obtaining Administrative Approval. It is, therefore, necessary that site is finalized by the Superintending Engineer, Designs Circle so that detailed soil explorations as may be necessary could be done by Road Project Divisions.

 

 

1.2 SOME IMPORTANT DEFINITIONS

 

Small bridge

 

Overall length of the bridge between the inner faces of dirt walls is up to 30m and where individual span is not more than 10m

 

Minor bridge

 

Total length up to 60m

 

Major bridge

 

Total length greater than 60

 

Culvert

 

A cross drainage structure having total length of 6 m or less between inner faces of dirt wall

 

Foot Bridge

 

 

 

 

[2]

 

 

A bridge extensively used for carrying pedestrians, cycles and animals

 

High Level Bridge

 

A bridge, which carries the roadway above H.F.L. of the channel

 

Submersible Bridge/ Vented Causeway

 

A bridge designed to be overtopped during floods.

 

Clearance

 

The	shortest   distance   between   boundaries   at	a	specified	position	of	bridge
structure
Freeboard
The	difference   between  H.F.L.   (allowing   afflux)   and   foundation   level  of  road
embankment on approaches

 

H.F.L.

 

Highest flood level is the level of highest flood ever recorded or the calculated level for design discharge

 

L.W.L.

 

Lowest flood level is the level of the water surface obtained in dry season

 

Length of Bridge

 

The length of a bridge structure will be taken as overall length measured along the center line of the bridge between inner faces of dirt wall

 

Linear Waterway

 

Width   of   waterway   between   the   extreme   edges   of   water   surface   at   H.F.L.

 

measured at right angles to the abutment face

 

Effective Linear Waterway

 

The total width of the waterway of the bridge at H.F.L. minus effective width of obstruction

 

Safety Kerb

 

A roadway kerb for occasional use of pedestrian traffic

 

 

 

 

 

[3]

 

 

Width of Carriageway

 

Minimum clear width measured at right angles to the longitudinal centerline of bridge between inside faces of roadway kerb or wheel grades

 

Vertical clearance

 

The height from the design highest flood level with afflux of the channel to the lowest point of the bridge superstructure at the position along the bridge where clearance is denote

 

20. Bearings

 

The part of the bridge structure which bears directly all the forces from the structure above and transmits the same to the supporting structure

 

Abutment

 

The end supports of deck of bridge, which also retains earth, fill of approaches behind fully or partly

 

Spill through Abutment

 

An abutment where soil is allowed to spill through gaps along the length of abutment such as column structure where columns are placed below deck beams and gap in between is free to spill earth

 

Afflux

 

The rise in the flood level of the river immediately on the upstream of a bridge as a result of obstruction to natural flow caused by the construction of bridge and its approaches

 

Bearing Capacity

 

The supporting power of a soil / rock expressed as bearing stress is referred to as its bearing capacity

 

Foundation

 

The part of bridge is in direct contact with and transmitting load to the founding strata

 

Pier

 

Intermediate supports of the superstructure of a bridge

 

 

 

 

[4]

 

 

Retaining Wall

 

A wall designed to resist the pressure of earth filling behind

 

Return Wall

 

A wall adjacent to abutment generally parallel to road or flared up to increase width and raised up to the top of road

 

Toe wall

 

A wall built at the end of the slope of earthen embankment to prevent slipping of earth and / or pitching on embankment

 

Wing Wall

 

A wall adjacent to abutment with its top up to R.T.L. near abutment and sloping down up to ground level or a little above at the other end. This is generally at 45 degrees to the alignment of road or parallel to the river and follows the profile of earthen banks

 

Substructure

 

The bridge structure such as pier and abutment above the foundation and supporting the superstructure. It shall include returns and wing walls but exclude bearings

 

Skew angle of Bridge

 

It is the angle between the perpendicular to the flow of traffic direction and the flow direction of river

 

2. SITE INSPECTION

 

2.1 SELECTION OF SITE

 

Where there is any choice, select a site:

 

(1)    Which is situated on a straight reach of the stream, sufficiently below bends

 

(2)    Which is so far away from the confluence of large tributaries as to be beyond their disturbing influence

 

(3)    Which has well-defined banks

 

(4)    Which makes approach roads feasible on the straight

 

In siting small bridges and culverts, due consideration should be given to the geometrics of the approach alignment and the latter should essentially govern the

 

 

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selection of site unless there are any special problems of bridge design.

 

2.2 EXISTING DRAINAGE STRUCTURES

 

If, by chance, there is an existing road or railway bridge or culvert over the same stream and not very far away from the selected site, the best means of ascertaining the maximum discharge is to calculate it from data collected by personal inspection of the existing structure.

 

It should be seen whether the existing structure is too large or too small or weather it has other defects. All these should be carefully recorded.

 

3. COMPONENTS OF BRIDGE

 

3.1 FOUNDATION

 

3.1.1 Depth of foundations

 

The foundation shall be taken to such depth that they are safe against Scour, or protected from it. Apart from this, the depth should also be sufficient from consideration of bearing capacity, settlement, stability and suitability of strata at the founding level and at sufficient depth below it.

 

Depth of shallow foundations may be taken down to a comparatively shallow depth below the bed surface provided a good bearing stratum is available and the foundation is protected

 

Selection of a particular type of foundation is a very important job as it affects the entire proposal for the bridge. On the other hand if scour depth is less and flood depth is also reasonably small the raft foundation could be the choice.

 

3.1.2 Important Points

 

The following points are to be noted while preparing bridge proposal.

 

(a) Span to height ratio for Raft foundation be kept as 1.00 to 1.25

 

Open foundation be kept as 1.25 to 1.50

 

Pile foundation be kept as 1.25 to 1.75

 

Well foundations it should be 1.50 to 2.00

 

(b)  The  dimensions  of  pier,  abutment  and  well  foundation  to  be  taken  from  type

 

 

 

 

[6]

 

 

designs or from the latest I.R.C. Codes.

 

(c)   Proper uniform sitting of well foundation could be ensured by taking the foundation into rock by about 15 cm.

 

(d)   The raft foundation details are taken from the type designs as applicable.

 

(e)    Other similar designs prepared and approved by the Designs Circle should also be studied and referred to.

 

(f)  Open foundations are comparatively easy to decide about.

 

(g)    Anchorage of open foundation into the rock shall be as per IRC-78 i.e. minimum 0.60m into hard rock and 1.50 m into soft rock excluding scour able layers.

 

(h)     Leveling course and annular filling should be proposed for open foundation. Annular filling should be done with M 15 concrete up to rock level.

 

(i)     Stability of foundation should be worked out. The beginner should obtain the standard calculation sheets from office, and do the calculations manually to gain confidence.

 

3.1.3 FOUNDATION TYPES

 

Generally two types of foundations are adopted for bridge structures. (i) Shallow foundations - Open foundations - Raft foundations

 

(ii) Deep foundations - Pile foundations - Well foundations

 

Open Foundations

 

Open foundations are preferred over any other type. These are to be provided when good-founding strata are available at shallow depth and there is not much problem of dewatering. R.C.C. footings are preferred over P.C.C. footing in case of RCC piers.

 

Raft Foundations

 

Raft foundation is designed as R.C.C. solid slab. The additional component of cut off walls on both sides U/s and D/s was considered necessary to take care of seepage and possible undermining of the raft due to seepage and the scour due to floods.

 

It was observed that the raft was showing signs of cracks between pier and cut off walls. The arrangement was, therefore, subsequently changed by resting pier on raft over the cut off walls.

 

 

[7]

 

 

Raft foundation is, however, not recommended when

 

- Spans more that 10m raft being uneconomical.

 

- Bridge foundation that cannot be inspected during its service life.

 

- Serious problem of dewatering due to large in flow of water/standing water.

 

- Where open foundations are feasible.

 

In other cases of small span bridges on weak soils, the raft foundations may be a most practicable solution.

 

Well Foundations

 

Some important points to be noted regarding well foundations are as follows –

 

a. If the external diameter of single circular wells exceeds 12 m relevant provisions of clause 708.1.2 of IRC: 78-2000 shall apply.

 

b. The steining thickness of well shall not be less than 500 mm and shall satisfy the following relationship

 

h = kd L where h = minimum thickness of steining in m d = external diameter of circular well in m

 

L = depth of wells in m below top of well cap or LWL whichever is more

 

K = constant(for wells in cement concrete 0.03,brick masonry 0.05 and twin D wells 0.39(For details refer to clause 708.2.3 of IRC: 78-2000).

 

Piles Foundations

 

 

 

Type of Strata	Minimum Embedment
Hard rock	1.5 x dia. of pile	400
Soft rock	3.0 x dia. of pile	250
	2.0 x dia. of pile	200

 

 

 

 

 

 

[8]

 

 

Although piles can be designed as end bearing or friction piles, only end bearing bored cast-in-situ piles drilled with rotary rig be preferred. Designs with single row of piles per substructure and annular piles filled or not filled should not generally be preferred.

 

3.2 SUB - STRUCTURE

 

Type designs available would provide sufficient information about the dimensions of the P.C.C. piers and abutments up to a height of 10m. These type designs available are for non-seismic zones only.

 

Grade of Concrete as are specified below : For bridges(Length > 60 m) :

 

Structural member	Conditions of Exposure
	Moderate	Severe
P.C.C.	M 25	M 30
R.C.C.	M 30	M 35
P.S.C.	M 35	M 40
For other bridges or Culverts (<60m) :
P.C.C.	M 15	M 20
R.C.C.	M 20	M 25

 

 

The proposed allowable compressive, tensile and shear stresses are as follows:

 

(i)   Flexural compression scb = 0.33 fck for all grades of concret

 

(ii)   Flexural tension stb = 0.033 fck for all grades of concrete

 

(iii)   Shear = As below

 

(a)  The  allowable  shear  stress  for  R.C.C.  members  subject  to  flexure,  shear

 

and members subject to axial compression, the allowable shear stress carried by

 

the concrete (tc) shall be as per following table.

 

 

 

 

 

 

 

 

[9]

 

 

100 A	Permissible Shear Stress in Concrete, t  14/mm2
bd	Grade of Concrete
	M 20	M 25	M 30	M 35	M 40 and above
(1)	(2)	(3)	(4)	(5)	(6)
0.15	0.18	0.19	0.20	0.20	0.20
0.25	0.22	0.23.	0.23.	0.23.	0.23.
0.50	0.30	0.31	0.31	0.31	0.32
0.75	0.35	0.36	0.37	0.37	0.38
1.00	0.39	0.40	0.41	0.42	0.42
1.25	0.42	0.44	0.45	0.45	0.46
1.50	0.45	0.46	0.48	0.49	0.49
1.75	0.47	0.49	0.50	0.52	0.52
2.00	0.49	0.51	0.53	0.54	0.55
2.25	0.51	0.53	0.55	0.56	0.57
2.50	0.51	0.55	0.57	0.58	0.60
2.75	0.51	0.56	0.58	0.60	0.62
3.00 and above	0.51	0.57	0.60	0.62	0.63

 

 

For slabs the allowable shear stress carried by concrete shall be Ktc Where K has the values given below

 

Overall	depth	of300 or more	275	250	225	200	175	150	or
slab (mm)								less
K		1.00	1.05	1.10	1.15	1.20	1.25	1.30

 

 

 

Forces to be considered for stability of piers and abutments are given in IRC:6-2000 Loads & Stresses. The permissible increases in stresses in the various members under different load combinations are also given in the code. The same is summarized as below

 

 

[10]

 

 

 

 

 

 

 

DING RETURAN	B
ROAD TOP LEVEL
	PIER CAP
1	1
n	n
RIDING RETURN	PIER
BB
FB
DOWELS
	RCC RAFT
	B
SECTIONAL ELEVATION ALONG A-A
ES	CUT OFF
	WALL

 

 

 

 

Sr. No.	Load Combination		Increase in permissible
			stresses.
1.	Dead + Live		NIL
2.	1 + Secondary + Deformation + Temperature		15%
3.	2	+ wind + wave pressure	33 1/3 %
4.	2	+ seismic + wave pressure	50%
5.	2	+ barge impact + wind load	33 1/3 %
6.	Dead + water current + buoyancy +		33 1/3 %
	Earth pressure + erection + friction +		50%
	wind + grade effect 6 + Seismic - Wind

 

 

Apart from above-mentioned combinations, following load combinations should generally be checked.

 

1. Dead + Live + wind in transverse direction Wind acting perpendicular to deck.

 

65   % perpendicular and 35 % along the deck. The wind velocity and method of computation of forces is given IRC: 6-2000. (Section-II).

 

1. One span dislodged (i.e. smaller span not in position) for pier and no span condition for abutment.

 

3.3 BEARINGS

 

3.3.1 Types

 

Various bearings in use by the department are M.S. plate, cast steel rocker rollers, neoprene, and POT/ PTFE, R.C.C. Roller.

 

3.32 Selection

 

The selection of Bearings should be as follows :

 

1	Spans upto and including 10 m for solid slab	Tar paper
	superstructure
2	Span > 10 m and < 25m	Neoprene
3	For larger spans	POT/PTFE

 

 

 

 

[11]

 

 

Reference should be made toI.R.C.83 Section IX

 

Part I               Metalic Bearings

 

Part II             Elastomeric Berings

 

Part III            POT, POT/PTFE

 

3.3.3 Seismic arrestors

 

To prevent dislodgement of superstructure reaction blocks or other types of arrestors shall be provided and designed for twice the seismic force.

 

 

3.4 SUPER STRUCTURE

 

 

Various types of superstructures are Arches, Masonry, C.C., R.C.C. Girder and deck slab, Solid Slab, R.C.C. T-Beam Slab, R.C.C. Box Beam, Voided Slab, P.S.C. Two Girder, Three Girder, Multi- Girder, Box Girder, Simply supported continuous Cantilever, Balance Cantilever, Hammer Head, Bow string girder, composite construction, cable stayed, suspension.

 

3.4.1 Selection of Proper Superstructure

 

Generally the following criteria should be followed for selection of superstructure depending on span length.

 

1. Spans upto 10m. R.C.C. solid slab.

 

1. Spans- 10 to 15m R.C.C. solid slab /Ribbed slab,

 

1. Spans - 15m.to 20m R.C.C. Multi-girder slab system.

 

1. Spans - 20m.to 30m P.S.C. Girder/Box type superstructure.

 

1. Span - 30m to 60m P.S.C. Box girder.

 

For spans more than 60 m the discussions should be held with Superintending Engineer, Designs Circle regarding selection of the type of superstructure.

 

For spans up to 10m solid slab superstructures are found most suitable. As the span increases beyond 10m the thickness of solid slab poses difficulties during concreting. Lot of construction joints are created in the structure if proper programme of concreting is not prepared and insisted upon.

 

 

[12]

 

 

Spans between 15m to 20m, multi-girder system would be desirable. Two-girder system should be avoided as far as possible. In case of single lane bridges two-girder system is natural choice.

 

For spans between 20m and 30m R.C.C. box type superstructure is considered suitable. Use of R.C.C. girder and slab system might result in excessive deflections under live load. Box girder is a more desirable shape for the superstructure.

 

Beyond 30 m span, it is necessary to go for P.S.C. This enables us to somewhat restrict the deck height to the desired level. For spans greater than 60m discussions should be held with Superintending Engineer, Designs Circle for deciding the type of superstructure.

 

3.4.2 Type Design

 

Type designs are available for solid slab and girder type superstructures. The type designs prepared by M.O.S.T. are also available for R.C.C. solid slab up to 10 m, R.C.C. Girder slabs upto 24 m and P.S.C. girder slab bridges upto 40 m spans.

 

3.4.3 Minimum thickness

 

Minimum thickness of deck slab shall not be less than 300 mm and 200 mm at tip of cantilever in transverse direction and minimum thickness of soffit slab shall be 240mm irrespective of provisions elsewhere. All the specified minimum thickness are from durability point of view.

 

3.4.4 Expansion Joints

 

To cater for the expansion and contraction of superstructure suitable expansion joint is required to be provided. The expansion joint is also supposed to be leak proof so that the superstructure, bearings and piers do not get damaged due to such leakage of rainwater etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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SUITABILITY CRITERIA FOR ADOPTION OF DIFFERENT TYPES

 

OF EXPANSION JOINTS

 

 

 

 

Sr.	Type of	Suitable for adoption joint	Service	Special Consideration
No	Expansion		Life
1	Buried	Simply supported	10 years	Only for decks
.		spans up to 10m		With bituminous
				asphaltic wearing
				coat.
2	Filler Joint	Fixed end of simply	10 years	The sealant and joint
.		supported spans with		filler would need
		In-significant  movement.		replacement if found
				damaged.
3	Asphaltic	Simply supported spans	10 years	Only for decks with
.	Plug Joint	for right or skew upto		bituminous /asphaltic
		(20 degree) moderately		wearing coat. Not
		curved or wide deck		suitable for bridge with
		with maxi- mum		longitudinal gradient
		horizontal movement		more than 2% and
		not exceeding 25mm.		cross camber/super-
				elevation exceeding
				3%.
4	Compression	Simply support of	10 years	Chloroprene/ closed
.	Seal Joint	continuous spans right or		Foam Seal may need
		skew (upto 30°),		replacement during
		moderately curved with		service.
		maximum horizontal
		movement not exceeding
		40 mm.

 

 

 

 

 

 

 

 

 

 

 

 

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5	Elastomeric	Simply supported or	10 years	Not suitable for
.	slab seal joint	continuous spans Right or		bridges located in
		skew (less than 70 degree)		heavy rainfall area and
		moderately curved with		spans resting on
		maximum horizontal		yielding support.
		movement up to 50 mm.
6	Simple strip	Moderate to large simply	25 years	Elastomeric seal may
.	seal joint	supported.(cantilever/		need replacement
		continuous construction		during service.
		having right, skew or
		curved deck with
		maximum horizontal
		movement upto 70 mm.

 

7	Modular strip/	Large to very large	25 years	Elastomeric seal may
.	Box Seal	continuous/cantilever		need replacement
	Joint	construction with right, skew		during service
		or curved deck having
		maximum horizontal
		movement  in excess
		of 70  mm.
8	Special	For bridge having wide	25 years	Elastometric seal may
.	joints for	decks/span length of		need replacement during
	special	more than 120 m. or/and		service. Provision of
	condition	involving complex		these joints may be
		movement/rotations in		made with prior approval
		different directions/		of competent authority.
		plans,  provision  of  special
		type of modular expansion
		joints such as swivel joists
		joints may be made.

 

 

These are proprietary items for which 10 years warranty shall be insisted upon from the suppliers.

 

For larger expansion gaps, of about 50mm and more the joint has to be designed suitably. Other types of joints are :

 

 

 

 

[15]

 

 

1. Finger type joint (Cast steel).

 

1. Strip seal joint (Elastomeric)

 

1. Compression seal joint (Elastomeric)

 

1. Slab seal joint (Elastomeric)

 

1. Modular joints. (Modules with Elastomeric)

 

The above joints are costly as compared to conventional joint described earlier. We are, however, left with no choice for long span bridges but for adopting them. For details of material properties refer latest M.O.S.T. specifications for Roads and Bridges.

 

The above item are presently patented and hence detailed design calculations are not generally made available. It should be insisted upon.

 

For details of these joints refer literature given by the manufacturers.

 

Extra care need be taken for maintaining line and level of the joint to match perfectly with the geometry of the deck surface. Expansion joint is the place wherein lies the comfort of the road users. Improper fixing invites criticism from public.

 

3.4.5 PARAPET AND KERB

 

Deciding the type of railing, kerb etc., as per the type of bridge i.e. high level or submersible.

 

(i)For High Level Bridge

 

Superintending Engineer Designs Circle’s Type drawings or Sanchi Type parapet as mentioned in designs criteria can also be adopted.

 

(ii) For Submersible Bridge

 

Railing shall be removable type. Either pipe railing or collapsible type as shown in the type drawings.

 

3.4.6 WEARING COAT

 

Earlier upto 1980 R.C.C. wearing coat was generally adopted. Now as per Govt. in P.W.D. Circular No.CEC/1179/50677/CR-225/D-29-A dated 12.08.80, following type of wearing coat are generally provided for bridges.

 

 

 

 

 

 

[16]

 

 

Conventional Practice

 

High Level Bridges : Bituminous 50 mm DBM + 25 mm AC/SDBC

 

Submersible Bridges : C.C. M-20 with temperature steel.

 

Long Span Bridges : Bituminous.

 

Better treatment considered today is –

 

12 mm Mastic Asphalt as leak proof layer.

 

+  50 mm DBM

 

+  25 mm Bituminous concrete / Mastic Asphalt

 

3.4.8  WATER SPOUTS

 

Waterspouts are required to drain out the rainwater from the deck surface quickly. The deck has camber or super elevation, which help rainwater get quickly towards kerbs. The waterspouts located near the kerb further disposes the water out. One water spout per 20 sq.m. of the deck area is considered adequate.

 

 

1. 4.   DESIGNING

 

4.1  DESIGN LOADS & STRESSES

 

 

All new structures shall be designed for the condition when footpath is used as carriageway. The footpath portion may be provided at the same level as the bridge carriageway and separated by crash barrier in non built-up areas. In built-up areas, raised footpaths shall be provided.

 

All the components of structures shall be designed for a service life of 100 years except appurtenances like crash barriers, wearing surface and rubberized components in expansion joints and elastomeric bearings. All the requirements to achieve durability and serviceability shall be implemented.

 

 

 

 

 

 

 

 

 

 

 

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4.2 HYDROLOGY

 

All the structures shall have adequate waterway, which shall in any case be not less than that of existing bridge (except when such waterways can be reduced in cases like clogging or silting of spans, etc.). The design discharge shall be evaluated for flood of 100-year return period.

 

4.3 SUB-SOIL INVESTIGATION

 

Independent sub-soil investigations shall be carried out to establish the soil parameters required for detailed design of foundations in accordance with relevant provisions of IRC:78 and MORTH Specifications.

 

4.4 TEMPORARY WORKS

 

4.4.1 Form Work

 

The Concessionaire shall be responsible for the safe, workable design and methodology for all temporary or permanent forms, staging and centering required for supporting and forming the concrete of shape, dimensions and surface finish as shown on the drawings (Refer IRC:87). Adequate foundation for the staging shall be ensured. Redundancy in support system shall also be ensured by providing diagonals and additional members.

 

The following guidelines shall be adopted:

 

(i)   Formwork shall be of steel, marine ply or laminated plywood.

 

(ii)   Only such shuttering oil (release agent) shall be used, which permits easy removal of shutters without leaving stains or other marks on the surface of the concrete. Requirements given under Clause 3.5 of IRC:87 shall also be complied with.

 

(iii)   In case of tubular staging of heights more than 10 m, special attention shall be paid to the structural adequacy of the system, efficacy of the connections (clamps etc), and foundations. Foundation blocks of adequate thickness in M15 cement concrete shall be provided under the base plates to prevent differential settlements.

 

(iv)   In case of prestressed concrete members, the side forms shall be removed as early as possible and the soffit forms shall permit movement of member without restraint, when prestress is applied.

 

(v)   Adequate foundations for formwork shall be ensured.

 

 

 

[18]

 

 

4.4.2 Special Temporary and Enabling Works

 

Designs, drawings and methodology proposed by the Concessionaire in the use of special temporary and enabling works like Launching Girders, Cantilever Construction Equipment, Tall Formwork, Shoring for Earth Retention, Lifting and Handling Equipments and the like shall be submitted to the Independent Engineer (IE) for his review and comments if any. The Concessionaire shall be fully responsible for the design and structural adequacy of all temporary and enabling works. Review by IE shall not relieve the Concessionaire of this responsibility.

 

4.5 DESIGN

 

4.5.1 Foundations and Sub-structures

 

The design of foundations and sub-structures shall conform to IRC:78.

 

Open Foundations

 

The design of open foundations shall conform to IRC:78. Floor protection shall be provided as per Section 2500 of MORTH Specifications.

 

Pile Foundations

 

(i) The design of pile foundations shall be done as per IRC:78. The Concessionaire shall submit a method statement supported by the following:

 

(a)   Bore-log details for each foundation;

 

(b)   Design assumptions;

 

(c)   Design calculations both for single pile or group of piles and for pile type;

 

(d)  Type of piles-Bored cast-in-situ piles and driven piles;

 

(e)   Procedure adopted for installation of piles;

 

(f)  Arrangements for load testing of piles;

 

(g) Format for reporting of test results.

 

(ii) The Concessionaire shall submit the following information regarding proposed proprietary system of piling:

 

(a)   General features of the process/system along with specifications and standards.

 

(b)   Authenticated copies of license/agreement, if any;

 

 

 

[19]

 

 

(c)    Details of plant and equipment to be used along with the names of manufacturers and name of process/system;

 

(d)   Details of projects where the process/system has been successfully used;

 

(e)   Limitations, if any;

 

(f)  Acceptance tests and criteria;

 

(g)   Installation and maintenance procedure and schedule; and

 

(h)   Performance warranty.

 

Well Foundations

 

(i) For conventional method of well sinking, the Concessionaire shall submit a method statement including the following:

 

(a)   Design calculations and drawings,

 

(b)   Procedure for sinking and plugging of well,

 

(c)   Format for reporting of test results.

 

(ii) If proprietary system of well sinking like jack down method is proposed to be used, the Concessionaire shall submit relevant information covering inter-alia the following:

 

(a) General features of the system along with specifications and standards and justification for the thickness of steining proposed to be adopted;

 

(b)   Authenticated copies of license/agreement, if any;

 

(c)    Details of plant and equipment to be used along with the names of manufacturers and name of process/system;

 

(d)   Details of projects where the process/system has been successfully used;

 

(e)   Limitations, if any;

 

(f)  Acceptance tests and criteria;

 

(g)   Installation and maintenance procedure and schedule; and

 

(h)   Performance warranty.

 

 

 

 

 

 

 

 

 

[20]

 

 

(iii) The Concessionaire in his Methods Statement shall include the procedure for sinking by special methods, carrying out tests, if any, of wells including design criteria/calculations, drawings and formats for reporting test results.

 

4.5.2 Approach Slabs

 

Approach slabs shall be provided as per Clause 217 of IRC:6 and Section 2700 of MORTH Specifications.

 

4.5.3 Superstructures

 

The design of reinforced and pre-stressed concrete superstructures shall be as per IRC:21 and IRC:18 respectively. The design of steel and steel-concrete composite super structures shall conform to IRC:24 and IRC:22 respectively.

 

The Concessionaire shall submit Method Statement indicating inter-alia the following:

 

(i)   Sources of materials,

 

(ii)   Design, erection and removal of formwork,

 

(iii)   Layout of casting yard together with necessary details,

 

(iv)   Production, transportation, laying, compacting and curing of concrete,

 

(v)     Sequence of concreting in cast-in-situ construction, side shifting of girders, if applicable and placing of girders on the bearings,

 

(vi)   Details of construction joints,

 

(vii)   Prestressing system, if required,

 

(viii)   Methodology and equipment for side shifting and launching of pre-cast girders,

 

(ix)   Key personnel for execution and supervision,

 

(x)   Testing and sampling procedure,

 

(xi)   Equipment details.

 

4.6 Reinforced Earth Retaining Structures

 

Reinforced earth retaining structures shall not be provided for height more than 6 m unless otherwise specified, and near water bodies. Such structures should be given special attention in design, construction, ground improvement where necessary,

 

 

 

 

[21]

 

 

maintenance and selection of System/System design. Local and global stability of the structure shall be ensured.

 

Design Accreditation and warranty for life of the structure from the approved supplier/ manufacturer shall be obtained and furnished. A qualified and experienced technical representative of the approved supplier/manufacturer shall be present on site throughout during the casting and erection phases to ensure that the quality of the works executed by the Concessionaire is in accordance with good industry practice.

 

The Concessionaire shall submit relevant information on the system covering inter-alia the following:

 

(i)   General features of the system along with specifications and standards;

 

(ii)   Authenticated copies of license/agreement, if any;

 

(iii)    Details of plant and equipment to be used along with the names of manufacturers and name of process/system;

 

(iv)   Details of projects where the process/system has been successfully used;

 

(v)   Limitations, if any;

 

(vi)   Acceptance tests and criteria;

 

(vii)   Installation and maintenance procedure and schedule; and

 

(viii)   Performance warranty.

 

The Concessionaire shall submit a method statement including the following:

 

(i)   Design assumptions, calculations and drawings,

 

(ii)   Construction Procedure,

 

(iii)    Tests to be conducted including frequency and the formats for reporting the test results.

 

The packaging of reinforcing elements shall clearly indicate the name of the manufacturer/ supplier and brand name, date of production, expiry, if any and batch identification number along with the manufacturer’s test certificates.

 

 

 

 

 

 

 

 

[22]

 

 

4.7 Safety Barriers

 

(i)   For bridges without foot paths, concrete crash barriers shall be provided at the edge of the carriageway on all new bridges.

 

(ii)    The type design for the crash barriers may be adopted as per IRC:5. The design loading for the crash barriers shall be as per Clause 209.7 of IRC:6.

 

(iii)   For bridges with foot paths, pedestrian railing shall be provided on the outer side of footpath.

 

(iv) The railings of existing bridges shall be replaced by crash barriers, where specified in Schedule-B of the Concession Agreement.

 

(v) Parapets/Railings of the existing bridges/culverts to be repaired/replaced shall be specified in Schedule-B of the Concession Agreement.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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