Precast Pre Stressed Concrete Bridges
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PRECAST PRESTRESSED CONCRETE BRIDGES
SAAGAR L. BHATIA
050901001
BRIDGE
A bridge is a structure built to span a valley, road, body of water, or other physical obstacle, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge and the nature of the terrain where the bridge is constructed.
Types of bridges
There are six main types of bridges:
beam bridges,
cantilever bridges,
arch bridges,
suspension bridges,
cable-stayed bridges
truss bridges.
FORCES
Bridges
may
be
classified
by
how
the
forces
of
tension, compression, bending, torsion and shear are distributed through their structure. Most bridges will employ all of the principal forces to some degree, but only a few will predominate. The separation of forces may be quite clear. In a suspension or cable-stayed span, the elements in tension are distinct in shape and placement. In other cases the forces may be distributed among a large number of members, as in a truss, or not clearly discernible to a casual observer as in a box beam.
PRESTRESSED CONCRETE
Prestressed
concrete is
a
method
for
overcoming the concrete's natural weakness in tension. It
can
be
used
to
produce beams, floors or bridges with
a
longer span than is practical with ordinary reinforced concrete. Prestressing tendons (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a compressive stress that offsets the tensile
stress that
concrete compression
the
member would
otherwise experience due to a bending load. Traditional reinforced concrete is based on the use of steel reinforcement bars, rebar's, inside poured concrete.
PRECAST CONCRETE
Precast concrete is a form of construction, where concrete is cast in a reusable mould or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, standard concrete is poured into site specific forms and cured on site.
By producing precast concrete in a controlled environment , the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. There are many different types of precast concrete forming systems for architectural applications, differing in size, function and cost.
Modern uses for precast technology include a variety of architectural and structural applications featuring parts of or an entire building system.
The advantages of using precast concrete is the increased quality of the material, when formed in controlled conditions, and the reduced cost of constructing large forms used with concrete poured on site.
PRECAST PRESTRESSED CONCRETE
Precast and prestressed concrete is now the dominant structural material for short to medium span bridges. With its inherent durability, low maintenance and assured quality, precast and prestressed is a natural product for bridge construction. The ability to quickly erect precast concrete component in all types of weather with little disruption of traffic adds to the economy of the job. For short spans(spans to 100 ft), use of box sections and double tee sections have proven economical. However, the most common product for short to medium spans in the I-girder. Spans to 150 to 160ft are not uncommon with I-girders. Spliced girders allow spans as much as 300ft. Even longer spans can be achieved using precast box girder segments which are then post-tensioned together in the field. Using cable stays, the spanning capability of precast and prestressed concrete has been increased to over 1000ft.
An important innovation in bridge construction has been the use of precast concrete in horizontally curved bridges.
Another application of precast and prestressed concrete in bridge construction includes the use of precast deck panels. Used as stay in place forms, the panels reduce field placement of reinforcing steel and concrete resulting in considerable savings.
The speed and variety of precast prestressed products and methods give designers many options.
B e n e fits to B e n e fits to O w n e r A g e n cie s : R e d u ctio n in th e d u ra tio n o f C o n tra cto rs : R e d u ce d exp o su re to w o rk zo n e s h a za rd s R e d u ce d tra ffic h a n d lin g co sts M o re w o rk -- le ss tim e R e d u ce d a ccid e n t exp o su re Fe w e r w e a th e r d e la ys risks Lo w e r co sts Le ss in co n ve n ie n ce to th e Le ss skille d la b o r tra ve lin g p u b lic N o cu rin g tim e Fe w e r m o to rist co m p la in ts
BANDRA WORLI SEA LINK
The Bandra Worli Sea Link would be an 8-lane , cable-stayed bridge
with pre-stressed concrete viaduct approaches, which links Bandra
and the western suburbs of Mumbai with Worli and central Mumbai,
and is the first phase of the proposed West Island Freeway system.
The Sea Link is likely to reduce travel time between Bandra and Worli
from 45–60 minutes to 7 minutes. The link has an average daily traffic
of around 25,000 vehicles on weekdays.
The project starts from the intersection of Western Express Highway and SV Road at the Bandra end, and connects it to Khan Abdul Gaffar Khan Road at the Worli end.
MAIN BRIDGE STRUCTURE The proposed Link Bridge consists of twin continuous concrete box girder bridge sections for traffic in each direction. Each bridge section except at the cable - stayed portion is supported on piers typically spaced at 50 meters. Each section is meant for four lanes of traffic complete with concrete barriers and service side walks on one side. The bridge alignment is defined with vertical and horizontal curves. The Link Bridge layout is categorized into three Part different 1 - The north end approach structure parts:
mainly with precast (PC) segmental construction Part 2 - The Cable Stayed Bridge at Bandra channel is with 50m - 250m - 250m - 50m span arrangement and the Cable Stayed Bridge at Worli channel is with 50m - 50m - 150m - 50m - 50m span arrangement Part 3 - The south end approach structure mainly with precast segmental construction
PART - I NORTH END APPROACH STRUCTURE
The bridge is arranged in units of typically six continuous spans of 50 meters each. Expansion joints are provided at ends of each unit.
Provision for access ramp to connect to Bandstand road below Searock Hotel. Span arrangement for this structure provides for cast in-situ spans.
The superstructure & substructure are designed in accordance with IRC codes. Specifications conform to the IRC standard with supplementary specifications covering special items. The sub structure consists of 1.5 meters diameter drilled piles with pile caps & some of the piers near Worli end will be directly socketed into the rock.
Bridge is proposed to be built utilizing the concept of precast, post tensioned, twin segmented concrete box girder sections. An overhead gantry truss crane with self - launching capability is proposed. The PC segments are epoxied together with nominal prestressing. The end segments adjacent to the pier would be short segments "cast - in - situ". Geometrical adjustments are
PART- II CABLE STAYED BRIDGE
The cable - stayed portion of the Bandra channel is 600 meters in overall length between expansion joints and consists of two 250 meters cable supported main spans flanked by 50 meters conventional approach spans. A centre tower with an overall height of 128 meters above pile cap level supports the superstructure by means of four planes of stay cables in a semi fan arrangement.
The cable - stayed portion of the Worli channel is 350 meters in overall length between expansion joints and consists of two 150 meters cable supported main spans flanked by 50 meters
A total of about 264 stay cables will be required for the cable stayed spans at Bandra channel with cable lengths varying from approximately 85 meters minimum to nearly 250 meters maximum. The tower is cast - in - situ reinforced concrete using the climbing form method of construction. The overall tower configuration is an inverted "Y" shape with the inclined legs oriented along the axis of the bridge. Tower cable anchorage's are achieved by use of formed pockets and transverse and longitudinal bar post - tensioning is provided in the tower head to resist local cable forces.
A total of about 160 stay cables will be required for the cable stayed spans at Worli channel with cable lengths varying from approximately 30 meters minimum to nearly 80 meters maximum. The tower is cast - in - situ reinforced concrete using the climbing form method of construction. The overall tower configuration is "I" shape with the inclined legs. Tower cable anchorage's are achieved by use of formed pockets and
PART - III SOUTH END APPROACH STRUCTURE
This portion of the bridge is similar to the North end approach structure in construction methodology with span by span match cast concrete box girder sections. Similar to the north end approach detailed, access ramps shall be provided for connection to the western freeway
BANGABANDHU BRIDGE,BANGALADESH
Bangabandhu Bridge, also called the Jamuna Multi-purpose Bridge , is a bridge opened in Bangladeshin June 1998. It is the eleventh longest bridge in the world and the second longest in South Asia. It is amongst the longest bridges in the world. It was constructed over the Jamuna River.
The bridge established a strategic link between the eastern and western parts of Bangladesh. It generated various benefits for the people and especially, promoted inter-regional trade in the country. Apart from quick movement of goods and passenger traffic by road and rail, it facilitated transmission of electricity and natural gas, and integration of telecommunication links. The main bridge is 4.8 km long with 47 main spans of approximately 100 metres
The crossing has been designed to carry a dual two-lane carriageway, a dual gauge railway, telecom cables and a 750 mm diameter high pressure natural gas pipeline. The carriageways are 6.315 metres wide separated by a 0.57 metre width central barrier; the rail track is located along the north side of the deck. On the main bridge, electrical
interconnector pylons
are
positioned
cantilevered from the north side of
the deck. Telecommunication ducts run through the box girder deck and the gas pipeline is
located under the south cantilever of the box
section.
on
brackets
SPECIFICATION
Considering the fact that the width of the main channel does not exceed 3.5 km, and after making allowances for floods, a bridge length of 5 km was considered adequate. In October 1995, one year after the commencement of physical work of the bridge, a bridge length of 4.8 km, instead of a flood-width of the river at 14 km, was finalised. This narrowing was essential to keep the overall project cost within economic viability. It has, however, required considerable river training work to keep the river under the bridge.
To withstand predicted scourge and possible earthquakes, the bridge is supported on 80-85 meter long and 2.5 meter and 3.15 meter diameter steel piles, which were driven by powerful (240ton) hydraulic hammer. The superstructure of the bridge is precast segments erected by the balanced cantilever method. Basic features of the bridge are: length (main part) - 4.8 km; width 18.5 metre; spans - 49; deck segments - 1263; piles - 121; piers - 50; road lanes - 4; railway tracks - 1 dual gauge.
SUB - STRUCTURE
The bridge is supported on tubular steel piles, approximately 80 metres in length, driven into the river bed. Sand was removed from within the piles by airlifting and replaced with concrete. Out of the 50 piers, 21 piers are supported on groups of 3 piles (2.5 m diameter) and 29 piers on groups of 2 piles (3.15 diameter). The driving of 121 piles started on October 15, 1995 and was completed in July 1996. The pier caps, p re ca st a n d stems in fille dare w ithfounded in -situ reon in foconcrete pile rce d whose shells were co n cre te . T h e re in fo rce d co n cre te p ie r ste m s su p p o rt p ie r h e a d s w h ich co n ta in b e a rin g s a n d se ism ic d e vice s. T h e se a llo w m o ve m e n t o f th e d e ck u n d e r n o rm a l lo a d in g co n d itio n s b u t lo ck in th e e ve n t o f a n e a rth q u a ke to lim it o ve ra ll se ism ic lo a d s th ro u g h th e stru ctu re a n d m in im ise
SUPER STRUCTURE
The main bridge deck is a multispan precast prestressed concrete segmental structure, constructed by the balanced cantilever method. Each cantilever has 12 segments (each 4 m long), joined to a pier head unit (2 m long) at each pier and by an in-situ stitch at mid span. The deck is internally prestressed and of single box section. The depth of the box varies between 6.5 metres at the piers to 3.25 metres at mid-span. An expansion joint is provided every 7 spans by means of a hinge segment at approximately quarter span. The segments were precast and erected
SAAGAR L. BHATIA
050901001
BRIDGE
A bridge is a structure built to span a valley, road, body of water, or other physical obstacle, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge and the nature of the terrain where the bridge is constructed.
Types of bridges
There are six main types of bridges:
beam bridges,
cantilever bridges,
arch bridges,
suspension bridges,
cable-stayed bridges
truss bridges.
FORCES
Bridges
may
be
classified
by
how
the
forces
of
tension, compression, bending, torsion and shear are distributed through their structure. Most bridges will employ all of the principal forces to some degree, but only a few will predominate. The separation of forces may be quite clear. In a suspension or cable-stayed span, the elements in tension are distinct in shape and placement. In other cases the forces may be distributed among a large number of members, as in a truss, or not clearly discernible to a casual observer as in a box beam.
PRESTRESSED CONCRETE
Prestressed
concrete is
a
method
for
overcoming the concrete's natural weakness in tension. It
can
be
used
to
produce beams, floors or bridges with
a
longer span than is practical with ordinary reinforced concrete. Prestressing tendons (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a compressive stress that offsets the tensile
stress that
concrete compression
the
member would
otherwise experience due to a bending load. Traditional reinforced concrete is based on the use of steel reinforcement bars, rebar's, inside poured concrete.
PRECAST CONCRETE
Precast concrete is a form of construction, where concrete is cast in a reusable mould or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, standard concrete is poured into site specific forms and cured on site.
By producing precast concrete in a controlled environment , the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. There are many different types of precast concrete forming systems for architectural applications, differing in size, function and cost.
Modern uses for precast technology include a variety of architectural and structural applications featuring parts of or an entire building system.
The advantages of using precast concrete is the increased quality of the material, when formed in controlled conditions, and the reduced cost of constructing large forms used with concrete poured on site.
PRECAST PRESTRESSED CONCRETE
Precast and prestressed concrete is now the dominant structural material for short to medium span bridges. With its inherent durability, low maintenance and assured quality, precast and prestressed is a natural product for bridge construction. The ability to quickly erect precast concrete component in all types of weather with little disruption of traffic adds to the economy of the job. For short spans(spans to 100 ft), use of box sections and double tee sections have proven economical. However, the most common product for short to medium spans in the I-girder. Spans to 150 to 160ft are not uncommon with I-girders. Spliced girders allow spans as much as 300ft. Even longer spans can be achieved using precast box girder segments which are then post-tensioned together in the field. Using cable stays, the spanning capability of precast and prestressed concrete has been increased to over 1000ft.
An important innovation in bridge construction has been the use of precast concrete in horizontally curved bridges.
Another application of precast and prestressed concrete in bridge construction includes the use of precast deck panels. Used as stay in place forms, the panels reduce field placement of reinforcing steel and concrete resulting in considerable savings.
The speed and variety of precast prestressed products and methods give designers many options.
B e n e fits to B e n e fits to O w n e r A g e n cie s : R e d u ctio n in th e d u ra tio n o f C o n tra cto rs : R e d u ce d exp o su re to w o rk zo n e s h a za rd s R e d u ce d tra ffic h a n d lin g co sts M o re w o rk -- le ss tim e R e d u ce d a ccid e n t exp o su re Fe w e r w e a th e r d e la ys risks Lo w e r co sts Le ss in co n ve n ie n ce to th e Le ss skille d la b o r tra ve lin g p u b lic N o cu rin g tim e Fe w e r m o to rist co m p la in ts
BANDRA WORLI SEA LINK
The Bandra Worli Sea Link would be an 8-lane , cable-stayed bridge
with pre-stressed concrete viaduct approaches, which links Bandra
and the western suburbs of Mumbai with Worli and central Mumbai,
and is the first phase of the proposed West Island Freeway system.
The Sea Link is likely to reduce travel time between Bandra and Worli
from 45–60 minutes to 7 minutes. The link has an average daily traffic
of around 25,000 vehicles on weekdays.
The project starts from the intersection of Western Express Highway and SV Road at the Bandra end, and connects it to Khan Abdul Gaffar Khan Road at the Worli end.
MAIN BRIDGE STRUCTURE The proposed Link Bridge consists of twin continuous concrete box girder bridge sections for traffic in each direction. Each bridge section except at the cable - stayed portion is supported on piers typically spaced at 50 meters. Each section is meant for four lanes of traffic complete with concrete barriers and service side walks on one side. The bridge alignment is defined with vertical and horizontal curves. The Link Bridge layout is categorized into three Part different 1 - The north end approach structure parts:
mainly with precast (PC) segmental construction Part 2 - The Cable Stayed Bridge at Bandra channel is with 50m - 250m - 250m - 50m span arrangement and the Cable Stayed Bridge at Worli channel is with 50m - 50m - 150m - 50m - 50m span arrangement Part 3 - The south end approach structure mainly with precast segmental construction
PART - I NORTH END APPROACH STRUCTURE
The bridge is arranged in units of typically six continuous spans of 50 meters each. Expansion joints are provided at ends of each unit.
Provision for access ramp to connect to Bandstand road below Searock Hotel. Span arrangement for this structure provides for cast in-situ spans.
The superstructure & substructure are designed in accordance with IRC codes. Specifications conform to the IRC standard with supplementary specifications covering special items. The sub structure consists of 1.5 meters diameter drilled piles with pile caps & some of the piers near Worli end will be directly socketed into the rock.
Bridge is proposed to be built utilizing the concept of precast, post tensioned, twin segmented concrete box girder sections. An overhead gantry truss crane with self - launching capability is proposed. The PC segments are epoxied together with nominal prestressing. The end segments adjacent to the pier would be short segments "cast - in - situ". Geometrical adjustments are
PART- II CABLE STAYED BRIDGE
The cable - stayed portion of the Bandra channel is 600 meters in overall length between expansion joints and consists of two 250 meters cable supported main spans flanked by 50 meters conventional approach spans. A centre tower with an overall height of 128 meters above pile cap level supports the superstructure by means of four planes of stay cables in a semi fan arrangement.
The cable - stayed portion of the Worli channel is 350 meters in overall length between expansion joints and consists of two 150 meters cable supported main spans flanked by 50 meters
A total of about 264 stay cables will be required for the cable stayed spans at Bandra channel with cable lengths varying from approximately 85 meters minimum to nearly 250 meters maximum. The tower is cast - in - situ reinforced concrete using the climbing form method of construction. The overall tower configuration is an inverted "Y" shape with the inclined legs oriented along the axis of the bridge. Tower cable anchorage's are achieved by use of formed pockets and transverse and longitudinal bar post - tensioning is provided in the tower head to resist local cable forces.
A total of about 160 stay cables will be required for the cable stayed spans at Worli channel with cable lengths varying from approximately 30 meters minimum to nearly 80 meters maximum. The tower is cast - in - situ reinforced concrete using the climbing form method of construction. The overall tower configuration is "I" shape with the inclined legs. Tower cable anchorage's are achieved by use of formed pockets and
PART - III SOUTH END APPROACH STRUCTURE
This portion of the bridge is similar to the North end approach structure in construction methodology with span by span match cast concrete box girder sections. Similar to the north end approach detailed, access ramps shall be provided for connection to the western freeway
BANGABANDHU BRIDGE,BANGALADESH
Bangabandhu Bridge, also called the Jamuna Multi-purpose Bridge , is a bridge opened in Bangladeshin June 1998. It is the eleventh longest bridge in the world and the second longest in South Asia. It is amongst the longest bridges in the world. It was constructed over the Jamuna River.
The bridge established a strategic link between the eastern and western parts of Bangladesh. It generated various benefits for the people and especially, promoted inter-regional trade in the country. Apart from quick movement of goods and passenger traffic by road and rail, it facilitated transmission of electricity and natural gas, and integration of telecommunication links. The main bridge is 4.8 km long with 47 main spans of approximately 100 metres
The crossing has been designed to carry a dual two-lane carriageway, a dual gauge railway, telecom cables and a 750 mm diameter high pressure natural gas pipeline. The carriageways are 6.315 metres wide separated by a 0.57 metre width central barrier; the rail track is located along the north side of the deck. On the main bridge, electrical
interconnector pylons
are
positioned
cantilevered from the north side of
the deck. Telecommunication ducts run through the box girder deck and the gas pipeline is
located under the south cantilever of the box
section.
on
brackets
SPECIFICATION
Considering the fact that the width of the main channel does not exceed 3.5 km, and after making allowances for floods, a bridge length of 5 km was considered adequate. In October 1995, one year after the commencement of physical work of the bridge, a bridge length of 4.8 km, instead of a flood-width of the river at 14 km, was finalised. This narrowing was essential to keep the overall project cost within economic viability. It has, however, required considerable river training work to keep the river under the bridge.
To withstand predicted scourge and possible earthquakes, the bridge is supported on 80-85 meter long and 2.5 meter and 3.15 meter diameter steel piles, which were driven by powerful (240ton) hydraulic hammer. The superstructure of the bridge is precast segments erected by the balanced cantilever method. Basic features of the bridge are: length (main part) - 4.8 km; width 18.5 metre; spans - 49; deck segments - 1263; piles - 121; piers - 50; road lanes - 4; railway tracks - 1 dual gauge.
SUB - STRUCTURE
The bridge is supported on tubular steel piles, approximately 80 metres in length, driven into the river bed. Sand was removed from within the piles by airlifting and replaced with concrete. Out of the 50 piers, 21 piers are supported on groups of 3 piles (2.5 m diameter) and 29 piers on groups of 2 piles (3.15 diameter). The driving of 121 piles started on October 15, 1995 and was completed in July 1996. The pier caps, p re ca st a n d stems in fille dare w ithfounded in -situ reon in foconcrete pile rce d whose shells were co n cre te . T h e re in fo rce d co n cre te p ie r ste m s su p p o rt p ie r h e a d s w h ich co n ta in b e a rin g s a n d se ism ic d e vice s. T h e se a llo w m o ve m e n t o f th e d e ck u n d e r n o rm a l lo a d in g co n d itio n s b u t lo ck in th e e ve n t o f a n e a rth q u a ke to lim it o ve ra ll se ism ic lo a d s th ro u g h th e stru ctu re a n d m in im ise
SUPER STRUCTURE
The main bridge deck is a multispan precast prestressed concrete segmental structure, constructed by the balanced cantilever method. Each cantilever has 12 segments (each 4 m long), joined to a pier head unit (2 m long) at each pier and by an in-situ stitch at mid span. The deck is internally prestressed and of single box section. The depth of the box varies between 6.5 metres at the piers to 3.25 metres at mid-span. An expansion joint is provided every 7 spans by means of a hinge segment at approximately quarter span. The segments were precast and erected
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