Partha Pratim Roy, General Manager (Technical), ADAPT International Pvt. Ltd. Kolkata

Most Modern Bridges are Built Segmentally. In such bridges, the components carry loading in a configuration other than thecompleted structure. Stress during construction exceeds that of the completed structure. Early-age loading of concrete results in large deformations. Bridge engineers must keep these aspects in mind while designing segmental bridges. Major design objectives are:
  • Geometry Control During Construction (Deflection and Camber)
  • Crack Control During Construction (Stress Check)
  • Structural Safety and Stability During Construction
  • Control of Stresses in Completed Structure
  • Control of Strength of Completed Structure

Evolution of Concrete Bridge Geometry

Simple Span & Support

Initially, the best and possible way was to opt for Simply Supported Span Bridges. That was easy to construct, but required huge sections. Still for certain cases and specific requirements, it is practical to go ahead with such combinations.

Later the concept of Continuous Span Bridges came up, where more economic section utilization was possible. To save construction time Precast Prestressed concrete sections (PCPS) are castand carried to job site from casting yard; erected over pier and finally spliced over supports. Needless to mention these sections are pretensioned. It helps to establish continuity for live load distribution to achieve longer spans (generally upto 40m). Compared to Single Span bridges, sudden change of slopes can be avoided which allows improved maintenance and quality of ride. However, potential possibilities of crack formation at the joints (non-prestressed) still exists.

To overcome the potential of crack formation, the concept of post-tensioning got introduced (PCPS with Post-Tensioning over the Supports only). It allows the engineer to achieve following advantages:
  • Continuity established for live load
  • Better performance of joints due to presence of precompression at the joints
  • Reduction of Dead Load Moment
  • Thinner, and longer spans
Later engineers started using the advantages of PT (Post-Tension) over the entire legth of bridge frame. This time Post-Tensioning directly participates in resisting positive moment at mid-span. Deflections are also controlled more effectively. Longer spans (more than 60 meter) are achievable. This concept also provides added economy by reducing the number of piers.

However, still at this stage Bridge geometry was restricted by non-technical parameters like limitation of transportation in length and width of members. Moreover, weight of sections were limited by the available crane capacity and lifting equipment. Hence the new concept got introduced when small pieces are casted and transported to job site; erected in place and hold with bracket to be spliced. Longer spans of 100 meter or more are achievable in this process and no of piers can be reduced to achieve economy.

About Segmental Construction

As its name implies, a segmental bridge is a bridge built in short sections (called segments), i.e. one piece at a time, as opposed to traditional methods that build a bridge in very large sections. The bridge is made of concrete that is either cast-in-place (constructed fully in its final location) or precast concrete (built at another location and then transported to their final location for placement in the full structure).

These bridges are very economical for long spans (over 100 meters), especially when access to the construction site is restricted. They are also chosen for their aesthetic appeal.

History

  • 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.
  • The first U.S. precast segmental concrete bridge, built in 1973, in Corpus Christi, Texas.
  • The first U.S. cast-in-place segmental bridge, built in 1974, was built near San Diego, California.
  • The first U.S. precast segmental oncrete arch bridge is the Natchez Trace Parkway Bridge, completed in 1993.

Construction

The sequence of construction is similar to traditional concrete bridge building, i.e. build the support towers (columns), build the temporary falsework, build the deck, and perform the finishing work. The principle differences are as follows:
  • The support towers may be built segmentally. Often this is accomplished using “slip-form” construction, where the falsework moves (slips) upward following sequential concrete “pours.” The falsework uses the newly constructed concrete as the basis for moving upward.
  • After the towers are built, a superstructure is built at top of the towers. This superstructure serves as the “launching” point for building the deck. (The deck is often built in both directions away from the tower, simultaneously.)
  • The deck is now constructed sequentially, beginning at the tower, one section at a time.
  • In cast-in-place bridges, the falsework is connected to the previously installed concrete and allowed to cantilever freely. Next, the permanent reinforcing steel and supports are installed. Finally, the concrete is placed and cured, freeing the falsework to be moved.
  • In pre-cast bridges, the concrete segment is constructed on the ground, and then transported and hoisted into place. As the new segment is suspended in place by the crane, workers install steel reinforcing that attaches the new segment to preceding segments. Each segment of the bridge designed to accept connections from both preceding and succeeding segments.
  • The process in step 3 is repeated until the span is completed.

Notable Projects

  • Guiniguada Viaduct, Madrid, Spain
  • Aswan Cable Stayed bridge in Egypt span 250m
  • Lane Ave Bridge, Ohio 110 m long Cable stayed bridge
  • Benicia-Martinez NW Ramp, California, for CALTRANS, balanced cantilever, length 211m, 4 spans
  • Ramirez de Arellano Guideway Puerto Rico for H2A Engineers, post-tensioned railroad viaduct, 161m, 5 spans
  • Bayou Chico Channel over SR292 in Florida, composite construction, 168m, 3 spans
  • Arch bridge with cable stay construction, Sommerset, Florida, 163m
  • Arch bridge over river Beas and Viaducts at Ramshila (NH-21) on Kulu bypass in Himachal Pradesh, arch base approx 100m
  • Ganga Bridge, Allahabad (NHAI Project)
  • Monorail people movers in Las Vegas, Seattle and presently in Dallas
  • Delhi Gurgaon Expressway, Delhi (Continuous Box Girder Bridge)
  • Cantilever Bridge Over River Chenab between Bakkal and Kauri in Jammu & Kashmir

References

  • Wikimedia Foundation, Inc.
  • ADAPT Corporation
  • Presentation by Dr. Bijan O. Aalami
Click Here
To Know More or to Contact the Manufacturer
Please let us know your name.
Invalid Input
Please let us know your Designation.
Please let us know your Contact Number.
Please let us know your email address.
Please brief your query.
Our other Value-Added Services:

To receive updates through e-mail on Products, New Technologies & Equipment, please select the Product Category(s) you are interested in and click 'Submit'. This will help you save time plus you will get the best price quotations from many manufacturers, which you can then evaluate and negotiate.

Invalid Input
Invalid Input
Invalid Input
As part of Northeast Policy, the Ministry of Railways took up the project of providing rail connectivity to Imphal in Manipur state. As per the detailed survey, the rail alignment takes off from existing Jiribam

Read more ...

Brahmaputra is one of the longest river in Asia with a total length of 2880 km & out of which 920km (approx.) lie in India. The New Brahmaputra Bridge @ Tezpur is one of the most challenging one, in the attempt to bridge

Read more ...

The road and railway crossing across the Brahmaputra on National Highway-52B is located at Bogibeel, about 17km downstream of Dibrugarh in Assam. The location is an area of high intensity rainfall (the annual rainfall ranges

Read more ...

The world has progressed beyond imaginations. Similar to the field of IT, Civil Engineering has also taken several steps forward to bring out innovative technologies to meet challenges of this world’s aspirations. Going forward from

Read more ...

The bridge lies in the state of Assam, but this location is usually referred to as upper Assam as it is far away from Guwahati and bordering China. The nearest airport is Dibrugarh. Then there is a drive of 65km into the

Read more ...

The Infrastructure Industry is continuously evolving; new roads, elevated corridors, expressways, railways, dedicated corridors, metros, mono-rails are being constructed all the time. They also require constant

Read more ...

The 6.5 feet wide walkway in the Hongyagu Scenic Area in Hebei province hangs 755 feet above the ground, and is the world's longest bridge, which opened in 2017-end. Designed by Tel Aviv architect Haim Dotan

Read more ...

Prestressed Concrete (PSC) structures especially bridges are being largely used all over the world due to their multifarious advantages in terms of structural behaviour, economy as well as aesthetical

Read more ...

Four Span Pipe Bridge
Distressed structures require necessary remedial measures in order to restore their original structural properties like strength and stiffness. Validating the effectiveness of the proposed qualitative remedial

Read more ...

Foot Bridges
Footbridges have a longer history than road or railway bridges. Ancient footbridges comprised of natural materials such as roots of trees, ropes, stones, masonry, and wood. Modern footbridges are built

Read more ...

Thane Creek Bridge
Load testing is done to determine the safe load carrying capacity of structures, determining if specific legal or overweight vehicles can safely cross the structure or needs to be restricted and the level of post

Read more ...

Bridge in Central Kerala
Cement concrete is a versatile building material and is the second most consumed material in the world, after water. It is made using porland cement, coarse, and fine aggregates, water and one or more

Read more ...

Concrete Road Bridges
Planning, design and construction of bridges and flyovers is very challenging at places with space constraints. There has been rapid development with the availability of high strength steel and concrete

Read more ...

Integral Abutment Bridges
The conventional bridges use expansion joints and bearings to accommodate the thermal movements of the bridge. However, they don't completely eliminate the distress caused because

Read more ...

Bridge Restoration
The use and advantages of Post Tensioning are very well known in the Civil Engg Industry as it has been in use for the last 40 to 50 years. Post tensioning is one of the best methods to induce stresses in the concrete

Read more ...

Signature Bridge
Wazirabad Bridge or Signature Bridge Project is an initiative of Delhi Government, planned during the Commonwealth Games. It was conceptualized to be a landmark tourist icon that would also speed

Read more ...

Integral Abutment Bridge
An integral bridge may be defined as having no expansion joints or sliding bearings, the deck is continuous across the length of the bridge. Integral bridges are alternatively referred to as integral abutment

Read more ...

Soil Structure Interaction
A type of bridge that is used extensively in road applications in particular is the integral abutment bridge (IAB). The concept of "integral abutment bridge" has recently become a topic of remarkable

Read more ...

Cracks in Ravi Bridge
Before carrying out any testing of the concrete structures using NDT methods, visual inspection of the structure is a must. Visual inspection is not confined to the surface, it also include examination of bearings

Read more ...

Mithi River Bridge
Strengthening of RCC structural elements is a common task for maintenance nowadays. For the purpose of strengthening, several materials and methods are available such as sprayed concrete

Read more ...

×
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.