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INTEGRAL BRIDGESINTEGRAL BRIDGES

Presented by:Safar.N.NS7, Roll no:59Civil Engg Dept

Guided by: Dipu.V.S Lecturer Civil Engg Dept

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INTRODUCTION

Integral bridges in simple words, can be defined as bridges without joints. Integral bridges are characterized by monolithic connection between the deck and the substructure (piers and abutments). They span from one abutment, over intermediate support to the other abutment, without any joint in the deck. Integral bridges have been constructed all over the world including India.

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WHAT IS AN INTEGRAL BRIDGE?

Bridges constructed without any expansion joint (between spans or between spans and abutments) and without any bearings are called integral bridges.

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CHARACTERISTICS OF INTEGRAL BRIDGES

The integral abutment bridge concept is based on the theory that due to the flexibility of the piling, thermal stresses are transferred to the substructure by way of a rigid connection between the superstructure and substructure

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MOTIVATION BEHIND INTEGRAL BRIDGES

To eliminate expansion joints in the deck

When earthquake forces are predominant or when consideration like increased resistance to blasts the integral bridge concept is an excellent option.

Less expensive

Improved durability

Easy to design

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WHY GO FOR INTEGRAL BRIDGES?

The expansion joints and bearings, by virtue of their functions are sources of weakness in the bridge and there are many examples of distress in bridges, primarily due to poor performance of these two elements

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Leaking of expansion joints and seals permit the surface run-off water from roadway

Continual wear and heavy impact from repeated live loads as well as continual stages of

movement from expansion and contraction

Impact loadings from heavy commercial vehicles

Elastomeric bearings can split and rupture due to unanticipated movements, or ratchet

out of position.

Malfunctioning of bearings can lead to unanticipated structural damage

Joints and bearings are expensive

PROBLEMS OF EXPANSION JOINTS AND BEARINGS

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INTEGRAL ABUTMENT

The integral abutment is defined as abutment, which is connected to the bridge deck without any movement joint for expansion or contraction of the deck

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WHY GO FOR INTEGRAL ABUTMENTS

1.Simple Design

2.Joint less construction

3.Resistance to pressure

4.Rapid construction

5.Ease in constructing embankments

6.No cofferdams

7.Vertical piles (no battered piles)

8.Simple forms

9.Few construction joints

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10.Reduced removal of existing elements

11.Simple beam seats

12.Simplified widening and replacement

13.Lower construction costs and future maintenance costs

14.Improved ride quality

15. It Design efficiency

16.Added redundancy and capacity for catastrophic events

17.Improve Load distribution

18.Enhance protection for weathering steel girders

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PLANNING CONSIDERATIONS1.Length of the Structure

2.Climatic Condition

3.Seismic Zone

4.Type of Superstructure

5.Type of Abutments

6.Type of Foundations And Sub-Soil Conditions

7.Geometry of the Structure

8.Complexity in Analysis and Design

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RECOMMENDED QUALITY IMPROVEMENT PRACTICE FOR

INTEGRAL BRIDGES Develop design criteria or office practices for designing integral abutment and join less bridges

In extending the remaining service lives of existing bridges

exchange information in the areas of design, construction and maintenance of joints and joint less bridges

The decision to install an approach slab should be made by the Bridges and Structures Office, with consultation from the Geotechnical group

Standardize practice of using sleeper slabs at the end of all approach slabs

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1. Simplified details for construction2. Reduced life cycle cost and long term maintenance3. Improved design efficiency Improved riding quality4. Added redundancy with improved seismic performance Ease in constructing embankments5. Elimination of water leakage on critical structural elements6. Lesser tolerance restriction due to elimination of bearings and expansion joints7. Faster construction8. Simplified widening and replacement detail Useful for strengthening of existing bridges

ADVANTAGES OF INTEGRAL BRIDGES OVER CONVENTIONAL

BRIDGES

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ILLUSTRATIVE EXAMPLE

1. Dankuni-Palsit FlyoverIt is situated at the durgapur Expressway. The span arrangement for the overpass is15m + 2x22.0 m + 15m,continuous over the support. The deck is RC solid slab type integral with the twin piers. The bridge is a joint less bridge without any expansion joint over intermediate piers without any bearings

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2. Kalkaji FlyoverA 150m integral flyover has been provided at the vital T-junction on Ring Road near Kalkaji Temple. The typical five span continuous deck (25m + 30m + 40m + 30m + 25m), has a voided slab reinforced concrete deck with a depth of 1.70m, which was hunched and increased to 2.20m at the piers supporting the 40.0m obligatory main span.

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CONCLUSION

In conclusion, it must be said that the final product represented by the integral bridge is vastly superior in performance in service conditions as compared to traditional bridges with bearings and expansion joints.

References Alok Bhowmick,2005, Design and detailing of integral

bridges:Suggested guidelines;The Indian Concrete Journal,79(9),pp 43 – 50.

Alok Bhowmick,2003,Design and construction of integral bridges- An innovative concept, The Indian Concrete Journal,77(7),pp 22 – 35.

www.nabro.unl.edu www.cbdg.org 1. WALLBANK, E. The performance of concrete in bridges – a survey of

200 highway bridges, HMSO, London, 1989, 96pp 2 NICHOLSON, B. Integral abutments for prestressed beam bridges,

British Precast Concrete, Federation, Leicester, 1998, 84pp. difficult to accommodate in design. ENGLAND, G., TSANG N. and BUSH, D. Integral bridges: a

fundamental approach to the time–temperature loading problem, Thomas Telford, London, 1999, 144pp.

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