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INTEGRAL BRIDGES


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.


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.


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


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


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


PROBLEMS OF EXPANSION JOINTS AND BEARINGS
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


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



WHY GO FOR INTEGRAL ABUTMENTS
Simple Design
Joint less construction
Resistance to pressure
Rapid construction
Ease in constructing embankments
No cofferdams
Vertical piles (no battered piles)
Simple forms
Few construction joints
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


PLANNING CONSIDERATIONS

Length of the Structure
Climatic Condition
Seismic Zone
Type of Superstructure
Type of Abutments
Type of Foundations And Sub-Soil Conditions
Geometry of the Structure
Complexity in Analysis and Design

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


ADVANTAGES OF INTEGRAL BRIDGES OVER CONVENTIONAL BRIDGES

1. Simplified details for construction
2. Reduced life cycle cost and long term maintenance
3. Improved design efficiency Improved riding quality
4. Added redundancy with improved seismic performance Ease in constructing embankments
5. Elimination of water leakage on critical structural elements
6. Lesser tolerance restriction due to elimination of bearings and expansion joints
7. Faster construction
8. Simplified widening and replacement detail Useful for strengthening of existing bridges

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.