Sivakumar Babu G L, Professor, Department of Civil Engineering, Indian Institute of Science, Bangalore
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 of the expansion and contraction of deck. In turn, they create maintenance and installation problems associated with the joints. In this regard, Integral Abutment Bridge (IAB) is an effective and economical alternative for conventional bridges. The IABs eliminate the need to provide deck joints and thereby alleviate the maintenance problem considerably. This paper provides a review on the integral abutment bridge construction method and also discusses the potential benefits of using IABs. It also enumerates few limitations associated with the integral bridges and illustrates some proposed measures to mitigate these problems.
IntroductionThe design of the conventional bridges as multiple simply supported spans always prompted the bridge engineers to deliberately install various joints and bearings at the supports. This was to check and allow the displacements due to cyclic thermal loading. However, the introduction of moment distribution method in 1930 by professor Hardy Cross, contemplated with new avenues in bridge design. This paved way for use of integral abutment type bridges. Integral abutment bridges are continuous bridges, where the deck is rigidly connected to the abutments and approach slabs. This rigid connection allows integral bridges to act as a single unit in resisting thermal and axle loads. A typical integral abutment bridge system is shown in Fig. 1. The need for jointless bridges evolved from the desire to eliminate the use of expansion joints and bearings. Here, in such kind of bridges, superstructure is constructed integrally with the abutments and normally these abutments are supported by rows of vertically driven flexible piles.
Integral abutment bridges have gained prominence throughout the United States from the 1930s and have since then become more common, especially for bridges with short, continuous spans. Traditionally the foundation of the abutments consists of a single row of flexible piles that are placed in pre augured holes up to a certain depth . The holes are then backfilled with granular material. The pile heads are either fixed at the point of connection with the abutment walls or they are pinned. They also include an approach system where an approach slab is in immediate connection with the deck and abutment.
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