Repair of a Major Bridge; Some Thoughts on Repair Materials

Dr. S. K. Manjrekar, Chairman and Managing Director, Sunanda Speciality Coatings Pvt. Ltd, Mumbai.
The paper discusses repair and rehabilitation of a major road over bridge connecting eastern and western suburbs of Andheri, Mumbai. While the case study is described, the author dwells upon some of the important aspects involved in selection of appropriate materials and methodologies of repair/ rehabilitation.

Rehabilitation of reinforced concrete (RC) bridges prematurely or otherwise damaged, continue to be a major problem throughout India. The problem is more serious in the coastal areas and is aggravated further in the highly polluted cities like Mumbai. Many bridges need major repairs. In view of the need to maintain continuous traffic flow on the bridge the repair methodology assumes great importance. A case in point is the repair to the Gopal Krishna Gokhale (GKG) Bridge, connecting S. V. Road and the Western Express Highway in a suburb of Mumbai.

Major rehabilitation work of the western approach of this bridge has been just concluded. It was carried out in very trying conditions of continuous traffic flow matched with the serious damage taken place over the years. This paper is an effort to understand the nature of damage and then the logical solution to repairs based on the latest understanding of the materials, particularly polymers and polymer-modified mortars/ concretes. An attempt is also made to explain the mechanisms involved. This is with the expectation that this case study which is possibly first example of its type in terms of the expanse of the job and large quantities of materials required can be a guidance for posterity to assess and carry out such bridge repairs in the future.

Salient Features of the Bridge

The salient features of the GKG bridge are as below :

1. Year of construction : 1969
2. Width of bridge : 27.45 m
3. Superstructure on railway track : Structural steel On approaches : RCC T-beam and slab (total length 160m;100 m on the western side and 60m on the eastern side.)
4. Substructure: 12 RC columns (the area below RC Approaches is enclosed and used as offices)
5. No. of girders per span: 12
6. Thickness of deck Slab:250 mm
7. Bearings: roller and rocker rocker roller type steel bearings
8. Foundation: open
9. Total length of approaches: Eastern side–240 m Western side–220 m