Load Testing of Second Thane Creek Bridge, Mumbai

Dr. Rajeev Goel, Senior Principal Scientist, Bridges and Structures, CSIR-Central Road Research Institute, New Delhi.

Introduction
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 posting required. Where member strength cannot be adequately determined from the results of in-situ material tests, load testing may be necessary. Experiences have shown that the structure located in marine environments suffer damages slow and steadily over the years, the damages become severe enough to lower the load carrying capacity of the structure along with speed restrictions.

This paper gives the details of the load testing of the bridges through a case study of second Thane Creek in Mumbai.

Description of Bridge
The second Thane Creek bridge, Mumbai has two independent carriageways (namely north and south) and was constructed in the year 1994. General view of the bridge is shown in Fig.1. The length of north carriageway of the bridge is 1837.09 m. It has 23 spans which comprises of six units and each unit consists of four continuous spans as shown in Fig.2 and Fig.3. The carriageway width is 11 m with 600 mm wide footpath on upstream (U/S) side and 890 mm central median on downstream (D/S) side. The superstructure consisting of single cell prestressed concrete box girder cross-section (refer Fig.4) of 6.5m width and varying depth 7.0m at support, reducing to 3.5m at mid-span was constructed by the free cast in-situ cantilever construction method. The superstructure of each unit is supported over POT-PTFE bearings (four POT-PTFE bearings) on the fixed pier (central) and a combination of POT-PTFE sliding and guide bearings on the remaining four piers. Finger type expansion joints have been provided in superstructure of the bridge.