In-Situ Health Assessment of a Poorly Executed Pre-Stressed In-Service Concrete Bridge and Suggesting a Rehabilitation Strategy – A Case Study

A study is reported on a two lane in-service pre-stressed concrete bridge having susceptible vibrations under service traffic conditions. The bridge was 1300 ft long with thirteen simple pre- cast post tensioned spans resting on in-situ bridge piers. The client reported significant vibrations under service loads and requested a solution. The bridge did not have a top wearing surface. Bridge design drawings were provided. The methodology of health assessment included the visual inspection followed by analysis with the help of drawings provided by the client. The records of concrete strengths along with prestressing protocols were missing. The static and dynamic bridge response using static and moving three different loaded vehicles (over loaded tractor trolley, unloaded 5 Axle vehicle loaded trailer and loaded 5 axle trailers) was monitored. Core samples from the bridge deck were taken. NDT, Digital half-cell and electrical resistivity readings were taken at various locations of bridge. The results indicated some design inadequacies, faulty construction methodologies, improper maintenance and lack of awareness even by the professionals to deal with such structures. The remedial measures were suggested in terms of strengthening and maintenance of bridge.