Technique to assess the residual prestress in prestressed concrete members

SummaryThe application of experimental techniques for the determination of available residual prestress in in-service structures is necessary to assess the health of the structure and also to support rehabilitation measures, if required. The concrete core trepanning technique has been found to be useful for the determination of residual prestress in prestressed concrete structures. Experimental studies were carried out in the laboratory to establish the reliability of the technique. The core trepanning technique is simple to handle. Moreover this technique can be almost classified as a non-destructive technique since the structure can continue to be in service even after testing. Since the method of core trepanning has the possibility of introducing some minor errors, the estimation of residual prestress from only one (or) two cores is not advisable. Hence a statistical approach has to be made from a fairly large number of measurements to obtain the probable value with reasonable reliability rather than an exact value.