A non-destructive method for prestress evaluation

As part of an investigation to evaluate prestressed concrete girder bridges, a new nondestructive technique has been developed to measure directly the available prestress in prestressed concrete girders. The new non-destructive technique is stress based and overcomes many of the weaknesses of the previous strain based techniques. The technique has been validated with a series of laboratory tests and finite element analyses. Further,the available prestress in a 25-year old prestressed girder has been predicted by the method with an acceptable accuracy.