External Prestressing Technique for Strengthening of Prestressed Concrete Structural Components

This paper presents the details of an innovative external prestressing technique for strengthening of prestressed concrete girders. The technique has been developed for anchoring the external prestressing to the sides of the end block. In the proposed technique, transfer of external force is in shear mode on the end block and the required transverse prestressing force is smaller compared to conventional techniques. In order to validate the technique, an experimental investigation has been carried out on two posttensioned end blocks (EB-1 and EB-4). Steel brackets are provided on either side of the end block for transferring external prestressing force and these are connected to the anchor blocks by expansion-type anchor bolts. Performance of the end blocks has been studied for design, cracking, and ultimate loads. A ductile failure is observed in EB-1 whereas a sudden failure is observed in EB-4. The slip and slope of the steel bracket have been recorded at various stages during the experiment. These values are found to be smaller in EB-1 than in EB-4 due to a higher anchorage depth of bolts. Finite-element analysis has been carried out by simulating the geometry, loading, material nonlinearity, and test conditions. Linear and nonlinear static analysis has been conducted for the specified loadings and the responses have been compared. From the analysis, it has been observed that the computed slope and slip of the steel bracket are in good agreement with the corresponding experimental observations.