Strengthening of concrete structures with prestressed and gradually anchored CFRP strips

Today post-strengthening of structures with externally bonded CFRP strips is state of the art. To take full advantage of this expensive material, it is beneficial to apply the strips in a prestressed state. This relieves the stresses in the internal steel reinforcement and reduces crack widths and deflections. Due to the limited shear strength of concrete, the high shear stresses at the ends of the strips cannot be transferred into the structure. To prevent premature failure of the system, the strips have to be anchored with special devices. Those are expensive, difficult to install and often subject to corrosion. These are the major reasons why prestressed, externally bonded CFRP strips have not yet been used in practice.

To overcome these anchorage problems, the prestressing force can be reduced gradually towards both ends of the strip. The result is an increased development length of the prestressing force such that the occurring shear stresses remain within the limitations of concrete. This can be achieved by using a purposely developed pretensioning device which allows the CFRP strips to be bonded to the concrete structure using a stepwise approach.

• INTRODUCTION

• EXTERNAL REINFORCEMENT WITH CFRP STRIPS

• ANCHORAGE OF PRESTRESSED CFRP STRIPS

• PRESTRESSING DEVICE

• GENERATE GRADUAL ANCHORING

• RESULTS

• CONCLUSIONS

• References