Experimental research on hybrid anchorages of prestressed composite strips for structural strengthening

Abstract

The prestressed unidirectional carbon fibre reinforced polymer (CFRP) strips are currently often used for flexural strengthening of concrete structures. To ensure reliable strengthening, strips have to be anchored at their ends to the surface. However, anchoring of unidirectional CFRP strips is difficult because of their weak transversal mechanical properties. Although several CFRP strip anchorage approaches have been developed to date, only very few were applied on-site. The paper presents the development of hybrid bonded/bolted anchorages of CFRP strips used in a novel prestressing system. The anchorages are made of thin steel plates, clamped with the high-strength friction grip (HSFG) bolts and epoxy adhesive, to fix the CFRP strips. The paper describes the results of full-scale tests carried out on a series of axial tensile specimens. The developed anchorage has an ultimate tensile strength of about 200 kN, i.e. 70% of the ultra-high CFRP strips’ strength, which is sufficient for strengthening purposes. After a series of tests in the laboratory, the anchorages have been implemented on-site and an example is presented in the paper.