Experimental and numerical investigations of bond between CFRP and concrete

It is known that the bonding failure between concrete and externally bonded CFRP-strips sets in where high shear forces and high bending moments occur. Despite this knowledge, experimental and theoretical studies had been exclusively focused on the situation at the end of the CFRP-strip until 2000–2001. Since then theoretical work on the bonding between concrete and externally bonded laminate at a section between two cracks has been done. But neither experimental nor numerical studies on a section between two cracks have been carried out. For experimental studies a test set-up has been developed, in order to simulate geometrical and mechanical conditions between two cracks of a post-strengthened concrete slab. Nine test series with 67 tests at a section between two cracks have been carried out. Thirty-seven tests were bonding tests without a relative displacement at crack-surface and 30 tests were bonding tests with a relative displacement. A three-dimensional finite element model with solid and shell elements has been used for numerical calculations. This paper undertakes to describe the results of these test series, the results of the finite element calculations and a mathematical algorithm to considerate an incline of the laminate at the calculation of the maximum stress difference at a section between two cracks.