Bond between concrete and reinforcement enables the transfer of forces from the reinforcement to the surrounding concrete. The load-deformation behaviour of reinforced and prestressed concrete members in the cracked state is largely influenced by the bond behaviour. Contrary to reinforcing and pre-tensioning steel the bond behaviour of post-tensioning tendons has not been the subject of much research. The present project aims at filling this gap.
Important influences on the bond behaviour of post-tensioning tendons will be investigated by performing 36 large-scale experiments. Test parameters include
(i) the tendon size;
(ii) the kind of duct (steel or plastic);
(iii) the grout strength;
(iv) the presence of a corrosion inhibitor (Rustban 310); and
(v) the direction of loading (loading e.g. due to live load or unloading e.g. due to cutting of a tendon).
Previously developed theoretical models of the bond behaviour of partially prestressed concrete members will be refined and simplified for practical applications.
28 tests on large-scale prismatic specimens will be performed to investigate the bond behaviour of post-tensioning tendons.
In addition, eight tests will be performed to investigate whether a corrosion inhibitor may be used in conjunction with (fixed) bond anchorages.
Based on these tests the tension chord model for partially prestressed concrete members developed at the Institute of Structural Engineering of the ETH in Zurich, Switzerland, was refined.
As a conclusion of the project, the bond behaviour is simplified for practical applications. It can be seen, that for bond related problems of strands in post-tensioned concrete a bond shear stress of 2 N/mm2 can be applied for calculations in the serviceability limit state. For a refined analysis and the verification of a sufficient bond capacity bond laws are given that include the influence of the pull-out force and the duct material.
Transition of research findings into practice through publications in scientific journals as well as training courses and standard proposals.