Pull-out tests of steel-encased specimens subjected to reversed cyclic loading

When deformed bars are anchored in concrete, this gives rise not only to bond stresses but also to splitting stresses. To measure the splitting stresses, tests were carried out in which a reinforcement bar was pulled out of a concrete cylinder surrounded by a thin steel tube. The tangential strains in the steel tube were measured, together with the applied load and slip. In five tests, specimens were loaded by monotonically increasing the load, while nine other tests were subjected to reversed cyclic loading. All of the tests resulted in pull-out failures. The results from the monotonic tests indicate that the splitting stresses decreased after the maximum load had been obtained, however not as much as the load decreased. The results from the cyclic tests show a typical response for bond in cyclic loading. When there was almost no bond capacity left the measured strain in the steel tubes stabilised and remained more or less unaffected by the last load cycles. The test results give valuable information about the splitting stresses that result from anchorage of reinforcement bars in concrete. These test results can be useful as a reference when calibrating models of the bond mechanism, and give a better understanding of the bond mechanism.