Bond Tests Under High Loading Rates

Abstract

The bond behavior between steel and concrete under high loading rates has been investigated. Different test configurations have been developed and an extensive test program has been performed. The results served as a basis for the development of a model for the bond behavior, where the influence of high strain rates is considered. Similar to the mechanical properties of concrete and steel also their interaction changes with an increase of the loading rate. The low rate dependency of steel compared to concrete with the simultaneous increase of the ultimate bond-stress can lead to a more brittle structural behavior. The knowledge of the rate dependent bond behavior is the condition for the nonlinear analyses of high-dynamic stressed reinforced structural components, if system reserves should be activated by the formation of plastic hinges, a sealing effect against fluids and gases has to be ensured and the crack width or the deformation should be limited. To cover a broad range of loading rates, the experiments have been performed on different test facilities. While the tests with loading velocities up to 1 m/s could be performed on hydraulic systems, for loading rates up to 17 m/s a test configuration with a split-hopkinson-bar has been developed. With this experimental technologies bond tests with slip rates in the range of 9.2·10−6 m/s to 0.9 m/s, respectively bond stress rates from 0.22 MPa/s to 2.1·105 MPa/s have been realized. About 183 Push-In tests with cylindrical test specimens and short bond lengths have been carried out. The concrete compressive strength, the diameter of the specimen, the diameter of the bar, the surface of the reinforcement and the bond length have been varied.