Cyclic beam bending test for assessment of bond–slip behaviour

Abstract

This paper presents the details of a novel cyclic beam testing method to assess the bond performance of steel bars in reinforced concrete members under reversed cyclic bending actions. The beam specimen originally proposed by RILEM for assessment of bond properties under monotonic flexural loading is modified to sustain displacement reversals without premature buckling of the bar. RILEM suggests a two-point loading (four-point bending) setup for testing beam specimens which would work only under monotonic loading. Hence, a new test setup is designed in such a way that the application of reversed cyclic loading becomes feasible to obtain the cyclic bond–slip relationship. Special attention is paid to ensure the stability of the proposed test setup and to ascertain that no unwanted forces are generated in the system during the course of the test. Performance of the devised cyclic test setup and modified specimen is scrutinised and remedial measures are discussed for the potential issues that may affect the functionality of the proposed testing method. The cyclic bond test results are compared with the results of the most commonly used pullout tests to validate that the bond stress and slip obtained from the proposed test are reliable. Finally, the repeatability of the established testing method is further validated by testing eight beam specimens with varying features subjected to different cyclic loading patterns.