Experimental investigation of reinforced concrete members subjected to reversed cyclic axial loading

Abstract This paper presents an experimental campaign of five reinforced concrete members subjected to cyclic axial loading alternating between tension and compression. Fiber optical sensors and digital image correlation , in combination with automated crack detection and measurement , were used to investigate, among other aspects, the development of crack opening and crack closure, tension stiffening and bond behavior. Bond shear stresses were derived by equilibrium from the steel stress gradient along the reinforcement, requiring accurate knowledge of the cyclic stress–strain relationship of the reinforcement in order to obtain reliable steel stresses from the measured steel strains. To this end, novel customized reversed cyclic material tests were carried out on reinforcing bars short enough to avoid premature buckling. The experimental results show that rather than occurring at a specific load level, crack closure occurs over a loading range in which the cracks close sequentially. Furthermore, the results indicate pronounced tension stiffening when the reinforcement exhibits plastic deformation, and bond shear stress reversal was observed during unloading from tension and reloading in compression. The findings, combined with the open‐access experimental data, are a valuable source for developing and validating mechanical models for reinforced concrete subjected to reversed cyclic loading.