Effect of structural features and loading parameters on bond in reinforced concrete under repeated load.

Some reinforced concrete structures are subjected to repeated loads during their service lives, and the effect of repeated loads is stronger and more complex than static loads. This paper reports the results of the tests performed on cylindrical reinforced concrete specimens under uniaxial repeated loads. The effect of structural parameters (e.g., stirrup configuration, bond length, confinement method, and concrete cover) and loading parameters (e.g., amplitude, peak load, loading rate, and initial load cycles) on the bond properties of the reinforced concrete under repeated loads was studied in detail. In addition, the degradation mechanisms and failure modes of the specimens' bond stress were analyzed. It is found that the use of stirrups, increase of bond length, and concrete cover, as well as confinement can effectively curb the widening and expansion of cracks in concrete and significantly improve ductility and repeated load bearing capability. As the rigidity of confinement material increased, the enhancement effect of confinement on bond stress increases. Compared to the role of confinement (e.g., carbon fiber reinforced polymer), increasing the concrete cover can more effectively improve the bond stress. The rebar's subsequent residual bond stress declines as the number of early-stage load cycle increases. [ABSTRACT FROM AUTHOR]