Hysteretic Performance and Bond-Slip Constitutive Model of the Ordinary Rebar with Unbonded Segment

Reinforced concrete structures are widely used, and the contact type between steel and concrete directly affects the mechanical properties of the structure. Setting unbonded segments on ordinary rebars can effectively improve the ductility and energy dissipation capacity of the structure. So, in order to study the hysteretic performance of the ordinary rebar with unbonded segment (OR-US) in detail, this study considered the influence of the unbonded length, rebar diameter, rebar strength, concrete strength, and performed hysteretic tests of five specimens aiming to analyze the damage phenomenon, hysteretic characteristics, ductility and energy dissipation capacity. The results indicated that all the specimens exhibited earlier yielding of bonded rebar at the loading end than the unbonded rebar; the decrease of the unbonded length or the increase of the rebar diameter or the rebar strength all resulted in the delayed yielding of bonded rebar at the loading end; compared to the rebar strength, the increase of rebar diameter led to the later yielding of the OR-US specimen; increasing the unbonded length could improve the ductility and energy dissipation capacity of the specimen; the concrete strength, however, had less impact on the ductility and energy dissipation capacity of the specimen. A bond-slip model for the OR-US was put forward, and the errors between theoretical results and test results were within 10%, indicating the theoretical results were in good agreement with the test results, which provides reference for engineering application of the OR-US.