Experimental and analytical investigation on bond-slip behaviour of deformed bars embedded in engineered cementitious composites

This paper investigates the bond-slip behaviour of steel reinforcement embedded in engineered cementitious composites (ECC), a ductile concrete exhibiting tensile strain hardening performance. Two series of experimental tests were carried out on short and long reinforcement subject to pull-out actions. The maximum bond stress that embedded steel reinforcement could sustain was quantified through pull-out tests on short rebars. Experimental results of short reinforcement suggested that ECC significantly increased the maximum bond stress of steel reinforcement. For long reinforcement, special attention was paid to the bond stress of steel segments at post-yield stage. Bond stress profiles were determined in accordance with attached strain gauge measurements along the steel bars. Besides, the effect of localised necking beyond ultimate strength on the force-slip relationships of reinforcement was studied. Thereafter, an analytical model was proposed based on experimental results to predict the force-slip relationship of long reinforcement either anchored in concrete or in ECC. Reasonably good agreement was achieved between experimental and analytical force-slip curves. Finally, parametric studies were conducted to quantify the required embedment length of steel reinforcement in ECC.