Experimental study on flexural and seismic performances of RC members with non-rebar-contact ECC joints

Grout-filled sleeves are widely used to splice steel bars for precast structural members, e.g., beams and columns. However, steel bars are generally densely distributed at the splice and steel bar misalignment always exists in actual practice, which bring huge troubles to building workers when splicing steel bars. To address this issue, the authors used Engineering Cementitious Composites (ECC) as the only material to cast connection region, and expected ECC to take the place of the grout-filled sleeve for connecting longitudinal steel bars. For this purpose, the authors experimentally studied the mechanical behaviors of beams with non-rebar-contact ECC joint by four-point bending tests, and raised a special algorithm to determine the appropriate lap length. Based on the proposed algorithm, three columns with designed non-rebar-contact ECC joints were cast and tested under quasi-static cyclic loads. The test results showed that the specimens exhibited increasing flexural strength, energy dissipation and ductility with the increase of non-contact lap length. When the lap length is sufficiently long, the strength of specimens got close or even higher than that of continuous steel-reinforced specimen, however, the corresponding energy dissipation and ductility are, to some extent, less than those of the continuous steel-reinforced specimen. It is verified that well-designed ECC joint may take the place of grout-filled sleeve for connecting longitudinal steel bars and achieve “continuous steel-reinforcement equivalent” effect.