Pullout behavior of rebar lap splices in steel-concrete composite structures

Rebar lap splices in steel-concrete composite (SC) structures are popular in joint design for hybrid structures. The local force transfer of such connections has not been investigated further. In this paper, pullout tests were carried out on 61 lap splice specimens to study the bond behavior and the influence of different parameters under wellconfined conditions, with a focus on detailed measurements of localized rebar strains. The failure mode of rebar pullout occurred in specimens with splice lengths smaller than 15 times the rebar diameter. For larger splice lengths, an ideal failure mode of rebar rupture was accomplished. Strain gauges inside the rebars were used to monitor the strain distribution along the rebars. The slip and bond stress could be accordingly derived, indicating the force transfer patterns. Further, the local bond-slip relations and strain penetration effect were clarified for different specimens. The bond-slip stiffness increased and the strain penetration effect decreased with the decrease of the lapped rebar-plate clearance or the increase of concrete strength. For larger rebar diameters, the bond-slip stiffness increased while the strain penetration effect was similar. The simple local bond-slip relations for rebar lap splices in SC structures were deduced for some specified conditions and design recommendations involving splice length, rebar placement, shear studs, and concrete materials were summarized for joint design.