Cyclic behaviour of precast reinforced concrete beam-columns connected with headed bars

Abstract

This paper evaluates the structural behaviour of precast reinforced concrete (RC) beam-columns connected with novel ribbed headed bars, and compares with conventional anchorage system of development length and partial development length. Additionally, the effect of encasement with expa-mesh and varying spacing of lateral ties in precast RC column is also investigated. Precast RC beam-column joints were subjected to the displacement controlled quasi-static reversed cyclic loading on the beam end and constant axial load on the column. Structural behaviour was assessed with regards to damage pattern, cyclic load capacity, stiffness degradation, deformation characteristics and energy dissipation; and performance assessment carried out in accordance with ACI 374.1–05. Most of the specimens experienced crack at the interface of beam-column joint at yield limit. Ultimate failure was beam rebar rupture along with separation of beam and column, thus forming plastic hinge at the joint, rather than in the beam element. Both headed bar and conventional specimens surpassed their nominal moment strength and design shear force, thus exhibiting satisfactory performance. On the other hand, specimens with partial development length attained their nominal moment strength but failed to reach joint shear. The strength parameters of headed bar specimens were well comparable to that of conventionally detailed specimens and satisfied the acceptance criteria of ACI 374.1–05, which can be considered as a benchmark to adopt the proposed ribbed headed bar system of anchorage for precast RC beam-column joints in light of its certain advantages over conventional anchorage system.