Seismic behavior of precast columns with large-spacing and high-strength longitudinal rebars spliced by epoxy mortar-filled threaded couplers

An innovative precast concrete column system, which is expected to be emulative to conventional cast-in-situ columns, is proposed in this paper. In this system, short novel epoxy mortar-filled threaded couplers (MTCs) provide column longitudinal reinforcement with continuity; large-spacing and high-strength longitudinal rebars are used to replace the conventional normal-strength rebars for simplified rebar splices; labor-saving spiral hoops combined with crossties provide core concrete with enhanced confinement. The effectiveness of the innovative construction details was investigated by individual connector tests and column tests. Test results showed that precast columns exhibited global behavior, damage state, cracking distribution, energy-dissipation, and deformation capacity comparable to those of cast-in-situ columns, validating the reliability of the innovative construction details. The short MTCs had little effect on the plastic hinge formation, and could enable precast columns to exhibit stable load-carrying capacity through extensive deformations. Eventually, an approximate method based on a modified plastic hinge length was developed to evaluate the deformation capacity of spliced columns, and the evaluated results agreed well with the measured ultimate drifts.