Experimental study of precast columns with a hybrid joint incorporating bolted couplers and grouted sleeves

Abstract

The grouted sleeve (GS) splicing with mature technology is a favored wet-assembled connection in Chinese engineering. A technical interval is normally required to reach the design strength of the grouting material in the in-situ construction of GS splicing, increasing the demands of temporary bracing and reducing the on-site construction efficiency. In this paper, a hybrid joint was proposed by incorporating grouted sleeves and bolted couplers to improve the construction efficiency of GS splicing and reach a comparable performance to the joint with GS splicing. The bolted coupler was labeled CTB coupler, characterized by a combination of threaded connection and bolt fastening. Quasi-static tests were conducted to discuss the seismic performances of four columns, including two precast columns with a hybrid joint (labeled the hybrid column), one precast column using grouted sleeves, and one precast column using CTB couplers. The discussions illustrated that the hybrid column exhibited comparable stiffness degradation and strength to the precast concrete column with the GS splicing, while the former showed a decrease in inelastic deformation capacity and energy dissipated capacity compared to the latter. The energy dissipated capacity of the hybrid column can be improved in two feasible ways: increasing the distance from the hybrid joint to the foundation and using a higher strength rebar for the lower rebar (in the CTB coupler) with respect to its upper rebar. Finally, simplified numerical manners were proposed to consider the effects of CTB couplers and GS splicing. The experimental result of each specimen matched well with its numerical result, validating the effectiveness of the simplified manners.