BEHAVIOR OF PRECAST REINFORCED CONCRETE BEAM-COLUMN EXTERNAL CONNECTIONS UNDER CYCLIC LOADING

Abstract

One of the main problems associated with beam-column precast connections is the lack of ductility and low shear strength. The main objective of this paper is to study experimentally the behavior of precast reinforced concrete beam-column external connections under cyclic loading and to improve the performance of shear resistance capacity for this connection type. This experimental study focused on the cyclic behavior of the bolted connection type, which is suitable for low level capacity of shear forces. In the proposed connection system, two factors were studied; firstly, introducing a shear key between column and beam in the connection zone, and secondly, studying the effect of adding shear reinforcement to this zone. Five external beam-column specimens were tested in the experimental program, including one monolithic specimen and four precast bolted connection specimens. Three variables studied in this paper were the effect of shear reinforcement in concrete shear key zone, the length of connection measured from the column face, and the location of threaded bars. All specimens were designed according to the concept of strong column and weak beam, and the specimens scale factor was two-thirds of a prototype structure in geometry according to ACI code. All specimens were loaded on the top of the column by a constant axial compressive load at the beginning of each test, and the reversed cyclic loading in accordance to a pre-described displacement history at the beam tip. The performance of the precast and monolithic connections was evaluated and compared on the basis of flexural strength, ductility, energy dissipation, and lateral drift capacity. The precast connections, with shear reinforcement at the shear key zone, exhibited higher flexural strength and initial stiffness when compared to the similar precast connection without shear reinforcement and the monolithic specimen.