A Study on the Core Confinement Method of Reinforced Concrete Piers

Reinforced concrete bridge columns can be subjected to a series of earthquake excitations as well as axial loads. Transverse reinforcement bars are used in the plastic hinge zone of columns to ensure ductile behavior. Fabrication and placement of those bars in columns is difficult and labor-intensive. Moreover columns with rectangular cross-section require cross-ties and/or overlapping ties in addition to the perimeter ties in order to provide adequate confinement and prevent bar buckling. To solve these problems, the confinement method using interlocking reinforcement is proposed for the transverse confinement of columns of the oblong cross-section. The experimental study for oblong cross-section was carried out by the column test in weak axis and strong axis. The column specimens had 3 types of transverse steel details, such as interlocking spirals(IS), interlocking circular hoop ties(IC), and rectangular ties(RT). The oblong columns with interlocking spirals and with interlocking circular hoop ties showed better seismic performance than the rectangular columns with hoops and cross-ties. Interlocking circular hoop ties, which use the same circular hoop ties as the circular cross-section, considerably reduce the amount of transverse reinforcement than the rectangular ties by about 50%. Connection of rebars can also be simplified. It can be the alternative for oblong section with improved workability and cost-efficiency.