Potential of new innovative confinement for square reinforced concrete columns

The most popular shape of column section used in reinforced concrete buildings is square or rectangle. Besides longitudinal bars, it is normally reinforced with traditional rectilinear or square shape of transverse steel (stirrups) or confinement. It is well known that circular spiral of reinforcing bars used in circular columns serve better ductility or performance compared to rectilinear stirrups in rectangular columns. Up to present, the use of spiral is limited only to circular columns. This is because for rectangular or square columns, it is not easy to shape the spiral on site during construction. The study focuses on the potential application of new innovative rectilinear or square spiral when used for rectangular or square concrete columns. The result of the study is that the proposed new innovative confinement which introduces the use of rectilinear or square spiral without any discontinuity or seismic hooks like those in the stirrups, as well as the introduction of interlocking system has successfully improved the ductility and performance of the columns. With this new innovative confinement, the confined core area is increased, the congestion can be avoided (no seismic hooks), and effectiveness of confining influence is improved (overlapped confining area through interlocking system).