Columns are structural elements that are prone to failure during intense earthquakes. Transverse reinforcement helps to prevent buckling of the longitudinal bars, prevents shear failure, and confines the concrete core. The bars have to be cut, bent and then placed individually on their corresponding position by the workers. All these complex details are sometimes difficult to accomplish on-site and might lead to construction errors. Due to technological advances and the automation of construction processes, some authors have proposed the use of continuous rectangular spirals for transverse reinforcement using machines that can be configured to obtain rebars bent to any desired shape and pitch.
In this study, the use of two continuous rectangular spirals is proposed, one along the corner longitudinal bars, and a second one holding the inner longitudinal bars. The use of two independent spirals may provide more adequate ductility and confinement of the core concrete. Three columns were tested in order to evaluate their seismic performance, comparing the ductility, failure mode, and hysteretic behavior at different drift ratios of the specimens reinforced using spiral transverse reinforcement against a specimen reinforced with conventional ties. The test variables were the transverse reinforcement configuration and the effects of welding the spirals to the longitudinal steel reinforcement.
The results indicate that using continuous transverse reinforcement provides several benefits. The use of rectangular spirals ease the construction process and it demands fewer amounts of steel. Their seismic performance is satisfactory and provides better confinement when an element is subjected to high-axial loading.

ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and
Commentary,” American Concrete Institute, Farmington Hills, MI, 2014.

ACI Committee 374, “Acceptance Criteria for Moment Frames Based on Structural Testing
(ACI 374.1-05) and Commentary,” American Concrete Institute, Farmington Hills, MI, 2005.

Azimi M., Adnan A.B., Tahir M.M., Mohd Sam A.R.B., Sk Abd Razak S.M. “Seismic
performance of ductility classes medium RC beam-column connections with continuous rectangular spiral transverse reinforcements”. Latin American Journal of Solids and Structures, 12, 787-807. (2015).

Campione G., Fossetti M., Minafò G., Papia M. “Influence of steel reinforcements on the
behavior of compressed high strength R.C, circular columns” Engineering Structures, 34, 371-382. (2012).

Chaloris C.E., Karayannis C.G. “Experimental investigation of RC beams with rectangular
spiral reinforcement in torsion”. Engineering Structures, 56, 286-297. (2013).

De Corte W., Boel V. “Effectiveness of spirally shaped stirrups in reinforced concrete beams”.
Engineering Structures, 52, 667-675. (2013).

Eom T-S., Kang S-M., Park H-G., Choi T-W., Jin J-M. “Cyclic loading test for reinforced
concrete columns with continuous rectangular and polygonal hoops”. Engineering Structures, 67, 39-49. (2014).

Eom T-S., Song J-A., Park H-G., Kim H-S., Lee C-M. “Cyclic loading test for beam column
connection with prefabricated reinforcing bar details”. ACI Structural Journal, 110(3), 403-459. (2013).

Essawy A.S., El-Havary M. “Strength and ductility of spirally reinforced rectangular
concrete columns”. Construction and Building Materials, 12(1), 31-37. (1998).

Ghee A.B., Priestley M.J.N., Paulay T. “Seismic shear strength of circular reinforced concrete
columns”. ACI Structural Journal, 86(1), 45-59. (1989).

Hindi R., Turechek W. “Experimental behavior of circular concrete columns under reversed
cyclic loading”. Construction and Building Materials, 22, 684-693. (2008).

Kakaletsis D.J., Karayannis C.G., Panagopoulos G.K. “Effectiveness of rectangular spiral shear
reinforcement on infilled R/C frames under cyclic loading”. Journal of Earthquake Engineering, 15(8), 1178-1193. (2011).
Karayannis C.G., Chalioris C.E. “Shear tests of reinforced concrete beams with continuous
rectangular spiral reinforcement”. Construction and Building Materials. 46, 86-97. (2013).

Karayannis C.G., Sirkelis G.M. “Seismic behavior of reinforced concrete columns with
rectangular spiral shear reinforcement”. Third International Conference on Construction in the 21st Century (CITC-III) “Advancing Engineering, Management, and Technology” 15-17, Athens. (2005).

Lim J-J., Park H-G., Eom T-S. “Cyclic load tests of reinforced concrete columns with high-
strength bundled bars”. ACI Structural Journal, 114(1), 197-207. (2017).

Mander J.B., Priestley M.J.N., Park R. “Theoretical stress-strain model for confined
concrete”. Journal of Structural Engineering, ASCE, 114(8), 1804-1826. (1988).

Moehle JP, Hooper JD, Lubke CD. Seismic design of reinforced concrete special moment
frames: a guide for practicing engineers. NEHRP Seismic Design Technical Brief No 1. Gaithersburg, MD: NEHRP Consultants Joint Venture, a partnership of the Applied Technology Council and the Consortium of Universities for Research in Earthquake Engineering, for the National Institute Standards and Technology: 2008. P. 14-8.

Ozcebe G., Saatcioglu M. “Confinement of concrete columns for seismic loading”. ACI
Structural Journal, 84(4), 308-315. (1987).

Park R., Paulay T. “Reinforced Concrete Structures”. John Wiley & Sons. (1975).

Riva P. “Cyclic response of column-to-foundation joints with continuous stirrups “SPIREX”.
The University of Bergamo. (2009).

Saatcioglu M., Grira M. “Confinement of reinforced concrete columns with welded
reinforcement grids”. ACI Structural Journal, 96(1), 29-39. (1999).

Saatcioglu M., Ozcebe G. “Response of reinforced concrete columns to simulated seismic
loading”. ACI Structural Journal, 86(1), 3-12. (1989).

Saatcioglu M., Razvi S.R. “Strength and ductility of confined concrete”. Journal of Structural
Engineering, ASCE, 118(25), 1590-1607. (1992).

Shahrooz B.M., Forry M.L., Anderson N.S., Bill H.L., Doellman A.M. “Continuous
transverse reinforcement-behavior and design implications”. ACI Structural Journal, 113(5), 1085-1094. (2016).

Shatarat N., Katkhuda H., Abdel-Jaber M., Alqam M. “Experimental investigation of
reinforced concrete beams with spiral reinforcement in shear”. Construction and Building Materials, 125, 585-594. (2016).
Sheik S., Toclucu M. “Reinforced concrete columns confined by circular spirals and hoops”.
ACI Structural Journal, 96(5), 846-857. (1993).

Tanaka H., Park R., McNamee B. “Anchorage of transverse reinforcement in rectangular
reinforced concrete columns in seismic design”. Bulletin of the New Zealand National Society for Earthquake Engineering, 18(2). (1985).

Tanaka H., Park R. “Seismic design and behavior of reinforced concrete columns with
interlocking spirals”. ACI Structural Journal, 90(2). 192-203. (1993).