This study investigates the behavior of oblong and rectangular bridge columns under combined constant axial loading and lateral cyclic loading. The transverse reinforcement schemes include conventional tie and multi-spiral reinforcement. The multi-spiral reinforcement for the oblong columns comprises two interlocking spirals, or seven interlocking spirals. For rectangular columns, the multi-spiral reinforcement comprises two interlocking large central spirals interlocked with four small spirals at the corners, or comprises seven interlocking large central spirals interlocked with four small spirals at the corners. The amount of transverse reinforcement for all of the columns conforms to the current seismic bridge design specifications. Test results indicate that all of the columns exhibit ductile behavior with ductility capacities significantly higher than the ductility capacity required by the design code. The oblong interlocking spirals column with an amount of transverse reinforcement 43% that of the corresponding tied column shows a similar strength, ductility, energy dissipation, and over-strength to the tied column. Additionally, the rectangular spiral columns with an amount of transverse reinforcement 59% (CM1R1-MS) and 75% (CM2R1-MS) that of the corresponding tied column exhibits a superior strength, ductility, energy dissipation and over-strength to the tied column. Along weak direction tests, the oblong multi-spirals column using H-shape steel shows a significant higher ductility than other corresponding columns using longitudinal reinforcement. With the similar ratio of longitudinal reinforcement, the oblong multi-spiral columns using D36 and D19 longitudinal reinforcement exhibited similar seismic capacities to columns using D25 longitudinal reinforcement. And using H-shape steel and lager diameter of longitudinal reinforcement decreases the over strength.

Moreover, the code P-M interaction analysis method can provide a conservative means of estimating the nominal moment strength. The methods in the current building and bridge seismic design codes to determine the maximum probable moment strengths may not provide conservative estimates. Results of this study demonstrate that the maximum probable moment of the columns examined can be estimated conservatively by 1.4 times the nominal moment strength.

This study investigates the behavior of oblong and rectangular bridge columns under combined constant axial loading and lateral cyclic loading. The transverse reinforcement schemes include conventional tie and multi-spiral reinforcement. The multi-spiral reinforcement for the oblong columns comprises two interlocking spirals, or seven interlocking spirals. For rectangular columns, the multi-spiral reinforcement comprises two interlocking large central spirals interlocked with four small spirals at the corners, or comprises seven interlocking large central spirals interlocked with four small spirals at the corners. The amount of transverse reinforcement for all of the columns conforms to the current seismic bridge design specifications. Test results indicate that all of the columns exhibit ductile behavior with ductility capacities significantly higher than the ductility capacity required by the design code. The oblong interlocking spirals column with an amount of transverse reinforcement 43% that of the corresponding tied column shows a similar strength, ductility, energy dissipation, and over-strength to the tied column. Additionally, the rectangular spiral columns with an amount of transverse reinforcement 59% (CM1R1-MS) and 75% (CM2R1-MS) that of the corresponding tied column exhibits a superior strength, ductility, energy dissipation and over-strength to the tied column. Along weak direction tests, the oblong multi-spirals column using H-shape steel shows a significant higher ductility than other corresponding columns using longitudinal reinforcement. With the similar ratio of longitudinal reinforcement, the oblong multi-spiral columns using D36 and D19 longitudinal reinforcement exhibited similar seismic capacities to columns using D25 longitudinal reinforcement. And using H-shape steel and lager diameter of longitudinal reinforcement decreases the over strength.

Moreover, the code P-M interaction analysis method can provide a conservative means of estimating the nominal moment strength. The methods in the current building and bridge seismic design codes to determine the maximum probable moment strengths may not provide conservative estimates. Results of this study demonstrate that the maximum probable moment of the columns examined can be estimated conservatively by 1.4 times the nominal moment strength.

[1]ACI Committee 318. “Building code requirements for structural concrete and commentary (ACI 318-08)”. American Concrete Institute; 2008.
[2]Caltrans. (2003).Bridge Design Specifications, California Department of Transportation, California, U.S.A.
[3]Correal, J.F., and Saiidi, M.S. (2004). “Seismic Performance of RC Bridge Columns Reinforced with Two Interlocking Spirals”, Report No. CCEER-04-06, University of Nevada, Reno.
[4]FEMA 356 (2000). Prestandard and commentary for the seismic rehabilitation of buildings. Federal Emergency Management Agency, Washington, DC, U.S.A.
[5]MOI. (2011). Design Specifications for Concrete Structures, Ministry of the Interior, Taiwan.
[6]MOTC. (2008). Seismic Bridge Design Specifications, Ministry of Transportation and Communications, Taiwan.
[7]MOTC. (2009). Seismic Bridge Design Specifications, Ministry of Transportation and Communications, Taiwan.
[8]Tanaka, H., and Park, R. (1993). “Seismic Design and Behavior of Reinforced Concrete Columns with Interlocking Spirals,” ACI Structural Journal, 90(2), pp. 192-203.
[9]Yin, S. Y. L., J. C. Wang, and P. H. Wang (2012). ”Development of Multi-Spiral Confinements in Rectangular Columns for Construction Automation,” Journal of the Chinese Institute of Engineers.(In press)
[10] Yin, S. Y.-L., Wu, T.-L. Wu, Liu, T. C., Sheikh, S. A., and Wang, R. (2011). “Interlocking Spiral Confinement for Rectangular Columns,” ACI Concrete International, 33(12), pp.38-45.
[11] Weng, C. C., Yin, Y. L., Wang, J. C, and Liang, C. Y. (2008). “Seismic cyclic loading test of SRC columns confined with 5-spirals”. Sci China Ser E-Tech Sci, 51(5), pp.529-555.
[12] Mander, JB., Priestly, M.J.N.,and Park, R. (1988). “Theoretical stress-strain model for confined concrete”, Journal of struct. Div. ASCE, 114(8), 1804-1826.
[13] Shah, S. P., Fafitis, A. and Arnold, R. (1983). “Cyclic loading of spirally reinforced concrete,” Journal. struct. Div. ASCE, 109(7).
[14] Sheikh, S. A., and Toklucu, M.T. (1993) “Reinforced concrete columns confined by circular spirals and hoops,” ACI struct. J., 90(5), 542-553.
[15] Correal, J. F.; Saiidi, M. S (2007). “Analytical Evaluation of Bridge Columns with Double Interlocking Spirals”, ACI Structural Journal, pp. 314-323.
[16] AISC (2010). Specification for Structural Steel Buildings, American Institute of steel construction, USA.