Experimental investigation of reinforced concrete columns with composite spiral stirrups under eccentric loading
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(1.School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China; 2.Key Lab of Structures Dynamic Behavior and Control (Harbin Institute of Technology), Ministry of Education, Harbin 150090, China; 3.Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters (Harbin Institute of Technology), Ministry of Industry and Information Technology, Harbin 150090, China; 4.61905 Troop of People’s Liberation Army, Shenyang 110005, China)

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TU375.3

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    Abstract:

    The application of composite spiral stirrups confined reinforced concrete columns can improve the core concrete strength and realize high ductility, which can be utilized to design and construct important structures in seismic zones of high intensity. A total of 6 concrete columns confined by composite spiral stirrups were tested under eccentric loading with different stirrup spacing and axial force eccentricities, and the results were compared with other two conventional composite stirrups confined columns under the same condition. The relationships of axial force with lateral deformation, stirrup strain, and compressive strain at the edge of the compression zone were obtained. Failure modes of longitudinal reinforcement yield and concrete crushing of the columns occurred successively under different spacing and eccentricities. Test results indicate that when the spacing is smaller than 80 mm, the composite spiral stirrups confined columns exhibited higher bearing capacity than conventional columns, the strength of the confined concrete is increased, and the defined displacement ductility is improved. Furthermore, the dual-confinement to the concrete consisted of core confinement by spiral stirrups and surrounding confinement by rectangular stirrups had significant effects on failure modes. The failure of the specimen was mainly caused by crushing and spalling of the concrete after buckling of longitudinal reinforcement. It was observed in the tests that the rectangular stirrups continuously provided a superior confinement effect on concrete even after the peak load while the spiral stirrups lost its efficacy. Based on the failure mechanism and the contribution of two different transverse reinforcement, spiral stirrups and rectangular stirrups, a calculation formula for eccentric bearing capacity of composite spiral stirrups confined concrete columns was proposed.

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History
  • Received:December 10,2018
  • Revised:
  • Adopted:
  • Online: December 02,2019
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