Compression behavior of reinforced concrete columns jacketed with multi‐spiral transverse reinforcement

Abstract

AbstractThe objective of this study was to investigate the compressive behavior of reinforced concrete (RC) columns jacketed by modified multi‐spiral transverse reinforcement, in which columns were jacketed by a large welded octagonal stirrup at the center and four small spiral stirrups at the corners of specimens. Sixteen large‐scale concrete columns were jacketed by the proposed method and subjected to axial compression tests. The investigated parameters included the axial compression ratio of existing column and the volumetric ratio of stirrups in jacket. The experimental results revealed that the jacketed columns failed by the formation of an inclined shear failure plane and specimens still kept rather high load‐bearing capacity after core concrete crushed, owing to the multiple confinement materials in jacket. The axial load‐strain curves of specimens could be divided into four phases, corresponding to failure modes. Furthermore, increasing the volumetric ratio of stirrups in jacket effectively improved ductility of jacketed RC columns compared to the load‐bearing capacity, while increasing the axial compression ratio of existing column decreased the enhancement of jacket. Six recent confinement models were selected to predict the peak strength of confined concrete and the corresponding strain. The predicted models performed well in the ascending branch of the analytical stress–strain curves, while the descending branch showed a lower rate of decrease than experimental values. The compression behavior of RC columns jacketed by modified multi‐spiral transverse reinforcement was analyzed, and the effects of axial compression ratios of existing columns and the volumetric ratio of stirrups of jacket on the compression behavior of columns were exhibited. Furthermore, the experimental results were evaluated by six existing models.