An analytical model computing the flexural strength and performance of the concrete columns confined by both transverse reinforcements and steel sections

Abstract

An analytical model was developed that accounted for double confinement provided by both transverse reinforcements and wide flange steel sections in the compression zone. This study also found that the amount of confinements was very sensitive to the post-yield behavior of the composite columns, especially when the buckling in compression region occurred. The nominal moment capacity and post-yield structural behavior of the composite columns were then calculated. The results were verified by comparison to numerical nonlinear finite element analysis results. The model was also verified experimentally. The post-yield behavior of the composite columns obtained from previous experimental studies and nonlinear finite element analysis based on concrete plasticity agreed well with those of the analytical results presented in this study, demonstrating a reliable and fast evaluation of the post-yield behavior of the composite actions. Fracture criteria for the concrete encasing steel columns under axial and lateral loads were also proposed based on the confinement offered by the steel sections encased in concrete. The new concept engaged in the estimation of the flexural strength of concrete columns confined by encased steel sections added innovations to the state of the art in the body of knowledge and advancement of the composite frames.

Part I: failure criteria of the steel-concrete columns (SRC columns) confined by cross-shaped flange sections

“…A substantial discrepancy was demonstrated by the axial load-strain relationship shown in the curve by Legend 8, in which no confining effect by the crossshaped steel section was considered. The equivalent confining factors of 1.2, 1.35, and 1.55 for the confinement provided by the cross-shaped steel section were greater than those obtained for the confinement provided by the H-shaped steel section (1.105, 1.23, and 1.50) (Nguyen and Hong 2020). The fracture criteria with an equivalent confining factor accounting for the confinement provided by the cross-shaped steel section was greater than that based on the confining factor provided by the H-shaped wide flange steel sections.…”

Strength gains of the axially and laterally loaded composite columns based on the concrete confinements provided by steel cores encased in structural concrete

“…The confining effects provided by the cross-shaped steel cores were accounted for by equivalent confining factors of 1.55 (35 mm), 1.35 (75 mm) and 1.2 (140 mm), demonstrating a strong correlation with the results of (Chen and Lin 2006). The equivalent confining factors of 1.11, 1.23, and 1.50 for the confinement provided by the H-shaped steel sections (Nguyen and Hong 2020b) were smaller than those obtained for the confinement provided by the cross-shaped sections (1.2, 1.35, and 1.55).…”