Influence of confining hoop flexural stiffness on behavior of high-strength lightweight concrete columns

This paper presents the behavior of high-strength lightweight concrete colu mns confined with small size diameter hoop reinforcement. The concrete had a strength of up to 87.2 MRa (12,500 psi). The experimental program consist ed of axial load tests on eight column specimens. The cross-sectional shape of the column specimens was elliptical, with dimensions of 152 x 229 mm (6 x 9 in.) and height of 762 mm (30 in.). The only longitudinal reinforcemen ts used were four 4.52 mm (0.178 in.) diameter wires that were tack-welded to the lateral reinforcement to maintain the desired configuration of the l ateral reinforcement. The influencing parameters included concrete strength and amount and spacing of lateral reinforcement. Results of this investiga tion were compared with those of similar columns confined with steel reinfo rcement of larger diameter size. The results showed that columns confined with small diameter size for confi ning reinforcement (representing low flexural stiffness) lead to low streng th and low ductility. The compressive strength of confined concrete f(cc)(' ) corresponding strain epsilon (')(cc), and ductility for columns confined with small size diameter were lower than that of larger diameter size, and the differences became considerable for high-strength concrete.