Title: Confinement Effect on Axial Behavior of Lightweight Aggregate Concrete Columns
Author(s): Ju-Hyun Mun, Keun-Hyeok Yang, Myoung-Sung Choi, and Chun-Ho Chang
Publication: Structural Journal
Appears on pages(s): 267-277
Keywords: axial ductility; column; confinement; lightweight aggregate concrete; modification factor; stress-strain relationship
This study aims to examine the axial performance and confinement effect in reinforced concrete columns with different concrete unit weights (ρc). Eleven columns, classified into all-lightweight aggregate concrete (ALWAC), sand-LWAC (SLWAC), and normal-weight concrete (NWC) groups, were tested under concentric axial loads. The existing data compiled from the previous NWC and LWAC column specimens are also used to compare the confinement effect in LWAC columns with those of NWC columns at similar levels of the transverse reinforcement index (ωsh). Test results show that the lateral confining pressure by the transverse reinforcement tends to decrease with the decrease in ρc. Hence, the strength gain factors, strains corresponding to the peak stress of the stress-strain performance, and axial ductility ratio of columns are lower for LWAC columns compared with those for the counterpart NWC columns. The decreasing rates of the axial ductility ratio with the decrease in ρc were more conspicuous in columns with more transverse reinforcement. The increasing rate in the tensile strains of hoops owing to the increase in the applied axial loads is lower for columns with a lower ρc. Hence, modification factors as a function of ρc in the stress-strain model of confined concrete proposed by Razvi and Saatcioglu are introduced herein to account for the reduced confinement effectiveness due to the crack and failure characteristics of LWAC.