EXPERIMENTAL STUDY ON AXIAL COMPRESSION BEHAVIOR OF CONFINED HIGH-STRENGTH LIGHTWEIGHT AGGREGATE CONCRETE UNDER CONCENTRIC LOADING

In order to investigate the axial compression behavior of confined high-strength lightweight aggregate concrete (HSLAC), an experimental study of twelve HSLAC columns confined by reinforcement under concentric loading were carried out. The failure process, failure mode, stress-strain behavior and strain of lateral ties were studied in the research program. Expected general improvements in strength and ductility of specimens with respect to the effect of key variables such as the tie configuration and transverse reinforcement ratio were reported. And a calculation model of peak stress (f'_cc) and the corresponding strain (ε_cc) suitable for confined HSLAC columns were proposed and compared with Richart model, Mander model, Razvi and Saatcioglu model, and Khaloo and El-Dash model to evaluate the accuracy. It is shown that, after the peak load point, the concrete cover were cut off and sudden spalling occurred as a whole, and a few cracks were found on the internal aggregates as well as the interface between aggregate and mortar, which present significant differences from normal concrete members. However, the development law of stress-strain curves is similar to the normal concrete. The plane of failure presents “H” shape or a diagonal failure at an angle of 45° with the horizontal surface. The results further indicate that the lateral restraint force and confined area of core concrete can be significantly increased by the reasonable selection of tie configuration and adding the amount of lateral ties. It is possible to obtain sufficient strength and ductility behavior in HSLAC columns through proper overlapping hoops with cross ties. The empirical model proposed by combining the stirrup characteristic values (λ_t) and coefficient (k), can accurately and reasonably estimate the peak stress and corresponding strain of confined HSLAC columns.