Constitutive model of lightweight aggregate concrete confined by circular steel tube

To study the constitutive model of lightweight aggregate concrete (LAC) constrained by the circular steel tube, the monotonic axial loading test was carried out on steel tube confined LAC (STCLAC) stub columns, considering the effects of the diameter-to-thickness (D/t) ratio (30.4, 19 and 12.7) and steel grade (Q235 and Q355). The test results showed that the steel tubes of STCLAC columns were bulging outward as a whole without local buckling during the loading process. The D/t ratio for the STCLAC column is recommended that be greater than 19.0. Due to friction stress accumulating at the interface between the steel tube and the LAC core, the steel tube is subjected to longitudinal stress. When the confinement factor (xi) is less than 2.313, the transverse stress of the steel tube reached its yield strength before the peak load, otherwise it reached the proportional stress without yielding. Using the average transverse stresses along the height of the steel tube, this study calculated the equivalent lateral confining stress of the STCLAC column. The calculation formulas of the compressive stress and corre-sponding strain of confined LAC were proposed based on the test results. And the constitutive model was also proposed, which is more capable of predicting the stress-strain relationship of the constrained LAC by a circular steel tube.

Automated summary

In this study, monotonic axial loading tests were conducted on steel tube confined lightweight aggregate concrete (STCLAC) stub columns to investigate their constitutive model. The effects of diameter-to-thickness (D/t) ratio and steel grade were considered. The results showed bulging outward of steel tubes without local buckling during loading. It is recommended that the D/t ratio for STCLAC columns should be greater than 19.0. The study proposed calculation formulas for the compressive stress and corresponding strain of confined LAC based on test results, and a constitutive model capable of predicting the stress-strain relationship of LAC constrained by a circular steel tube.