Study on the Axial Tensile Properties of Reinforced Low-Grade Magnesium Ores Concrete-Filled Circular Steel Tubes

In order to study the axial tensile properties of reinforced low-grade magnesium ores concrete-filled circular steel tubes, explore the feasibility of low-grade magnesite concrete as the core concrete of steel tube axial tensile specimens and the influence of longitudinal reinforcement on the axial tensile properties of concrete-filled steel tube specimens, the axial tensile tests and corresponding push-out tests of 8 specimens were carried out with whether reinforcement and concrete type as changing parameters. The results showed that the average strain at each measuring point of the outer wall of the steel tube increased linearly with the increase of axial loads, the maximum strain ratio at the upper, middle and lower measuring points was about 8∶4∶1, and the ultimate interface bond strength of low-grade magnesium ores concrete-filled steel tubes was 0.67-0.73 MPa, which was stronger than that of ordinary concrete(the conclusion only applies to C40 concrete); the specimen was broken at L/3 and L/4 sections, and the section was a horizontal crack; the ultimate bearing capacity of concrete filled with low-grade magnesium ores was about 5% higher than that of ordinary concrete; the inner longitudinal reinforcement could effectively improve the ultimate bearing capacity of the specimen, and the inner longitudinal reinforcement had yielded when the specimen reached the ultimate bearing capacity; finally, based on the calculation formula of axial tensile capacity of concrete-filled circular steel tubes fitted by the research group in the early stage, a new calculation formula of axial tensile capacity of reinforced concrete-filled circular steel tubes related to the ratio of the wall thickness tothe diameter of the steel tube was proposed. The error between calculation results and test data was 2.2%, and the accuracy was high.