ECCENTRIC COMPRESSION TESTS AND CALCULATION METHODS OF RC STUB COLUMNS STRENGTHENED WITH STEEL TUBES

In order to revealed the performances and mechanical mechanism of the RC stub columns strengthened with steel tubes (RCSST) under eccentric compression, a series of tests including ten eccentrically loaded RC stub columns strengthened with steel tubes was conducted. The effects of parameters such as eccentricity along the long and short axis, the core concrete area ratios on the performances were analyzed. The change laws of the experimental phenomena, the failure modes, the ultimate strength, the displacement ductility coefficients and the strength enhancement indexes were respectively studied. Moreover, the mechanical mechanism of the eccentrically loaded RCSST stub columns were revealed through the analysis of the relationships between the vertical force and axial displacement, and the vertical force and strain. The design formulae for predicting the eccentric compressive strength of the RC stub columns strengthened with steel tube was proposed. The experimental results showed that the failure modes of the columns mainly included the local buckling of the steel tube, the fracture of the weld, the crushing of the grouting material and the buckling of the longitudinal rebar. The eccentric compressive strength of the column was enhanced with the decrease of eccentricity and the area ratio of core concrete, and the ductility was significant improved with the increase of eccentricity and the area ratio of core concrete.