Strength of short concrete-filled steel tubes considering a physic-geometrical factor of concrete core under axial compression

Test data have shown that the increase in strength of concrete-filled steel tubular (CFST) columns due to confinement are in variable bigger range than the strength without confinement. Different approaches and design philosophies were adopted in different design codes to account for this increase in strength. The theoretical research herein consider the effect of important physic-geometrical concrete core factors, such as the effect of confining lateral pressure on the concrete core expressed through the coefficient value of lateral confinement, the variable expected direction of failure planes and the enhanced compressive strength of concrete core with different concrete grades. Analytical expression has been proposed to determine the compressive strength of short (CFST) columns taking into account these factors for normal weight concrete core. The results of the analysis and comparison with some design codes indicate that the proposed approach yields satisfactory prediction. Keywords: concrete-filled steel tubular columns; physic-geometrical factor; coefficient lateral confinement; and direction of failure plane