EXPERIMENTAL RESEARCH ON BENDING BEHAVIOR OF Q690 HIGH PERFORMANCE STEEL TUBES UNDER CONSTANT AXIAL COMPRESSION

To study the compression-bending stability of Q690 high performance steel tubular in power transfer tower， 15 welded tubular specimens of 3 various cross sections with different slenderness which were designed and fabricated by 6 and 8 mm-thick Q690 high performance steel sheets made in China． The tests of the specimens were conducted under static moment loading with constant axial compression，and moment-axial displacement curves were derived． Based on the test results，the specimensglobal behaviors were analyzed，including the load-carrying capacity，the buckling mode and the failure state，and Chinese specification and American code for design tubular structure in power transfer tower were adopted to verify． The conclusion shows that，buckling types depend on slenderness ratio and the ratio of diameter to thickness，as slenderness ratio decreases or the ratio of diameter to thickness increases，buckling type transfers from global buckling to local buckling; buckling stress states relay on the ratio of diameter to thickness， when the ratio of diameter to thickness decreases，buckling stress state transfers from elasticity to elastoplasticity; all code formulas are conservative，while all analysis results agree well with the test，which further validates that relevant code formulas and stability coefficient are feasible and rational to guide the practice．