Performance of round-ended CFST columns under combined actions of eccentric compression and impact loads

Round-ended concrete-filled steel tubular (RECFST) columns are gaining increasing usage in bridge structures. During their service life, RECFST columns under eccentric compression may suffer from impact loading. This study conducted test and numerical investigations to assess the performance of RECFST columns under the coupled actions of compression, bending and lateral impact loads. Fourteen columns were fabricated and tested, considering the influences of axial-load ratio, bending moment and impact energy. The damage mode and the time histories of impact force and displacement were accessed and analyzed. The experimental findings revealed that the initial bending moment negatively affected the impact resistance of RECFSTs. In addition, finite element model was established in ABAQUS and calibrated against the test results. The calibrated model was then employed to conduct the failure mechanism analysis and parametric study. Finally, a single-degree-of-freedom (SDOF) analysis was conducted to predict the mid-height deflection of RECFST columns under combined action of compression, bending and lateral impact loads, by incorporating the influences of pre-axial load and initial bending moment.