Abstract：A series of tests were conducted for concrete-encased concrete-filled steel tubes under
lateral drop hammer impact, and their failure modes, overall and local deformation patterns were
analyzed based on the experimental study. Failure modes of concrete-encased concrete-filled steel
tubes were compared with those of concrete-filled steel tubes and reinforced concrete specimens.
Furthermore, characteristics of time-history curves for impact force, axial force and mid-span
deflection were studied; effects of those parameters, such as impact energy, axial force and
thickness of steel tube, on the mechanical behavior of circular concrete-encased concrete-filled
steel tubes under lateral impact were also investigated. Results indicate that the outer
reinforced concrete component can work coordinately with the inner concrete-filled steel tube
component, and test specimens exhibit good impact resistance performance. Within the experimental
parameter scope, the peak value of impact force, the peak value of mid-span deflection and the
impact duration increase with the increase of impact energy. For specimens with pre-applied axial
load, the peak value of impact force is higher, while the plateau value of impact force is lower.
For specimens with larger thickness of steel tube, both the peak value and the plateau value of
impact force is higher, the peak value of mid-span deflection is lower, and the impact duration is
shorter.
