Abstract: Dealt with in this paper is the nonlinear dynamic response of reinforced concrete frame structures under symmetrical centralized impacts.In the investigation,first,two influencing factors,namely the initial impact velocity of the drop hammer and the beam-to-column linear stiffness ratio,are analyzed.Next,a nonlinear finite element analysis is performed to explore the variations of the impact force with time,the displacement response of the structure,the final deformation,the characteristics of the plastic deformation and the energy consumption of the structure.Then,the computational results are analyzed and a simplified model to estimate the final deformation of the impact point is put forward.Finally,a comparison is made between the results respectively obtained by the finite- element computation and the simplified model.It is found that ( 1) the influence of initial impact velocity on the structure's dynamic response is more evident than that of the beam-to-column linear stiffness ratio; ( 2) the plastic deformation of the frame structure mainly occurs at the two ends and in the midpoint of the beam,which greatly increases with the increase of the initial impact velocity; and ( 3) the horizontal displacement of the two frame columns is symmetrically outward and the plastic deformation of the column is relatively smaller than that of the beam.

Key words: reinforced concrete frame structure, symmetrical impact, initial impact velocity, linear stiffness ratio, nonlinear dynamic response, finite element analysis