Infrastructures and key members are potentially exposed to accidental loads due to extreme situations such as collisions, impacts, and terrorist bombings. Consequently, the current design concept requires that the structures or key members possess adequate capacities to resist accidental loads. To understand the mechanical response of concrete-filled steel tube (CFT) beams subjected to impact loads, this paper presents numerical simulations on the CFT beam tests in an instrumented drop-weight impact facility using finite element code LS-DYNA. The adequacy of finite element modeling (FEM) has been validated against drop-hammer impact tests in the literature. Based on the dynamic increase factors (DIFs) derived from FEM, an algorithm based on theoretical sectional analysis (TSA) is introduced to evaluate the dynamic plastic moment capacity of CFT beams. A linear relationship between initial impact energies and absorbed energies by CFT beams is found using either FEM or TSA. To assist engineers in designing simply supported circular CFT beams subjected to lateral impact, an energy design procedure using TSA is proposed, along with the ranges of key parameters, and an example is presented to illustrate the design procedure.