Falling debris may initiate or promote the progressive collapse of a structure. To mitigate progressive collapse under falling debris impact, steel frames with five types of beam–column connections were tested. Both single and multiple impacts were applied to each specimen to obtain dynamic responses, load-resisting mechanisms, and impact resistance. The results showed that a typical impact process was divided into three stages. The falling debris impact was mainly resisted by the inertia effect in the initial stage and by deformation in subsequent stages. The majority of the external work applied to the system was absorbed by bending deformation, especially by the plastic rotation at midspan of the beam. All the specimens had the same global deformation shape under the midspan impact scenario. The evolution of catenary action in specimens with different beam–column connections was similar. Catenary action was shown to significantly improve the load-carrying capacity and energy absorption in specimens with high levels of rotational ductility. Greater load-carrying capacity did not offer greater impact resistance. Load-carrying capacity and ductility both played a significant role in the energy absorption capability of the specimens.

In recent years, falling-floor impact scenarios have been studied because they may generate disproportionate collapse. A series of impact tests was carried out at Nanyang Technological University to investigate the dynamic behavior and impact resistance of steel-framed structures. Ten specimens with five types of beam–column connections—i.e., a welded unreinforced flange-bolted web connection (WUF-B), a reduced beam section connection (RBS), a fin-plate connection (FP), a reverse channel connection with flush end plate (RC-FEP), and a reverse channel connection with extended end plate (RC-EEP)—and two typical impact locations—i.e., at midspan for tensile/bending failure, and at beam end for shear failure—were tested under impact loads. Finite-element models were developed and validated against the experimental results. Numerical and experimental results indicated that the numerical model is capable of predicting the dynamic behavior of steel-framed specimens subjected to impact loading in terms of the impact force, displacement, energy absorption, and failure mode. The results showed that all specimens had greater failure displacement under midspan impact. Except Specimen FP, the specimens had greater impact force under beam-end impact. Only Specimen RC-FEP had greater energy absorption under beam-end impact than under midspan impact. Specimen RC-EEP and Specimen FP had the best and worst impact resistance, respectively, which was attributed to the greatest and lowest energy absorption at both impact locations.