The buildings may encounter unexpected events such as explosions and impacts, leading to the initial failure of some structural elements, and eventually leading to progressive collapse. The falling-debris-impact scenario is one of the triggers for the progressive collapse of building structures. Therefore, this paper investigated the impact behaviour of three half-scale composite beam subassemblies with different types of connections under the falling-debris-impact scenarios by conducting both experimental tests and finite element analyses. To resist the impact load, structures must exhibit favourable flexural resistance and deformation capacity. The influence of the thickness of concrete in the composite slab, the thickness of profiled steel plate, and the ratio of longitudinal reinforcement on the impact load resistance of the structure are discussed. Parametric analysis indicated that the composite plate can significantly improve the energy absorption capacity. With the increase of the aforementioned parameters, the impact load resistance performance of the structure was significantly improved. The impact resistance of welded unreinforced flange-bolted web (WUF-B) specimens was significantly affected by the thickness of the concrete and the thickness of the profiled steel plate, whereas the ratio of longitudinal reinforcement was the critical factor for the impact resistance of fin plate (FP) and reverse channel connection (RCC) specimens. As the span-to-depth ratio increases, the failure displacement increased while the energy absorption capacity and maximum structural resistance decreased.