Because they have foundations with two or more different elevations, the mechanical performance of structures in mountain cities is significantly different from that of common structures. Our simulation method and the parameters of a typical bolt steel plate-based dry connection joint were verified based on the static load test of a fully assembled substructure against progressive collapse. The load–displacement curves and the displacement–time history curves of the failure point of six kinds of column removal conditions were obtained by using static nonlinear and dynamic nonlinear analysis methods, establishing a different number of dropped stories and spans for the prefabricated step-terrace frame structure models. Based on the ultimate load amplification factor and the maximum dynamic displacement at the failure point, the progressive collapse performance of prefabricated frame structures in mountain cities, including the number of dropped stories and spans, was obtained. The results show that the progressive collapse performance of a prefabricated step-terrace frame structure is inferior to that of a common prefabricated frame structure. The progressive collapse performance is stronger when the upper ground columns fail than that when the dropped ground columns fail. The progressive collapse performance of the prefabricated step-terrace frame structure decreases gradually with the increase in the number of dropped stories and increases gradually with the increase in the number of dropped spans. With the increase in the number of dropped stories, the redundancy of the structure is reduced, and the progressive collapse performance of the dropped stories is reduced by more than that of the upper stories. The increase in the number of dropped spans increases the redundancy of the structure, and the improvement in the progressive collapse performance of the dropped stories is greater than that of the upper stories. This paper provides a reference for the progressive-collapse-resistant design of step-terrace frame structures in mountain cities.
