Assess seismic resilience of unreinforced stone loess cave retrofitted with composite materials by shaking table tests

Unreinforced masonry (URM) structures have consistently suffered significant seismic damage in past earthquake events, leading to considerable losses in both life and property. Unreinforced stone loess cave (URSLC), a type of URM structure, are commonly used in the loess regions of northwestern China due to their affordability for lowincome populations. Developing cost-effective and easily implementable reinforcement technologies to enhance the seismic performance of URSLC is therefore critical. In this study, a series of shake table tests were conducted to improve the strength and ductility of URSLC. Initially, the unreinforced structure was subjected to six progressively intense bidirectional seismic excitations, driving the structure to near-collapse. Subsequently, the damaged structure was retrofitted using composite materials, including steel bar/wire mesh mortar, steel belts, and epoxy resin. To compare the performance, a shaking table test was repeated on the retrofitted structure using the same seismic input as the initial test. Throughout the experiments, the damage progression, crack development, and failure characteristics of both the unreinforced and reinforced specimens were meticulously recorded. Additionally, dynamic properties before and after reinforcement were analyzed to assess the effectiveness of the retrofitting. The results demonstrated that the composite materials provided a strong bond between the stone layers and reinforcement, significantly improving the seismic resistance of the damaged loess caves. Moreover, the use of these materials was found to be both efficient and economical in enhancing the structural performance-particularly in terms of strength, stiffness, and damage tolerance. This study confirms that composite reinforcement can significantly improve the safety of masonry buildings, even under severe seismic loading conditions.