Flexural behavior of precast concrete cantilever balconies according to various dry connection details

Precast concrete (PC) is increasingly adopted in alignment with the growing trend toward off-site construction (OSC). In residential buildings, however, PC balconies require temporary supports to stabilize their position during installation. To address this challenge, this study developed innovative PC cantilever balcony systems featuring distinct connection details between the PC balcony and bearing wall structures. An experimental campaign was conducted to evaluate their structural performance. Three test specimens were designed to investigate two primary cantilever connection methods: 1) dry mechanical coupler connection; 2) End plate connections using high-strength bolts. Load-deformation responses including strength, failure modes, crack patterns, and strain behavior were analyzed, where the dry mechanical coupler detail exhibited over twice the deformational capacity compared to end plate connections, and end plate connections experienced premature failure due to local buckling or prying action before PC balcony yielding. Specimen capacities were assessed using current design codes combined with existing models accounting for prying action. All possible failure modes including flexural and shear friction failures, bolt shear, and prying action were considered. The evaluation results showed that the specimen with innovative dry mechanical coupler connection was dominated by flexural failure of PC balcony, while that with high-strength bolt connections with a large unsupported length was dominated by prying out strength. It also appeared that the presented method well captured the failure modes of the specimens, and it also provided accurate structural capacities. On this basis, it can be concluded that when bolt connections with end plates are applied instead of mechanical couplers, it is necessary to prevent local and brittle failure due to prying action in the joint region. To this end, unsupported length between bolts must be sufficiently small, or thick end plate must be used.