Seismic Safety Assessment of the Gate Hoist Structure in a Roller-Compacted Concrete Gravity Dam

Gate hoist structures are safety-critical appurtenant systems in hydropower projects, yet their seismic behavior has received far less attention than that of dam bodies. This study investigates the seismic performance of a gate hoist structure in a roller-compacted concrete gravity dam using a three-dimensional finite element model of the foundation–dam–gate hoist structure system. Linear-elastic time-history analyses are performed for both unreinforced and brace-reinforced configurations under the design earthquake. Seismic performance is evaluated using principal stress, the point safety factor, the section safety factor, and demand-to-capacity ratio (DCR). The results show that tensile stress is concentrated mainly at beam–column joints in the unreinforced structure, where the maximum principal stress exceeds the concrete tensile strength and local cracking may occur. Brace reinforcement reduces the peak tensile stress and improves the safety level at critical locations, while vulnerable regions may shift to the beam–brace joints rather than being completely eliminated. These findings indicate that the seismic safety of gate hoist structures is better assessed within an integrated dam–structure system, while multi-index evaluation provides a more comprehensive basis for identifying vulnerable regions and assessing reinforcement effectiveness.