Underground substations are large-span

heavy-load

vertically and horizontally irregular

high-space underground structures with complex stress conditions.They require unique architectural and structural layouts based on the requirements of electrical equipment

auxiliary functional rooms and transportation.This study is based on an investigation into the connection methods of beam-column joint combinations in frame structures of underground substations located in high-intensity seismic regions.The structural system features unequal-height and split-level configurations

with reinforced concrete beams and concrete-filled steel tubular columns

and employs engineered cementitious composite(ECC).The research reveals the effects of several key parameters on the load-bearing capacity

failure modes

energy dissipation capacity

and multi-factor-influenced seismic performance of these beam-column combinations.These parameters include different reinforcement ratios

stirrup ratios

and the presence as well as the distribution length of ECC.The research results can provide a basis for the seismic design of underground substations.