Design optimization and performance evaluation of semi-prefabricated UHPC-RC metro station structures

Aiming to address the limitations associated with conventional cut-and-cover metro stations that utilize cast-in-situ reinforced concrete structures, this study proposes an optimized design method for a semi-prefabricated UHPC-RC metro station structure, which integrates ultra-high performance reinforced concrete (UHPC) as permanent formwork with conventional cast-in-situ reinforced concrete (RC). The optimization scheme and construction method of the semi-prefabricated UHPC-RC metro station are elaborated. Finite element analysis (FEA) was employed to evaluate the stress, damage, and deformation of the longitudinal beams, floor slabs, and sidewalls of the prefabricated UHPC-RC structure under various loading conditions. Furthermore, bending and shear capacity, as well as crack resistance, were verified for the longitudinal beams, slabs, and side walls. The results demonstrate that, compared to conventional cast-in-situ RC metro stations, the proposed semi-prefabricated UHPC-RC metro station features reduced structural dimensions, the thickness of the roof and the middle plate is reduced by 11.8% and 12.5% respectively, the overall project scale is reduced by 1.8%, and the space utilization rate is increased by 0.8%. In the finite element calculation of the design load in the construction stage and operational stage, the UHPC-RC shell structure exhibits minimal plastic damage, and the maximum settlement is 4.62 mm. The main structural components meet the requirements of the specification, and the structural safety reserve is about 1.2 ~ 1.8 times that of the conventional cast-in-situ RC station structure. The proposed semi-prefabricated UHPC-RC metro station offers an innovative and viable solution for metro station construction.