Mechanical Performance Analysis of Cast-in-Place Shear Wall-Precast Slab Joints Connected by Ultra-High Performance Concrete （UHPC） in Nuclear Powers Plants

Nuclear power plant buildings commonly adopt wall-slab structural systems composed of shear walls and floor slabs， which are typically constructed using the cast-in-place open-top method， resulting in long construction periods. Moreover， wall-slab joints are characterized by large-diameter and densely arranged reinforcement， making it difficult to control the quality of concrete casting. To address these issues， a joint connecting cast-in-place shear walls and precast slabs using ultra-high-performance concrete （UHPC） is proposed. Based on previous seismic tests， a nonlinear finite element model of the joint was established in ABAQUS and validated against experimental results， with bearing capacity discrepancies of less than 5%. A parametric finite element study was then conducted to examine the effects of axial compression ratio （0.1， 0.2， 0.3） and precast slab reinforcement ratio （0.75%， 0.95%， 1.15%） on the failure mode， ultimate bearing capacity， and initial stiffness. All joint models exhibited flexural failure at the slab ends. Increasing the axial compression ratio enhanced the ultimate bearing capacity， while its influence on initial stiffness was negligible （<1%）. When the precast slab reinforcement ratio was 0.95%， increasing the axial compression ratio from 0.1 to 0.2 and 0.3 increased the ultimate bearing capacity by 6.53% and 16.34%， respectively. At an axial compression ratio of 0.2， increasing the precast slab reinforcement ratio from 0.75% to 0.95% and 1.15% increased the ultimate bearing capacity by 5.81% and 15.15%， and the initial stiffness by 2.69% and 5.61%， respectively. Overall， the initial stiffness varied slightly， and the simulated bearing capacity differed from the theoretical values for cast-in-place joints by less than 15%， indicating favorable mechanical properties.