Numerical simulation analysis of the axial compressive performance of UHPC hoop-restrained reinforced concrete columns

To investigate the axial compressive behavior of reinforced concrete (RC) square columns enhanced with ultra-high-performance concrete (UHPC) under specific conditions, a composite column model comprising "UHPC + steel mesh" was developed using finite element analysis software. This approach distinguishes between confined and unconfined zones within the column. The study examined the effects of UHPC shell thickness, longitudinal bar spacing, and stirrup spacing on the axial compression characteristics, failure mechanisms, and load-bearing capacity of RC square columns. The results indicate that increasing the thickness of the UHPC shell significantly enhances load capacity from 2172 kN to 5132 kN while concurrently reducing ductility. In contrast, reducing stirrup spacing has a minimal effect, yielding an increase in load capacity of only 806 kN. Adjusting the longitudinal rib spacing greatly enhances ductility while concurrently achieving a comparable increase in load capacity, namely by 704 kN. The suggested calculation model for the RC was theoretically validated against the restricted concrete theory and shown strong concordance with experimental data.