This paper investigates the strength and behaviour of high-strength self-compacting concrete-filled steel tubular (HSSC-CFST) stub columns under axial compression. HSSC-CFST columns are high-performance structural members with wide applications in engineering structures. Nevertheless, relevant studies have commonly focused on the mechanical performance of HSSC-CFST in indoor environments. A finite element (FE) model was developed to predict the axial load capacity of HSSC-CFST stub columns subjected to chloride corrosion. According to this, several crucial geometric and material parameters were designed to investigate the influences on strength, initial stiffness, and ductile performance. Moreover, the analysis on failure mechanisms was investigated by N-ε curves and stress development in the whole loading process. The impacts of key parameters on the reduction factor of axial load capacity were also identified. The numerical analysis results indicate that the axial strength of HSSC-CFST stub columns under chloride corrosion was significantly heightened by increasing the strength of core self-compacting concrete, while contrary results were found with the increase in the steel ratio and yield strength of the steel tube. Lastly, design recommendations for the axially loaded HSSC-CFST were presented by modifying the design codes in CECS104-99. The proposed model is shown to be able to estimate the axial load-bearing capacity of HSSC-CFST stub columns more accurately.

This research examines the effects of vertical jacking construction on the mechanical behavior of shield tunnels. Model tests simulating vertical jacking were performed utilizing a purpose-built apparatus to quantify the reaction forces generated by the diffusion block during the jacking operation. A systematic analysis was conducted on the mechanical responses of shield tunnel lining segments and their interconnecting joints. Utilizing Particle Flow Code (PFC) methodology, a deformation prediction model specifically tailored for vertical jacking conditions was formulated. Correlating simulation results with experimental measurements quantified the sensitivity of tunnel deformation to grouting reinforcement, enabling the identification of an optimal reinforcement zone. Key findings reveal that the jacking reaction force distribution exhibits pronounced nonlinearity: a substantial increase precedes failure, followed by rapid post-failure reduction and eventual stabilization in advanced jacking stages. Tunnel convergence deformation evolves through four distinct phases: significant growth, rapid attenuation, gradual diminution, and final stabilization. The primary zone of influence encompasses the opening ring and its two adjacent rings. Jacking induces longitudinal bending deformation, with maximum joint opening occurring at the opening ring. Abrupt longitudinal load fluctuations cause dislocation between the opening ring and neighboring rings. Internal segment stresses exhibit initial tensile and compressive increases followed by subsequent relaxation. Externally applied grouting reinforcement effectively attenuates jacking-induced tunnel deformation. An optimal reinforcement range was determined at the 60° position relative to the segment springline, substantially lowering resource consumption and construction risks compared to conventional reinforcement strategies. These outcomes furnish theoretical underpinnings and technical benchmarks for optimizing engineering design and facilitating the implementation of vertical jacking technology.