High-strength built-up columns in modern structures offer efficiency and load capacity, but axial impact behaviour remains poorly understood currently. A comprehensive numerical investigation was performed using 88 finite element models developed in ABAQUS/Explicit. This study analysed twenty unique cross-sectional designs, two column lengths (420 mm and 800 mm), three hammer velocities (3000, 7000, and 10,000 mm/s), and three hammer weights (224, 424, and 824 kg). The finite element models were tested against previously published experimental results to ensure accuracy in simulating dynamic impact behaviour. Cross-sectional geometry was identified as the principal factor influencing axial impact resistance, with double-web and wide-flange sections demonstrating the greatest capabilities and energy absorption levels. Dimensional scaling markedly improved resistance; however, the column length affected the failure modes, ranging from localised crushing in shorter specimens to a combination of local and global buckling in longer components. The correlation between hammer velocity and mass exhibited nonlinear traits, with peak performance achieved at intermediate velocities and modest masses due to a balance between strain-rate hardening and stability. The recognised failure mechanisms included local buckling, tearing at connection sites, corner cracking, and flexural deformation. The findings provide critical insights into the relationships between geometry, loading circumstances, and failure mechanisms in high-strength built-up columns.
Cable force estimation is critical for ensuring the structural health of cable-stayed bridges. This study assesses the accuracy of three vibration-based models - classical string theory, a least-squares beam formulation, and a two-mode beam combination - using lift-off test results as ground-truth validation. Field measurements were analysed to extract natural frequencies, which served as inputs to predict axial forces. The correlation between estimated forces and lift-off measurements was evaluated using the Pearson coefficient and mean absolute error (MAE). Results show strong agreement between vibration-based estimates and lift-off forces, with correlation coefficients ranging from 0.8610 to 0.8619. Beam-theory approaches outperformed the string model, achieving 7-8% lower MAE confirming that incorporating bending stiffness and multi-mode effects improves accuracy. However, small numerical differences suggest axial tension remains the dominant factor, with flexural rigidity having minor influence on long and slender cables. The near-perfect correlation between the beam-based models (r > 0.9996) highlights their internal consistency. Overall, these findings demonstrate that vibration-based models are reliable tools providing essential insights for structural health monitoring and maintenance strategies.
Design methods for extra-large-diameter welded hollow spherical joints (WHSJs; diameter > 900 mm) are essential for engineering applications. This study presents a parametric analysis of the ultimate axial compressive capacity of such joints, utilising finite element models calibrated against experimental data. The investigation focuses on the effect of sphere diameter, tube diameter, wall thickness, stiffener height, and stiffener thickness, on failure modes and ultimate capacity. The results reveal that the failure mode of extra-large-diameter WHSJs under axial compression is characterised by a circumferential plastic hinge at the tube-sphere junction following substantial plastic deformation. For unstiffened joints, the ultimate capacity is positively correlated with the tube-to-sphere diameter ratio. Increasing the height and thickness of stiffeners significantly enhances the load-bearing capacity of the hollow-sphere wall. To facilitate design optimisation, the joint capacity is decomposed into two components: (1) the enhanced capacity of the stiffeners, and (2) the bearing capacity of the stiffener. Building on this decomposition model, an analytical formula is proposed to evaluate the ultimate compressive capacity of extra-large-diameter WHSJs. The accuracy of this formula is subsequently validated against parametric analysis results.
