Sluice gates are critical infrastructure for flood mitigation. During extreme floods, steel tubes from upstream sites can be transported downstream and impact radial gates, a scenario reported by operators but lacking systematic investigation. This study investigates the dynamic response and damage characteristics of a steel radial gate subjected to such impacts. A finite element model of an in-service radial gate was developed using shell elements. The Johnson–Cook constitutive model was adopted to capture the strain-rate hardening and to quantify the damage extent of Q235 steel. Numerical simulations were conducted across various impact scenarios, comparing the effects of a realistic steel tube against a mass-equivalent spherical impactor, and analyzing the influence of tube size, velocity, angle, and impact location. The results demonstrate that using a mass-equivalent spherical model yields unsafe estimates, underestimating the impact impulse and maximum total displacement by up to 10.58% and 26.16%, respectively, and under-predicting the damage parameter by as much as 51.53% in certain conditions. The maximum gate displacement (885.2 mm) occurs when the tube strikes near the top edge, while the most severe damage (parameter 0.53) is observed near the main crossbeam-support arm joint. The analysis further identifies two primary deformation modes under tube impact: local bending and a cantilever plate deformation. The latter, occurring at top-corner impacts, induces large displacements and forms a plastic hinge line, causing critical damage that is remote from the initial impact point. This research provides quantitative insights that are necessary for the anti-collision design and vulnerability assessment of radial gates. The findings underscore the need to consider realistic impactor geometry in structural analyses, contributing to enhanced risk management and the operational resilience of flood-control infrastructure during extreme flood events.

Modeling complex conditions involving extensive engineering structures with large numbers of beams and columns often requires a mixture of analytical modeling based on beam theory and numerical simulations involving finite element models composed of solid or shell elements. However, high levels of deformation in the planar configuration of cross-sections arising under extreme external loads, such as intensive earthquakes, explosions, and hurricanes, greatly complicates the task of fitting the numerical simulation results to the planar cross-sections required by beam theory. The present work addresses this issue by proposing a fitting method based on a least squares approximation method. The fitting problem is first transformed into a process of solving a cubic equation whose coefficients are integrals over the simulated cross-section. The solution of the cubic equation is defined using explicit formulae developed for calculating the integrals over the surfaces of single solid or shell elements lying within the cross-section by combining the shape functions and degree of freedom results of the elements. The proposed fitting method is then applied for analyzing the blast resistance of steel structures. The potential application of the proposed method is demonstrated by evaluating the rotations, shear deformations, and moment–curvature relationships of the fitted cross-sections.

An efficient CE/SE-based numerical method implemented in LS-DYNA R7.0 has been developed for predicting far-field blast loads from large TNT-equivalent explosives on structures, offering validated accuracy for engineering risk assessment. However, the stability and numerical dissipation characteristics induced by its non-physical parameters (α, β, CFL) remain unquantified, limiting optimal application. To resolve this, we analytically derived an explicit numerical dissipation term coefficient aβΔx(w₊ − w₋)(1 − CFL²)/4 from a simplified 1D continuity equation and established stability criteria via von Neumann analysis. Benchmark simulations of 1 kg TNT free-air bursts demonstrate that increasing α from 0.1 to 5.0 reduces peak overpressure by 13.0%, while β rising from 0.5 to 1.0 decreases it by 1.89%, and elevating CFL from 0.05 to 0.50 increases overpressure by 1.92%. Critically, stability requires α ≥ 0, 0 ≤ β ≤ 1, and 0 ≤ CFL ≤ 1. These first theoretical guidelines for non-physical parameter selection enhance the method’s prediction accuracy and computational efficiency.