International Journal of Steel Structures最新文献

Semi-rigid connections fundamentally alter the dynamic behavior of steel structures, yet their height-dependent effects remain inadequately quantified in current design practice. This computational study employs nonlinear time-history finite element analysis using the Al-Bermani hysteretic model to systematically investigate dynamic amplification across nine single-bay portal frame configurations (1–25 stories) under harmonic excitation. Three distinct height-dependent behavioral regimes emerge: a growing amplification zone (1–16 stories, displacement amplification factors 0.23–1.87), a saturation zone (8–16 stories, factors 1.75–1.87), and a declining zone (16–25 stories, factors 1.73–1.87). The anomalous 1-story result (R = 0.23) is attributed to resonance detuning: the rigid frame operates at near-resonance with the excitation frequency, and the semi-rigid frequency shift eliminates this condition. Frequency reductions ranging from 25.7 to 49.5% follow a logarithmic relationship (R² = 0.666). The semi-rigid to rigid period ratio increases from 1.34 for a single story to 1.83 for 25 stories, demonstrating strongly nonlinear compounding of flexibility effects with height. Equivalent viscous damping from hysteretic connection behavior decreases from 9.8% (1-story) to 0.033% (25-story). Individual connection rotation demands remain remarkably stable at 19.2–22.8 mrad across all multi-story configurations, indicating that global displacement amplification is driven by accumulation of similar-magnitude rotations across increasing numbers of connections rather than by increasing individual demands. Findings and empirical formulas apply specifically to single-bay portal frames with α ≈ 0.44 and uniform member sizing.

To accurately assess the impact of initial defects in beam-column joints on the seismic performance of structures, this study introduces, for the first time, the initial defect depth (a₀) as a stochastic structural parameter into the seismic fragility assessment framework. Considering the variability of defects across different joints in practical engineering, a simplified approach assuming statistical independence of defect depths among joints is adopted. Firstly, a finite element model of a steel frame incorporating initial cracks at the joints is developed. Subsequently, a systematic parametric analysis is conducted to compare the seismic dynamic responses of the structure under varying initial crack depths. Building upon this, probabilistic seismic demand analysis is performed to establish the relationship between structural responses and ground motion intensity measures for steel frames with cracked joints. Fragility curves corresponding to different initial defect depths are generated, thereby quantifying the significant influence of these initial defects on both the seismic performance and collapse risk of the structure. The findings indicate that the modeling and analysis of steel frames with explicit consideration of initial joint defects enable a more realistic and effective assessment of structural seismic vulnerabilities. The derived fragility curves and parametric analysis results provide a theoretical basis for evaluating the seismic performance of existing structures.

Steel bracing systems help to control the lateral deformations from wind or seismic loads, with gusset plates transferring forces between beams and columns. The commonly used Uniform Force Method (U.F.M.) often overestimates plate size and assumes uniform stress. Using Abaqus finite element analysis validated against experiments, this study shows U.F.M. overlooks framing effects, mis predict force paths, and creates additional bending. Optimizing plate dimensions independently and adding stiffeners at stress concentrations can reduce stress by up to 80% and lower structural weight. Increasing plate thickness improves stiffness, with limited gain beyond 16 mm. These results support more realistic and efficient gusset plate design, with future research needed on nonlinear behavior, dynamic loads, and different bracing systems.

Semi-submersibles are effective for deep-sea oil and gas exploration but face design and operational challenges across varying environmental conditions. The current study examines the response behaviour under a novel passive damper comprising steel vertical struts, stiffeners, elastomer rubber, and rigid steel plates. The damper is affixed to the columns using extended braces. The control mechanism is activated by buoyancy-induced reaction forces at the base plate, with the stiffeners acting as tuned mass dampers, dissipating excessive vibrations. Results of a detailed numerical analysis on different damper configurations show a significant reduction in the heave motion, about 53% with an 8-stiffener damper under low-sea states and 34% under high-sea states. The study helps improve the operational stability of semi-submersibles with cost-effective design solutions.

In the off-site construction of steel composite girder bridges, there is a growing need for non-interference interface connections to address various issues arising from conflicts between prefabricated components. This study examines a connection type for prefabricated steel composite girders that allows for efficient assembly without interference between the prefabricated deck panels and the steel girders. This is achieved by mechanically injecting non-shrink grout through continuous channels. The enhanced workability and flow of non-shrink grout are particularly beneficial for hydraulic injection grouting, enabling faster filling and reducing the risk of voids that could compromise the system's flexural capacity. To evaluate the impact of this connection type and injection grouting on structural performance, a full-scale girder designed according to AASHTO LRFD specifications was tested up to the plastic moment capacity range, demonstrating flexural ductility. Then, based on verified numerical models, a series of finite element analyses were conducted as part of parametric studies to investigate the bending and shear performance of prefabricated composite bridge systems, including variations in the material properties of non-shrink grout for hydraulic injections. The comparative studies revealed that prefabricated steel composite girders with the non-interference interface connection can achieve an equivalent full composite capacity. These findings confirm the applicability of the proposed design procedure for prefabricated steel composite girders in bridge construction.

Welding, a critical technique for joining metals across various industries, introduces residual stresses that significantly affect the mechanical properties and structural performance of welded components. This study investigates the impact of welding-induced residual stresses on the mechanical characteristics and structural behavior of gusset plates used in steel bracing. Finite element analysis (FEA) and sequential (indirect) coupled analysis were employed, with results validated against experimental data. 72 numerical models of gusset plate connections, varying in connection length and plate thickness, were analyzed with and without welding effects. Compared to non-welded conditions, welded gusset plates exhibited an average reduction in ultimate strength and stiffness of 12% and 17%, respectively, highlighting the importance of considering residual stresses in structural design.

Technologies and methods for the assessment and repair of broken cables in cable dome structures are lacking. Therefore, this study developed a method that can be used to assess and repair broken cables in a Geiger-type cable dome structure. Initially, the ANSYS/LS-DYNA software program was used to examine the effects of removing different components on the dynamic response and collapse mode. Based on the change in structural strain energy before and after the removal of component, a component importance coefficient was defined, and the influence patterns of component design parameters and shape design parameters on the component importance coefficient were analyzed. On the basis of the analysis results, evaluation criteria and repair procedures were developed for broken cables. Furthermore, the entire cable repair process was simulated using the dynamic relaxation method. The results revealed that the removal of different components resulted in different dynamic responses and collapse modes. The removal of four key components, namely an outer diagonal cable, an outer ring cable, an inner ring cable, and the upper tension ring, caused strong dynamic responses and resulted in a higher component importance coefficient. The removal of an outer ridge cable (important component) produced a medium dynamic response and a medium component importance coefficient. The removal of the remaining components (general components) resulted in a smaller dynamic responses and a lower component importance coefficient. Component design parameters, such as component cross-sectional size and initial prestress, had a minor impact on the component importance coefficient, whereas shape design parameters, such as the number of trusses in the cable truss and structural topology, had a significant impact on the component importance coefficient, even altering the importance attributes of the components. This study formulated criteria for determining the repairability of broken cables in general and important components. On the basis of the sensitivity of different components to the overall structure after removal, combined with operability and cost-effectiveness, outer diagonal cables were identified as the active tension repair in the proposed repair model. After the repair was completed based on controlling component length and using the dynamic relaxation method, both the internal forces and node coordinates of the structure can revert to their original states prior to cable breakage.

Automating the optimal design of welded plate girders offers significant cost and time savings in structural engineering. This paper introduces a novel framework that combines multi-agent reinforcement learning (MARL) with an inference chain and a shrink refinement procedure to minimize the manufacturing costs of plate girders while adhering to Eurocode constraints. The optimization problem for plate girders is defined using seven discrete design variables and a five-component cost model. A cooperative MARL architecture, known as Comm-DDQN, is trained to sequentially select girder dimensions while ensuring structural feasibility. During inference, a two-stage search process—consisting of beam search followed by stochastic sampling—utilizes the learned policy to efficiently explore high-quality design candidates. A subsequent UF-aware local search (shrink refine) fine-tunes the final design to reduce over-conservatism, pushing the utilization factor (UF) close to 1.0 without violating constraints. We evaluate this approach across 100 diverse load cases and compare it with a Genetic Algorithm (GA) baseline. The proposed MARL method achieves cost outcomes comparable to GA while reducing per-design optimization time considerably. Parametric analysis of the beam search width (W), number of stochastic samples (N), and refinement toggle shows that a broader search and refined approach consistently enhance cost efficiency, reducing average costs by approximately 5–7% and producing designs with UF ≈ 1.0, albeit with a slight increase in inference time. These findings demonstrate that a sequential MARL approach, combined with a beam-stochastic inference chain and refinement, can effectively automate steel girder design, balancing cost efficiency, structural safety, and computational performance. The paper also discusses potential extensions to more complex design scenarios and real-time optimization in design offices.

In this study, a practical approach is developed for a rapid life-cycle cost (LCC) assessment of special moment-resisting steel frames (SMRFs). This approach enables the LCC estimation for SMRFs up to eight stories using only three input parameters: building height, total number of stories, and the response spectrum. The proposed approach first estimates the effective fundamental period of a structure, followed by the estimation of maximum inter-story drift ratios under specified seismic hazard levels. These estimated demands are then integrated into an established probabilistic framework to compute the expected LCC. Results indicate that the proposed regression models effectively capture structural response, yielding average absolute calibration errors of 7.14% and 8.61% for inter-story drift ratios and LCC, respectively. Owing to its simplicity and efficiency, the proposed approach offers strong potential as a practical tool for decision-makers to rapidly estimate the LCC of entire residential zones through discrete evaluation of individual structures, particularly those designed according to modern building codes in seismically active regions.

A new sleeve system is developed to enhance the seismic behavior of steel column base connections under repeated lateral loads. The system uses a custom-shaped steel sleeve installed between the base plate and anchor washer, altering the way loads are transferred at the column base to improve ductility. Various sleeve designs were assessed using a finite element model validated against experimental data. Findings indicate substantial gains in rotational performance and energy absorption while maintaining the original strength of the connection. By acting as a sacrificial component, the sleeve confines damage to a replaceable element, protecting the main structural members during seismic events. This system offers a practical and economical strategy for improving the seismic resilience of steel structures, with clear potential for implementation in earthquake-prone regions.