查看更多>>摘要：This research examines the applicability of previously developed global and local reduction factors to account for the impact of amplified geometrical imperfections and induced stresses on the buckling resistance of slender steel box section columns. In evaluating the suitability of reclaimed steel structures, conducting a resistance check is critical in determining their reusability. In the buckling resistance check, existing geometric imperfections and residual stresses play a significant role, which could stem from (i) the original manufacturing process and (ii) later deformation during its lifetime. Previous investigations studied the effect of the manufacturing process on buckling resistance but did not consider deformations arising during the lifetime. In the current study, the effect of local and global imperfections stemming from deformations at a later time is investigated. The stresses and deformations arising from applied displacements are incorporated into a subsequent analysis to determine the buckling capacity. Previously developed local and global buckling formulas derived from EN1993-1-5 and EN1993-1-1 are evaluated against GMNI analyses that account for the influence of enlarged imperfections and induced stresses. The calibration process is performed by modifying the imperfection factor alpha in the buckling formulas. Subsequently, the developed formulas are assessed against the interaction buckling resistance of local and global buckling behaviours. This study provides enhanced tools for accurately estimating buckling capacity, particularly in scenarios involving stress formation due to imperfections, thereby improving the accuracy and safety of the application of reclaimed structural members.
Pedrosa, BrunoFarahani, Behzad V.Rebelo, Carlos F. C.Santos, Ruben F....
1.1-1.17页
查看更多>>摘要：The bolt hole detail's fatigue and crack growth behaviour were investigated through experimental testing and numerical approaches. Three fatigue models were used to describe the fatigue behaviour obtained from experimental tests. Fatigue mechanisms were evaluated by considering the impact of hole execution methods, protective coatings, and material type. A characteristic S-N curve was derived, showing that Castillo's model offered the most reliable fatigue life predictions across all stress range levels. Results also demonstrated that the EC3-1-9 design curve provides unsafe predictions at high-stress range levels compared to experimental data. Regarding fatigue crack growth, tests were conducted on specimens with both single and double cracks emerging from the bolt hole. The presence of multiple cracks led to a significant reduction in fatigue life. Beach and striation marks were identified in crack surfaces using optical and scanning electron microscopes. Digital Image Correlation measurements were used to capture strain fields ahead of the crack tip during the crack growth process, confirming distinct displacement patterns depending on the crack configuration. Overall, the findings highlight the critical role of fatigue mechanisms and crack growth assessments on the fatigue strength of bolt hole details. These results contribute to improving the quality of fatigue life predictions and provide valuable insights related to the fatigue crack growth on bolt hole details.
查看更多>>摘要：The optimal design of Kiewit shell structures typically involves two key aspects: grid optimization and section optimization. However, traditional design software primarily designs member sections through finite element analysis and iterative optimization under predetermined grid conditions, making it difficult to achieve a global coupling between the grid form and section configuration. To address this limitation, this paper proposes an integrated design method assisted by deep learning. By setting an overall optimization objective, structural features are automatically extracted from a large database of design schemes, and the optimal grid along with its corresponding member sections is simultaneously selected. Initially, the paper introduces the core concepts of the proposed method, including the multi-feature embedding unit, the embedding encoding principle, and the overall framework of the single-layer spherical lattice shell design model. Subsequently, using an optimal grid selection technique, candidate structures with minimal steel consumption are identified under various design conditions, with spans ranging from 30 to 80 m. To validate the effectiveness of the proposed approach, a comparative analysis with traditional PKPM software is conducted. Experimental results indicate that the deep learning-assisted integrated optimization method not only generates grid forms and section configurations that meet code requirements but also offers significant advantages in reducing steel consumption, enhancing material utilization, and improving design efficiency.
Sun, JiaqiGeng, YueYin, HaitangMoy, Charles K. S....
1.1-1.19页
查看更多>>摘要：Long-span concrete-filled steel tubular (CFST) arches have gained widespread use due to their high strength, excellent seismic resistance, and ease of construction. However, long-span CFST arches are susceptible to out-ofplane buckling problem. In addition, experimental studies on out-of-plane buckling behavior of CFST arches remains limited. In that perspective, this study investigates the buckling behavior of a 9-m span CFST parabolic fixed arch. The arch has a circular cross-section and was subjected to uniformly distributed tilting loads. The effects of the residual stress on the buckling behavior of the composite arches were examined by building finite element models with solid elements. The influence of the confinement effects on the buckling response of the arches was then examined using models with simplified beam elements. It was found that the residual stress had limited effect on the buckling behavior of the arches. The confinement effect had insignificant influence on the buckling behavior of the arches with large slenderness ratios subjected to distributed tilting loads, while it became substantial for arches with low slenderness ratios. The model's accuracy was validated against the experimental data, and the comparative results demonstrated its capability to reliably predict the buckling behavior of CFST arches.
查看更多>>摘要：This paper investigated the seismic behaviour of stainless-clad (SC) bimetallic steel welded T-joints through experimental study and numerical simulation. Seven T-joint specimens were tested, and the influences of the welded section types, welding configurations between the chord and brace, steel grades, and the brace-to-chord width ratios were clarified through comparative research on the test phenomenon, failure modes, hysteretic behaviour, ductility, and energy dissipation. Besides, refined finite element (FE) models were established using simplified modelling approaches. Model verification and parameter analysis were conducted, focusing on parameters such as brace-to-chord width ratio, chord stress ratio, and plate clad ratio. Research showed that all specimens failed through weld fracture between the chord and brace, with only minor deformation observed in the chord walls; the joint moment resistance under cyclic loading ranged from 70 % to 85 % of that under monotonic loading, with corresponding rotation ratios of 0.5-0.6; these T-joints demonstrated excellent ductility and energy dissipation, with ductility indices exceeding 3.0 and energy dissipation coefficients ranging from 20 to 45; the lager brace-to-chord width ratio could result in the larger joint moment resistance and initial stiffness; the welded section types and welding configurations had negligible effects on seismic behaviour. Based on these findings, a restoring force model was developed to accurately represent the moment-rotation behaviour as well as to assist in the design of the SC bimetallic steel welded tubular T-joints.
查看更多>>摘要：In order to solve the issue of ineffective synergetic force transfer between modular columns in existing modular steel building systems, this paper investigates the mechanical properties of an innovative self-locking cooperative modular columns (SLCMC) through eccentric compression experiment. This study analyzes critical mechanical characteristics, including failure modes, ultimate bearing capacity, and strain distribution. The results indicate that under eccentric loading, the self-locking dovetail inter-column connection (SLDICC) significantly improve the bearing capacity, ductility, and stiffness of the modular columns. Additionally, a finite element model of the self-locking cooperative modular column was developed and validated using experimental results. Using this finite element model, further analysis was conducted to explore factors influencing the mechanical performance of the self-locking cooperative modular columns, such as slenderness ratio and the positioning and quantity of SLDICC. The findings show that when the SLDICC are evenly distributed, their effect is maximized, leading to better performance of the modular columns. For a column group made up of four box-section modular columns, the most significant increase in bearing capacity occurs when SLDICC are introduced. However, once synergetic force transmission is achieved, further increasing the number of SLDICC has a diminishing impact on the bearing capacity. As the slenderness ratio of the columns increases, the role of the SLDICC becomes more pronounced, further enhancing the degree of cooperative load-bearing between the columns.
查看更多>>摘要：Serving as an essential step in the design, processing, and forming of the constructional steel in real application scenarios, welding inevitably introduces substantial tensile residual stresses, which compromise fatigue strength, increase the risk of crack initiation and propagation, and jeopardize system safety. The suppression and elimination of welding residual stress in 316 L austenitic stainless steel is one of the key scientific problems that urgently needs to be solved, which can be helpful to expand the practical application of structural steel in new engineering fields such as renewable energy and fusion devices. In this study, the experimental and numerical study on welding residual stresses relief and mechanical properties assessment of 316 L austenitic stainless steel welded joints practically used in the construction of fusion reactor components via layer-by-layer ultrasonic impact treatment was carried out. Effects of surface and layer-by-layer ultrasonic impact treatment (UIT) on the surface residual stress, tensile properties, impact toughness, and microstructures of welded joints made from this specialized fusion reactor material were compared and analyzed. The results revealed that both UIT processes effectively reduced tensile residual stresses in both directions within the impact zone while preserving the fundamental mechanical properties of the welded joints. Furthermore, layer-by-layer UIT demonstrated superior performance compared to surface UIT, achieving residual stress reduction rates of up to 52.31 % for longitudinal stress and 42.62 % for transverse stress, along with the induction of compressive stress in some regions. Additionally, the layer-by-layer UIT refined the grain size within welded joints, which led to the enhancement of the local strength. These findings demonstrate the enhanced effectiveness of layer-by-layer UIT for residual stress management of the 316 L stainless steel, providing physical insights for optimizing welding fabrication processes and improving the reliability of new engineering systems.
查看更多>>摘要：High strength cold-formed steel (CFS) built-up sections have been widely used in the construction sector, mainly due to high load-bearing capacities and flexible cross-section shapes. To further broaden the knowledge and develop efficient design provisions for high strength CFS built-up sections, experiments and numerical simulations were conducted to investigate the local-flexural interactive buckling behaviour and resistances of S700 high strength CFS built-up I-section columns. In the physical experiments, two identical unlipped channel sections were adopted to assemble each built-up I-section in a back-touching configuration with self-tapping screws. Material testing and measurements of initial geometric imperfections were first conducted; nine column specimens of two cross-sections - 90 x 70 x 2.9 and 160 x 100 x 2.9 were employed and then tested under pin-ended boundary conditions. In the numerical simulations, finite element (FE) models were developed and observed to precisely capture experimental observations. A parametric study was then conducted to derive additional numerical data across a wider range of geometric parameters and member slenderness. After that, the effective width method (EWM) in the European code and American specification, and the direct strength method (DSM) in the American specification were assessed, according to the experimental and numerical results, for their applicability to S700 high strength CFS built-up I-section columns failing by minor-axis local-flexural interactive buckling. The assessment results showed that the EWM yielded scattered and conservative results, while the DSM resulted in relatively accurate but still overall conservative resistance predictions. Therefore, a revised AISI design approach was proposed to improve design consistency and accuracy, with its reliability also verified.
查看更多>>摘要：In a Ductile Linked Rocking Frame (DLRF) system, the steel braced frames remain elastic, incorporating Rocking Column Bases (RCBs) with coupon-type fuses at the horizontal rocking interface to facilitate uplift and rocking. This system is further enhanced by Corrugated Steel Panel (CSP) links, which are positioned along the vertical rocking interface. These CSP links act as additional structural fuses, dissipating energy and accommodating relative vertical movements between adjacent steel braced frames. This paper presents a numerical study to examine the seismic response of a typical DLRF and assess the influence of two key design parameters, the SelfCentering ratio (SC) and the Coupling Ratio (CR), on seismic-induced forces and drifts. A total of 40 prototype buildings, including two heights (4-storey and 8-storey) and various configurations of RCBs and CSP links, are analyzed using nonlinear time-history analysis in OpenSees with 22 far-field ground motions. The results indicate that an optimized DLRF configuration, especially with SC values in the range of 0.6 to 0.9 and CR values in the range of 0.5 to 0.6, achieves a uniform inter-storey drift distribution and negligible residual drift, even under Maximum Considered Earthquake (MCE) shaking. Finally, an improved capacity design procedure for DLRFs is proposed, which incorporates both SC and CR to guide engineering design.
查看更多>>摘要：TSZ410 ferritic stainless steel, a novel material with excellent corrosion resistance, high strength, and low cost, enhancing the application and popularization of stainless steel in structural engineering. A high-temperature steady-state tensile test was conducted on TSZ410 ferritic stainless steel, leading to the proposal of a reduction coefficient formula for its high-temperature mechanical properties and the establishment of a stress-strain constitutive model. Finite element models of TSZ410 ferritic stainless steel axial compression members were established to analyze the effects of slenderness ratio, initial imperfection, section size, and section type on their high-temperature ultimate bearing capacity. The results indicate that 300 degrees C marks the critical transition temperature for TSZ410 ferritic stainless steel, beyond which its strength and ultimate load bearing capacity deteriorate at an accelerated rate. Meanwhile, the increase in slenderness ratio results in a continuous decline in the ultimate bearing capacity of TSZ410 ferritic stainless steel axial compression members, with failure modes transitioning from strength failure to overall instability. Finally, based on the EN 1993-1-4, the high-temperature stability coefficient of stainless steel axial compression members was revised. A high-temperature ultimate bearing capacity formula for TSZ410 ferritic stainless steel axial compression members and their critical temperature under different load ratios were proposed, offering a foundation for future standard revisions.
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