Search Results (1,771)

Wheeled multifunctional motorized crossing frames represent a new type of crossing equipment for high-voltage transmission line construction. The initial design is too conservative, having a large safety margin and high material redundancy. Therefore, it is necessary to study a lightweight design version. However, as the structure constitutes an assembly consisting of multiple components, it also exhibits relatively high complexity. In a lightweight design, optimizing multi-component and multi-size parameters can lead to structural interference and separation, seriously affecting the smooth progress of design optimization. Therefore, an optimization design method of a multi-parameter complex assembly structure is proposed to solve this problem. Firstly, the typical stress conditions of the wheeled multifunctional motorized crossing frame were analyzed using its structural model. Then, a finite element model of the beam was established in ANSYS 2021 R1 Workbench, and the mechanical characteristics were analyzed. The results show that the arm support is the key load-bearing component and has significant optimization potential. Subsequently, functional mapping relationships were established among the 14 dimension parameters of the arm support, reducing the number of design variables to six and successfully avoiding component separation or interference during optimization. Through global sensitivity analysis, the height, thickness, and length of the arm body were screened out as the core optimization parameters from six initial design variables. Then, 29 groups of sample points were generated via central composite design (CCD), and a response surface model reflecting the relationships among the arm body’s dimensional parameters, total mass, maximum stress, and maximum deformation was established using the Kriging method. Leave-one-out cross-validation (LOOCV) was performed, and the coefficients of determination (R²) for model fitting were all higher than 0.995, indicating extremely high prediction accuracy. Taking mass and deformation minimization as the optimization objectives, the MOGA algorithm was adopted to perform multi-objective optimization and determine the optimal engineering parameters. Simulation verification was conducted on the optimized arm support, and an eigenvalue buckling analysis was performed simultaneously to verify structural stability. Finally, the proposed optimization method was experimentally verified through mechanical performance tests of the full-scale prototype under symmetric and eccentric loads. The results show that the mass of the optimized arm support is reduced from 217.73 kg to 189.8 kg, with a weight reduction rate of 12.8%. Under an eccentric load of 70,000 N, the maximum deformation of the arm support is 8.9763 mm, the maximum equivalent stress is 314.86 MPa, and the buckling load factor is 6.08, all of which meet the requirements for structural stiffness, strength, and buckling stability. The maximum error between the experimental and finite element results is only 4.64%, verifying the accuracy and reliability of the proposed method. The proposed optimization methodology, validated on a wheeled multifunctional motorized crossing frame, serves as a transferable paradigm for the lightweight design of complex assemblies with coupled dimensional constraints, thereby offering a general reference for the structural optimization of multi-component transmission line equipment, construction machinery, and other multi-component engineering systems. Full article

Conventional buckling-restrained braces (BRBs) with rectangular steel tube confinement suffer from stress concentration and inefficient material utilization, limiting their seismic performance. To address these limitations, this study proposes a novel non-rectangular concrete-filled steel tube BRB system incorporating elliptical and corrugated cross-sections. Comprehensive finite element simulations using ABAQUS are conducted to systematically investigate the influence of key geometric parameters—wall thickness (1–14 mm), corner radius (40–55 mm), and corrugation angle (30–75°)—on hysteretic behavior, load-bearing capacity, and failure modes. The results demonstrate that optimized non-rectangular sections achieve load-bearing capacity comparable to conventional rectangular designs (e.g., elliptical section with 12 mm wall thickness reaches 10.02 MN, a 75% increase over 1 mm thickness) while significantly improving material efficiency. Corrugated sections exhibit enhanced weak-axis performance, with equivalent viscous damping ratios exceeding the NIST-recommended threshold of 0.25. Parametric analyses reveal that wall thickness above 12 mm yields diminishing returns; corner radius reduction to 40 mm triggers local buckling yet increases peak capacity; and corrugation angles exceeding 50° induce instability. All non-buckling models satisfy AISC compression strength adjustment factor requirements (β ≤ 1.3). This study systematically evaluates non-rectangular BRB geometries, filling a critical gap in the literature and providing design guidelines that leverage shape optimization to enhance both seismic resilience and material economy. Full article

The steel frame-shear wall composite system has excellent lateral resistance performance in prefabricated steel structure buildings. However, the traditional steel plate concrete shear wall is prone to early buckling of the steel plate and concentrated interface damage under cyclic loading, which limits its energy dissipation capacity. This study presents a steel plate-enhanced reinforced concrete shear wall (SPRCSW) with an internal corrugated steel plate and double-layer steel mesh working together and conducts a selection study based on finite element analysis. Under the same design conditions, the peak bearing capacity in the positive and reverse directions of the SPRCSW is increased by approximately 55.4% and 46.9%, respectively, compared to the ordinary reinforced concrete shear wall, with a ductility coefficient reaching 6.08. The stiffness decline is mild, and the hysteretic curve is complete. Then, this paper forms an SR-SPRCSW composite structural system by combining the new shear wall with a steel frame using semi-rigid joints. Through the comparison of the finite element analysis and low-cycle reverse loading test results of the SR-SPRCSW structure, it is verified that the overall structural system shows good agreement in hysteretic response, skeleton curve characteristics, and failure mode under both research methods, with the peak shear bearing capacity error of less than 1% and the overall bearing capacity deviation controlled within 8%. On this basis, the key parameters of the semi-rigid joints in the SR-SPRCSW structure are analyzed. The results show that the strengthening of the “top and bottom + double web” angle steel joint can raise the peak bearing capacity of the SR-SPRCSW structure by approximately 26.1% and the yield displacement by approximately 29.5%; increasing the strength grade and diameter of high-strength bolts can heighten the initial stiffness and bearing capacity of the overall structure, but ductility slightly decreases; the thickness of the angle steel has a significant impact on the stiffness and deformation capacity of the structure, and a recommended range of values with better comprehensive performance is provided. The findings offer valuable insights for designing seismic-resistant semi-rigid steel frames with steel plate reinforced concrete shear walls and optimizing their parameters. Full article

Low-velocity impacts can cause barely visible impact damage (BVID) in carbon-fiber-reinforced polymer (CFRP) laminates, leading to significant reductions in residual compressive strength. Compression-after-impact (CAI) tests are therefore essential for damage-tolerance design, but existing fixtures often allow global buckling or edge crushing, which can compromise test accuracy. This study experimentally investigates the CAI response of two symmetric angle-ply CFRP laminates with reversed stacking sequences, [0/−45/45/90]s and [90/45/−45/0]s, using a modified CAI fixture. Compared to standard CAI rigs, the modified fixture combines the lateral guidance with anti-buckling plates that clamp the upper and lower specimen edges using a bolt–nut assembly, thereby reducing the active gauge length and stabilizing the panel during compression. Rectangular plate specimens were first impacted at low velocity with a hemispherical projectile; the BVID threshold was defined by a permanent indentation depth of 0.8 mm for [0/−45/45/90]s and 0.7 mm for [90/45/−45/0]s, measured 24 h after impact. Subsequent CAI tests showed about a 22% reduction in maximum compressive load at the BVID level for both layups, while the post-impact compressive stiffness decreased by 17% for [0/−45/45/90]s and 6% for [90/45/−45/0]s. These results demonstrate that reversing the symmetric layup significantly affects stiffness degradation and that the proposed CAI setup suppresses global buckling and edge-dominated failures in all testson the investigated thin CFRP laminates, enabling repeatable residual-strength and stiffness measurements. Full article

Ensuring the crashworthiness of heavy-duty truck cabs is essential for reducing occupant fatalities and improving passive safety in commercial vehicles. Regulatory frameworks such as UNECE Regulation No. 29 (R29) define structural integrity requirements through full-scale destructive impact tests, which are costly and limit iterative design. In this study, an integrated experimental–numerical methodology is presented for the impact assessment of a real Iveco Eurocargo 120E18 truck cab reconstructed using high-resolution 3D scanning. The scanned geometry was used to generate a dimensionally accurate CAD model of the load-bearing cab structure, which was analysed using explicit finite element simulations in ANSYS Academic Mechanical and CFD Teaching package under impact conditions compliant with UNECE R29 and implemented according to the Swedish regulation VVFS 2003:29. In parallel, a full-scale physical pendulum impact test was performed on the same cab using a cylindrical impactor with a diameter of 580 mm, a length of 1800 mm, and a mass of approximately 1000 kg, impacting the upper region of the A-pillar. The experimental setup was instrumented using high-speed optical measurements and an accelerometer to capture impact kinematics and structural response. The numerical predictions showed good agreement with experimental results in terms of acceleration–time histories, absorbed energy evolution, and structural deformation, with differences generally below 6%. Critical regions susceptible to local buckling and plastic collapse were consistently identified in both approaches, while preservation of the driver survival space was confirmed. The results demonstrate that scan-based finite element models, when properly calibrated and validated, can reliably reproduce certification-level impact behaviour. The proposed workflow provides a robust and cost-effective framework for regulatory pre-validation, structural optimisation, and digitalisation of crashworthiness assessment for heavy-duty truck cabs. Full article

To overcome the limitations of conventional steel support systems in large-span concrete dome construction, this study proposes a novel prestressed modular aluminum alloy formwork system based on a radial–circumferential spatial truss configuration. A refined finite element model was established to simulate the staged construction process under the most unfavorable load combination (1.3G + 1.5Q), and the influences of prestress levels and concrete pouring sequences were systematically investigated. Results indicate that external prestressing significantly enhances structural stiffness and deformation control. Increasing the prestress level from 0.3fptk to 0.5fptk reduces the maximum vertical displacement by approximately 18%, while a prestress of 0.7fptk achieves a total reduction of about 31%. Radial support displacement decreases by up to 48%, demonstrating improved global stability. Considering both deformation control and material utilization efficiency, 0.5fptk is recommended as the optimal prestress level. Comparative analysis of construction schemes shows that the layered pouring method reduces maximum vertical displacement by approximately 15% compared with ring casting. Buckling analyses further confirm adequate stability reserve beyond code-required safety coefficients. These findings verify the feasibility and deformation control effectiveness of the proposed prestressed aluminum alloy dome formwork system for large-span construction applications. Full article

The determination of landslide thrust is one of the premises of slope protection. The normative calculation methods of landslide thrust are often difficult to develop because of the structural complexity and paroxysmal instability of rock slopes. In this study, the thin-plate buckling model was adopted to simplify the upper bedding slope rock mass of the protective structure into a rock plate considering transverse shear deformation. The critical load of bedding rock slope instability was selected as the primary indicator for landslide thrust analysis. The double Fourier series was used to solve the mechanical properties of rock plates with simply supported edges under unidirectional and bidirectional pressures, and the critical load expressions of small-deflection buckling of rock plate mechanics were modeled under corresponding conditions and obtained. The relationship and change rules of the dimensionless load coefficient and rock plate geometry size with different cases of thickness is discussed in detail. Finally, the model test and field test were conducted, and the obtained data were used to verify the theoretical results and applied to the landslide thrust calculation and protection structure design of bedding rock slope, providing a theoretical reference for guiding the design of anti-slide piles for slopes and ensuring the stability of slopes. Full article

This study presents a newly conducted comprehensive investigation into the lateral torsional buckling (LTB) behavior of un-bonded pre-stressed (PS) thin-walled steel I-beams subjected to non-uniform bending moments, combining a numerical study with a machine learning (ML) approach and experimental validation. Despite extensive prior work, no exact analytical solution exists particularly for non-uniform bending or can be extremely complicated, as the resulting differential equations contain variable coefficients particularly under non-uniform bending due to the complexity of the PS system. To overcome this limitation, a numerical study using finite element (FE) analysis is first conducted with emphasis on the key geometric and pre-stressing parameters, including unbraced beam length, tendon eccentricity, deviators configurations, and pre-stressing force, to evaluate the LTB behavior. The FE modeling was then validated against experimental testing to ensure the accuracy and reliability of the FE solutions. Subsequently, a comprehensive dataset is generated using FE simulations to train the ML models aimed at predicting the LTB resistance of the PS system. This study presents three ML approaches, including support vector regression (SVR), random forest (RF) and least-square boosting (LSBoost), and their optimal hyperparameters are determined using Bayesian optimization (BO) to enhance the prediction performance. The results indicate that the LTB capacity predicted by the Bayesian-optimized ML models achieve high predictive accuracy and are in close agreement with numerical FE simulations, thereby highlighting their potential in capturing the complex, underlying non-linear interactions influencing the buckling behavior of the PS structural system. Accordingly, the proposed framework offers a robust and effective predictive tool for evaluating LTB resistance, particularly under non-uniform bending where exact analytical solutions are not available, and for supporting the design and assessment of PS steel structures. Full article

A lightweight composite that simultaneously exhibits high strength and excellent thermal insulation is of great interest for thermal protection applications. In this study, dimensionally stable needled quartz fiber felt-reinforced phenolic aerogel composites were prepared using vacuum impregnation, sol–gel, and ambient pressure drying. The composites exhibit a multiscale porous structure formed by interconnected nanometer polymer skeletons and micronscale fibers. By regulating the thermoplastic phenolic resin concentration in the precursor solution, the pore structure of the material was refined; the average particle diameter reduced from 99.76 nm to 38.91 nm, and the average pore diameter decreased from 216.79 nm to 49.53 nm. At a phenolic resin concentration of 25%, the composite exhibits outstanding thermal insulation and mechanical properties: a low thermal conductivity of 0.0646 W·m⁻¹·K⁻¹ at room temperature, with a mere 19.5 °C temperature rise on the sample backside after 1800 s heating at 200 °C, and compressive strengths of 7.70 MPa in the XY-direction and 3.87 MPa in the Z-direction (at 10% strain). X-ray micro-CT characterized the internal structural evolution during loading, revealing a failure mechanism dominated by fiber buckling. Theoretical models and experimental data were used to analyze and quantify the contribution rates of gas and solid heat conduction in NQF/PR aerogel composites, with solid conduction accounting for over 80%. Combined with microstructural evolution, the mechanism for the high thermal insulation efficiency of NQF/PR aerogel composites was elucidated. This study prepared NQF/PR aerogel composites with promising application potential. By systematically evaluating their compressive behavior and quantifying the respective contributions of gas and solid conduction, this work provides a methodological framework to guide the rational design of similar aerogel composites. Full article

The rapid development of multimegawatt wind turbines presents greater demands on the structural safety and stability of tower structures. In response, this study investigates the axial compressive behavior of steel–concrete–steel (SCS) composite towers with a low steel ratio and enhanced shear connection. The two steel plates are integrated by bolt connectors to ensure overall stiffness and effective composite action. Axial compression tests are conducted on curved tower wall members representing a 1/16 segment of the tower cross-section. Previous experimental results indicate that failure is dominated by local buckling of steel plates between adjacent connectors, highlighting the critical role of connector-induced confinement in controlling instability. Numerical models of curved composite walls are established and validated against previously published experimental results, showing good agreement in both failure modes and bearing capacity. Parametric analysis indicates that increasing the bolt diameter from 16 mm to 20 mm and 24 mm enhances the ultimate load by 3.09% and 6.58%, respectively. For the full-section tower model, reducing bolt spacing to 500 mm, 300 mm, and 250 mm increases the ultimate load by 16.33%, 20.05%, and 21.79%, respectively, compared to the bolt-free model. These results confirm that reducing connector spacing substantially enhances bearing capacity through improved confinement and delayed local buckling. A calculation method for evaluating the axial bearing capacity of SCS composite towers incorporating confinement effects is proposed, showing good consistency with both experimental and numerical data. Full article

This paper presents experimental and numerical investigations on thin-walled carbon-epoxy composite structures subjected to axial compression under varying thermal conditions. The primary objective of the study was to determine the influence of temperature on the stability, postbuckling behavior, and load-carrying capacity of the tested profiles. To achieve this, an innovative research methodology combining laboratory experiments and numerical simulations was developed, enabling a comprehensive assessment of the performance of compressed composite structures at different operating temperatures. The obtained results allowed for both qualitative and quantitative evaluation of the temperature-dependent behavior (from −20 °C to +80 °C) of thin-walled composite elements under compressive loading, offering new insights into their structural performance in thermally variable environments. The maximum percentage change in load capacity under variable thermal conditions was approximately 26.5%. At sub-zero temperatures (−20 °C), a slight effect on the load-carrying capacity of composite structures was observed, with a change in stiffness of a few percent. At increased above-zero temperatures (+80 °C), a significant change in stiffness (up to several dozen percent) was observed. The strengths of the work are a relatively extensive experimental program across several temperatures and stacking sequence composites, the use of digital image correlation to capture buckling and postbuckling deformations, and the parallel use of numerical modeling. Full article

The soil–pile–structure interaction (SPSI) has an important effect on the design of earthquake-resistant structures and becomes more complicated for irregular structures constructed on liquefiable soils. Using pile foundations is an efficient method for improving structure stability because they enhance bearing capacity and reduce structural settlement. To assess the effects of SPSI, a 10-story irregular reinforced concrete structure supported by a group of five piles was modeled in PLAXIS2D. To examine the effect of input shaking amplitude on system response, four sinusoidal ground motions with different amplitudes and a real earthquake record were used. The results were assessed, considering the superstructure’s inter-story drift, rotation, and basement settlement. Furthermore, the distributions of curvature and internal forces along the piles were compared in various scenarios. Several failure modes were investigated, including bending, buckling, bending–buckling interaction, shear, and slenderness instability. The results show that internal forces and curvature development in piles are strongly influenced by the shaking amplitude, pile diameter, superstructure load magnitude, and presence of a liquefied layer. These factors also determine the failure mode that is experienced. Full article

With the growing demand for seismic resilience in urban building structures, the development of high-performance energy-dissipation components has become critical for enhancing structural safety and mitigating earthquake-induced damage. Traditional buckling restrained braces (BRBs) are typically designed to remain elastic under frequent earthquakes, limiting their ability to dissipate early seismic energy input. To address this limitation, a novel friction-damped double-stage yield buckling restrained brace (FD-DYBRB) is proposed by integrating friction dampers (FDs) with a conventional BRB. The mechanical performance of both the traditional BRB and the proposed FD-DYBRB was investigated through cyclic loading tests. Additionally, to evaluate the performance differences among various configurations, a cross-shaped double-stage yield BRB was also tested for comparison. The experimental results demonstrate that the proposed FD-DYBRB design is highly effective, exhibiting plump hysteretic curves and distinct double-stage yielding characteristics. Specifically, the FD-DYBRB possesses an initial stiffness ranging from 249.38 kN/mm to 250.31 kN/mm, which is comparable to traditional BRBs. Under small displacements, its equivalent damping ratio increases by approximately 7% for every 50 kN increase in friction force, achieving continuous early-stage energy dissipation. Furthermore, the proposed brace realizes full-process energy dissipation by maintaining stable average tensile and compressive capacities of 87.08 kN and 84.50 kN, respectively, even after the core plate fractures. Compared to the traditional BRB, the maximum dissipated energy of the FD-DYBRB increases by 23.55% to 54.75%, and its maximum equivalent damping ratio exceeds that of the cross-shaped DYBRB by 5%. These findings offer a reliable technical solution for improving the seismic performance of high-rise and long-span buildings, ultimately helping to mitigate structural damage and protect life and property during seismic events. Full article

Piping systems must cope with the internal pressure of the fluid they carry. They are almost always well-designed for withstanding steady-flow pressures, but allowing for unsteady-flow pressures and for fatigue can be more challenging. Positive and negative gauge pressures induced by waterhammer waves are possibly the most extreme that piping is likely to face during its lifetime. It is widely accepted that this should be addressed by analyses during the design phase, but this is usually done under the assumption that consequential (non-hoop) structural movements do not affect the calculated pressures. However, the calculated pressures are used as input to the structural design. Commonly, attention focusses on static predictions of induced hoop stresses and on the risk of buckling, but attention sometimes has to be paid to dynamic responses. In these cases, the complexity of the structural analysis depends on the assumed degrees of freedom of possible movement, so it is desirable to avoid including unnecessary detail. The title of this paper poses one question that is frequently asked. However, the correct answer is not always obtained, partly because highly misleading answers were published in one early paper, the rebuttals to which were much less widely reported. The current contribution attempts to answer the question for both fixed and movable bends. Attention is paid to pressure transients arriving at bends from remote locations and potentially inducing pipe movement. Then, the opposite effect is considered, namely the generation of pressure transients by structural movements. To avoid distorting the picture by combining this with nominally unrelated causes, strong simplifications are made—e.g., disregarding all forms of energy dissipation. Full article

This study presents a mechanics-based comparison of the buckling and ultimate strength behavior of stiffened plates reinforced with bulb-type and built-in angle stiffeners, with particular emphasis on the trade-off between structural performance and weight efficiency. Although these stiffener types are commonly treated as equivalent when designed to provide the same sectional moment of inertia, their nonlinear collapse behavior under realistic loading conditions has not been sufficiently quantified. To address this gap, a two-stage finite element framework is employed, consisting of linear eigenvalue buckling analysis to identify imperfection-sensitive modes, followed by geometrically and materially nonlinear imperfection analysis (GMNIA) to capture post-buckling behavior and ultimate strength. High-fidelity three-dimensional solid models incorporating classification-society-based material properties are used to simulate axially compressed stiffened plates representative of jack-up rig Living Quarter structures. The results demonstrate that, while both stiffener types exhibit comparable elastic buckling resistance, their nonlinear responses differ in terms of stiffness degradation, stress redistribution, and collapse localization. Importantly, the angle stiffener achieves an ultimate strength comparable to that of the elastically equivalent bulb stiffener while requiring less material, thereby exhibiting superior weight efficiency. These findings indicate that elastic equivalence alone is insufficient for optimal stiffener selection and highlight the necessity of nonlinear, imperfection-sensitive assessment in the design of lightweight and high-performance marine structures. Full article