Search Results (3,188)

Plastic forming of the workpiece is a key quality indicator during deforming broaching. This study aims at technological control over workpiece forming by establishing a relationship with technological factors, including broaching modes: interference, tool geometry, and workpiece wall thickness. The research methods used included numerical simulation of the deformation process and the stress–strain state of a plastic steel workpiece. The constructed simulation models allowed tracking stress and strain evolution on the inner and outer surfaces, revealing their differences. The approach’s originality lies in establishing the key influence of critical contact pressure in the deformation zone on strain state changes. Its appearance is influenced by interference, tool geometry, and workpiece wall thickness. Circumferential strain depends solely on interference and workpiece wall thickness, remaining independent of the angle, α. A relationship is provided to determine the interference ensuring the outer dimension. The calculation method for determining the processed hole diameter was improved, considering the real deformation zone scheme, simulation results, and elastic recovery. The relationship between the processed hole diameter, broaching modes, and workpiece wall thickness has been established. It is necessary to set the angle that ensures the absence of axial strain. A technological control scheme for forming is developed, and an application example is provided. Full article

Traditional fixed-tilt photovoltaic (PV) support structures commonly employ inclined beams, double columns, and diagonal braces to resist and transfer horizontal loads. However, this conventional design is characterized by an excessive number of structural components, elevated steel consumption, and suboptimal installation efficiency. To address these limitations, this study proposes a novel unbraced double-column PV support system incorporating hat-shaped inclined beams and T-shaped connectors. The proposed configuration eliminates diagonal bracing while maintaining structural integrity through an efficient load-transfer mechanism, thereby achieving improved standardization, reduced steel consumption, and enhanced constructability. The structural performance of the proposed system was rigorously evaluated through full-scale load-bearing experiments and comprehensive finite element analysis (FEA). The global response, including ultimate load capacity, failure modes, and deformation characteristics, was comprehensively evaluated. The results demonstrate that the proposed system exhibits favorable mechanical behavior and sufficient load-carrying capacity under combined loading conditions. Furthermore, the finite element model was validated against experimental results, showing good agreement in terms of stiffness, deformation patterns, and ultimate response, thereby confirming its reliability for structural analysis. Full article

To investigate the posture control of super-long-span heavy steel box girders during synchronous lifting, this study takes the integral lifting project of the 82 m-span steel box girder of Xiaotun Bridge on the Fuyi Expressway as a case study. A fluid–solid–thermal three-field coupled numerical model was established using Midas NFX 2024 R1 (a general-purpose finite element analysis software for multi-physics and fluid–structure interaction simulations) to explore the alignment and end-displacement characteristics of the steel box girder throughout the lifting process. The results show that under combined thermal and wind loads, girder deflection presents a daily cyclic pattern: temperature rise induces upward arching, while wind-induced vibration generates a mid-span instantaneous amplitude of ±25.0 mm, with a maximum coupled deflection of 31.78 mm. Girder end-displacement increases significantly at lifting heights of 5–25 m and peaks at 25 m. With further height increase and shortened sling length, sway frequency rises while maximum displacement gradually declines. When the plane tilt ratio exceeds 0.17% or the overall unbalanced displacement at lifting points exceeds 12 mm, local stress exceeds 95% of the allowable value, implying potential instability risks. For construction safety, a synchronous intelligent hydraulic lifting system based on the “displacement synchronization and load balancing” strategy was applied. Supported by real-time sensor feedback and adjustment, the system achieves millimeter-level lifting precision and welding positioning accuracy. This study provides a reference for similar synchronous lifting practices of large-span steel box girders. Full article

Construction materials like steel and concrete have been used for thousands of years; however, their industrial-scale production began relatively recently in the 19th century. These materials are still being improved as the drive to build taller buildings, longer bridges, larger dams, and similar engineering marvels keeps pushing boundaries and requirements to previously unimaginable values. Yet, testing and characterization of construction materials that make all that progress possible are overshadowed in scientific literature by more trendy materials such as graphene, composites, nanomaterials, smart materials, and biomaterials. The objective of this review was to identify, collect, and systematically analyze recent papers in which the researchers performed experimental testing on construction materials to document how state-of-the-art experimental practice extends beyond what standardized protocols prescribe. This paper covers Uniaxial Tensile Testing (UT), Compact Tension C(T), Uniaxial Compression (UC), and Single Edge Notched Bending SEN(B), as they are the most commonly used and best-suited techniques for construction material analysis. State-of-the-art papers featuring these techniques were systematically gathered using AI-assisted literature discovery tools, and their contributions beyond ISO and ASTM standards were identified and summarized. Using this review, material scientists and engineers can quickly discover the most influential and relevant papers with the actual experimental data and can apply the testing procedures described in these papers in their laboratories so they can compare their results with the previously published measurements and make an engineering decision based on appropriate comparisons. Full article

Post-rotation jacking is a critical construction stage for load-path reconstruction and alignment adjustment in rotation-constructed bridges, particularly for ultra-wide double-deck composite girder systems. Taking a two-span continuous steel truss–concrete composite girder bridge with spans of 2 × 85 m as the engineering background, this study investigates the mechanical behavior during post-rotation jacking through theoretical derivation, finite element simulation, and on-site monitoring. Based on the force method of structural mechanics, a linear relationship between vertical synchronous jacking force and displacement is derived, and an analytical formulation for bearing reaction redistribution under laterally asynchronous jacking is established by considering the coupling effects of vertical bending, torsion, and transverse multi-bearing support. A full-bridge spatial finite element model was developed in MIDAS Civil NX 2024 V1.1 to analyze the redistribution of bearing reactions and the stress response of the concrete crossbeam under different jacking conditions. The results show that, for the investigated bridge, the jacking force–displacement response remains highly linear during synchronous jacking. The B-axis middle bearing is more sensitive to jacking displacement than the two side bearings, with its fitted stiffness being approximately 2.19 times the average stiffness of the side bearings. Eccentric jacking causes reaction concentration at the jacked point and reaction reduction at adjacent supports, and the magnitude of reaction variation increases approximately linearly with jacking displacement. When the transverse non-uniform jacking magnitude reaches 20 mm, a tensile stress of 0.3 MPa appears at the bottom flange of the concrete crossbeam; therefore, a project-specific stroke-difference limit of 20 mm is recommended for this bridge, while the actual construction achieved a stroke control accuracy of ±0.5 mm and a transverse elevation difference within 1 mm. Field monitoring results validate the proposed analytical and numerical methods. The Pearson correlation coefficients of the measured jacking forces with the finite element and theoretical results are 0.9987 and 0.9988, respectively, and the corresponding mean relative errors are 3.84% and 4.23%. For stress responses, the measured and calculated values show a strong correlation, with a Pearson correlation coefficient of 0.9980 and a mean relative error of 12.77%; the critical mid-span monitoring point shows a relative error of only 0.65%. The final bridge alignment deviation is controlled within ±3 cm. The overall mean verification coefficient is 0.968, with a 95% empirical agreement range of [0.888, 1.048], indicating that the proposed mechanical analysis framework and combined force–displacement control strategy can provide a useful reference for refined construction control of similar ultra-wide double-deck composite girder bridges with comparable span arrangement and transverse bearing layout. Full article

With the advancement of China’s carbon peaking and carbon neutrality targets and the low-carbon upgrading of the construction industry, steel fiber recycled aggregate concrete (SFRAC) has attracted increasing attention as a sustainable construction material due to its advantages in resource recycling and enhanced mechanical performance. However, its compressive strength is influenced by multiple interacting factors, making accurate prediction challenging when using conventional empirical or regression-based methods. To enhance predictive performance, a compressive strength database was established based on published experimental data. The input layer included seven mixture parameters: water content, cement content, fine aggregate content, natural coarse aggregate content, recycled coarse aggregate content, steel fiber content, and superplasticizer dosage, with the 28-day compressive strength serving as the output variable. Using this database, four prediction models were developed, including a back-propagation (BP) neural network and three optimized variants—GA–BP, PSO–BP, and GA–PSO–BP, optimized by genetic algorithm (GA) and particle swarm optimization (PSO)—were developed. Their performance was evaluated using the coefficient of determination (R²), root mean square error (RMSE), and mean absolute error (MAE). Among the four models, GA–PSO–BP produced the best predictive performance, with a best-run R² of 0.9308 on the validation set, exceeding the BP, GA–BP, and PSO–BP neural networks by 0.0642, 0.0326, and 0.0512, respectively. Over 10 independent runs, it attained an average R² of 0.8822 and consistently delivered the lowest RMSE and MAE with small standard deviations, confirming its superior predictive accuracy and stability. These findings suggest that integrating GA and PSO can effectively enhance the predictive accuracy and stability of the BP neural network, thereby providing a dependable reference for compressive strength prediction and mix proportion optimization of steel fiber recycled aggregate concrete. Full article

Conventional formwork systems are limited in their ability to efficiently realize complex and free-form concrete geometries, while additive manufacturing (AM)-based formwork faces constraints in casting-stage structural stability and cost-effectiveness, particularly at construction scale. To address these limitations, a hybrid formwork system integrating a structural steel frame with 3D-printed modules is proposed, in which the steel frame resists casting-induced lateral pressure while the printed components define complex mold geometries. The system was fabricated and validated through a full-scale case study structure measuring 3.0 m × 1.7 m × 2.2 m, produced using a large-scale fused deposition modeling (FDM) process with carbon-fiber-reinforced ABS (ABS-CF20). Geometric accuracy was evaluated by comparing design dimensions with as-built measurements across planar, edge, curved, and inclined regions. Construction efficiency and cost performance were assessed through process-based and cost-based comparisons with conventional steel formwork and fully 3D-printed formwork alternatives. The constructed structure reproduced the intended geometry with an average deviation of approximately 3.2 mm and a maximum deviation within ±4 mm, and no notable formwork deformation or damage was observed during concrete casting. Relative to conventional steel formwork, the hybrid system reduced total fabrication duration by about 50% and fabrication cost by about 60% based on a normalized cost index, while also outperforming fully 3D-printed formwork in cost efficiency by about 45%. The modular configuration and bolted connection system further improved transportability, on-site assembly efficiency, and component reusability. These findings demonstrate that the proposed hybrid formwork system provides a practical and resource-efficient pathway for fabricating complex concrete structures, supporting the broader adoption of digital fabrication in sustainable construction practice. Full article

The article deals with non-destructive methodologies for assessing and preventing corrosion of polymer-coated underground pipelines, advanced corrosion-barrier coating systems based on extruded three-layer high-density polyethylene (3LPE), corrosion control strategies for buried oil, gas, and water transmission infrastructures, and mechanisms and engineering approaches for corrosion prevention and mitigation. The quality assurance of newly polymer-coated underground pipelines, following construction (installation and backfilling), is vital for evaluating the polymer coating quality state and the efficiency of passive anti-corrosion protection, aimed at reducing corrosion risks and prolonging the pipeline’s service life. The evaluation relies on the coating average specific electrical resistance and the presence of coating defects (number, total area, and distribution) of inspected pipeline sections. In this study, based on extensive real data obtained from testing of newly installed underground water and oil/gas pipeline networks (60 projects with a total pipeline length of 260 km) with various technical characteristics, Drainage Test and DCVG (Direct Current Voltage Gradient) complementary non-destructive indirect methods have been investigated to determine the quality level and identify the location and severity of defects in polyolefin (polyethylene) coatings. The novel concepts and criteria were defined: the quantitative criteria for average specific electrical resistance are established; in addition, a new parameter related to the specific coating defects ratio is introduced, which has been shown to correlate with the criteria for the average specific electrical resistance of the polymer coating and consumed electrical current; finally, following DCVG measurements of the 3LPE coating system, a novel degree of relative defect sizes (%IR) for repairs has been suggested. The innovative and comprehensive approach can support the efforts of regulatory quality assurance, design, maintenance, safety, and research communities to ensure the long-term integrity and sustainability of underground polymer-coated steel pipelines. Full article

The contact performance of automotive airbag electrical connectors directly affects the stable conduction of the initiator circuit, yet sufficient failure data are difficult to obtain for such long-life safety-critical components. This study develops a degradation model for connectors with stainless-steel pins, beryllium-bronze sockets, and Ni/Au composite coatings, using the contact resistance increment as the degradation measure. Considering the accumulation of oxidation corrosion products under thermal stress, as well as the local film rupture and re-oxidation induced by fretting wear under combined temperature-vibration stress, a nonlinear time scale t^α is introduced to describe the nonlinear growth of contact resistance. A random-drift nonlinear Wiener process is then constructed: the diffusion term represents local fluctuations within each sample trajectory, while the random drift rate captures growth-rate differences among samples. Parameter estimation was performed using degradation data obtained from 160 °C high-temperature and 160 °C temperature-vibration accelerated degradation tests. The estimation results show that the stress-class-specific time-scale model better reflects the different degradation mechanisms than a common time-scale model, and that the temperature-vibration group exhibits higher resistance growth and stronger trajectory fluctuations. Model diagnostics support the description of the main increment distribution and sample-to-sample differences, while EDS and XPS results provide supplementary evidence for oxidation-related surface composition changes and coating-state evolution. Full article

This study develops collapse fragility curves for a representative steel moment-resisting frame building exposed to idealized tsunami-loading scenarios, explicitly incorporating shoreline distance as an organizing spatial variable. Nonlinear static analyses are performed in SeismoStruct for braced and unbraced configurations, using the maximum interstory drift ratio as the engineering demand parameter. Drift-based damage states are defined according to ASCE 41-23 and FEMA 356 to interpret damage progression, while the probabilistic formulation focuses on the collapse limit state using a lognormal model with total dispersion based on FEMA P695. Triangular and rectangular tsunami-load distributions are considered to assess the influence of load-pattern assumptions. The braced model remains below global collapse within the analyzed intensity range and is retained as a comparative case, whereas the unbraced model reaches global instability and provides the collapse-response information used to construct the fragility curves. The median collapse inundation depth is approximately 14.1 m for the triangular distribution and 11.7 m for the rectangular distribution, corresponding to shoreline distances of approximately 97.5 m and 157.5 m, respectively. The results suggest that shoreline distance can support a spatial interpretation of collapse vulnerability for preliminary coastal-risk assessment, provided that the idealized and site-dependent nature of the adopted distance–depth–velocity scenarios is properly recognized. Full article

Currently, reinforced concrete (RC) columns rely heavily on closely spaced steel ties for confinement and ductility under axial compression. However, tie congestion and construction limitations often reduce confinement efficiency, creating a need for alternative hybrid reinforcement solutions. A series of ten one-third scale circular RC short column specimens of 240 mm diameter and 1.2 m height were fabricated to investigate the effects of different internal confinement configurations. The columns were reinforced longitudinally with six steel rebars of 10 mm diameter (a steel ratio of 1%), and transversely with 6 mm diameter steel ties at varying spacings. All column specimens were cast using 25 MPa concrete, and their cores were internally wrapped with welded wire mesh (WWM) and carbon fiber reinforced polymer (CFRP) strips to enhance their confinement performance. The experimental program focused on evaluating the axial load capacity, axial strain, and ductility. Compared to control RC columns having conventional steel rebar ties, the specimens incorporating hybrid internal confinement of WWM and CFRP exhibited up to 38% and 180% increases in peak loads and ductility, respectively, and failed by buckling of the longitudinal steel bars, followed by rupture of the CFRP strips/WWM layers. These findings suggest that the use of internally wrapped composite systems in RC columns is particularly suitable for applications where dimensional constraints are critical. Additionally, an analytical model was proposed to predict the peak loads of the confined columns. The peak load predictions for various confinement configurations aligned well with the corresponding peak loads measured in experiments. Full article

The development of additive manufacturing in steel construction opens new possibilities for shaping structurally efficient and geometrically differentiated load-bearing systems. At the same time, the viability of such solutions depends strongly on their material rationality, especially at the scale of larger structural typologies. This paper presents a computational comparative screening of spatial steel roof typologies that may be relevant for future large-scale metal additive manufacturing, focusing on how global geometry, support arrangement, curvature, and structural depth influence mass efficiency under a unified structural modelling framework. Using computational modelling and comparative evaluation, the study examines how variations in structural form influence the performance of spatial systems developed within a unified design framework. The analysis demonstrates that the potential for material rationalisation of such structures is not limited to local modification of member dimensions, but is fundamentally linked to the configuration of the overall structural geometry. More than 40 structural configurations were analysed, covering seven typological variants, three rise levels, two support strategies, and two section-sizing approaches. An additional threshold sensitivity check was performed for representative variants to examine whether the main typological ranking remained stable under an alternative four-group utilisation classification. The obtained masses varied by more than one order of magnitude between the most and least favourable configurations, confirming the strong influence of global typology and support arrangement on material demand. The results highlight the importance of structural typology, support arrangement, and geometric organisation in achieving material-efficient solutions. The study therefore argues that, in the context of steel structures considered for future additive manufacturing, global form should be treated as a primary design variable rather than as a secondary outcome of local member sizing. Full article

The article presents the results of experimental studies on the possibility of predicting the efficiency of CO₂ mineralization using metallurgical wastes (MWs) from the perspective of chemical thermodynamics and on identifying, accordingly, promising MWs for the production of construction materials and products. The study examined MWs from major Russian iron and steel producers, namely: blast furnace, electric steelmaking, ferroalloy, converter steelmaking slag, as well as nepheline slag, a by-product of nepheline ore processing for alumina. The CO₂ binding capacity of MWs was determined using experimental samples fabricated by semi-dry pressing of MW powders, followed by curing them in a gas atmosphere with an CO₂ concentration of 80% vol. It was found that the investigated MWs are capable of absorbing and binding CO₂, thereby improving their physical and mechanical properties. Experimental samples made from nepheline slag bind 11.3 to 12.0 wt.% of CO₂; samples from steelmaking slags: up to 9 wt.% or more; and samples from blast furnace dump slag: approximately 5.5 wt.% At the same time, the compressive strength of samples from steelmaking slags exceeds 100 MPa, that of samples from nepheline slag approaches 80 MPa, and that of samples from blast furnace dump slag exceeds 50 MPa. It has been established that predicting the efficiency of CO₂ mineralization by metallurgical wastes based solely on chemical thermodynamics is not entirely accurate. To develop a preliminary forecasting model for the carbonate hardening potential of various MWs, further studies are needed to identify additional key factors influencing the carbonate hardening process of MWs. Full article

This study investigates the durability of timber buildings through a systematic literature review and a service life assessment of two representative building components. The review focused on degradation mechanisms, reasons for demolition, reference service life values, and strategies for extending service life. The deterioration of timber was found to be primarily driven by biological, physical, and mechanical processes, with moisture as a critical factor. Although degradation mechanisms are thoroughly documented, evidence concerning the physical lifespan of timber buildings remains scarce. Most demolitions are due to obsolescence and inadequate maintenance rather than structural failure. Reference service life values are frequently derived from expert judgment and often lack transparent boundary conditions. Nevertheless, factor-based service life prediction models offer a framework for evaluating structural components. When applied to a reference building, the method yielded estimated service lives of 100 years for an interior LVL beech column and 81 years for an exterior wall stud. These findings align with observed lifespans reported in demolition studies. More robust empirical data on demolition ages and refined reference values under standardized conditions are needed. Such improvements would enhance the accuracy of service life prediction models, support more realistic environmental assessments, and strengthen the role of timber as a sustainable construction material. Full article

Stainless steel pipes are critical components in industrial systems such as oil and gas transportation and nuclear power cooling. Surface defects can severely degrade their mechanical performance and operational safety. However, existing inspection methods still face challenges including difficult feature extraction, strong reflection interference, and limited accuracy in small-target detection. To address these issues, this paper proposes an improved detection algorithm termed YOLOv8s-BISW (incorporating BiFPN, SGE attention, and WIoU loss), which introduces multidimensional optimizations based on the YOLOv8s baseline. First, an image enhancement module combining Gamma correction and Contrast Limited Adaptive Histogram Equalization (CLAHE) is designed to mitigate uneven illumination and blurred defect imaging. Second, a Bidirectional Feature Pyramid Network (BiFPN) structure is introduced to strengthen multi-scale feature fusion and improve adaptability to defects of different sizes. Meanwhile, a Spatial Group-wise Enhance (SGE) attention module is embedded into the backbone to enhance defect feature representation while suppressing background interference. Furthermore, the Wise Intersection over Union (WIoU) loss function replaces Complete IoU (CIoU) to improve bounding box regression for irregular defects. Experimental results show that the proposed model achieves an mAP of 0.979 on a self-constructed Stainless-steel Tube Flaw (STF) dataset. Compared with the original YOLOv8s, precision, recall, and mAP are improved by 0.007, 0.010, and 0.033, respectively, while the average detection time per image is only 3.7 ms, achieving a favorable balance between accuracy and real-time performance. Compared with mainstream algorithms such as SSD, YOLOv3, and Faster R-CNN, the proposed method demonstrates superior overall performance, providing reliable technical support for automated surface defect detection of stainless steel pipes and offering practical value for intelligent manufacturing quality control. Full article