Purpose This paper studies the response of building integrated photovoltaic (BIPV) floor tiles under normal thermo-mechanical conditions and superimposed short-term sustained loads. While the thin glass covers are in general minimally affected by ordinary thermal effects, the typical BIPV section suffers for possible loss of mechanical capacity, due to the sensitivity of the constituent materials, especially the encapsulant. Also, the features of fixing systems have further influence on the mechanical response. Design/methodology/approach 3D numerical models are inspired from real BIPV tiles and used to investigate the coupled thermo-mechanical performance of BIPV tiles under ordinary conditions. The effects of temperature variations are highlighted in terms of deflection, stress and bending stiffness. Findings Key mechanical performance indicators of typical use for laminated glass are critically discussed for the examined BIPV floor tiles. As shown, the serviceability deflection check of BIPV tiles is a key parameter of their performance assessment, which implicitly suffers from the progressive modification of the bending stiffness with increasing temperature. Originality/value Structural glass members are usually designed as load-bearing elements in terms of serviceability deflection and ultimate tensile stress verifications. One of the most influencing parameters in their mechanical analysis is represented by the shear flexibility of the interlayer in use to bond the glass panels. This aspect is even more pronounced for BIPV solutions, where both the glass covers and the encapsulant are subjected to non-uniform temperature scenarios due to ordinary heating, whilst their load-bearing role and mechanical capacity should be in any case preserved. This study shows the key role of thermo-mechanical considerations for similar systems, even under ordinary operational conditions.

Purpose The study aims to propose a new multiaxial fatigue damage parameter. Design/methodology/approach Using the proposed stress analysis method proposed in part 1 and results of the design experimental program, the proposed formula is introduced. Findings The performance of the proposed formula shows encouraging accuracy. This performance is evaluated via the comparison of the proposed formula with other well-known ones. Research limitations/implications The proposed formula requires fatigue input data for non-proportional loadings in the low-cycle regime to predict the fatigue life in that regime. While accessing the available data in high-cycle fatigue is sufficient for life prediction of the non-proportional loadings in the high-cycle regime. Practical implications The paper introduces the concept of the normal-shear stresses interaction in a multiaxial fatigue field. The importance of this phenomenon is evaluated via several available data. Originality/value This paper fulfils an identified need to predict the fatigue life under the proportional and non-proportional multiaxial loadings.

Purpose Aiming at the aging steel water pipelines buried under urban intersections, a predictive reliability assessment framework is proposed by considering the combined effects of internal corrosion and traffic-induced fatigue to provide the decision support for pipeline maintenance and management. Design/methodology/approach The proposed framework evaluates the corrosion effects and then integrates the corrosion and fatigue damage for reliability assessment. The effects of corrosion, considering the material performance deterioration and pipe stress concentration, are first evaluated. A novel strain energy density-based approach is proposed for integrating damage induced by corrosion and fatigue, whereby a new limit state function considering the combined action of corrosion and fatigue is proposed based on strain energy density failure criteria. Finally, reliability assessment has been conducted on the aging water pipelines under urban intersections. A DN500 steel water pipeline buried at an urban intersection is taken as a case study to demonstrate the engineering practicality of the proposed framework. Findings The predicted fatigue life degradation induced by corrosion is consistent with the corresponding fatigue testing results of the corroded specimens in literature, which verifies the effectiveness of the proposed limit state function. And the case study of a DN500 pipeline has demonstrated the feasibility and engineering practicality of the reliability assessment framework. Originality/value This study proposes a novel strain energy density-based approach for integrating corrosion and fatigue effects in pipeline reliability assessment. The limit state function considering the combined effects of fatigue loading and corrosion is then developed based on the approach.

Purpose Mechanical meta-materials have aroused great interest during the past few decades. Unique or even unprecedented mechanical behaviors and functionalities have been created through the rational design of the micro-structure of mechanical meta-materials. Moreover, the development of additive manufacturing (AM) techniques further promotes their applications in various fields like aerospace, automobile, tissue engineering, etc. In recent years, mechanical meta-materials have also been applied to the design of aeroengine structures due to their superior performance and lightweight features. This paper aims to give a comprehensive review of the design of mechanical meta-materials and show their recent applications to aeroengine structures. Design/methodology/approach This paper presents a state-of-the-art review on the design of mechanical meta-materials and their applications to the rotating and stationary components in aeroengine structures. Findings Mechanical meta-materials are categorized into two kinds, including homogeneously architected meta-materials that have one unique unit cell periodically arranged to fill the space and heterogeneously architected meta-materials that may integrate different unit cell designs or introduce gradient changes to the whole structure. A promising design strategy, i.e. “the right micro-structure deployed to the right position,” is proposed for heterogeneous meta-materials, and it is concluded that the design methods for mechanical meta-materials are moving from simple cell design to the direction of customized and optimized design enabled by artificial intelligence. Besides, the integration of metal AM and mechanical meta-materials paved a novel path for the design of lightweight high-performance engine structures. Originality/value The present paper systematically reviews the design of mechanical meta-materials, and for the first time summarizes the application of mechanical meta-materials to aeroengine structures.

Purpose This study proposes a UHPC-NC composite beam system to address deformation incompatibility issues caused by significant elastic modulus mismatch in conventional steel-NC composite beams. To further reduce the construction cost of UHPC-NC composite beams, an optimal cross-section design method based on an improved genetic algorithm is introduced. Design/methodology/approach Taking a 16 m simply supported T-beam as the engineering case study, a preliminary UHPC-NC composite beam cross-section is designed. With material cost minimization as the objective function and cross-sectional parameters as variables, an optimization model incorporating bearing capacity and deformation constraints is established. An enhanced adaptive genetic algorithm is employed, wherein crossover and mutation probabilities are dynamically adjusted to substantially improve global optimization performance and convergence efficiency. The mechanical performance and practical behavior of the optimized composite beam are validated through a 1:2 scaled four-point bending test. Findings The optimized UHPC-NC composite beam achieves a 21.91% reduction in total life-cycle cost, significantly improving economic feasibility. Test results indicate that the composite beam undergoes a sequence of four characteristic phases: elastic phase, crack propagation, fiber reinforcement and ultimate failure. The measured strain profiles are consistent with the hypothesis that cross-sections remain plane under loading. For the composite beam, the measured flexural capacity is 21.8% greater than the specified design value. When loaded to the serviceability stage, the maximum crack opening is under 50 micrometers. The deflection remains limited to less than l/600. Originality/value The optimized design achieves a balance among lightweight construction, high load-bearing capacity and low maintenance requirements, providing theoretical foundations and practical references for the broader engineering application of UHPC-NC composite structures.

Purpose The development of additive manufacturing (AM) techniques has significantly expanded the design space for engineering structures and facilitated the practical application of novel concepts, such as meta-materials with diverse microstructures. However, in load-bearing applications—particularly in aerospace and aeroengine fields—additively manufactured (AMed) metallic materials and structures still face limitations due to the presence of inherent defects. For meta-materials, the geometric accuracy of microstructural cells is also difficult to ensure using current metal AM technologies. These defects and geometric inaccuracies can markedly affect the mechanical properties of mechanical meta-materials. Consequently, a substantial body of research has focused on investigating the mechanical behavior and performance of AMed mechanical meta-materials. This paper presents a comprehensive review of recent advancements in metal AM technologies, with a particular focus on defect characterization methods and the evaluation of strength and fatigue properties in AMed mechanical meta-materials. Design/methodology/approach This paper provides a state-of-the-art review on the AM techniques for mechanical meta-materials, defects and defect characterization methods in AMed structures, and evaluation methods of strength and fatigue properties of mechanical meta-materials. Findings Metal AM techniques for mechanical meta-materials, like selective laser melting, wire-arc AM, etc, and recently developed technologies like, online inspection during the AM process, are reviewed. The defects in AMed meta-materials, along with the corresponding characterization methods, are systematically summarized. Additionally, this paper presents a comprehensive overview of evaluation approaches for the strength and fatigue properties of mechanical meta-materials, encompassing experimental testing, theoretical modeling, numerical simulation, and machine learning techniques. Future perspectives on manufacturing and the mechanical property study of mechanical meta-materials are also given. Originality/value A systematic summary of metal AM techniques, as well as defect detection and characterization methods in AMed mechanical meta-materials, is provided. Furthermore, the paper presents a comprehensive review of the mechanical properties of mechanical meta-materials, with a particular focus on strength and fatigue performance.

PurposeThis study aims to accurately assess the long-term service performance of welded high-speed train carbodies by predicting their crack-growth life.Design/methodology/approachFirst, the Christopher-James-Patterson (CJP) crack tip field model was applied to analyze the crack growth rate of the welded aluminum alloy in a high-speed train carbody. Next, a high-precision surrogate model, developed by the research team, correlates multiaxial loads and stresses to transform load-time histories into dynamic structural stresses at critical points. These dynamic stresses were then corrected using the mesh-insensitive structural stress method to improve the accuracy of crack growth life predictions.FindingsThe results demonstrate that the proposed fatigue residual life prediction framework, integrating structural stress analysis with the CJP model, is mesh-insensitive and eliminates subjectivity in selecting the primary S-N curve method. This framework improves the reliability of predictions and provides valuable insights for determining overhaul cycles and implementing intelligent maintenance strategies for large welded structures.Originality/valueThis study presents a novel approach that combines the CJP model with structural stress analysis to predict the fatigue crack growth life of high-speed train carbodies. The proposed method overcomes limitations of traditional methods and offers more accurate and robust predictions, contributing to the field of fatigue durability assessment of welded structures.

PurposeThis paper aims to update the finite element model of a pre-stressed concrete continuous girder bridge using a back propagation neural network optimized by the improved mind evolutionary algorithm (IMEA).Design/methodology/approachIn this paper, we introduce particle swarm optimization in the convergence process of the mind evolutionary algorithm (MEA) and then dynamically adjust the inertia weights in the moving speed of the particle swarm through a nonlinear decreasing strategy, which is used to solve the drawback of the algorithm’s arbitrarily initialized population. Finally, the measured natural frequency of the Yunliang River Bridge is used as the input parameter, and the design parameters are obtained by updating in stages (pile foundation stage and bridge completion stage).FindingsThe relative error of the natural frequencies of the continuous girder bridge is significantly reduced from more than 7% before updating to less than 3%. Compared with the 2.31% average relative error of the natural frequency of the continuous beam bridge updated by the MEA-BP neural network, the error of the natural frequency after the update of the IMEA-BP neural network model is only 1.01%. The IMEA-BP neural network demonstrates stronger applicability and higher update precision. Compared to the bridge finite element models without phased updating, the phased updating presents a better performance.Originality/valueThis study provides an accurate and effective method of updating finite element models for continuous girder bridges, as well as a valuable reference for updating finite element models for other types of bridges.

PurposeDamage of engineering structures is a nonlinear evolutionary process that spans across both material and structural levels, from mesoscale to macroscale. This paper aims to provide a comprehensive review of damage analysis methods at both the material and structural levels.Design/methodology/approachThis study provides an overview of multiscale damage analysis of engineering structures, including its definition and significance. Current status of damage analysis at both material and structural levels is investigated, by reviewing damage models and prediction methods from single-scale to multiscale perspectives. The discussion of prediction methods includes both model-based simulation approaches and data-driven techniques, emphasizing their roles and applications. Finally, summarize the main findings and discuss potential future research directions in this field.FindingsIn the material level, damage research primarily focuses on the degradation of material properties at the macroscale using continuum damage mechanics (CDM). In contrast, at the mesoscale, damage research involves analyzing material behavior in the meso-structural domain, focusing on defects like microcracks and void growth. In structural-level damage analysis, the macroscale is typically divided into component and structural scales. The component scale examines damage progression in individual structural elements, such as beams and columns, often using detailed finite element or mesoscale models. The structural scale evaluates the global behavior of the entire structure, typically using simplified models like beam or shell elements.Originality/valueTo achieve realistic simulations, it is essential to include as many mesoscale details as possible. However, this results in significant computational demands. To balance accuracy and efficiency, multiscale methods are employed. These methods are categorized into hierarchical approaches, where different scales are processed sequentially, and concurrent approaches, where multiple scales are solved simultaneously to capture complex interactions across scales.

PurposeAs a clean and renewable energy source, wind energy will become one of the main sources of new energy supply in the future. Relying on the stable and strong wind resources at sea, wind energy has great potential to become the primary energy. As a critical part of the wind turbine, the gearbox of a wind turbine often bears a large external load. Especially at sea, due to the effects of ocean corrosion, waves and wind, the burden of the wind turbine gearbox is greater, which brings great challenges to its reliability analysis. This study aims to systematically review the reliability research in wind turbine gearboxes and guide future research directions and challenges.Design/methodology/approachThis study systematically reviews some design requirements and reliability analysis methods for wind turbine gearboxes. Then, it summarizes previous studies on wind load uncertainty modeling methods, including the processing of wind measurement data and the summary of three different classifications of random wind speed prediction models. Finally, existing reliability analysis studies on two major parts of the gearbox are described and summarized.FindingsFirst, the basic knowledge of wind turbine gearboxes and their reliability analysis is introduced. The requirements and reliability analysis methods of wind turbine gearboxes are explained. Then, the processing methods of wind measurement data and three different random wind speed prediction models are described in detail. Furthermore, existing reliability analysis studies on two common parts of wind turbine gearboxes, gears and bearings, are summarized and classified, including a summary of bearing failure modes. Finally, three possible future research directions for wind turbine gearbox reliability analysis are discussed, namely, reliability research under the influence of multiple factors on gears, damage indicators of bearing failure modes and quantitative evaluation criteria for the overall dynamic characteristics of offshore wind turbine gearboxes and a summary is also given.Originality/valueThis paper aims to systematically introduce the relevant contents of wind turbine gearboxes and their reliability analysis. The contents of wind speed data processing, predictive modeling and reliability analysis of major components are also comprehensively reviewed, including the classification and principle introduction of these contents.