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Parametric Study of the Numerical Model of a Bolted Connection of Steel Structure for Photovoltaic Panels
In the face of the reality that unexpectedly mobilized the governments of most central European countries (including Poland), the development of renewable energy sources (RES) seems to be an important direction. Therefore, both wind parks and solar farms will be constructed at double speed for energetic independence. This urgency makes the market of producers of structures for mounting solar panels also need to adapt quickly to the new situation. New constructions adapted to quick assembly with the use of nutless screw connections seem to be one of the best solutions. These structures must not only be easy and quick to install but also durable, which makes the connections resistant to cyclical loads. The speed of assembly of the substructure can be achieved precisely with the help of nutless connections, but their durability should be carefully analyzed. This article presents parametric analyses of the numerical model of this type of connection. The selection of appropriate numerical models for simulation is of key importance in the fatigue strength analysis of bolted connections. This article investigates two different models used in numerical fatigue analyses performed in the Abaqus FEA and FE-Safe program, namely, traditional bolt with nut and innovative self-tapping nutless bolt. Extended parametric analyses of both numerical models were carried out, which ultimately allowed optimization of the fatigue capacity of the connection.
Wind Parks in Poland—New Challenges and Perspectives
The wind farm market in Poland evolved very dynamically in the years 2000–2015. Unfortunately, the high public resistance caused the government in 2016 to freeze the development of this industry by introducing a restrictive act, which practically stopped the wind farm industry overnight. The climate aspects, such as reduction of the carbon footprint, which have been considered and widely discussed for several years at the European Union forums, were a chance to change this situation. The new regulations gave hope that the wind energy industry in Poland would soon be unblocked, unfortunately the commitment to coal was still an effective barrier, which is clearly visible in the presented study. The Russian aggression against Ukraine, which resulted in a blockade of hydrocarbon imports, has completely changed the center of gravity of the Polish energy and heating economy. The article focuses on the accelerated changes in the renewable energy sources (RESs) and the related legislation, especially emphasizing the prospect of building offshore wind farms. The huge European energy crisis means that new solutions, both legislative and technological, which will allow to quickly switch to green energy, must appear in Poland immediately. The direct conversion of green energy from RES farms into thermal energy in the planned investment in heat energy plants is discussed. This article also presents a broad view of new opportunities as well as the challenges and prospects that have recently arisen in the wind energy industry in Poland.
Experimental Research and Computational Analysis of Eco- and Biomaterials
This Special Issue of Materials is dedicated to the exploration and analysis of eco- and biomaterials through experimental research and computational methods [...]
Mechanics of Corrugated and Composite Materials
The main aim of this Special Issue in Materials was to collect interesting and innovative works on the mechanics of corrugated and composite materials [...]
Optimal Design of Double-Walled Corrugated Board Packaging
Designing corrugated board packaging is a real challenge, especially when the packaging material comes from multiple recycling. Recycling itself is a pro-ecological and absolutely necessary process, but the mechanical properties of materials that are processed many times deteriorate with the number of cycles. Manufacturers are trying to use unprecedented design methods to preserve the load-bearing capacity of packaging, even when the material itself is of deteriorating quality. An additional obstacle in the process of designing the structure of paper packaging is the progressive systematic reduction of the grammage (the so-called lightweight process) of corrugated cardboard. Therefore, this research presents a critical look at the process of optimal selection of corrugated cardboard for packaging structures, depending on the paper used. The study utilizes analytical, simplified formulas to estimate the strength of cardboard itself as well as the strength of packaging, which are then analyzed to determine their sensitivity to changes in cardboard components, such as the types of paper of individual layers. In the performed sensitivity analysis, numerical homogenization was used, and the influence of initial imperfections on the packaging mechanics was determined. The paper presents a simple algorithm for the optimal selection of the composition of corrugated cardboard depending on the material used and the geometry of the packaging, which allows for a more conscious production of corrugated cardboard from materials derived, e.g., from multiple recycling.
Efficient Load-Bearing Capacity Assessment of a Degraded Concrete Manhole Using Sectional Homogenization
This study addresses a practical and efficient approach to evaluating the load-bearing capacity of severely degraded concrete manholes. Concrete deterioration, often advanced and highly irregular, can be captured accurately through surface scanning to create a detailed model of the damaged structure and also to build a simplified modeling to enable rapid engineering-level assessment, filling a critical gap in infrastructure maintenance. The repair strategy involves applying an internal polyurea layer, a variable-thickness polyurethane foam layer depending on the degree of localized degradation, and an external polyurea layer to restore the original shape of the manhole. However, these repairs do not fully restore the manhole’s original load-bearing capacity. A full 3D model, encompassing millions of finite elements, would provide a detailed analysis of strength reductions but is impractical for engineering applications due to computational demands. An alternative approach utilizing sectional homogenization is proposed, where sectional properties are sequentially averaged to calculate effective parameters. This approach enables the use of only a few hundred shell elements, each representing thousands of elements from the detailed 3D model, thus providing a rapid, engineering-level assessment of load-bearing reductions in degraded manholes. The study finds that while the repair method restores up to 76% of bending stiffness in heavily corroded sections, it does not fully recover the original load-bearing capacity.
Digital Twin Model for Predicting Hygrothermal Performance of Building Materials from Moisture Permeability Tests
Moisture transport in building materials significantly influences their durability, mechanical integrity, and thermal performance. This study presents an experimental investigation of moisture permeability in a range of traditional and modern wall elements, including autoclaved aerated concrete (ACC), ceramic blocks, silicate blocks, perlite concrete blocks, and concrete units. Both vapor diffusion and capillary transport mechanisms were analyzed under controlled climatic conditions using gravimetric and hygrometric methods. Among the tested materials, autoclaved aerated concrete (AAC) was selected for detailed numerical modeling because of its high porosity, strong capillarity, and widespread use in modern construction, which make it especially vulnerable to moisture-related degradation. Based on the experimental findings, a digital twin was developed to simulate hygrothermal behavior of walls made of ACC under various environmental conditions. The model incorporates advanced moisture transport equations, capturing diffusion and capillary effects while considering real-world variables, such as relative humidity, temperature fluctuations, and wetting–drying cycles. Calibration demonstrated strong agreement with experimental data, enabling reliable predictions of moisture behavior over extended exposure scenarios. This integrated approach provides a robust engineering tool for assessing the long-term material performance of AAC, predicting degradation risks, and optimizing material selection in humid climates. The study illustrates how coupling experimental data with digital modeling can enhance the design of moisture-resistant and durable building envelopes.
Three-layer Repair Coating System for Manholes, Pump Stations, and Tanks in Aggressive Sulfate Environment
Advancements in the repair and protection of water and wastewater infrastructure are now focused on using an innovative material called polyurea. Distinguished by its rapid curing time and versatile applications, polyurea is applied using a spray gun with high-pressure pumps. The introduction of new building materials is part of ongoing efforts to meet stringent environmental, health, and performance standards, and polyurea offers significant improvements by eliminating solvents and volatile organic compounds (VOCs). This paper presents a technological protocol starting with inspection and cleaning, followed by drying, and ending with the application of three layers: a moisture-blocking base layer, a rigid polyurethane middle layer for structural reinforcement, and a final sealing and anti-corrosion layer. This innovative method ensures a homogeneous, seamless structure, enhances construction durability, and accelerates the repair process, allowing immediate resumption of operation. Designed specifically for aggressive wastewater environments, this system is characterized by excellent corrosion resistance, making it ideal for water and wastewater infrastructure elements such as reinforced concrete manholes, sewage pumping stations, and tanks. Customizable polyurea properties allow personalization based on environmental aggressiveness, structure size, and abrasion resistance, representing a significant advancement in infrastructure maintenance technology. The paper showcases this modern repair and renovation method, highlighting its applications, benefits, and potential to revolutionize water and wastewater infrastructure maintenance in challenging conditions. The effectiveness of this solution is also compared with traditional methods, demonstrating the superiority of the three-layer system in terms of waterproofing, sulfuric acid resistance, monolithic structure, and application time.
On the use of artificial intelligence in predicting the compressive strength of various cardboard packaging
AbstractArtificial intelligence is increasingly used in various branches of engineering. In this article, artificial neural networks are used to predict the crush resistance of corrugated packaging. Among the analysed packages were boxes with ventilation openings, packages with perforations and typical flap boxes, which make the proposed estimation method very universal. Typical shallow feedforward networks were used, which are perfect for regression problems, mainly when the set of input and output parameters is small, so no complicated architecture or advanced learning techniques are required. The input parameters of the neural networks are selected so as to take into account not only the material used for the production of the packaging but also the dimensions of the box and the impact of ventilation holes and perforations on the load capacity of individual walls of the packaging. In order to maximize the effectiveness of neural network training process, the group of input parameters was changed so as to eliminate those to which the sensitivity of the model was the lowest. This allowed the selection of the optimal configuration of training pairs for which the estimation error was on the acceptable level. Finally, models of neural networks were selected, for which the training and testing error did not exceed 10%. The demonstrated effectiveness allows us to conclude that the proposed set of universal input parameters is suitable for efficient training of a single neural network model capable of predicting the compressive strength of various types of corrugated packaging.
Application of the generalized nonlinear constitutive law in numerical analysis of hollow-core slabs
Optimization of Rectangular Tank Cross-Section Using Trust Region Gradient Method
"In various industries, rectangular tanks are commonly used for storing liquids and other materials. The design and optimization ofthese tanks are crucial for ensuring structural integrity and material efficiency. Traditional designs often utilize constant wallthickness, which does not align optimally with the stress distribution, leading to potential overuse of materials and increased costs.Recent studies have shown that tanks with variable wall thickness, such as trapezoidal cross-sections, can better match stressdistributions, particularly under hydrostatic loads, resulting in more efficient use of materials. This research aims to build uponprevious studies by introducing an advanced optimization algorithm based on the Trust Region Gradient Method to further refinethe cross-sectional design of rectangular tanks. The primary objective is to minimize the material usage while maintainingstructural safety and performance under various load conditions, including hydrostatic pressure and thermal effects. The proposedalgorithm iteratively adjusts the tank's wall thickness, seeking an optimal configuration that reduces bending moments andmaterial costs. Initial static calculations is verified using the finite difference method, emphasizing energy minimization conditionsfor elastic strain in bent plates on elastic foundations. This approach is compared with traditional discretization methods tovalidate accuracy. The trust region method is then applied to optimize the design, with a focus on achieving a balance betweenstructural integrity and economic feasibility. Preliminary results indicate that the trust region gradient method can significantlyenhance the design process, leading to substantial material savings and improved structural performance. The algorithm'seffectiveness is demonstrated through case studies comparing tanks with constant and variable wall thickness. This researchcontributes to sustainable construction practices by promoting designs that use materials more efficiently and meet safetystandards."
Parametric Optimization of Thin-Walled 3D Beams with Perforation Based on Homogenization and Soft Computing
The production of thin-walled beams with various cross-sections is increasingly automated and digitized. This allows producing complicated cross-section shapes with a very high precision. Thus, a new opportunity has appeared to optimize these types of products. The optimized parameters are not only the lengths of the individual sections of the cross section, but also the bending angles and openings along the beam length. The simultaneous maximization of the compressive, bending and shear stiffness as well as the minimization of the production cost or the weight of the element makes the problem a multi-criteria issue. The paper proposes a complete procedure for optimizing various open sections of thin-walled beam with different openings along its length. The procedure is based on the developed algorithms for traditional and soft computing optimization as well as the original numerical homogenization method. Although the work uses the finite element method (FEM), no computational stress analyses are required, i.e., solving the system of equations, except for building a full stiffness matrix of the optimized element. The shell-to-beam homogenization procedure used is based on equivalence strain energy between the full 3D representative volume element (RVE) and its beam representation. The proposed procedure allows for quick optimization of any open sections of thin-walled beams in a few simple steps. The procedure can be easily implemented in any development environment, for instance in MATLAB, as it was done in this paper.
Optimal Design of Rectangular Tank Walls With Ribs Using Numerical Models and Global Optimization
This paper addresses the optimization of the cross-section in rectangular above-ground tank walls, incorporating vertical ribs and an optional top ring. The objective is to minimize the volume of concrete used, while maintaining key performance criteria such as keeping the maximum tensile stress below the material’s allowable limit and minimizing deflections. The analysis is performed using the finite element method (FEM), with the optimization handled through a local gradient-based algorithm (trust region method), supported by a multistart technique to navigate the complexity of the design space and avoid suboptimal solutions. The results demonstrate that this approach effectively reduces concrete consumption without exceeding the tensile stress limits or causing excessive deflection, offering more efficient and cost-effective designs for rectangular tanks used in water storage applications. This method provides valuable insights into the balance between material usage and performance constraints, contributing to sustainable engineering practices.
