Periodica Polytechnica (Budapest University of Technology and Economics)
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Response Spectrum of Piecewise Linear Elastic Structures
Full text linkResponse spectra are helpful in the structural engineering practice for the design with earthquake as an extreme load case. However, it is restricted to the linear analysis, except for the plastic behavior. The linear analysis uses a single stiffness only, and by this, the low-level nonlinearities, as the opening and closure of cracks in reinforced concrete structures, are neglected. In this paper, we investigate single-degree-of-freedom systems with two linear elastic states. The response of the piecewise linear elastic structure is compared to the linear response for artificial earthquake accelerograms confined to a design response spectrum. The analysis shows that a high difference in the stiffnesses of the two states may result in a considerable increase in the response. At the same time, states with small relative differences in their stiffness have a maximum response below or close to the response of the linear system. Thus, the neglect of the low-level nonlinearity, as the opening and closing of a crack does not affect the assessment of the structure
Advancements in Heat Exchangers for Improved Engine Cooling: A Comprehensive Literature Review
Full text linkThis literature review investigates the dynamic environment of heat exchangers employed in engine cooling systems, exploring advancements and innovations that have shaped the field. The increasing demand for enhanced engine performance, fuel efficiency, and environmental sustainability has propelled research into heat exchanger technologies. The review encompasses a comprehensive analysis of different types of heat exchangers, materials utilized, design considerations, and performance evaluations, with a keen focus on their respective applications in engines and radiators. The various kinds of heat exchangers belong to the most important themes, such as air-to-air, liquid-to-liquid, finned-tube, and plate heat exchangers, with a focus on their respective advantages, drawbacks, and applications. Design considerations encompass size, shape, and configuration, addressing the factors influencing design choices in modern engine cooling systems. A comprehensive evaluation of heat exchanger performance is carried out, taking into account variables including energy consumption, pressure drop, and heat transfer efficiency. The review incorporates insights from experimental methods and simulations used in assessing heat exchanger performance. Challenges in the field are discussed, providing a nuanced understanding of current limitations, and potential areas for improvement are explored. The literature review concludes with a synthesis of key findings, emphasizing the current state of knowledge in heat exchangers for engine cooling. The abstract aims to provide a concise overview of the multifaceted aspects covered in the literature review, offering valuable insights for researchers and engineers in the advancement of engine cooling systems
Assessing Road Safety of the Peshawar-Rawalpindi Section of National Highway (N-5) in Pakistan Using iRAP
Full text linkThe road safety situation in Pakistan is critical, with an average 25,781 fatalities due to road accidents. This study considered the N-5 national highway section between Rawalpindi and Peshawar, employing the International Road Assessment Programme (iRAP). The data collected reveals that many road sections in this area have low safety ratings, highlighting significant risks and substandard road conditions for travelers. Through the iRAP, proposed countermeasures were evaluated and analyzed for the purpose of improving safety ratings on N-5, in line with the Sustainable Development Goals (SDGs) for 2020–2030, targeting road safety performance goals 3 and 4. To meet the SDG target of having 75% of road segments rated 3 stars or higher, the study includes a comprehensive risk assessment and mapping, safety interventions, a Safety Rating Investment Program (SRIP), Fatal and Serious Injuries (FSI) Estimation, and Benefit-Cost Ratio (BCR) analysis. The findings stress the importance of a holistic approach, combining both geometric and non-geometric measures (such as pavement maintenance, traffic control devices, street lighting, school zone crossings, and clearing roadside hazards) to fully achieve global road safety objectives
A Hybrid Deep Learning and Statistical Approach for Fault Detection and Diagnosis in AGRU Systems: Integration with Aspen Plus and Explainable AI
Full text linkFault detection and diagnosis are vital functions in process industries, supporting real-time monitoring and ensuring plant safety. However, the presence of complex, high-dimensional, and highly correlated process data presents a significant challenge for traditional monitoring systems. In natural gas processing, the acid gas removal unit is a critical subsystem responsible for removing acid gases such as hydrogen sulfide and carbon dioxide. Faults such as foaming, tray corrosion, cooler fouling, low gas flow, and reduced amine circulation are common in AGRUs but have received limited attention in the literature, highlighting a significant research gap. To address this, a comprehensive study was conducted by simulating the AGRU process and its associated faults using Aspen Plus Dynamics. This enabled the generation of realistic, multivariate time-series data under normal and faulty operating conditions. For the fault detection phase, two approaches were developed and comparatively evaluated: principal component analysis, which employs Hotelling's T2 and squared prediction error metrics, and a long short-term memory autoencoder, which utilizes reconstruction error and leverages sequential learning. Subsequently, a fault diagnosis was performed using bidirectional recurrent neural networks, specifically Bi-GRU and Bi-LSTM models, which were trained to classify fault types based on their temporal signatures. The Bi-GRU model demonstrated superior performance with an accuracy of 99.8% and an F1-score of 99.6%, indicating its suitability for robust fault classification. To enhance model interpretability, shapley additive explanations were applied to identify critical input variables influencing model predictions, and the results were compared with those from local interpretable model-agnostic explanations
Quantifying the Stability–defect–layer Trade-off in Surfactant-assisted Fluid-dynamic Exfoliation of Few-layer Graphene
Full text linkIn this paper we report an all-aqueous fluid-dynamic exfoliation route to low-defect few-layer graphene (FLG) using the non-ionic surfactant Triton X-100. Systematic variation of surfactant concentration (1–5 wt%) and processing time (0.5–1.5 h) revealed a quantitative interplay among stability, defect, and layer. Raman spectroscopy and 2D band Lorentzian modeling revealed that the few-layer graphene (FLG) predominantly consists of four layers, with very low defect ratios (ID/IG = 0.02–0.11; I2D/IG = 0.18–0.30). Raman imaging confirmed spatially uniform G band intensity, while the edge-activated D band signals indicated residual edge defects characteristic of shear-cleaved flakes. Transmission electron microscopy and particle size analysis yielded lateral sizes of ~1.29–1.43 µm with a narrow distribution. Fourier transform infrared spectroscopy verified that the defects were not oxidation-derived, while UV–Vis showed graphene π–π absorption at 270–276 nm. This work establishes a short-duration, low-cost, and solvent-free approach for producing stable FLG suitable for liquid-phase applications and provides process–structure metrics for benchmarking across exfoliation studies
Reliability Analysis of Stone Columns Improved Ground for Mitigation of Liquefaction
Full text linkStone columns are widely used to improve ground performance and mitigate liquefaction in weak or loose soils. However, conventional deterministic design methods fail to account for the uncertainties in soil and column properties, which can significantly affect performance under seismic loading. To address this gap, this study presents a reliability-based framework for assessing the effectiveness of stone columns in reducing liquefaction potential. The analysis considers key random variables – seismic acceleration (amax), saturated unit weight (γsat), stone friction angle (φ′c ), shear wave velocity (Vs), and column diameter (Dc) – under normal and lognormal distributions. Probabilistic methods, including First Order Second Moment (FOSM), Point Estimation Method (PEM), and Monte Carlo Simulation (MCS), were applied to evaluate the reliability index (β). Results show that increasing parameter uncertainty leads to a significant reduction in β, even when the deterministic safety factor exceeds unity (≈1.50). Sensitivity analysis reveals that Vs and γsat have the greatest influence on reliability, while Dc and amax exhibit minimal impact. These findings underscore the necessity of incorporating probabilistic approaches in design and provide insights for simplifying reliability assessment by reducing the number of random variables without compromising accuracy
Sustainable Use of Construction Waste: Fire Resistance and Strength Characteristics of Recycled Aggregate Concrete for Sustainable Concrete
Full text linkThe pursuance of sustainability in construction has propelled the adoption of innovative materials, with recycled aggregate concrete (RAC) emerging as a pivotal solution to address the environmental challenges posed by traditional concrete. Sustainability in construction has become a global priority, driven by the need to reduce environmental impacts and conserve natural resources. The increasing use of green building certifications like LEED and BREEAM highlights the push towards innovative materials, including RAC. With construction and demolition (C&D) waste accounts for 31% of Europe's total annual waste and global consumption of natural aggregates (NAs) projected to double in the coming decades, recycling concrete waste into recycled concrete aggregates (RCA) has emerged as a sustainable alternative. Studies show that RCA use can reduce greenhouse gas emissions by 65% and non-renewable energy consumption by 58%. Despite advancements in RAC research, challenges remain, particularly regarding its performance under extreme conditions like fire. This study investigates the mechanical and durability properties and potential of using recycled aggregate(RA) in conventional concrete as a replacement in varying percentages of recycled fine and coarse aggregates (0%, 25%, 50%, 75%, and 100%) after exposure to different elevated treatment temperatures (20, 100, 200, 300, 400, 500, 600, and 800 °C). The findings aim to address gaps in understanding the thermal behavior of RAC and promote its adoption as an environmentally friendly construction material
Experimental Characteristics Impact on Bond Strength at Elevated Temperatures: A Literature Review
Full text linkEvaluating structure strength characteristics post-fire or when subjected to prolonged periods of elevated temperature is essential, as these conditions degrade concrete strength, specifically bond strength between rebar and concrete. Residual bond strength can be determined through direct pull-out or beam tests. Several factors influence bond strength at normal temperatures, including the properties of the concrete and the rebar, the specimens' characteristics, the concrete cover, and the stress state of the specimen during testing. The situation becomes more complex at higher temperatures as heating introduces additional variables. In this context, the bond is influenced by the heating characteristics of the specimen, such as the heating rate and cooling process. While researchers acknowledge these factors, the degree of their impact is still a subject of debate. This paper aims to review the existing literature on bond strength at elevated temperatures and to explore how various factors influence this strength under such conditions. The study gathers data to examine the bond-slip curve at high temperatures, the effects of experimental variables on bond strength, and the residual bond strength after exposure to elevated temperatures. Key experimental characteristics considered in this paper include the heating procedure, heating rate, heating duration, cooling regime, properties of the rebar, properties of the specimen, and the relationship between concrete strength and bond strength
Digital Twins in Heritage Conservation and Visitor Engagement: Comparative Case Studies from Four Historic Sites
Full text linkThis study explores the application of digital twin technologies in heritage conservation and visitor engagement, focusing on their practical use in preserving and enhancing access to culturally significant sites. Digital twins, which are virtual replicas of physical environments, enable real-time monitoring and simulation, offering innovative tools for conservation management and experiential interpretation. Through a systematic literature review and comparative analysis of four case studies, Pompeii, Notre-Dame, the Colosseum, and Hagia Sophia, this research examines how digital twins are implemented across varying contexts. The findings reveal that digital twins support predictive maintenance, structural monitoring, and restoration planning while also enabling immersive experiences through virtual and augmented reality. These technologies provide remote access, interactive storytelling, and tailored tours, fostering a deeper connection with heritage. In terms of conservation, digital twins support predictive maintenance, structural monitoring, and evidence-based decision-making. The structured comparison highlights how digital twin systems balance preservation needs with modern engagement demands. While challenges such as data accuracy, cultural sensitivity, and technological infrastructure remain, the study concludes that digital twins represent a valuable model for integrating conservation and visitor experience in heritage site management. Future developments in immersive technologies and broader adoption of digital twins could further enhance the management and appreciation of cultural heritage worldwide
Development of Part Cooling in 3D Printer through the Design of a Custom Cooling Duct Using Generative Design
Full text linkThis study addresses the improvement of part cooling in FFF 3D printing, using the Creality Ender 3 V2 as a case study. The stock cooling system directs airflow from a single side, which leads to uneven cooling and reduced surface quality. To overcome this limitation, both a reference redesign and a generative design approach were investigated. The development involved flow domain optimization with Autodesk Fusion's Generative Design module, followed by CFD simulations in Ansys CFX. Results indicate that generative design can enhance cooling performance and enable more effective two-sided airflow. At the same time, challenges remain in achieving uniform outlet velocity distribution, as flow separation effects may occur. Overall, the study demonstrates the potential of generative design as an innovative tool for accelerating fluid dynamics design processes, while highlighting the need for further refinement and experimental validation