Search Results (355)

Concrete-filled steel tube (CFST) columns are composite structural elements preferred in various engineering structures due to their superior properties compared to those of traditional structural elements. However, fire resistance analyses are complex due to CFST columns consisting of two components with different thermal and mechanical properties. Significant challenges arise because current design codes and guidelines do not provide clear guidance for determining the time-dependent fire performance of these composite elements. This study aimed to address the existing design gap by investigating the fire behavior of circular long CFST columns under axial compressive load and developing robust, accurate, and reliable design models to predict their fire performance. To this end, an up-to-date database consisting of 62 data-points obtained from experimental studies involving variable material properties, dimensions, and load ratios was created. Analytical design models were meticulously developed using two advanced soft computing techniques: artificial neural networks (ANNs) and genetic expression programming (GEP). The model inputs were determined as six main independent parameters: steel tube diameter (D), wall thickness (t_s), concrete compressive strength (f_c), steel yield strength (f_sy), the slenderness ratio (L/D), and the load ratio (μ). The performance of the developed models was comprehensively compared with experimental data and existing design models. While existing design formulas could not predict time-based fire performance, the developed models demonstrated superior prediction accuracy. The GEP-based model performed well with an R-squared value of 0.937, while the ANN-based model achieved the highest prediction performance with an R-squared value of 0.972. Furthermore, the ANN model demonstrated its excellent prediction capability with a minimal mean absolute percentage error (MAPE = 4.41). Based on the nRMSE classification, the GEP-based model proved to be in the good performance category with an nRMSE value of 0.15, whereas the ANN model was in the excellent performance category with a value of 0.10. Fitness function (f) and performance index (PI) values were used to assess the models’ accuracy; the ANN (f = 1.13; PI = 0.05) and GEP (f = 1.19; PI = 0.08) models demonstrated statistical reliability by offering values appropriate for the expected targets (f ≈ 1; PI ≈ 0). Consequently, it was concluded that these statistically convincing and reliable design models can be used to consistently and accurately predict the time-dependent fire resistance of axially loaded, circular, long CFST columns when adequate design formulas are not available in existing codes. Full article

The study of the dynamics during droplet breakup is fascinating to engineers. Some industrial applications include fire extinguishing by sprinkler systems, painting of various components, washing processes, and fuel spraying in internal combustion engines, which involve the interaction between liquid droplets, gaseous flow field, and walls. In this work, washing operations effectiveness of civil aviation aircraft engines is analyzed. Periodic washing operations are necessary to slow down the effects of particle deposition, e.g., gas turbine fouling, to reduce the specific fuel consumption and the environmental impact of the gas turbine operation. This analysis describes the dynamics in the primary breakup, related to the breakup of droplets due to aerodynamic forces, which occur when the droplets are set in motion in a fluid domain. The secondary breakup is also considered, which more generally refers to the impact of droplets on surfaces. The latter is studied with particular attention to dry surfaces, investigating the limits for different breakup regimes and how these limits change when the impact occurs with surfaces characterized by different wettability. Surfaces with different roughness are also compared. All the tested cases are referred to surfaces at ambient temperature. Dimensionless numbers generalize the analysis to describe the droplet behavior. The analysis is based on several data reported in the open literature, demonstrating how different washing operations involve different droplet breakup regimes, generating a non-trivial data interpretation. Impact dynamics, droplet characteristics, and erosion issues are analyzed, showing differences and similarities between the literature data proposed in the last twenty years. Washing operation and the effects of gas turbine fouling on the aero-engine performance are still under investigation, demonstrating how experiments and numerical simulations are needed to tackle this detrimental issue. Full article

Energy storage is vital for on-demand electricity generation from renewable sources like wind and solar. Besides employing batteries, retrofitting conventional fossil-fired power plants with thermal energy storage might present a highly cost-effective solution. State-of-the-art molten salt storage systems currently operate at a maximum temperature of 565 °C. At a higher permanent temperature, nitrate salts start to decompose. The actual wall temperatures of power components for heating, such as solar receivers and electrical heaters, may exceed temperature limits. To date, there is no clear threshold identified up to which heating surfaces in contact with nitrate salt can be operated without leading to the degradation of the salt, which is inevitably followed by increased corrosivity. In this study, possible mechanisms affecting the maximum permissible wall temperature of heating surfaces are identified. The local production of oxygen and nitrite at hot surfaces and its accumulation in the entire system is looked at in an experiment with 9.3 kg of nitrate salt. The effect of high wall temperatures on the evolution of oxygen and nitrite content over time is monitored and analyzed. Parametric studies with an experimentally validated physical model focusing on the nitrate/nitrite equilibrium reveal major influencing factors, with wall temperatures significantly exceeding current design limits. These findings potentially allow for more compact and cost-effective heating components. This work supports the advancement of high-temperature thermal energy storage systems essential for the scalability and economic competitiveness of renewable energy infrastructure. Full article

Fire safety is a crucial issue for buildings, especially with the rise of modular construction, which demands materials that combine lightness with mechanical performance and stability. This study investigates a new concept for single-story modular constructions, made up of 3D cells assembled from thermally and acoustically pre-insulated concrete panels. These panels comprising four walls and two slabs forming the module, are stiffened, with thicknesses of only 5 cm for the walls and 7 cm for the slabs. Their constituent material is a self-compacting, high-volume steel-fiber concrete, containing 80 kg/m³ of steel fibers and 0.3 kg/m³ of polypropylene fibers. Experimental tests on a full-scale wall and slab revealed that adding 0.3 kg/m³ of polypropylene fibers effectively prevents concrete from splintering and achieves the necessary 30 min fire resistance. Standardized full-scale fire tests on walls and slabs confirmed that these thin structures meet fire resistance, insulation, and airtightness standards. The high volume of steel fibers provides ductility, maintaining structural integrity despite concrete spalling. The maximum spalling depth observed in some areas ranged 35 to 50 mm, without compromising structural performance. Overall, the modular system satisfies the fire safety requirements for structural stability (no collapse) and performance in single-story modular construction. Full article

Surveys and excavations carried out between 2004 and 2019 around the Vlach town of Samarina, in the Pindos Mountains of Western Macedonia (Greece), have yielded potsherds that can be attributed to different historical periods. The data collected so far suggest a long human presence in this region of the northern Pindos spanning from the Middle Pleistocene to the late Middle Ages. The ceramic fragments from the Historical Camp (HC), Kirkouri (KRK), the Holy Cross Church (SMC), Mt. Anitsa (Anitsa), Avgo (VGO), the Mirminda Pass (VLC), Mt. Vasilitsa (VSL), and the saddle between Mts. Bogdhani and Gurguliu have been studied in detail. Despite their fragmentary state, a database has been created with the morphological and typological characteristics of the potsherds and the sites from which they were retrieved. Coarse and fine ware potsherds have been identified. According to their manufacturing characteristics, they can be attributed to different Roman and medieval periods. A diassarion of the Larissa mint shows that connections between the mountain highlands and the lowlands were already active during the period of Emperor Augustus. The Samarina potsherds are probably related to the movements of Vlach shepherds, who spent long periods in these mountains with their flocks. This impression is confirmed by the presence of one vessel wall fragment which was directly in contact with fire and a few small vessel bases. The presence of ceramic vases is closely linked to the transportation of primary or secondary food supplies in a pre-cooked form or as liquids. We know that Vlach shepherds, as many other groups of Eurasian shepherds, never manufactured ceramic vessels even in their villages. Instead, they used different types of wooden and metal containers for cooking, drinking, and other tasks associated with pastoral activities, such as keeping milk and making cheese and butter, for example. Following these observations, our aim has been to define the vessel types used by the Vlach shepherds, which exhibit some kind of uniformity from the Roman to the Middle Ages. Full article

Interlocking Compressed Earth Blocks (ICEBs) offer a sustainable alternative to conventional fired-clay bricks but remain hindered by inconsistent geometric designs and limited standardization. This study develops a stakeholder-weighted Analytic Hierarchy Process (AHP) framework to evaluate and select the most suitable ICEB geometry for sustainable and seismic-ready construction in developing regions. Five evaluation criteria—size, weight, interlocking effectiveness, reinforcement/grout provision, and handling ergonomics—were prioritized based on expert input from masons, engineers, architects, and researchers. The synthesized results ranked the HiLo-Tec-type geometry highest, followed by Thai-Rhino, Auram, and Hydraform designs. Unit weight (0.289) and reinforcement capacity (0.261) emerged as dominant decision factors. Sensitivity analysis confirmed the robustness of rankings under varying weight perturbations. The AHP framework identifies the top-ranked geometry, whose structural performance was examined experimentally through a full-scale cyclic test on a grouted double-wythe ICEB wall, revealing enhanced ductility and residual strength compared with traditional brick masonry. The proposed framework demonstrates that selected ICEB geometry can balance ergonomic and structural performance while meeting seismic resilience demands. Beyond geometry selection, the model provides a replicable decision-support tool adaptable for regional material innovations in sustainable construction. Full article

Newly brewed Baijiu often contains harmful substances such as mercaptan and methanol, which are spicy and harmful to health. At present, this is mainly solved by long-term cellaring, but this is faced with some problems such as a long cycle, high cost, high fire hazards and so on. Therefore, based on the principle of liquid jet cavitation explosion catalyzing the heterogeneous association of Baijiu molecules, this paper first developed the physical aging process and equipment without radiation and additives. Then, based on the traditional computational fluid dynamics (CFD) model of high-speed jet simulation, an N-CFD model which can accurately simulate the cavitation explosion catalytic process of high-speed jet of Baijiu was established by optimizing the three sub models of conservation, turbulence and VOF. Finally, the N-CFD model was used to optimize the distance between the nozzle and the reaction chamber wall of the new aging equipment. Through the 15 min aging experiment on 100 L Baijiu, the methanol concentration of Baijiu decreased by 68.14 ± 2.25%, and the concentration of ethyl acetate, ethyl lactate and ethyl palmitate increased from 6.105 ± 0.014, 3.498 ± 0.015 mg/L and 0.621 ± 0.010 mg/L to 6.332 ± 0.016, 4.868 ± 0.012 mg/L and 0.681 ± 0.008 mg/L. The results show that the aging technology equipment can adjust the self-coupling characteristics and dynamic characteristics of various molecules in Baijiu through high-speed jet, and catalyze the alternating phase transition and association of various molecules. Finally, the goal of high-efficiency and healthy aging Baijiu without additives was achieved, which helps the rapid and healthy development of the Baijiu brewing industry. Full article

As a critical element within the prefabricated structural system, the prefabricated shear wall connected by sleeve grouting is renowned for its superior mechanical performance and high construction efficiency. It is widely applied in mid- and high-rise buildings. However, under fire conditions, not only do the material properties degrade, but the structural connections may also fail, significantly compromising the structural stability and safety. Therefore, this study delves into the fire resistance performance of such prefabricated shear walls. The research primarily focuses on analyzing fire resistance characteristics, including deformation patterns, lateral and axial deformations, fire resistance limits, and other performance metrics, for both prefabricated and cast-in-place shear walls subjected to three hours of single-sided fire exposure. Additionally, a parametric analysis is performed. The results reveal that, after three hours of single-sided fire exposure, the temperature distribution patterns at the mid-width and mid-height sections of the prefabricated shear wall generally resemble those of the cast-in-place wall, displaying arch-shaped and strip-shaped distributions, respectively. However, due to the presence of sleeves, higher temperatures are observed near the sleeve areas in the prefabricated wall, along with a more extensive high-temperature zone. Throughout the three-hour fire exposure, both types of shear walls demonstrated satisfactory structural stability and thermal insulation performance, meeting the requirements for a first-level fire resistance rating (3 h). Nevertheless, greater axial and lateral deformations were noted in the prefabricated shear wall. Key factors influencing the fire resistance performance of the sleeve-connected prefabricated shear wall include the axial compression ratio, longitudinal reinforcement diameter, protective layer thickness, and height-to-thickness ratio. Specifically, axial deformation is found to be directly proportional to the axial compression ratio and height-to-thickness ratio, while inversely proportional to the longitudinal reinforcement diameter and protective layer thickness. Lateral deformation is directly proportional to the axial compression ratio and longitudinal reinforcement diameter, and exhibits a trend of initially increasing and then decreasing with an increase in protective layer thickness, and initially decreasing and then increasing with an increase in the height-to-thickness ratio. Full article

To address the challenges of combustion stability and pollutant control during biomass co-combustion in coal-fired boilers under deep peak regulation, a numerical simulation study was conducted on a 660 MW front-and-rear wall opposed-fired pulverized coal boiler using computational fluid dynamics (CFD) technology. First, the reliability of the numerical model was validated under the Boiler Maximum Continuous Rating (BMCR) condition by comparing the simulated results of furnace outlet temperature and NO concentration with on-site operational data, with relative errors of 1.2% and 1.9%, respectively, both within the acceptable range of 5%. Subsequently, the effects of different biomass co-combustion ratios (0%, 5%, 10%, 15%, 20%) and injection positions (primary air nozzles of lower, middle, and upper burners) on the in-furnace velocity field, temperature field, component distribution (O₂, CO, CO₂), and NO emissions were systematically analyzed. The results indicate that increasing the biomass co-combustion ratio does not alter the overall variation trend of flue gas components but significantly affects their concentrations: the O₂ content at the furnace outlet decreases gradually, while the CO₂ content increases, and the NO emission concentration decreases continuously. A 20% co-combustion ratio is identified as the optimal choice, balancing combustion efficiency and NO reduction. Regarding injection positions, biomass injected at the middle burner’s primary air nozzle achieves the best NO control effect, reducing NO emissions by 22% compared to pure coal combustion. This is attributed to the formation of a stable reducing atmosphere in the main combustion zone, which facilitates NO_x reduction. The research findings provide valuable theoretical references and technical support for the parameter optimization and safe, low-emission operation of biomass co-combustion in large-scale coal-fired boilers. Full article

The flexible operation of coal-fired boilers poses significant challenges to thermal safety, particularly due to delayed responses in wall temperature under variable load conditions, which may lead to overheating risks and reduced equipment lifespan. To address this issue, we propose a PLO-KAN framework for high-precision prediction of high-temperature superheater wall temperatures. The framework integrates a Kolmogorov–Arnold Network (KAN) with learnable B-spline activation functions to enhance interpretability, a sliding-window strategy to capture temporal dependencies, and Polar Lights Optimization (PLO) for automated hyperparameter tuning, balancing local exploitation and global exploration. The method is validated using 10,000 operational samples from a 1000 MW ultra-supercritical once-through boiler, with 68 key features selected from 106 candidates. Results show that the proposed model achieves high accuracy and robustness in both single-step and multi-step forecasting, maintaining reliable performance within a five-minute prediction horizon. The proposed method provides an efficient and interpretable solution for real-time wall temperature prediction, supporting proactive thermal management and enhancing operational safety in coal-fired power plants. Full article

The aquaculture industry generates large amounts of shell waste, with limited recycling options at the industrial scale. This study explores the feasibility of substituting 20% of gypsum with seashell waste to produce sustainable, fire-resistant panels for non-load-bearing walls on a semi-industrial scale (2.4 × 2.2 × 0.1 m). The new composite exhibits high density (≈1500 kg/m³) and mechanical performance comparable to commercial gypsum. Thermal and fire tests confirmed its excellent insulation and stability: after 4 h of standard fire exposure, the non-exposed surface temperature remained below 80 °C, meeting European fire-resistance criteria. The incorporation of shell waste slightly reduced density and thermal conductivity (0.23 W/mK at 500 °C) without affecting strength or surface hardness. Environmental characterization revealed leaching and radionuclide levels well below regulatory limits, confirming its safety for building use. Overall, this work demonstrates, for the first time at a semi-industrial scale, the technical and environmental feasibility of reusing seashell waste as a gypsum substitute for fireproof materials. The proposed approach advances circular-economy strategies for aquaculture residues, providing an innovative pathway toward sustainable and low-impact construction products. Full article

Building-Integrated Photovoltaics (BIPV), which are used for building exteriors such as walls, roofs, balconies, and awnings, play a significant role in reducing greenhouse gas emissions. However, since the back sheet, sealant, junction box, and cable of BIPV modules are made of flammable plastic materials, fire protection technologies are needed to ensure fire safety. The aim of this work is to evaluate the fire safety performance of BIPV modules coated with fire-resistant (FRs) and flame-retardant (FRt) materials. The test results show that the performance of the FRs coating was excellent in terms of fire blocking, physical properties, and durability, compared to the FRt coating. Surface damage, such as cracks and blisters, was observed on the FRt coating during the impact and acid resistance tests, whereas the FRs coating demonstrated superior durability without any defects. Specifically, aluminum hydroxide (ATH, 5–10 wt%) added to the FRs coating promoted an endothermic reaction that lowered the flame temperature, released H₂O, and stably formed an Al₂O₃ heat-shielding layer. Due to this reaction, the suppression of the fire spread by the BIPV modules was the best compared to that of Mg, Ti, and Si-based additives. Full article

This study experimentally and numerically examines the structural and seismic performance of recycled solid-brick masonry infills and load-bearing walls constructed from demolition materials. Solid bricks recovered from demolished structures were reused as infill in reinforced concrete (RC) frames and as standalone walls. Five full-scale panels, bare, 50% infilled, and 100% infilled frames, were tested under diagonal compression in accordance with ASTM E519-17, simulating in-plane seismic loading. Results showed that fully infilled frames exhibited a 149% increase in diagonal shear strength but a 40% reduction in ductility relative to the bare frame, indicating a trade-off between stiffness and deformation capacity. Finite element simulations using the Concrete Damaged Plasticity (CDP) model reproduced the experimental load–displacement curves with close agreement (within 6–8% in peak load) and captured the main failure patterns. Reusing cleaned demolition bricks reduces the demand for new fired bricks and helps divert construction waste from landfill, contributing to sustainable and circular construction. The findings confirm the potential of recycled masonry for low-carbon and seismic-resilient construction, provided that ductility limitations are appropriately addressed in design. Full article

As coal-fired power plants shift from being primary power sources to operating as flexible peak-shaving units, the reheater—a critical component of the boiler’s ‘four tubes’—has attracted significant attention. This study focuses on the tube wall temperature distributions of the reheater at different loads and measurement points, analyzing factors that contribute to its uneven heat distribution. The results indicate that the heat distribution across the tubes of the low temperature reheater (LRH) is uneven. From the left to the right side of the tube panel, the tube wall temperatures form two parabolic profiles. The tubes most susceptible to overheating are the first tube of the 91st panel and the first tube of the 181st panel. For the high-temperature reheater (HRH), at an electrical load of 217.7 MW, the maximum temperature difference is higher than that of LRH. At all other electrical loads, however, the maximum temperature difference of the HRH is lower than that of the LRH. The LRH is at a higher risk of tube rupture caused by uneven heating compared to the HRH. Full article

The Global Cement and Concrete Association (GCCA) estimated that by 2050, 36% industry-wide sustainable value will be created, which includes sequestering CO₂ into the cement and concrete industry to produce commercially feasible high-value products. Direct utilization of CO₂ in the cement and concrete industry, which utilizes natural and sustainable materials, is gaining momentum. Naturally occurring mixtures of hydro magnesite and huntite are important industrial minerals which, upon endothermic decomposition over a specific temperature range, will release water and CO₂. This unique chemistry has led to such mixtures being successfully utilized as fire retardants, replacing aluminum hydroxide or Alumina Tri-Hydrate (ATH). Despite the developed marketplace for magnesium-based fire-retardant products, there is little mention of CO₂ mineral carbonation methods, which attempt to recover and convert magnesium from natural seawater or industrial waste into oxides or carbonates as part of the carbon sequestration initiative. The hypothesis to be proven in this work states that if the process of seawater mineral carbonation is prematurely quenched, Mg²⁺ ionic species in seawater adsorbed on the calcite lattice formation will be trapped and therefore recovered in various oxidized forms, such as magnesium oxides, magnesium hydro magnesite, and magnesium carbonate precipitates. A novel method to recover magnesium Mg²⁺ ions from seawater was successfully explored and documented; as such, from an initial concentration of 1250 ppm Mg²⁺ in raw seawater, the average concentration of spent Mg²⁺ ions after the reaction was as low as 20 ppm. A very efficient near-total recovery of Mg²⁺ from the seawater into the solid precipitates was recorded. Subsequently, the process for continuous seawater mineral carbonation for the production of magnesium/brucite/huntite products was successfully proven and optimized to operate with a 30 s reaction time, a dynamic feedstock concentration, [CaO] at 1 gpl in seawater and a room temperature reaction temperature (30 °C), where the average yield of the fire-retardant magnesium-based compounds was 26% of the synthesized precipitates. Approximately 5000 g of the hydro magnesite materials was molded into a fire-retardant brick or concrete wall, which was subjected to an accredited fire performance and durability testing procedure BS476-22:1987. There were encouraging results from the fire resistance testing, where the fire-retardant material passed BS476-22:1987, with performance criteria such as physical integrity failure, the maximum allowable face temperature, and a minimum duration before failure, which was up to 104 min, evaluated. Full article