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The Influence of End Effects on the Flow Resistance Characteristics of Variable Diameter Cylinders
Full text linkBased on the study of the flow around finite-length cylinders, an analysis of the flow resistance characteristics of commonly encountered variable diameter cylinders at high Reynolds numbers was conducted. A comprehensive relationship equation for the flow resistance within the subcritical region, the drag crisis region, and the drag recovery region was obtained. Additionally, the influence of end effects on the flow resistance characteristics of finite-length cylinders and variable diameter cylinders was analyzed using large eddy simulation (LES), and a comprehensive formula describing the range of end effect influence was obtained. The results indicate that the flow resistance coefficients at both ends of the variable diameter cylinder are influenced by the aspect ratio λ, Reynolds number (Re), and included angle θ. As θ and λ increase, the distance affected at the top of the cylinder increases. As Re decreases, the affected distances at the top and bottom increase. The comprehensive formula for the influence range can be used to modify the relationship equation for the drag coefficient. These findings have important implications for the study and application of the flow characteristics of finite-length variable diameter cylinders.
Received: 29.05.2024
Received in revised form: 16.07.2025
Accepted: 06.11.202
Experimental analysis of covering layer-prestressed wire rope reinforced bridges
Full text linkWith the application of prestressed steel wire rope in bridge reinforcement project, mortar or composite mortar as the embedded material of steel wire rope is also gradually exposed to low strength, easy to crack, easy to fall off, and affect the durability of the wire rope and other shortcomings. Polyurethane-cement (PUC) composite, as a polymer concrete material, is characterized by light weight, high strength, high toughness, and good adhesion and corrosion resistance. In this paper, two kinds of reinforcement methods, PUC prestressed steel wire rope and prestressed steel wire rope, were used respectively, and the load test before and after reinforcement was carried out, and the effectiveness of the reinforcement methods was verified through the collection of parameter information, such as strain and deflection, before and after reinforcement. Although the PUC-strengthened bridge is less than the mortar-strengthened bridge each piece of girder arranged 15 pre-stressing steel wire rope, but the two bridges strengthened girder stiffness increase amplitude is comparable, under the action of the symmetrical load, the middle girder are increased by 13%, after the reinforcement of the bridge in the measured deflection to meet the highway load standard requirements of class Ⅱ. The PUC overlay layer has a good adhesion with the original beam body, and no cracks were found. However, the mortar overlay layer has cracks of varying degrees. The crack width is 0.15 mm, and the average spacing is approximately 150 mm.
Received: 05.12.2024
Received in revised form: 08.09.2025
Accepted: 06.11.202
Cable-stayed bridge Static performance with different cable damage condition caused by fire
No full textThe stay cable is usually close to the carrieway. Once the fire occurs, it will inevitably cause different degrees of damage to the cable of the bridge. Rapid and accurate mechanical analysis and evaluation of fire-damaged cable-stayed bridges is very important to provide accurate basis for decision makers. Taking Sifang Tai Bridge fire accident as the engineering background, this paper uses damage theory and finite element theory to simulate the fire damage of different cable-stayed cables and different fire damage degrees of the same cable, and analyzes the change characteristics of the static parameters of the main beam and cable force caused by fire damage of the cable-stayed bridge. The results show that the fire damage of back cable and mid-span cable has a global effect on the alignment and cable force of the whole bridge. However, the damage caused by other cable fires is localized, with only the deflection near the self anchored main beam position and the significant influence of 3-4 cable forces nearby. It is similar to the support stiffness change or support failure of multi-point elastic supported continuous beam. The fire induced fusing damage occurred on the outermost back cable, which caused the cable force of the nearby cable not to reach the warning value, but the surplus was very small. The results of the study can provide implications for similar projects.
Received: 8.2.2025
Received in revised form: 24.7.2025
Accepted: 30.8.202
Analysis of the downward deflection parameters before and after external prestressing reinforcement of continuous rigid frame bridges
Full text linkDue to a lack of foresight by designers during bridge planning, outdated specifications that have not been updated in a timely manner, or construction errors during the building process, bridge structures may be overloaded, ultimately leading to excessive deflection in the main span of continuous rigid frame bridges. Therefore, it is urgent to study the causes of downward deflection in continuous rigid frame bridges and explore their reinforcement methods. This paper addresses the issue of severe mid-span deflection in a specific continuous rigid frame bridge and investigates the iMPact of various factors, including internal prestress loss, stiffness reduction, shrinkage and creep, over-excavation (possibly referring to excessive excavation or over-dimensioning in construction), shear deformation, external prestress loss, and overloading, on the downward deflection of continuous rigid frame bridges. The study identifies the most significant factor contributing to this deflection. Upon comprehensive coMParison of all factors, stiffness reduction is found to be the primary cause of mid-span deflection. For reinforced bridges, external prestress loss and overloading are the most critical factors. In calculations for continuous rigid frame bridges, shear deformation cannot be neglected.
Received: 22.05.2025
Received in revised form: 28.06.2025
Accepted: 11.11.202
Study of ozone destruction reaction at higher temperatures
Full text linkThe ozone destruction at higher gas temperatures was studied in a quartz cuvette. The cuvette was heated by a resistance wire wound on the outer surface of the cuvette. The cuvette was filled with ozone and the time dependence of ozone concentration in the cuvette was measured by absorption spectroscopy. The rate constant for ozone decay was derived from this time dependence. The influence of the rate constant on surface condition (the surface concentration of adsorbed oxygen atoms and molecules) was studied. The surface concentration of adsorbed oxygen atoms was changed by reactions with gaseous molecular oxygen just before the cuvette was filled by ozone. The cuvette temperature was set to 40, 50 and 60 ◦C. The measured rate constants increase with increasing temperature from the value 1.27 × 10−4 s−1 to 1.88 × 10−4 s−1. The influence of temperature and cuvette surface coverage on ozone decay constants is discussed
Fractional calculus in describing the viscoelastic response of PVB foil
Full text linkTo address the response of a PVB foil, both traditional and fractional viscoelasticity based formulations are described and compared in this paper. Traditional viscoelasticity uses models consisting of elastic springs and viscous dashpots. Fractional viscoelasticity is based on the principles of fractional calculus (derivatives and integrals of non-integer order) and introduces another rheological element, the springpot, which behaves as viscoelastic on its own and allows us to construct even more complex models. While limiting attention to the Maxwell chain model, both formulations are compared in light of approximation of experimental data provided by rheometer measurements. This is illustrated by plotting the storage modulus derived experimentally as well as computationally, which in turn promotes application of fractional calculus as an efficient tool for smoothing out and storing the experimental data
Characterization of the microstructure of cement paste exposed to gamma radiation by scanning electron microscopy
Full text linkHardened cement paste with a water-cement ratio of 0.4 was examined under five different relative humidity (RH) conditions (11 %, 33 %, 76 %, 96 %, and 100 %). These samples were exposed to gamma radiation with a total dose of 13.82 MGy over 341 days. Scanning electron microscopy (SEM) was the primary tool used for characterizing the samples’ microstructure at a microscale, aided by image analysis (IA), which showed negligible changes in Calcium-Silicate-Hydrate phases but a decrease in Portlandite of 1.5–3.5 % under 33–100 % RH conditions. Point elemental analysis was conducted to determine the (Ca-S)/Si ratio of the inner product, finding a significant increase of up to 20 % at medium RH conditions (33–76 %)
Multi-index evaluation method for grouting repair effect of diseases in expessways based on combined weighting method - cloud model
Full text linkAs a highly practical technique, grouting repair technology is widely used in the practical repair of highway diseases. Existing single indicator detection methods can well reflect certain characteristic indicators of roads, such as compaction and strength. However, the road performance after grouting often needs to be comprehensively evaluated from multiple perspectives, which is difficult to achieve through a single detection method. Therefore, this paper proposes a multi-index evaluation method that comprehensively considers the mechanical properties, uniformity, and compactness of the road after grouting repair. This method combines hierarchical analysis and entropy weight method, integrating subjective evaluation with objective reality, to assign weights to each evaluation index and obtain the weight ranking of relevant influencing factors in the evaluation index system. Based on these index and the combined assign weight method, a comprehensive evaluation model for asphalt pavement is constructed and demonstrated by cloud model step by step. Taking the reconstruction and expansion project of an actual expressway as an example, the grouting effect is evaluated by the proposed model. After that, the actual excavation situation of the expressway show that the evaluation results are closer to the actual performance. The transition from qualitative and empirical evaluation of grouting repair effect to scientific and semi-quantitative evaluation has been initially achieved. The evaluation model for grouting effect based on the combined weighting method-cloud model can accurately, and effectively evaluate the performance of the expressway after grouting repair.
Received: 9.5.2024
Received in revised form: 25.7.2025
Accepted: 30.8.202
The impact of oxygen content on the ablation mechanism of gassing materials under arc action
Full text linkWith the rapid development of Renewable energy, DC power system, Energy Storage System and Rail Transit etc, the demand of high performance Direct Current circuit breakers is increasing significantly. Gassing materials can improve the interruption capability during the arc ignition process, however, the decomposition process and reaction products will be affected by the onsite environment, such as pressure, oxygen concentration and humidity. Using molecular dynamics simulations, the decomposition process of PA66 under an electric field at varying oxygen contents was analyzed. The results show that the introduction of oxygen accelerates the decomposition of PA66, not only promoting hydrogen generation but also suppressing the formation of tar and coke, and provides a preliminary standard for choosing the qualified gassing materials
Developing an effective approach to assess pavement condition for high friction surface treatment (HFST) installation
Full text linkFor more than two decades, High Friction Surfacing Treatments (HFST) have been used worldwide to improve road safety at critical locations, such as sharp curves and intersections. However, the costs associated with HFST installation and the rapid deterioration observed on pavements with poor structural conditions cannot be overlooked. To address these concerns, this research study sought a reliable and accurate method for assessing the suitability of applying HFST to pavements. The main focus was on using machine learning techniques and incorporating International Roughness Index (IRI) and Pavement Condition Index (PCI) data to predict and provide informed recommendations for HFST application. To achieve this, ensemble models were employed, of which the decision tree and extreme gradient boosting showed robust performance, achieving an impressive R-squared value of 0.90, indicating a high level of accuracy in predicting PCI. These models were further assessed for HFST application using the LTPP dataset, with sections classified as suitable and categorised them as good, fair, or poor. The suggestions from these models were particularly reliable in determining the appropriate area for HFST application. The research results clearly demonstrated the efficacy of the ensemble models in accurately predicting PCI and providing informed recommendations for HFST application