Trang: 342-356 Pham Minh PhucTóm tắtComposite plates with cracks, variable thickness, and porous structures are increasingly used in modern engineering applications due to their superior performance under complex operating conditions. However, the combined effects of porosity, variable thickness, cracks, and elastic foundation on the free vibration behavior of such plates are still not fully understood. This study investigates the free vibration characteristics of a porous functionally graded plate with parabolically varying thickness along the x-axis. A crack is assumed to be located either at the center or at the edge of the plate. The material porosity is considered to be uniformly distributed through the plate thickness. The governing equations are established based on the first-order shear deformation theory in combination with the phase-field approach to simulate the crack behavior. The finite element method is employed to solve the resulting eigenvalue problem and obtain the natural frequencies of the plate. Parametric studies are carried out to examine the influences of crack length, crack position, porosity coefficient, thickness variation, and elastic foundation stiffness on the vibration response. The numerical results demonstrate that the crack length and crack location have a significant effect on the natural frequencies, while the presence of a stiff elastic foundation remarkably reduces the sensitivity of the vibration characteristics to cracking effects.
Trang: 357-370 Le Kha Quyen, Khuc Thien Thanh, Nguyen Thoi Trung, Nguyen Trang Thao, Vu Ho NamTóm tắtLaminated composite plates are widely used in lightweight structures owing to their high stiffness-to-weight ratio and flexible design capability. However, uncertainties in loads, material properties, and design parameters may significantly affect their mechanical performance and are often not fully addressed in deterministic optimization. This study presents a reliability-based multi-objective optimization framework for the bending design of laminated composite plates under uncertainty. The structural response is evaluated using Isogeometric Analysis combined with the First-order Shear Deformation Theory, allowing geometry and transverse shear deformation to be represented in a unified numerical model. Ply thicknesses are design variables, while maximum transverse deflection and structural mass are minimized as conflicting objectives. The First-order Reliability Method is used to evaluate the reliability index, and the Generalized Differential Evolution 3 algorithm is used to obtain Pareto-optimal solutions. Numerical results show that uncertainties affect the feasible design region and the trade-off between mass, deflection, and reliability. The framework supports reliability-informed design of lightweight composite plate structures.
Trang: 371-384 Hoang Viet Hai, Le Dac Hien, Tran Thi Bich Thao, Bui Thanh TungTóm tắtAccurate prediction of the axial load-carrying capacity of reinforced concrete (RC) columns strengthened with ultra-high-performance concrete (UHPC) jackets is essential for reliable structural design. However, experimental data for UHPC-jacketed RC columns are scarce due to high costs and complex testing procedures, limiting the generalization of data-driven models. This study proposes a Gaussian-based data augmentation framework to enhance the predictive performance of machine learning models for estimating the axial capacity of UHPC-jacketed rectangular RC columns. An experimental database compiled from the literature is statistically analyzed, and Gaussian distribution-based techniques are employed to generate synthetic samples while preserving the statistical characteristics of the original data. Several machine learning models are developed and evaluated, with testing performed exclusively on the original experimental dataset to ensure unbiased generalization assessment. The results show that the best-performing model, CatBoost, exhibits poor generalization when trained solely on experimental data, achieving a test R² of 0.526 with MAE = 328.1 kN, MAPE = 33.5%, and RMSE = 540.9 kN. After Gaussian-based data augmentation, CatBoost performance improves substantially, reaching a test R² of 0.943, with MAE = 145.51 kN, MAPE = 10.5%, and RMSE = 222.1 kN. These results confirm that Gaussian-based data augmentation significantly enhances prediction accuracy, robustness, and generalization. The proposed framework offers a practical solution for mitigating data scarcity and supports reliable design and assessment of UHPC-strengthened RC columns.
Effect of RAP content on the performance of warm mix stone matrix asphalt
Trang: 385-401 Nguyen Ngoc Lan, Pham Thi Thanh Thuy, Tran Hoai Nam, Nguyen Kim Son, Pham Nguyen Huy HoangTóm tắtThe incorporation of reclaimed asphalt pavement (RAP) into warm mix stone matrix asphalt (WSMA) has attracted increasing attention due to its potential to reduce natural resource consumption, energy demand, and environmental impacts associated with asphalt pavement construction. However, the use of RAP in SMA mixtures may significantly influence the balance between rutting resistance and cracking performance because of the stiffening effect of aged binder. Therefore, this study investigates the influence of RAP content on the mechanical performance of WSMA mixtures. Four mixtures containing 0%, 10%, 20%, and 30% RAP were designed using a warm mix additive, a bio-based rejuvenator, and cellulose fiber. The performance of the mixtures was evaluated through IDEAL-RT and IDEAL-CT tests to characterize rutting and cracking resistance, respectively. The results indicated that increasing RAP content significantly improved rutting resistance, as reflected by higher shear strength and RTIndex values. However, the cracking resistance gradually decreased with increasing RAP content due to the increased stiffness and brittleness of the aged binder system. Among the investigated mixtures, the WSMA containing 20% RAP exhibited the most balanced mechanical performance, providing substantial rutting improvement while maintaining acceptable cracking resistance.
Evaluation of creep–recovery behavior of TPS-modified asphalt binders
Trang: 402-415 Tran Danh Hoi, Tran Thi Cam Ha, Nguyen Quang Tuan, Nguyen Ngoc QuangTóm tắtDue to increasing traffic loads and high pavement temperatures, improving the rutting resistance and durability of asphalt pavements has become a critical issue in road engineering. Conventional asphalt binders often show inadequate resistance to permanent deformation under severe loading and temperature conditions. This study investigates the effect of TAFPACK-Super (TPS) modification on the high-temperature performance of asphalt binders using Multiple Stress Creep Recovery test. Tests were conducted at stress levels of 0.1 and 3.2 kPa over temperatures ranging from 52°C to 88°C. Asphalt binders containing different TPS contents (6%, 13.6%, and 18%) were compared with base asphalt and polymer-modified asphalt. Non-recoverable creep compliance (Jnr) and percent recovery were analyzed to evaluate rutting resistance and elastic response. The results show that TPS significantly enhances deformation resistance by reducing Jnr values and increasing recovery rates. Temperature mainly affects Jnr, while TPS dosage strongly influences elastic recovery behavior. Overall, TPS modification improves the rheological properties of asphalt binders by forming a stable polymer network, resulting in lower temperature sensitivity and better long-term pavement performance under heavy traffic conditions.
Analysis of slope stability under dynamic vehicle loads induced by rough flexible pavements
Trang: 416-430 Huynh Van QuanTóm tắtUneven pavement surfaces increase the dynamic loads generated by moving vehicles. However, stability analyses of road embankments often neglect the influence of vehicle vibrations on slope stability. Therefore, considering the interaction between vehicles, pavement conditions, and slope response provides a more realistic evaluation of embankment stability. In this study, vehicle dynamics are simulated using a quarter-car model (QCM), pavement roughness is represented by the International Roughness Index (IRI), and slope stability is evaluated using the Fellenius method. Numerical simulations were conducted for an 8-m-high, 1:1 cut slope in homogeneous saturated cohesive soil under vehicle speeds of 20, 40, and 60 km/h. Four pavement roughness levels with IRI values of 2, 3, 5, and 7 were considered. Dynamic wheel loads for car and truck models were simulated in MATLAB-Simulink over 150 s using the Runge-Kutta integration method. The results show that the static factor of safety (FoS) is 2.05 for the car and 2.03 for the truck. Under dynamic loading with IRI=7, the FoS decreases to 1.96-2.00 for cars and 1.92-1.96 for trucks, depending on vehicle speed. The findings indicate that increasing pavement roughness and vehicle loads reduce slope stability and should be considered in road embankment design and assessment.
Short-term mechanical properties of geopolymer concrete incorporating sea sand
Trang: 431-445 Thuy Chi DangTóm tắtThe depletion of natural river sand and the environmental effect of Portland cement production have motivated the search for green building materials. This study investigates the short-term mechanical properties of geopolymer concrete (GPC) incorporating sea sand as fine aggregate. Class F fly ash and ground granulated blast furnace slag were employed as aluminosilicate precursors, activated by a dry sodium silicate-based powder. Nine mixtures were designed by varying activator content (8%, 11.5%, and 15% by binder mass) and water-to-binder (W/B) ratios (0.30, 0.35, and 0.40). A total of 108 cylindrical specimens were tested for compressive strength at the age of 3, 7, 14, and 28 days. Flexural tensile strength, splitting tensile strength, and elastic modulus were evaluated at 14 days for the optimal mixture. Results indicate rapid early-age strength development, with 3-day strength reaching 50–60% of 28-day strength. Increasing activator content significantly improved compressive strength, while increasing W/B ratio reduced strength. The 28-day compressive strength reached 44.8 MPa under ambient curing. Flexural and splitting tensile strengths exceeded predictions from conventional concrete design models. The findings preliminary demonstrate that sea sand can be effectively utilized in geopolymer concrete providing a sustainable option for construction in coastal regions.
Geometrically nonlinear response of axially functionally graded beams subjected to a moving load
Trang: 446-458 Pham Thi Ba LienTóm tắtUnderstanding the dynamic response of the beam under the actions of a moving load is crucial for practical applications. In this study, nonlinear dynamic characteristics of an axially functionally graded (AFG) beam subjected to a moving load has been performed by using the trigonometric shear deformation beam theory and the von-Kármán geometric nonlinearity. The Voigt model is used to calculate the material properties of the beam. The system of nonlinear differential equation of motion for the beam is derived by using Hamilton’s principle. The finite element formula based on the Lagrange and Hermite interpolation functions is employed to discretize the model and obtain a numerical approximation of the system of differential equation of motion in nonlinear analysis. The Newmark method together with the Newton-Raphson iteration method is adopted to solved these equations. To validate the present work, the results in this paper are compared with those of the existing literature and good agreement is achieved. The results show that the power-law index, velocity and moving load magnitude and aspect ratio play a very important role on the beam’s nonlinear response.
Application of fuzzy logic in collision avoidance control of multiple swarm robots
Trang: 459-470 Le Thi Thuy Nga, Nguyen Manh DungTóm tắtIn nature, many swarms of organisms may encounter one another while moving in search of food, which can lead to conflicts between groups. In the field of transportation, there are flows of unmanned vehicles traveling from different directions on the roads; when they reach intersections, the challenge is how these vehicles can pass one another without collisions and then continue toward their destinations as originally planned. Groups of drones fly in the sky, controlled to form various shapes. So how do these drone swarms move past each other without colliding while forming the desired shape? This paper proposes a solution based on the use of Takagi–Sugeno and Mamdani SISO fuzzy structures to compute internal forces within a swarm, target-directed forces, and forces for avoiding other swarms. The proposals above will be validated through MATLAB simulations under different scenarios involving varying numbers of swarms and different numbers of individuals in each swarm.
Enhancing the operational efficiency of public transport through automated fare collection systems
Trang: 471-484 Nguyen Thi Bich HangTóm tắtPublic transport systems in major urban areas of Vietnam have experienced significant growth in recent years, however, the application of information technology in their management and operation remains limited. In cities such as Hanoi and Ho Chi Minh City, fare collection on bus networks is still predominantly conducted manually, with ticket counting and data recording also performed using traditional methods. This approach not only leads to high labor costs but also reduces efficiency in data management and service planning. These limitations hinder the implementation of advanced operational and policy mechanisms, including integrated fare systems, direct passenger-based subsidy schemes, and data-driven service planning that can adapt to fluctuations in travel demand. This study examines the technical, technological, and socio-economic prerequisites for implementing automated fare collection (AFC) systems in Vietnam. Based on this analysis, it proposes a set of solutions aimed at enhancing the operational efficiency and overall performance of urban public transport through the automation and digitalization of fare collection processes.
Vibration-based damage detection in cable-stayed bridges using a novel 1D-ConvNeXt-LSTM network
Trang: 485-499 Ho Xuan Nam, Vu Manh Trung, Nguyen Nam Son, Nguyen Ngoc LongTóm tắtStructural health monitoring (SHM) plays a crucial role in maintaining the safety and serviceability of civil infrastructure, such as cable-stayed bridges. However, simultaneously extracting detailed local signal features and long-range temporal dependencies from vibration data remains a significant challenge for standalone deep learning architectures like LSTM or ResNet1D. To address this limitation, this study proposes an advanced hybrid architecture, 1D-ConvNeXt-LSTM, for structural damage detection. This framework integrates the multi-scale feature extraction capabilities of 1D-ConvNeXt with the sequential modeling proficiency of Long Short-Term Memory (LSTM) networks. The proposed method was evaluated using vibration time-series data acquired from a scaled cable-stayed bridge model under five distinct simulated damage scenarios. Experimental results demonstrate that the 1D-ConvNeXt-LSTM model achieves superior classification performance, yielding a macro–Area Under the Curve (AUC) of 0.971 and a macro F1-score of 0.814, significantly outperforming baseline architectures including FCN, ResNet1D, and LSTM. Ultimately, the proposed architecture provides a robust, stable, and highly accurate solution for structural condition assessment, thereby enhancing the effectiveness of damage identification in practical SHM applications.
HIT4DAR: Holistic interaction transformer for driver action recognition
Trang: 500-514 Hoang Hiep Bui, Khanh Huyen Bui, Thien Linh Vo, Hong Quan Nguyen, Thuy Binh Nguyen, Thanh Toan Dao, Thi Lan LeTóm tắtTraffic accidents remain a critical issue worldwide, especially in the context of the rapidly growing number of vehicles on the road. This leads to the need for an automatic system to recognize distracted driver actions and provide early warnings to enhance road safety. In fact, driver action recognition (DAR) can be considered as a subfield of human action recognition (HAR). In addition to the common challenges of HAR, DAR must address additional difficulties, including fine-grained and subtle hand movements, self-occlusion, and complex interactions with multiple objects. To overcome these challenges, we leverage Holistic Interaction Transformer (HIT) network, originally designed for HAR, to recognize driver activities from video sequence. The proposed method named HIT4DAR (Holistic Interaction Transformer for Driver Action Recognition). Some experiments are conducted on UTCDriverAct to show the effectiveness of HIT network in DAR task. The overall performance across the six actions of interest achieves a Video-mAP of 47.8%. In particular, the recognition accuracy for Texting activity reaches 78.9%. Furthermore, an ablation study is performed to investigate the influence of pose estimation models on recognition accuracy. The experimental results indicate the trade-off between recognition accuracy and computational efficiency in different pose estimation models. This comprehensive analysis provides useful recommendations for the research community when deploying the proposed framework in real-world DAR systems.
Trang: 515-529 Nguyen Ngoc Long, Vu Manh Trung, Phung Ngoc Hung, Nguyen Dan Le, Nguyen Ngoc LanTóm tắtSurface crack segmentation is a critical task in structural health monitoring (SHM), serving as an early indicator of structural deterioration and safety risks. Recently, deep learning-based computer vision has emerged as a dominant approach for automating defect detection, gradually replacing manual inspections. However, traditional convolutional neural networks (CNNs) often struggle to capture long-range dependencies. To address this limitation, this paper introduces the CSWin-Semantic FPN, a model integrating the transformer architecture with cross-shaped window (CSWin) attention and a semantic feature pyramid network (Semantic FPN) to optimize feature extraction. Notably, this study utilizes a multi-modal fusion dataset-combining optical and thermal infrared images collected in real-world environments. This fusion approach significantly enhances crack signals against complex backgrounds, facilitating more effective model training. Experimental results demonstrate that the CSWin-Semantic FPN achieves an impressive intersection over union (IoU) of 70.53%, significantly outperforming ResUNet (59.44%), SwinUNet (57.91%), and UNet (51.79%). These findings confirm the potential of hybrid Transformer architectures combined with multi-modal data in providing reliable and automated SHM solutions.
Induced inner product structures and Cauchy-Schwarz inequalities for linear functionals
Trang: 530-541 Nguyen Ha TrangTóm tắtLinear functionals on finite-dimensional polynomial spaces generate fundamental algebraic and analytic structures, including moment sequences, moment matrices, and functional inequalities. Associated with a linear functional on polynomials of bounded degree is a moment matrix whose entries are given by the values of the functional on products of monomials and naturally exhibit a Hankel structure. Adopting an intrinsic functional-analytic viewpoint, this paper studies linear functionals on polynomial spaces without invoking any external representation framework. We develop a unified algebraic setting in which linearity, positivity-type conditions, moment matrices, and a functional inequality are examined simultaneously. We distinguish properties arising purely from linearity from those requiring additional structural assumptions. In particular, we establish a Cauchy-type inequality for linear functionals under mild algebraic conditions, independent of any a priori inner product structure. Under stronger positivity assumptions, the linear functional induces an inner product on polynomial spaces, with the associated moment matrix reflecting this structure precisely. Moreover, the Hankel structure of moment matrices is clarified as an intrinsic consequence of polynomial multiplication.
The impact of debt structure on financial performance: evidence from listed transportation firms
Trang: 542-555 Do Thi Hai YenTóm tắtThe transportation sector is a key pillar of economic activity, both supporting broader development and remaining highly responsive to shifts in the macroeconomic environment and the pressures associated with deeper international integration. Examining the relationship between debt structure and financial performance in transportation firms is essential in understanding the challenges and guiding financial management in the context of an emerging economy. This study focuses on analyzing the impact of key indicators related to debt structure, including the ratio of short-term debt to total debt (SDR), the ratio of long-term debt to total debt (LDR), and the total debt to total assets ratio (TDR), on financial performance metrics such as earnings per share (EPS), return on equity, and return on assets. The research data was collected from 99 listed transportation firms between 2019 and 2023 and analyzed using fuzzy-set Qualitative Comparative Analysis. The findings indicate that higher levels of SDR are associated with configurations linked to stronger financial performance, suggesting that the use of short-term debt may be conducive to improved performance in the short run. However, the simultaneous presence of LDR and TDR shows varying impacts, indicating that when the ratio of long-term debt or total debt exceeds a reasonable threshold, it can lead to increased financial costs and risks, ultimately degrading financial performance. Therefore, this study offers practical implications for developing appropriate debt management strategies to ensure sustainable growth and financial stability for Vietnamese listed transportation firms.
Study on intention to switch to electric vehicles in the Low-Emission zone in Hanoi
Trang: 556-570 Hoai An Nguyen, Quang Minh Phung, Huy Hoang Nguyen, Ngoc Bao Pham, Duc Thien Phuoc Pham, Minh Hieu NguyenTóm tắtAir pollution is one of the most critical environmental challenges worldwide, encouraging governments to promote electric motorcycles (EMs) and implement Low-Emission Zones (LEZs) as key instruments for achieving sustainable urban mobility. In Vietnam, especially in large cities such as Hanoi, emerging policies restricting gasoline-powered motorcycles are expected to significantly influence individual travel behavior. This study investigates the factors affecting individuals’ intention to switch from conventional gasoline motorcycles to EMs in Hanoi under the context of these policy changes. The analysis is based on primary survey data collected from 409 respondents. Exploratory Factor Analysis (EFA), multiple regression analysis, and ANOVA are employed to examine the impacts of psychological, socio-demographic, and mobility-related factors on EM adoption intention. The findings reveal that psychological factors play a prominent role, besides socio-demographic characteristics, in shaping switching intention. Perceived value is identified as the strongest positive determinant, followed by environmental concern, while perceived risk negatively influences intention. The results provide valuable insights for policymakers in designing effective measures to promote electric motorcycle adoption and support sustainable transport transitions in urban Vietnam.
Trang: 571-582 Pham Thi Ly, Nguyen Duc Du, Nguyen Thi Hong HoaTóm tắtTraffic flow forecasting is a critical component in intelligent transportation systems, supporting traffic management, reducing congestion, and improving the operational efficiency of urban road networks. However, this is a challenging problem due to the temporal variability of traffic data and the influence of numerous complex factors. In this study, we propose a traffic flow forecasting method based on the CatBoost algorithm to effectively exploit tabular traffic data collected from traffic sensors. The dataset consists of 2,976 records containing temporal information and vehicle counts across four categories (cars, motorcycles, buses, and trucks). In addition to the original features, the study constructs supplementary temporal and time-series features, including Hour, DayOfWeek, IsWeekend, Total_lag1, and Total_roll3, to enhance the model's ability to capture traffic flow variation trends. Based on this, two independent machine learning tasks are established: (i) total traffic flow forecasting as a regression problem, and (ii) traffic condition classification into four levels. Experimental results demonstrate that the proposed model achieves strong predictive performance. Furthermore, feature importance analysis using the SHAP method reveals that vehicle count-related variables, particularly CarCount and BusCount, have a significant impact on prediction outcomes. The study demonstrates that CatBoost is an effective approach for traffic flow forecasting with tabular data and holds strong potential for application in intelligent traffic management systems.
Trang: 583-593 Ngo Duc Chinh, Do Anh Tu, Hoang Thi Tuyet, Do Van Thang, Do Trong Nguyen, Ho Quang HuyTóm tắtEarly-age temperature development of concrete is governed by the balance between hydration heat generation and heat dissipation to the surrounding environment. Adiabatic calorimetry is commonly regarded as the most accurate experimental method for determining hydration-related thermal parameters of concrete; however, it requires complex equipment and is relatively costly. In contrast, semi-adiabatic calorimetry offers a simpler and more economical alternative. This study experimentally investigates the semi-adiabatic temperature development of concrete mixtures with different fly ash replacement levels. Four mixtures containing 0%, 10%, 20%, and 30% fly ash by mass of cementitious materials were tested using a laboratory calorimeter operated under semi-adiabatic mode. Concrete and chamber air temperatures were continuously monitored, and key thermal indicators were evaluated. The results show that increasing fly ash replacement reduces both the peak temperature and the overall temperature rise under consistent testing conditions. The temperature rise (ΔT) decreased from 23.9 °C to 17.5 °C as fly ash replacement increased from 0% to 30%. The reduction in temperature rise does not follow a strictly linear trend, and no clear monotonic relationship was observed for the time to peak temperature. Semi-adiabatic calorimetry is shown to provide reliable comparative indicators for preliminary assessment of early-age thermal behavior of concrete mixtures.
Forced vibration analysis of variable thickness microplate
Trang: 594-606 Dam Vu Son QuyenTóm tắtNowadays, with the development of material science, nano- or microstructures are increasingly of interest in research because of their applications in micro-electromechanical technology, semiconductor chips, or sensors. In this study, the isogeometric approach (IGA) method combining the Mindlin plate hypothesis and the modified couple stress hypothesis is used to analyse the forced vibration of a micro-plate with variable thickness made of materials with variable mechanical characteristics subjected to the effect of different types of dynamic loads. The thickness change of the microplate is considered in two directions with a nonlinear law, while the material characteristics vary with the plate thickness. The model's and method's accuracy are validated by comparing it with results from published studies. Then, the paper surveys the impact of geometric and material coefficient on the transient responses of FG microplate. The research results provide important bases in the design and optimization calculation of micro-electromechanical systems serving the chip and sensor industries.
Dynamic stability analysis of functionally graded plate with variable thickness
Trang: 607-618 Nguyen Thao HoaTóm tắtUnderstanding the dynamic stability behaviour of functionally graded microstructures is of great importance for the development of advanced micro-electromechanical systems, aerospace components, and high-performance smart structures. Accurate prediction of instability regions and vibration characteristics can significantly improve structural reliability, safety, and lightweight design efficiency in modern engineering applications. This study presents an analytical method for analysing the dynamic stability of FG variable thickness microplate based on Mindlin plate theory, modified couple stress theory and the Bolotin method. The microplate thickness is assumed to vary along the length and width with a non-linear variation. The isogeometric analysis method is used to derive the pulse frequency and dynamic stability region of the plate under different boundary conditions. The accuracy of the model and calculation method is verified through numerical comparison with reliable publications. A set of numerical results is collected to evaluate the influence of input parameters; these results are crucial for the optimal calculation and design of variable thickness structures in practice.
