Journal of Science and Technique: Section on Special Construction Engineering
Journal of Le Quy Don Technical University
ANALYSIS OF BLAST LOADS ON STRUCTURES WITH FACADE OPENINGS USING UFC 3-340-02
Designing blast-resistant structures with openings presents a significant challenge due to the complex propagation and interaction of shock waves with internal structural components. While international design codes have been established to address this issue, engineering practice in Vietnam primarily relies on empirical methods for assessing external blast loads on simple rectangular geometries, often neglecting internal pressure effects due to a lack of experimental data. As an alternative to computationally intensive CFD simulations, this article presents a comprehensive approach utilizing UFC 3-340-02 to determine blast loads acting on both exterior and interior structural surfaces. An automated calculation method is introduced to estimate the determination of these loads and rapidly generate a robust loading database. This study provides Vietnamese engineers with a practical blast loading assessment tool and a new approach to accurately analyze structural components, thereby enhancing the survivability and resilience of structures against explosive events.
NUMERICAL SIMULATION OF BLAST PRESSURE ON ACCESS BLAST DOOR USING ABAQUS SOFTWARE
This article presents the investigation results of reflected blast pressure acting on access blast doors using a numerical simulation method with Abaqus software. The study employs Sadovskii's empirical formula as the theoretical basis for determining shock wave overpressure. Simulations were conducted with parametric variations including: TNT explosive mass ranging from 50 kg to 200 kg, standoff distance from explosion center to protective door (R₀) from 10m to 25m, and incident angle α between shock wave propagation direction and door surface normal from 0° to 60°, under the assumption that the protective door is perfectly rigid and immobile. Results show that the error between Abaqus simulation and empirical formula ranges from 1.123% to 13.65%, demonstrating high reliability of the simulation method. Reflected pressure decreases with increasing standoff distance R₀ and varies complexly with angle α due to the curved surface characteristics of the protective door. The study confirms that Abaqus software is an effective tool for predicting and analyzing blast pressure on protective door structures, contributing to improved efficiency and safety in the design and construction of access tunnel protective doors in practice. Moreover, the influence of the curvature radius of the door surface on the reflected pressure value is complex. When calculating the load acting on the protective door, it is necessary to consider the average reflected pressure on the curved surface to ensure accurate calculations.
ESTIMATING SHALLOW-WATER BATHYMETRY FROM SENTINEL-2 IMAGERY USING MACHINE LEARNING: A CASE STUDY IN COASTAL AREA OF GIA LAI, VIETNAM
This study investigates the potential of applying machine learning algorithms to estimate shallow-water bathymetry from Sentinel-2 satellite imagery in the coastal waters of Gia Lai province, Vietnam. A Sentinel-2 Level-2A image acquired on January 23, 2020, under clear and stable optical conditions, was used after atmospheric correction. In-situ bathymetric data were collected using a GPS-integrated single-beam echo sounder and employed as training and validation datasets. Five machine learning models, including Multiple Linear Regression (MLR), Random Forest (RF), Decision Tree (DT), K-Nearest Neighbors (KNN), and Long Short-Term Memory (LSTM), were developed and compared for bathymetric estimation accuracy. The results indicate that the coefficient of determination (R²) ranges from 0.80 to 0.91, with Root Mean Square Error (RMSE) values between 0.72 m and 1.05 m, and Mean Absolute Error (MAE) values ranging from 0.49 m to 0.72 m. These findings demonstrate the feasibility of integrating Sentinel-2 imagery with machine learning for accurate shallow-water bathymetric mapping. Furthermore, the proposed approach shows strong potential for application to other coastal regions of Vietnam with comparable environmental and optical characteristics.
BALANCING COMPOSITE MOTION OPTIMIZATION FOR CONSTRUCTION SITE FACILITY LAYOUT PROBLEMS
The arrangement of construction facilities on the construction site is one of the important problems of construction organization, but at the same time it represents a complex combinatorial optimization problem. Metaheuristic methods are recognized as powerful and effective tools in solving such problems. The Balancing Composite Motion Optimization (BCMO) algorithm is a recently proposed metaheuristic algorithm. This article introduces the results of establishing a problem model and applying the BCMO algorithm with discrete variables receiving integer values to solve the problem of arranging service facilities on the construction site based on a static model. A numerical experiment with three static problem cases selected from the sample problems is conducted. The obtained layout options are compared with the results from other algorithms, thereby demonstrating the proposed algorithm's advantages: its ease of implementation, capability to search for and identify multiple good solutions, and fast convergence speed. The numerical experiment also shows the need for further experimentation and exploration to enhance the algorithm.
NUMERICAL ANALYSIS OF THE EFFECTS OF DIFFERENT BEHAVIOR MODELS OF ISOLATORS ON THE SEISMIC RESPONSES OF MULTI-STORY BUILDINGS
Seismic base isolation (SBI) is widely recognized as a highly effective solution for earthquake-resistant design, extensively implemented in high-seismicity regions, and increasingly adopted in areas with moderate seismic activity. While structural analysis software provides various behavior models to simulate SBI elements, the suitability of these models for specific analytical applications remains unclear. This study conducts a numerical analysis to assess the impact of different isolator behavior models - including equivalent linear, plastic Wen, bilinear, and rubber isolators - on the seismic response of isolated buildings. Nonlinear time-history analyses are performed on a typical seismically isolated building using the 1994 Northridge earthquake record, scaled to match the target spectrum. The seismic isolators are modeled using link elements with constitutive parameters corresponding to the selected models. Key response parameters, such as isolator behavior, lateral displacements, and base shear forces, are analyzed to compare the structural performance across different isolator models. The results indicate that nonlinear models (plastic Wen, bilinear, and rubber) yield comparable and realistic seismic responses, whereas the linear model significantly overestimates displacements and forces. These findings highlight the limitations of linear assumptions in seismic analysis and underscore the necessity of employing nonlinear models for a more accurate evaluation of structural behavior during earthquakes.
REVIEW OF KEY CRITERIA FOR SUSTAINABLE BUILDING MATERIALS
Over the past decade, sustainable building materials (SBM) have increasingly been gained the interests from construction industries, leading to numerous studies that have been conducted to find out the criteria for evaluating the effectiveness and sustainability of such kinds of materials. Despite this growing interest, a systematic review of the key sustainability criteria used to select building materials, which is crucial for guiding future research and practical applications, is possibly still lacking. Thus, this article presents a literature review on sustainability criteria for building material selections for engineering designs and practices. This study employed a systematic literature review (SLR) method, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data were extracted from the Scopus database, comprising 27 impactful peer-reviewed publications related to the selection of SBM criteria from 2015 to 2024. The review identified and synthesized four key criteria: environmental, economic, social, and technical. A model framework was also developed to understand these sustainability criteria better. The findings could enhance the understanding of critical sustainability considerations, assisting industry practitioners, policymakers, and sustainability-focused institutions in formulating more informed guidelines and strategies for sustainable material selection. Furthermore, the checklist and model framework presented in this article may offer valuable resources for researchers conducting further empirical studies in sustainable construction.
A SOLUTION TO IMPROVE LOCATION DATA ACCURACY FOR MAP-UPDATING FROM MOBILE DEVICES USING THE KALMAN FILTER
With the increasing prevalence of mobile devices, it is possible to continuously collect geospatial data directly in the field such as image data and coordinates of objects. However, location data collected from mobile devices often contains noise and large errors, thus direct integration into spatial database poses challenges in terms of accuracy. In the context of the continuous expansion and infrastructure changes of industrial parks in Vietnam, the application of GPS-integrated GIS technology enables automatic and accurate updates of internal road maps within the parks. This article proposes a framework for optimizing point-based data used to update digital maps from mobile devices. The article uses the Kalman filter as a solution to improve the location data accuracy when updating maps from mobile devices. Experimental programming of mobile devices utilizes the Flutter and MapLibre GL libraries, while the desktop program employs QGIS software. The database management systems used are PostgreSQL and PostGIS/GeoServer. Experiments on updating data on real mobile devices demonstrate that the proposed method can effectively limit location errors and minimize the risks associated with anomalous data. By applying the proposed method, the positioning error has been reduced from approximately 8.23 meters to only 3.11 meters. The experimental results also show significant improvements in coordinates accuracy, data deduplication, and map-updating efficiency.
EQUIVALENT ELASTIC MODULI FOR BRICK MASONRY: A COMPARATIVE STUDY OF PERIODIC HOMOGENIZATION APPROACHES
The mechanical characterisation of masonry remains a central challenge in structural analysis due to its heterogeneous composition of bricks and mortar joints. This study conducts a comprehensive comparative assessment of four approaches for determining the equivalent elastic properties of masonry: finite element modelling (FEM), the two-step homogenization method, the one-step Fourier-based scheme, and the interface-joint model. FEM simulations of a two-dimensional brick–mortar assemblage with varying mortar thicknesses serve as the benchmark. Analytical predictions are compared with FEM results for longitudinal and transverse Young's moduli, shear modulus, and Poisson’s ratio. The two-step method achieves excellent agreement with FEM, with errors typically below 3% across all parameters. In contrast, the one-step method consistently overestimates transverse and shear stiffnesses by up to 50-60%, while the interface approach underestimates them by 20-55%. These deviations grow with mortar thickness, reflecting the different modelling assumptions. Overall, the FEM results are bounded by the stiffer predictions of the one-step method and the more compliant interface model, while the two-step method aligns most closely with the reference values. The study concludes that the two-step scheme is most suitable for engineering design, while the interface model is valuable for nonlinear mortar analyses.
AN APPLICATION OF ANALYTICAL METHOD FOR EVALUATING THE STRESS-STRAIN STATE OF DEEP LINED CIRCULAR TUNNELS IN DRY ANISOTROPIC ROCK CONSIDERING ROCK-LINING INTERACTION AND CONSTRUCTION STAGES
In the context of Vietnam's strategic orientation toward developing nuclear energy, the disposal of high-level radioactive waste (HLW) from nuclear power plants is a pressing issue that must be addressed. The long-term storage of HLW in deep geological repositories is a solution being researched and applied in many developed countries, wherein deep tunnels constitute a fundamental component of this system. Circular cross-section tunnels at depth are also widely used for road and high-speed railway tunnels through mountains. Currently, studies on deep tunnels, where the rock strata often exhibit anisotropic properties, are rarely mentioned and investigated in Vietnam. This article aims to present an analytical method for evaluating the stress-strain state of a deep, lined circular tunnel in a dry, anisotropic rock mass, considering the rock-liner interaction under two conditions: perfect bonding and relative slip. Additionally, the influence of the tunnel face advance on the stress-strain state of the tunnel is taken into account based on the well-known convergence-confinement method. The analytical solution for the interaction problem is developed using the complex potential approach with the conformal mapping technique and the theory of thin elastic cylindrical shells. The derived analytical solution is verified against available solutions for several special cases. Based on the obtained solution, parametric studies of the anisotropic rock mass are conducted to assess their influence on the liner's response. This analytical solution can serve as a rapid analysis tool for the preliminary design of deep tunnels in anisotropic rock.
EXPERIMENTAL STUDY ON STRENGTH DEVELOPMENT AND ADIABATIC TEMPERATURE OF HIGH-STRENGTH CONCRETE FOR BRIDGE PIERS
This article presents the design and experimental evaluation of a high-strength concrete mix for bridge pier applications, targeting a compressive strength of 50 MPa. The mix composition was designed according to ACI 211.1-91, incorporating cement, fly ash, blast furnace slag, superplasticizer, and a temperature rise inhibitor. The selected mix achieved a laboratory design strength of 60 MPa. Strength development tests were conducted on cubic and cylindrical specimens at 3, 7, 28, and 56 days. Results showed a compressive strength increase from 35.2 MPa at 3 days to 64.2 MPa at 56 days, while splitting tensile strength improved from 3.12 MPa to 5.19 MPa within the same period. The elastic modulus calculated according to CEB-FIP Model Code 2010, reached 40.47 GPa at 56 days. In addition, an adiabatic calorimeter was designed and improved to monitor the temperature rise of the concrete. Measurements revealed a maximum adiabatic temperature of 76.6°C, corresponding to a temperature rise of 52°C, with the most rapid increase occurring between 8 and 32 hours after casting. The study results provide the necessary data to evaluate the thermal behavior and minimize the risk of thermal cracking in large concrete structures such as bridge piers.
COMPARATIVE INVESTIGATION OF THE COMPRESSIVE STRENGTH OF STEEL FIBER REINFORCED CONCRETE UNDER STATIC AND IMPACT LOADS
This study examines the effect of steel fiber content on compressive behavior of concrete under static and impact loading. The results indicate that increasing fiber dosage reduces workability: the mixture with 0.5% fibers reached the highest flowability (245 mm), while higher contents of (1.0-2.0)% progressively decreased it to 195 mm. This reduction is attributed to greater interparticle friction, the disruption of the granular framework, and fiber orientation resisting flow. Compressive strength under static loading exhibited only slight variation (176.97-179.87) MPa, suggesting limited influence of fibers on quasi-static strength. In contrast, impact loading significantly increased the compressive strength (189.54-194.06) MPa and the strain capacity, with corresponding DIF values of approximately 2.7. A fiber content of 1.5% (MT15) provided the best balance between strength and ductility, whereas 2.0% (MT20) produced the highest toughness but was affected by fiber clustering and stress concentration. Dynamic analysis further confirmed consistent improvements in compressive strength (7-8)% across all dosages, while toughness more than doubled under impact conditions, reaching 1.258 MJ/m³ for MT20. These improvements were governed by crack-bridging and fiber pull-out mechanisms, which delayed crack propagation and enhanced energy absorption. An optimal fiber dosage of 1.5% is recommended to balance workability, strength, and toughness in practical applications.
NUMERICAL SIMULATION OF STRESS AND DISPLACEMENT BEHAVIOR OF TRC-STRENGTHENED FRP-REINFORCED CORAL CONCRETE PANELS UNDER BLAST LOADING
This article presents a numerical simulation of the stress and displacement responses of coral aggregate concrete (CAC) slabs reinforced with glass fibre-reinforced polymer (GFRP) bars and externally strengthened with textile-reinforced concrete (TRC) under blast loading conditions. The panel consists of a B22.5-grade coral concrete core (equivalent to C35/45), combined with a surface TRC layer composed of a Sigratex Grid 350 carbon textile embedded in high-strength fine-grained concrete (grade M600). The integration of GFRP, TRC, and CAC offers advantages in terms of corrosion resistance, utilisation of locally available marine aggregates, and enhanced dynamic load resistance, making it a promising solution for coastal and island infrastructure subjected to blast effects. The simulation results demonstrate that the inclusion of the TRC layer significantly reduces both stress concentration and peak displacement at the panel’s centre. Moreover, it contributes to the confinement of localised damage zones caused by the propagation of blast-induced shock waves. This study provides valuable insights into the potential application of TRC-strengthened CAC structures in marine, military, and defence-related constructions.
IDENTIFICATION OF DAMAGE LOCATIONS IN STEEL BEAMS BASED ON CHANGES IN NATURAL FREQUENCIES
When damage occurs in a structure, it results in changes to its dynamic characteristics including natural frequencies, mode shapes, and damping ratios, compared to an undamaged structure. Based on this principle, several methods have been researched and applied to identify damaged regions in structures. In this article, a cantilever steel beam with constant cross-section is studied by dividing it into regions, where each region is classified based on the first four normalized natural frequencies. The damaged region is identified by classifying the normalized frequencies of the structure through the ratio of the natural frequency of the damaged beam to that of the undamaged beam. A simulation is conducted using SAP2000 for both the intact and damaged cantilever beam to determine its natural frequencies, serving as a basis for identifying the damage location and severity. The identified damage region matches the assumed location and is independent of damage severity. The research results demonstrate that changes in natural frequencies can be utilized to identify damage on cantilever beam structures, providing a basis for the application in detecting damage locations in more complex structures and real-world constructions.
CHALLENGES IN ENGINEERING GEOLOGICAL MAPPING AT LARGE SCALES 1:2000 FOR SUBMERGED CORAL ISLANDS
This article presents a methodology for creating large-scale engineering geological maps (1:2000) for submerged coral islands in Vietnam’s maritime zones, in accordance with the national standard TCVN 9156:2012. The primary objective is to provide a comprehensive representation of key geological and environmental factors, particularly coral sediments that influence land use planning, construction design, and implementation. As there are currently no specific national standards for engineering geological mapping in coral-based island areas, this study references various related standards and documents. It also highlights significant issues that need to be addressed when conducting large-scale engineering geological mapping in submerged coral environments. The results demonstrate that large-scale engineering geological mapping is of considerable scientific and practical value for construction planning, resource management, and natural disaster mitigation. The article also recommends further research to enhance mapping accuracy and the development of appropriate technical standards. Future directions emphasize the integration of modern technologies, such as GIS-based digital mapping, 3D geological modeling, and virtual reality (VR) applications, to simulate geological conditions and assess geohazards in marine island environments. These advancements aim to address challenges posed by climate change and promote sustainable development.
STRUCTURAL RESPONSE OF BAILEY BRIDGE SPANS UNDER MOVING VEHICLE LOADS
Bailey truss bridges are commonly used as temporary structures in emergency traffic situations, such as rescue operations and the repair of aging bridges. Studying the impact of load velocity on bridge structures is essential for determining appropriate operational conditions. This article examines the effect of vehicle speed on the internal forces of truss members and the deflection of the bridge span. The study employs the finite element method using SAP2000 software, the moving load model has an axial load diagram of the real truck. The results indicate that vehicle velocity has a minimal impact on the internal forces of the truss members and the deflection of the bridge spans. Based on these findings, suitable vehicle velocity regulations can be established to optimize traffic flow across the bridge when necessary.
DAMAGE IDENTIFICATION IN BEAM-LIKE STRUCTURE USING RELATIVE NATURAL FREQUENCY SHIFTS
Vibration-based damage identification methods have demonstrated significant potential for structural health monitoring. Modal parameters, including natural frequencies and mode shapes, serve as global indicators of a structure’s condition. Changes in these parameters can be indicative of damage within the structure. This article proposes an enhanced methodology for damage detection through shifts in natural frequencies. By precisely determining the frequencies of both the intact and damaged structure, frequency shifts can be computed, thereby transforming the damage detection process into a minimization of error in the identification task. This approach involves comparing the measured frequency variations with analytical values, which characterizes the frequency shifts resulting from damage. The effectiveness of the proposed procedure is validated through numerical simulations, followed by experimental testing.
STATISTICAL MODELING OF UNIT SKIN FRICTION BETWEEN PILES AND CORAL GRAVELLY SAND USING IN-SITU SPT DATA
This paper presents a statistical analysis of unit skin friction between piles and coral sand layers, based on 245 in-situ Standard Penetration Test (SPT) records collected from a coral reef area. The unit skin friction was estimated using Meyerhof’s empirical correlation. Field data were used to assess the statistical characteristics of the pile-soil interface in coral sand. The results reveal that the distribution of unit skin friction does not follow a single normal (Gaussian) distribution, as is typical for terrestrial granular soils, but instead indicating the presence of multiple distinct geotechnical regimes. This distinctive feature reflects the unique interaction mechanism between piles and calcareous soil, which should be carefully considered in the foundation design of coastal and island structures.
CRACK WIDTH CONTROL IN THE DESIGN OF REINFORCED CONCRETE BEAMS IN MARINE ENVIRONMENTS
Reinforced concrete beams are extensively used in construction, and understanding crack development is essential to ensure the safety and durability of structures, particularly in marine environments. This study investigates the influence of tensile steel reinforcements on crack width in reinforced concrete beams through analytical calculations. The objective is to evaluate crack width behavior under varying amounts and configurations of reinforcement, providing recommendations for optimal load-carrying steel arrangements to limit crack width. The research methodology involves numerical simulations using ETABS and adheres to the design guidelines specified in TCVN 5574:2018, IS 456:2000, and TCVN 9346:2012. The results show that both the quantity and arrangement of tensile reinforcement significantly affect crack formation and width. Notably, the study reveals that meeting both structural strength and crack width requirements for reinforced concrete beams in marine structures is challenging. Ensuring a maximum crack width of 0.05 mm under harsh environmental conditions, such as tidal seawater exposure, poses significant difficulties. These findings offer valuable insights for engineers in designing marine concrete structures and optimizing reinforcement layouts to meet performance and durability criteria under aggressive exposure conditions.
BUILDING SOFTWARE FOR ANALYZING MUCK PILES AFTER BLASTING IN LABORATORY CONDITIONS WITH INTEGRATED ARTIFICIAL INTELLIGENCE
In the mining and tunneling industry, the mean particle size (Dtb) of a muck pile after blasting is a key parameter for evaluating blasting efficiency. Numerous solutions exist for determining mean particle size by photographing muck piles after blasting using commercial software such as Split-Desktop and WipFrag, but these incur annual costs of thousands of US dollars. To address this limitation, the study develops software that analyzes images of muck piles after blasting, providing Swebrec, Gate-Gaudin-Schumann, and Rosin-Rammler particle size distribution (PSD) functions and their corresponding mean particle sizes. The software utilizes open-source resources and integrates the SAM2 artificial intelligence model to facilitate editing of each rock fragment detected in the image. The software’s mean particle size results are compared with those from traditional sieving analysis, with differences ranging from 5% to 7% for image segmentation data. These results demonstrate the software’s feasibility as a low-cost, reliable alternative to the sieving process.
AUTOMATED BUILDING OBJECT SEGMENTATION FROM UAV ORTHOGRAPHIC IMAGERY USING DEEP LEARNING AND GIS TECHNIQUES
This paper presents an automated model for segmenting building objects in orthographic images captured by unmanned aerial vehicles (UAVs) using deep learning and GIS techniques. The proposed method consists of two phases: Phase 1 employs a two-stage deep learning method (named YOLO-SAM) that uses YOLOv11 for coarse building segmentation, followed by the SAM2 (Segment Anything Model) algorithm to refine and enhance the results. Phase 2 further processes this shapefile using a series of geometry-based post-processing techniques, including the Douglas-Peucker algorithm for boundary simplification and curve smoothing to optimize the overall shape. The approach achieves high segmentation accuracy (~mAP of 0.75) and provides a scalable, practical solution for mapping in Vietnam. Unlike previous methods, this approach stands out by combining YOLOv11 and SAM2 for accurate, detail-rich segmentation, and by integrating this with GIS-based post-processing in a unified, efficient pipeline.
EXPERIMENTAL EVALUATION OF NOISE REDUCTION EFFECTIVENESS OF SOUNDPROOFING PANEL SYSTEM
Measures to mitigate aviation noise at airports are increasingly critical, particularly for those near urban areas, requiring studies of effective noise reduction strategies. This article presents an experimental study evaluating and comparing the soundproofing efficiency of a 3 cm thick panel system made from different material combinations, including acoustic sonic felt, plywood, and black rubber. The study focuses on single-source noise with intensity levels equivalent to aircraft engine noise, measured at the noise measurement points recommended by ICAO. Through the shielding panel system, the noise level generated by the electrical blasting machine decreases linearly with the power of the noise source. The findings indicate that noise levels decrease proportionally as the power of the noise source is reduced. Among the tested configurations, the wood-felt-wood combination exhibited the highest sound insulation efficiency, reducing sound intensity levels by 9.48-7.58 dB, compared to 5.85-5.08 dB for the felt-wood-felt system and 5.42-3.14 dB for the uniform felt and black rubber system of the same thickness. These results provide an initial foundation for proposing effective soundproof panel combinations to mitigate both traffic and aviation noise.
SEISMIC PERFORMANCE OF SUPERELASTIC BRACING SYSTEMS APPLIED TO STEEL FRAME STRUCTURES
Bracing systems have emerged as an effective solution for enhancing the resilience of steel frame structures under dynamic loads. Conventional steel bracings dissipate energy through bilinear hysteresis responses, ensuring structural safety but often resulting in significant residual displacements after strong earthquake impacts that necessitate costly maintenance and repairs. Shape memory alloys (SMAs), particularly superelastic alloys, have drawn interest due to their potential for both energy dissipation and self-centering capabilities. This study explores the use of SMA-based superelastic bracing systems in steel frame structures subject to seismic loading. Using nonlinear time-history analyses performed in ETABS, the study investigates the comparative response of conventional and superelastic bracing systems. The findings of this research suggest that SMA-based bracing systems may offer advantages in reducing column demands and residual displacements, indicating potential for further development in seismic design applications.
STABILITY MECHANISM OF MASONRY SEMI-CIRCULAR ARCHES
Masonry arches are ancient structures, applied from tunnel works to complex constructions such as churches, temples, and castles, bearing the aesthetic and unique style of each civilization across various periods. A masonry arch consists of a series of blocks of a specific size stacked atop one another to create an upward curve that can maintain its shape and stability through the interaction of forces among the blocks within the structure. This research elucidates the principles and stability mechanisms of masonry arches in the case of support displacements. Focus on investigating the influence of structural thickness on the stability of masonry semi-circular arches. Simultaneously, it assesses the influence of the surrounding soil on the stability of the structural system. From there, determine the minimum structural thickness to ensure stability under different working conditions of masonry semi-circular arches.
EXPERIMENTAL RESEARCH ON THE PROPAGATION PARAMETERS OF EXPLOSIVE STRESS WAVE IN CORAL CONCRETE
This study investigates the propagation of stress waves in coral concrete material under explosive conditions. The experimental system was designed to analyze the stress wave characteristics in coral concrete, focusing on the velocity and attenuation of the stress waves as they pass through the material. The study used explosive charges placed at specific depths within boreholes to generate the stress waves, with pressure sensors deployed to record the intensity of the waves at different distances from the center of the explosion. The results obtained are the stress wave intensity over time at different distances from the center of the explosion. Using regression analysis, the propagation velocity of the stress waves was determined, and the attenuation coefficient was calculated based on distance. It was found that the blast-induced stress wave attenuation coefficient in coral concrete with a compressive strength class equivalent to B22.5 is 1.272, while the propagation velocity of the blast-induced stress wave ranges between 3658 m/s and 3817 m/s, with a minimal measurement error of 1.18%. These findings provide valuable insights into the dynamic behavior of coral concrete, contributing to the establishment of formulas for calculating stress wave intensity and blast loading in coral concrete.
EVALUATION OF SOIL LOSS ACROSS LAND USE TYPES IN NORTHERN VIETNAM, A CASE STUDY OF TAY CON LINH MOUNTAIN
Deforestation and farming offer two of the most serious risks to soil erosion (SER), water degradation, and desertification... Based on the Universal Soil Loss Equation (USLE) proposed by Wischmeier and Smith, the paper aims to use Geographic Information Systems (GIS) to evaluate the risk of SER in the Tay Con Linh mountain area in Vietnam. Maps of the environmental parameters and the resulting erosion risk were also proposed. The study has discovered that the kind of vegetation in the area was the primary factor in SER. It was concerned with farming methods relevant to steep topography. Studies have demonstrated that the vegetation type in this region is a key determinant of severe erosion. To validate the methodology, Google Earth images of locations identified as prone to erosion were analyzed based on strict criteria. The model demonstrated an efficiency rate of 88.5%. According to the Vietnamese standard TCVN 5299:2009, the levels of erosion in the study area are quite complex but classified as medium risk, with many regions exhibiting R-I level conditions (93.51% soil loss of 10 tons per hectare per year). The study established correlations between the degree of erosion and the amount of vegetation cover, emphasizing the impact of land use on soil erosion rates. This assessment of soil erosion not only aids land users in making informed decisions regarding land use and ecosystem conservation but also provides scientific criteria that complement traditional farmers' knowledge.
EVALUATING HUMAN TOLERANCE UNDER THE EFFECT OF SHOCK WAVE PRESSURE FROM SURFACE EXPLOSIONS
Protecting individuals and structures from the effects of blast loading is a critical challenge when calculating and designing defensive structures. Shock waves, fragments, and the acceleration of structures caused by explosions will cause lethal damage to humans, equipment, and structures. To ensure safety, studies and standards in Vietnam for calculating safe distances for construction and humans in mining operations and defence structure constructions have been implemented. However, detailed studies on the impact of blast wave pressure on humans, depending on the position, the posture of the victims, the direction of the blast loading, and varying degrees of impact due to weight, have not been specifically researched. Hence, this article will introduce and use UFC 3-340-02, "Structures to resist the effects of accidental explosions", to develop a procedure for assessing the safe distances for humans affected by the pressure of ground blast loading. The result can be applied to automatically estimate the survival probability of humans under the impact of blast loading on the ground.
WAVE REDUCTION ABILITY PASSING OVER SUBMERGED BREAKWATER USING POROUS CONCRETE BY FLOW-3D SOFTWARE
This paper presents the results of a study on the wave height reduction efficiency of submerged breakwaters constructed from porous concrete structures (PCSB), using FLOW-3D software. The simulations were conducted on a model with dimensions of 45 m (length) × 1.0 m (width) × 1.5 m (height) and included four groups of scenarios: variations in porosity, the freeboard to incident wave height ratio (S/H), the crest width to wave length ratio (B/L), and the slope of the structure. The simulation results were calibrated against experimental data from different cross-sections, demonstrating strong compatibility. This study clarifies the mechanisms of wave propagation and absorption as they pass over PCSB. When properly designed, the wave reduction efficiency of PCSB is quantified by the coefficient of transmitted wave height to incident wave height, illustrating the practical applicability of these structures. The FLOW-3D software employed in this research serves as an effective tool for analyzing wave deformation over PCSB, significantly contributing to the design of these structures as effective coastal protection measures.
EXPERIMENT TO EVALUATE THE EFFECTIVENESS OF THERMAL REFLECTIVE COATING APPLIED TO CONSTRUCTIONS
Constructions are usually made of materials like reinforced concrete and steel. In hot weather conditions, the reflected thermal radiance in the daytime and the emitted thermal radiance of human activities inside the structure are significantly higher than in the background. Thanks to the temperature difference between them, thermal imaging systems can easily detect or recognize the target. In order to reduce the thermal contrast, it is vital to research and apply the specific coating that can be used to cover the construction and the outside door. On the other hand, there is yet to be a method to evaluate the effectiveness of thermal reflective coating for constructions and mobile targets in Vietnam. Hence, the article has focused on performing the experimental measurement of the thermal difference between two coating materials. The result will also be applied to evaluate and select the effective thermal paint for the protected system.
ON THE USE OF THE GENERAL BANDWIDTH METHOD TO IDENTIFY DAMPING IN MDOF SYSTEMS
The general bandwidth (GeB) method is one of the methods used for viscous damping identification of structures. In this method, approximate and exact formulas have been studied to estimate the damping ratio from frequency response function (FRF) of the single degree-of-freedom (SDOF) system. However, the applicability of these formulas to estimate the damping in multi degree-of-freedom (MDOF) systems has not been analyzed in detail. This article studies the influence of modal parameters on the accuracy of the GeB method used to identify the viscous damping ratios in MDOF systems. The results compared with the formulas based on the half-power bandwidth (HPB) method show that the GeB method has good efficiency and wide identification range.
DEVELOPING SPECIALIZED SOFTWARE FOR PROGRESSIVE COLLAPSE ANALYSIS OF PLANE FRAME STRUCTURES USING THE PLASTIC DAMAGE INDEX
In this study, the authors developed software named Sonar to analyze the progressive collapse of structural elements. This software is capable of assessing the level of damage to each structural component and automatically updating the structural model for subsequent analyses. The software features a user-friendly interface, intuitive graphics, easy input of parameters, and presents computational results in 2D graphics. Through the use of the developed software, damaged structures were analyzed and studied to conclude that considering the progressive collapse of elements based on the plastic damage index serves as a basis for investigating specific design problems to propose more optimal design solutions.