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Evaluation of Strength Characteristics of Cement-Stabilized Rammed-Earth Material
Get PDFThe traditional method of rammed-earth construction is seeing a resurgence because of its minimal environmental impact and sustainability. Numerous elements, including soil composition, compaction procedure, stabilization methods, moisture content, and ambient conditions, affect the properties of rammed-earth materials. This research work aims to investigate the strength characteristics of cement-stabilized rammed-earth material. The strength characteristics involve compressive strength and splitting tensile strength. There are four soil types involved in the casting of cement-stabilized rammed-earth, i.e., 0C100S, 10C90S, 20C80S, and 30C70S. The moisture contents used are based on the OMC of Thar Desert sand, i.e., 11.5%, 12.5%, and 13.5%. While the cement contents used are, i.e., 5%, 10%, and 15%. The number of specimens cast is equal to 216. The results of compressive strength and splitting tensile strength tests conclude that strength increases with the increase in cement content; however, the increase in moisture content decreases the magnitude of compressive strength and splitting tensile strength. The increase in clay content up to 20% increases the compressive strength; a further increase in clay content, i.e., 30%, results in a reduction of compressive strength. The splitting tensile strength increases with the increase in clay content. The maximum compressive strength equal to 13.43 MPa is achieved in the specimen, i.e., 20C80S15c, with minimum moisture content used, i.e., OMC-1% (or 11.50%). While the maximum splitting tensile strength achieved is 6.68 MPa of the specimen, i.e., 30C70S15c, with a moisture content of 11.50%
Assessment of Soil Shear Strength Parameters: Insights from Direct Shear and Direct Simple Shear Testing
No full textThe direct shear test is widely used to determine shear strength parameters ( ) of soil. However, its validity has been questioned due to several issues, such as uneven stress distribution, the creation of a predetermined failure plane, lateral constraints, difficulties in controlling drainage conditions, and limitations in measuring pore water pressure, which is essential for understanding soil behaviour under different conditions over time. This study addresses these concerns by comparing the shear strength parameters obtained from a direct shear test (DST) and a direct, simple shear test (DSST). To further explore these issues, a fully automated universal shear device was used to perform shear tests on clay, sand, and composite soil (clay + sand), covering both consolidated and shear phases of DST and DSST. Specimens were fabricated at their optimal moisture content, and the composite soil was developed by mixing clay with sand in proportions of 10%, 25%, 50%, and 75% of the mass of sand. This research aims to clarify the relationship between these two testing methodologies through comprehensive testing and to enhance the knowledge of the principal mechanism of the 2 tests. The findings revealed that the DST yielded higher shear strength values than the DSST results. It was also observed that the friction angle of sand specimens generally decreased with the addition of clay for both tests. Additionally, the the kaolinite soil in DST and DSST, decreased in the sand as the clay contents increased
Numerical Assessment of Inter-Pillar Stability in Inclined Ore Bodies for Underground Mining Design
No full textThis paper presents a methodology for assessing the stability of stoping chambers and inter-chamber pillars (ICPs) during underground mining of ore bodies with varying dip angles. The objective is to determine optimal parameters for excavation elements (chamber width and pillar spacing) that ensure the stability of the mining system under fractured rock mass conditions. The Zhezkazgan deposit’s geomechanical properties were used as the modeling case study. The methodology includes geotechnical core mapping (with RQD, Q-system, and GSI classifications), laboratory strength testing, field–laboratory correlation, and numerical modeling using the finite element method. Particular focus is placed on the sensitivity of stability to variations in GSI, depth, and excavation geometry. The results indicate that increasing the dip angle significantly reduces the stability of both chambers and pillars. The novelty of this study lies in the comprehensive assessment of structural factors and excavation geometry on mass stability under site-specific geological conditions
Seismic Response Analysis of Buckling-Restrained Brace Frames Considering Brace Performance Degradation
No full textTo elucidate the degradation mechanisms of the hysteretic behavior of buckling-restrained braces (BRBs) in hot–humid service environments and their implications for structural seismic performance, this study tested six BRBs of identical specifications under different numbers of hygrothermal cycles (0, 24, 48, 72, 96, and 120), combining alternating high–low temperature hygrothermal exposure with subsequent quasi-static cyclic loading. The evolution of hysteretic performance parameters with cycle count was quantified. Test results indicate that hygrothermal cycling induces corrosion of the steel core and deterioration of the unbonded material, weakening interfacial bond strength and increasing axial friction effects; consequently, the tensile yield load, elastic stiffness, and ultimate tensile capacity decrease. Based on the experimental observations, a modified Bouc–Wen model was employed to simulate BRB hysteretic nonlinearity, and the identified parameter evolution closely reproduced the measured trends. The degradation model was further incorporated into time-history analyses to assess the influence of BRB performance deterioration on structural response for four representative bracing layouts: single-diagonal (symmetric), single-diagonal (asymmetric), chevron (inverted-V), and multi-story X-braced schemes. All layouts significantly reduced seismic responses; among them, the chevron configuration exhibited the lowest sensitivity to degradation, with response amplification after 120 hygrothermal cycles markedly lower than that of the single-diagonal asymmetric scheme. The findings provide an experimental basis and design reference for seismic design and durability assessment of structures in long-term hot–humid service regions
Climate Change Impacts on Rainfall Variability and Adaptive Reservoir Operation in a Multi-Reservoir System
No full textChanges in rainfall patterns driven by climate change have altered the hydrological regime of river basins, creating substantial challenges for water resources management, particularly in the operation of the Batutegi cascade system comprising the Batutegi Dam, Way Sekampung Dam, Argoguroh Weir, Margatiga Dam and Jabung Weir. This study assesses the impacts of climate change on rainfall intensity, dependable flow, and water allocation modeling within the Sekampung River Basin. The analysis employed five rainfall datasets downscaled from the NASA Earth Exchange Downscaled Climate Projections at 30 arc-seconds (NEX-DCP30) and simulated using five CMIP6 models for both the historical period (1980–2014) and future projections (2024–2100). Results indicate that CMIP6 projections reproduce rainfall patterns reasonably well during January–February and May–July, but perform less consistently in March–April and October–November. Most models tend to overestimate the mean annual rainfall. Rainfall variability contributes to pronounced fluctuations in river discharge, particularly during the dry season. Dependable flows show marked changes, especially within the exceedance probability range of Q10% to Q100%. Although an overall increasing rainfall trend is observed, the system is still able to satisfy water demand under the 2023 operating rules, with potential deficits persisting during critical periods. Optimization modeling further demonstrates the necessity of adaptive reservoir operation rules under climate change, which could improve the reliability of meeting multisectoral demands to approximately 80%. These findings underscore the importance of incorporating climate model projections into watershed-based water resources management to strengthen resilience against extreme hydroclimatic variability
Finite Element Analysis of Concrete Beams Reinforced with Basalt Fiber-Reinforced Polymer
No full textThe increasing demand for corrosion-resistant reinforcement in concrete structures has highlighted the potential of basalt fiber-reinforced polymer (BFRP) bars as a sustainable alternative to conventional steel reinforcement. However, the flexural behavior of BFRP-reinforced concrete beams remains insufficiently characterized, particularly through advanced numerical simulation. This study develops and validates a finite element model (FEM) to analyze the flexural performance of BFRP-reinforced concrete beams and to compare it with that of steel-reinforced beams. Eight beam specimens (200 × 300 × 3,100 mm), including six reinforced with BFRP bars and two with steel bars, were modeled under four-point bending using ANSYS software. The FEM predictions were validated against experimental data and benchmarked with the design provisions of ACI 440.1R-15 and CSA S806-12. The model showed strong agreement with experimental results, yielding ultimate load ratios of 0.92–0.94 for steel-reinforced beams and 1.01–1.45 for BFRP-reinforced beams. At higher reinforcement ratios, FEM predictions tended to overestimate the capacity of BFRP-reinforced beams. While steel-reinforced beams exhibited ductile failure, BFRP-reinforced beams failed in a brittle manner. The predicted moment-deflection responses and crack patterns closely matched both experimental observations and code-based predictions. This validated FEM provides a reliable computational framework for assessing and optimizing the design of BFRP-reinforced concrete beams, thereby advancing the application of non-metallic reinforcement in structural engineering. The findings also highlight challenges in accurately modeling concrete crushing and bond behavior within FEM, indicating directions for future refinement
A Comparative Study of a Series of Supervised Learning Models for Motorcycle Crash Injury Severity Prediction
Get PDFMotorcycle crashes pose a major public health challenge in Thailand, where motorcyclists account for most traffic fatalities. This study aims to evaluate and compare the predictive performance of four supervised learning models—Decision Tree (DT), K-Nearest Neighbor (KNN), Naïve Bayes (NB), and Random Forest (RF)—for motorcycle crash injury severity using data from the Highway Accident Information Management System (2020–2022). After preprocessing, 36 explanatory variables covering roadway, environmental, accident causes, crash characteristics, and vehicle involvement were analyzed. To address class imbalance, the Synthetic Minority Oversampling Technique (SMOTE) and cost-sensitive learning were applied, and models were validated using train–test splits with cross-validation. The Random Forest model achieved the best performance with an AUC of 0.726, balanced accuracy of 0.649, and Matthews Correlation Coefficient (MCC) of 0.308, outperforming the other algorithms. SHapley Additive exPlanations (SHAP) were used to interpret the RF model, identifying nighttime crashes, large truck involvement, and roadway features (e.g., depressed medians and two-lane roads) as key predictors of severe outcomes. These insights suggest countermeasures such as improving nighttime safety, dedicating truck lanes, and designing safer medians. The novelty of this study lies in integrating model comparison, imbalance-aware metrics, and SHAP interpretability to provide actionable, context-specific policy recommendations for motorcycle safety in Thailand
Assessment of Sulfur Dioxide Levels in Atmospheric Air Over the Period 2019–2024
Get PDFThis study investigates the spatiotemporal distribution and dynamics of atmospheric sulfur dioxide (SO₂) over the Crimean Peninsula during the period 2019–2024, employing protected natural areas as background reference sites for air quality assessment. The primary objective is to determine the variability in SO₂ concentrations in the atmosphere over Crimea. Methodologically, the study involves selecting background sites across diverse landscape levels throughout the peninsula, and applying Z-analysis to categorize ambient air pollution into four levels: conditionally low, average, elevated, and high. The analysis encompasses annual mean SO₂ levels, assessment of temporal trends, and localization of pollution hotspots. Results indicate a peak in SO₂ levels in 2020, predominantly at mid-mountain landscape level, and a minimum in 2019. Overall, a decreasing trend of 25.4 µmol/m² per year in SO₂ concentrations is observed, despite localized zones of high pollution, including areas northeast of the regional center, Simferopol. In 2022, the low-mountain landscape level of the northern macroslope exhibited the most extensive conditionally high pollution zone, covering nearly half of its territory. The novelty of this work lies in integrating protected natural areas as reference sites within the Z-analysis framework, enabling more precise identification of anthropogenic influences and the spatial distribution patterns of sulfur dioxide concentrations in the region’s atmosphere
A Novel Steel Lazy Wave Riser Configuration for Ultra-Deepwater
Get PDFA steel lazy wave riser (SLWR) configuration combines buoyancy modules with a traditional steel catenary riser (SCR). The buoyancy section at the riser separates the floater's motion and acts as a damper toward the critical area in the touchdown point, improving the strength and fatigue performance. In ultra-deepwater environments, the substantial payload of risers due to extreme riser length imposes considerable tension and stress, challenging the limits of traditional configurations such as SLWR and SCR. The effective tension, maximum stress, and minimum bend radius at ultra-deep depths of these conventional risers would exceed the allowable limits, leading to potential structural failure. To address these limitations, this study proposes a novel riser configuration, the shaped steel lazy wave riser (SSLWR), specifically for ultra-deepwater conditions. By introducing an additional buoy section, SSLWR effectively reduces the effective tension while ensuring allowable stress distribution across the riser length, enhancing structural reliability and operational feasibility over traditional risers. OrcaFlex, a fully 3D non-linear finite element software widely used in maritime structure analysis, was used to simulate the effective tension, maximum stress, and minimum bend radius of the SCR, SLWR, and SSLWR configurations at 3000 m depth. The SSLWR shows a maximum effective tension that is less than half of that observed in the SCR, and it remains consistently lower than SCR and SLWR, suggesting that SSLWR holds promise as a robust alternative for ultra-deepwater applications. This study offers new insights into how modifying riser shape and buoy placement can effectively balance tension reduction with stress distribution, providing an alternative to traditional riser designs. The SSLWR's specific responses to buoy placements and varying currents expand an understanding of riser performance under varying conditions, guiding future advancements in offshore riser engineering. Doi: 10.28991/CEJ-2025-011-01-03 Full Text: PD
Shaking-Table Test on a Multi-Story Continuous Vibration-Control System Employing Pulley Amplification Mechanism
Get PDFThis study proposes an innovative passive vibration-control system, named the Pulley Damper Multi-story System (PDMAS), which incorporates pulley tackles installed at multiple stories in the successive stories to amplify inter-story displacement. This configuration significantly enhances the energy absorption efficiency of the linked dampers at the middle of the cable by utilizing the cumulatively amplified story displacements via a continuously stretched cable across the entire structure. The proposed system shows notable potential for controlling responses induced by higher vibration modes by customizing the wire installation layout. The aim of this study is to introduce PDMAS and to investigate its seismic-mitigation effectiveness. As a primary investigation of this new system, comparative experimental studies were conducted through shaking-table tests on nine specimens featuring various cable layouts optimized for the first and second structural vibration modes, with or without dampers, under harmonic waves, white-noise waves, and simulated seismic waves. The experimental results demonstrate that the PDMAS effectively accommodates the cumulative amplified story displacement across the structure to match theoretical damper values. Furthermore, the specimens employing PDMAS with a wire layout optimized for the first structural mode reduced both acceleration and displacement by nearly half compared to specimens without PDMAS. Doi: 10.28991/CEJ-2025-011-01-02 Full Text: PD