2031 research outputs found
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Drying Shrinkage of Cement Stone with Superplasticizers of Various Chemical Bases
No full textThe crack resistance of reinforced concrete structures also depends on concrete shrinkage. Therefore, assessing the influence of mix design factors and operating conditions on concrete shrinkage is essential to determine the relationships between shrinkage magnitude and kinetics and variables such as ambient humidity, cement properties, and admixture characteristics. These relationships are important for calculating shrinkage crack resistance and, consequently, the durability of reinforced concrete structures. The widespread use of superplasticizers and other mineral additives in concreting, including new complex modifiers, highlights the need to clarify known relationships and identify new dependencies involving the material and mineralogical composition of cements, the properties of admixtures, concrete mix formulation, and environmental humidity on both the magnitude and kinetics of shrinkage deformations. The purpose of this study is to identify patterns in the development of shrinkage deformations of cement paste depending on the type of cement and superplasticizer, including the influence of dehydration degree, and to propose equations that can be used to calculate the shrinkage crack resistance of reinforced concrete structures. The study includes an analysis of established approaches for evaluating changes in drying shrinkage of cement paste as ambient humidity varies. Experimental investigations were conducted on the drying shrinkage of cement paste as a function of evaporable water content and the chemical basis of superplasticizers. The influence of superplasticizers on both the kinetics and magnitude of the basic shrinkage of cement paste is demonstrated, considering evaporable water content under standard conditions as well as after drying to constant mass at 105 °C. The effect of relative air humidity on the basic shrinkage of cement stone has also been clarified. Furthermore, an equation describing the kinetics of shrinkage of cement pastes and a classification of cements based on shrinkage kinetics are proposed. Finally, the dependence of shrinkage for the studied cements with different superplasticizers on relative air humidity is established
Spatial Prediction of Soil Index Properties Using GIS and Empirical Bayesian Kriging
No full textThe purpose of this study is to assess the possible use of Empirical Bayesian Kriging (EBK) combined with Geographic Information Systems (GIS) to map and analyze geotechnical index properties in Thi Qar Province in southern Iraq. The aim of this objective is to describe the spatial variability of soil limits of the consistency and define areas with expansive soils, which may influence infrastructure development. Data on 550 boreholes and 862 observations per soil property, including Liquid Limit (LL), Plastic Limit (PL), and Plasticity Index (PI), were analyzed. To test the predictive accuracy of the EBK model and thus assure its statistical validation, RMSE, MSD, RMSSD, and correlation coefficients were used to test the model. The findings show that the LL was between 32% and 69%, the PL between 9% and 36%, and the PI between 1% and 39%, with most of the soils being CL and CH, which signifies moderate-high plasticity. The results indicate that there are good spatial patterns, and plasticity is more dense in the north and central areas. The originality of this work is the use of EBK to create detailed digital soil maps of a semi-arid area, where the available geotechnical data is sparse, which is used to form a dependable base to support engineering design, land-use planning, and regional geotechnical modelling
An Experimental Study on Web Hardening Technology Using Encasement by RPC and Lacing Reinforcement
No full textOver the past ten years, cold-formed steel two-channel sections featuring edge-stiffened castellated cellular web apertures have been developed and are now widely used in New Zealand. Previous research on vertical compression has shown that using edge-stiffened web openings in these channel sections increases their vertical load capacity. Subsequent studies expanded to include hexagram web holes; however, the literature still lacks investigations on the effect of applied vertical pressure on web openings in two-channel sections with perforated webs. This research addresses that gap. The aim of this study is to evaluate the structural response of symmetrical castellated two-channel (2C) sections. Six specimens of castellated 2C beams made of cold-formed steel and encased in reactive powder concrete with diagonal reinforcement on both sides were examined. The concrete encasement and reinforcement enhanced the beam’s resistance to buckling, bending, and both horizontal and vertical shear, and also improved joint performance. Two concentrated loads were applied at the beam center to investigate the structural behavior of each specimen. The results showed that the presence of a joint gap enhanced load resistance. The ultimate load increased by 6.75% compared with the reference specimen SCB2C-rLG20% in G3, by 30.86% compared with SCB2C-rL in G2, and by 1064.73% compared with SCB2C/R1 in G1. The specimen with a 30% gap demonstrated the best load capacity and the highest ductility compared with the reference specimen and the other specimens
A Correlated Random-Field Ising Model for Pore-Scale Hysteresis in Soil-Water Characteristic Curves
No full textThe soil–water characteristic curve (SWCC) plays a central role in the behavior of unsaturated soils, yet explaining its hysteresis directly from pore-scale mechanisms remains challenging. The objective of this study is to investigate how pore-size heterogeneity, spatial correlations, and cooperative dynamics contribute to hysteresis in SWCCs. In this study, a correlated Random-Field Ising Model (RFIM) combined with Monte Carlo simulations is developed to represent the pore space as a two-dimensional lattice with a bimodal distribution of pore volumes and a spatially correlated disorder field. Drainage processes are simulated without parametric curve fitting, enabling direct analysis of pore-scale switching dynamics. The results show that macropore fraction, pore-size heterogeneity, and the activation parameter \beta exert a strong control on drainage behavior. Low \beta values produce smooth and nearly reversible drainage, whereas higher \beta stabilizes metastable pore configurations and yields abrupt transitions accompanied by hysteresis. The divergence between number-based and volume-based saturation serves as a useful indicator of size-selective drainage and cooperative pore-scale events. The novelty of this work lies in providing a physically grounded and statistically dynamics to macroscopic hysteresis in SWCCs, offering insights beyond traditional phenomenological or uncorrelated pore-network approaches
Effect of Fly Ash and Nano-Silica Fume on Soft Clay: Atterberg Limits, MDD, and OMC
No full textTo improve the geotechnical properties of soft clay soil, this study compares and contrasts two types of micro and nano stabilizing additives: fly ash and nano-silica fume. Treatments with fly ash and nano-silica fume were applied to soft clay samples from Basra, Iraq, at varying fly ash concentrations. The samples were then subjected to the treatments. The ASTM requirements were adhered to in the laboratory tests conducted to investigate changes in plasticity characteristics, maximum dry density, and optimum moisture content (OMC). In the course of this research, Atterberg limits and standard compaction tests were undertaken. In accordance with the findings, fly ash reduces MDD (maximum dry density) by increasing the plastic limit and OMC while simultaneously decreasing the liquid limit and plasticity index. On the other hand, nano-silica fume enhances MDD, decreases OMC and the plastic limit, and increases the plasticity index and the liquid limit. The flocculation and dilution of clay particles are both promoted by fly ash, but the significant reactivity of nano-silica fume increases water adsorption and pore filling. The differences in particle size, specific surface area, and interaction mechanisms explain the observed divergent tendencies. Micro- and nanosized additives added to local soft clay at the same dosage were compared and contrasted in this study. This comparative analysis aims to help select the most effective stabilizing agents that either increase soil plasticity or improve compaction properties. The use of such an approach is a new methodological contribution
AI-Driven Shear Capacity Model of Steel Studs in Composite Structural Systems
No full textIn composite steel-concrete structures, shear connectors in the form of headed steel studs are commonly utilized to transfer longitudinal shear force developed at the interface between the two materials. To overcome the shortcomings of design codes, which frequently understate shear capacity and fail to take advantage of sophisticated computational methods, this paper presents an optimization attempt to estimate the shear strength of headed steel studs utilizing the Grey Wolf Optimizer (GWO) technique using MATLAB software. Data from 234 experimental tests are employed to identify and highlight key input parameters influencing the shear strength of headed steel studs. These key parameters include concrete compressive strength (f’c), diameter (D), and tensile strength of the steel stud shank (fu). After identifying and examining the limits of the experimental data, the proposed model has been developed using about 80% of the mixed raw dataset. The remaining 20% of the raw data is utilized to validate the proposed model. The predicted shear strength of headed steel studs closely matched the experimental results. This research offers an innovative strategy to measure the steel stud's shear capacity employing GWO, showing the current code's limitations. The GWO model showed excellent accuracy in predicting the shear strength with an R-value of 0.9922, indicating that the predicted value is in good agreement with experimental observations. Interestingly, the model's mean absolute error with 100 wolves in the GWO method was only 7.51%, showing the proposed model provides an improvement in shear capacity forecasting for practical structural engineering applications
High-Resolution Silt Distribution Mapping Using Ordinary Kriging From Borehole Data in a Geohazard-Prone Area
No full textKundasang, Sabah, is one of the most geohazard-prone highland regions in Malaysia. Slope failures are frequently triggered by heavy rain. Silt-rich zones present a particular stability problem, since silt has low cohesion and drains faster than clay, which means that slopes can undergo rapid saturation and lose shear strength during sustained and intense rainfall. Previous research works in Kundasang have focused on landslide susceptibility through rainfall thresholds and GIS terrain analysis. However, depth-specific, high-resolution silt distribution maps have not yet been produced. This study addresses the research gap using geostatistical modeling of geotechnical data from boreholes to map silt distribution patterns. Soil samples from 70 boreholes were analyzed by classifying soil types down to 10 m depth in 2.5 m segments. Using Ordinary Kriging in ArcGIS 10.3, the best-fit semivariogram model for each depth was selected based on the lowest Root Mean Square Error values (ranging from 5.33 to 11.92). The findings reveal that high-silt zones (areas with over 30% silt content) cover around 40% of the study area and cluster mainly in western and northern Kundasang, particularly in the upper 7.5 m of soil. These correspond to areas previously documented as highly susceptible to rainfall-induced slope failures. The depth-specific silt distribution maps produced in this study provide important geotechnical inputs to enhance future landslide susceptibility assessments, improve slope stability analyses, and support risk-informed land-use planning for local authorities in geohazard-prone highland areas
A Multivariate Analysis of Smartphone Use Behavior Among Motorcyclists at Urban Intersections
No full textThe increasing use of smartphones while riding motorcycles poses significant safety risks, particularly in urban environments of middle-income countries with high motorcycle usage. Despite growing global concerns, limited research has examined the combined influence of individual, behavioral, and environmental factors on smartphone use among motorcyclists at signalized intersections. This study investigates the determinants of smartphone use behavior—both hand-held and hands-free—among motorcyclists in Khon Kaen City, Thailand. A total of 31,648 riders were observed using video surveillance across eight intersections with varying geometric and land-use characteristics. As part of the methodological approach, binary and multinomial logistic regression models were applied to analyze factors associated with smartphone use. The results show that 7.7% of motorcyclists used smartphones while riding, with 6.2% using hand-held and 1.5% using hands-free modes. Significant predictors included riding alone, being male, not wearing a helmet, riding during nighttime or weekdays, and stopping at red lights. Delivery riders were particularly likely to use smartphones, especially in hands-free mode. These findings highlight the multifaceted nature of distracted riding and suggest the need for comprehensive, context-sensitive policy interventions. The insights gained from this study can inform strategic planning and safety enforcement not only in Thailand but also in other urban areas across middle-income countries where motorcycles remain a dominant mode of transport
Structural Performance of Circular Hollow Steel Damper with Fins and Gaps
No full textPrior studies have shown that fin reinforcement on a circular hollow steel damper (CHSD) could mitigate buckling and enhance shear strength. However, in bridge applications, repeated vibrations from lateral traffic loads and low-frequency cyclic actions may cause premature energy dissipation and fatigue damage, thus reducing the seismic performance of CHSD during design-level earthquakes. To address this issue, this study integrates fins and gaps into CHSD to enhance stability against buckling and to mitigate fatigue-induced damage. The CHSD specimens were fabricated in three variations: without fins, with fins, and with fins and gaps. Cyclic loading tests and nonlinear finite element analyses were conducted to evaluate their effects on mechanical properties and seismic performance. Cyclic loading was performed in accordance with the AISC 341-22 protocol and applied at 0° and 30° to simulate multidirectional lateral forces. The cyclic test results reveal that the addition of fins exhibits both beneficial and adverse effects on the mechanical properties and seismic performance of CHSD, while the gap reduces the equivalent viscous damping ratio. The backbone curves derived from the numerical analyses agree well with experimental results. Furthermore, the damper shear resistance and deformation capacity are delayed by the presence of gaps, mitigating fatigue-related damage
A Wastewater Strength Indicator for Estimating the Energy Performance and Recovery Potential in WWTPs
No full textThis study aims to propose a practical indicator that enables quick and reliable evaluation of the relationship between influent characteristics and energy performance and recovery in municipal wastewater treatment plants (WWTPs). A composite Wastewater Strength Indicator (WWSI) was developed, integrating wastewater dilution and pollutant load into a single metric. Theoretical correlations were established through mathematical estimation and verified using case studies of six WWTPs in Bulgaria based on operational data from 2020–2022. WWSI correlates strongly with both specific energy consumption (kWh/kg COD removed) and electrical energy recovery rate. WWTPs with a WWSI below 0.25 perform unsatisfactory, exhibiting specific energy consumption levels above 2.0 kWh/kg removed COD, whereas those with a WWSI above 0.35 demonstrate higher energy efficiency, with specific consumption below 1.0 kWh/kg removed COD. The treatment of low-strength wastewater leads to inherent energy inefficiencies that are difficult to overcome through sludge digestion and cogeneration alone. Despite sludge calorific values ranging from 11.5 to 19.4 MJ/kg, the energy recovery potential in the studied WWTPs remained below 35%, confirming that energy neutrality is challenging for diluted wastewater. A conversion coefficient of 0.039 kWh/MJ was introduced to facilitate rapid estimation of potential electrical recovery from sludge calorific values. The proposed WWSI provides a simple yet effective tool for benchmarking WWTPs and supports future upgrades toward energy-neutral wastewater management