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2007 research outputs found
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Natural Frequency of Liquefaction Potential Based on Soil Investigation and Microtremor Observation Results
No full textThis study aims to identify the natural frequency threshold for liquefaction potential by comparing four assessment methods at 54 identical sites in Padang, Indonesia. Methods include: (1) safety factor calculations from soil investigation results (CPT and SPT) applying the 2009 Padang earthquake's peak ground acceleration as input for cycling stress ratio; (2) natural frequency measurements at the surface using microtremor single observations; (3) liquefaction potential assessment through vulnerability index; and (4) analysis of historical liquefaction events from the September 30, 2009 Padang earthquake documented in two previous research papers. The analysis focused on soil depths ranging from 1-4 m. Findings reveal that sites with natural frequencies exceeding 0.40 Hertz remain safe from liquefaction, while sites with frequencies between 0.20-0.39 Hertz demonstrate significant liquefaction potential. This research contributes to the field by establishing a clear correlation between measurable natural frequency thresholds and liquefaction risk, providing engineers and urban planners with a more accessible parameter for preliminary risk assessment. Integrating multiple assessment methods at identical sites enhances the reliability of the identified frequency thresholds, offering a more comprehensive approach to liquefaction hazard mitigation in earthquake-prone regions
Assessing Urban Characteristics: The C-DNA As a Catalyst of Urban Morphogenesis
No full textHistoric city centers are cultural archives where built forms and spatial practices hold the collective memory of generations. In Baghdad, the concept of Cultural DNA (C-DNA) is a tool to understand how cultural codes are the generative rules that shape the evolution and persistence of the historic urban fabric. This research explores the role of C-DNA as a trigger of urban morphogenesis in Rusafa, the historic heart of Baghdad, by looking into how cultural values underpin spatial continuity, change, and adaptability. The study uses Space Syntax methodologies with DepthmapX, supported by historical maps, surveys, and field observations, to analyze two morphological stages of Rusafa: 1850 and now. Through axial analysis, the research measures integration, connectivity, choice, and control to evaluate key urban characteristics: centrality, hierarchy, privacy, and territoriality. This comparative approach highlights both continuity and disruption in the historic fabric. The results show that cultural nuclei (mosques, markets, khans, and schools) are still the central points of the city, anchoring movement and interaction across centuries. Despite the disruption caused by modern interventions like Al-Rashid Street, the organic urban fabric still holds the capacity to sustain privacy, territoriality, and hierarchical spatial arrangements. The findings prove C-DNA is not a metaphor but an operational system that generates urban order and resilience. The study concludes that understanding C-DNA is crucial for developing sustainable revitalization strategies in Baghdad and similar Islamic historic cities. By treating culture as the city’s genetic code, planners and policymakers can design interventions that preserve cultural identity while accommodating urban needs
A Model to Estimate the Level of Passenger Satisfaction With the High-Speed Train
No full textPassenger satisfaction must be measured by operators providing high-speed train services, as it is directly related to passenger loyalty, which in turn ensures the business's sustainability. This study aims to measure passenger satisfaction with the Jakarta-Bandung high-speed train by developing a model that considers various factors significant in influencing user satisfaction. The quantitative method was developed by distributing questionnaires to 300 respondents, and the results were analyzed using SEM. The results of this study prove the existence of a model built from 5 (five) dimensions: the availability of information, accessibility, train comfort, emergency actions, and responses to complaints. The results of this study are expected to provide recommendations to the operator of the Jakarta-Bandung High Speed Train to evaluate the factors of 5 (five) dimensions that are considered important in forming a user satisfaction model for the service using a performance analysis matrix (IPA Diagram). According to the results of the IPA diagram, it is evident that the most urgent task for the operator is to consolidate with third parties related to the availability of modes to serve passengers who will continue their journey to Bandung, particularly for work and tourism purposes
Quantifying Slope Stability and Landslide Susceptibility Through Rainfall-Induced Geotechnical Assessment
No full textLandslides are a major hazard to people and infrastructure, especially in areas with weak geology and high rainfall. This study examined soil properties and slope stability in Ranau (RNU) and Kota Belud (KB), Sabah. Soil tests showed that RNU had 2–21% clay with cohesion of 3.49–9.7 kPa, while KB soils contained 2–17% clay, more sand and gravel, and much lower cohesion of 0.5–1.1 kPa, indicating weaker strength and higher permeability. Rainfall data from 2013–2023, provided by the Malaysian Meteorological Department, were used to develop Intensity-Duration-Frequency (IDF) curves. Results showed that 1-hour intensities increased from 0.92 mm/hr at ARI-2 to 2.18 mm/hr at ARI-100, reflecting the variation of extreme rainfall. Slope stability was analyzed using GeoStudio’s SEEP/W and SLOPE/W to simulate infiltration and compute the Factor of Safety (FOS). In RNU, FOS rose from 2.481 to 2.565 after 24 hours, showing stable slopes. In KB, FOS declined from 2.495 to 2.379 under ARI-100 rainfall, along with higher pore-water pressures. Both slopes remained above the safe limit of 1.50, but KB proved more vulnerable to long rainfall. Compared with earlier studies, this research introduces a decade-long dataset combined with numerical modelling to demonstrate the dynamic response of tropical slopes. The findings provide practical contributions to slope design, drainage management, and disaster risk reduction in regions experiencing similar climatic and geological conditions
Performance Evaluation of Composite CNT/PE-Modified Asphalt Concrete at Binder, Mixture, and Pavement Levels
No full textAdvancing the multi-scale performance of asphalt pavements requires innovative binder modifications that address limitations in rutting resistance, fatigue resistance, and durability across the binder, mixture, and structural levels. This study evaluates the performance of asphalt cement, mixtures, and pavement systems modified with a combination of polyethylene (PE) and carbon nanotubes (CNTs). The binder was modified using 4% PE and varying CNT contents (0.5%, 1%, 1.5%, and 2% by weight of the modified binder). Binder performance was assessed through conventional and rheological tests, including penetration, softening point, viscosity, performance grade (PG) evaluation, and master curve analysis. Mixture-level performance was evaluated using Marshall properties, rutting, resilient modulus, and fatigue tests. Long-term pavement behavior was predicted using VESYS 5W software. The results showed that incorporating 1.0% CNT with 4.0% PE significantly improved binder rheology, increasing the true failure temperature by approximately 10% compared to the reference binder. Complex modulus and phase angle master curves also indicated notable improvements at low frequencies. Mixtures containing 2% CNT demonstrated approximately one-third of the permanent strain observed in the reference mix, while PCNT1.0% exhibited the best fatigue resistance. These findings highlight the significant role of combining plastomeric modifiers (PE) with nanoscale materials (CNTs) in enhancing the performance of asphalt binders and mixtures
Projections of Land-Cover Change in a Tropical High-Andean Lake
No full textLand use and land cover change is one of the main drivers transforming high Andean ecosystems in Colombia. This study examines the spatial dynamics of land use in the La Cocha Ramsar Wetland between 1989 and 2020 and projects land cover scenarios to the year 2050 using spatial modeling techniques. Land cover maps for 1989 and 2020 were developed using satellite imagery and photo-interpretation, following the CORINE Land Cover methodology adapted for Colombia. A transition matrix and change indicators defined by the Institute of Hydrology, Meteorology and Environmental Studies (IDEAM) were used for multitemporal analysis, allowing the identification of processes such as forest fragmentation and recovery, agricultural expansion, and the spread of pastures. Future projections were modeled with the Land Change Modeler (LCM) module in the IDRISI Selva software, incorporating biophysical and socioeconomic variables with significant association (Cramér’s V > 0.4). Eight dominant transitions were identified, and change potential maps were generated. The model was validated through random field sampling and a confusion matrix analysis, yielding a Kappa index of 0.76, indicating strong agreement between simulated and observed data. Results show that 91.06% of the area remained unchanged, while 8.94% underwent transformations attributed to human activities. A net increase of 66.75 ha in dense forest is projected by 2050, along with growth in fragmented forest areas and agro-pastoral mosaics
Mechanical Performance of Volcanic Ash Concrete Showing Modulus Reduction with Strength Retention
No full textThis study aims to evaluate the mechanical behavior of concrete that incorporates 51.3% raw volcanic ash into its structure, focusing on its static elasticity modulus and compressive strength. Cylindrical concrete samples were prepared via the mix design commonly used in practice in Baños, Tungurahua, Ecuador. Three curing methods were applied: immersion, water spraying, and no curing. Compressive strength tests were conducted at 3, 7, 14, 21, and 28 days, whereas the static modulus was measured at 28 days following ASTM C469. Despite the high use of ash in the mixture, the mixtures achieved adequate compressive strengths for structural applications, reaching 28.05 MPa. However, a significant reduction in the static modulus was observed, with experimental values of approximately 7.06 GPa, whereas the value of 24.89 GPa was predicted by the equations given in ACI318. The use of raw volcanic ash in structural mixes requires modifications to deformation and stiffness calculations to ensure seismic performance, suggesting the need to review local regulations on traditional mixes. Based on the experimental data, an alternative empirical model, the VAM model, was proposed to better predict the elastic modulus of concrete with high volcanic ash content. The findings reveal a dual function of ash, acting as a pozzolanic material and as a low-density aggregate, highlighting the need to adjust the design equations when raw volcanic ash is used. This work contributes to the sustainable design of concrete mixtures in seismic regions
Development of Sustainable Self-Compacting Concrete Using Slag Sand and Expanded Clay Aggregates
No full textThe objective of this study is to develop a sustainable self-compacting concrete (SCC) by partially replacing natural aggregates with slag sand (SS) and lightweight expanded clay aggregate (ECA) in combination with a ternary binder system, thereby enhancing both performance and environmental sustainability. The methodology involved preparing thirty SCC mixes of M30 grade using 65% Ordinary Portland Cement, 25% fly ash, and 10% silica fume as binder, with slag sand replacing river sand at 20–100% and ECA replacing coarse aggregate at 20–100%. Fresh properties were evaluated through slump flow, T50, V-funnel, L-box, and U-box tests following EFNARC guidelines, while mechanical strength (compressive, split tensile, and flexural) was measured at 7, 28, and 90 days. Durability was assessed through sulphuric acid and magnesium sulphate exposure, and microstructural behavior was studied using FTIR and TGA. Results revealed that mixes with higher ECA content enhanced flowability, with A2B10 achieving superior workability (slump flow 694 mm, T50 2.9 s), while A2B6 (20% SS + 20% ECA) achieved optimum strength (45.21 MPa compressive) and durability retention under aggressive exposures. The novelty of this work lies in demonstrating the synergistic role of slag sand and ECA in producing SCC with enhanced performance, reduced natural aggregate usage, and improved sustainability compared to conventional SCC
Clay Crack Initiation and Propagation Resistance Mechanism Using Municipal Solid Waste
No full textThis study investigates the potential of black seed flour (Nigella sativa) as an additive to enhance the crack resistance of clay-based landfill liners, aiming to mitigate gas transfer and leachate formation in landfill environments. Two distinct clay types were mixed with varying proportions of black seed flour (10%, 20%, and 30% by weight). The crack propagation resistance was assessed through desiccation tests over short (24 hours) and medium (72 hours) durations. Parameters such as crack morphology, fracture toughness, and crack propagation time were analyzed using image analysis and mechanical testing. The addition of black seed flour significantly influenced the crack morphology and propagation characteristics. Clay type 2 exhibited optimal fracture toughness at 10% and 30% black seed flour concentrations. The presence of black seed flour delayed crack initiation and reduced crack width, indicating improved crack resistance. Comparative analysis with existing literature suggests that the incorporation of natural additives like black seed flour can enhance the structural integrity of landfill liners. This research introduces black seed flour as a sustainable, cost-effective additive to improve the mechanical properties of clay-based landfill liners. The study provides new insights into utilizing natural materials for environmental engineering applications, contributing to the development of more resilient and eco-friendly landfill liner systems
Enhancing AA6061–Bottom Ash Composites: Role of Heat Treatment on Properties and Dimensional Stability
No full textAluminum matrix composites (AMCs) reinforced with industrial by-products have attracted attention as lightweight, sustainable materials, yet most research has focused on fly ash. The higher density of bottom ash compared to fly ash makes bottom ash suitable for use as reinforcement in AMC. This study investigates the combined effect of BA reinforcement (0, 3, and 6 wt%) and T6 heat treatment (aging at 175, 200, and 225 °C) on the microstructure, mechanical performance, thermal expansion, and dimensional stability of AA6061 composites. Mechanical testing, thermomechanical analysis (TMA), and coordinate measuring machine (CMM) evaluations were conducted to establish correlations between microstructure and macroscopic reliability. The results show that aging plays a decisive role in strengthening and stabilizing the alloy. The unreinforced AA6061 achieved peak hardness (69.43 BHN) and tensile strength (274.60 MPa) at 200 °C, but exhibited the largest distortion due to high thermal expansion. BA addition significantly reduced the mean coefficient of thermal expansion, with the 3 wt% BA composite aged at 200 °C demonstrating the most balanced behavior: stable CTE response, minimal distortion (0.1–0.4 mm²), and improved mechanical reliability. In contrast, 6 wt% BA composites, despite their lowest mean CTE (≈25 ppm/K), suffered from local instabilities due to particle agglomeration and porosity, leading to reduced toughness and higher geometric irregularities. Overall, this work highlights the novelty of employing BA as a sustainable reinforcement distinct from fly ash, showing that moderate BA addition coupled with optimized heat treatment can enhance dimensional stability and mechanical performance. The findings provide new insights into the design of cost-effective, environmentally friendly AMCs for structural applications