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The Behavior of Enlarged Base Pile Under Compression and Uplift Loading in Partially Saturated Sand
Get PDFThe aim of this paper is to study the behavior of enlarged base piles embedded within partially saturated soils under compression and uplift loading. This type of pile is rarely excavated and cast on-site. Accordingly, to construct an enlarged base pile model, an excavator was designed and manufactured to give appropriate shape through drilling and casting in the laboratory through the design and manufacture of an excavator to produce piles with a shaft of 35 mm in diameter, 500 mm in length, and a base of 80 mm in diameter inclined at an angle of 60 degrees. Three different partial saturation soils were achieved by lowering the water level below the soil surface 20, 40, and 60 cm and measuring the suction force of each stage using a Tensiometer. The average matrix suction results were 6.4, 7.6, and 9.1 kPa for each lower water level, respectively. The test results showed that the bearing capacity of the enlarged base piles under compression load in partially saturated soil was higher than that in the case of full saturation because of matrix suction, with an improvement rate of 2.5–4.5 times compared with the case of fully saturated soil. Additionally, test results showed that the enlarged base piles subjected to uplift loading in partially saturated soil were significantly improved compared with the fully saturated condition, with an improvement rate of 1.5 - 3 times. The reason for this is the apparent surface cohesion of the sandy soil, which increases the bearing capacity of the sandy soil. This study sheds light on the phenomenon of apparent surface cohesion of sandy soil and the extent of its effect on increasing the soil's resistance to the loads placed on it. Doi: 10.28991/CEJ-2024-010-10-08 Full Text: PD
Vibration Control of Corrugated Steel Web Box Girder Bridge with Friction Pendulum Isolation
Get PDFIn order to investigate the feasibility and applicability of friction pendulum bearings for vibration control of large-span space beam-arch bridges with corrugated steel web box girders, taking the Huian Yellow River Bridge in Guide County, Qinghai Province, China, as an example. A three-dimensional calculation model of the friction pendulum isolation space beam-arch composite bridge with a corrugated steel web was established by MIDAS, the modal analysis was carried out, and the damping effect of the friction pendulum isolation bridge was investigated using the response spectrum and the time history analysis methods; the influence of the design parameters of the friction pendulum isolation on the reduction effect was further analyzed. The results show that the friction pendulum isolation improves the stress conditions of both the girder and the pier and reduces the displacement and acceleration of the pier top, as well as reduces the acceleration of the girder, and the damping ratio is more than 50%. The optimal dynamic coefficient of friction and the radius of curvature for the corrugated steel web composite bridge are 0.04 and 3.0 m, respectively. Friction pendulum isolation has a good seismic absorption effect and provides an effective way for the seismic control of the corrugated steel web composite bridge. Doi: 10.28991/CEJ-2024-010-10-01 Full Text: PD
Optimizing Injection Moulding Processes for Structural Components in Construction Management
Get PDFThe optimization of injection molding processes for structural components is critical in construction management, particularly for enhancing precision, efficiency, and sustainability. However, existing research has not fully addressed the complex interplay of factors that influence this optimization. This study aims to fill this gap by identifying and analyzing five key constructs: Structural Performance, Material Efficiency, Sustainability and Integration, Precision and Consistency, and Design Flexibility. Data were collected from 249 professionals in China using a Likert-scale survey and analyzed through Exploratory Factor Analysis (EFA), Confirmatory Factor Analysis (CFA), and Structural Equation Modeling (SEM). The results show that Structural Performance is the most significant factor (β = 0.943, p < 0.001), followed by Material Efficiency (β = 0.858, p < 0.001) and Sustainability and Integration (β = 0.772, p < 0.001). The model's predictive relevance, with a Q² value of 0.659, confirms its robustness and accuracy. These findings highlight the need for construction managers to focus on improving Structural Performance and Material Efficiency while integrating sustainability and ensuring precision and flexibility. Optimizing injection molding for construction components is challenging due to complex factors like structural performance, material efficiency, and sustainability. This study develops a novel framework using Structural Equation Modeling to rank these factors, providing insights for cost-effective, high-performance outcomes, and advancing sustainable practices in construction management. Doi: 10.28991/CEJ-2024-010-10-020 Full Text: PD
Study of Reversible Nozzle Apparatuses Using Euler Methodology and CFD Technologies
Get PDFThis research aims to study multiflow nozzle apparatuses designed to control the thrust vector within a full geometric sphere when the deflection angle of the thrust vector can vary in the range from +180 °to -180 °in any direction. The distribution of the working gas energy was considered as exemplified by a reversible nozzle apparatus with two outlet channels. It was shown that when using wedge-shaped diaphragms, the critical section area can be regulated while maintaining a constant pressure and flow rate of the working gas entering the inlet of the multiflow nozzle. In this case, the mass flow rate of the gas and jet thrust in each outlet channel change in direct proportion to the linear displacement of the diaphragm. Known conical diaphragms do not provide these results. To create promising control systems and train designers, it is proposed to use the Euler methodology and CFD technologies more widely based on the philosophy of technology. In the course of the numerical experiments, the options for the thrust cutoff (tailoff) were considered. A scientific basis has been prepared for solving problems with six degrees of freedom in three-dimensional space, considering Euler angles, when controlling the thrust vector within a full geometric sphere. Issues in flight trajectory planning (for example, for an unmanned aerial vehicle) are discussed with regard to new possibilities for extreme maneuvering. Two main areas for the development of scientific research are considered: energy-saving power generation and transportation systems (land, sea, and air). Doi: 10.28991/CEJ-2024-010-11-013 Full Text: PD
Kinematic Seismic Isolation System with Magnetic Dampers
Get PDFThe aim of this study is to experimentally and theoretically investigate the behavior of a three-story fragment of a frame building constructed using the PGF-SIKF system”Prefabricated girderless frame with seismic-isolating kinematic foundations. Magnetic dampers are employed at the support level. The novelty of the research lies in the combination of a girderless frame with kinematic foundations and innovative magnetic dampers. The experimental research method involved loading the system with horizontal static force using a stationary winch, followed by the release of the load. Vibration measurements were recorded using a digital measurement system. The normative live load was simulated by applying additional static load. It was determined that the oscillation period varies between 1.8 and 2.1 seconds, depending on the amplitude of the impact. The dissipative characteristics of the seismic isolation system were obtained, with acceleration values during the testing phases ranging from 95 to 177 cm/s². The experimental results confirmed that the building fragment showed no visible damage. The logarithmic decrement of oscillations was found to range between 0.08 and 0.16. Theoretical studies involved calculations based on a sample of 14 real accelerograms, with parameters corresponding to the magnitudes of local earthquakes (M=6), the maximum magnitude expected in Shymkent. The main result is the reduction of seismic loads achieved by using kinematic foundations in the girderless frame system. It was established that, under 7-8 intensity seismic events, the average displacements at the foundation level will not exceed the experimental values. Doi: 10.28991/CEJ-2024-010-11-018 Full Text: PD
Study of Post-Spalling Reinforced Concrete Beam Repair Using Grouting and GFRP Reinforcement
Get PDFReinforced concrete beams must meet strength and durability standards, but aggressive environmental factors are the main cause of corrosion, which can affect the strength and durability of building structures. Maintenance, retrofitting, and reinforcement of structures are important to ensure safety. It is necessary to take appropriate measures to address corrosion problems in building structures early on. One way to achieve this is by repairing damaged structures using more modern and effective technologies and materials. This study aims to determine the flexural behavior of reinforced concrete (RC) beams repaired with Sikagrout-215 material and reinforced with GFRP sheets with different layer configurations. The study used three RC beams as the control group, three RC beams coated with Sikagrout-215 mortar, and six RC beams reinforced with GFRP. All beams were subjected to 4-point bending tests to determine their load capacity, crack response, ductility, and energy absorption capacity. The results showed that repair with grouting decreased the load capacity, while reinforcement with a combination of mortar grouting and GFRP increased the maximum load. Reinforcement of the support region could restore the function of the beam by 9.3%. Among the three types of reinforcement, BGRST significantly improved the first crack response, yield response, and ultimate performance of the RC beams. Beam fracture occurred more frequently with Sikagrout-215 mortar reinforcement, while reinforcement with GFRP composites partially protected the load capacity after fracture. Doi: 10.28991/CEJ-2024-010-01-08 Full Text: PD
The Effectiveness of the Procurement at the Construction Services Selection Implementation Center
Get PDFThe construction industry still faces various challenges in some developing countries, and one of the problems is the procurement of goods and services. The allocation of public procurement funds is significant to the national GDP. It is essential to conduct comprehensive research on government procurement in the construction industry in Indonesia due to the rapid growth of the construction industry in the last decade. This research focuses on the procurement of construction goods and services in the Ministry of Public Works and Housing by looking at the perception of the government as the project owner. This research aims to identify a model of critical success factors to improve public procurement performance in the construction industry from the government's perspective. The research method includes two stages, namely, the development of critical success, which consists of crucial factors and indicators that affect the performance of public procurement in the construction industry. It is a literature study of relevant previous research results from various countries that affect these critical success factors. Then, the second stage is a survey of experts' perceptions through questionnaires. The questionnaire data analysis used SEM-PLS software to quantify the relationship model of critical success factors to improve the performance of government procurement of goods and services in the construction industry. Data processing results include: business process factors affect 97.1%, regulatory factors affect 90.1%, information system factors affect 63.1%, human resource factors affect 56.1%, organizational factors affect 46.1%, and monitoring and evaluation factors affect 38%. Doi: 10.28991/CEJ-2024-010-03-013 Full Text: PD
Effect of Breach Parameters and Progression Curves on Dam Failure Hydrograph
Get PDFUnderstanding the failure mechanisms of embankment dams due to overtopping is vital for flood protection, covering planning, design, and flood defence zone management. Typically, dam failure-induced flood wave propagation is modeled in 1D using Saint-Venant's equations. The breach itself is often simplified as a trapezoid defined by its final height, average width, side slopes, and the time required for complete formation. Often overlooked is the dynamic process of breach formation and its correlation with the outflow hydrograph during dam failure. This research scrutinizes the impact of breach parameters and progression curves on the outflow hydrograph. Two approaches were formulated: one crafting new equations for average breach width and formation time using global dam failure data and regression analysis, and the other employing these equations in 2D HEC-RAS dam failure modeling, comparing them with literature recommendations. The derived equations yield results similar to those in the literature. This study introduces a novel aspect by examining the mutual influence of results and floodplain areas on the outflow hydrograph, offering a comprehensive perspective on dam failure dynamics and its hydraulic consequences. Doi: 10.28991/CEJ-2024-010-02-08 Full Text: PD
Monitoring Physiological State of Drivers Using In-Vehicle Sensing of Non-Invasive Signal
Get PDFEighty percent of traffic accidents are caused by human error, called hypo vigilance, stemming from drowsiness, stress, or distraction while driving. This poses a significant threat to road safety. An electrocardiogram (ECG) is often used to monitor drivers' health. Thus, enhancing vehicles with Internet of Things (IoT) sensors and local analytical databases becomes crucial for real-time detection and transmission of relevant health data to avoid things that compromise road traffic safety. This study introduces a cost-effective in-vehicle ECG sensing prototype using an AD8232 sensor integrated with an Arduino Uno and an AD8232 Wi-Fi module placed on the steering wheel to monitor the driver's heart signal while driving. Short-term heart rate variability (HRV) features were computed through Python from the acquired ECG data, and supervised machine learning techniques such as AdaBoost, Random Forest, Naí¯ve Bayes, and Support Vector Machine (SVM) classified the features into normal and abnormal classes. Naive Bayes exhibited the highest accuracy (90.91%) and F1 score (85.71%), surpassing Random Forest's lower accuracy (63.64%) and F1 score (50.00%). These findings indicate the prototype's potential as a valuable tool for ensuring safe and efficient driving, proposing integration into standard vehicle safety systems for enhanced road traffic safety. Doi: 10.28991/CEJ-2024-010-04-014 Full Text: PD
Effect of Steel Fiber on Plastic Hinge Length of Concrete Columns: Buckingham Theory Application
Get PDFThe accuracy of designing the performance of concrete structures nowadays not only depends on the use of standard materials (cement, sand, and gravel) for certain concrete strengths but also on the accuracy of using additional materials for concrete, such as steel fiber. The use of steel fiber not only can improve the performance of concrete structures to behave in a ductile manner but can also form plastic hinges according to design purposes. The design of the axial load of Pa=0.121.Ag.f'c is based on the prediction of the column's axial capacity. The columns were designed to behave in a flexural manner. As predicted, the lengths of the plastic hinges were found not too long. Controlling the length of plastic hinges in the design of structural concrete members is necessary to avoid excessive displacements. The control is mainly related to the prediction of the plastic hinge length. Thus, in this case, a plastic hinge length formula is required. In the study, the length of the plastic hinges of columns, which are confined with square stirrups and reinforced with steel fiber with Vf = 0%, 0.5%, 1%, 1.5%, and 2%, is proposed. This plastic hinge length formula is proposed after all column test specimens have met the displacement ductility requirement of mD>4, meaning that all test specimens are defined as very ductile. Doi: 10.28991/CEJ-2024-010-05-03 Full Text: PD