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Effect of Polypropylene Fibers on Swelling Potential and Shear Strength of Clay
No full textExpansive clays can cause major problems for urban development (roads, railways, infrastructure, etc.); therefore, reducing the swelling potential of clays has always been a concern in the geotechnical field. The presented paper investigates the effect of polypropylene reinforcement fibers on the swelling potential and shear strength of clay. The samples studied were taken from the clayey region of Mila, located in the northern east of Algeria. The experimental procedure adopted in this research consists first of the assessment of the physical, mechanical, and mineralogical characteristics of the soil samples without reinforcement. Then, swelling pressure, swelling rate, and swelling index are used to assess the swelling potential of these samples. After the reinforcement using a variety of polypropylene fiber concentrations (2 to 6% of the weight of the dry clay), the free swelling is clearly reduced. The optimum reinforcement rate in this case is 4%, in which the swelling was reduced by 90.7%. Finally, to offer more insights regarding the impact of clay reinforcement using polypropylene fibers, the effect of this later on the mechanical properties of the studied clay was also analyzed through the tangential shear strength. It was found that the polypropylene fibers increased the tangential shear resistance of Mila's clay. Doi: 10.28991/CEJ-2023-09-03-04 Full Text: PD
Numerical Investigation of the Optimum Angle for Open Channel Junction
No full textNumerous natural and artificial streams, including those for irrigation ditches, wastewater treatment facilities, and conveyance structures for fish movement, have open channel confluences. The flow dynamics at and around the junction are intricate; in particular, immediately downstream of the junction, the flow creates a zone of separation on the inner wall along with secondary recirculation patterns. The structure of this complicated flow depends on several factors, including the flow rates in both channels, the angle of confluence, the geometry of the channels, including the longitudinal slope and bed discordance, the roughness of the boundary, and the intensity of the turbulence. It also has a significant impact on bed erosion, bank scouring, etc. The objective of the current work is to calculate the velocity profile and the separation zone dimensions for four angles (30o, 45o, 60o, and 75o) through the simulation process, and the best angle using a three-dimensional model. This work gives a detailed application of the numerical solution (Finite Volume) via Flow 3D software. Results for two flow discharge ratios, q*=0.250 and q*=0.750 were shown; the numerical model and the experimental results agreed well. The findings are consistent with past research and demonstrate how the main channel flow pattern is affected by changes in the channel crossing angle, as well as how greater separation zones are produced in the main channel when the flow discharge ratio q* (main channel flow divided by total flow) is smaller. Analysis revealed that the separation zone's smallest diameter will be at the 75ocrossing angle. Doi: 10.28991/CEJ-2023-09-05-07 Full Text: PD
The Acoustic Performance of Natural Composites in Reducing Stress Levels: Textile Industry
No full textThe porous characteristics of recycled natural fibres make them suitable for use as acoustic materials. Straw and water hyacinth fibres are natural materials that can potentially be used as composites in damping devices. This study evaluated the acoustic performance of two types of reinforced composites containing natural fibers (water hyacinth and rice straw) and gypsum adhesives in reducing stress levels in the textile industry. The evaluation was carried out through laboratory tests using impedance tubes and direct testing in a textile factory to reduce the stress level of production machine workers and operators. Rice straw and water hyacinth fibres were thoroughly mixed in proven mass ratios of 10% and 30% with water and gypsum plaster as a binder. The mixture was pressed into a mould at a pressure of 3 MPa before being heated in an oven at 900ºC for 5 hours. Perforations measuring 4 to 8 mm in diameter were then made at equal distances on the panels. Acoustic panel performance tests were carried out with impedance tubes according to ISO 10534-2 standards at sound frequencies ranging from 0 to 6400 Hz. Field tests were also conducted at a textile factory, with each machine unit generating a sound source of 100 to 110 dB. Heart rate data was collected, and noise measurements were carried out before and after the panels were installed in the area around the operating machines. The results showed that the rice straw-gypsum composite with four perforations performed the best, achieving an α coefficient of 1.0 at a frequency of 1500 Hz and an NRC of 0.50, indicating effective noise reduction. The installation of acoustic panels around the noise source in the textile industry reduced noise levels by up to 9.8 dB and was found to affect workers' heart rates, indicating reduced stress levels. The questionnaire results also showed a significant effect on the stress levels of workers. The use of natural fibers in composite materials has the potential to be an eco-friendly and sustainable solution for soundproofing applications. Doi: 10.28991/CEJ-2023-09-06-02 Full Text: PD
Experimental and Analytical Study on Postfire Reinforced Concrete Beams Retrofitted with CFRP in Flexure and Shear
No full textIn this study, experiments were performed on carbon fiber reinforced polymer (CFRP) retrofitted postfire reinforced concrete (RC) beams, followed by theoretical analyzes. Experiments were conducted on eleven RC beams, which were exposed to different fire durations and retrofitted with CFRP in flexure and shear. The experimental results indicated that fire shifted the flexure failure to the flexure-shear failure of postfire RC beams. CFRP retrofitted postfire RC beams experienced progressive peeling-off failure. FRP retrofitting significantly increased the yield deflection by 58.2−97.3% but decreased the ultimate deflection by 43.0−55.5% compared with that of the control beam. Consequently, the ductility was reduced by 69.7−74.7%, categorized as low ductility. CFRP retrofitting successfully increased the strengths of 30-min postfire beams by up to 23.1% higher than those of the control beam. Fire significantly decreased the stiffness of postfire beams by 46.4−49.2% compared with that of the control beam, whereas CFRP retrofitting did not fully recover the stiffness of postfire beams. Finally, a simple model of the moment capacity of postfire beams without/with CFRP retrofits was developed based on the practicability of limited data feasibly obtained from real fires. The proposed model, with its simplicity, practicability, and reasonable accuracy, can be a useful tool for structural engineers in the FRP retrofitting of postfire RC structures. Doi: 10.28991/CEJ-2023-09-07-05 Full Text: PD
Ventilation Performance of Air Duct in Double Loaded Corridor Building: A Case Study
No full textBuildings with double-loaded corridor types are often found in Indonesia and generally function as offices or lecture rooms. This type of building is popular because of its efficient circulation path to accommodate the movement of occupants. However, a wall separating the room from the corridor makes it impossible to put windows to implement a cross-ventilation system due to acoustic problems. Hence, to achieve indoor thermal comfort, this type of building relies on using an air conditioning (AC) system. However, with the WHO's call to reduce the use of AC during the COVID-19 pandemic, it is necessary to evaluate cross-ventilation in double-loaded corridor buildings to meet comfort standards while still preventing acoustic problems due to noise from corridors and other spaces. The study proposes a new natural ventilation system using air ducts placed above the corridor ceiling to create cross-ventilation in lecture buildings. The E-ITERA building was chosen as a case study in this research. The building has a glass facade with several small windows that can be opened outside. The corridor of this building is designed with openings at both ends, allowing for direct connection to the outside air. The walls facing the passage have a single door and four small ventilations on the aisle's upper side. Simulations were carried out in two classrooms on the 3rd floor using CFD (Computational Fluid Dynamics) software. Experiments were carried out to change the size of the air duct and the size of the ventilation on the wall that leads to the corridor. The results showed that the air duct was able to create cross-ventilation. Ventilation performance is improved when the WWR air duct is the same as the WWR window. The highest air velocity in the centre of the room is 0.6 m/s. Doi: 10.28991/CEJ-2023-09-10-06 Full Text: PD
Production Economical Reinforced Concrete Slabs using Eco-Friendly Material
No full textConcrete is a material that is strong in compression but weak in tension. To overcome this issue, reinforcement must be used to improve the tensile strength of the concrete. However, it is acknowledged that steel has its drawbacks, such as the fact that it has a high cost and corrosion potential, and the rebar is heavy, non-renewable, and non-environmentally friendly. Thus, this experimental study investigates the potential product of economical reinforced concrete slabs using eco-friendly materials. Firstly, to enhance the concrete properties, a compressive, tensile, and flexural test, also a concrete with the addition of polypropylene fiber outlasted the control mix design in terms of strength and durability. The results included the control mix (CM), F1 0.25%, F2 0.50%, F3 0.75%, and F4 1%. The specimen with the highest compression and tensile strength was 24.28 MPa and 3.15 MPa, respectively, for the F1 specimen with 0.25% short fibers. Secondly, the bending test was carried out on ten slabs to check the structural behavior of these slabs reinforced with reed rods as the eco-friendly material. The good results of the bearing capacity of a partially reinforced concrete slab with a reed have been obtained at 23.8 kN. Meanwhile, to obtain better results, this research has enhanced the behavior of the concrete slab by improving the concrete's properties by adding polypropylene synthetic microfiber to the mixed concrete. In addition, giant reeds treated with epoxy increase the bonding strength with concrete, improve tensile strength properties, and reduce the absorption of reeds. Therefore, the bearing capacity results of the reed-reinforced concrete slab became the best, which were 35.83 kN. Thus, reinforcement of one-way slabs by reed partially with appropriate diameters could be substituted to obtain good performance in the reconstruction of low-cost buildings. As a result, economical reinforced concrete slabs have been produced using eco-friendly materials. Doi: 10.28991/CEJ-2023-09-06-010 Full Text: PD
Proposal for the Expansion of the Light Rail Vehicle Network
No full textThe objective of this study is to present a preliminary study to demonstrate the importance of expanding the Light Rail Vehicle (LRV) in the city of Joí£o Pessoa. This would ensure the best level of operational comfort, safety, social inclusion, and sustainability with the existing transport network in the city. The methodology used began with the collection of data provided by public agencies that regulate urban transport modes in the city and other technical sources that report on the feasibility of implementing the LRV. Then the main bus routes used by the population were analyzed (in relation to passenger volume) and how these routes could be improved if LRV could be inserted as a viable option. With the study, it was realized that there is no possibility of replacing one mode of transportation with another to drive all passengers. The optimal solution is to make expansions in the system that can make LRV an affordable and quality alternative for people to move around the city. Doi: 10.28991/CEJ-2023-09-10-014 Full Text: PD
An Intelligent Approach for Predicting Mechanical Properties of High-Volume Fly Ash (HVFA) Concrete
No full textPlastic waste (PW) is a major soild waste, which its generation continues to increase globally year in and year out. Proper management of the PW is still a challenge due to its non-biodegradable nature. One of the most convenient ways of managing plastic waste is by using it in concrete as a partial substitute for natural aggregate. However, the main shortcomings of adding plastic waste to concrete are a reduction in strength and durability. Hence, to reduce the undesirable impact of the PW in concrete, highly reactive additives are normally added. In this research, 240 experimental datasets were used to train an artificial neural network (ANN) model using Levenberg Marquadt algorithms for the prediction of the mechanical properties and durability of high-volume fly ash (HVFA) concrete containing fly ash and PW as partial substitutes for cement and coarse aggregate, respectively, and graphene nanoplatlets (GNP) as additives to cementitious materials. The optimized model structure has five input parameters, 17 hidden neurons, and one output layer for each of the physical parameters. The results were analyzed graphically and statistically. The obtained results revealed that the generated network model can forecast with deviations less than 0.48%. The efficiency of the ANN model in predicting concrete properties was compared with that of the SVR (support vector regression) and SWLR (stepwise regression) models. The ANN outperformed SVR and SWLR for all the models by up to 6% and 74% for SVR and SWLR, respectively, in the confirmation stage. The graphical analysis of the results further demonstrates the higher prediction ability of the ANN. Doi: 10.28991/CEJ-2023-09-09-04 Full Text: PD
Effect of Infills on the Response Modification Factor for Infilled Reinforced Concrete Frame Buildings
No full textRC frames with unreinforced masonry infill walls are the most common type of building. Unreinforced masonry walls are often not considered by engineers in the design process, although walls and frames interact during strong ground motion, leading to structural responses deviating radically from what is expected in the design. Under lateral load, reinforced concrete confining members (frames) act in tension or compression, depending on the direction of the lateral seismic pressures. Meanwhile, masonry walls act as diagonal struts prone to compression. This research aims to develop the effect of masonry infills and their distribution on the value of the resulting response modification factor. For this purpose, a parametric study was performed on five, seven, and ten-story' buildings modeled as bare and infilled frames. Infill ratio, panel aspect ratio, unidirectional eccentricity, and bidirectional eccentricities were the parameters investigated. Each proposed model's resulting response modification factor was compared to the value cited in different international codes. It was concluded that this value differs depending on several parameters and cannot be constant for a certain structural system. The novelty of this research is the deduction of a general equation to calculate the response modification factor as a function of the percentage of infills and the eccentricity, while presenting two different methods to calculate it. Doi: 10.28991/CEJ-2023-09-12-09 Full Text: PD
Recommending Surface Water Quality Monitoring for the Nature Reserve Using Multivariate Statistical Methods
No full textLung Ngoc Hoang Nature Reserve has a crucial role in conserving and protecting the natural ecosystem and biodiversity in the Mekong Delta, Vietnam, and the local communities also receive great benefits from aquatic resources in this nature reserve. This study was conducted to assess water quality in the Lung Ngoc Hoang Nature Reserve and to provide important information for the monitoring program using multivariate statistical methods. Water samples were collected bimonthly from fifteen locations belonging to five functional zones of the nature reserve (i.e., buffer zone, main canal, administrative and service zone, ecological restoration zone, and strictly protected zone). The physiochemical properties of water samples were measured, including temperature, pH, electrical conductivity (EC), total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), sulfate (SO42-), iron (Fe2+), and aluminum (Al3+). The results showed that the levels of TSS, COD, and Fe2+ exceeded the Vietnamese standard on surface water quality, and the DO level was also far below the standard. Besides, the concentrations of TN, TP, and Al3+ in the nature reserve area showed the risk of eutrophication and negative effects on aquatic organisms. Problems of water quality were observed in the main canal and the administrative and service zones more than in the other zones. Cluster analysis (CA) suggested a reduction in the number of monitoring frequencies and locations to four months (i.e., January, April, July, and September) and twelve locations, respectively. This reduction allows for a decrease in the effort and cost of the monitoring program with adequate information to evaluate water quality. Moreover, principal component analysis (PCA) identified five principal components, which could explain 80.98% of the total variance of the initial dataset. Potential pollution sources were also recognized based on PCA, including the nature properties of sulfate-acid soils, livestock, fertilizer, and domestic activities. The findings of this study can enhance our understanding of water quality in the nature reserve area and the effectiveness of future monitoring programs. Doi: 10.28991/CEJ-SP2023-09-015 Full Text: PD