Challenge Journal Publications (TULPAR Academic Publishing)
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Structural behavior of ferrocement beams with circular openings
Full text linkThe construction sector is a major contributor to resource consumption and waste generation. Therefore, developing more efficient and sustainable materials and infrastructure is a top priority for achieving the Sustainable Development Goals. This research aims to contribute to this effort by studying the behavior of ferrocement beams with circular openings, with the goal of understanding their behavior under various loads and determining their potential use in designing more resilient and sustainable structures. Fifteen beams with different reinforcement mesh types were subjected to experimental testing under four-point loading, one group serves as the control with conventional reinforcement, while others vary in mesh type and opening configurations. All beams maintained approximately close reinforcement ratios, employing either two layers of welded galvanized steel mesh or a single layer of expanded steel mesh. Using numerical models, all fifteen beams were analyzed with the structural analysis program ANSYS V. 15 to study their non-linear shear behaviors and compare them with experimental data, focusing on load-deflection curves and failure modes. Results show that beams reinforced with expanded steel mesh achieved higher ultimate loads than those with welded mesh, with increases up to 81.59% depending on the opening configuration. However, beams with openings generally exhibited reduced ultimate loads, averaging 26.85% for welded mesh and 32.13% for expanded mesh, compared to beams without openings. Vertical openings, particularly with multiple openings, resulted in significant load decreases
Investigation of the seismic response of irrigation channel using Coupled Eularian-Lagrangian approach
Full text linkWhile devastating earthquakes affect cities, they can also cause serious damage to irrigation structures in agricultural areas. Cracks and structural deteriorations may occur in water structures using concrete such as dams, aqueducts and open channels. This study investigates the earthquake response of irrigation canals through fluid-structure interaction analysis. The earthquake response of an irrigation canal was examined by establishing fluid-structure interaction. Finite element models, with material properties and dimensions determined, were created and analysed with destructive earthquake records. In the finite element model, the behaviour of water inside the channel is simulated using the Coupled Eulerian-Lagrangian (CEL) approach. In the analyses, displacement and stress values were examined in the model without water, and in addition to these, fluctuations on the water surface were examined in the model with water. The observed changes are shown with graphs and contour diagrams. As a result, it was shown that hydrodynamic effects reduced horizontal displacements by 42% but increased the maximum principal tensile stresses by 49% and the maximum principal compressive stresses by 75%, compared to the non-water model. In addition, it was observed that in both models, the dynamic analysis values at the time of the earthquake increased by approximately 7‒13 times the static values before the earthquake. These findings underscore the importance of dynamic analysis using fluid-structure interactive models for safeguarding irrigation structures against seismic hazards, thereby ensuring food security in vulnerable agricultural regions. Therefore, it is important to perform dynamic analysis with fluid-structure interactive models for irrigation structures exposed to destructive earthquake forces
Effect of different trimline extension of clear aligners in combination with Class II elastics on the mandibular dentition: a finite element analysis
Full text linkObjective of this study is to evaluate the effect of different trimline extension of aligners and the effect of elastics applied through the slit cutouts and buttons on the mandibular dentition using Class II intermaxillary elastics combined with clear aligner treatment. Three-dimensional (3D) finite element models that simulate the effects of Class II elastics on the mandibular arch in four different scenarios were studied, named, straight and high trimline aligner (HTLA) model with elastic applied through buttons (Model 1), straight and low trimline aligner (LTLA) model with elastic applied through buttons (Model 2), HTLA model with elastic applied through slit cutout (Model 3), LTLA model with elastic applied through slit cutout (Model 4). 3D displacements of the teeth, von Mises stress (VMS) in the periodontal ligament (PDL) were calculated. In all models, the crown of the mandibular anterior teeth moved labially, the root moved lingually, and the mandibular first molars moved mesially. Among all models, labialization of incisors and mesialization of molars was highest in Model 2 and lowest in Model 3. In clear aligner treatment combined with Class II elastics, HTLA was more effective in controlling mandibular incisor proclination and mesial tipping of mandibular molars. The slit cutout models were more effective in controlling mesial tipping of mandibular molars
Advantageous approach for boron ores used in cement production: optimization of dehydration
Full text linkBoron with a certain water content is used for industrial purposes, including cement production. It is necessary to perform and optimize heat treatments and determine the water content. The heat treatment is applied to boron ores that must be used for cement production. However, these processes take time and increase costs. With this study, it will be possible to obtain boron products with the desired properties in a shorter time by determining the optimal parameters for dewatering processes. Colemanite and ulexite ores were reduced to a grain size of 44 microns by ore dressing processes and subjected to dewatering. The Taguchi method was used to optimize the dehydration of colemanite and ulexite ores. The orthogonal design of experiments method L18(6132) 3 factors, 18 trials was chosen to determine the design of experiments. The changes in the H2O-CaO-Na2O-B2O3 concentrations were determined on the basis of the analyses performed. TG/DTA analyses were carried out for comparison with the dehydration processes. In the optimization processes performed using the Taguchi method, the maximum water removal was achieved with 1 g of ore and a period of 6 hours. H2O removal was 98.42% at 650 °C for colemanite and 99.1% at 300 °C for ulexite. It has been shown that the dehydration of ulexite and colemanite ores can be optimized and the boron product with the desired properties can be obtained in a short time, which is an advantage for its use in the cement industry. It is expected that this study will serve as an important basis for future applications of B2O3 cement
Comparison of dexmedetomidine dosing strategies based on Bispectral Index (BIS) and Ramsay Sedation Scale (RSS) in patients undergoing infraumbilical surgeries under spinal anesthesia: A prospective comparative study
Full text linkObjectives and Aim: This study aimed to evaluate the impact of dexmedetomidine infusion dosage adjustment strategies guided by BIS and RSS on total consumption in patients undergoing infraumbilical surgeries under spinal anesthesia.Materials and Method: Eighty patients aged between 18-70 years, classified as American Society of Anesthesiologists (ASA) I and II, who underwent orthopaedic, urological, and plastic surgery under spinal anesthesia were included. Patients received spinal anesthesia in the lateral position through the L3-4 interval using a median approach. Following the observation of free flow of cerebrospinal fluid, spinal anesthesia was induced with 10 mg (2 ml of 5% hyperbaric bupivacaine) bupivacaine and 25 µg of intrathecal fentanyl. When the sensory block reached the T10 level, all patients were administered a dexmedetomidine loading dose of 1 µg/kg IV over 10 min for sedation, and the maintenance drug infusion dose was titrated to maintain BIS values between 60-80 in the first group and RSS at 3-4 in the second group. Throughout the surgery, hemodynamic variables (heart rate and blood pressure), respiratory parameters (respiratory rate), SpO2, sedation scores (BIS and RSS), and drug infusion doses and perioperative complications were recorded. Drug infusion was stopped 5 min before the end of surgery, and the duration of surgery, anesthesia, and total drug consumption were recorded. Statistical analyses were performed, and a p-value of less than 0.05 was considered statistically significant.Results: Desired sedation was achieved by dexmedetomidine administration. A decrease in BIS values and an increase in RSS were observed with the loading dose. In both groups, the heart rate and systolic and diastolic blood pressures were significantly lower at all measurement times than the control values. There was no significant difference in the mean blood pressure between groups B and R (p>0.05). The average blood pressure for B group was 92 ± 14.12 mmHg, while the average blood pressure for R group was 90 ± 12.73 mmHg. There was no statistically significant difference between the two groups in terms of dexmedetomidine infusion doses required to achieve the desired sedation and total drug consumption 110 ± 20 (µg) in B group and 111 ± 22 µg in R group (p>0.05).Conclusions: Dexmedetomidine provides a targeted level of sedation in patients undergoing spinal anesthesia without causing significant respiratory depression. Monitoring sedation depth using the BIS did not change the total drug consumption
Prediction of optimum design of welded beam design via machine learning
Full text linkDesign optimization is an important engineering design topic. One of the important issues in structural design is to minimize the cost. This study based on an engineering problem of Welded Beam Design aims to minimize the cost of the beam with machine learning (ML) models depending on the constraints on applied load, shear stress, bending stress and end deflection. The data set to be used in this context was created using a metaheuristic optimization algorithm. This hybrid algorithm is based on the classical Jaya algorithm by adding the student phase of Teaching Learning Based Optimization. The dataset obtained as a result of the optimization is a dataset with 1189 rows. Six different algorithms were used for prediction analyses. These are Linear Regression, Decision Tree, Elastic Net, K-Nearest Neighbour, Random Forest, and XGBoost algorithm. In the data set, load, length, and displacement are input; the design variables such as b, h, l, t and minimum cost are output. Since there is more than one output in the dataset, Multioutput Regression is applied. The performance of regression models was assessed using the Coefficient of Determination (R²), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). According to the results obtained, the Decision Tree Model showed the best performance among the other models (R2=1, MAE=6.13e-11, RMSE=9.47e-10)
Freeze-thaw and drop-weight impact resistance of fiber-reinforced pervious concretes produced using recycled pervious concrete aggregate
Full text linkPervious concrete can rapidly drain stormwater from the top layer to the sublayer. However, the porous structure of this concrete also results in low mechanical properties, which prevent the widespread use of pervious concrete around the world. This study investigated the freeze-thaw and drop-weight resistances of pervious concrete produced with recycled pervious concrete aggregate. Two different aggregate types (limestone and recycled) and two different aggregate size fractions (15/25 mm and 5/15 mm) were used to examine the effect of aggregate type and gradation. Additionally, for improving mechanical and durability properties, polypropylene fibers were used at three different dosages by the volume of mixtures (0.1%, 0.2%, and 0.3%). Within the scope of the study, compressive, splitting-tensile, and flexural strengths, effective porosity, freeze-thaw, abrasion, and impact resistance of pervious concrete were determined. The results showed that concrete produced with recycled aggregate had some advantages in terms of porosity; however, its mechanical properties, freeze-thaw, and impact resistance were lower than those of pervious concretes produced with limestone aggregate. Additionally, fiber addition decreased the compressive strength and effective porosity of pervious concrete. However, up to a certain point (0.2%), fiber addition improved abrasion, freeze-thaw, and impact resistance, as well as splitting tensile and flexural behavior of pervious concrete
