Circular Opening Research Articles

Experimental and analytical investigation on effect of openings in behavior of reinforced concrete deep beam and enhanced by CFRP laminates

This work studies the potential of producing web openings within the shear span for the reinforced concrete (RC) deep beams. Carbon fiber reinforced polymer (CFRP) laminates are used to improve the shear strength. 13 specimens with dimensions of 120, 750, and 1800 mm are prepared for the tests. Shapes of the web openings are square and circular with diameter of 230, 300, and 370 mm. Their locations are in the center, upper and lower of the shear span. Three angles for wrapping 0°, 45°, and 90° are used to strengthen the beams with circular openings. The shear strength of RC deep beams decreased in the range of 22–74 % depending on the diameter, location, and shape of the openings. While CFRP improved the shear strength, stiffness and toughness in about 17–48 %, 0.7–17 % and 4–20 % respectively. The previous percentages depended on size of openings and the orientation of CFRP laminates in RC deep beams with circular openings. The laminates of CFRP are able to repair and restore the bearing capacity of beams by approximately 100 % of the same beams before they failed. On the other hand, Strut and Tie method established to estimate the maximum strength of the RC deep beams and it results that the theoretical method succeeded in guessing the practical results.

Static and vibration analysis of reinforced cement concrete cellular beams: A three-dimensional study

This paper presents an analysis of Reinforced Cement Concrete (RCC) cellular beams, focusing on both static and dynamic aspects. The study investigates the behavior of RCC cellular beams under varying loads, including dead weight, superimposed loads, and environmental factors like wind. It addresses the essential characteristics of dynamic problems compared to static loading scenarios, emphasizing the influence of time-varying loads on structural response. The research methodology involves the design and analysis of a simply supported RCC beam with circular openings, utilizing advanced computational tools such as RISA 3D®. The study outlines the process of modeling, including the design of circular openings and reinforcement details. It also discusses the theoretical background, including the strut and tie model of concrete, which is essential for understanding the structural behavior. The paper presents the results of static and vibrational analysis, including stress distribution, mode shapes, and fundamental frequencies of vibration. The analysis evaluates the performance of RCC cellular beams, considering factors such as stress concentrations, principal stresses, shear stresses, and Von Mises stresses.

Improving Efficiency of Corn Seed Separation and Calibration Process

Abstract The paper analyzes the existing theoretical research of corn seed separation and calibration processes. The machines, tools and equipment that implement the process were studied. An innovative sieve with openings in the Cassini oval shape was proposed for the economical separation and calibration of corn seeds. The results of operation of the proposed sieve in the operating conditions of Kharkiv Feed Mill on BSH-100 serial separators were considered. The study of the effectiveness of sifting corn seeds through the holes of the sieves was carried out in partnership with the State University “Ukrainian Research Institute of Forecasting and Testing of Agricultural Production Techniques and Technologies named after Leonid Pohorily” (Kharkiv Branch). The use of sieves with openings in the Cassini oval shape, instead of classic circular base openings, was found to result in an increase in throughput capacity of the sieve and open area of up to 20%.

Intraoperative management of axial posterior capsular opacities during cataract surgery in six dogs.

Posterior capsular opacification (PCO) is a cause of decreased vision after canine cataract surgery. PCO can appear in the months following surgery but can also be present at the time of surgery. To describe the intraoperative management of marked axial PCO during canine cataract surgery through a retrospective case series study of six cases. Six dogs (six eyes) with cataracts were included in this study. A complete ophthalmologic examination including electroretinography and ocular ultrasound was performed. After conventional phacoemulsification, a marked PCO obstructing the visual axis was found in five cases, previously diagnosed by ultrasound in the sixth. An axial posterior capsulorhexis (APC) was performed in all cases, before or after implantation of the intraocular lens (IOL). For the four cases implanted before APC, the posterior capsule (PC) was visualized either by positioning the IOL laterally in the bag with viscoelastic or through the optic of the implant. After perforation of the PC with a 30-Gauge needle, APC was initiated with Vannas curved scissors, then finalized with Utrata forceps to obtain a circular axial opening (3 mm diameter). In each case, a moderate anterior vitrectomy was performed through the APC (under the IOL when initially placed), then the IOL centered and the viscoelastic was removed. Six dogs (Beagle, German Shepherd, Cavalier King Carles, French pointing dog, American bully, Beagle Harrier) aged 11 to 94 months (mean 51.8) were included. The mean follow-up period was 15.5 months (range 10-22). Visual function with capsular axial transparency and well-centered IOL, without complications during the follow-up period, was preserved for each eye. APC combined with moderate anterior vitrectomy appears to be effective in the treatment of marked axial PCO obstructing the visual axis during canine cataract surgery.

유공이 있는 철근콘크리트 보의 전단강도 및 설계 제한에 관한 실험적 평가

이 연구에서는 유공의 직경, 위치, 간격, 개수, 보강방법을 변수로 하는 4그룹 21개의 유공보 실험체에 대한 반복가력 실험을 수행하였다. 최대 전단강도에 대한 실험결과를 기존 유공보 전단강도 평가식 및 Mansur의 제안식에 의한 계산 결과와 비교하여 유공보 최대강도 예측에 있어 이들 평가식의 정합성을 비교하였다. 보 단면 높이에 대한 유공 직경의 비, 유공 직경에 대한 유공 간격의 비, 유공의 위치, 유공 보강형상이 보의 전단 강도에 미치는 영향을 평가하였다. 마지막으로 영향평가 결과를 토대로 기존과 비교하여 보다 단순하고 직관적인 유공보 전단강도 평가식을 제안하고, 주요 변수들에 관한 설계 제한을 명확히 제시하였다. 제안식은 기존 철근콘크리트 유공보의 전단강도 예측식 및 Mansur의 제안식보다 합리적으로 예측한 것을 확인하였다.

Torsional Behavior of RC Beams with Transverse Openings Strengthened by Near Surface Mounted-Steel Wire Rope Subjected to Repeated Loading

The presence of the openings negatively effects on the strength of the beams where they act as a weak point because of the sudden change in the cross-section of the beam, so it becomes necessary to make strengthening for the beams to resist the effect of the openings and improve the strength of the beams, especially if the beams are subjected to repeated loads because of its effect on the strength at the failure. This paper studies the effect of the openings on the beams subjected to repeated loading and determine the extent of the increase in the strength of the beams when strengthened by the NSM technique. The experimental program included casting and testing fifteen RC beams, six of them considered as a control beams (three with strengthening and three without strengthening), and nine of them having circular transverse openings in different locations and strengthened by the NSM technique. Every type of beams is tested under three different types of loads (monotonic, constant repeated load, and incremental repeated load). All of the beams have the same dimensions and same reinforcement. The results show that all the beams with transverse openings are affected by repeated loads where the ultimate torque decreases and the twist angle increases. The existence of openings has a noted effect on reducing the ultimate torque, whereas the percentage of decrease in the ultimate torsional capacity reached 43.83% at the beam where the opening location is closest to the support (at the quarter of the clear span) and subjected to constant repeated loads, and the ultimate torque is significantly improved when the opening position is moved away from the supports. Also, the existence of strengthening reduced or eliminated the influence of openings on the ultimate torque compared with related non- strengthened beams.

Numerical nonlinear analysis of RC beans with un-strengthened and CFRP-strengthened opening drilled under service loads within shear zones

Current research paper deals with reinforced concrete (R.C.) beams numerical modeling and suggested strengthening procedure if it is required to create an opening within their shear zones. Strengthening is assumed to be achieved during different service load application conditions. Reinforced Concrete beams with rectangular or circular opening in shear zone; as critical regions; sustain two concentrated system of loads are tested till failure before and after performing suggested opening assessing technique by means of Carbon Fibers Reinforced Polymer sheets (CFRP). The main aim of this research is simulating real practice situation where the beam is subjected to service loads, supported temporary by means of hydraulic jacks, opening is created and strengthening is performed then jacking supports are released. Results of achieved numerical nonlinear modeling are introduced and influence of strengthening achieving on improving assessed beams almost structural behavior such as initial cracking loads, load deflection curves, cracking patterns, failure loads & modes for reference (without opening), main un-strengthened control beams, and CFRP strengthened opening beams are introduced and analyzed in details. Some important conclusions & recommendations for designer and executive engineers are stated.

Вплив включення із функціонально-градієнтного матеріалу на концентра-цію напружень в тонких пластинах та циліндричних оболонках з круговим отвором

ology, in particular, space-rocket engineering, oil-and-gas engineering, power engineering, construction, etc. The presence of openings in their plate and shell components leads to a sharp increase in local stresses, which, under certain conditions, may trigger destructive processes. The use of functionally graded materials (FGMs) with certain mechanical properties can significantly reduce the stress concentration in the vicinity of local concentrators in the form of openings, cutouts, fillets, grooves, etc. This paper presents the results of computer simulation and finite element analysis of the stress and strain fields of thin plates and thin-walled cylindrical shells with a circular opening and an annular FGM inclusion surrounding it. The effect of the dimensions of the FGM inclusion and the law of variation of its elastic modulus on the stress and strain concentration in the vicinity of the opening was studied. The stress and strain intensity distribution in local stress concentration zones was obtained. It was found that an annular FGM inclusion with certain mechanical properties can reduce the stress concentration factor by more than 30%. In this case, a proportional decrease in strain intensity in the vicinity of the opening is also observed. The law of variation of the elastic modulus of the FGM inclusion and the inclusion width have a significant effect not only on the level of stress and strain concentration, but also on the stress and strain pattern. The results of the large-scale computational experiments show that an FGM annular inclusion reduces both the stress and the strain intensity around the opening. Therefore, the use of annular FGM reinforcements in plates and cylindrical shells with openings makes it possible to control the distribution and magnitude of the stress and strain intensities in local stress and strain concentration zones.

Shear behavior of I-section steel with circular web opening and novel reinforcement

For reinforcement of circular web opening in I-section steel beams, half-ring plates of novel configuration were proposed considering the economy and structural performance. To verify the proposed method, cyclic loading tests were conducted for cantilever beams with a single web opening and low shear-span ratio. The test parameters were opening diameter-to-beam depth ratio and degree of reinforcement. The test results showed that the shear behavior of I-section steel was significantly affected by web opening of standard and small diameters (= 50% and 33% of the beam depth, respectively). On the other hand, properly designed ring plates strengthened the perforated beams to exhibit the plastic capacity of solid I-section, restraining the double-curvature flexural mode of web opening (i.e., the Vierendeel mechanism). The proposed ring plates were effective not only in enhancing the flexure-shear strength of the perforated beams, but also in ensuring large inelastic deformation, irrespective of design parameters. The test results, such as the overall load-displacement relationships and buckling modes, were successfully captured by finite element analysis using Abaqus. An existing analytical model for the flexure-shear interaction capacity of the circular web opening was modified to account for the proposed reinforcement method. The predictions conservatively estimated the test strengths.

Elastic buckling of simply supported stiffened steel plates with circular opening

Steel plates are used as the main components of steel elements in many structures. Openings in steel elements may exist for maintenance or inspection purposes in addition to creating paths for different fixtures such as air conditioning, pipes, and facilities. The structural performance of plates with openings is different from that of solid plates when subjected to axial compressive load. Openings affect local buckling, lateral torsional buckling, and shear of plates. Adding stiffeners around openings is a common engineering practice to strengthen plates. However, different design codes and guides provide estimates of the flexural and shear capacity of beams with no clear formulas for the influence of such openings on axial buckling strength. In this study, a parametric study has been performed using general-purpose finite element software, ANSYS, in order to study the effect of using stiffeners around circular opening in simply supported axially loaded plates on the elastic buckling behavior. Different parameters were considered including the aspect ratio of the plate, opening diameter, opening position in both horizontal and vertical directions, and stiffener’s dimensions. The results of the extensive parametric study are used to propose an empirical design formula considering the different studied parameters.

Mechanotransduction in the pathogenesis of non-alcoholic fatty liver disease.

Mechanobiology is a domain of interdisciplinary research that aims to explore the impact of physical force, applied externally or internally, on cell and tissue function, including development, growth, and differentiation. Mechanotransduction is a term that describes how cells sense physical forces (such as compression, stretch, and shear stress), convert them into biochemical signals, and mount adaptive responses integrated by the nucleus. There is accumulating evidence that mechanical forces extensively inform the biological behaviour of liver cells in health and disease. Recent research has elucidated many cellular and molecular mechanisms involved in this process including the pleiotropic control and diverse effects of the paralogous transcription co-activators YAP/TAZ, which play a prominent role in mechanotransduction. The liver sinusoids represent a unique microenvironment in which cells are exposed to mechanical cues originating in the cytoskeleton and at interfaces with adjacent cells, the extracellular matrix, and vascular or interstitial fluids. In non-alcoholic fatty liver disease (NAFLD), hepatocellular lipid accumulation and ballooning, activation of inflammatory responses, dysfunction of liver sinusoidal endothelial cells, and transdifferentiation of hepatic stellate cells into a pro-contractile and pro-fibrotic phenotype have been associated with aberrant cycles of mechanosensing and mechanoresponses. The downstream consequences of disrupted mechanical homeostasis likely contribute to the progression of NAFLD and promote the development of portal hypertension, cirrhosis, and hepatocellular carcinoma. Identification of molecular targets involved in pathogenic mechanotransduction will allow for the development of novel strategies to prevent the progression of liver disease in NAFLD.

Evaluation of input geological parameters and tunnel strain for strain-softening rock mass based on GSI

The regression analysis method is being widely adopted to analyse the tunnel strain, most of which ignore the strain-softening effect of the rock mass and fail to consider the influence of support pressure, initial stress state, and rock mass strength classification in one fitting equation. This study aims to overcome these deficiencies with a regression model used to estimate the tunnel strain. A group of geological strength indexes (GSI) are configured to quantify the input strength parameters and deformation moduli for the rock mass with a quality ranging from poor to excellent. A specific semi-analytical procedure is developed to calculate the tunnel strain around a circular opening, which is validated by comparison with those using existing methods. A nonlinear regression model is then established to analyse the obtained tunnel strain, combining twelve fitting equations to relate the tunnel strain and the factors including the support pressure, GSI, initial stress state, and critical softening parameter. Particularly, three equations are for the estimation of the critical tunnel strain, critical support pressure, and tunnel strain under elastic behaviour, respectively; and the other nine equations are for the tunnel strain with different strain-softening behaviours. The relative significance between the GSI, the initial stress and the support pressure on the tunnel strain is assessed.

Electrical and Structural Properties of Two-Inch Diameter (0001) α-Ga2O3 Films Doped with Sn and Grown by Halide Epitaxy

Two-inch diameter α-Ga2O3 films with thickness ∼4 μm were grown on basal plane sapphire by Halide Vapor Phase Epitaxy (HVPE) and doped with Sn in the top ∼1 μm from the surface. These films were characterized with High-Resolution X-ray Diffraction (HRXRD), Scanning Electron Microscope (SEM) imaging in the Secondary Electron (SE) and Micro-cathodoluminescence (MCL) modes, contactless sheet resistivity mapping, capacitance-voltage, current-voltage, admittance spectra, and Deep Level Transient Spectroscopy (DLTS) measurements. The edge and screw dislocations densities estimated from HRXRD data were respectively 7.4 × 109 cm−2 and 1.5 × 107 cm−2, while the films had a smooth surface with a low density (∼103 cm−2) of circular openings with diameters between 10 and 100 μm. The sheet resistivity of the films varied over the entire 2-inch diameter from 200 to 500 Ω square−1. The net donor concentration was ∼1018 cm−3 near the surface and increased to ∼4 × 1018 cm−3 deeper inside the sample. The deep traps observed in admittance and DLTS spectra had levels at Ec−0.25 eV and Ec−0.35 eV, with concentration ∼1015 cm−3 and Ec−1 eV with concentration ∼1016 cm−3.

Ultrastructure of the palatine tonsils of the donkey (Equus asinus): New insights by light, scanning, and transmission electron microscopy.

The study aimed to explore the ultrastructure of the donkeys' palatine tonsils. Palatine tonsils of five male donkeys (5 years old) were investigated macroscopically and microscopically. The tonsils appeared as a dome shape with slight elevation and a circular opening on the surface of the oropharynx. The central tonsillar crypt appeared on the medial side of the palate-pharyngeal folds and the floor of the oropharynx. The external surface of the palatine tonsil had different sizes of mucosal folds, some grooves directed to drainage at the tonsillar opening, and the tonsil crypt opening was a crescentic or irregular oval shape. The outer surface was covered by stratified squamous epithelium and modified to be reticular epithelium invaded by lymphocytes in the crypt called lympho-epithelium. The tonsil crypt had aggregated lymphoid nodules, and the cryptal epithelium has surrounded by diffused lymphocytes and hassles corpuscles-like structures. The lymphocytes infiltrated into different layers of the cryptal epithelium and transformed into reticular or lympho-epithelium. The organized lymphoid nodules were primary and secondary, and the secondary ones had a light germinal center. The interfollicular area had many high endothelial venules and blood capillaries. The endothelial venules were lined by simple cuboidal epithelium and had lymphocytes. The blood capillaries had red blood cells and neutrophils. The tonsil was surrounded incompletely by a connective tissue capsule with mucous glands under that capsule. In conclusion, the epithelial lymphocyte infiltration, crypt epithelium, lymphoid nodules, and intra-follicular area of the donkey's palatine tonsils indicate the humoral and cell-mediated immunological process.

Cavitation in a periodontal pocket by an ultrasonic dental scaler: A numerical investigation

Periodontal pockets are spaces or holes surrounded by teeth under the gum line. These pockets can become filled with infection-causing bacteria resulting in tissue, bone, and tooth loss. Cavitation produced by the oscillating tip of dental ultrasonic scalers plays a significant role in routine periodontal therapy to clean these areas. Numerical studies were conducted for a scaler vibrating in a periodontal pocket which was simplified to a hole, using ABAQUS based on the finite element method. The simulations consider the three-dimensional, nonlinear, and transient interaction between the vibration and deformation of the scaler tip, the water flow around the scaler and the cavitation formation. The numerical model was validated by comparing results with experimental data for a scaler vibrating in an unbounded liquid, the displacement at the free end of the scaler and the cavitation pattern near the scaler tip displaying excellent agreement. A parametric study for a scaler vibrating in a hole has been carried out in terms of the volume of the hole, the taper ratio (the radius ratio between the circular opening and bottom of the hole), and the immersion depth of the scaler tip in the hole. The amount of cavitation generated is evaluated by the cavitation density (or the void fraction) which is the ratio of the volume of the cavitation occupied in the hole to the total volume of the hole. Numerical results indicate that the cavitation density in the hole increases with the decreasing hole volume and the increasing taper ratio. It is inferred that cleaning effects could be increased if some modifications to the scaler design could be made to increase the blocking effect of the hole during the cleaning process. Cavitation is observed in the hole even if the scaler is placed above the hole and increases with the immersion depth.

Numerical study of fracture failure nature around the circular and horseshoe openings using the bonded-particle model

SUMMARY Rock failure is a process of the rapid release of energy. The energy release can generate a transient elastic wave. This phenomenon is named acoustic emission (AE) that can provide a wealth of information regarding the failure process. To get a better understanding of failure mechanism in rocks, several criteria had been proposed and widely used to distinguish the failure nature of fractures based on the AE information. Due to these criteria are based on different theories, sometimes they may obtain different results from the same failure source. To analyse the application of these distinguished criteria, a series of uniaxial compressive tests were carried out on granite rocks containing a circular/horseshoe opening by using bonded-particle model combined with the AE technique. Cracking sequences and failure pattern of numerical simulations are comparable with those of laboratory tests. By discussing the force distribution, displacement field and the forces acting on the failure sources of numerical study, the results indicate that the crack path initiating from the top and bottom of the opening is tensile in nature. The shear and compressive AE events are predominant at the lateral sides of the opening. Three criteria can well distinguish the tensile failure. While the Ohtsu's criterion cannot distinguish the compressive failure effectively. The Feignier and Young's criterion and Ming's criterion are recommended to studying the cracking process and failure nature of rocks.

Mechanism of improvement in the shear performance of RC beams due to multiple small transverse openings

This paper evaluated the improvement effect of multiple small circular transverse openings (diameter is 1/10 of member height) on the shear performance of RC beams without shear reinforcement and explained the shear resistance mechanism, using three dimensional Rigid-Body-Spring-Method (3D RBSM). First, 3D RBSM was employed to reproduce the shear loading test on the RC beams with multiple small circular transverse openings, and the contributions of beam and arch actions to the shear resistance at each loading stage was evaluated. The analytical load-deflection relationship and cracking behavior were in good consistent with the experiment, and it was noted that the connecting line of the opening centers (line of openings) could control the path of critical diagonal crack, and transfer the failure mode of one of the beams from the diagonal tension pattern to the shear compression pattern. Moreover, the shear strength and ultimate deflection of this beam with openings were significantly improved due to the increase in the shear resistance contribution of arch action. Furthermore, the analysis of additional cases with three transverse openings at each shear span were conducted aiming to explore the possibility that a proper setting of openings can reliably improve the shear performance of RC beams. The line of openings was on a straight line and passed through the loading point at the same side, and the main parameter was set as the angle of the line of openings to beam axis (25°-50°). As a result, the role of the transverse openings in improving the shear performance was confirmed and the corresponding mechanism was explained based on the investigation on the beam and arch actions and crack behaviors.

Estimating the Buckling Load of Steel Plates with Center Cut-Outs by ANN, GEP and EPR Techniques

Steel plates are used in the construction of various structures in civil engineering, aerospace, and shipbuilding. One of the main failure modes of plate members is buckling. Openings are provided in plates to accommodate various additional facilities and make the structure more serviceable. The present study examined the critical buckling load of rectangular steel plates with centrally placed circular openings and different support conditions. Various datasets were compiled from the literature and integrated into artificial intelligence techniques like Gene Expression Programming (GEP), Artificial Neural Network (ANN) and Evolutionary Polynomial Regression (EPR) to predict the critical buckling loads of the steel plates. The comparison of the developed models was conducted by determining various statistical parameters. The assessment revealed that the ANN model, with an R2 of 98.6% with an average error of 10.4%, outperformed the other two models showing its superiority in terms of better precision and less error. Thus, artificial intelligence techniques can be adopted as a successful technique for the prediction of the buckling load, and it is a sustainable method that can be used to solve practical problems encountered in the field of civil engineering, especially in steel structures.

Experimental investigations on passive direct methanol fuel cell using variable membrane electrode assembly dynamic regions by altering gasket shapes

PurposeThe purpose of this paper is to investigate the performance of Passive Direct Methanol Fuel Cell (PDMFC) experimentally using various Membrane Electrode Assembly (MEA) shapes such as square, rectangle, rhombus, and circle with equal areas and equal perimeters. The variation in MEA shape/size is achieved by altering gasket openings in the dynamic regions.Design/methodology/approachIn the equal areas of MEA shapes, gasket opening areas of 1963.5 (+/−0.2) mm2 are used. Whereas in the equal perimeters of shapes, gasket opening perimeters of 157.1 (+/−0.2) mm are used. In this experimentation, Nickel-201 current collectors with 45.3% of circular openings are used on both the anode and cathode sides. The experiment is carried out at a 5 molar methanol concentration to find out the highest power density of the cell.FindingsIn the equal areas, among the shapes that are chosen for investigation, the square shape opening consisting of a perimeter of 177.2 mm has developed a maximum power density of 6.344 mWcm−2 and a maximum current density of 65.2 mAcm−2. Similarly, in equal perimeters, the rhombus shape opening with an area of 1400 mm2 has developed a maximum power density of 7.714 mWcm−2 and a maximum current density of 85.3 mAcm−2.Originality/valueThe novelty of this research work is instead of fabricating various shapes and sizes of highly expensive MEAs, the desired shapes and sizes of the MEA are achieved by altering gasket openings over dynamic regions to find out the highest power density of the cell.

An Improved Capillary Pressure Model for Fractal Porous Media: Application to Low-Permeability Sandstone

Capillary pressure is a crucial input in reservoir simulation models. Generally, capillary pressure measurements are expensive and time-consuming; therefore, there is a limitation on the number of cores tested in the laboratory. Accordingly, numerous capillary pressure models have been suggested to match capillary pressure curves and overcome this limitation. This study developed a new fractal capillary pressure model by depicting the porous system as a bundle of tortuous triangular tubes. The model imitates the pores’ angularity, providing a more accurate representation of the pore system than smooth circular openings. Moreover, triangular tubes allow the wetting phase to be retained in the tube’s corners. A genetic algorithm was employed to match the capillary pressure curves and obtain the proposed model’s parameters. Capillary pressure data of eight low-permeability sandstone samples from the Khatatba formation in the Western Desert of Egypt were utilized to test the proposed model. The results revealed that the developed model reasonably matched the laboratory-measured data.