Resistance Shear Stress Research Articles

Effective Concrete Failure Area for SC Structures Using Stud and Tie Bar Under Performance Tests.

Nuclear power plants, where steel-plate concrete (SC) structures are commonly adopted, require large-scale components to withstand significant loads, such as those caused by sudden explosions. As a result, SC modular members used in nuclear power plants must have thicker walls filled with concrete compared to standard-sized ones. These large walls also require additional components, such as tie bars and H-shaped steel sections, to reinforce adhesion and resist shear stresses. This study focuses on tie bars placed adjacent to studs and evaluates their influence on the tensile strength of wall structures. To investigate this, we conducted experimental tests using full-scale specimens, including various combinations ranging from single stud to combined stud-tie configurations. Based on the results of these performance tests, we propose a design recommendation for estimating the tensile capacity of SC structures, considering the influence of tie bars.

Comparison of airway resistance and wall shear stress between non- and bronchial pattern images in cats by computational simulation

Comparison of airway resistance and wall shear stress between non- and bronchial pattern images in cats by computational simulation

Lateral Shear Stress Calculation Model Based on Flow Velocity Field Distribution from Experimental Debris Flows

AbstractDebris flows continuously erode the channel downward and sideways during formation and development, which changes channel topography, enlarges debris flow extent, and increases the potential for downstream damage. Previous studies have focused on debris flow channel bed erosion, with relatively little research on lateral erosion, which greatly limits understanding of flow generation mechanisms and compromises calibration of engineering parameters for prevention and control. Sidewall resistance and sidewall shear stress are key to the study of lateral erosion, and the distribution of the flow field directly reflects sidewall resistance characteristics. Therefore, this study has focused on three aspects: flow field distribution, sidewall resistance, and sidewall shear stress. First, the flow velocity distribution and sidewall resistance were characterized using laboratory debris flow experiments, then a debris flow velocity distribution model was established, and a method for calculating sidewall resistance was developed based on models of flow velocity distribution and rheology. A calculation method for the sidewall shear stress of debris flow was then developed using the quantitative relationship between sidewall shear stress and sidewall resistance. Finally, the experiment was validated and supplemented through numerical simulations, enhancing the reliability and scientific validity of the research results. The study provides a theoretical basis for the calculation of the lateral erosion rate of debris flows.

The Contrasting Effects of Bothrops lanceolatus and Bothrops atrox Venom on Procoagulant Activity and Thrombus Stability under Blood Flow Conditions.

Consumption coagulopathy and hemorrhagic syndrome are the typical features of Bothrops sp. snake envenoming. In contrast, B. lanceolatus envenoming can induce thrombotic complications. Our aim was to test whether crude B. lanceolatus and B. atrox venoms would display procoagulant activity and induce thrombus formation under flow conditions. Fibrin formation in human plasma was observed for B. lanceolatus venom at 250-1000 ng/mL concentrations, which also induced clot formation in purified human fibrinogen, indicating thrombin-like activity. The degradation of fibrinogen confirmed the fibrinogenolytic activity of B. lanceolatus venom. B. lanceolatus venom displayed consistent thrombin-like and kallikrein-like activity increases in plasma conditions. The well-known procoagulant B. atrox venom activated plasmatic coagulation factors in vitro and induced firm thrombus formation under high shear rate conditions. In contrast, B. lanceolatus venom induced the formation of fragile thrombi that could not resist shear stress. Our results suggest that crude B. lanceolatus venom displays amidolytic activity and can activate the coagulation cascade, leading to prothrombin activation. B. lanceolatus venom induces the formation of an unstable thrombus under flow conditions, which can be prevented by the specific monovalent antivenom Bothrofav®.

Hormonal Control of Blood Viscosity.

The hemodynamic milieu differs throughout the vascular tree because of varying vascular geometry and blood velocities.Accordingly, the risk of turbulence, which is dictated by the Reynolds and Dean numbers, also varies. Relatively high blood viscosity is needed to prevent turbulence in the left ventricle and aorta, where high-velocity blood changes direction several times. Low blood viscosity is needed in the capillaries, where erythrocytes pass through vessels with a diameter smaller than their own. In addition, higher blood viscosity is necessary when the cardiac output and peak blood velocity increase as a part of a sympathetic response or anemia, which occurs following significant hemorrhage. Blood viscosity, as reflected in systemic vascular resistance and vascular wall shear stress, is sensed, respectively, by cardiomyocyte stretching in the left ventricle and mechanoreceptors for wall shear stress in the carotid sinus.By controlling blood volume and red blood cell mass, the renin-aldosterone-angiotensin system and the systemic vascular resistance response control the hematocrit, the strongest intrinsic determinant of blood viscosity. These responses provide gross control of blood viscosity. Fine-tuning of blood viscosity in transient conditions is provided by hormonal control of erythrocyte deformability. The short half-life of some of these hormones limits their activity to specific vascular beds. Hormones that modulate blood viscosity include erythropoietin, angiotensin II, brain natriuretic factor, epinephrine, prostacyclin E2, antidiuretic hormone, and nitric oxide.

The proteolysis of ZP proteins is essential to control cell membrane structure and integrity of developing tracheal tubes in Drosophila.

Membrane expansion integrates multiple forces to mediate precise tube growth and network formation. Defects lead to deformations, as found in diseases such as polycystic kidney diseases, aortic aneurysms, stenosis, and tortuosity. We identified a mechanism of sensing and responding to the membrane-driven expansion of tracheal tubes. The apical membrane is anchored to the apical extracellular matrix (aECM) and causes expansion forces that elongate the tracheal tubes. The aECM provides a mechanical tension that balances the resulting expansion forces, with Dumpy being an elastic molecule that modulates the mechanical stress on the matrix during tracheal tube expansion. We show in Drosophila that the zona pellucida (ZP) domain protein Piopio interacts and cooperates with the ZP protein Dumpy at tracheal cells. To resist shear stresses which arise during tube expansion, Piopio undergoes ectodomain shedding by the Matriptase homolog Notopleural, which releases Piopio-Dumpy-mediated linkages between membranes and extracellular matrix. Failure of this process leads to deformations of the apical membrane, tears the apical matrix, and impairs tubular network function. We also show conserved ectodomain shedding of the human TGFβ type III receptor by Notopleural and the human Matriptase, providing novel findings for in-depth analysis of diseases caused by cell and tube shape changes.

Water-Adaptive Microcapsules with a Brittle-Ductile-Brittle Transition Based on an O/W/O Emulsion for the Self-Healing of Cementitious Materials.

Cementitious materials inevitably develop cracks, posing a serious threat to the long-term security of infrastructure, especially in the complex underground environment of cementing engineering. Microcapsules are facing the problem of encapsulated structure damage during the mixing and breaking difficultly during self-healing when applied in cementitious materials, resulting in the decline of self-healing efficiency. Herein, the calcium alginate water-adaptive microcapsules (CaAlg-NS/E-51) were prepared via an O/W/O emulsion, and the water adaptability of the shell was applied to achieve a rapid brittle-ductile transition by absorbing water. The water adaptability of the microcapsule is conducive to resisting shear stress during stirring due to the decreased elastic modulus and the increased ductility of the shell when it absorbs water. Meanwhile, the water-bearing shell loses water and becomes brittle during dry curing, making it prone to fracture when self-healing. In the self-healing measurement, the self-healing efficiency of cementitious specimens with microcapsules absorbing water for 10 min improved by 234.9 and 60.0% at 1 and 7 days, respectively, compared with those containing dry microcapsules, owing to the water adaptability of the shell.

Molecular simulation on the mechanical and thermal properties of modified insulating paper cellulose doped with trapezoidal polyphenylsesquisiloxane at different temperature

AbstractWith the further development of the transmission and distribution network, the requirements for the insulating system of power equipment are further deepened. As one of the important factors, insulating paper is of great value to improve its performance. The pure cellulose model and trapezoidal polyphenylsesquisiloxane (T‐PPSQ) composite model are established to analyze the mechanical and thermal properties of insulating paper cellulose. The effects of T‐PPSQ doping at different temperature on properties of cellulose are investigated by comparing the radial distribution function, mechanical parameters, glass transition temperature, mean square displacement (MSD), and free volume fraction (FVF) through molecular dynamics method. The results show that T‐PPSQ can improve the ability of cellulose to resist shear stress at different temperatures, showing good mechanical properties. When the temperature is 423 K, the mechanical performance parameters elastic modulus, bulk modulus and shear modulus can be increased by 47.2%, 18.2%, and 38.56% at most. The glass transition temperature of the insulating paper cellulose with T‐PPSQ increases by 64 K, the MSD and the FVF all decrease at different temperature which demonstrated it has improved thermal stability. The research in this paper is of great significance for improving the life of the insulating system of power equipment.

Equivalent seismic behaviors of artificial frozen-thawed soft clay with a new reduction factor of shear stress

The artificial ground freezing (AGF) technique is widely used in the construction of underground structures, and the deformation of soft clay is more significant after freezing-thawing cycles. Moreover, many earthquake disasters indicate that the engineering in soft soil areas experience huge risks to seismic fortification. In this paper, the inversion formula of seismic acceleration time history for different peak ground accelerations (PGAs) in the frequency domain was derived. The maximum peak acceleration and maximum dynamic shear stress in the undisturbed and frozen-thawed soft clay sites were analyzed by DEEPSOIL. The reduction factor of dynamic shear stress suitable for the clay field was calculated to provide basic parameters for the cyclic triaxial tests considering different confining pressures, dynamic stress amplitudes and loading frequencies. The ground motion acceleration of soft clay sites has an amplification effect, and that of frozen-thawed soft clay sites is more obvious. The reduction factor of shear stress for the clay site is overestimated by the liquefaction resistance shear stress method. The axial strain of the frozen-thawed clay reaching failure is less than that of the undisturbed clay. Under the same seismic shear stress, the development of the excess pore water pressure in frozen-thawed clay is more significant than that in undisturbed clay.

Computational fluid dynamics model of laryngotracheal stenosis and correlation to pulmonary function measures

3D models of airway lumens were created from CT scans of 19 patients with laryngotracheal stenosis. Computational fluid dynamics (CFD) simulations were completed for each, and results were compared to measured peak inspiratory flow rate, grade of lumen constriction, and measures of airway geometry. Results demonstrate flow resistance and shear stress correlate with degree of lumen constriction and absolute cross-sectional area as well as flow rate. Flow recirculation depends on airway constriction but does not vary with flow rate. Resistance and wall shear stress did not correlate well with functional measures. Flow recirculation did differ between subjects with higher functional measures and subjects with lower functional measures. This analysis provides mathematical models to predict airway resistance, wall shear stress, and flow reversal according lumen constriction and inspiratory flow rate. It suggests aerodynamic factors such as flow recirculation play a role in differences in functional performance between patients with similar airway measures.

New approach to establish a surgical planning in infantile vallecular cyst synchronous with laryngomalacia based on aerodynamic analysis

Background and objectivesA large proportion of infants with vallecular cyst (VC) have coexisting laryngomalacia (LM). Feeding difficulties, regurgitation, occasional cough, and sleep-disordered breathing are the common symptoms in moderate to severe cases. The surgical management of these cases is more challenging and remains controversial. The purpose of this study is to help surgeons select the effective surgical strategies by computer-aided design (CAD) and computational fluid dynamics (CFD) simulations of the upper airway flow characteristics. MethodsThe three dimensional (3D) geometric model of the upper airway was reconstructed based on two dimensional (2D) medical images of the patient with VC accompanied with LM. Virtual surgeries were carried out preoperatively to simulate three possible post-operative states in silico. The different outcomes of virtual surgical strategies were predicted based on computational evaluations of airway fluid dynamics including pressure, resistance, velocity, and wall shear stress (WSS). ResultsThe CFD results of this study suggested the importance of the angle between the rim of epiglottis and arytenoid epiglottic (AE) fold. There was a small impact on the upper airway flow field while the VC was removed and the angle of epiglottis was unchanged. The partial lifting of epiglottis can further improve the flow field. With performing supraglottoplasty (SGP) and the marsupialization of VC, epiglottis was completely recovered, and the flow field was significantly improved. The clinical symptoms of this patient improved greatly after surgeries and no recurrence or growth retardation were noted during 1-year follow-up. The clinical prognosis was consistent with the prediction of the CFD results. ConclusionsThe state of epiglottis needs to be carefully checked to evaluate the necessity of performing further SGP in the patients with VC accompanied with LM. CFD and CAD could be developed as a new approach to help surgeons predict the post-operative outcomes through quantification of the airflow dynamics, and make the optimal and individualized surgical approaches for patients with airway obstruction.

Determine the Response of Structural and Mechanical Properties to Heat Treatment For (PMMA) Matrix Reinforcement By (Al2o3) Powder

Poly (methyl methacrylate) (PMMA) was used as a matrix for fabrication samples of polymer matrix composites (PMCs). The matrix was reinforcement by (Al2O3) powder with a volumetric ratio (20%) and an average grain size (40 ±5) μm. The manufactured samples were treated after conducting the surface treatment operations thermally with different temperatures (50,70 and 90 ⁰C) and with different treatment times (2,4,6,8, and 10 hours). The samples were subjected to a set of mechanical and microscopic tests, whereby the effect of thermal treatment on the bending fatigue life of the manufactured samples, and the effect of thermal treatment on the ability of the material to resist shear stress, flexural strength, wear, compressive resistance and impact resistance. The results showed that there was an improvement in fatigue life, shear stress, flexural strength, compressive strength, wear resist, and impact resistance after heat treated samples. The best fatigue life, shear resistance, wear resist, and flexural strength occurred for 6 hours post cure time, while it was observed that the best improvement in compressive resistance and impact resistance occurred after the passage of (4hours) of the post cure time. The results also showed that the best thermal treatment temperature is (T=70⁰C).

Stability Evaluation of Reinforced Slope Soil with Vetiver Grass against Erosion and Landslides Hazards by Using Finite Element Method

This work studied slopes with different geometric situations. The purpose is to select types of soil for embankment construction to stabilise the site by using nearby accessible filling materials. Then, PLAXIS-2D software was used including five (6) phases of sequential calculation such as soil, structure, mesh generation, conditions of flow and construction stage and the use of Vetiver grass for embakment stability reinforcement. Choices were made on soil properties, loading, water table effect, embankment geometry and reinforcement actions of vetiver grass. The method is based on using diverse filling materials and varied slope gradients with different heights. So, the slope analyse involves homogeneous soils, in addition to slope section by various soils strata. Results obtained showed that the increase in soil shear strength is related to the mechanical effects of vetiver roots and make the soil able to resist shear stress due to the presence of roots density within the soil mass and the root tensile strength. It is also noticed that the soil suction effects and roots reinforcement increased the apparent cohesion of the soil, showing an important role played by vetiver grass in stabilising shallow-seated slopes failure with significant effect on slopes stability.

Study of Shear Transfer in Modified Push-Off Members Using Finite Elements Method

This paper aims to investigate numerical study onto the behavior of modified push-off specimens under the action of direct shear stress. Based on the tow-dimensional finite element model developed in this research, the contribution of the aggregate interlock to resist the shear stress along the shear plane, the effect of existing of the compressive stress acting across the shear plane, the effect of the parallel reinforcement in resisting shear stress, the effect of the shear reinforcement parameter, the strains in the concrete and steel and the actual distribution of the shear stress along the shear plane were studied. To verify the accuracy and applicability of the suggested finite element model, a comparison between the results obtained in this study and those obtained experimentally by other authors was carried out. Comparison showed that the finite element results were in good agreement with the experimental results. It has been found that, for modified push-off specimens of groups without shear reinforcement across the shear plane the diagonal tension crack within the shear plane occurred at the load level which is closely to the ultimate shear strength respectively, while for specimens with both shear and parallel reinforcement , the first crack formed at about (33.7% - 53.0%) of the ultimate strength , also the investigation showed that the presenting of the shear reinforcement normal to the shear plane are significantly increased the shear transfer stress for all levels of loading.

An Investigation on Local Shearing Mechanisms of Irregular Dentate Rock Joints Using the PFC

Joint surfaces are widely distributed in natural rock mass, and their shear mechanical properties play an important role in determining the safety and stability of rock mass. Previous studies rarely discussed the contribution degree of different joint protrusions to resisting shear stress. In this study, seven irregular dentate joint profiles were proposed to represent the geometric morphology of natural joints. Joint samples were subjected to direct shear tests under constant normal stress using the particle flow code (PFC). First, the reliability of the research scheme was verified by routine test results. Secondly, based on the microcrack tracking module and the force chain analysis, the local failure modes of the joint sample after and during the shearing process are discussed in detail. The relationship between the shear stress and the number of microcracks was studied. Finally, based on the measuring circle function, the variation law of the mean stress at different joint protrusions during the shearing process was tracked. The maximum stress of each protrusion before the shear stress peak was introduced to quantitatively describe the contribution of local protrusions to shear stress. There was an important link between the size of the protrusion and the stress it can withstand. During the shearing process, the local shearing mechanism of the joint surface is controlled by the distribution of joint protrusions. The research results of this paper can provide a good idea for the follow-up joint surface research.

Thermal effects of two immiscible fluids through a permeable stenosed artery having nanofluid in the core region

AbstractA theoretical investigation of two‐layered fluid flow in a stenosed tube having permeable walls is studied. The fluid (blood with nanoparticles) within the core region behaves as a non‐Newtonian fluid (nanofluid) and the fluid within the peripheral layer behaves as a Newtonian fluid. Flow equations are linearized considering mild stenoses. The closed form mathematical expressions for flow resistance and wall shear stress are computed. The problem is solved using HPM (homotopy perturbation method). The numerical calculations of flow parameters (like flow resistance, wall shear stress) are performed and are discussed graphically. A novel result is found that with increased permeability and viscosity, the resistance of the fluid flow and shear at the wall is found to decrease. Moreover, the velocity profiles are increasing in the radial direction with the enhancement of viscosity of the fluid in the peripheral layer but decrease with permeability. Streamlines are drawn to examine the flow pattern.

Sustainable concrete pavements for low volume roads-Scientometric analysis of the literature

Developing countries like India invest huge amounts of money for the construction and maintenance of different roads which includes all types of roads. In this research paper a critical review of literature on sustainable pavements for low volume roads was made using sustainable materials for paving Ultra-thin white topping concrete overlays sustainable new pavements like Pervious concrete pavements, Roller compacted concrete pavements, Cell filled concrete pavements, Self-Compacting Concrete (SCC) Pavement and additional discussion on energy harvesting pavements done. Ultra-thin white topping concrete overlay has better-proven performance but interface bond strength is very critical to resist shear stresses which cause debonding of composite concrete layers. The porous cement or bituminous concrete helps to recharge the groundwater reducing the heat islands and makes nature eco-friendly but on the other hand clogging effect can retain the water in the pavement and causes failure of the pavement. Roller compacted concrete pavement, Self-Compacting Concrete (SCC) Pavement and cell-filled concrete pavements are good in terms of performance disadvantages are less. The Indian standard code should be developed to implement energy harvesting pavements that help to produce electrical energy which meets the need of society. Further Scientometric analysis of sustainable concrete pavements for low volume roads done using VOS viewer software and the database of research work from Dimensions software. From the research gap in keyword occurrences on this topic, it is observed that rice husk ash, recycled aggregate, aluminum dross and fatigue, modulus of elasticity has a wide gap indicating further research on the combination of these key words make sustainable concrete pavements further discussed regarding high impact research papers published, similarly countries were discussed in detail.

Fire resistance of a fully concealed, moment-resisting new timber connection utilizing mechanically-fastened steel rods

One major hindrance to more utilization of timber in the construction of tall buildings is the limited fire resistance of the connections between its structural elements. In an experimental study that aimed to investigate the structural behaviour of a new connection configuration that utilizes fully concealed, mechanically fastened steel rods, eight (8) full-size glued-laminated timber beam-end connections were tested under the CAN/ULC-S101 standard time-temperature curve. Test variables investigated in this study included rod anchorage length (200 and 250 mm) and washer size (38.1 × 38.1 and 50.8 × 50.8 mm). Results show that using the smaller washer provided more wood side cover to protect the steel components from the effects of elevated temperatures. Also, utilizing longer rod anchorage length provided larger internal surface area of the wood prism to better resist shear stresses as well as longer length for the rods to bear against the wood at high rotation values of the connection. By combining the said two aspects (longer anchorage length and smaller washer) a fully concealed glulam beam-end connection that utilizes only two mechanically-fastened steel rods can be successfully designed to achieve a 1-h fire resistance without the application of additional fire protection.

Challenges in Modeling Hemodynamics in Cerebral Aneurysms Related to Arteriovenous Malformations.

The significantly higher incidence of aneurysms in patients with arteriovenous malformations (AVMs) suggests a strong hemodynamic relationship between these lesions. The presence of an AVM alters hemodynamics in proximal vessels by drastically changing the distal resistance, thus affecting intra-aneurysmal flow. This study discusses the challenges associated with patient-specific modeling of aneurysms in the presence of AVMs. We explore how the presence of a generic distal AVM affects upstream aneurysms by examining the relationship between distal resistance and aneurysmal wall shear stress using physiologically realistic estimates for the influence of the AVM on hemodynamics. Using image-based computational models of aneurysms and surrounding vasculature, aneurysmal wall-shear stress is calculated for a range of distal resistances corresponding to the presence of AVMs of various sizes and compared with a control case representing the absence of an AVM. In the patient cases considered, the alteration in aneurysmal wall shear stress due to the presence of an AVM is considerable, as much as 19 times the base case wall shear stress. Furthermore, the relationship between aneurysmal wall shear stress and distal resistance is shown to be highly geometry-dependent and nonlinear. In most cases, the range of physiologically realistic possibilities for AVM-related distal resistance are so large that patient-specific flow measurements are necessary for meaningful predictions of wall shear stress. The presented work offers insight on the impact of distal AVMs on aneurysmal wall shear stress using physiologically realistic computational models. Patient-specific modeling of hemodynamics in aneurysms and associated AVMs has great potential for understanding lesion pathogenesis, surgical planning, and assessing the effect of treatment of one lesion relative to another. However, we show that modeling approaches cannot usually meaningfully quantify the impact of AVMs if based solely on imaging data from CT and X-ray angiography, currently used in clinical practice. Based on recent studies, it appears that 4D flow MRI is one promising approach to obtaining meaningful patient-specific flow boundary conditions that improve modeling fidelity.

Septal deviation in the nose of the longest faced crocodylian: A description of nasal anatomy and airflow in the Indian gharial (Gavialis gangeticus) with comments on acoustics.

The remarkably thin rostrum in the Indian gharial (Gavialis gangeticus) imparts challenges to nasal physiology. Competition for space in the slim jaws necessitates a thin nasal septum, leaving this taxon susceptible to nasal passage abnormalities such as septal deviation. Here we describe the nasal anatomy of gharials based on multiple individuals including one that showcases an extreme instance of nasal septum deviation. We found that gharials have both confluent nostrils and choanae, which may be important for their unique nasal acoustics. The deviated nasal septum in the female showed distinct waviness that affected the nasal passages by alternately compressing them. We performed a computational fluid dynamic analysis on the nasal passages to visualize the effects of septal deviation on airflow. Our analysis found the deviated septum increased nasal resistance and wall shear stress during respiration, resulting in unequal distribution of the air field between both sides of the nasal passage. Our findings indicate that gharials—and potentially other longirostrine crocodylians—may be particularly susceptible to septal deviations. Lastly, we observed pterygoid bullae to be present in both sexes, though their morphology differed. Airflow in the male pterygoid bullae produced a Bernoulli effect which may be responsible for the unique “pop” sounds recorded in this species.