Results Of Numerical Analysis Research Articles

Experimental and Numerical Research of Post-Tensioned Concrete Beams.

The purpose of this paper is to present a new approach for the modelling of post-tensioned beams with calibration of the FE model to experimental results until the load capacity and post-critical state are reached. Two post-tensioned beams with different nonlinear tendon layouts were analysed. Material testing for concrete, reinforcing steel and prestressing steel was performed prior to the experimental testing of the beams. The Hypermesh program was used to define the geometry of the spatial arrangement of the finite elements of the beams. The Abaqus/Explicit solver was used for numerical analysis. The concrete damage plasticity model was used to describe the behaviour of concrete with different laws of elastic-plastic stress-strain evolution for compression and tension. Elastic-hardening plastic constitutive models were used to describe the behaviour of steel components. An effective approach to modelling the load was developed, supported by the use of Rayleigh mass damping in an explicit procedure. The presented model approach ensures good agreement between numerical and experimental results. The crack patterns obtained in concrete reflect the actual behaviour of structural elements at every loading stage. Random imperfections found during experimental studies on the results of numerical analyses were also discussed.

Examination of air flow characteristics over an open rectangular cavity between the plates

Air flow characteristics of an open cavity have been numerically examined by using different turbulence models of Detached Eddy Simulation (DES), k-ε Realizable, k-ω Shear Stress Transport (SST) and Large Eddy Simulation (LES) based on an experimental study of open literature. Numerical results of transient analyses have been compared to experimental results at cavity length-based Reynolds number of Re = 4600. Pressure distributions, streamline patterns, streamwise velocity components, mean velocity values and their vectors have been given in terms of contour graphics. Moreover, velocity profiles have been presented. Pressure fluctuations have been triggered by flow separation and its reattachment. Due to upstream separation of boundary layer, there was curved boundary layer obtained between the outer potential-flow-like and the recirculation zones. As a result, negative velocity values are evidence for rotational flows affected by formation of secondary flows in the cavity. Furthermore, lower pressure region has been observed as a result of rotational flow which was powerful in the open cavity. Numerical results of DES and LES turbulence models are in good agreement with the results of reference study. As the numerical results obtained by LES turbulence model are approximately same with those of experimental reference study, LES turbulence model is mostly recommended. As an option to these turbulence models, k-ω SST model could be utilized for limited computer capacity. However, k-ε Realizable model is not sufficient for capturing rotational flows which are very effective in terms of present case.

An energy stable incompressible SPH method with consistent solid boundary treatment

We propose two novel solid wall boundary treatments on the energy-stable Smoothed Particle Hydrodynamics (SPH) method for the Navier–Stokes system which models single-phase incompressible flows. In this work, the solid wall is discretized with dummy particles, and an external force is introduced to restrict the motion of solid particles, whose physical significance and numerical necessity are analyzed. We construct consistent fluid–solid coupling schemes based on the approaches so that the boundary condition is involved in the same equations system with particular constraints. Furthermore, the schemes are unconditionally energy-stable, which allows large time step sizes and leads to efficient computation. A variety of examples are demonstrated to verify the corresponding numerical analysis result, which shows that the approaches can easily handle no-slip and moving boundaries. Finally, we highlight that the energy-stable ISPH with consistent boundary treatments greatly benefits solving long-term problems with steady states.

Numerical Analysis Results of Debonding Damage Effects for an SHM System Application on a Typical Composite Beam

In the aeronautical field, the damage that occurs to a carbon-fibre-reinforced polymer (CFRP) structure analysis is a crucial point for further improving its capability and performance. In the current the state of the art, in fact, many issues are linked to the certification process more than to technological aspects. For the sake of clarity, it should be added that regulations call for technological solutions that are invasive (in terms of weight and manufacturing costs) or exploit technologies that are not fully mature. Thus, the truth is in between the above statements. One of the possible solutions to bypass this issue is the assessment of a structural health monitoring system (SHM) that is sufficiently reliable to provide a full-state representation of the structure, automatically, perhaps in real-time, with a minimum intervention of specialized technicians, and that can raise an alert for safe maintenance whenever necessary. Among the different systems that have been proposed in the scientific and technological literature, SHM systems based on strain acquisitions seem very promising: they deduce the presence of flaws by analysing the variations of the intimate response of the structure. In this context, the SHM using fibre optics, supported by a dedicated algorithm, seems to be able to translate the effects of the damage reading the strain field. This means that is necessary to have a full comprehension of the flaws’ effects in terms of strain variation to better formulate a strategy aimed at highlighting these distortions. It should be remarked that each type of damage is distinct; imperfections of the bonding line are herein targeted since the quality of the latter is of paramount importance for ensuring the correct behaviour of the referred structure. This presents paper focuses on a deep investigation on the strain field peculiarities that arise after the imposition of irregularities in the adhesive region. The aim is to explore the damage dimension versus its effect on the strain map, especially when bonding connects different parts of a complex composite beam. By means of finite element method applied on a typical aeronautical beam, a parametric numerical simulation was performed in order to establish the influence of a debonding dimension on a reference strain map. This work provides evidence that these effects on strain flaw decrease the distancing itself of the damage. The knowledge of these effects can be highly helpful during the design of a preliminary phase of an SHM system in order to choose the most suitable sensor in terms of reading sensitivity error, the number to be used, and their location.

Experimental and computational study on local buckling of standard and improved cold-formed square hollow sections under static and dynamic loading

Because of aesthetics, economic advantages, easy composite member production and design, and a wide range of standard sizes, hollow sections are commonly utilized in various construction industry applications worldwide, including conventional and unique free-form structures. However, the sections must fulfill more restricted circumstances to avoid early local buckling. The behavior of cold-formed square hollow sections with different wall thicknesses under static and dynamic transverse impact loading was investigated experimentally and numerically in this study. A method that uses rivet nuts is proposed to improve the dominant local buckling behavior, which is observed in the experimental studies and causes a relatively low bending strength, for providing convenience in field applications. The effectiveness of the proposed method is demonstrated experimentally and numerically using finite-element analysis. In addition to conventional measurement techniques, motion analysis is performed using digital image correlation to measure the displacements during static and dynamic tests. With the proposed technique, the local buckling strength of the square hollow sections is increased by 64% under static loading and by approximately 40–85% under dynamic loading compared with standard square hollow sections, respectively. This is due to the internal stiffness plate, steel threaded rods, and rivet nut configuration connecting the flanges and webs of the square hollow section, which ensures load sharing between the section parts. Additionally, steel threaded rods prevent early buckling of the internal stiffness plate. In addition, parametric analysis results show that the thickness of the internal stiffness plate has a negligible effect on the local buckling strength, although the presence of an internal stiffness plate increased the strength. The numerical analysis results indicate that the local buckling behavior of both conventional and improved square hollow specimens can be predicted with acceptable errors in terms of their strength and damage modes using finite-element analysis models.

Research on thermal contact resistance between C/C and resin thermal protection materials for solid rocket motor nozzles considering real surface roughness

C/C composite and resin materials have been applied in rocket motor nozzles. This study aims to investigate the thermal contact resistance (TCR) between C/C composite and resin materials. Contact surfaces are scanned by surface morphological-measuring instrument. The TCR values are solved numerically. With the steady-state heat flux method, the TCR values are experimentally measured at different temperatures and pressures. The study results show that the TCR value between C/C composite and resin materials varies in the range of 1.8245 × 10–3 ∼7.5851 × 10–3 K·m2·W-1 at different pressures and temperatures. The average TCR error between numerical analysis and test results is 8%, which indicates a high accuracy. The developed TCR numerical prediction model can provide a reference for thermal-structural design and analysis of nozzles.

Numerical and clinical analysis of an eyeball injuries under direct impact.

The objective of this study was to develop a numerical model of the eyeball and orbit to simulate a blunt injury to the eyeball leading to its rupture, as well as to conduct a comparative analysis of the results obtained using the finite element method against the clinical material concerning patients who had suffered an eyeball rupture due to a blunt force trauma. Using available sclera biometric and strength data, a numerical model of the eyeball, the orbital contents, and the bony walls were developed from the ground up. Then, 8 different blunt force injury scenarios were simulated. The results of numerical analyses made it possible to identify possible locations and configurations of scleral rupture. The obtained results were compared against the clinical picture of patients hospitalized at the Department of Ophtalmology, Medical University of Gdańsk in 2010-2016 due to isolated blunt force trauma to the eyeball. It has been demonstrated that the extent of damage observed on the numerical model that indicated a possible location of eyeball rupture did not differ from the clinically observed configurations of the scleral injuries. It has been found that the direction of the impact applied determines the location of eyeball rupture. Most often the rupture occurs at the point opposite to the clock-hour/positions of the impact application. The eyeball rupture occurs in the first 7-8 ms after the contact with the striking rigid object. It has been established that the injuries most often affected the upper sectors of the eyeball. Men are definitely more likely to sustain such injuries. Eyeball ruptures lead to significant impairment of visual acuity. This study may contribute to a better understanding of injury mechanisms and better treatment planning. It may also contribute to the development of eyeball protection methods for employees exposed to ocular injuries. Int J Occup Med Environ Health. 2023;36(2):263-73.

Study on Deformation Characteristics of Retaining Structures under Coupled Effects of Deep Excavation and Groundwater Lowering in the Affected Area of Fault Zones

In order to study the deformation characteristics of the retaining structure under the coupled effect of excavation and dewatering in the affected area of fault zones, this paper takes a deep excavation project in the F1322 fault zone influence area in Shenzhen as an example. The research methods of theoretical analysis, numerical simulation and field measurement are used to conduct in-depth research on the deformation of the retaining structure caused by the excavation and dewatering of the foundation pit. The results show that considering the coupled effect of dewatering in the foundation pit, the energy method based on elastic theory is more accurate in solving the deformation of the retaining pile. By comparing and analyzing the theoretical calculation results, numerical analysis results, and field measurement values, we found that the numerical laws of the three are basically the same. Simplified calculations that only consider rotational deformation and ignore the translational deformation of the wall lead to large deviations between the theoretical calculation results and the measured values of the wall bottom deformation. In order to reduce the deviation between numerical results and measured values, the construction of the foundation pit should strictly adopt measures such as “sectional excavation, avoiding peripheral loads, and optimizing construction deployment”, strengthen construction monitoring, and reduce the impact on the deformation of the retaining pile. The maximum deformation growth rate k (ΔSmax/Δ) of the retaining pile decreases approximately exponentially with the increase of the structural stiffness parameters (E and I) and the embedment ratio within a certain range. The sensitivity analysis of the lateral displacement of the retaining pile to different geological parameters is conducted, and the sensitivity factors of the geological parameters to the deformation of the retaining structure are obtained, namely the maximum internal friction angle, followed by the cohesion, and the elastic modulus is the smallest. Based on the original design plan, an optimization of the excavation design is proposed by reducing the stiffness of the support structure. Therefore, the research findings in this paper have significant theoretical and practical implications for the engineering design of excavation projects located in fault zones. By optimizing the excavation support system, not only can standardized construction procedures be achieved, but also investment costs can be reduced, and construction time shortened, which fully aligns with the current safety, economic, and sustainable design principles of excavation projects aiming to conserve resources.

Nonstationary Problems of Heat Conduction for a Thermosensitive Plate with Nonlinear Boundary Condition on One Surface

We propose a method for the determination of temperature fields formed in a plate with regard for the thermal radiation, temperature dependence of thermal characteristics, and densities of surface and volumetric heat sources for a nonuniform distribution of the initial temperature. By using the Kirchhoff transformation, Green’s function, generalized functions, and linear splines, we reduce the problems of heat conduction to the solution of a recurrence nonlinear algebraic equation for the values of the Kirchhoff variable at the spline nodes on the corresponding boundary surface. The results of numerical analysis are presented.

Space Division Multiplexing Using High-Luminance Cell-Size Reduction Arrangement for Low-Luminance Smartphone Screen to Camera Uplink Communication

To simultaneously enhance data rate and physical layer security (PLS) for low-luminance smartphone screen to camera uplink communication, space division multiplexing using high-luminance cell-size reduction arrangement is numerically analyzed and experimentally verified. The uplink consists of a low-luminance smartphone screen and an indoor telephoto camera at a long distance of 3.5 meters. The high-luminance cell-size reduction arrangement avoids the influence of spatial inter-symbol interference (ISI) and ambient light to obtain a stable low-luminance screen. To reduce the screen luminance without decreasing the screen pixel value, the arrangement reduces only the high-luminance cell area while keeping the cell spacing. In this study, two technical issues related to high-luminance cell-size reduction arrangement are solved. First, a numerical analysis and experimental results show that the high-luminance cell-size reduction arrangement is more effective in reducing the spatial ISI at low luminance than the conventional low-luminance cell arrangement. Second, in view point of PLS enhancement at wide angles, symbol error rate should be low in front of the screen and high at wide angles. A numerical analysis and experimental results show that the high-luminance cell-size reduction arrangement is more suitable for enhancing PLS at wide angles than the conventional low-luminance cell arrangement.

Random forest algorithm and support vector machine for nondestructive assessment of mass moisture content of brick walls in historic buildings

The article presents the results of experimental research and numerical analyses, and also shows the usefulness of the random forest algorithm and the support vector machine for the non-destructive identification of the moisture content of brick walls in historic buildings. To train and test the models, a representative dataset, including 290 sample sets and 7 predictor variables, was used. These variables are: Y - describing the year of construction of the building; XD, XM, Um - describing the wall's moisture; XC, XS, XA - describing the concentration of salts in the wall. The analyses showed that the random forest algorithm is the most predisposed model for the non-destructive assessment of the Umc mass moisture content of brick walls in historic buildings. This is proved by the highest value of the R2, amounting to 0.968, and the lowest values of RMSE, MAE and MAPE, amounting to 1.080%, 0.791 and 14.28%, respectively.

Effect of Surface Stresses on the Antiplane Stress-Strain State of a Thin Ribbon-Like Interface Inclusion

On the basis of the theory of functions of complex variable and the method of jump functions, we propose a procedure of taking into account the additional influence of surface stresses in the problem of thin interface inclusion in the bimaterial. In this problem, we take into account the possibility of imperfect contact between the inclusion and the matrix and, in particular, the possibility of contact with surface tension. This significantly extends the field of applicability of the results of simulation within the framework of the concept of representative volume element in micro- and macromechanics. We propose a generalized model of thin inclusion with arbitrary mechanical properties. The analysis of test problems reveals high accuracy and efficiency of the proposed approach. We present the results of numerical analyses of the stress fields in the case of interaction of the inclusion with concentrated forces and screw dislocations.

Performance of Base-Isolated RC School Building under Blast Loading

It is known that bomb-laden vehicles target many buildings as a result of terrorist activities. The effects of such attacks must be reduced and structures must be protected against blast effects. In high seismic hazard regions, buildings are designed to be earthquake resistant. One of the methods used to dampen earthquake effects on structures is base isolation. Base isolation is effective in distributing blast loads to the structure, similar to seismic loading. In this study, the effects of this distribution on the structure will be evaluated. The scope of the study encompasses the numerical estimation of explosive loads at different distances according to the explosive material carrying capacity of various vehicles and their effects on structures. Linear and nonlinear analysis methods were used to compare the dynamic behaviour of school buildings designed with and without base isolators. The Turkish Building Earthquake Code (2018), which includes the maximum seismic loads, was used in the design of the isolators. Numerical analysis was performed using SAP2000 software based on the finite element method. The blast loads were applied to the floors of the building using the direct integration method in the time domain. FEMA standards were used to determine the blast loads and the performance was evaluated in comparison with the numerical analysis results. As a result of the study, it was concluded that structures with base isolators are efficient in reducing the effects of an explosion at certain distances and these distances will affect the design of the shelter walls.

Assessment of Small Diameter Steel Pile as a Stabilizing Element for Transmission Tower Slope Stability

Background: Stabilization of unstable slopes with relatively large reinforced concrete piles has been widely adopted over the past several decades. Small diameter steel piles have several advantages as a slope reinforcement technique for an unstable transmission tower slope where space and access restrictions that typically occur render alternate approaches unfeasible. Methods: In this study, a numerical performance assessment of small diameter steel pile as a stabilizing element for transmission tower slope stability was carried out using an uncoupled analysis, in which the pile response and slope stability are considered separately. Numerical evaluations are presented and the influencing parameters that could affect the behavior of reinforcing piles to increase transmission tower slope stability are investigated. Results: The numerical analysis results indicate that the soil properties, slope geometry, pile location, pile diameter, pile length and number of pile rows have a combined effect on the performance of small diameter steel piles to stabilize transmission tower slopes. Conclusion: The numerical assessment can satisfactorily capture some fundamental response of transmission tower slope reinforced with multi-row small diameter steel piles.

Design, Implementation and Test of a Novel Cylindrical Permanent Magnet DC Linear Motor

Electric motors that convert electrical energy into motion are one of the basic components of automation systems. In these systems, either linear or circular motion is needed. Linear motion can be obtained either from motors that generate circular motion with the help of ancillary equipment or directly by the means of a linear motor. Obtaining linear motion from motors that produce rotary motion leads to additional costs and reduced efficiency. Linear motors, on the other hand, eliminate the need for conversion mechanisms. Despite this advantage, linear motors have some disadvantages, such as length limitation and low force/current ratio. In this study, a novel Cylindrical Direct Current Linear Motor (CDCLM) with high force/current ratio and no length limitation (long stroke) has been developed. Analyses of the developed motor has been performed with an analytical method. In addition, detailed numerical analyses have been carried out in an Ansys-Maxwell environment. A prototype of the designed DC linear motor has been implemented in a laboratory environment and experimental analyses have been carried out. The results of analytical, numerical and experimental analyses have been compared.

Modeling of shear-lap tests of flat and curved masonry specimens strengthened by FRCM

Nowadays Fiber Reinforced Cementitious Matrix (FRCM) systems play a relevant role in the context of innovative interventions for the seismic rehabilitation of masonry structures. Their capacity in improving the strength of masonry components is comparable with the one observed in case of Fiber Reinforce Polymer (FRP) systems, but with additional advantages (lower costs, environmental compatibility, removability, etc.). Nevertheless, although a relevant number of applications concerns curved structures (arches, vaults, domes, etc.), the majority of studies available in literature provide a contribution mainly concerning the specific case of applications on flat masonry substrates. The present paper is part of a research activity carried out by the Authors with the main goal to provide a contribution toward the study of the bond behavior of FRCM systems externally applied to curved masonry elements. In particular, the results of numerical analyses carried out by means of a simple modeling approach proposed by the Authors are here carried out by considering as case studies specimens object of a recent experimental investigation. Specific aspects influencing the local bond behavior of FRCM systems applied on curved masonry substrates are then analyzed by opportunely introducing them into the numerical model. The obtained results allow for understanding the effect of important features, experimentally observed in terms of global response, and here assessed in terms of local bond behavior, by particularly emphasizing the role of the curvature and the strengthening position.

Numerical Investigations of GFRC beams strengthened in shear with innovative techniques

This paper discusses the Finite Element analysis (FE) conducted to predict the behavior of Glass Fiber Reinforced Concrete (GFRC) beams without shear reinforcement (stirrups) and strengthen them with proposed techniques to increase their shear strength. for this study, A total of eighteen (18) (120 * 300 * 2200 mm) specimens were modeled using Ansys™ mechanical. The main variables were the percentage of discrete glass fiber in the concrete (0.0, 0.6, and 1.2%), the type of main reinforcing bars (steel or GFRP), the shear strengthening material (GFRP or steel) links, the strengthening systems (side near-surface mounted (SNSM) bars, externally bonded (EB) sheet, or both), various NSM GFRP bars configurations (side bonded links, full wrapped stirrups, side C-shaped stirrups, and side bent bars), the link spacing, the link inclination angle, and the number of bent bars. Each model had a free span of 2000 mm with a constant shear span-to-depth ratio (a/d) of 2.0. The numerical models were verified against experimental results presented in the earlier publication. These results were analyzed to investigate the effect of main variables on shear strength. Increasing the ratio of discrete glass fiber in the R.C beam to 0.6 and 1.2% enhanced the ductility and increase the shear strength by 24% and 32% for steel reinforcement and by 16% and 29% for GFRP reinforcement, respectively. The use of GFRP bars instead of steel bars as the main reinforcement slightly enhanced the shear strength and ductility but decreased the stiffness. the use of various strengthening systems enhanced the shear capacity by a ratio of up to 115%. A new strengthening technique (SNSM bent bars with strips) produced better improvements in terms of shear capacity, ductility, and crack propagation compared to other strengthening techniques. The results of Numerical analyses and the experimental results for eighteen beams were considered, the ratio between them is equivalent by a factor of 0.96 to 1.04.

Improvement of tailings impoundment seismic and post-seismic stability using densification and waste rock inclusions

Tailings impoundments are often prone to failure due to various causes related to complex loading conditions. For instance, tailings impoundments can fail during or after a seismic event, mainly because of the liquefaction of loose, cohesionless tailings. To improve the seismic stability of impoundments, the density of the tailings can be increased or waste rock inclusions (WRI) can be added in the impoundment. This paper presents the results of numerical analyses of the impoundments loaded with a variety of ground motions with different frequencies, scaled at two different levels of intensity representative of two mining regions of Eastern Canada. The results show that the conventional impoundments are subjected to medium to high displacements at the end of shaking; these show a high probability of rupture during the earthquake or in the post-seismic phase. Tailings densification can decrease the volume of liquefied tailings and displacements during the seismic phase but does not significantly reduce the probability of post-seismic failure. WRI can slightly reduce the volume of liquefied tailings, depending on the intensity of the motions, but the reinforcement reduces significantly the lateral displacements; impoundments with WRI show even better performances during the post-seismic phase. The use of WRI is deemed a good approach to ensure the seismic stability of tailings impoundments and reduce the risk of seismically induced failure.

Probabilistic Seismic Demand Models of Circular Tunnels Subjected to Horizontal Ground Motions Based on 2D Dynamic Analyses

ABSTRACT This paper develops the probabilistic seismic demand models of circular tunnels under the transversal seismic load. The uncertainties of ground motion, soil profile, tunnel depth, and lining size are considered. Since the quasi-static analyses may significantly underestimate the seismic responses of tunnels, the results of dynamic numerical analyses are adopted to construct probabilistic models that are more accurate. The constructed model is unbiased and can facilitate the fragility analysis of tunnels. As a demonstration, the proposed probabilistic models are used to estimate the seismic fragility curves of a particular tunnel.

Selectivity of Protein Interactions Stimulated by Terahertz Signals.

It has been established that Terahertz (THz) band signals can interact with biomolecules through resonant modes. Specifically, of interest here, protein activation. Our research goal is to show how directing the mechanical signaling inside protein molecules using THz signals can control changes in their structure and activate associated biochemical and biomechanical events. To establish that, we formulate a selectivity metric that quantifies the system performance and captures the capability of the nanoantenna to induce a conformational change in the desired protein molecule/population. The metric provides a score between -1 and 1 that indicates the degree of control we have over the system to achieve targeted protein interactions. To develop the selectivity measure, we first use the Langevin stochastic equation driven by an external force to model the protein behavior. We then determine the probability of protein folding by computing the steady-state energy of the driven protein and then generalize our model to account for protein populations. Our numerical analysis results indicate that a maximum selectivity score is attained when only the targeted population experiences a folding behavior due to the impinging THz signal. From the achieved selectivity values, we conclude that the system response not only depends on the resonant frequency but also on the system controlling parameters namely, the nanoantenna force, the damping constant, and the abundance of each protein population. Based on the selectivity metric, the nanoantenna must be tuned to a frequency that is not necessarily the resonant frequency of the protein. The presented work sheds light on the potential associated with the electromagnetic-based control of protein networks, which could lead to a plethora of applications in the medical field ranging from bio-sensing to targeted therapy.