Results Of Numerical Analysis Research Articles

A new p-y model for soil-pile interaction analyses in cohesionless soils under monotonic loading

The most widely used analysis method for the laterally loaded pile problem is the Winkler spring approach. Although researchers have proposed nonlinear formulations for the p-y curves, the contribution of the soil nonlinearity has not been thoroughly studied. The main drawback of the current approach is the use of a single stiffness in the p-y formulation. This study investigates the laterally loaded pile problem by employing the pressure-dependent hardening soil model with small-strain stiffness (HS-Small Model), where the degree of soil nonlinearity is better integrated. The parametric analyses are performed on the verified model for various pile and soil properties. A new p-y model is proposed for pile behaviour under monotonic loading based on the numerical analysis results. The model includes the initial stiffness, ultimate soil resistance, and degree of nonlinearity parameters. The validity of the proposed model is demonstrated by simulating a centrifuge and two field tests from the literature. The proposed model accurately accounts for soil nonlinearity and significantly improves the estimation of lateral displacements.

Leptospirosis Relative Risk Estimates based on Continuous-Time, Discrete-Space Stochastic SIR-L-SI Transmission Model

Leptospirosis is a re-emerging global disease that has become endemic in Malaysia. The transmissions usually occur between animals especially rats to rats and rats to humans. Since, it is an easily contractable disease that can be transmitted directly through contact with infected rat’s urine or indirectly from the environment such as via water and soil, it is very challenging to curb this disease from infecting humans. Poor understanding of the disease and lack of epidemiological data also made leptospirosis is difficult to control. To cope with this problem, a leptospirosis disease transmission model is developed to study the mechanism of leptospirosis disease spread over continuous-time that may help to predict future caused of an outbreak. This study aims to construct a continuous-time and discrete-space stochastic SIR-L-SI (Susceptible, Infected, Recovered Humans-Leptospires in the Environment-Susceptible, Infectious Rats) of leptospirosis disease transmission to estimate the risk involved. A simple method of asymptotic and numerical analyses is applied as an alternative approach for solving simultaneous differential equations in the leptospirosis SIR-L-SI transmission model. The application of the proposed model is demonstrated using leptospirosis data for Malaysia. The results of asymptotic behaviour and numerical analysis provide useful information about susceptible and infective rat and human populations as well as offer relative risk estimates that can be used as one of the control measures in identifying hot-spot areas for this disease.

Failure investigation of a propped cantilever truss bridge

Propped cantilever truss is not a common bridge construction technique. The performance of such bridges under operational and extreme loading is not reported in the literature either. In this paper, failure mechanisms in a propped cantilever truss bridge are reported using field investigation. The field observations are supplemented by numerical analysis to identify the causes of failure. A a systematic account of damage mechanisms in bridge components is also reported. The failure of the Lamgadi Bridge over the Seti River in Nepal is used as a case study example. The loading and construction protocols are detailed, and numerical analysis results are juxtaposed with the field observations to explain the failure mechanisms. Field observations and numerical results show that lack in adequate design is the most likely cause of the bridge collapse. Numerical results also indicate that the roller support at the propped end, unlike the hinged pot bearing used in the as constructed bridge would have been a safer choice. The failure could have been easily prevented with proper numerical simulation of the bridge response during the design phase.

Mathematical Analysis of Tuberculosis Transmission Model with Multidrug and Extensively Drug-resistant Incorporating Chemoprophylaxis Treatment

Tuberculosis has remained the principal cause of mortality worldwide, and one of the major sources of concern is drug-resistant TB. The increasing emergence of extensively drug-resistant and multidrug-resistant TB has further increased the TB epidemic. In this current work, we suggest a model to study the transmission of TB with extensively drug-resistant and multidrug-resistant compartments, incorporating chemoprophylaxis treatment. In the theoretical analysis, the concept of the next-generation matrix and the Jacobian method are applied to obtain a formula that states the reproductive number. The existence of endemic and disease-free equilibrium points was checked, and their stability has been analyzed using the Lyapunov method. The qualitative-based analysis indicated the local asymptotic stability of the disease-free-state for R0 1, whereas the endemic state is globally asymptotically stable if R0 1. Moreover, sensitivity analysis was carefully done using normalized forward sensitivity, and numerical simulation was carried out. Based on the results of numerical simulation and sensitivity analysis, chemoprophylaxis treatment was found to drastically minimize the progression of exposed individuals to infectious classes and also reduce the progression to extensively drug-resistant and multidrug-resistant classes, which decreases disease transmission.

A Comparative Study on the Structural Response of Multi-Linked Floating Offshore Structure between Digital Model and Physical Model Test for Digital Twin Implementation

A digital twin is a virtual model of a real-world structure (such as a device or equipment) which supports various problems or operations that occur throughout the life cycle of the structure through linkage with the actual structure. Digital twins have limitations as a general simulation method because the characteristic changes (motion, stress, vibration, etc.) that occur in the actual structure must be acquired through installed sensors. Additionally, it takes a huge computing cost to output changes in the structure’s characteristics in real time. In particular, in the case of ships and offshore structures, simulation requires a lot of time and resources due to the size of the analysis model and environmental conditions where the wave load acts irregularly, so the application of a different simulation methodology from existing ones is required. The order reduction method, which accurately represents the system’s characteristics and expresses them in a smaller model, can significantly reduce analysis time and is an effective option. In this study, to analyze the applicability of the order reduction method to the development of digital twins for offshore structures, the structural responses of a multi-connected floating offshore structure were estimated by applying the order reduction method based on distortion base mode. The order reduction method based on the distortion base mode predicts the responses by constructing an order-reduced conversion matrix consisting of the selected distortion base mode, based on the mode vector’s orthogonality and autocorrelation coefficients. The predicted structural responses with the reduced order model (ROM) were compared with numerical analysis results derived using the higher order boundary element method and finite element method with in-house code owned by the Korea Research Institute of Ship & Ocean Engineering and measured responses with a model test. When compared with the numerical analysis results, the structural responses were predicted with high accuracy in the wave direction and wave frequency band of the selected distortion base mode, but there are differences due to changed characteristics of the structure when compared with the results of the model test. In addition, differences were also seen in reduced order model evaluation with different sensor locations, and it was confirmed that the more similar the extracted distortion base modes of input sensor location set is to the distortion base modes of predicted location set, the higher accuracy is in predicting the structural responses. As a result, the performance of the reduced order model is determined by the distortion base mode selection method, the locations of the sensor, and the prediction for the structural response.

Seismic behavior of prefabricated frame with special‐shaped concrete‐filled steel tubular columns and H‐shaped steel beams

AbstractTo realize the prefabricated structure of special‐shaped concrete‐filled steel tubular (CFST) column frame and enhance the level of indoor room utilization, this paper proposed a novel prefabricated frame with special‐shaped CFST columns and H‐shape steel beams connection with side plate. To investigate seismic behavior of this prefabricated frame structure, a 2‐story and 2‐bay CFST frame specimen was fabricated and tested under reversed cyclic loading. The failure mode, hysteresis behavior, degradation of lateral stiffness and bearing capacity, ductility and energy dissipation were analyzed. Experiment results indicated that failure mode presented strong columns and weak beams. Hysteresis curve of frame showed fully shuttle‐shaped. The mean story drift angle was 1/36 at ultimate stage. Equivalent viscous damping coefficient was 0.038–0.464. The bearing capacity degradation was relatively gentle, but the overall stiffness degradation was more obvious. It suggested that the frame had proper seismic and energy dissipation property. After the test, the seismic property of test frame was further investigated through the numerical simulation approach. The failure mode and skeleton curve obtained from the simulation were nearly consistent with test results, indicating that numerical analysis results were precise and with high reference meaning.

Frequency Identification of Equal-Span Continuous Girder Bridge Based on Moving Vehicle Responses

The indirect method for bridge modal identification based on the response of moving vehicles has attracted widespread attention in recent years. However, most existing studies only focus on the simply supported bridge, while continuous girder bridges are widely used in practical engineering. Therefore, this study proposes an indirect frequency identification method for continuous girder bridges. First, the mode shape formula of the equal-span continuous beam is deduced using the three-moment equations, and the analytical solution of the vehicle vibration response is deduced via the vehicle–bridge coupled vibration theory. Second, the derived analytical solution is verified through numerical analysis results and field test results. Finally, the effects of bridge and vehicle parameters on the frequency identification accuracy are analyzed. The results show that a reasonable frequency of the trailer should be selected to avoid the resonance between the vehicle and the bridge for better performance. The research findings can provide a reference for the indirect identification of continuous girder bridges based on the response of moving vehicles.

Dynamic compression reconstruction of pulsed thermography sequence for defect characteristic enhancement in composites

In this study, a dynamic compression reconstruction (DCR) method for pulsed thermography sequence was proposed, which could effectively compress the original data length of pulsed thermography and significantly enhance the defect signal characteristics. The DCR method modulated the length of the pulsed thermography sequence to dynamically compress the image sequence with a newly defined F-function, thus reconstructing the DCR thermal image sequence. The length of the DCR thermal image sequence was compressed to 1/4 the length of the raw thermal image sequence. We assessed the DCR method using the pulsed simulation data of a homogeneous flat plate with circular defects in the subsurface, and found that the proposed DCR method could suppress temporal noise, reduce the edge blur of defects, and enhance defect recognition. To further verify the validity and practicability of this method, the pulsed thermography experimental data of the glass fiber reinforced plastic (GFRP) specimen was processed using the DCR method, and the experimental results were consistent with the numerical analysis results of the simulated data. The DCR thermal image of the GFRP specimen had lower spatial noise and higher signal-to-noise ratio (SNR) of the defects than the raw thermal image. Finally, the DCR method was compared with other pulse thermal signal processing methods, including TSR, PPT, and PCT, indicating that the pulsed thermal images processed by the DCR method could achieve the highest SNR of the defects.

Effect of external prestressing on the special shear lag behavior of precast box girder bridges

The shear lag behavior exhibited by precast segmental box girders (PSBGs) under concentrated external prestressing differs significantly from that observed in box girders subjected to vertical loads. To study the special shear lag behavior of PSBGs under external prestressing, a theoretical analytical method was developed based on the classical energy variational principle. In this analysis, the effect of external prestressing was decomposed into axial compression and bending effects through the equivalent load method. For each of these effects, appropriate longitudinal warping displacement modes were assumed, and the total energy functional expressions of the system under these two effects were further established. The governing differential equations for the two effects were derived using the principle of energy variation. Analytical solutions for the normal stress of the beam section under axial compression and bending effects were deduced, and corresponding boundary conditions were obtained. Subsequently, the normal stress of the section under the two effects was superimposed to obtain the comprehensive normal stress distribution curve of the beam section under external prestressing. The reliability of the theoretical analysis method was validated through a comparison of the theoretical analysis results with experimental and numerical analysis results.

Experimental study on the seismic behavior of an innovative stepped beam-column joint

Achieving favorable seismic performance in joints while maintaining flush alignment on the upper and lower surfaces of the beam flanges remains a current challenge. To address this issue, this paper introduces an innovative stepped beam-column joint. To study the seismic performance of the joint, four beam-column joint specimens with different configurations were tested under cyclic loading. The plastic development process, failure modes, hysteresis loops, skeleton curves, stiffness degradation, ductility, load-bearing capacity, and energy dissipation capacity of the joint specimens were carefully investigated. All joint specimens exhibited superior seismic performance and load-bearing capacity. Moreover, variations in plate configurations led to discrepancies in the final failure modes among different joint specimens. Finally, finite element models were established and verified for each joint specimen, and analyses of the tensile forces on outer bolts were conducted. Through the experimental and numerical analysis results, it was concluded that the proposed innovative stepped joint could exhibit excellent seismic performance, and could be recommended for practical application in engineering.

Validation of numerical results of complex seismic analysis through simple analytics

The paper analyzes the application of the numerical findings of the program, which is becoming increasingly difficult for civil and structural design. Since, as in many other countries, the verification of design using a software model is now required by current Italian codes as well. Given this, the structural engineer must provide a technical report using a licensed software tool, attached to other project documents to get the Seismic Authorization at the local Civil Engineering Department offices. Following a brief explanation of structural analysis methodologies, this study presents a criterion for assessing the applicability of numerical findings obtained using any structural software. Three case studies of this criterion are shown to demonstrate how to check them using simple manual calculations: (i) the normal stress in RC columns subjected to gravity loads; (ii) the periods of vibration, participating masses, and seismic base shear derived from dynamic modal analysis; and (iii) the main parameters characterizing the pushover curves of existing buildings. Finally, this work underlines the significance of confirming the application of numerical results obtained by software in civil and structural design. The offered criteria and scenarios exhibit realistic techniques to ensure accuracy and reliability in structural performance assessment, according to the structural requirements imposed by current codes in Italy and similar countries.

Research on Aerodynamic Test Validation and the Vector Force Control Method for an E-STOL Fan Wing Unmanned Aerial Vehicle

The concept of the Fan Wing, a novel aircraft vector-force-integrated device that combines a power unit with a fixed wing to generate distributed lift and thrust by creating a low-pressure vortex on the wing’s surface, was studied. To investigate the unique propulsion mechanism of the Fan Wing, a Fan Wing test platform was developed, and experiments were conducted in a wind tunnel. At the same time, numerical simulations were established. In order to further improve the aerodynamic efficiency of the Fan Wing and decouple the control of lift and thrust, an improved scheme for the leading-edge structure of the Fan Wing was proposed, and a numerical analysis was conducted. A Fan Wing unmanned aerial vehicle (UAV) was designed and manufactured using the Fan Wing as the source of lift and thrust for the aircraft, and flight verification was conducted. The wind tunnel tests have proven that the main factors influencing the lift and thrust of the Fan Wing are rotation speed of cross flow fan, angle of attack, and incoming flow. The numerical analysis results of slotting on the leading edge show that the lift and thrust of the Fan Wing can be improved, but also the strength and position of the low-pressure vortices can be controlled. The results of flight tests show that the distributed lift and thrust of the Fan Wing can be directly applied to aircraft without the need for additional propulsion devices. In summary, the aerodynamic characteristics of the Fan Wing can be applied to electric short takeoff and landing (E-STOL) scenarios in urban air traffic.

The shaking table test and the numerical analysis on a novel viscous damper installation configuration

Most of the existing installation configurations for viscous dampers only consider the structural requirement, ignoring the functional requirement of the architecture. Therefore, an open-space viscous damper installation configuration is proposed and studied by some scholars. Based on the existing research findings, the working performance of the open-space installation configuration for viscous dampers (OSVDIC) in the actual structure remains to be studied. In order to investigate the working mechanism and damping effect of OSVDIC in the structure, the shaking table test is conducted on a three-story steel frame structure model with OSVDIC. Based on the conditions of the shaking table test, the finite-element model of a three-story steel frame structure model with the OSVDIC is established by SAP2000 for time-history analysis. The comparison shows that the numerical analysis results are in good agreement with the shaking table test results. The results of the shaking table test and numerical analysis show that, on the premise of reducing space occupation of the structure, adding the OSVDIC in the structure could significantly lower the seismic response. The effect of the parameters of the OSVDIC on the damping effect of the structure is analyzed by SAP2000. In summary, the structure with OSVDIC could meet the requirements of a certain level of damping effect, while also taking the needs of open space, wide vision, aesthetic appearance, and functional use into account.

Optimization of parameters for the best shot peening effect based on surface response and neural network model

To optimize the peening effect of different shot peening process parameters on metal surfaces, the mapping relationship between different shot peening process parameters and metal surface integrity was obtained. In this paper, ABAQUS software was used to establish a DE-FE (Discrete element-Finite element) random multi-shot analysis model to simulate shot peening, then optimize the shot peening process parameters based on the surface response method(RSM), and finally validate it through experiments and BP(back propagation) neural network model. The result shows that when the shot velocity is 70 m s−1, the impact angle of shot is 61.45°, and the shot diameter is 0.78 mm, the shot peening effect is the best, the surface roughness value is reduced by 101.84%, and the arc height value is increased by 54.66%; the error between the predicted results of BP neural network and the results of numerical analysis is less than 8%. Therefore, the optimized process parameters significantly improve the shot peening effect, but also shows that the BP neural network prediction model can more accurately predict the mapping relationship between the input parameters of shot velocity, shot diameter, and impact angle of shot and the output parameters of roughness value and arc height value.

Dynamic response of the annular hole defect under ultrasonic in brick

In recent years, ultrasonic diagnostics and health monitoring of buildings have become widely used in construction. However, the accuracy of ultrasonic devices in heterogeneous media such as concrete, brick and other elements is fraught with difficulties and leads to errors. The article considers the problem of the dynamic response of a defect in the form of a cylindrical hole in a brick during ultrasonic diagnostics. The problem was simulated in the ANSYS environment using the finite element method. A dynamic stimulus with a frequency of 60 kHz is applied in the immediate vicinity of the defect and the response is numerically determined at a point symmetrically located from the defect. The results of numerical analysis in the form of fields of displacements, stresses and deformations have been obtained. It is shown that to effectively determine the geometry of a defect in the form of a hole, it is necessary to analyse data on the 3rd or 4th half-waves of the response.

The interface instability development induced by the bulk density perturbations in accelerated media

The development of hydrodynamic instabilities has a significant impact on the operation of laser fusion systems. During radiation compression, the shells of a target are accelerated, resulting in the growth of perturbations at their interfaces. In this paper, we study the influence of density perturbations on the stability of the contact boundary during accelerated motion. The analysis is performed in a two-dimensional planar formulation using the linear approximation and assuming a weak spatial dependence on the temperature near the contact boundary. Due to the consideration of small time intervals, the phenomenon of heat conduction is not taken into account. The cases of acceleration of a medium described by the Mie–Grüneisen equation of state (EoS) into a vacuum and of acceleration of two contacting media, each described by the ideal plasma EoS, are considered. The time dependence of the amplitude of the boundary perturbation on time is obtained. The obtained values are in agreement with the results of numerical analysis. It is shown that the boundary curvature occurs independently of the acceleration direction. The theoretical results are compared with numerical results for laser fusion systems.

FABRICATION OF REALISTIC TRANSPARENT POROUS MEDIA FOR 3D OBSERVATION OF INTERNAL MASS TRANSPORT

A new experimental system was developed to observe the migration of colloidal particles in saturated porous media in 3D, which is important in engineering processes such as contaminant migration and filtration. The system enables the observation of internal migration that is invisible from the outside by fabricating a porous body using a transparent material and a 3D printer. Non-artificial media with arbitrarily controlled internal pore sizes were fabricated by designing the porous media based on the results of numerical analysis on phase-separation phenomena. The refractive indices of the porous media and the interstitial liquid were matched, and a laser sheet was used to extract cross sections of the media. By reconstructing multiple cross-sectional images, it was possible to visualize the 3D migration of suspended particles. The developed system was then applied to the collective gravitational settling of fine particles in saturated porous media. The results showed that the particles selectively settled in the pore networks while repeatedly branching in the lateral direction.

Numerical analysis of thermal differential distribution in Bobbin tool friction stir welding of 7075-AZ31B dissimilar alloy

The theoretical model of bobbin tool friction stir welding (BT-FSW) structure and dynamic process is established. Because of the great differences in properties of different materials, the mathematical relationship between material stress and deformation will be expressed based on 3D transient heat conduction equation and J-C constitutive model. The BT-FSW process of 7075 and AZ31B was analyzed by finite element method, and the field distribution, thermal cycle curve and stress distribution characteristics of different welding areas of the welded material were simulated. To predict and control the non-equilibrium distribution of welding temperature and stress field, the influences of different Rotating speed, welding speed, offset and other variables on the BT-FSW process of 7075/AZ31B aluminum magnesium dissimilar alloy were studied comprehensively. Finally, the reliability of the model is proved by fitting the experimental and numerical analysis results. The research results show that the temperature of BT-FSW presents an “hourglass” symmetrical distribution, and the stress distribution on both sides of the plate is uniform when the aluminum alloy is placed on the advancing side, the stirring tool is offset to the aluminum alloy by 2mm, and the rotating speed and welding speed are 700r/min and 180mm/min, respectively.

The Explosive Crack Propagation Mechanism of Layered Rock Mass

Layered joints significantly affect the propagation and attenuation of engineering blasting stress waves and have a significant influence on rock breakage. In this study, the explosion crack propagation mechanism of a stratified rock mass with weak or no cementation is analyzed. Multilayer plexiglass plates are employed to simulate a layered rock mass, establishing an experimental model to investigate the vertical interaction between explosive charges and layered rock masses. The extent of ruptures and damage within the charging and sealing sections of the rock mass is analyzed. The explosion cracks at the bottom of the hole are relatively dense, whereas those at the hole opening are relatively sparse. The range of the crushing and fracture zones around the gun hole in the charging section is larger than that in the blocking section. Moreover, as the blocking section approaches the free plane, the crushing zone size decreases. A notable area of rapid damage escalation is identified between the blocking and charging sections, leading to a significant increase in damage intensity. The numerical analysis results indicate that the cumulative explosive energy within the charging section surpasses that of the blocking section, and the rate of energy accumulation is notably higher in the charging region.

Study on the seawater cooled PRHRS of a nuclear propulsion ship with the upper heat exchanger for driving force and the seawater heat exchanger as an ultimate heat sink

As international maritime trade among countries increases, great efforts are being made to reduce the amount of greenhouse gases emitted from ships using conventional fossil fuels. A variety of environment-friendly power sources for ships are being considered, and nuclear energy is one of them. The research described in this paper focuses on elemental technologies related to nuclear-powered ships rather than the nuclear reactor technology itself. Among those technologies, the Passive Residual Heat Removal System (PRHRS) of a nuclear-powered ship is studied to remove residual heat by using seawater as an alternative heat sink. New concept of PRHRS is proposed and it is named as SWC-PRHRS. SWC-PRHRS has two heat exchangers: one is for driving force and another is for dumping the most of residual heat to the sea. Numerical analysis and experimental studies are conducted to improve the performance of SWC-PRHRS. The numerical results show that most of the residual heat comes from a reactor core is eliminated by sea water cooling proving the concept of SWC-PRHRS is working properly without any operator intervention and additional water supply. Experimental studies are conducted based on the numerical analysis results. From the experimental results, it is found that the mass flow rate of SWC-PRHRS is very sensitive to the filling ratio of SWC-PRHRS and there are three distinctive filling ratio ranges. Through the experiment, it is confirmed that SWC-PRHRS is working efficiently with the lower mass flow rate and the smaller upper heat exchanger without any operator intervention. SWC-PRHRS could remove a large amount of residual decay heat from the ship's reactor and release it to the sea. Considering the size, weight, and exceptional heat removal capability of SWC-PRHRS, it is clear that SWC-PRHRS is well suited for marine application usage.