Finite Element Analysis Program Research Articles

Open-source simulation of strongly-coupled fluid-structure interaction between non-conformal interfaces

Design code-based “life-safety” requirements for structural earthquake and tsunami design offer reasonable guidelines to construct buildings that will remain standing during a tsunami or seismic event. Much less consideration has been given to assessing structural resilience during sequential earthquake and tsunami multi-hazard events. Such events present a series of extreme loading scenarios, where damage sustained during the earthquake influences structural performance during the subsequent inundation. Similar difficulties exist with respect to damage sustained during tropical events, as wind and fluid loading may vary with structural response or accumulated damage. To help ensure critical structures meet a “life-safety” level of performance during such multi-hazard events, analysis software capable of simulating simultaneous structural and fluid dynamics must be developed. To address this gap in understanding of non-linear fluid-structure-interaction (FSI), an open-source tool (FOAMySees) was developed for simulation of tsunami and wave impact analysis of post-earthquake non-linear structural response of buildings. The tool is comprised of the Open-source Field Operation And Manipulation software package and OpenSeesPy, a Python 3 interpreter of OpenSees. The programs are coupled via preCICE, a coupling library for partitioned multi-physics simulation. FOAMySees has been written to work in a Linux OS environment with HPC clusters in mind. The FOAMySees program offers a partitioned conventional-serial-staggered coupling scheme, with optional implicit iteration techniques to ensure a strongly-coupled two-way FSI solution. While FOAMySees was developed specifically for tsunami-resilience analysis, it may be utilized for other FSI applications with ease. With this coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) program, tsunami and earthquake simulations may be run sequentially or simultaneously, allowing for the evaluation of non-linear structural response to multi-hazard excitation.

압축구조 개선을 통한 분로리액터의 소음 저감에 관한 연구

Recently, with the development of the city center around the substation, complaints about noise are increasing. Shunt reactors are a major source of noise in substations. To reduce the noise of the shunt reactor, research on the magnetic circuit and structural design for optimizing the compression distribution are important. In this paper, the magnetic flux distribution and compression distribution of the magnetic element were calculated using a finite element analysis program, and the reduction effect was analyzed by measuring the noise. Introducing a study that improved the distribution of magnetic flux by applying a magnetic flux control panel to the vibration caused by the magnetomotive force generated from the magnetic element, and reduced noise by changing the shape of the compression structure.

Experimental and Numerical Predictions of Cryogenic Leakages in Welded Steel Plates

This study presented experimental and numerical research to investigate the effect of cryogenic leakage on a plate structure of AH36-grade steel containing welded joints. To simulate the cryogenic leakage conditions, the welded plate was exposed to a temperature of −196 °C by supplying liquid nitrogen (LN2) to the center of the steel plate. The time-dependent temperature history and strain variation were measured by using thermocouples and strain gauges attached to the plate surface. Additionally, the residual stress of the middle surface section before and after the cryogenic leakage process was measured by X-ray diffraction analysis (XRD). A three-dimensional finite element model was created with the use of a commercial finite element analysis (FEA) program to simulate the flux-cored arc welding process and cryogenic leakage process. The steel surface temperature dropped sharply and reached approximately −196 °C at 160 s after LN2 supplement. After the first 650 s of the LN2 leakage experiment, the outside of the trough reached approximately −75 °C and −25 °C, depending on the location of the thermal couples. Although there was a relative difference in the results, the experiment and numerical simulation results for temperature and stress distribution showed good agreement. The results could be utilized in the ship design stage adopting welded structures as a basic database.

Research on evolution of shock wave of ground explosion in pit type explosion containment vessel

In order to explore the evolution of shock wave in a confined space, a pit type explosion containment vessel is designed in this paper, in which the ground explosion experiments are carried out. Four gauge points are set on the container cover to collect shock wave signals. By observing the pressure history, it was found that the shock wave experiences multiple reflections in the vessel and then tends to be stable gradually. As well as each pressure crest increases abruptly and then decays rapidly. Meanwhile, the finite element analysis program ANSYS/AUTODYN is adopted to simulate the charge is detonated in the explosion containment vessel by the 2D axisymmetric algorithm. Observing the variation of the pressure field inside the container, it is found that the propagation velocity of shock wave in sand is obviously lower than that in air. And the intensity of the shock wave is obviously increased after reflection and interaction. As the shock wave propagates upward along the side wall of the vessel, the incidence angle of the shock wave also increases gradually. When the incidence angel reaches 47.73°, Mach reflection occurs. Through analyzing the distribution of pressure field near the cover, it is found that the center and the edge of the cover suffer the impact strength and bear the serious damage risk.

Reinforcement design optimisation for continuously reinforced concrete pavement: one-mat vs. two-mat

ABSTRACT Over the years, thicknesses of continuously reinforced concrete pavement (CRCP) increased to accommodate rising truck traffic. With a fixed percentage of longitudinal reinforcement relative to the concrete cross-sectional area, thicker slabs necessitate more reinforcement and reduced bar spacing, potentially hindering consolidation. To address this issue, two-mat steel design was implemented in Texas for pavements with thickness of 330 mm (13 in.) or larger. Performance evaluations of thick CRCPs revealed that horizontal cracking developed at the depth of reinforcement where one-mat steel was placed, while no horizontal cracking was observed where two-mat steel was used. Pavement responses with one-mat and two-mat reinforcements with different depths were analysed by three-dimensional modelling with a finite element analysis (FEA) programme for the wide range of environmental loadings. Maximum concrete vertical tensile stresses around longitudinal reinforcement at transverse crack area are a good indicator of horizontal cracking potential; those stresses were evaluated, along with concrete stresses at top of the slab, which are responsible for top-down transverse cracking. The results show that the two-mat design causes higher concrete stresses at the top of the concrete slab and lower concrete stresses around the longitudinal reinforcement, leading to increased transverse cracks and a reduction in horizontal cracking potential.

Numerical Modeling Technique of Damage Behavior of MaSonry-Infilled RC Frames

The damage pattern of masonry-infilled reinforced concrete (RC) frame structures in earthquake events is complicated, and understanding the detailed failure behavior of these structures and modeling it accurately has been a challenging task. In this paper, the extended finite element method (XFEM) is introduced to reproduce arbitrary cracks initiating and propagating in concrete frame and masonry units, combined with interface elements to model various behaviors of masonry-infilled RC frames. Within the finite element analysis program FEAP, a user element subroutine is adopted for the incorporation of XFEM and two types of extended finite elements with and without crack tip enrichments are built to simulate the behavior of concrete material for frame members and masonry blocks for the infill panel, respectively. In addition, a macro command is created to check the crack-propagation criterion and update crack and enrichment information. Furthermore, numerical examples are performed with existing test data, which reveal the efficiency of the implementation procedure. A comparison of the analytical and experimental results show that the proposed modeling can be used to predict the crack and failure process and the load-bearing capacity curves of the structures and reflect accurately the interaction of masonry infill and RC frames.

An BESO Approach for Optimal Retrofit Design of Steel Rectangular-Hollow-Section Columns Supporting Crane Loads

In this paper, we propose a cost-effective optimal-topology retrofitting technique for hollow-steel-section columns to sufficiently support industrial running cranes. A so-called bi-directional evolutionary structural optimization (BESO) method was encoded within the MATLAB modeling framework, with a direct interface with an ANSYS commercial finite-element analysis program, to determine the optimal topology of double external steel plates connected to columns in a 3D space. For the initial ground structure, we have adopted standard uniform double U-shaped external stiffener plates located at the top and bottom flange layers of an I-beam to box-column connection (IBBC) area. The influences of inelastic materials and the incorporated nonlinear geometry can effectively describe the premature (local buckling) failures of the columns in an IBBC area. The applications of the proposed optimal-topology BESO-based stiffening method are illustrated through the retrofitting of three hollow-steel-section columns, characterized by non-slender and slender compression sections. Some concluding remarks are provided on the pre- and post-retrofitted responses of the columns, with the results showing both the accuracy and robustness of the proposed external stiffening schemes.

Study of the laminas’ stress-strain state for cross-ply composites with the [± 45°]2s lay-up: tensile tests

In this paper we have analysed the relations that allows one to determine the components of strains and stresses in the orthotropic axes of layered fiber reinforced composite materials in tensile and compression experiments for test specimens with the [±45°]2s lay-up. In particular, such relations were compiled on the assumption that in a cross-ply fiber composite two adjacent layers with the [±φ] lay-ups can be considered as one symmetrically reinforced layer with orthotropic properties. To establish the degree of accuracy of these relationships and assumptions, numerical experiments were carried out to determine the parameters of the stress-strain state of specimens consisting of two and four monolayers of a unidirectional fibrous composite material with the [±45°]2s lay-up. The analysis has been performed in the ANSYS finite element analysis program system in a linear formulation of two- and three-dimensional problems. It is shown that in the central zone of the specimen, the theoretical-experimental methodology based on the above mentioned relations has a sufficient degree of accuracy. Based on the analysis of results of three-dimensional problems, the formation of a linear torque in the specimen, which causes the twisting of some zones of the specimen along its length, has been revealed.

음향진동 헬스케어기구의 마사지력 분석을 위한 유한요소해석 및 실험검증

The acoustic vibration health care device is a small medical device that can be used in homes. It was developed for the general public to meet the current needs of modern-day workers who value health and leisure. The device’s massager negates acoustic vibrations set at a certain frequency that activate metabolism and blood circulation. It has also been proven to lessen pain or enhance treatment effects by stimulating the cranial nerves. Stored inside the massager is a voice-coil actuator made of a bobbin core wrapped in coils and a permanent magnet. The component produces the Lorentz force as a result of the applied current and the magnetic flux density form the internal magnetic field. In our experiment, we used the ANSYS Maxwell, a commercial finite element analysis program, to analyze the electromagnetic field. We also measured and compared the Lorentz force by testing the massager’s vibrations. Through these actions, we validate the finite element analysis and obtained the design technology data of the massager model.

The Effect of Different Soil Classes on Earthquake Demands of Reinforced Concrete Structures: Case Study for Sakarya

In this study, it is aimed to investigate the effect of different soil classes on the behavior of the structure under earthquake loads. An evaluation was made for five-storey and eight-story reinforced concrete (RC) frame structures considering the three different soil classes (ZC, ZD, ZE) defined in the Turkish Building Earthquake Code 2018 (TBEC 2018) and the current earthquake hazard of Sakarya. In the structural system of the RC frame, the cross-section geometry and reinforcement details of the columns and beams were designed by considering the design criteria in TBEC 2018. While determining the dynamic behavior of the structure, the effective bending rigidity defined for column and beam elements in TBEC 2018 was used. For the RC frame structural model, the base shear force, story displacements and story drifts were investigated comparatively by using the mode superposition method in the SAP2000 finite element analysis program. When the results are compared, it is seen that as the soil stiffness decreases, the force and displacement demands on the structure increase.

Probabilistic assessment of slope stability at ore mining with steep layers in deep open pits

Purpose. A methodology development for predicting the geomechanical situation when mining an ore deposit with steep-dipping layers, taking into account the uncertainty in determining the rock properties, which is a consequence of the rock mass heterogeneity. Methods. The assessment of the open-pit wall stability is based on a combination of numerical simulation of the rock stress-strain state (SSS) and probabilistic analysis. The finite element method is used to determine the changes in the SSS that occur at various stages of mining operations due to design changes in the overall open-pit slope angle. The elastic-plastic model of the medium and the Mohr-Coulomb failure criterion are implemented in the codes of the 3D finite element analysis program RS3 (Rocscience). Stochastic simulation is used to assess random risks associated with natural object state variations. Findings. The distribution of maximum shear strains, which localizes the real or potential sliding surfaces in the open-pit wall at various stages of ore mining, has been identified. Based on the Shear Strength Reduction procedure, the open-pit wall Strength Reduction Factor (SRF) has been determined. The probabilities of open-pit wall stability loss, as well as the decrease in the strength reduction factor below the standard level at all stages of the ore body mining, have been revealed. Originality. For the first time, for real mining-geological conditions of a deep ore open pit, the dependence of the strength reduction factor on the overall wall slope angle, which changes during mining of each steep layer, has been determined. For each stage of mining operations, for the first time, the probability of a decrease in the open-pit wall stability below the standard level has been determined based on stochastic simulation. Practical implications. The ratio between the open-pit contour characteristic (overall slope angle) and the probabilistic safety factor is the basis for practical solutions to ensure the efficiency and safety of mining at various stages of friable and hard overburden excavation, ore extraction, as well as for the subsequent optimization of the open-pit design contours.

Finite element analysis of changes in tensile strain and deformation by airbag impact in eyes of various axial lengths

PurposeAirbags have substantially reduced mortality and morbidity, while ocular injuries caused by airbags have been reported. We applied a three-dimensional finite element analysis (FEA) model we have established for evaluation of the deformation of an intact eyeball of various axial lengths induced by an airbag impact at various impact velocities.MethodsA model human eye we have created was used in simulations with an FEA program, PAM-GENERIS™ (Nihon ESI, Tokyo, Japan). The airbag was set to impact eyes with various axial lengths of 21.85 mm (hyperopia), 23.85 mm (emmetropia) and 25.85 mm (myopia), at initial velocities of 30, 40, 50 and 60 m/s. Changes in the shape of the eye and the strain induced were calculated. Deformation of the eye in a cross-sectional view was displayed sequentially in slow motion.ResultsWe found that considerable damage, such as corneal or scleral lacerations, was observed especially at higher impact velocities, such as 50 or 60 m/s, in eyes with any axial length. Deformation was most evident in the anterior segment. The decrease rate of axial length was greatest in the hyperopic eye, followed by the myopic eye, and the emmetropic eye.ConclusionsIt was shown that hyperopic eyes are most susceptible to deformation by an airbag impact in this simulation. The considerable deformation by an airbag impact on the eye during a traffic accident shown in this study might indicate the necessity of ocular protection to avoid permanent eye damage.

Passive heat removal in horizontally oriented micro-HTGRs

There are novel, horizontally oriented high-temperature gas-cooled micro-reactor (HTGR) designs under consideration because of their portability, simplicity, and reliable operation. These features of the micro-HTGR design can meet the fission battery attributes, such as economic, standardize, installed, unattended and reliable. Although there have been HTGR related safety studies, micro-HTGRs when horizontally oriented are expected to exhibit significantly different thermal physics. During the unavailability of helium circulation, the internal reactor core is designed to cool by block-to-block conduction and radiation, and the reactor vessel surface is cooled by the ambient air. This scenario is anticipated during the transport of the micro-HTGR in a shipping container. The conduction and radiation between the prismatic micro-HTGR blocks in the core can be influenced by variances in the thermal contacts. This work investigated the conduction within a simulated horizontal HTGR core. An experimental setup was used to validate a numerical model. The experimental setup consisted of a hexagonal assembly with scaled prismatic blocks placed within a high-temperature vacuum environment. The gaps between the blocks were well controlled and monitored. The experimental setup was designed in such a way that the temperature variation in the axial direction was minimal, such that the experiment could be observed as a 2D (r, θ) heat transfer problem. The pressurized tube was equipped with Infra-Red (IR) transparent windows, and an IR camera was used to capture the spatio-temporal temperature evolution in the hexagonal block assembly during the cooldown experiments. The experimental scenario was computationally modeled with a finite element analysis (FEA) program. Once validated, the computational model was used to investigate the impact of gap conductance on overall decay heat removal. Using a conservative estimate for gap conductance value (100 W/m2−K) between the prismatic blocks, there is a negligible increase in temperature observed during decay heat generation.

Behavioural Assessment on Influence of Adjacently Placed Strip Footings at Different Embedment Level

Abstract The footings laid in close proximity imposes a definite change in the behaviour of the adjacent footing, subsequently changing the behaviour of the nearby footings. The present study emphasises the behaviour of the nearby strip footings embedded at a different level by adopting the commercially available finite element analysis program, ABAQUS. The load-settlement behaviour, ultimate bearing capacity (UBC), and the failure patterns of adjacent strip footings are assessed by considering the Mohr-Coulomb failure criterion. The UBC is of the nearby footings (left and right) are estimated and represented in terms of interference factors (ξL/ξR ) defined as the UBC of a footing in the presence of adjacent footing to that of same considered for equivalent isolated footing. The results reveal that a significant influence of the adjacent footing is experienced when the spacing between the footings (S/B) is lesser, and they behave as the single footing of greater width at S/B = 0.25 irrespective of the level of embedment depth. Furthermore, the influence of interference increases with the increase in the embedment depth of adjacent footing. It is found that the ξL is significantly more for a lower level of embedment depth, and the same increases with an increase in the embedment depth of the right footing but on the contrary ξR decreases. The increase in the peak interference factor, ξL-max for DL/B = 0.5 is 2.1% and 4.2% when DR/B = 0.75 and DR/B = 1.0, respectively.

Experimental and theoretical study on seismic behavior of connection between prefabricated steel-reinforced concrete column and base

This paper presents the seismic behavior of the prefabricated steel-reinforced concrete (PSRC) column. An experimental program was first performed on five full-scale specimens, varying by axial compression ratio (n) and shear span ratio (λ). Finite element analysis program was then carried out to calibrate the accuracy of the FEA models. Both experimental and numerical results revealed that PSRC column exhibited high energy dissipation and good plastic deformation. The calculational method to assess the bearing capacity of PSRC column was proposed and provided a reference for the actual engineering design and application of the PSRC column.

DEVELOPMENT OF FINITE ELEMENT ANALYSIS PROGRAM FOR ROTORDYNAMIC PREDICTION OF SINGLE AND MULTI DISK ROTOR MODEL

The rotating equipment is a crucial part of system performance reliability. Vibration, as a characteristic of an oscillating body, is a fundamental parameter to determine the dynamic behaviour of the rotor system. The dynamic characteristics include natural frequency, critical speed, mode shape, and vibration response. This paper discussed the application of rotordynamics analysis as a tool to numerically predict the dynamic behaviour of a rotor system. The aim is to determine a rotor system's natural frequency and critical speed by a finite element analysis (FEA) program. The selected method is validated using various analytical methods from other references with small discrepancies in the result. The calculation of FEA using the computational program; they applied the developed program to describe the dynamic characteristic of single and multi-disk rotors. The developed works provided comprehensive results about a rotor system's natural frequency, mode shape, and critical speed and predicted the vibration response due to unbalance. However, other types of rotors, such as coaxial dual rotors, can be further investigated to make the program capable of the general purpose of the rotor. Validation with the real case problem could be an interesting investigation to satisfy the result of developed works.

Performance-Based Design Method for Multiple Helices of Helical Pile in Cohesionless Soil

Multiple helices are being used frequently in helical pile applications nowadays. This paper presents multiple helices on simplified field design charts for small diameter helical piles that relate service compressive load and soil parameters as a group with the pile parameters. This study conducts an extensive three-dimensional nonlinear finite element analysis (FEA) study on multiple helices piles using the FEA program PLAXIS to evaluate helices’ performance subjected to axial compressive loads. A calibrated and verified numerical model uses full-scale load testing data of multiple helices from practical experience. This paper compiled numerical results from 495 models to propose an extension of the chart-based design. Here, the optimized combination of multiple helices will be the output of the design chart for soil type, service load, and allowable displacement as input. At the end of this paper, the design charts for double and triple helices are validated for cohesionless soil. The correlation square, R2, ranges from 0.69 to 0.86 for cohesionless soil. The mean Qc/ Qm is 0.90 for double helices and 1.04 for triple helices. Preliminary evaluation suggests that the method performs well. The authors believe that this study will permit engineers and state agencies to better understand the behavior of multiple helices, resulting in a more resilient approach in designing small diameter helical piles for a compressive load.

Numerical Analysis of the Vertical Crown Displacements in Triple Adjacent Tunnels with Rock Bolts and Pipe Roofings

This study aimed to investigate the effects of installing pipe roofings and rock bolts before bench cuts during the excavation of a tunnel. The limited space available during excavation resulted in the formation of triple adjacent tunnels. To solve the issue of narrow spacing between the tunnels, middle posts were added for greater stiffness, and pipe roofings were installed to prevent collapse in tunnel sections with shallow overburden where the rock weathering was significant. PLAXIS 3D 2018, a finite element analysis program, was used to simulate the wall rock displacement during the bench cuts with pipe roofings and rock bolts installed. In addition, the difference between the presence and absence of bias pressure was studied. It was found that, in the absence of bias pressure, the tensile and compressive forces were symmetric from side to side. However, under bias pressure, the tensile force remained unchanged. Moreover, the compressive force under bias pressure was three times greater than without bias pressure and was concentrated at the sidewall of the eastbound tunnel and the crown of the mass rapid transit (MRT) tunnel. The results may be helpful for the design and construction of multiple adjacent tunnels in the future.

Investigation of material deterioration and seismic behavior of Fertek and Hançerli Churches in Cappadocia Region

Cappadocia is among the rare natural and cultural centers on earth with its fairy chimneys, underground cities, rock churches, stone structures and natural beauties. Among these structures, Fertek and Hançerli Churches that are subjected to the scope of the study are very original artifacts with their superior construction techniques and rich workmanship according to the period they were built. In this study, the architectural features of Fertek and Hançerli Churches which were built in the 19th century and located within Niğde province in the Cappadocia Region were defined and material deteriorations were determined. In the light of these determinations, the existing static properties of these structures were examined using the Dynamic Finite Element Analysis program. Discoloration, vegetation, crack formation, moisture problems and partial mortar and stone losses were detected in both church structures. When the analysis results are evaluated, it has been determined that the structures need repair and improvement, depending on the region and soil class, considering the earthquake forces.

Empirical formulations for estimation of the ultimate strength of the perforated stiffened panels under the combined lateral pressure and in-plane compression

The holes artificially cut for a certain purpose can greatly reduce the ultimate strength of the perforated stiffened panels. In this paper, the ABAQUS finite element analysis program is used to investigate the effect of the position and size of the circular holes, the slenderness ratio, the aspect ratio, and the loading ratio on the ultimate strength of the perforated stiffened panels. Periodic and symmetric boundary conditions are applied to the (1/2 + 1+1/2) span model to consider the continuity of the stiffened panel in modeling. The results show that the ultimate strength of the perforated stiffened panel is highly dependent on the location and size of the hole. An empirical formula to primarily predict the ultimate strength reduction rate of perforated stiffened panel is proposed, and its accuracy is evaluated.