Finite Element Analysis Procedure Research Articles

Simulation of controlled modulus column installation using a large deformation finite element analysis

Controlled modulus columns (CMC) are widely used in ground improvement techniques where grout columns are constructed by penetrating an auger into the ground using the displacement approach. Numerical simulation of this problem is challenging owing to the large soil deformations associated with installation. Small strain-based finite element analysis procedures available in commercial finite element modeling software are unsuitable for simulating this problem because they cannot simulate large soil deformations around the auger during column installation. Hence, this study presents a numerical approach based on the finite element method to simulate the installation of CMCs. The numerical modeling technique adopted in this study considers large soil deformations around columns during penetration, and the proposed approach is based on remeshing and interpolation techniques. This method was developed using the Python development environment (PDE) within the ABAQUS/standard finite element program. It can penetrate columns below the ground surface without causing large mesh distortions. In this study, silty sand-type soil was considered; hence, the constitutive behavior was simulated using the Mohr–Coulomb criteria. The load-carrying capacity of a controlled modulus column was predicted and compared with an empirical equation based on the cone penetration resistance. The influence zone and failure mechanism of the soil during installation were determined by considering the stress distribution and soil flow pattern around the column.

Enhancing crashworthiness characteristics of modified hexagonal honeycomb structural panels through stretching and bending of ribs

The effects of stretching and bending of concave, convex, and horizontal ribs on the energy absorption characteristics of modified hexagonal honeycomb structural panels are investigated under in-plane quasi-static compression loading conditions. In this regard, five hierarchical modified structural panel configurations were fabricated using polylactic acid material (PLA) via a fused filament 3D printer, ensuring uniform wall thickness in the 1.5–2 mm range. The panels included the regular hexagonal panel (RHP), regular hexagonal panel with concave rib (RHCP), regular hexagonal panel with convex rib (RHXP), regular hexagonal panel with concave and horizontal ribs (RHCRP), and regular hexagonal panel with convex and horizontal ribs (RHXRP). In-plane quasi-static compressive loading tests were conducted to analyze crush resistance characteristics, and buckling modes of the modified honeycomb panels were examined through experimental and finite element analysis procedures. The result indicates that the specific energy absorption capacity (SEA) of RHXRP is increasing significantly compared to the SEA capacity of other categories of the structures. The changes in failure modes and increased crush energy absorption characteristics of modified RHP with the introduction of concave, convex, and horizontal ribs are elaborated.

Scalable BIM based open workflow for structural analysis of masonry building aggregates

Masonry building aggregates are complex historical structures comprising interconnected buildings. The safety of each building depends not only on its structural integrity but also on the interactions with neighbouring structures and their collective performance. The structural assessment of such complex constructions can benefit from BIM methodology. The latter eases modelling complicated solid geometries and assigning mechanical properties information essential for developing a reliable finite element model. Thus far, BIM to finite element analysis procedures applied to historic constructions have remained laborious, semi-automatic, and based on proprietary software. This paper introduces an open-source automated solid finite element analysis method using OpenBIM data (IFC). The tool implemented automatically creates tetrahedron mesh and assigns mechanical properties, self-weights, and fixities at the structure's base. The methodology is applied to an actual masonry building aggregate to validate its capability of working with complex geometries and scalability.

Thick-shell finite element analysis of reinforced concrete flat plates with non-uniform connection stresses

This paper presents the application of a thick-shell nonlinear finite element analysis procedure to estimate the punching shear resisting performance of reinforced concrete slab-column connections under variable connection shear stress conditions. In the analyses performed, varied connection shear stress conditions stem from slabs being supported by columns with different cross-section aspect ratios, being subjected to different distributions of gravity loading, being constructed with different planar reinforcement ratios in orthogonal directions, as well as the application of unbalanced bending moments. Forty-eight isolated slab-column connection specimens presented in the literature were modelled and analyzed using a thick-shell finite analysis procedure. All numerical results were developed using a predefined set of material models and analysis parameters, a consistent meshing procedure, and are shown to provide meaningful agreement with experimental data without the need for case-specific model calibration or the adoption of specialised failure criteria. The results show that thick-shell modelling methods can be suitable for estimating the punching shear response of slabs subjected to non-uniform shear stress development in connection regions, and can provide similar levels of precision to that obtained for the analysis of idealised slab-column connections typically used for design procedure and model development.

Optimization Design of Laminated Functionally Carbon Nanotube-Reinforced Composite Plates Using Deep Neural Networks and Differential Evolution

This study presents a new approach as an integration of deep neural networks (DNN) into differential evolution (DE) to give the so-called DNN-DE for frequency optimization of laminated functionally graded carbon nanotube (FG-CNT)-reinforced composite quadrilateral plates under free vibration. In the presented approach, the DNN is applied to predict the objective and constraints during the optimization process instead of using the time-consuming finite element analysis (FEA) procedures while the DE is used as an optimizer for solving the optimization problem. Several numerical examples are performed to illustrate the performance of the proposed method. Optimal results obtained by the DNN-DE are compared with those achieved by other methods in order to show the reliability and effectiveness of the proposed methodology. Additionally, the influence of various parameters such as the boundary condition, the carbon nanotube (CNT) volume fraction, the CNT distribution on the optimal results is also investigated. The obtained results indicate that the proposed DNN-DE is an effective and promising method in solving optimization problems of engineering structures.

Punching shear code provisions examination against the creation of an opening in existed RC flat slab of various sizes and locations

Punching shear is a critical problem in flat slabs directly supported at columns resulting in a high-stress concentration area, increasing the probability of brittle punching shear failure. However, the capacity is reduced by creating an opening that affects the overall behavior of the slab based on its size and location with respect to the loaded area. Furthermore, the design and analysis of the various structural elements are based on international regulations that have major differences in their basis and executions. In this study, the different code provisions in punching shear of RC two-way flat slab without shear reinforcement are examined under various opening sizes and locations using the Nonlinear Finite Element Analysis (NLFEA) procedure using ABAQUS software. A total of twenty-one model has been simulated for examining the prediction accuracy by the ACI318-19, MC2010, and EC2 under the effect of opening size (100, 200, and 300) mm, and locations (zero, 0.25d, 0.50d, 2.0d, 4.0 h, 5.5d, and 6.0d) under two main categories; the critical punching perimeter, and the critical opening location. However, it has been revealed that the proposed value of 0.50d as the critical punching perimeter is the most reliable one; besides, the value of 4 h is enough for defining the position where the effect of an opening could be neglected regardless of its size. Furthermore, it has been found that the column-to-opening ratio (C/O) is a very significant factor in controlling the punching shear capacity prediction accuracy by the different codes. Predictions get more overestimated under larger (C/O) values where increasing the C/O ratio by half increases the ultimate deflection percentage by an average of 22 %, except for those with smaller C/O values of less than 0.5, where it only reaches a maximum value of 13 %. Moreover, code prediction of the ACI318-19 and the MC2010 was found to be overestimated in all cases. In contrast, the EC2 was underestimated with an accurate prediction for an opening location of 2.0d from the column's face. However, it has been found that ACI318-19 is the most accurate one regarding the critical punching perimeter (0.5d) and critical opening location (4.0d).

Finite Element Analysis of Residual Stress Distribution Patterns of Prestressed Composites Considering Interphases

New finite element analysis procedures are developed in this study to obtain the precise stress distribution patterns of prestressed composites. Within the FEM procedures, an equivalent thermal method is modified to realize the prestress application, and a multi-step methodology is developed to consider coupling effects of polymer curing and prestress application. Thereafter, the effects of interphases' properties, including the elastic modulus and coefficient of thermal expansion (CTE), on the stress distribution patterns are revealed. Analytical methods for residual stress prediction are modified in this study to demonstrate the finite element analysis procedures. From the residual stress results, it is found that the increase in the prestress level tends to contribute to the initiation of interphase debonding. The increase in the elastic modulus or CTE of the interphase results in very large circumferential and axial stress values appearing in the interphase. When the elastic modulus in the interphase is heterogeneous, the predicted stress values in the fiber and matrix are similar to the results predicted with the equivalent elastic modulus of the interphases. However, the heterogeneous elastic modulus results in serious circumferential and axial stress gradients in the interphase.

Influence of shear direction on the buckling of CFRP composite perforated plate

The shear buckling performance of CFRP composite perforated plates taking due account of the influence of the flexural anisotropy is examined in this paper using the finite element analysis procedure. Typical laminated composite lay-up causes many complexities but can easily be dealt with in the numerical simulations. The results from the finite element models are shown to agree favourably with the buckling curves from the independent simulations using finite strip method of analysis. Results in the paper clearly show that care should be taken seriously for the case of composite structural members having opening in their webs. Depending on the nature of the applied shear loading, openings, and varied symmetric angle ply laminates, the buckling behavior and capabilities have also been altered.

Failure analysis and curvature-based failure criterion of super large cooling tower under strong equivalent static wind load

More and more super large cooling towers are used in recent years. However, investigations on them under strong wind are still insufficient and there is still not an agreement failure criterion. In this paper, we conducted the failure analysis of a super large cooling tower with 253 m height under the equivalent static wind load. The finite element analysis procedure incorporates the multi-layered shell element, the softened damage model of concrete and the two-level secant algorithm in one framework. The numerical results show that the nonlinear response of the tower can be divided into four stages, i.e., the initial linear stage, the nonlinear stage, the softening linear stage and the failure stage. The failure of the cooling tower is caused by the loss of material strengths, i.e., the cracking of the concrete and the following yield of the meridian rebar. Finally, a curvature-based failure criterion is proposed to evaluate the failure of the cooling tower, in which the structure fails when the global curvature variation ratio ϰ reaches some definite values. ϰ is defined as the ratio of the total curvature variation with the initial total curvature of the cooling tower geometry. It can evaluate the total curvature variation in a global view. It is recommended that ϰ can be used as an index in the design of the cooling tower, and 1.0% and 3.5% can be deemed as the nonlinear and failure index, respectively.

Seismic Response of Underground Subway and Aboveground Structures Considering the Tunnel-Soil-Aboveground Structure Interaction

ABSTRACT With the acceleration of urbanization, the distance between the underground structure and the aboveground structure is becoming smaller and smaller, and the mutual influence between them during earthquake is worthy of attention. In this study, a three-dimensional (3D) finite element (FE) analysis procedure was verified based on shaking table test data firstly. Subsequently, the validated FE analysis procedure was used to carry out an extended parameter analysis to study general seismic response of more complex aboveground structure-soil-underground structure systems. The key parameters, such as the height and number of aboveground structures, earthquake type, and distance between underground and aboveground structures, were considered. It was found that the tunnel-soil-aboveground structure interaction could effectively affect the acceleration and deformation response of both the ground and underground structures. With the increasing height and number of aboveground structures and the decreasing distance between underground and aboveground structures, the deformation of the underground structure tended to become larger. On the other hand, the existence of underground structure could effectively reduce the response of aboveground structure, and the influencing effect was found to be considerably affected by the distance between underground and aboveground structures. The findings obtained from this study could provide useful references for the seismic design of both aboveground and underground structures in urban areas.

A new finite element procedure for simulation of flexural fatigue behaviours of hybrid engineered cementitious composite beams

This study proposes a new finite element (FE) analysis procedure for simulation of flexural fatigue behaviours of hybrid fibre reinforced engineered cementitious composite (hybrid ECC) beams. The proposed method simplifies the analysis of hybrid ECC beams under fatigue loading, which could have fatigue life up to millions of cycles, into a small number of static FE analyses corresponding to a set of designated load cycles with equivalent fatigue damages. An ECC material damage model is first developed to describe the degrading of material properties caused by fatigue loading. This material damage model defines the relationships of two critical damage properties of ECC, namely the degraded stiffness and the accumulated plastic strain with the number of load cycles applied. By using the developed material damage model, a simplified analysis procedure is then proposed for the fatigue analysis of hybrid ECC beams under bending. The accuracy and reliability of the proposed material damage model and analysis procedure are validated by comparing experimental results obtained from bending tests of three types of hybrid ECC beams under three different stress ranges with the modelling predictions. It is found that the proposed material damage model and analysis procedure provided good predictions of the fatigue responses of the hybrid ECC beams in terms of material damages, deformation and fatigue life.

Estimation of losses and efficiency of double-stator switched flux permanent magnet machines

Losses such as rotor iron and stator iron losses, magnet eddy current loss, as well as efficiency of a double stator permanent magnet machine having varying rotor pole numbers is estimated and presented in this study. This current investigation would be vital for electrical machine designers in quantifying the amount of losses in the various sections of a given double stator electric machine and as well provide better insight on resulting output efficiency of the machine. Time-stepping finite element analysis (TS-FEA) procedure is adopted in the calculations using ANSYS-MAXWELL simulation software. The compared machines having the same stator teeth/pole number (Ps) and different rotor pole (Pr) numbers are designated as: 6Ps/10Pr, 6Ps/11Pr, 6Ps/13Pr and 6Ps/14Pr. The predicted total loss values at rated current and operating base speed is 13.02 Watts, 13.13 Watts, 13.539 Watts, 13.537 Watts, from the 6Ps/10Pr, 6Ps/11Pr, 6Ps/13Pr and 6Ps/14Pr machine types, respectively. The corresponding efficiency of the machine types at rated working conditions is: 81.76%, 88.17%, 86.95% and 78.61%, respectively. The results show that magnitude of losses in a given machine would largely depend upon factors such as number of rotor poles and hence, the machine’s operating speed, electric loading and angular rotor position of the machine, etc. It is also found that the number of loss waveform cycles (Nc) in an electric revolution of the investigated machine would depend upon its stator and rotor arrangements. The most performing compared machine types are the ones that have 11- and 13-rotor pole numbers, while the least amount of efficiency is obtained from the machine type that has 14-rotor pole number. Above all, the 6Ps/10Pr and 6Ps/14Pr are characterized with high amount of pulsations or ripples and this is detrimental to the overall performance of the machines.

Investigated behavior of the top-base foundation using finite element analysis

Top-base foundation (TBF) is a cutting-edge technology in construction area. It is in terms of increasing the load-carrying capacity of the ground, reducing settlement, especially the difference in settlement between the footings, resisting earthquake loads, fast construction, friendly environment, and low construction cost. To date, most of the research has mainly focused on field and laboratory experimental studies. These studies require large costs, and take a long time. In addition, most practical experiments only determine the displacement field, while the stress field is difficult to determine precisely. Therefore, in this study, a finite element analysis (FEA) is proposed based on verification with the experimental results of previous studies. Consequently, the accuracy and reliability of the FEA can be assessed. Through the FEA procedure, it is possible to predict the stress field with high reliability, which can be applied in practice, bringing economic efficiency, especially suitable for current conditions in Vietnam.

Fragility analysis of a prestressed concrete containment vessel subjected to internal pressure via the probability density evolution method

The prestressed concrete containment vessel (PCCV) is the final barrier to prevent radioactive material leakage from a nuclear power plant to the outside. Therefore, the fragility evaluation is very important for the design and analysis of the PCCV. In this paper, the fragility analysis of the PCCV (tested at Sandia National Laboratories (SNL)) subjected to internal pressure is conducted using the probability density evolution method (PDEM). First, a high-fidelity finite element analysis procedure is introduced to perform the deterministic analysis of the PCCV. In the following stochastic analysis and fragility evaluation, the material properties are selected as the uncertain resources. By applying the PDEM, the probability surface and probability density function (PDF) of the stochastic responses are obtained. Furthermore, the limit state of the PCCV is evaluated by the global average strain, which is defined as the ratio of radial displacement to the radius of the PCCV, and the PCCV reaches its functional and structural failure states when the global average strain reaches 0.4% and 1.5%, respectively. To consider more than one failure mode in the fragility evaluation, an equivalent extreme-value event combined with the PDEM is adopted to obtain the failure probability and the fragility curve of the PCCV to evaluate its fragility behavior. The results show that the fragility of the PCCV is still zero until the internal pressure increases to 2.890 times and 3.155 times the design pressure and then increases rapidly and reaches 1 at 3.560 times and 3.955 times the design pressure of the functional and structural failure criteria, respectively.

A Review on Atrial Fibrillation (Computer Simulation and Clinical Perspectives)

Atrial fibrillation (AF), a heart condition, has been a well-researched topic for the past few decades. This multidisciplinary field of study deals with signal processing, finite element analysis, mathematical modeling, optimization, and clinical procedure. This article is focused on a comprehensive review of journal articles published in the field of AF. Topics from the age-old fundamental concepts to specialized modern techniques involved in today’s AF research are discussed. It was found that a lot of research articles have already been published in modeling and simulation of AF. In comparison to that, the diagnosis and post-operative procedures for AF patients have not yet been totally understood or explored by the researchers. The simulation and modeling of AF have been investigated by many researchers in this field. Cellular model, tissue model, and geometric model among others have been used to simulate AF. Due to a very complex nature, the causes of AF have not been fully perceived to date, but the simulated results are validated with real-life patient data. Many algorithms have been proposed to detect the source of AF in human atria. There are many ablation strategies for AF patients, but the search for more efficient ablation strategies is still going on. AF management for patients with different stages of AF has been discussed in the literature as well but is somehow limited mostly to the patients with persistent AF. The authors hope that this study helps to find existing research gaps in the analysis and the diagnosis of AF.

Multiresolution analysis and deep learning for corroded pipeline failure assessment

The assessment of the safety of corroded pipelines is considered a vital task in the oil and gas industry. This research aims to develop an efficient system to accurately predict the burst pressure of corroded pipelines with complex corrosion profiles through hybrid models using multiresolution analysis, numerical analysis and meta-models. The work addresses the parametrization of real corrosion shapes and its use as input to a neural network system that can predict the burst pressure accurately and quickly. Ultrasonic inspections provide the thicknesses in the corrosion area and with that data the river-bottom profile (rbp) can be constructed. A set of scripts creates finite element models from the rbp, which are then subjected to non-linear analyses to determine the failure pressure. In this work, the Finite Element models and analysis procedure are validated against experimental tests and are compared to semi-empirical assessment methods. A discrete wavelet transform is performed for the parametrization of the remaining thicknesses and it is used as a filter bank to reduce the amount of data that describes the defect. The coefficients obtained from the wavelet transform are used as inputs to feed a neural network to provide a quick evaluation of the failure pressure. This neural network is trained with the results of finite element analyses performed on synthetic models built with statistical properties similar to those of real corrosion defects The results from the neural networks are obtained very fast and accurate for all cases presented in this work.

Analytical design method for the improvement of steel structures stability

AbstractThis article presents a design method for the improvement of steel structures stability by modifying their structural elements parameters. The available parameters can be selected from a predefined list of stiffness and ultimate capacities for joints and steel members. The proposed procedure is based on determining the critical load factor (ratio between the critical and the demanding loads: αcr = Pcr / PEd) and analyzing its sensitivity with respect to the design parameters, by using its gradient vector and Hessian matrix. The methodology is well suited for structures where the second order effects are relevant. A simple two parameter example is presented, and the general procedure for finite element analysis is outlined.

Buffeting-Induced Resonances of Hangers at a Long-Span Suspension Bridge and Mitigation Countermeasure

Abstract Buffeting-induced oscillations of hangers at a suspension bridge have been addressed in this work. The buffeting is obtained by a dynamic finite-element analysis procedure in the time doma...

Preventive strategy of flatfoot deformity using fully automated procedure

A non-invasive, no radiation, out-of-hospital automated system is proposed to identify low arch integrated in the design and manufacturing of personalized orthoses using parametric modelling. The aim of the design process is to integrate assistive technology with assessment and prevent low arch progressing to a more serious case - flatfoot. In the automated procedure, we developed an assessment method including reliable thresholds of foot type classification and test protocol to reduce interferences due to preceding activities, an automation to translate scanned data into parametric design for orthotic customization, finite element model evaluating effectiveness of the personalized design, and a personalized comparative test to evaluate the long-term improvement of foot arch shape. Our low arch threshold established by subject-specific 3D models reduced the misclassification rate from 55%, as previously reported to 6.9%. Individuals who engaged in sedentary activity (i.e. sitting) had the greater change in arch height compared to active activity (i.e. standing and walking), which is more likely to affect the obtained measure. Therefore, a test protocol now states that participants are not allowed to sit over 100 min prior the measurement to reduce such interference. We have proposed and tested an automated algorithm to translate scanned data including seven foot's parameters into customised parametric design of the insert. The method decreases the required time of orthotic computer-aided design from over 3 h to less than 2 min. A finite element analysis procedure was additionally developed to assess the performance of geometries and material of designed orthotic based on the distribution of plantar pressure and internal stress. The personalized comparative assessment based on midfoot contact area was carried out periodically for follow-up and the orthotic could be re-designed if necessary. The proposed automated procedure develops a pre-screening system to distinguish low arch and provide preventatives before it becomes symptomatic. Furthermore, non-symptom flatfoot can be detected at early stages and referred to medics for further diagnosis or treatment.

Topology optimization of multi-material structures with elastoplastic strain hardening model

The paper presents a new multi-material topology optimization method with a novel adjoint sensitivity analysis that can accommodate not only multiple plasticity but also multiple hardening models for individual materials in composite structures. Based on the proposed method, an integrated framework is developed which details the nonlinear finite element analysis, sensitivity analysis and optimization procedure. The proposed method and framework are implemented and illustrated by three numerical examples presented in this paper. An in-depth analysis of the numerical results has revealed the significant impact of the selection of plasticity and hardening model on the results of topology.