FEM Computer Program Research Articles

Stable Paths in the Postbuckling of an Imperfect Slender Web Loaded in Compression

The stability analysis of a slender web loaded in compression is presented. The non-linear FEM equations are derived from the variational principle of minimum of potential energy. The peculiarities of the effects of the initial imperfections are investigated using user program. Special attention is paid to the influence of imperfections on the post-critical buckling mode. Stable load-displacement paths are investigated. The FEM computer program using a 48 DOF element has been used for analysis. FEM model consists of 4x4 finite elements. Full Newton-Raphson procedure has been applied.

Validation of a simplified micromodel for analysis of infilled RC frames exposed to cyclic lateral loads

An RC frame structure with masonry infill walls (“framed-masonry”) exposed to lateral loads acts as a composite structure. Numerical simulation of framed-masonry is difficult and generally unreliable due to many difficulties and uncertainties in its modelling. In this paper, we reviewed the usability of an advanced non-linear FEM computer program to accurately predict the behaviour of framed-masonry elements when exposed to cyclic lateral loading. Numerical results are validated against the test results of framed-masonry specimens, with and without openings. Initial simplified micromodels were calibrated by adjustment of the input parameters within the physically justifiable borders, in order to obtain the best correlation between the experimental and numerical results. It has been shown that the use of simplified micromodels for the investigation of composite masonry-infilled RC frames requires in-depth knowledge and engineering judgement in order to be used with confidence. Modelling problems were identified and explained in detail, which in turn offer an insight to practising engineers on how to deal with them.

Postbuckling Analysis Of A Rectangular Plate Loaded In Compression

Abstract The stability analysis of a thin rectangular plate loaded in compression is presented. The nonlinear FEM equations are derived from the minimum total potential energy principle. The peculiarities of the effects of the initial imperfections are investigated using the user program. Special attention is paid to the influence of imperfections on the post-critical buckling mode. The FEM computer program using a 48 DOF element has been used for analysis. Full Newton-Raphson procedure has been applied.

Effect of a Nonlinear Term in a Strain-Displacement Relationship on the Load-Displacement Path of Von Mises Truss

Von Misses truss is one of the best examples to explain different theoretical approaches, nature of non-linear solution, define the snap-through, illustrate interactive buckling, etc. The presented paper compares two nonlinear approaches to the problem. Effect of nonlinear terms in strain-displacement relationship on the load level in critical point of nonlinear solution is analyzed. To obtain the nonlinear equilibrium paths, the Newton-Raphson iteration algorithm is used. Corresponding levels of the total potential energy are defined. The peculiarities of the effects of the initial imperfections are investigated. Custom FEM computer program has been used for analysis. Full Newton-Raphson procedure, in which the stiffness matrix is updated at every equilibrium iteration, has been applied. Obtained results are compared with results of the nonlinear analysis using ANSYS system, element type BEAM3 is used. The arc-length method is chosen for analysis, the reference arc-length radius is calculated from the load increment. Only fundamental path of nonlinear solution has been presented.

Evaluating Fire Resistance of Steel Girders in Bridges

In current practice, no special measures are applied for enhancing structural fire safety of steel bridge girders. Further, there is very limited information and research data in the literature on the fire resistance of structural members in bridges. In this paper, the fire response of a steel bridge girder under different conditions is evaluated using the FEM computer program ANSYS. In the analysis, the critical factors that influence fire resistance, namely, fire scenario, fire insulation, and composite action arising from steel-concrete interaction, are accounted for. Results from numerical studies show that the composite action arising from steel-girder-concrete-slab interaction significantly enhances the structuralperformance(and fireresistance)ofasteelbridgegirderunder fireconditions.Othersignificantfactorsthatinfluence fireresistanceof steel bridge girders are fire insulation and type of fire scenario. DOI: 10.1061/(ASCE)BE.1943-5592.0000412. © 2013 American Society of Civil Engineers. CE Database subject headings: Fires; Fire resistance; Girder bridges; Steel bridges. Author keywords: Bridge fires; Fire resistance; Steel girders; FEM analysis.

Finite element method analysis of pipe material temperature changes influence on line expansion loops in hydraulic installations on modern tankers

Finite element method analysis of main lines of hydraulic central loading system installation expansion loops mounted on product and chemical tankers has been presented in the paper. The axial forces problem in installations mounted along the ship?s open decks executed from hull deformations on waves and thermal stresses is given. Use of ?U? type expansion loops is described. Results of forces in anchor points and stresses of Mises due to expansion loop deformations are shown. Calculations were made by ABAQUS Ver.6.7 FEM computer program.

Stability analysis of multilayered composite shells with cut-outs

A numerical stability analysis of an axially compressed multilayered composite shell is presented. The authors examine how the stability performance of a panel can be influenced by a centrally located square cut-out. The computations are performed within FEM computer program NX-Nastran (ver. 6.0). The stability is investigated by means of a linearized buckling analysis as well as of a non-linear large deformations incremental analysis . To get more insight into the performance of the layered structure, the failure index according to Tsai–Wu criterion is monitored in the study.

TRANSITION, CONVERGENCE AND CONSTANCY IN RADIUSED ENTRY CROSS-BORED CYLINDERS

A 3D FEM computer program was developed to establish the stress distributions and SCFs in thick walled cylinders with radiused entry flush and non-protruding cross bores under internal pressure. Th...

Geometric Constants in Plain Cross-Bored Cylinders

A three-dimensional FEM computer program was developed to establish the stress distributions and SCFs in thick walled cylinders with flush and nonprotruding plain cross bores under internal pressure. The displacement formulation and eight-noded brick isoparametric elements were used. The Frontal solution technique was used due to the limited computing facilities. In the far field, the FEM stresses and displacements were in good agreement with the through thickness analytical values. The variation of SCF with d was established for various thickness ratios. For k>1.25, the maximum hoop stress occurred away from the crotch corner when d⩽0.2. For k=1.25, the maximum hoop stress occurred away from the crotch corner when d⩽0.15. For k⩾1.75, d was found to be a geometrical constant equal to 0.2 where the k values have a SCF of 2.734. For k<1.75, d was found to be a geometrical constant equal to 0.11 where the k values have a SCF of 2.67. A new categorization of cylinders has been proposed: thin shells, thick shells, and thick cylinders.

Performance evaluation of continuous levitation in an active‐maglev system using YBCO bulk and multiple electromagnets

AbstractWe have designed and constructed a new type of active‐maglev system using YBCO bulk and two electromagnets and have demonstrated that levitation height was remarkably improved by continuous levitation. In the active‐maglev system, however, the upper and lower coils differed in the coil size and an iron plate beneath the lower coil was used to enhance the magnetic field around the bulk. Considering the real application to maglev transporter in the axial direction, we must realize continuous leviation using a larger number of electromagnets without such iron plate and enable the levitation height to be controlled freely. In this paper, we demonstrate continuous levitation while controlling the leviation height using three‐ and five‐electromagnet systems and investigate electromagnetic behavior within the bulk using an FEM computer program. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 25–33, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10055

Characteristics of active-maglev system using YBCO bulk and multiple electromagnets

One useful feature of the active-maglev system is that levitation height is adjustable by varying operating current in electromagnets. To improve the levitation height, we have designed and constructed a new type of active-maglev system with two electromagnets instead of using a larger single electromagnet. The levitation height, as well as stability, was remarkably improved by adjusting the operating current of each electromagnet individually. Although the bulk is levitated up to high position, the lower electromagnet is continued to operate in continuous levitation using multiple electromagnets. It is waste that the lower electromagnet is continued to operate. The required energy for the electromagnet operation should be minimized. In this paper, we tried to realize continuous levitation with keeping the total operating current constant in five-electromagnet active-maglev system and investigate electromagnetic behavior within the bulk using a newly developed FEM computer program. Continuous levitation was successfully achieved under the desired operating condition. Agreements between experiment and analysis were excellent.

Numerical and experimental investigation of the deformational behaviour of plastic containers

AbstractA numerical and experimental study was undertaken to investigate the deformational behaviour of a plastic grooved container used to store agrochemical solutions when loaded under columnar crush conditions. Finite element analysis was implemented to calculate stresses and deformations at various critical points of the container. A non‐linear elastoplastic analysis was performed, based on the ABAQUS FEM computer program. The results of the stress analysis were coupled with a yield criterion to predict the initiation of plastic deformation. The numerically obtained results are compared to those obtained experimentally. It was found that the numerically calculated strains at predetermined locations of the plastic container were in good agreement with the experimentally measured ones. Copyright © 2001 John Wiley & Sons, Ltd.

Improvement of superconducting cylindrical linear induction motor

The authors have constructed a model superconducting cylindrical (tubular) linear induction motor (SCLIM) to clarify the behaviors (AC loss, stability and so on) of AC superconducting windings in a realistic operational environment of electrical rotating machines. The studies of an AC superconductor's development in regard to the reduction of AC loss and the improvement of current capacity have been advanced. From now on, the valuation of characteristic of AC superconducting windings in a realistic operational environment should be investigated. In the previous paper, the authors presented the design and construction of an SCLIM model system composed of AC superconducting primary windings, FRP cryostat and VVVF power supply with quench detection and protection circuit, and the results of fundamental driving experiments. In this paper, the authors optimize the current distribution in primary windings to enhance the thrust characteristics and the quench detection and protection system for AC superconducting machines by a numerical approach based on a developed FEM computer program. The measurements of the thrust force, the distributions of the magnetic flux density and primary current in the SCLIM model are also shown.

バルク超電導体と複数の電磁石による鉛直方向連続アクティブ磁気浮上の特性評価

We have designed and constructed a new type of active-maglev system using YBCO bulk and two electromagnets and have demonstrated that levitation height was remarkably improved by continuous levitation. In the active-maglev system, however, the upper and lower coils differed in the coil size and an iron plate beneath the lower coil was used to enhance the magnetic field around the bulk. Considering the real application to maglev transporter in the axial direction, we must realize continuous leviation using a larger number of electromagnets without such iron plate and enable the levitation height to be controlled freely. In this paper, we demonstrate continuous levitation while controlling the leviation height using three- and five-electromagnet systems and investigate electromagnetic behavior within the bulk using an FEM computer program. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 25–33, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10055

Nonlinear Earthquake Response of Soft Ground with Non-Flat Base

To determine seismic ground motion for seismic design, it is necessary to take site effects into account, such as non-linearity of soil and geological irregularities. In this paper, we discuss these two aspects of site effects. The two-dimensional FEM computer program, therefore, is developed which can take into account the soil non-linearity. From an analytical study, the characteristics of nonlinear wave propagation in soil deposit with a basin edge are clarified.

Dynamical Influence Lines At Drop Impact OfTransport Masses

The safety enhancement measures of the Paks NPP (Hungary) included the investigation of the drop impact check of reinforced concrete structures strength. A FE model of the structures was generated and a standard FEM computer program was used to calculate the displacements and internal forces. However, the problem is that the place of force vector and initial velocity vector on the slab are unknown. If we want to obtain the maximum of displacements and different internal forces, we have to drop the body on different points of the slab. To decide the maximum of an internal force we have to use dynamic influence lines of the different internal force. On this basis the strength of the existing structures were assessed. The results showed that above the reactor hermetic containment in the case of a minimal drop height the strength capacity is adequate, but in the case of higher drop heights special measures should be taken.

ボイドスラブを空調用ダクトとして利用する場合の熱性能の数値解析

Unsteady state thermal behavior of void slabs used as an air-conditioning duct was numerically analyzed with FEM computer program. Non-insulated void slab and eight types of insulated void slab were simulated. The following results were obtained: (1) When a void slab is used as a floor, inside surface of the void should be insulated. If the thickness of insulation exceeds 30 mm, the temperature difference on the floor surface becomes less than 1 degree C and the surface condensation during cooling period can almost be avoided. (2) When a void slab is used as a roof, inside surface of the void as well as exterior surface of the roof should be insulated. Thc recommended thickness of insulation is more than 30mm for inside surface of the void and 100 mm for exterior surface of thc roof, respectively.

Mathematical model for coupled solid deformation and methane flow in coal seams

A mathematical model of coupled solid-gas for gas flow in coal seams is presented; the numerical method of the mathematical model and FEM computer program are given. The law of gas flow, radius of drainage, and the effective stress distribution in coal seams under the condition of gas exhaustion through the drilling hole are obtained by using the above methods. The calculation sample was selected from the first coal mine of Yangquan and the calculation result is compared with the field data. A few conclusions are given.

Nonlinear Effects on Shakedown of Sidesway Frames

A general nonlinear FEM computer program for analysis of frames is used to examine the shakedown load of sidesway frames. It is shown that large displacement effects and interaction between moment and axial force in the cross sections reduce the shakedown load substantially. This process is visualized in a diagram depicting load factor versus mean load factor. The curves drawn in this plane may be simplified by straight lines, reducing the effort of calculating the shakedown loads.

Characteristics of externally pressurized porous ceramics air bearings.

In this study, basic characteristics of porous-ceramics air bearings, such as stiffness, load carrying capacity and stability, and analyzed by means of the finite element method. The validity of an FEM computer program developed in this study is examined through experimentation. The effects of anisotropic permeability, porosity and thickness of porous-ceramics materials on the stiffness and pneumatic instability are investigated. The effect of air supply area on the load carrying capacity and stiffness are also analyzed. The effect of the characteristics of porous materials on the occurrence of pneumatic instability is analyzed through the simulation of the dynamic response of bearing. Consequently, it is pointed out that the porosity and thickness of the porous-ceramic materials should be kept as small as possible in order to obtain higher stiffness and stability.