Simplified 3D Finite Element Research Articles

Efficiency of timber-concrete composite floors with discrete perfobond connections: A numerical study

To evaluate the behaviour of a single timber-concrete composite (TCC) T-beam, a simplified 2D finite element (FE) model in Abaqus is developed and validated using experimental tests and the Gamma method given in Annex B of EN 1995–1-1. The shear connection used in the beam consist of perfobond connectors, which are adhesively bonded to the timber beam. In the developed model, beam and shell finite elements have been used to simulate/reproduce the timber beam and the concrete slab, respectively. These have then been connected using connector elements which incorporate the mechanical behaviour of the tested shear connections, obtained in a previous research. After the successful validation of the FE model, this is used to further analyse different parameters such as: i) different number of connections (varying from 8 to 20), ii) different types of loading (point load, distributed load and line load), iii) different concrete slab widths and iv) connection models with elastic perfectly plastic behaviour applied to TCC T-beam and a 5 m by 5 m floor system. The results of the conducted study provide an in-depth understanding of the effect and impact of the investigated parameters which can support a future optimisation of the structural solution. Moreover, the results show that the use of a simplified 2D model can support designers to overcome the limitations of analytical approaches, such as the Gamma method, to analyse large spacing and to take benefit of bidirectional effects (load sharing) if analysed as a whole instead of a single T-beam.

An efficient micromechanics-based finite element model for failure analysis of laminated composites

Accurately predicting ultimate strength of composite laminate is still a great challenge, especially only based on the constituent properties. In this paper, the micromechanics Bridging Model and systematic failure criteria for the constituent materials with emphasis on matrix failures subjected to three dimensional (3D) loads are compiled into a UMAT subroutine for ABAQUS to analyze failures of a laminated composite structure. The main purpose of this research is to greatly reduce calculation costs for loading conditions of in-plane tension or compression by introducing a simplified 3D finite element model based on the Pipes-Pagano theory. In all calculation cases, only the constituent properties together with the transverse tensile strength of unidirectional composite are needed as input data. Later in this paper, sufficient illustrations of 81 different composite laminates composed of 14 material systems are analyzed to confirm the practicability of this model.

Influence of the Longitudinal Shear Transfer on the Vertical Shear Capacity in CSTC Beams

AbstractUnlike typical composite beams using downstand steel profiles, Composite steel truss in concrete (CSTC) beams consist of steel trusses welded to a steel plate and embedded in concrete. In this case, the longitudinal shear transfer relies on the mechanical interlock between the surrounding concrete and the embedded diagonals which carry simultaneously most of the vertical shear force. The current work aims to assess to what extent the longitudinal shear transfer affects the capacity of these diagonals, such that the current approach for determining the vertical shear resistance is suitable. Hence, a simplified 3D finite element (FE) model was firstly developed and several simulations were carried out. The results were post‐processed in consideration of the slip distribution and load conditions which may occur along the actual beam. Finally, a more advanced FE model was created to evaluate and compare the vertical shear resistance of a 6m CSTC beam with the corresponding value according to the current design method. Whilst the former methodology (simplified model) shows that a 15% yielding resistance reduction of the diagonal is sufficient to ensure the safety of the current design approach, the latter (advanced beam model) shows that no reduction is required.

Simplified 2D Finite Element Model for Calculation of the Bearing Capacity of Eccentrically Compressed Concrete-Filled Steel Tubular Columns

Concrete-filled steel tubular (CFST) columns are widely used in construction due to effective resistance to compression and bending joint action. However, currently, there is no generally accepted effective calculation method considering both nonlinearities of the materials and lateral compression. The article proposes the finite element analysis method of concrete-filled steel tubular columns in a physically nonlinear formulation by reducing a three-dimensional problem to a two-dimensional one based on the hypothesis of plane sections. The equations of Geniev’s concrete theory of plasticity are used as relations establishing the relationship between stresses and strains. The technique was tested by comparing the solution with the calculation in a three-dimensional formulation in the LIRA-SAPR software package and with the experimental data of A.L. Krishan and A.I. Sagadatov. It has been established that the effective area of operation of circular-section columns are small eccentricities of the longitudinal force. The proposed approach can be applied to analyzing the stress–strain state and bearing capacity of pipe-concrete columns of arbitrary cross-sections. There are no restrictions on the composition of concrete, and the shell material can be steel and fiberglass.

Reliability assessment of fiber-reinforced polymer cable-anchorage system

In this study, an evaluation framework for the reliability of a fiber-reinforced polymer (FRP) cable-anchorage system was established. We first developed a simplified 3D finite element (FE) model for an effective FRP cable anchorage, in which layers of FRP tendons were equivalent to several concentric rings. The performance of the anchorage system was evaluated using the maximum Tsai–Wu failure index (FImax) of all cable elements. By feeding 1600 samples generated from the above FE model, a back-propagation neural network (BPNN) was trained to rapidly predict FImax. Assuming that the overall failure was controlled by the weakest part, the reliability index β of the entire system can be calculated from FImax through a Monte Carlo (MC) simulation. The β of the prototype anchorage system reached 4.3635. Under a deterministic design load Fd, giving a target reliability index βT = 3.7, the design-to-ultimate ratio was estimated to be 0.532. The sensitivity analysis suggested that the FImax was most sensitive to the longitudinal tensile strength of the FRP cable and the thickness of the load transfer component (LTC, also known as load transfer medium or LTM) at the loading end.

Sustainable Measures for Protection of Structures Against Earthquake Induced Liquefaction

Soil liquefaction can cause excessive damage to structures as witnessed in many recent earthquakes. The damage to small/medium-sized buildings can lead to excessive death toll and economic losses due to the sheer number of such buildings. Economic and sustainable methods to mitigate liquefaction damage to such buildings are therefore required. In this paper, the use of rubble brick as a material to construct earthquake drains is proposed. The efficacy of these drains to mitigate liquefaction effects was investigated, for the first time to include the effects of the foundations of a structure by using dynamic centrifuge testing. It will be shown that performance of the foundation in terms of its settlement was improved by the rubble brick drains by directly comparing them to the foundation on unimproved, liquefiable ground. The dynamic response in terms of horizontal accelerations and rotations will be compared. The dynamic centrifuge tests also yielded valuable information with regard to the excess pore pressure variation below the foundations both spatially and temporally. Differences of excess pore pressures between the improved and unimproved ground will be compared. Finally, a simplified 3D finite element analysis will be introduced that will be shown to satisfactorily capture the settlement characteristics of the foundation located on liquefiable soil with earthquake drains.

Mitigating effect of embankment to adjacent pipe with CDM columns

Pipelines are valuable infrastructures that covering a large area or expanding to long distance for the transporting function. This leads to the variety of loads and effects applied on such buried structures. A thread to pipeline integrity is the construction of the embankment on the soft soil which leads to the displacement of the pipe adjacent to the slope. This displacement will effect to the increase of internal force or causing failure of the near-by pipes. The use of concrete pile to improve the soil properties may be a solution; however, the cost for this is expensive. To propose an alternative solution for the problem, this study uses a system of cement deep mixing, CDM, columns as the solution for protecting the pipe. A simple 2D Finite Element, FE, model using Plaxis software has been established based on the equivalent soil approach which considering the CDM columns and their surrounding soil as an unified soil. The effectiveness of the proposed solution has been numerically investigated and proven. The lateral displacement of pipe and the maximum ring bending moment and other internal forces are significantly reduced with the appearance of the CDM columns. The selective parametric study has been implemented revealing the critical input variables are the distance of pipe to the slope and the length of the CDM column.

Reinforcing Effect of Strain Gauges on 3D Printed Polymers: An Experimental Investigation

Strain gauges are ordinary transducers for strain measuring; their operation relies on the electrical resistance, which varies as the underlying substrate is subjected to mechanical deformation. The mechanical strain can be obtained by converting the electrical signal through a gauge factor, provided by the manufacturer. It was demonstrated that its values are not unique; it may be influenced by the geometrical characteristics of both the specimen and the strain gauge and by their respective moduli of elasticity. This can be extremely dangerous when low modulus materials are studied. This study confirms that even with commercial strain gauges specifically designed for low modulus materials the effect might be present. An experimental method for its evaluation is discussed; tensile specimens are used as a test bench and their modulus is determined using both strain gauges and a non-contact method (Digital Image Correlation). The results show that a local reinforcing effect is present and a higher tensile modulus is obtained when contact transducers are bonded to polymeric specimens. The amplitude of this effect is predicted with established methods available in the literature and through a simple 2D Finite Element (FE) model. All these models require the elastic modulus of the strain gauge to be considered; a digital procedure to estimate it for any wired transducer is therefore proposed. The predicted results were found to be consistent with those experimentally measured; this validated the method, thus advising on how to evaluate the phenomenon also when this information is not available.

Influence of the Compaction Pressure and Sintering Temperature on the Mechanical Properties of Porous Titanium for Biomedical Applications

In the present work, the use of porous titanium is proposed as a solution to the difference in stiffness between the implant and bone tissue, avoiding the bone resorption. Conventional powder metallurgical technique is an industrially established route for fabrication of this type of material. The results are discussed in terms of the influence of compaction pressure and sintering temperature on the porosity (volumetric fraction, size, and morphology) and the quality of the sintering necks. A very good agreement between the predicted values obtained using a simple 2D finite element model, the experimental uniaxial compression behavior, and the analytical model proposed by Nielsen, has been found for both the Young’s modulus and the yield strength. The porous samples obtained by the loose sintering technique and using temperatures between 1000 °C −1100 °C (about 40% of total porosity) are recommended for achieving a suitable biomechanical behavior for cortical bone partial replacement.

The dilemma of functional therapy: the new EFA to do or not to do?

ObjectivesThis finite element analysis was conducted to study the effects produced by a new fixed functional appliance (EFA; Elhiny functional appliance) and hence predict its clinical effectiveness.Materials/methodsUnder ANSYS environment, a simplified 2D finite element model was prepared for this study. The models simulated a clinical situation where the mandible was positioned forward via a new fixed functional appliance design. The models’ components were created on a commercial CAD/CAM package then imported to finite element software. Pushing load of 2 N was applied along the appliance longitudinal direction.ResultsThe mandible showed downward and forward deformation in the X and Y directions with the highest deformation at the symphysis and lower border with a total deformation of 80 μm. There was little deformation in the maxilla. The highest strain results were at the condyle, both compressive and tensile in the X and Y directions with a total of 1520 micro strain behind the condyle. The strain in the mandibular tooth bearing area was around zero and in the maxillary tooth bearing area ranged from − 9 to 16.6 micro strain.ConclusionsWithin the limitations of this finite element analysis, it could be predicted that the new appliance (EFA) produces pure functional skeletal results with absolutely no dentoalveolar effects, which provides the opportunity for observing significant skeletal changes.

On Simplified 3D Finite Element Simulations of Three-Core Armored Power Cables

This paper analyzes different ways to electromagnetically simulate three-core armored cables in 3D by means of the finite element method. Full periodic models, as lengthy as 36 m, are developed to evaluate the accuracy when simulating only a small portion of the cable, as commonly employed in the literature. The adequate length and boundary conditions for having the same accuracy of full periodic models are also studied. To achieve this aim, five medium voltage and high voltage armored cables are analyzed, obtaining the minimum length of the cable that may be simulated for having accurate results in shorter time and with less computational burden. This also results in the proposal of a new method comprising the advantages of short geometries and the applicability of periodic boundary conditions. Its accuracy is compared with experimental measurements and the International Electrotechnical Commission (IEC) standard for 145 kV and 245 kV cables. The results show a very good agreement between simulations and measurements (errors below 4%), obtaining a reduction in the computation time of about 90%. This new method brings a more effective tool for saving time and computational resources in cable design and the development of new analytical expressions for improving the IEC standard.

2D Finite Element Model for computing the electric field strength-rms generated by overhead power lines

In this article, a simple 2D finite element model is proposed for computing the RMS electric field strength generated by overhead power lines. The model it is implemented in FEMM 4.2, a high quality, open source finite element software for solving low frequency electromagnetic problems, for the particular case of a 110 kV single-circuit overhead power line. The results obtained with this model there are analyzed and then compared to those obtained by analytical calculations, revealing a very good agreement. The proposed FEMM 4.2 model it is primarily intended to assess the compliance with the electric field exposure limits established by health regulations, but other applications are also possible.

Simulation of temperature rise within a rolling tire by using FE analysis

A simulation method is proposed to predict temperature rise within a dynamic rolling tire. The friction heat from tire-road contact and the internal heat generated by hysteresis loss caused by rubber deformation are considered in the simulation model. A systematic process was developed to calculate the heat generation rate by using dissipated energy, and it was applied to the simulation model by establishing user subroutines. An axial tensile test was conducted for the rubber specimen, and the obtained stress-strain curve was applied to the simulation model based on the first-invariant Marlow model. The reliability of the simulation method was verified by comparing the tensile simulation and test results. A simplified 3D finite element tire model was developed, and simulations were performed in dynamic rolling conditions. Heat was generated because of friction and internal deformation. The temperature distribution within the tire, which was derived using the model, indicates that the proposed simulation method is reliable.

Genetic algorithm based inverse analysis for the superplastic characterization of a Ti-6Al-4V biomedical grade

The inverse analysis approach is recently spreading as a valuable methodology to calibrate constitutive models describing the superplastic behaviour of light alloys. In this work, the superplastic behaviour of a titanium grade for biomedical applications was characterized by means of a Genetic Algorithm based inverse analysis. Free inflation tests at 850 °C were carried out on the Ti-6Al-4V Extra Low Interstitial alloy at two different levels of constant pressure; in addition, a jump pressure test in which the gas pressure was changed during the same test between the same levels was performed. The dome height curve was acquired during each test and subsequently adopted as target data: a simple 2D Finite Element model, in which the material behaviour was implemented using the Backofen power law, was then created to calibrate the material constitutive equation by means of an inverse analysis approach. A set of constants, able to minimize the error between numerical and experimental data, was determined for each investigated load condition. Subsequent numerical simulations, run for validation purposes, demonstrated that the sets determined using as target the data from the free inflation tests under a constant level of pressure were capable of effectively describing the material behaviour only for load conditions close to the ones from which they had been determined. On the contrary, the set of material constants obtained using the same inverse approach but adopting as target data the acquisitions from the jump pressure test, revealed to describe the material behaviour over a wider span of operative conditions.

Effects of cyclic deformation on a barrier thin film for flexible organic optoelectronic devices

Effects of cyclic bending on the encapsulation properties of a barrier thin film are investigated. Water vapor transmission rate (WVTR) of the given barrier film is measured after variously cyclic bending conditions using a calcium corrosion test technique. Experimental results show that microcracks in the barrier thin film are found after applying a certain number of bending cycles. They are responsible for an increase in WVTR. Given a bending radius, a greater number of bending cycles leads to a larger amount of damage, and consequently a greater extent of moisture ingress. A smaller bending radius produces a greater amount of damage than a larger one, in a short period of loading time (≤104 cycles). However, after 105 cycles of cyclic bending, the amount of damage reaches a saturated level regardless of bending radius, as all the WVTR values become comparable. A simplified 3D finite element analysis (FEA) model is established in microscale to analyze the moisture diffusion mechanism. Numerical results show that, with the presence of cracking and delamination, the WVTR value increases significantly. Good agreement between the simulation and experimental measurements on WVTR confirms that the failure mechanism involves cracking and delamination under cyclic bending. The 3D FEA modeling developed could offer a method to predict the change of WVTR in correlation with cracking and delamination in the barrier thin film.

Modelling the creep of deep foundations in soft Gothenburg clays

The design of deep foundations in areas with significant background creep deformation is a challenge. In Sweden, mainly empirical methods have been used in the design of deep foundations. Generally, the predictions have been highly inaccurate, in particular with regards to the long-term deformations. Therefore, a stepwise approach is proposed, which stems from the concept of performance based design. It is shown that with the proposed approach, it is for the first time possible to perform representative back analyses of the long-term response of deep foundations in an environment with ongoing settlements. This is achieved with simplified 2D finite-element analyses using a commercially available creep model. Design assumptions and simplifications are defined based on careful back analysis of relevant case studies in the area that can be found in literature. Finally, the approach is validated by comparison with long-term monitoring of a 22-storey building on a floating piled raft.

Atherosclerotic plaque delamination: Experiments and 2D finite element model to simulate plaque peeling in two strains of transgenic mice

Finite element analyses using cohesive zone models (CZM) can be used to predict the fracture of atherosclerotic plaques but this requires setting appropriate values of the model parameters. In this study, material parameters of a CZM were identified for the first time on two groups of mice (ApoE-/- and ApoE-/- Col8-/-) using the measured force-displacement curves acquired during delamination tests. To this end, a 2D finite-element model of each plaque was solved using an explicit integration scheme. Each constituent of the plaque was modeled with a neo-Hookean strain energy density function and a CZM was used for the interface. The model parameters were calibrated by minimizing the quadratic deviation between the experimental force displacement curves and the model predictions. The elastic parameter of the plaque and the CZM interfacial parameter were successfully identified for a cohort of 11 mice. The results revealed that only the elastic parameter was significantly different between the two groups, ApoE-/- Col8-/- plaques being less stiff than ApoE-/- plaques. Finally, this study demonstrated that a simple 2D finite element model with cohesive elements can reproduce fairly well the plaque peeling global response. Future work will focus on understanding the main biological determinants of regional and inter-individual variations of the material parameters used in the model.

EFFECT OF BULLET SHAPE AND H/A RATIO ON BALLISTIC IMPACT BEHAVIOUR OF FRP COMPOSITE PLATE: A NUMERICAL STUDY

In this paper, the behaviour of FRP composite plate has been studied under ballistic impact with different shapes of impactor and incidence velocity ranging from 100 m/s to 1000 m/s. Damage behavior of plate, the variation of residual velocity and ballistic limit have been studied with different h/a ratios and nose shapes of impactor. A simplified 3D finite element model for composite plate and impactor with gap interaction and Lagrangian mesh has been presented. Progressive damage based on material stress/strain failure criteria incorporation with shock effect is considered to study the stage wise damage evolution in FRP composite plate due to ballistic impact by conical as well as blunt shaped cylindrical bullet in AUTODYN hydro code. FE models are validated with available literature in terms of numerical values of residual velocity and damage pattern in composite plate and show a close agreement.

The effect of manufacturing tolerances on the load carrying capacity of large diameter bearings

This paper deals with simplified 3D finite element (FE) analysis on the effect of manufacturing tolerances on the load carrying capacity of large diameter bearings based on Hertz theory. The nonlinear connector elements are used to model the rolling elements. This model enables us to evaluate the contact load on the rolling elements with relatively reduced calculation time. FE study has been carried out by allocating tolerance on balls and raceways using Monte Carlo simulation technique. The variation in dimension on balls is taken as per IS 2898-1976. A coding has been developed and employed for Monte Carlo simulation. Using the results of Monte Carlo simulation, tolerance has been assigned to the elements of large diameter bearing. From the results of finite element analysis, it is identified that analysis of large diameter bearing with tolerance on ball and raceway will lead to safe design.

Simplification Study of FE Model for 1000kV AC Transmission Line Insulator String Voltage and Grading Ring Surface Electric Field Distribution Calculation

The finite element model of the 1000kV Ultra High Voltage (UHV) AC transmission line porcelain insulator string voltage distribution and grading ring surface electric field distribution calculation has the characteristics of large size, complicated structure and various mediums. To insure the accuracy, related influencing factors should be considered to simplify the model reasonably for improving computational efficiency. A whole model and a simplified 3D finite element model of UHV AC transmission line porcelain insulator string were built. The influencing factors including tower, phase conductors, hardware fittings, yoke plate and phase interaction were considered in the analysis. And finally, the rationality of the simplified model was validated. The results comparison show that building a simplified model of three-phase bundled conductors within a certain length, simplifying the tower reasonably, omitting the hardware fittings and yoke plate and containing only single-phase insulator string model is feasible. The simplified model could replace the whole model to analyze the voltage distribution along the porcelain insulator string and the electric field distribution on the grading ring surface, and it can reduce the calculation scale, improve optimization efficiency of insulators string and grading ring parameters. DOI : http://dx.doi.org/10.11591/telkomnika.v12i2.3833