Efficient Finite Element Model Research Articles

Resistance of stud shear connectors in composite beams using profiled steel sheeting

In composite beam design, headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface. This paper describes the structural performance of shear connection in composite beams with profiled steel sheeting. An accurate and efficient nonlinear Finite Element (FE) model was developed to study the behavior of headed stud shear connectors welded through the deck. The concrete slab considered in this article uses profiled steel sheeting with ribs perpendicular to the longitudinal axis of the steel beam. The material nonlinearities were included in the FE model. The concrete was modeled considering a damaged plasticity model available in ABAQUS software. The results obtained from FE analysis were verified against experimental results. A parametric study was conducted to observe the effects of changing of both the stud position inside the rib of profiled steel sheeting and the concrete strength on the resistance of the stud shear connector. The shear resistance of stud connectors obtained from the FE analysis and many experimental push-out tests whose results are available in the literature were used as a database to compare with design shear resistance calculated using AISC-LRFD and Eurocode 4. It is found that the shear resistance of stud connectors, obtained from the design rules specified in these codes, in some cases is greatly underestimated, and in other cases significantly overestimated.

Finite Element Analysis of Double Wishbone Vehicle Suspension System

Suspension systems play an important role in vehicles. These systems provide passenger comfort and vibration isolation from road bumps. Thus an efficient finite element model is required to study and analyze the dynamic response of these suspension systems. This paper presents a finite element model to analyze the dynamic response of double wishbone vehicle suspension system taking into consideration both links and joints flexibilities. Links are modeled using plane frame element based on Timoshenko beam theory (TBT) kinematic relations. On the other hand, the revolute joint element, developed in ANSYS, is adopted to model joints flexibility.Both internal viscoelastic and external viscous as well as the modal proportional damping models are adopted to simulate the damping effect. The resulting dynamic finite element equations of motion are solved using Newmark numerical technique. The proposed numerical methodology is checked by comparing the obtained results with the developed analytical solution and good agreement is noticed. The applicability of the proposed procedure is demonstrated by operating parametric studies to illustrate the effects of the road irregularity configurations, the vehicle travelling velocity, as well as the material damping on the dynamic response characteristics of the double wishbone suspension system. The obtained results are helpful for the mechanical design of these structural systems.

Three‐dimensional multiscale finite element models for in‐service performance assessment of bridges

AbstractAccurate representation of the structural performance of civil engineering structures, specifically complex bridge structures, may be achieved through an efficient multiscale finite element (FE) model. Multiscale FE modeling couples multiple dimensions of elements in a single model. In this study, the selected existing multipoint constraint equations applied in planar coupling conditions are modified and refined for out‐of‐plane coupling conditions in a single three‐dimensional FE model. Also, the optimum location for the interface points of different elements is determined to improve the model's accuracy and efficiency. The present case study, the Memorial Bridge in Portsmouth, NH, is a vertical lift bridge, which includes novel gusset‐less connections. These connections have complex geometries and therefore require finer dimension elements to represent the structural behavior, while the remainder of the structure is modeled with coarser dimension elements. To achieve an accurate and efficient multiscale model of the Memorial Bridge, multiple global FE models are developed and the predicted structural responses are verified with respect to the field‐collected structural responses of the bridge.

Finite Element Modeling and Design of Single Angle Member Under Bi-axial Bending

Practical single angle members are mostly subjected to eccentric forces due to the end connections to their legs. Plastic Class 1 and compact Class 2 angle cross-sections are allowed for using their plastic reserves. However, most of the interaction equations in the current design codes are linear whereas the nonlinear equations associated with plastic surface are provided in the literature. In this study, a new design method for single angle member to address the plastic failure as well as stability checks is proposed. The first yield moments at different critical points due to the interaction between the normal forces and the biaxial bending are provided. Moreover, the elastic flexural and flexural-torsional buckling loads for single angle member are calculated using a simplified equation rather than the complex design charts or series of equations in literature or design codes. New buckling curves, taking the Eurocode 3 design rules into account, are presented for single angle member subjected to eccentric load about both major and minor principal axes. A reliable and efficient finite element model is provided to verify the proposed equations and to investigate the different parameters affecting the buckling behavior. Finally, various initial geometric imperfections together with a residual stress distribution pattern are studied and provided in this paper.

On the carbon nanotube mass nanosensor by integral form of nonlocal elasticity

In many researches, mass nanosensors have been modeled as a cantilever nanobeam in presence of nonlocal elasticity that produces paradoxical results so that the nanostructure shows hardening behavior in the first mode of vibration when the differential form of nonlocal elasticity is assumed. Accordingly, in this study, vibration behavior of carbon nanotube-based mass nanosensor resting on nonlocal elastic foundation is investigated through an efficient finite element model including the integral form of nonlocal elasticity. Also, the influences of mass value, elastic foundation constant, mass position and nonlocal parameter on the first two natural frequencies are examined. The results reveal that, employing integral nonlocal elasticity obviates the paradoxes so that increasing nonlocal parameter reduces the frequency shift of mass nanosensor in both first and second modes. Also, applying nonlocality on elastic foundation leads to considerable changes and reduction in frequency shift in comparison to those obtained from the local elastic foundation assumption.

Investigation of Mesh Size Effect on Dynamic Behaviour of an Assembled Structure with Bolted Joints using Finite Element Method

The predicted results of the finite element (FE) model of an assembled structure with different types of joints are highly dependent on the mesh size of the FE model. The complexity of the FE model has forced engineers to seek the most efficient techniques for the selection of the appropriate mesh size specifically in obtaining accurate predicted results in normal modes analysis. This paper concerns the investigation into the effects of the mesh sizes and selection technique of the appropriate mesh size in the FE modelling and analysis of the assembled structure with bolted joints. The investigation was carried out by predicting the modal parameters of the FE models with the predefined range of mesh sizes. The predicted results of the FE models were compared with the measured counterparts obtained from the experimental modal analysis (EMA). The total error obtained from the comparison between FE and EMA was recorded. Evaluations were made by comparing the number of nodes and elements of the FE models, percentage of total error, computer processing unit (CPU) elapsed time and memory usage. The outcomes of the evaluations showed that there are significant effects of the mesh sizes on the accuracy, computing time and memory usage of the FE modal analysis of the assembled structure with bolted joints. This work also demonstrated an efficient technique for the selection of the appropriate mesh size in achieving a reliable, efficient and economic FE modelling and analysis of the assembled structure with bolted joints.

Mechanism-based constitutive modeling of ZEK100 magnesium alloy with crystal plasticity and in-situ HEXRD experiment

The constitutive behavior of a hexagonal close-packed (HCP) polycrystalline ZEK100 magnesium alloy was investigated using combined high energy X-ray diffraction (HEXRD) from a synchrotron source and crystal plasticity modeling approach. The in-situ tensile test data coupled with the HEXRD enabled the tracking of the lattice strain evolution during deformation. The microscopic behavior represented by lattice strain and the macroscopic behavior represented by stress-strain curves were then used together as objective function to estimate the critical resolved shear stress (CRSS) and hardening parameters of available slip and deformation twin systems in the ZEK100 alloy. An enhanced predominant twinning reorientation (ePTR) scheme was proposed in the current work, and the ePTR parameters were determined for the first time by the use of basal plane peak intensity along loading direction measured from HEXRD. Two crystal plasticity models, the computationally efficient elastic-plastic self-consistent (EPSC) and crystal plasticity finite element (CPFE) models, were developed incorporating the deformation twinning for the HCP-structured metals. The determined constitutive parameters were further validated by comparing the predicted deformation texture with the measured one. The work provides a useful and computationally-efficient modeling scheme to understand the slip/twin induced deformation behaviors of the ZEK100 alloy in micro- and macro-scales.

Numerical Analysis of ACSR Conductor–Clamp Systems Undergoing Wind-Induced Cyclic Loads

Submitted to wind-induced vibrations, overhead conductors are vulnerable to fatigue damage, especially at restraining fixtures such as the suspension clamp. This paper proposes an efficient finite-element modeling approach providing a full 3-D representation of both the conductor and suspension clamp. Validation based on experimental data shows the precision of the approach. An in-depth model response analysis also demonstrates its ability to describe inter-wire and conductor–clamp contact interactions. Finally, a study of conductor stress distributions reveals that in critical regions, conductor wires mostly sustain alternating bending loads.

A 3D efficient finite element model to simulate rolling contact fatigue under high loading conditions

Abstract The objectives of this investigation were to develop a 3D efficient elastic-plastic finite element model to characterize the rolling contact fatigue behavior of through hardened steel at high loads (∼5 GPa) and to corroborate analytical and experimental results. The efficient FE model developed for this investigation was coupled with the continuum damage mechanics to simulate rolling contact fatigue (RCF). The new computationally efficient approach developed uses Delaunay mesh to reduce the number of elements without compromising the accuracy of stress distribution induced during a rolling contact pass. In order to validate the newly developed approach, the results obtained from the current 3D model for line contact were corroborated to previously published results. The fatigue lives obtained from the new model are consistent with the previously published model predictions and empirical observations. In order to simulate the RCF for high load conditions, the increase in the contact width observed in the experiments and consequently the decrease in the contact pressure with loading cycles were implemented in the model. Furthermore, the damage evolution law was modified to incorporate the compressive residual stresses induced by the plastic deformation. The L10 life and the scatter in the fatigue lives obtained from the model correlated well with the experimental results. As a part of this investigation, a Thrust Bearing Test Apparatus (TBTA) was designed and developed to simulate RCF. RCF experiments were conducted on through hardened AISI 52100 steel flat specimens at high contact stress levels (5 GPa) to induce plastic deformation. The results demonstrated that the contact width increased as the cycles increased due to plastic strain accumulation. The results from FE model corroborate well with experimental results obtained from TBTA.

Effects of missing fasteners on the mechanical behavior of double-lap, multi-row composite bolted joints

This paper presents a numerical investigation into the effects of missing fasteners on the mechanical characteristics of double-lap, multi-row composite bolted joints. A highly efficient explicit finite element model, which was validated effective and accurate by experiments, was developed and employed to conduct the virtual tests. Single-column and multi-column joints with various positions of missing fastener were considered. It is shown that the removal of fasteners can reduce the joint stiffness significantly, especially in joints with fewer columns or missing fasteners in the outside rows. The removal of fasteners can also cause considerable reductions in both the initial significant failure loads and ultimate loads of multi-column joints, while in single-column joints only the initial significant failure loads are influenced. Considering the load distribution, it is suggested that bolts in the same column as or in the adjacent column to the missing fastener experience a notable growth in load. Meanwhile, if a bolt bears more loads in the pristine joint, the larger changes in stiffness, ultimate strength, and load distribution may be obtained when it is lost.

A new efficient hyperelastic finite element model for graphene and its application to carbon nanotubes and nanocones

A new hyperelastic material model is proposed for graphene-based structures, such as graphene, carbon nanotubes (CNTs) and carbon nanocones (CNC). The proposed model is based on a set of invariants obtained from the right surface Cauchy-Green strain tensor and a structural tensor. The model is fully nonlinear and can simulate buckling and postbuckling behavior. It is calibrated from existing quantum data. It is implemented within a rotation-free isogeometric shell formulation. The speedup of the model is 1.5 relative to the finite element model of Ghaffari et al. [1], which is based on the logarithmic strain formulation of Kumar and Parks [2]. The material behavior is verified by testing uniaxial tension and pure shear. The performance of the material model is illustrated by several numerical examples. The examples include bending, twisting, and wall contact of CNTs and CNCs. The wall contact is modeled with a coarse grained contact model based on the Lennard-Jones potential. The buckling and post-buckling behavior is captured in the examples. The results are compared with reference results from the literature and there is good agreement.

The forming limit curve for multiphase advanced high strength steels based on crystal plasticity finite element modeling

A computationally efficient rate independent crystal plasticity finite element (CPFE) model was used to predict the forming limit curve (FLC) for a multiphase advanced high strength steel (AHSS). The CPFE model accounts for mechanical properties of the steel phases based on their individual plastic deformation and slip systems. The macroscopic behavior of the polycrystalline aggregate was predicted based on the volume-averaged response of the representative phases, and their volume fraction in the steel sheet. In addition to the random texture distribution assumption for each grain, the volume fractions of various phases were also assumed to be randomly distributed at each integration point. The microstructural inhomogeneity of the material, as well as a geometrical inhomogeneity in the form of a groove region in the specimen, based on the Marciniak-Kuczynski (MK) theory, were considered in the calculation of the FLC using the CPFE model (MK-CPFE). The validity of predicted FLC for quenched and partitioned QP980 steel was confirmed by comparing the results with experimental measurements. The FLC calculated by CPFE model showed that the presence of microstructural inhomogeneity allows for a more realistic prediction of the localized necking phenomenon. Subsequently, the FLC was used to compute the limit strains for the T-shape part stamping process. The limit strains and the punch force-stroke relationship for the T-shape part predicted by the multiphase CPFE model were in good agreement with experimental results.

Finite Element Simulation of Space Trusses

AbstractThe purpose of this paper is introducing a simplified and computationally efficient finite element model to investigate the nonlinear behavior of composite and non-composite space trusses. Two models were employed using the Finite Element ANSYS program in order to analyze the space trusses. The first model simulates the non-composite space trusses while the second model simulates the composite space trusses. Also this research presents the comparisons between the results of the current finite element models and four previous published space trusses in order to verify the validity of the current models. Comparisons between the results of the two models and the results of the four previous published space trusses indicated that the numerical analysis created by the FE ANSYS program using the two employed models can predict the general collapse behavior of the space trusses.

An efficient three-field mixed finite element model for the linear analysis of composite beams with deformable shear connection

In this paper, we develop a new and efficient finite element for the linear static analysis of composite beams with deformable shear connection. We adopt a 3-field mixed approach, based on the Hu-Washizu principle, combined with the enhanced strain concept. Our proposal includes the possibility of systematically choosing interpolating functions of increasing order for certain generalized stresses and for the enhanced strains. Another distinctive feature of our approach is the fact that only three generalized stresses are directly approximated. As in many mixed formulations, the degrees of freedom associated with the approximation of generalized stresses and enhanced strains can be condensed out at the element level at negligible cost, leading to discrete systems involving only the displacement degrees of freedom. For benchmarking purposes, a conventional displacement-based conforming finite element is also briefly derived. Several illustrative examples demonstrate the mixed element’s ability to perform very well on the coarsest of meshes – often consisting of a single finite element –, even when the material data exhibits a jump discontinuity in its interior, in sharp contrast with the displacement-based conforming element. This is particularly true when it comes to the estimation of generalized stresses, often the variables of most interest to designers.

Experimental testing and modeling of precast segmental bridge columns with hybrid normal- and high-strength steel rebars

Precast segmental bridge columns (PSBCs) have significant advantages, including faster construction speed and lower environmental impacts, over cast-in-place bridge columns. Traditional PSBCs usually employ normal-strength steel rebars as longitudinal reinforcement. Hence, it is named the NSR-PSBC herein. In this paper, a novel PSBC, named hybrid-reinforced PSBC (HR-PSBC), is developed. The HR-PSBC utilizes hybrid normal- and high-strength steel rebars to improve the seismic response of PSBCs. The main contributions of this study include: (1) large-scale cyclic tests were conducted to compare the seismic performance of the HR-PSBC with the NSR-PSBC; and (2) a novel and computationally efficient finite element model for the HR-PSBC was developed. The test results demonstrated that the hybrid reinforcement employed in the HR-PSBC was very effective in improving the post-yield stiffness, self-centering capacity, ductility and load-carrying capacity of the bridge column. These test results were further used to verify the accuracy of the proposed finite element model. It was found that the numerical model was able to provide satisfactory predictions of both global and localized responses of the PSBCs. Based on the results presented in this paper, it is concluded that the HR-PSBC can be a promising alternative to traditional NSR-PSBCs and cast-in-place bridge columns, and the proposed numerical modeling method can be a suitable tool for design-oriented studies of the NSR- and HR-PSBCs.

Active-passive damping in functionally graded sandwich plate/shell structures

In this work, a simple and efficient finite element model is applied to the vibration analysis of active–passive damped multilayer sandwich plates/shells with a viscoelastic core, sandwiched between functionally graded material (FGM) layers, and including piezoelectric layers. Both the FGM and the piezoelectric layers are modelled using the classical plate theory and the core is modelled using Reddy’s third-order shear deformation theory. The sandwich finite element is obtained performing the assembling of N “elements” through the thickness, by using specific assumptions on the displacement continuity at the interfaces between layers. To achieve a mechanism for the active control of the structural dynamics response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers. The dynamic analysis of the sandwich plate/shell structures is conducted in the frequency domain to obtain the natural frequencies and the loss factors of the viscoelastic core and in time domain for the steady state harmonic motion. For both analyses, a finite element code has been implemented. The model is applied in the solution of some illustrative examples and the results are presented and discussed.

An efficient partial mixed finite element model for static and free vibration analyses of FGM plates rested on two-parameter elastic foundations

In this study, a four-node quadrilateral partial mixed plate element with low degrees of freedom (dofs) is developed for static and free vibration analysis of functionally graded material (FGM) plates rested on Winkler-Pasternak elastic foundations. The formulation of the presented finite element model is based on a parametrized mixed variational principle which is developed recently by the first author. The presented finite element model considers the effects of shear deformations and normal flexibility of the FGM plates without using any shear correction factor. It also fulfills the boundary conditions of the transverse shear and normal stresses on the top and bottom surfaces of the plate. Beside these capabilities, the number of unknown field variables of the plate is only six. The presented partial mixed finite element model has been validated through comparison with the results of the three-dimensional (3D) theory of elasticity and the results obtained from the classical and high-order plate theories available in the open literature.

Mode-I Metal-Composite Interface Fracture Testing for Fibre Metal Laminates

The main contribution of the present paper is the determination of the mode-I fracture of metal-composite interface region for fibre metal laminates (FMLs). A hybrid DCB configuration is proposed to investigate the mode-I fracture between metal-composite interface using experimental and numerical approaches. A computationally efficient and reliable finite element model was developed to account for the influence of metal plasticity on the measured fracture energy. The results of the experimental and numerical studies showed that metal plasticity increases the fracture energy of the metal-composite interface as the fracture event progresses. The applied energy truly utilized to propagate metal-composite interface fracture was predicted numerically by extracting the elastic strain energy data. The predicted true fracture energy was found to be approximately 50% smaller than the experimentally measured average propagation energy. The study concluded that metal plasticity in hybrid DCB configuration overpredicted the experimentally measured fracture energy, and this can be alleviated through numerical methodology such as the finite element approach as presented in this paper.

Numerical assessment of vibration control systems for multi-hazard design and mitigation of glass curtain walls

Glass systems and facades are widely used in building structures, due to a multitude of aspects. Beside these motivations, from a pure structural point of view, glazing envelopes represent one of the most critical components for multi-storey buildings under the action of exceptional loads as impacts, explosions, seismic events or hazards in general. Such systems represent in fact the first line of defense from outside. Given the current lack of specific design regulations for the mitigation and enhancement of glass curtains under extreme loads, as well as the typically brittle behaviour and limited tensile resistance of glass as material for constructions, the same facades require specific, fail-safe design concepts.In this paper, the feasibility and potential of special mechanical connectors interposed at the interface between a multi-storey primary building structure and the enclosing glazing facade are investigated via accurate Finite-Element (FE) numerical models, under various impact scenarios. At the current stage of research, careful consideration is given both to the observed global performances as well as to local mechanisms, based on computationally efficient FE models inclusive of damage models to account for failure mechanisms in each system component. Compared to earlier research efforts, the attention is focused on the multi-hazard performance of a given case study building, subjected to extreme loadings such as seismic loads or blast events. As shown, even the typically different features of the examined loading conditions, when the proposed vibration control devices are properly designed and the curtain wall is considered as part of a full 3D building, the final result is an overall assembled structural system in which the glazing facade can work as a passive control system for the building system, in the form of a distributed Tuned-Mass Damper (TMD), with marked benefits in terms of protection level as well as design optimization.

Efficient Finite Element Models for Calculation of the No-load losses of the Transformer

Different transformer models are examined for the calculation of the no-load losses using finite element analysis. Two-dimensional and three-dimensional finite element analyses are used for the simulation of the transformer. Results of the finite element method are also compared with the experimental results. The Result shows that 3-dimensional provide high accuracy as compared to the 2 dimensional full and half model. However, the 2-dimensional half model is the less time-consuming method as compared to the 3 and 2-dimensional full model. Simulation time duration taken by the different models of the transformer is also compared. The difference between the 3-dimensional finite element method and experimental results are less than 3%. These numerical methods can help transformer designers to minimize the development of the prototype transformers.