• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.26 no.4
• /
• pp.293-300
• /
• 2013

In this study we proposed a simplified finite element model of anchor bolt system inserted through concrete structures considering clamping forces. The three different finite element types using LS-DYNA are applied for numerical efficiency of the anchor bolt modeling. Combined beam and solid elements are used to reflect the tension state at internal part of anchor bolt due to torques. The clamping forces due to torques are considered by introducing a compression for a nut plane modeled by beam elements. The numerical examples show good agreement with different element types. Parametric studies are focused on the various effects of different element types on the induced axial and shear forces of anchor bolts considering clamping forces.

• Steel and Composite Structures
• /
• v.42 no.2
• /
• pp.243-256
• /
• 2022

A coupled finite element method (FEM)-boundary element method (BEM) for analyzing the hydroelastic response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) floating plates under moving loads is firstly introduced in this article. For that aim, the plate displacement field is described utilizing a generalized shear deformation theory (GSDT)-based FEM, meanwhile the linear water-wave theory (LWWT)-relied BEM is employed for the fluid hydrodynamic modeling. Both computational domains of the plate and fluid are coincidentally discretized into 4-node Hermite elements. Accordingly, the C1-continuous plate element model can be simply captured owing to the inherent feature of third-order Hermite polynomials. In addition, this model is also completely free from shear correction factors, although the shear deformation effects are still taken into account. While the fluid BEM can easily handle the free surface with a lower computational effort due to its boundary integral performance. Material properties through the plate thickness follow four specific CNT distributions. Outcomes gained by the present FEM-BEM are compared with those of previously released papers including analytical solutions and experimental data to validate its reliability. In addition, the influences of CNT volume fraction, different CNT configurations, water depth, and load speed on the hydroelastic behavior of FG-CNTRC plates are also examined.

• Advances in nano research
• /
• v.13 no.4
• /
• pp.351-368
• /
• 2022

Recently, promising structural technologies like multi-function, ultra-load bearing capacity and tailored structures have been put up for discussions. Finite Element (FE) modelling is probably the best-known option capable of treating these superior properties and multi-domain behavior structures. However, advanced materials such as Functionally Graded Material (FGM) and nanocomposites suffer from problems resulting from variable material properties, reinforcement aggregation and mesh generation. Motivated by these factors, this research proposes a unified shape function for FGM, nanocomposites, graded nanocomposites, in addition to traditional isotropic and orthotropic structural materials. It depends not only on element length but also on the beam's material properties and geometric characteristics. The systematic mathematical theory and FE formulations are based on the Timoshenko beam theory for beam structure. Furthermore, the introduced element achieves C1 degree of continuity. The model is proved to be convergent and free-off shear locking. Moreover, numerical results for static and free vibration analysis support the model accuracy and capabilities by validation with different references. The proposed technique overcomes the issue of continuous properties modelling of these promising materials without discarding older ones. Therefore, introduced benchmark improvements on the FE old concept could be extended to help the development of new software features to confront the rapid progress of structural materials.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.7
• /
• pp.109-116
• /
• 2007

The emf of a permanent magnet multi-phase BLAC(Brushless AC) motor is generally a non-sinusoidal or a non-ideal trapezoid wave. So, conventional modeling using a sinusoidal or an ideal trapezoid emf can result in errors to simulate and analyze the properties of a multi-phase BLAC motor. To reduce the modeling error, this paper proposes a phase variable model, which is obtained from a hybrid modeling technique consisting of Finite Element Analysis(FEA) based circuits and equations. Since the phase model parameters including the emf waveform were obtained using FEA, the proposed hybrid modeling technique can be used to implement a simulation model for multi-phase BLAC motors with any emf voltage waveforms. Adequacy of the proposed model was established from the simulation and experimental results for a seven-phase BLAC motor.

• Composites Research
• /
• v.16 no.5
• /
• pp.7-14
• /
• 2003

Modeling of thick composite structures for finite element analysis is relatively complicated. 2-D plane elements may cause inaccurate result since the plane stress condition cannot be applicable in these structures. Therefore a 3-D modeling should be used. However, the difficulty to model all the layers with different material properties and ply orientation arise in this case. In this paper, an equivalent modeling is proposed and numerically tested for analysis of thick composite structures. By grouping layers with same material and ply orientation, number of elements through the thickness is remarkably reduced and still the result is close enough to the one from a detail finite element model. MSC/NASTRAN and PATRAN are used for the analysis. The proposed modeling technique has been applied for analysis of composite rotor hub system designed by Korea Aerospace Research Institute(KARI). Using the proposed equivalent modeling technique, we could conduct stress analysis for the hub system and check the safety factor of each part.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.9
• /
• pp.938-945
• /
• 2012

To design and estimate material failures of Type III pressure vessels, which have excellent stability and performance, various modeling techniques have been introduced. This paper provided a hybrid modeling technique composed of ply-based modeling for a cylinder part and laminate-base modeling technique for a dome part for enhancing modeling efficiency. The ply-based modeling technique provided accurate ply stresses directly for predicting material failure, on the other hand, additional manipulations in stress calculations, which may cause some errors, were needed for the case of the laminate-based modeling technique. The ply stresses in fiber, transverse and in-plane shear directions were compared with the corresponding material strengths to predict material failure.

• Structural Engineering and Mechanics
• /
• v.65 no.5
• /
• pp.611-619
• /
• 2018

This paper addresses numerical modeling and nonlinear analysis of unreinforced masonry walls and vaults externally strengthened using fiber reinforced polymers (FRP). The aim of the research is to provide a simple method for design of strengthening interventions for masonry arched structures while considering the nonlinear behavior. Several brick masonry walls and vaults externally strengthened by FRP which have been previously tested experimentally are modeled using finite elements. Numerical modeling and nonlinear analysis are performed using commercial software. Description of the modeling, material characterization and solution parameters are given. The obtained numerical results demonstrate that externally applied FRP strengthening increased the ultimate capacity of the walls and vaults and improved their failure mode. The numerical results are in good agreement with the experimentally obtained ultimate failure load, maximum displacement and crack pattern; which demonstrates the capability of the proposed modeling scheme to simulate efficiently the actual behavior of FRP-strengthened masonry elements. Application is made on a historic masonry dome and the numerical analysis managed to explain its structural behavior before and after strengthening. The modeling approach may thus be regarded a practical and valid tool for design of strengthening interventions for contemporary or historic unreinforced masonry elements using externally bonded FRP.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.459-462
• /
• 2005

In finite element analysis of the PSC structures, the prestressing effect can be introduced by two ways, i.e, equivalent loads or initial stress. This study investigates the reason why the two schemes that adopt the different approaches produce the similar results. The discussion is applicable to the general finite elements that correspond to the concrete and tendons. Some of the detailed derivations of each scheme are presented. Numerical examples show the identical results for the two methods.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.2
• /
• pp.244-251
• /
• 1999

Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric rotation parts and gas forces induced by the pressure difference between compression and suction gases. Rotor-journal bearing system is nonlinear since the stiffness and damping coef-ficients of the lubrication oil film are not constant in the bearings. in this paper the program for predicting the behaviors of rotor-journal bearing system of rotary compressor is developed. Finite element modeling is used to analyze the flexible rotor. The numerical results are compared with experimental results.

• Structural Engineering and Mechanics
• /
• v.33 no.5
• /
• pp.573-588
• /
• 2009

In this paper a four-node hybrid stress element is proposed for analysing arbitrarily shaped plates on a two parameter elastic foundation. The element is developed by combining a hybrid plate stress element and a soil element. The formulation is based on Hellinger-Reissner variational principle in which both inter element compatible boundary displacement and equilibrated stress fields for the plate as well as the foundation are chosen separately. This formulation also allows a low order polynomial interpolation functions. Numerical examples are presented to show that the validity and efficiency of the present element for the plate analysis resting on an elastic foundation. In these examples the effect of soil depth, interaction between closed plates on soil parameters, comparison with Winkler hypothesis is investigated.