• Geomechanics and Engineering
• /
• v.9 no.4
• /
• pp.465-481
• /
• 2015

Three-dimensional simulation of flow through dam foundation is performed using finite element (Seep3D model) and artificial neural network (ANN) models. The governing and discretized equation for seepage is obtained using the Galerkin method in heterogeneous and anisotropic porous media. The ANN is a feedforward four layer network employing the sigmoid function as an activator and the back-propagation algorithm for the network learning, using the water level elevations of the upstream and downstream of the dam, as input variables and the piezometric heads as the target outputs. The obtained results are compared with the piezometric data of Shahid Abbaspour's Dam. Both calculated data show a good agreement with available measurements that demonstrate the effectiveness and accuracy of purposed methods.

• Structural Engineering and Mechanics
• /
• v.44 no.3
• /
• pp.325-337
• /
• 2012

In this article, the multi-objective optimization of cylindrical aluminum tubes under axial impact load is presented. The specific absorbed energy and the maximum crushing force are considered as objective functions. The geometric dimensions of tubes including diameter, length and thickness are chosen as design variables. D/t and L/D ratios are constricted in the range of which collapsing of tubes occurs in concertina or diamond mode. The Non-dominated Sorting Genetic Algorithm-II is applied to obtain the Pareto optimal solutions. A back-propagation neural network is constructed as the surrogate model to formulate the mapping between the design variables and the objective functions. The finite element software ABAQUS/Explicit is used to generate the training and test sets for the artificial neural networks. To validate the results of finite element model, several impact tests are carried out using drop hammer testing machine.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.11
• /
• pp.1752-1759
• /
• 2004

Reinforced braid layer (RBL) in automobile power steering hose plays an important role in power steering system. When the working oil is applied to the power steering hose, RBL suppresses rubber hose deformation from internal pressure and heat expansion. RBL is woven textile composites having a double-row structure of nylon cords twisted with the specific helix angle. In this paper, effective material properties of RBL are estimated using a detailed 3-D finite element model considering its complicated geometry. Numerical experiments based on a superposition method are carried out to simulate uniaxial tensile loading condition.

• Structural Engineering and Mechanics
• /
• v.23 no.6
• /
• pp.635-649
• /
• 2006

The static and dynamic responses of guyed telecommunication towers can be determined by using two models, the space truss element model, and the equivalent beam-column element model. The equivalent beam-column analysis is based on the determination of the equivalent shear, torsion, and bending rigidities as well as the equivalent area of the guyed mast. In the literature, two methods are currently available to determine the equivalent properties of lattice structures, namely: the unit load method, and the energy approach. In this study, an equivalent beam-column analysis is introduced based on an equivalent thin plate approach for lattice structures. A finite-element modeling, using suitably modified ABAQUS software, is used to investigate the accuracy of utilizing the different proposed methods in determining the static and dynamic responses of a guyed tower of 364.5-meter high subjected to static and seismic loading conditions. The results from these analyses are compared to those obtained from a finite-element modeling of the actual structure using 3-D truss and beam elements. Good agreement is shown between the different proposed beam-column models, and the model of the actual structure. However, the proposed equivalent thin plate approach is simpler to apply than the other two approaches.

• Journal of the Korean Society for Railway
• /
• v.14 no.3
• /
• pp.240-247
• /
• 2011

Finite element analysis was undertaken to investigate the effect of freezing force of water unexpectedly penetrated into inserts used in railway sleeper on pullout capacity of anchor bolts for fixing base-plate onto concrete sleeper. Based on the in-situ investigation and measurement of geometry of railway sleeper and rail-fastener, the railway sleeper was modeled by 3D solid elements. Nonlinear and fracture properties for the finite element model were assumed according to CEB-FIP 1990 model code. And the pullout maximum load of anchor bolt obtained from the model developed was compared with experimental pullout maximum load presented by KRRI for verification of the model. Using this model, the effect of position of anchor bolt, amount of fastening force applied to the anchor bolt, and compressive strength of concrete on pull-out capacity of anchor bolts installed in railway sleeper was investigated. As a result, it is found that concrete railway sleepers could be damaged by the pressure due to freezing of water penetrated into inserts. And the pullout capacity of anchor bolt close to center of railway is slightly greater than that of the others.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.4
• /
• pp.449-455
• /
• 2011

Recently, international collaborative research which was organized at Bhabha Atomic Research Centre in India, was conducted to develop for pressure capacity and nonlinear behavior of PHWR 1/4 scale nuclear containment building between experimental test and numerical code. In this paper, a nonlinear finite element analysis was carried out in order to predict ultimate pressure capacity and nonlinear behavior of the 1/4 scale containment building. The 1/4 scale containment building is consisted of basemat, cylinder wall, dome and 4-buttress. For the finite element analysis, commercial program ABAQUS was used. Finite element models including concrete, rebar and tendon have been developed for assessment of ultimate pressure capacity and failure mode for nuclear containment building. From the analysis results, first crack of the concrete, the yielding of the rebar and ultimate capacity pressure occurred at $1.6P_d$(design pressure), $3.36P_d$ and $4.0P_d$, respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.5 s.98
• /
• pp.604-611
• /
• 2005

The relationship between floor impact sound and vibration has been studied by field measurements, and the vibration modal characteristics have been analyzed. Vibration levels impacted by a standard heavy-weight impact source have been predicted according to the main design parameters using finite element method. Experimental results show that the dominant frequencies of the heavy impact sounds range below 100 Hz and that they are coincident with natural frequencies of the concrete slab. In addition, simple 2-dimensional finite element models are proposed to substitute 2 types of 3-dimensional models of complicated floor structural slabs those by The analytical result shows that the natural frequencies from first to fifth mode well correspond to those by experiments with an error of less than $12\%$, and acceleration peak value iscoincident with an error of less than $2\%$. Using the finite element model. vibration levels areestimated according to the design Parameters, slab thickness, compressive strength, and as a result, the thickness is revealed as effective to increase natural frequencies by $20\~30\%$ and to reduce the vibration level by 3$\~$4 dB per 30 mm of extra thickness.

• Computers and Concrete
• /
• v.12 no.4
• /
• pp.519-536
• /
• 2013

This paper presents a mixed formulation frame element with the assumptions of the Timoshenko shear beam theory for displacement field and that accounts for interaction between shear and normal stress at material level. Nonlinear response of the element is obtained by integration of section response, which in turn is obtained by integration of material response. Satisfaction of transverse equilibrium equations at section includes the interaction between concrete and transverse reinforcing steel. A 3d plastic damage model is implemented to describe the hysteretic behavior of concrete. Comparisons with available experimental data on RC structural walls confirm the accuracy of proposed method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.3
• /
• pp.323-331
• /
• 2010

In this study, we propose a 3D finite element (FE) model for the residual stress under oblique shot peening. Using the FE model for an oblique impact, we examine the effects of factors on the residual stress such as the Rayleigh damping in the material, dynamic friction, and the rate dependency of the material and systematically integrate the effects. The plastic deformation of the shot is also emphasized. Then, the FE model is used to study oblique multi-impacts. The results obtained using the FE model are compared with experimental x-ray diffraction (XRD) results; in contrast to the rigid and elastic shots, plastic shots are found to produce residual stresses similar to that shown in the XRD results. Thus, the 3D FE models with integrated factors and plastically deformable shots are validated. The proposed model will serve as a basis for the 3D FE model for multi-impacts with different impact angles to simulate the actual phenomenon of shot peening.

• Computers and Concrete
• /
• v.14 no.6
• /
• pp.695-710
• /
• 2014

This paper presents a theoretical and computational approach to solve inelastic structures subjected to overloads. Current practice in structural design is based on elastic analysis followed by limit strength design. Whereas this approach typically results in safe strength design, it does not always guarantee satisfactory performance at the service level because the internal stiffness distribution of the structure changes from the service to the ultimate strength state. A significant variation of relative stiffnesses between the two states may result in unwanted cracking at the service level with expensive repairs, while, under certain circumstances, early failure may occur due to unexpected internal moment reversals. To address these concerns, a new inelastic model is presented here that is based on the nonlinear material response and the interaction relation between axial forces and bending moments of a beam-column element. The model is simple, reasonably accurate, and computationally efficient. It is easy to implement in standard structural analysis codes, and avoids the complexities of expensive alternative analyses based on 2D and 3D finite-element computations using solid elements.