• Smart Structures and Systems
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• v.1 no.1
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• pp.83-101
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• 2005

This paper summarizes the application of a rational methodology for the structural assessment of older reinforced concrete Tunisian bridges. This methodology is based on ambient vibration measurement of the bridge, identification of the structure's modal signature and finite element model updating. The selected case study is the Boujnah bridge of the Tunis-Msaken Highway. This bridge is made of a continuous four-span simply supported reinforced concrete slab without girders resting on elastomeric bearings at each support. Ambient vibration tests were conducted on the bridge using a data acquisition system with nine force-balance accelerometers placed at selected locations of the bridge. The Enhanced Frequency Domain Decomposition technique was applied to extract the dynamic characteristics of the bridge. The finite element model was updated in order to obtain a reasonable correlation between experimental and numerical modal properties. For the model updating part of the study, the parameters selected for the updating process include the concrete modulus of elasticity, the elastic bearing stiffness and the foundation spring stiffnesses. The primary objective of the paper is to demonstrate the use of the Enhanced Frequency Domain Decomposition technique combined with model updating to provide data that could be used to assess the structural condition of the selected bridge. The application of the proposed methodology led to a relatively faithful linear elastic model of the bridge in its present condition.

• East Asian mathematical journal
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• v.34 no.5
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• pp.661-681
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• 2018

In this paper, we discuss a reduced-order modeling for the Benjamin-Bona-Mahony-Burgers (BBMB) equation and its application to a distributed feedback control problem through the centroidal Voronoi tessellation (CVT). Spatial distcritization to the BBMB equation is based on the finite element method (FEM) using B-spline functions. To determine the basis elements for the approximating subspaces, we elucidate the CVT approaches to reduced-order bases with snapshots. For the purpose of comparison, a brief review of the proper orthogonal decomposition (POD) is provided and some numerical experiments implemented including full-order approximation, CVT based model, and POD based model. In the end, we apply CVT reduced-order modeling technique to a feedback control problem for the BBMB equation.

• Journal of Power System Engineering
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• v.15 no.3
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• pp.18-24
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• 2011

In this study, the reflection of the L(0,2), axially symmetric guided elastic wave from defects in pipes above ground is examined using finite element method. Phase and group velocity dispersion curves for the pipe were presented for the selection of the excitation mode. Some simple signal processing was applied to determine the amplitude of each of the reflected waves and to calculate the reflection coefficient. The results show the reflection coefficient of this mode is very close to a linear function of the circumferential extent of the defect. The motivation for the work was the development of a technique for inspecting chemical plant pipelines, but the study addresses the nature of the reflection function and its general applicability.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.147-158
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• 1997

This paper presents the analysis technique and procedure of main engine components-cylinder block, cylinder liners, gasket and cylinder head-using the finite element method, which aims to assess mainly the potential of lower oil consumption in a view point of engine design and to decide subsequently the accuracy of engine design which was done. The F.E. model of an engine section consisting of one whole cylinder and two adjacent half cylinders is used, whereby the crankcase is cut off at the block bottom deck. By means of a 3-dimensional F.E. model-including cylinder block, liners, gasket, cylinder head, bolts and valve seat rings as separate parts a linear analysis of deformations and stresses was performed for three different loading conditions;assembly, thermal and gas loads. For the analysis of thermal boundary conditions also the temperature field had to be evaluated in a subsequent step.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.05
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• pp.66-69
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• 1993

We have developed a software package for the analysis of electric field distribution in human body. It includes the graphical finite element mesh generator, linear system of equations solver using sparse matrix and vector technique, and post-processor for the display of the results. This software package can be used in various research areas of biomedical engineering where we inject current or apply voltage to human body. The software package was developed on Macintosh II computer and the size of the model is only limited by the main memory.

• Structural Engineering and Mechanics
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• v.3 no.3
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• pp.273-287
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• 1995

Stochastic response of systems to random excitation can be estimated by direct integration methods in the time domain such as the stochastic central difference method (SCDM). In this paper, the SCDM is applied to compute the variance and covariance in response of linear and nonlinear structures subjected to random excitation. The accuracy of the SCDM is assessed using two-DOF systems with both deterministic and random material properties excited by white noise. For the former case, closed-form solutions can be obtained. Numerical results also are presented for a simply supported geometrically nonlinear beam. The stiffness of this beam is modeled as a random field, and the beam is idealized by the stochastic finite element method. A perturbation technique is applied to formulate the equations of motion of the system, and the dynamic structural response statistics are obtained in a time domain analysis. The effect of variations in structural parameters and the numerical stability of the SCDM also are examined.

• Advances in nano research
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• v.7 no.3
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• pp.181-190
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• 2019

The thermal buckling temperature values of the graded carbon nanotube reinforced composite shell structure is explored using higher-order mid-plane kinematics and multiscale constituent modeling under two different thermal fields. The critical values of buckling temperature including the effect of in-plane thermal loading are computed numerically by minimizing the final energy expression through a linear isoparametric finite element technique. The governing equation of the multiscale nanocomposite is derived via the variational principle including the geometrical distortion through Green-Lagrange strain. Additionally, the model includes different grading patterns of nanotube through the panel thickness to improve the structural strength. The reliability and accuracy of the developed finite element model are varified by comparison and convergence studies. Finally, the applicability of present developed model was highlight by enlighten several numerical examples for various type shell geometries and design parameters.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.4
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• pp.217-222
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• 2010

Since 1980's, optimum design techniques for ship structural design have been developed to the preliminary design which aims at minimum weight or minimum cost design of mid-ship section based on analytic structural analysis. But the optimum structural design researches about the application for the detail design of local structure based on FEA have been still insufficient. This paper presents optimization technique for the detail design of a racing motor boat. To improve the performance and reduce the damage of a real existing racing boat, direct structural analyses; static and non-linear transient dynamic analyses, were carried out to check the constraints of minimum weight design. As a result, it is shown that the optimum structural design of a racing boat has to be focused on reducing impulse response from pitching motion than static response because the dynamic effect is more dominant. Optimum design algorithm based on nonlinear finite element analysis for a racing motor boat was developed and coded to ANSYS, and its applicability for actual structural design was verifed.

• International Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.19-23
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• 2015

This work deals with the study of buckling and post buckling characteristics of laminated composite plates with and without localized regions of damage. The need of a detailed study on Finite Element Analysis of buckling and post buckling of laminated composite structures considering various aspects enhances the interest among researchers. Mathematical formulation is developed for damaged composite plates using a finite element technique based on Inverse Hyperbolic Shear Deformation Theory. This theory satisfies zero transverse shear stresses conditions at the top and bottom surfaces of the plate and provides a non-linear transverse shear stress distribution. Damage modeling is done using an anisotropic damage formulation, which is based on the concept of stiffness change. The structural elements are subjected to in-plane loading. The computer program is developed in MATLAB environment. The numerical results are presented after through validation of developed finite element code. The effect of damage on buckling and post buckling has been carried out for various parameters such as amount of percentage of damaged area, damage intensity, etc. The results show that the presence of internal flaws will significantly affect the buckling characteristics of laminated composite plates. The outcomes and remarks from this work will assist to address some key issues concerning composite structures.

• Computers and Concrete
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• v.21 no.6
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• pp.607-622
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• 2018

A non-linear finite element model (FEM) was constructed using a three-dimensional software (ATENA-3D) to investigate the effect of strengthening on the behavior of prestressed hollow-core (PHC) slabs with or without openings. The slabs were strengthened using near surface mounted (NSM)-carbon fiber reinforced polymer (CFRP) strips. The constructed model was validated against experimental results that were previously reported by the authors. The validated FEM was then used to conduct an extensive parametric study to examine the influence of prestressing reinforcement ratio, compressive strength of concrete and strengthening reinforcement ratio on the behavior of such slabs. The FEM results showed good agreement with the experimental results where it captured the cracking, yielding, and ultimate loads as well as the mid-span deflection with a reasonable accuracy. Also, an overall enhancement in the structural performance of these slabs was achieved with an increase in prestressing reinforcement ratio, compressive strength of concrete, external reinforcement ratio. The presence of openings with different dimensions along the flexural or shear spans reduced significantly the capacity of the PHC slabs. However, strengthening these slabs with 2 and 4 (64 and $128mm^2$ that represent reinforcement ratios of 0.046 and 0.092%) CFRP strips was successful in restoring the original strength of the slab and enhancing post-cracking stiffness and load carrying capacity.