• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1179-1183
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• 2007

Electro-Active paper(EAPap) is a new smart material that has a potential to be used in biomimetic actuator and sensor. It is made by cellulose that is abundant material in nature. EAPap is fascinating with its biodegradability, lightweight, large displacement, high mechanical strength and low actuation voltage. Actuating mechanism of EAPap is known to be the combined effects of ion migration and piezoelectricity. However, the electromechanical actuation mechanisms are not yet to be established. This paper presents the modeling of the actuation behavior of water infused cellulose samples and their composite dielectric constants calculated by Maxwell-Wagner theory. Electro-mechanical forces were calculated using Maxwell stress tensor method. Bending deflection was evaluated from simple beam model and compared with experimental observation, and which result in good correlation with each other.

• Nuclear Engineering and Technology
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• 제32권2호
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• pp.180-190
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• 2000

In this study, nonlinear analyses of prestressed concrete(PSC) test beams for inservice inspection of prestressed concrete containments for CANDU nuclear power plants are presented. In the analysis the material nonlinearities of concrete, rebar and prestressing steel are used. To reduce the numerical instability with respect to the used finite element mesh size, the tension stiffening effect has been considered. For concrete, the tensile stress-strain relationship derived from tests is modified and the stress-strain curve of rebar is assumed as a simple bilinear model. The stress-strain curve of prestressing steel is applied as a multilineal curve with the first straight line up to 0.8fpu. To prove the validity of the applied material models, the behavior and strength of the PSC test specimens tested to failure have been evaluated. A reasonable agreement between the experimental results and the predictions is obtained. Parametric studies on the tension stiffening effects, the impact of prestressing losses with time, and the compressive strength of concrete have been conducted.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.901-911
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• 2015

The goal of this study is to investigate computational convergence of optimal solutions, with respect to optimality criteria (OC) method and methods of moving asymptotes (MMA) as optimization model for non-linear programming of material topology optimization using an acceleration method that makes design variables rapidly move toward almost 0 and 1 values. 99 line topology optimization MATLAB code uses loop vectorization and memory pre-allocation as properly exploiting the strengths of MATLAB and moves portions of code out of the optimization loop so that they are only executed once as restructuring the program. Numerical examples of a simple beam under a lateral load and a given material density limitation provide merits and demerits of the present OC and MMA for 99 line topology optimization code of continuous material topology optimization design.

• Steel and Composite Structures
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• 제25권1호
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• pp.67-78
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• 2017

In this study, free vibration of functionally graded (FG) micro/nanobeams based on nonlocal third-order shear deformation theory and under different boundary conditions is investigated by applying the differential quadrature method. Third-order shear deformation theory can consider the both small-scale effects and quadratic variation of shear strain and hence shear stress along the FG nanobeam thickness. The governing equations are obtained by using the Hamilton's principle, based on third-order shear deformation beam theory. The differential quadrature (DQ) method is used to discretize the model and attain the natural frequencies and mode shapes. The properties of FG micro/nanobeam are assumed to be chanfged along the thickness direction based on the simple power law distribution. The effects of various parameters such as the nonlocal parameter, gradient index, boundary conditions and mode number on the vibration characteristics of FG micro/nanobeams are discussed in detail.

• International Journal of Reliability and Applications
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• 제5권2호
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• pp.59-74
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• 2004

There are many uncertain parameters associated with vibration components. Their physical parameters, the machining quality of vibration components, and the applied load acting on them are all uncertain. As a result, the natural frequency and the fatigue limits are also uncertain variables. In this paper, we express these parameters of vibration components and the frequency zone of resonance through interval models; this way, the robust reliability of the vibration components is defined. The robust reliability model measures and assesses the reliability of vibration components. The robust reliability of a cantilever beam is evaluated as an example. The results show that this method is reasonable for robust reliability analysis of vibration components because it does not require a large amount of failure data, it avoids the evaluation of the probability density function, and the computation is simple.

• 자연, 터널 그리고 지하공간
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• 제21권2호
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• pp.117-129
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• 2019

Tunnelling in urban environments is very common nowadays as large cities are expanding and transportation demands require the use of the underground space for creating extra capacity. Inevitably, any such new construction may have significant effects on existing nearby infrastructure and therefore relevant assessment of structural integrity and soil-structure interaction is required. Foundation piles can be rather sensitive to nearby tunnel construction and therefore their response needs to be evaluated carefully. Although detailed three-dimensional continuum finite element analysis can provide a wealth of information about this behaviour of piles, such analyses are generally very computationally demanding and may require a number of material and other model parameters to be properly calibrated. Therefore, relevant simplified approaches are used to provide a practical way for such an assessment. This paper presents a simple method where the pile is modelled with beam finite elements, pile-soil interaction is modelled with soil springs and tunnelling-induced displacements are introduced as an input boundary condition at the end of the soil springs. The performance of this approach is assessed through some examples of applications.

• Advances in nano research
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• 제14권3호
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• pp.285-294
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• 2023

The dynamic and sensing performances of nanomechanical resonators with their different boundary conditions are studied based on surface elasticity-based modeling and simulation. Specifically, the effect of surface stress is included in Euler-Bernoulli beam model for different boundary conditions. It is shown that the surface effect on the intrinsic elastic property of nanowire is independent of boundary conditions, while these boundary conditions affect the frequency behavior of nanowire resonator. The detection sensitivity of nanowire resonator is remarkably found to depend on the boundary conditions such that double-clamping boundary condition results in the higher mass sensitivity of the resonator in comparison with simple-support or cantilever boundary condition. Furthermore, we show that the frequency shift of nanowire resonator due to mass adsorption is determined by its length, whereas the frequency shift is almost independent of its thickness. This study enables a design principle providing an insight into how the dynamic and sensing performances of nanomechanical resonator is determined and tuned.

• 콘크리트학회논문집
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• 제15권5호
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• pp.759-767
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• 2003

This paper presents the simplified but more rational analysis method for the prediction of additional internal forces induced in integral abutment bridges. These internal forces depend upon the degree of restraint provided tc the deck by the backfill soil adjacent to the abutments and piles. In addition, effect of the relative flexural stiffness ratio among pile foundations, abutment, and superstructure on the structural behavior is also an important factor. The first part of the paper develops the stiffness matrices, written in terms of the soil stiffness, for the lateral and rotational restraints provided by the backfill soil adjacent to the abutment. The finite difference analysis is conducted and it is confirmed that the results are agreed well with the predictions obtained by the proposed method. The simplified spring model is used in the parametric study on the behavior of simple span and multi-span continuous integral abutment PSC beam bridges in which the abutment height and the flexural rigidity of piles are varied. These results are compared with those obtained by loading Rankine passive earth pressure according to the conventional method. From the results of parametric study, it was shown that the abutment height, the relative flexural rigidity of superstructure and piles, and the earth pressure induced by temperature change greatly affect the overall structural response of the bridge system. It may be possible to obtain more rational and economical designs for integral abutment bridges by the proposed method.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.4102-4102
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• 2001

In multivariate analysis, absorbance spectrum is measured over a band of wavelengths. One does not often pay attention to the size of this wavelength band. However, it is desirable that spectrum is measured at only necessary wavelengths as long as the acceptable accuracy of prediction can be met. In this paper, the method of selecting an optimal band of wavelengths based on the loading vector analysis was proposed and applied for determining total protein in human serum using near-infrared transmission spectroscopy and PLSR. Loading vectors in the full spectrum PLSR were used as reference in selecting wavelengths, but only the first loading vector was used since it explains the spectrum best. Absorbance spectra of sera from 97 outpatients were measured at 1530∼1850 nm with an interval of 2 nm. Total protein concentrations of sera were ranged from 5.1 to 7.7 g/㎗. Spectra were measured by Cary 5E spectrophotometer (Varian, Australia). Serum in the 5 mm-pathlength cuvette was put in the sample beam and air in the reference beam. Full spectrum PLSR was applied to determine total protein from sera. Next, the wavelength region of 1672∼1754 nm was selected based on the first loading vector analysis. Standard Error of Cross Validation (SECV) of full spectrum (1530∼l850 nm) PLSR and selected wavelength PLSR (1672∼1754 nm) was respectively 0.28 and 0.27 g/㎗. The prediction accuracy between the two bands was equal. Wavelength selection based on loading vector in PLSR seemed to be simple and robust in comparison to other methods based on correlation plot, regression vector and genetic algorithm. As a reference of wavelength selection for PLSR, the loading vector has the advantage over the correlation plot since the former is based on multivariate model whereas the latter, on univariate model. Wavelength selection by the first loading vector analysis requires shorter computation time than that by genetic algorithm and needs not smoothing.

• Earthquakes and Structures
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• 제12권2호
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• pp.165-175
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• 2017

This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full probabilistic analysis methods like MC commonly are very time consuming, the feasibility of simple approximate methods' application including First Order Second Moment (FOSM) method and ASCE41 proposed approach for the soil uncertainty considerations is investigated. By comparing the results of the approximate methods with the results obtained from MC, it's observed that the results of both FOSM and ASCE41 methods are in good agreement with the results of MC simulation technique and they show acceptable accuracy in predicting the response variability.