• Structural Engineering and Mechanics
• /
• 제65권6호
• /
• pp.657-678
• /
• 2018

Sandwich structures are well known for their use in aircraft, naval and automobile industries due to their high strength resistance with light weight and high energy absorption capability. Sandwich beams with soft core are very common and simple structures that are employed in day to day general use appliances. Modeling and analysis of sandwich structures is not straight forward due to the interactions between core and face sheets. In this paper, formulation of Super Convergent finite elements for analysis of the sandwich beams with soft core based on Euler Bernoulli beam theory are presented. Two elements, Eul4d with 4 degrees of freedom assuming rigid core in transverse direction and Eul10d with 10 degrees of freedom assuming the flexible core were developed are presented. The formulation considers the top, bottom face sheets and core as separate entities and are coupled by beam kinematics. The performance of these elements are validated by results available in the published literature. Number of studies are performed using the formulated elements in static, free vibration and wave propagation analysis involving various boundary and loading conditions. The paper highlights the advantages of the elements developed over the traditional elements for modeling of sandwich beams and, in particular wave propagation analysis.

• Structural Engineering and Mechanics
• /
• 제66권3호
• /
• pp.329-341
• /
• 2018

This paper considers the smooth receding contact problem between a homogeneous half-plane and a composite laminate composed of an inhomogeneously coated elastic layer. The inhomogeneity of the elastic modulus of the coating is approximated by an exponential function along the thickness dimension. The three-component structure is pressed together by either a concentrated force or uniform pressures applied at the top surface of the composite laminate. Both semianalytical and finite element analysis are performed to solve for the extent of contact and the contact pressure. In the semianalytical formulation, Fourier integral transformation of governing equations and boundary conditions leads to a singular integral equation of Cauchy-type, which can be numerically integrated by Gauss-Chebyshev quadrature to a desired degree of accuracy. In the finite element modeling, the functionally graded coating is divided into homogeneous sublayers and the shear modulus of each sublayer is assigned at its lower boundary following the predefined exponential variation. In postprocessing, the stresses of any node belonging to sublayer interfaces are averaged over its surrounding elements. The results obtained from the semianalytical analysis are successfully validated against literature results and those of the finite element modeling. Extensive parametric studies suggest the practicability of optimizing the receding contact peak stress and the extent of contact in multilayered structures by the introduction of functionally graded coatings.

• 한국소음진동공학회논문집
• /
• 제24권8호
• /
• pp.583-591
• /
• 2014

The mathematical modeling on the free vibration and stability of a multi-stepped shaft of turbo compressor is performed in this study. The multi-stepped shaft is modeled as a non-uniform Timoshenko beam supported by anisotropic bearings. It is assumed that the shaft is spinning with constant speed about its longitudinal axis and subjected to a conservative axial force induced by front and rear impellers attached to the shaft. The structural model incorporates non-classical features such as transverse shear and rotary inertia. A structural coupling between vertical and lateral motions is induced by Coriolis acceleration terms. The governing equations are derived via Hamilton's variational principle and the equations are transformed to the standard form of an eigenvalue problem. The implications of combined gyroscopic effect, conservative axial force, bearing stiffness and damping are revealed and a number of pertinent conclusions are outlined. In this study analytical results are compared with those from ANSYS finite element analysis and experimental modal testing.

• 한국병원경영학회지
• /
• 제12권2호
• /
• pp.1-24
• /
• 2007

The medical fee reimbursement denied by HIRA(Health Insurance Review Agency) amounted to about 1.2% of the total medical fee claim to HIRA for reimbursement. Most of the denials stem from the inappropriate prescriptions of medical staff violating the medical fee review standards issued by HIRA. Considering the significant impacts of the standards observance behavior on the hospitals' financial viability, we attempted to analyze the predisposition factors of medical staffs' review standards observance behavior. The TPB(Theory of Planned Behavior) was adopted as the theoretical framework of the analysis. Data were collected by administrating a survey on the concepts included in TPB model to the 187 medical staff of a tertiary care hospital. Of the 187 questionaries distributed, 150 were responded resulting 80.2% of response rate. The mean differences among the groups classified by age group, years of experience, medical specialty and gender were analysis using ANOVA. The relationships among the TPB concepts were analysed by applying the Structural Equations Modeling method. The TPB model consists of three exogenous concepts (attitude toward the behavior, subjective norm, and perceived behavioral control) and two endogenous concepts (intention and the behavior). The results of ANOVA indicated significant mean differences among the groups classified by the medical staff's age, years of experience, and medical specialty. The older and the more experienced had the higher mean of observance behavior score. The results of Structural Equations analysis showed that the subjective norm and perceived behavioral control had statistically significant influences on intention, but the influence of attitude to intention was not statistically significant. The influences of perceived behavioral control and intention on behavior were significant. Based on these results the theoretical and practical implications were discussed.

• 한국병원경영학회지
• /
• 제15권2호
• /
• pp.84-106
• /
• 2010

Ensuring the confidentiality of patient records is critical requirement for quality of care and in fulfilling legal obligation of healthcare organizations. This study analyzed the behavior of hospital employees who are dealing with confidential patient information in a hospital. Theory of Planned Behavior(TPB) model and TPB expanded models that add habit concept to TPB are tested for the validity in explaining the predisposing factors that affect the behavior of hospital employee in ensuring the confidentiality of patient records. Data were collected by administrating a survey to the 350 employee of a tertiary care hospital. Of the 350 questionaries distributed, 321 were responded resulting 92% of response rate. The mean differences among the groups classified by age, years of experience, gender, and occupation were analysis using ANOVA. The relationships among the concepts suggested in the models were analysed by applying the Structural Equations Modeling method. The results of ANOVA indicated significant mean differences in the frequency of confidentiality ensuing behavior. Administrative staff and medical technicians show higher frequency of ensuing behavior compared to the physicians and the nurses. And more experienced employee show more confidentiality ensuring behavior. The results of Structural Equations analysis showed that the strong effect of habit and attitude in predicting the behavior. However, the effect of perceived behavioral control was not significant. Based on the results the theoretical and practical implications are discussed.

• 한국건설관리학회논문집
• /
• 제13권3호
• /
• pp.43-55
• /
• 2012

최근 건설 산업에서 이슈가 되고 있는 BIM의 신뢰성을 판단하기 위한 방안으로 BIM 품질 검증 방안이 대두되고 있다. 그러나 현재 BIM 품질 검증은 부재간의 간섭체크, 공간 배치 등 3D Model을 검토하는 것에 국한되어 있으며, 구조, 설비, 견적과 같은 각 분야별 BIM기반 작업 결과물의 검증 방안은 부재한 실정이다. 특히 BIM기반 견적분야에서는 수량 산출의 근거인 산출식이 출력되지 않아 BIM기반 물량산출 결과물을 신뢰하지 못하는 현상이 발생하였다. BIM기반 견적 작업 결과물의 신뢰성을 향상시키기 위해 제조업에서 정의하고 있는 신뢰성 개념을 분석하고, 다년간 BIM기반 물량산출 수행 경험을 토대로 BIM기반 견적 또는 물량산출 작업의 신뢰성에 영향을 미치는 요인을 도출한 결과, 모델링 방법 및 BIM Tool의 특징에 따라 BIM기반 물량 데이터가 달라지는 것을 알 수 있었다. 따라서 본 연구에서는 BIM 기반 견적 모델링 시 모델링 방법에 따른 결과값의 분석과 IFC 파일 교환을 통해 데이터의 신뢰성을 높이는 올바른 모델링 방법 및 데이터 검증 방안을 제시하고자 한다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.275-282
• /
• 2007

In this study, a fluid-structure interaction (FSI) analysis system has been developed in order to evaluate the turbine cascade performance with blade structural deformation effect. Relative movement of the rotor with respect to stator is reflected by modeling independent two computational domains. To consider the deformed position of rotor airfoil, dynamic moving grid method is applied. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation SST $k-{\varepsilon}$ turbulence models are solved to predict unsteady fluid dynamic loads. A fully implicit time marching scheme based on the Newmark direct integration method with high artificial damping is used to compute the fluid-structure interaction problem. Cascade performance evaluations for different elastic axis positions are presented and compared each other. It is importantly shown that the predicted aerodynamic performance considering structural deformation effect of blade can show some deviations compared to the data generally computed from rigid blade configurations and the position of elastic axis also tend to give sensitive effect.

• Structural Engineering and Mechanics
• /
• 제8권6호
• /
• pp.607-622
• /
• 1999

Being a significant mode of deformation, shear effect in addition to the other modes of stretching and bending have been considered to develop two finite element models for the analysis of beams on elastic foundation. The first beam model is developed utilizing the differential-equation approach; in which the complex variables obtained from the solution of the differential equations are used as interpolation functions for the displacement field in this beam element. A single element is sufficient to exactly represent a continuous part of a beam on Winkler foundation for cases involving end-loadings, thus providing a benchmark solution to validate the other model developed. The second beam model is developed utilizing the hybrid-mixed formulation, i.e., Hellinger-Reissner variational principle; in which both displacement and stress fields for the beam as well as the foundation are approxmated separately in order to eliminate the well-known phenomenon of shear locking, as well as the newly-identified problem of "foundation-locking" that can arise in cases involving foundations with extreme rigidities. This latter model is versatile and indented for utilization in general applications; i.e., for thin-thick beams, general loadings, and a wide variation of the underlying foundation rigidity with respect to beam stiffness. A set of numerical examples are given to demonstrate and assess the performance of the developed beam models in practical applications involving shear deformation effect.

• Structural Engineering and Mechanics
• /
• 제12권5호
• /
• pp.527-540
• /
• 2001

A new sort of learning algorithm named whole learning algorithm is proposed to simulate the nonlinear and dynamic behavior of RC members for the estimation of structural integrity. A mathematical technique to solve the multi-objective optimization problem is applied for the learning of the feedforward neural network, which is formulated so as to minimize the Euclidean norm of the error vector defined as the difference between the outputs and the target values for all the learning data sets. The change of the outputs is approximated in the first-order with respect to the amount of weight modification of the network. The governing equation for weight modification to make the error vector null is constituted with the consideration of the approximated outputs for all the learning data sets. The solution is neatly determined by means of the Moore-Penrose generalized inverse after summarization of the governing equation into the linear simultaneous equations with a rectangular matrix of coefficients. The learning efficiency of the proposed algorithm from the viewpoint of computational cost is verified in three types of problems to learn the truth table for exclusive or, the stress-strain relationship described by the Ramberg-Osgood model and the nonlinear and dynamic behavior of RC members observed under an earthquake.

• Structural Engineering and Mechanics
• /
• 제29권1호
• /
• pp.91-111
• /
• 2008

This paper outlines the development of a computational model in order to analyze the dynamic behaviour of coupled fluid-structure systems such as a) liquid containers, b) a set of parallel or radial plates. In this work a hybrid fluid-solid element is developed, capable of simulating both membrane and bending effects of the plate. The structural mass and stiffness matrices are determined using exact integration of governing equations which are derived using a combination of classical plate theory and a finite element approach. The Bernoulli equation and velocity potential function are used to describe the liquid pressure applied on the solid-fluid element. An impermeability condition assures a permanent contact at the fluid-structure interface. Applications of this model are presented for both parallel and radial plates as well as fluid-filled rectangular reservoir. The effect of physical parameters on the dynamic behaviour of a coupled fluid-structure system is investigated. The results obtained using the presented approach for dynamic characteristics such as natural frequency are in agreement to those calculated using other theories and experiments.