• Steel and Composite Structures
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• 제24권5호
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• pp.603-613
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• 2017

In this research, the free vibration response of laminated composite plates is investigated using a novel and simple higher order shear deformation plate theory. The model considers a non-linear distribution of the transverse shear strains, and verifies the zero traction boundary conditions on the surfaces of the plate without introducing shear correction coefficient. The developed kinematic uses undetermined integral terms with only four unknowns. Equations of motion are obtained from the Hamilton's principle and the Navier method is used to determine the closed-form solutions of antisymmetric cross-ply and angle-ply laminates. Numerical examples studied using the present formulation is compared with three-dimensional elasticity solutions and those calculated using the first-order and the other higher-order theories. It can be concluded that the present model is not only accurate but also efficient and simple in studying the free vibration response of laminated composite plates.

• Computers and Concrete
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• 제21권1호
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• pp.11-20
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• 2018

The possibilities of non-linear analysis of reinforced-concrete structures are under development. In particular, current research areas include structural analysis with the application of advanced computational and material models. The submitted article aims to evaluate the possibilities of the determination of material properties, involving the tensile strength of concrete, fracture energy and the modulus of elasticity. To evaluate the recommendations for concrete, volume computational models are employed on a comprehensive series of tests. The article particularly deals with the issue of the specific properties of fracture-plastic material models. This information is often unavailable. The determination of material properties is based on the recommendations of Model Code 1990, Model Code 2010 and specialized literature. For numerical modelling, the experiments with the so called "classic" concrete beams executed by Bresler and Scordelis were selected. It is also based on the series of experiments executed by Vecchio. The experiments involve a large number of reinforcement, cross-section and span variants, which subsequently enabled a wider verification and discussion of the usability of the non-linear analysis and constitutive concrete model selected.

• 대한토목학회논문집
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• 제9권3호
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• pp.133-141
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• 1989

과압밀성(過壓密性) 점성토(점성토)의 응력(應力)-변형(變形) 거동(擧動)은 일정한 응력수준(應力水準)에 이르기까지 거의 선형(線形)의 관계를 유지하는 경우가 많다. 본 연구(硏究)에서는, 이러한 지반(地盤)의 응력(應力)-변형(變形) 거동(擧動)을 추정하기 위하여 횡이방성(橫異方性) 탄성론(彈性論)을 도입하고, 이 이론(理論)에 필요한 탄성정수(彈性定數)를 등가매개변수(等價媒介變數)로 대치(代置)하는 새로운 방법(方法) 제안(提安)하였다. 이 방법(方法)은, 등방퇴적면(等方堆積面)과 연직방향(鉛直方向)의 공시체(供試體)로 임의의 두가지 응력경로(應力經路) 배수시험(排水試驗)에 의한 연직변형도(鉛直變形度) 측정만에 의해서도 매개변수(媒介變數)가 결정되는 특징을 가지고 있으며, 이 방법(方法)으로 결정된 등가매개변수(等價媒介變數)를 횡이방성탄성론(橫異方性彈性論)에 적용하여 추정한 응력(應力)-변형(變形) 거동(擧動)을 실험치(實驗値)와 비교(比較)한 결과 대체로 부합된 결과를 얻었다.

• 한국지반공학회논문집
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• 제21권5호
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• pp.25-32
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• 2005

일반적으로 압밀계수는 일차원 압밀이론에 근거한 표준압밀시험을 이용하여 평가된다 하지만 실제 현장에서는 압밀 중 3차원적으로 응력 및 변형이 발생하게 된다. 본 연구에서는 실제 현장에서 발생 가능한 다양한 응력-변형 조건을 고려한 새로운 압밀계수 평가방법을 제안하였다. 제안된 방법에 의한 과잉간극수압 소산양상 예측 결과는 실측치와 매우 잘 일치하였으며, 따라서 본 연구에서 제안된 방법을 이용하는 경우 지반의 압밀 속도를 보다 정확하게 예측할 수 있을 것으로 판단된다.

• Human Ecology Research
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• 제53권3호
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• pp.309-318
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• 2015

This study investigates to investigate the ageing effect on household demand for clothing, food, housing and medical care commodities in Korea using a demand system model. The cross-sectional and time-series data from Statistics Korea on urban household expenditures and age projection analyzed household demands of consumption commodities. The household head age and elderly population ratio were employed for proxy variables of ageing. Ageing variable elasticities of commodity demands were estimated. Study results show that ageing variables significantly influenced on a household demand for commodities; clothing and food consumption decreases; however, housing and medical care consumption increases with ageing. The elasticities of total consumption expenditures and price variables were estimated in the demand analysis; these two variables significantly impacted almost all of the household consumption for the studied commodities. This study provides an opportunity to examine how ageing influences household consumption for clothing, food, housing and medical care commodities as Korean society experiences a rapid ageing. It is also meaningful that this study conducted a quantitative measuring of the household demands for commodities that was different from past research on the household consumption expenditures for commodities.

• Structural Engineering and Mechanics
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• 제10권4호
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• pp.337-357
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• 2000

Analytical formulations and solutions for the first time, to the stability analysis of a simply supported composite and sandwich plates based on a higher order refined theory, developed by the first author and already reported in the literature are presented. The theoretical model presented herein incorporates laminate deformations which account for the effects of transverse shear deformation, transverse normal strain/stress and a nonlinear variation of inplane displacements with respect to the thickness coordinate - thus modelling the warping of transverse cross sections more accurately and eliminating the need for shear correction coefficients. The equations of equilibrium are obtained using the Principle of Minimum Potential Energy (PMPE). The comparison of the results using this higher order refined theory with the available elasticity solutions and the results computed independently using the first order and the other higher order theories developed by other investigators and available in the literature shows that this refined theory predicts the critical buckling load more accurately than all other theories considered in this paper. New results for sandwich laminates are also presented which may serve as a benchmark for future investigations.

• Structural Engineering and Mechanics
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• 제3권1호
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• pp.91-103
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• 1995

An analysis to determine shear centers for anisotropic elastic thin-walled composite beams, cantilevered and loaded transversely at the free end is presented. The shear center is formulated based on familiar strength of material procedures analogous to those for isotropic beams. These procedures call for a balancing of torsional moments on the cross sectional surface and lead to a condition of zero resultant torsional couple. As a consequence, due the presence of anisotropic coupling, certain non-classical effects are manifested and are illustrated in two example problems. The most distinguishing result is that twisting may occur for composite beams even if shear forces are applied at the shear center. The derived shear center locations do not depend on any specific anisotropic bending theories per se, but only on the values of bending and shear stresses which such theories produce.

• Structural Engineering and Mechanics
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• 제40권2호
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• pp.257-277
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• 2011

In this paper the geometrically nonlinear continuum plate finite element model, hitherto not reported in the literature, is developed using the total Lagrange formulation. With the layerwise displacement field of Reddy, nonlinear Green-Lagrange small strain large displacements relations (in the von Karman sense) and linear elastic orthotropic material properties for each lamina, the 3D elasticity equations are reduced to 2D problem and the nonlinear equilibrium integral form is obtained. By performing the linearization on nonlinear integral form and then the discretization on linearized integral form, tangent stiffness matrix is obtained with less manipulation and in more consistent form, compared to the one obtained using laminated element approach. Symmetric tangent stiffness matrixes, together with internal force vector are then utilized in Newton Raphson's method for the numerical solution of nonlinear incremental finite element equilibrium equations. Despite of its complex layer dependent numerical nature, the present model has no shear locking problems, compared to ESL (Equivalent Single Layer) models, or aspect ratio problems, as the 3D finite element may have when analyzing thin plate behavior. The originally coded MATLAB computer program for the finite element solution is used to verify the accuracy of the numerical model, by calculating nonlinear response of plates with different mechanical properties, which are isotropic, orthotropic and anisotropic (cross ply and angle ply), different plate thickness, different boundary conditions and different load direction (unloading/loading). The obtained results are compared with available results from the literature and the linear solutions from the author's previous papers.

• The Journal of Asian Finance, Economics and Business
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• 제8권8호
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• pp.433-442
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• 2021

This research examines the financial performance of Village and Urban Community Funds (VFs). The study also explores the beneficial effects of the biggest microfinance programs in the world in the lower and lowest income provinces; specifically, whether VFs change household economic status or not. The data is collected uniquely from the village funds in four provinces of each region in Thailand which considerably reflect the government achievement. Accordingly, several financial ratios have been applied to evaluate the financial efficiency of the village funds, and the ordered logit model has been used to estimate the impact on economic variables of the poor. The findings show that the village funds do not improve the savings, income, consumption, and asset of VFs' members, although such funds have a higher financial performance. Furthermore, the VFs are a good substitute compared to the Bank for Agriculture and Agricultural Cooperatives (BAAC) credit because the cross-price elasticity of quantity of demand for such loans is positive. In particular, the loans from village funds are insignificantly correlated with the debt, income, asset, and economic status of VF members. This implies that Thai Village Funds do not alleviate definitely the serious problem about the financial situation in rural provinces. Thus, this microfinance does not change the economic well-being of the poor.

• 패션비즈니스
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• 제27권2호
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• pp.52-69
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• 2023

Based on five types of health KF masks currently being commercialized, this study analyzed results of a survey of 316 male and female college students with experience in wearing health masks in Seoul metropolitan area. By identifying problems and improvement requirements according to current status of wearing health masks, results of this study could be used as basic data for designing ergonomic health mask with improved ease of wearing and satisfaction for human safety protection in the future. SPSS 26.0 statistical program was used for all data analyses, including post-hoc test, χ² test for cross-analysis, frequency analysis, independent samples t-test, ANOVA, and Duncan test. Considering that masks are worn for more than 8 hours a day on average, it is necessary to design masks considering materials, sizes of mask ear straps, elasticity and thickness of straps. The design should minimize contact with lips and cheeks with improved fit and comfort, blocking performance, and aesthetics. According to this survey, nearly 50% of respondents said they were willing to wear masks even after the end of COVID-19. Thus, it is necessary to perform research and improve masks to have excellent colors, designs, shapes, fit, and functions suitable for both pandemic and post-pandemic era when wearing masks is common.