• Computational Structural Engineering
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• v.10 no.1
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• pp.159-171
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• 1997

This study investigates the stress distribution in a transversely isotropic medium containing a spheroidal cavity where the medium is under uniaxial tension in z-direction in one case and pure shear in the plane of isotropy in another case. The technical approach used in this study combines exact analytical and numerical methods. The exact analytical method is based upon three potential functions taken in terms of the Legendre associated functions of the first and second kind. The numerical method is based upon the finite difference approach. Numerical results concerning the two loading conditions with five anisotropic materials are presented.

• Structural Engineering and Mechanics
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• v.20 no.2
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• pp.209-223
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• 2005

A new method for deriving analytical solution of the annular elastic plate on elastic foundation under axisymmetric loading is presented. The formulation is based on application of Hankel integral transforms and Bessel functions' properties in the corresponding boundary-value problem. A representative example is studied and the obtained solution is compared with published numerical results indicating excellent agreement.

• Journal of Korea Port Economic Association
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• v.19 no.2
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• pp.55-67
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• 2003

The purpose of this study is to estimate and forecast the marine trading volumes based on the structural model. We employ GPH cointegration test since the structural model must be stationary to get the accurate predicted values. The empirical results show that our model is stationary. This paper also applies variance decompositions and impulse-response functions to the structural model composed of exchange rate, domestic industrial activity, and world business. The results indicate that while both loading and unloading volumes respond positively to the shocks in income and then decay very slowly, their responses are different to the shocks in exchange tate.

• Journal of the Korean Wood Science and Technology
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• v.34 no.5
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• pp.19-28
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• 2006

There has been considerable research in recent times in light-timber med structures in fires. These structures have included horizontal (floor-like) panels in bending and walls under eccentric and approximately concentric vertical loading. It has been shown that compression properties are the most dominant mechanical properties in affecting structural response of these structures in fire. Compression properties have been obtained by various means as functions of one variable only, temperature. It has always been expected that compression properties would be significantly affected by moisture and stress, as well. However, these variables have been largely ignored to simplify the complex problem of predicting the response of light-timber framed structures in fire. Full-scale experiments on both the panels and walls have demonstrated the high level of significance of moisture and stress for a limited range of conditions. Described in this paper is an overview of these conditions and experiments undertaken to obtain compression properties as a functions of moisture, stress and temperature. The experiments limited temperatures to $20{\sim}100^{\circ}C$. At higher temperatures moisture vaporizes and moisture and stress are less significant. Described also is a creep model for wood at high temperatures.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.6
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• pp.577-588
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• 2016

Due to the uncertainties related to the flaw assessment parameters, such as flaw size, fracture toughness, loading spectrum and so on, the probability concept is preferred over deterministic one in flaw assessment. In this study, efforts have been made to develop the reliability based flaw assessment procedure which combines the flaw assessment procedure of BS7910 and first-and second-order reliability methods (FORM/SORM). Both crack length and depth of semi-elliptical surface crack at weld toe were handled as random variable whose probability distribution was defined as Gaussian with certain means and standard deviations. Then the limit state functions from static rupture and fatigue perspective were estimated using FORM and SORM in joint probability space of crack depth and length. The validity of predicted limit state functions were checked by comparing it with those obtained by Monte Carlo simulation. It was confirmed that the developed methodology worked perfectly in predicting the limit state functions without time-consuming Monte Carlo simulation.

• Journal of the Korea society of information convergence
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• v.7 no.2
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• pp.49-57
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• 2014

Recently, opinion mining is introduced to extract useful information from SNS data and to evaluate the true intention of users. Opinion mining are required several efficient techniques to collect and analyze a large amount of SNS data and extract meaningful data from them. Therefore in this paper, we propose a parallel HDFS(Hadoop Distributed File System) and emotion functions based on Mapreduce to extract some emotional information of users from various unstructured big data on social networks. The experiment results have verified that the proposed system and functions perform faster than O(n) for data gathering time and loading time, and maintain stable load balancing for memory and CPU resources.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.199-212
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• 2020

A large percentage of maritime accidents in coastal seas are related to small fishing vessels. In order to investigate causes of maritime accidents, it is often necessary to carry out dynamic simulations for the estimation of trajectories and motions of vessels. Initial conditions of vessels such as main dimensions, loading conditions and hydrostatic properties are required for the accurate simulations. Small fishing vessels usually have few records of hydrostatic properties during their fishing operations. Therefore, in this study, estimation procedures for hydrostatic properties of small fishing vessels are proposed. At first, hull form characteristics of Korean small fishing vessels are investigated. Most of vessels have hard-chines and centerline skegs, they have similar hull forms. Bonjean curves of several small fishing vessels whose gross tonnages are below 10 tons are normalized with vessel breadths and depths. Representative bonjean curves are derived from normalized bonjean curves, and a representative hull plan is obtained as well. If the vessel loading conditions such as total weights and centers of gravity are given, fore and aft drafts can be calculated by using the representative bonjean curves with the constraint that weights and buoyancies are in equilibrium. Metacentric heights are also estimated by using the representative hull plan. Drafts and metacentric heights estimated by proposed iterative estimation procedures are compared with actual vessel data, estimated values are in good agreements with actual values. In addition, normalized fore and aft drafts, metacentric heights of vessels can be formulated as the linear functions of normalized total weights and centers of gravity. Empirical formulas of drafts and metacentric heights are proposed, and it is confirmed that the empirical formulas also provide reasonable results, which are similar to the results by iterative estimation procedures with representative bonjean curves and hull plan.

• Geomechanics and Engineering
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• v.20 no.1
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• pp.1-7
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• 2020

In structures excavated in rock mass, load progressively increases to a level and remains constant during the construction. Rocks display different elastic properties such as E_i and ʋ under different loading conditions and this requires to use the true values of elastic properties for the design of safe structures in rock. Also, rocks will undergo horizontal and vertical deformations depending on the amount of load applied. However, under constant loads, values of E_i and ʋ will vary in time and induce variations in the behavior of the rock mass. In some empirical equations in which deformation modulus of the rock mass is taken into consideration, elastic parameters of intact rock become functions in the equation. Hence, the use of time dependent elastic properties determined under constant loading will yield more reliable results than when only constant elastic properties are used. As well known, rock material will play an important role in the deformation mechanism since the discontinuities will be closed due to the load. In this study, E_i and ʋ values of intact rocks were investigated under different constant loads for certain rocks with high deformation capabilities. The results indicated significant time dependent variations in elastic properties under constant loading conditions. E_i value obtained from deformability test was found to be higher than the E_i value obtained from the constant loading test. This implies that when static values of elastic properties are used, the material is defined as more elastic than the rock material itself. In fact, E_i and ʋ values embedded in empirical equations are not static. Hence, this workattempts to emerge a new understanding in designing of safer structures in rock mass by numerical methods. The use of time-dependent values of E_i and ʋ under different constant loads will yield more accurate results in numerical modeling analysis.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.1
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• pp.1-8
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• 2013

The finite element analysis (FEA) is a numerical technique to find solutions of field problems. A field problem is approximated by differential equations or integral expressions. In a finite element, the field quantity is allowed to have a simple spatial variation in terms of linear or polynomial functions. This paper represents a review and an accuracy-study of the finite element method comparing the FEA results with the exact solution. The exact solutions were calculated by solid mechanics and FEA using matrix stiffness method. For this study, simple bar and cantilever models were considered to evaluate four types of basic elements - constant strain triangle (CST), linear strain triangle (LST), bi-linear-rectangle(Q4),and quadratic-rectangle(Q8). The bar model was subjected to uniaxial loading whereas in case of the cantilever model moment loading was used. In the uniaxial loading case, all basic element results of the displacement and stress in x-direction agreed well with the exact solutions. In the moment loading case, the displacement in y-direction using LST and Q8 elements were acceptable compared to the exact solution, but CST and Q4 elements had to be improved by the mesh refinement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.143-153
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• 2006

In design of bridges, estimation of actions and loadings is very important for the safety and maintenance of bridges. In general, effect of traffic loading on the bridge can be modeled as live load (including impact load) and fatigue load. For estimation of traffic loading, it is important to get reliable and comprehensive truck statistical data such as the traffic and weight information. To get statistical data, Bridge Weigh-In-Motion (BWIM), which measures the truck weights without stopping the traffic, is need to be developed. In this study, BWIM system with various functions is developed first. Then this system is used to get comprehensive truck data. Traffic loadings including fatigue and live loading are formulated from the truck data acquired from the bridges. Objectives of this study are to develop the BWIM system, to apply the system in test bridge in Highway, and to formulate the live and fatigue loading for bridge design.