• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.151-160
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• 2004

In the present study, Loop scheme is applied to generate smooth surfaces. To be consistent with the limit points of target surface, the initial sampling points are properly rearranged. The pointwise errors of curvature and position in the sequence of subdivision process are evaluated in the Loop subdivision scheme. A first-order shear deformable Loop subdivision triangular element which can handle transverse shear deformation of moderately thick shell are developed. The developed element is more general than the previous one based on classical shell theory, since the new one includes the effect of transverse shear deformation and has standard six degrees of freedom per node. The quartic box spline function is used as interpolation basis function. Numerical examples for the benchmark static shell problems are analyzed to assess the performance of the developed subdivision shell element and locking trouble.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.331-340
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• 2010

The basic theory and application of new adaptive finite element algorithm have been proposed in this study including the adaptive hp-refinement strategy, and the effective method for constructing hp-approximation. The hp-adaptive finite element concept needs the integrals of Legendre shape function, nonuniform p-distribution, and suitable constraint of continuity in conjunction with irregular node connection. The continuity of hp-adaptive mesh is an important problem at the common boundary of element interface. To solve this problem, the constraint of continuity has been enforced at the common boundary using the connectivity mapping matrix. The effective method for constructing of the proposed algorithm has been developed by using hierarchical nature of the integrals of Legendre shape function. To verify the proposed algorithm, the problem of simple cantilever beam has been solved by the conventional h-refinement and p-refinement as well as the proposed hp-refinement. The result obtained by hp-refinement approach shows more rapid convergence rate than those by h-refinement and p-refinement schemes. It it noted that the proposed algorithm may be implemented efficiently in practice.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.731-740
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• 2011

Provisions for the redistribution of negative moments in KCI 2007 and ACI 318-08 use a method for continuous flexural members subjected to uniformly-distributed gravity load. Moment redistributions and plastic rotations in beams of reinforced concrete moment frames subjected to lateral load differ from those in continuous flexural members due to gravity load. In the present study, a quantitative relationship between the moment redistribution and plastic rotation is established for beams subjected to both lateral and gravity loads. Based on the relationship, a design method for the redistribution of negative moments is proposed based on a plastic rotation capacity. The percentage change in negative moments in the beam was defined as a function of the tensile strain of re-bars at the section of maximum negative moment, which is determined by a section analysis at an ultimate state using KCI 2007 and ACI 318-08. Span, reinforcement ratio, cracked section stiffness, and strain-hardening behavior substantially affected the moment redistribution. Design guidelines and examples for the redistribution of the factored negative moments determined by elastic theory for beams under lateral load are presented.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.5 no.1
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• pp.22-28
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• 2002

A New concept for the LNG-FPSO ship, with moonpool and bilge step in bottom, is proposed. This concept is investigated with regard to motion reduction and sloshing phenomena of the cargo and operation tanks. The principal dimensions of the ship are $L\timesb B\times D\times t(design)=270.0\times51.0\times32.32\times13.7(m)$, with a total cargo capacity of 161KT; a 98% loading condition is considered for this study. The moonpools and rectangular step at the bilge have been designed for the purpose of decreasing the motion within the tank. For the motion analysis, linearized three-dimensional diffraction theory, with the simplified boundary condition was used. The six-degree of freedom coupled motion responses were calculated for the LNG-FPSO ship. Viscous effects on the roll motion responses of a vessel were taken into account in this calculation program, using an empirical formula suggested by Himeno(1981). The case study for the moonpool size has been conducted using theoretical estimation and the experimental method. For the optimization of the moonpool size and effect of the bilge step, 9 cases of its size, both with and without bilge step, were involved in the study. no motion responses, especially roll motion, for the designed LNG-FPSO ships are much lower than those of other drill ships and shuttle tankers. The limit criterions are satisfied. To check the cargo tank and operation tank sizes, we performed a sloshing analysis in the irregular waves which focuses on the pressure distribution on the tank wall and the time history of pressure and free surface for No.2 and 5 tanks of LNG-FPSO with chamfers. Finally, optimum tank sire was estimated.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.225-228
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• 2008

This paper presents out-of-plane shear strength models for composite wall with steel plates based on limit theorem in the framework of the plasticity theory. The formulas proposed by JEAG 4618 need to be reconsidered with a couple of limitations; ignoring the effect of bond stress generated by studs in the process of calculating arch action, illogically discriminating between concrete shear cracking strength and arch strength by algebraic relation in short shear span ratio(0-2.0). In most cases, reinforcement ratio is not sufficient to yield, as a result, arch strength is determined by accounting equilibrium including both bond strength and concrete compressive strength. We conducted experimental research assuming that SC wall is a continuous beam under the simplified loading patterns, changing main valuables involving the number of studs, stirrups. The results show good agreements with the formula and we quoted the test results of JEAG.

• Geomechanics and Engineering
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• v.5 no.4
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• pp.363-377
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• 2013

Any structure constructed on the earth is supported by the underlying soil. Foundation is an interfacing element between superstructure and the underlying soil that transmits the loads supported by the foundation including its self weight. Foundation design requires evaluation of safe bearing capacity along with both immediate and long term settlements. Weak and compressible soils are subjected to problems related to bearing capacity and settlement. The conventional method of design of footing requires sufficient safety against failure and the settlement must be kept within the allowable limit. These requirements are dependent on the bearing capacity of soil. Thus, the estimation of load carrying capacity of footing is the most important step in the design of foundation. A number of theoretical approaches, in-situ tests and laboratory model tests are available to find out the bearing capacity of footings. The reliability of any theory can be demonstrated by comparing it with the experimental results. Results from laboratory model tests on square footings resting on sand are presented in this paper. The variation of bearing capacity of sand below a model plate footing of square shape with variation in size, depth and the effect of permissible settlement are evaluated. A steel tank of size $900mm{\times}1200mm{\times}1000mm$ is used for conducting model tests. Bearing capacity factor $N_{\gamma}$ is evaluated and is compared with Terzaghi, Meyerhof, Hansen and Vesic's $N_{\gamma}$ values. From the experimental investigations it is found that, as the depth of sand cushion below the footing ($D_{sc}$) increases, ultimate bearing capacity and settlement values show an increasing trend up to a certain depth of sand cushion.

• Water for future
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• v.27 no.3
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• pp.45-54
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• 1994

Basic theory of fractal dimension is introduced and performed for the generated time series using the water balance model. The water balance equation over a large area is analyzed at seasonal time scales. In the generation and modification of mesoscale circulation local recycling of precipitation and dynamic effects of soil moisture are explicitly included. Time delay is incorporated in the analysis. Depending on the parameter values, the system showed different senarios in the evolution such as fixed point, limit cycle, and chaotic types of behavior. The stochastic behavior of the generated time series is due to deterministic chaos which arises from a nonlinear dynamic system with a limited number of equations whose trajectories are highly sensitive to initial conditions. The presence of noise arose from the characterization of the incoming precipitation, destroys the organized structure of the attractor. The existence of the attractor although noise is present is very important to the short-term prediction of the evolution. The implications of this nonlinear dynamics are important for the interpretation and modeling of hydrologic records and phenomena.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.9
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• pp.1040-1049
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• 1992

When the model of control object is not described correctly, ambiguity is often expressed by unknown parameter, In a case that this ambiguity satisfies a certain condition of limit, if robust control method is used, even if model is not correctly discribed, control system can be composed. The characteristic of control based on the variable structure theory is that the influence by ambiguity of system eradicates high-gain feedback. Therefore in this paper, VSS indentifier is proposed. Transformation of control input producing control system in sliding mode actually reflects influence of ambiguity unknown parameter of control object. If useful information is out from transformation input by a few times of operation, proper identify mechanism is selected and this information is used, to decide the unknown parameter is possible. So more effective controller was composed by addition of the proposed identifier to the unknown parameter identifier of robot manipulator.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.853-858
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• 2007

In this paper, a seesaw system composed with a moving cart on the rail and seesaw frame is made to demonstrate the effectiveness of the control theory. The control aim is to maintain an equilibrium of seesaw frame in spite of various initial conditions and an allowable disturbance. To solve this control problem, a PI-type state feedback controller using reduced-order observer is implemented and applied to the seesaw system. The reduced-order observer can be used to estimate the state variables in the case of the limit of sensor number or the constraint on setting sensors and the cost. A series of simulation are carried out to verify the effectiveness of the control system.

• Journal of the Korean Society for Library and Information Science
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• v.8
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• pp.73-101
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• 1981

Retrieval effectiveness is the principal criterion for measuring the performance of an information retrieval system. The effectiveness of a retrieval system depends primarily on the extent to which it can retrieve wanted documents without retrieving unwanted ones. So, ultimately, effectiveness is a function of the relevant and nonrelevant documents retrieved. Consequently, 'relevance' of information to the user's request has become one of the most fundamental concept encountered in the theory of information retrieval. Although there is at present no consensus as to how this notion should be defined, relevance has been widely used as a meaningful quantity and an adequate criterion for measures of the evaluation of retrieval effectiveness. The recall and precision among various parameters based on the 'two-by-two' table (or, contingency table) were major considerations in this paper, because it is assumed that recall and precision are sufficient for the measurement of effectiveness. Accordingly, different concepts of 'relevance' and 'pertinence' of documents to user requests and their proper usages were investigated even though the two terms have unfortunately been used rather loosely in the literature. In addition, a number of variables affecting the recall and precision values were discussed. Some conclusions derived from this study are as follows: Any notion of retrieval effectiveness is based on 'relevance' which itself is extremely difficult to define. Recall and precision are valuable concepts in the study of any information retrieval system. They are, however, not the only criteria by which a system may be judged. The recall-precision curve represents the average performance of any given system, and this may vary quite considerably in particular situations. Therefore, it is possible to some extent to vary the indexing policy, the indexing policy, the indexing language, or the search methodology to improve the performance of the system in terms of recall and precision. The 'inverse relationship' between average recall and precision could be accepted as the 'fundamental law of retrieval', and it should certainly be used as an aid to evaluation. Finally, there is a limit to the performance(in terms of effectiveness) achievable by an information retrieval system. That is : "Perfect retrieval is impossible."