• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.973-978
• /
• 2009

In this study, the thermal environment characteristics of On-Off control and thermal difference proportional control method in floor radiant heating system were researched by computer simulation. For the analysis of unsteady heat transfer phenomena in household, the method of using electrical equivalent R-C circuit is applied, and radiation heat transfer between panel, ceiling and walls in household is calculated by enclosure analysis method. The parametric study on two control methods, conventional on-off control and temperature error based time control(T.E.B.T.C.) method, are performed to compare thermal heating control performances, respectively.

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

• 한국수자원학회논문집
• /
• 제50권8호
• /
• pp.551-562
• /
• 2017

2014년부터 기상청에서 현업으로 활용하고 있는 전지구 계절예측시스템 GloSea5의 최대 6개월 예측 강수량을 수자원 및 여러 응용분야에 활용하기 위해서는 예측모델이 가지는 관측자료와의 정량적인 편의를 보정할 필요가 있다. 본 연구에서는 GloSea5의 예측 강수량에서 나타나는 편의를 보정하기 위해 확률분포형을 활용한 편의보정기법, 매개변수 및 비매개변수적 편의보정기법 등 총 11개의 기법을 활용하여 계절예측모델의 적용성을 평가하고 최적의 편의보정기법을 선정하고자 하였다. 과거재현기간에 대한 편의보정 결과, 비매개변수적 편의보정기법이 다른 기법에 비해 가장 관측자료와 유사하게 보정하는 것으로 분석되었으나 예측기간에 대해서는 상대적으로 많은 이상치를 발생시켰다. 이와는 대조적으로 매개변수적 편의보정기법은 과거재현기간 및 예측기간 모두 안정된 결과를 보여주고 있음을 확인할 수 있었다. 본 연구의 결과는 수자원운영 및 관리, 수력, 농업 등 계절예측모델을 활용한 여러 응용분야에 적용이 가능할 것으로 기대된다.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 동계학술발표대회 논문집
• /
• pp.381-386
• /
• 2008

In this study, the energy characteristic of automatic thermostatic valves according to each heating method in floor radiant heating system were researched by computer simulation. For the analysis of unsteady heat transfer phenomena in household, the method of using electrical equivalent R-C circuit is applied, and radiation heat transfer between panel, ceiling and walls in household is calculated by enclosure analysis method. The parametric study on heating method, valve's control method, outdoor air condition, supply heating water temperature, supply flow rate are performed to compare energy characteristic, respectively.

• Geomechanics and Engineering
• /
• 제4권4호
• /
• pp.263-279
• /
• 2012

The present paper deals with the analysis of combined footings resting on geosynthetic reinforced granular fill overlying stone column improved poor soil. An attempt has been made to study the influence of inclusion of geosynthetic layer on the deflection of the footing. The footing has been idealized as a beam having finite flexural rigidity. Granular fill layer has been represented by Pasternak shear layer and stone columns and poor soil have been represented by nonlinear Winkler springs. Nonlinear behavior of granular fill layer, stone columns and the poor soil has been considered by means of hyperbolic stress strain relationships. Governing differential equations for the soil-foundation system have been derived and solution has been obtained employing finite difference scheme by means of iterative Gauss Elimination method. Results of a detailed parametric study have been presented, for a footing supporting typically five columns, in non-dimensional form in respect of deflection with and without geosynthetic inclusion. Geosynthetic layer has been found to significantly reduce the deflection of the footing which has been quantified by means of parametric study.

• Structural Engineering and Mechanics
• /
• 제64권2호
• /
• pp.155-171
• /
• 2017

This paper presents a proposed method for producing reinforced composite concrete columns reinforced with various types of metallic and non metallic mesh reinforcement. The experimental program includes casting and testing of twelve square columns having the dimensions of $100mm{\times}100mm{\times}1000mm$ under concentric compression loadings. The test samples comprise all designation specimens to make comparative study between conventionally reinforced concrete column and concrete columns reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh and tensar mesh. The main variables are the type of innovative reinforcing materials, metallic or non metallic, the number of layers and volume fraction of reinforcement. The main objective is to evaluate the effectiveness of employing the new innovative materials in reinforcing the composite concrete columns. The results of an experimental investigation to examine the effectiveness of these produced columns are reported and discussed including strength, deformation, cracking, and ductility properties. Non-linear finite element analysis; (NLFEA) was carried out to simulate the behavior of the reinforced concrete composite columns. The numerical model could agree the behavior level of the test results. ANSYS-10.0 Software. Also, parametric study is presented to look at the variables that can mainly affect the mechanical behaviors of the model such as the change of column dimensions. The results proved that new reinforced concrete columns can be developed with high strength, crack resistance, and high ductility properties using the innovative composite materials.

• Steel and Composite Structures
• /
• 제19권3호
• /
• pp.615-633
• /
• 2015

Composite steel-concrete beams are used frequently in situations where axial forces are introduced. Some examples include the use in cable-stayed bridges or inclined members in stadia and bridge approach spans. In these situations, the beam may be subjected to any combination of flexure and axial load. However, modern steel and composite construction codes currently do not address the effects of these combined actions. This study presents an analysis of composite beams subjected to combined loadings. An analytical model is developed based on a cross-sectional analysis method using a strategy of successive iterations. Results derived from the model show an excellent agreement with existing experimental results. A parametric study is conducted to investigate the effect of axial load on the flexural strength of composite beams. The parametric study is then extended to a number of section sizes and employs various degrees of shear connection. Design models are proposed for estimating the flexural strength of an axially loaded member with full and partial shear connection.

• 한국철도학회논문집
• /
• 제12권3호
• /
• pp.396-404
• /
• 2009

고속열차의 개발과 함께 구름접촉피로에 의한 레일의 피로균열 및 피로파괴에 대한 연구를 통해 주행안정성을 확보할 수 있는 방안 마련이 필요하다. 따라서 본 연구에서는 Eisenmann의 근사계산식(실용식)을 이용하여 속도, 차륜반경, 궤도지지강성, 침목간격, 축중, 궤도품질에 따른 레일내부 발생응력을 검토하였다. 또한, 유한요소해석을 통해 초기균열의 길이 및 각도, 온도에 따라 레일두부에서 발생하는 전단응력을 검토하여 모드별 응력확대계수를 도출하였다. 이로써 고속철도 레일의 피로수명에 영향을 미치는 주요인자들을 확인하였다.

• 한국해양공학회지
• /
• 제32권5호
• /
• pp.333-340
• /
• 2018

This paper addresses the concept of the representative mean position, which was devised to improve the numerical efficiency of a time domain fatigue analysis of a mooring chain. To investigate the influence of an artificial offset of the floater on the fatigue of the mooring chain, a parametric study was performed on the moored FPSO under various combinations of offsets and environmental conditions. Tension time histories were calculated using the de-coupled analysis method, and fatigue damages were calculated to determine the influence of the offset. The parametric study was extended to a more realistic case to determine the actual effect of the representative mean position, where a comparison was made between the two different analysis results, one using the representative mean position and the other one using the actual mean position. It was confirmed that the application of the representative mean position guaranteed the conservatism of the fatigue damage with the enhanced numerical efficiency in the time domain fatigue analysis.

• Nuclear Engineering and Technology
• /
• 제52권5호
• /
• pp.1079-1092
• /
• 2020

A parametric study of several parameters relevant to design safety on the spent nuclear fuel (SNF) rod response under a drop accident is presented. In the view of the complexity of interactions between the independent safety-related parameters, a factorial design of experiment is employed as an efficient method to investigate the main effects and the interactions between them. A detailed single full-length fuel rod is used with consideration of post-irradiated fuel conditions under horizontal and vertical free-drops onto an unyielding surface using finite-element analysis. Critical drop heights and critical g-loads that yield the threshold plastic strain in the cladding are numerically estimated to evaluate the fuel rod structural resistance to impact load. The combinatory effects of four uncertain parameters (pellet-cladding interfacial bonding, material properties, spacer grid stiffness, rod internal pressure) and the interactions between them on the fuel rod response are investigated. The principal finding of this research showed that the effects of above-mentioned parameters on the load-carrying capacity of fuel rod are significantly different. This study could help to prioritize the importance of data in managing and studying the structural integrity of the SNF.