• 콘크리트학회논문집
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• 제11권3호
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• pp.59-67
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• 1999

The mass concrete structures are generally constructed in an incremental manner by deviding the whole structures by a series of many blocks. The temperature and stress distributions of any specific block are continuously affected by the blocks placed before and after the specific block. For an accurate analysis of mass concrete structures, the sequence of all the blocks must be accordingly considered including the change of material properties with time for those blocks considered. The purpose of this study is to propose a realistic analysis method which can take into account not only the influence of the sequence, time interval and size of concrete block placement on the temperatures and stresses, but also the change of material properties with time. It is seen from this study that the conventional simplified analysis, which neglects material property changes of some blocks with time and does not consider the effect of adjacent blocks in the analysis, may yield large discrepancies in the temperature and stress distributions of mass concrete structures. This study gives a method to choose the minimum number of blocks required to obtain reasonably accurate results in analysis. The study provides a realistic method which can determine the appropriate size and time interval of block placement, and can be efficiently used in the design and construction of mass concrete structures.

• Computers and Concrete
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• 제3권1호
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• pp.17-28
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• 2006

Replacement of actual stress distribution in a reinforced concrete (RC) flexural member with a simpler geometrical shape, which maintains magnitude and location of the resultant compressive force, is an acceptable conceptual trick. This concept was originally perfected for normal strength concrete. In recent years, high strength concrete (HSC) has been introduced and widely used in modern construction. The stress block parameters require updating to account for special features of HSC in the design of flexural members. In future, more varieties of concrete may be developed and a corresponding design procedure of RC flexural members will be required. The usual practice is to conduct large number of experiments on various sizes of specimen and then evolve an empirical relation. This paper presents a numerical procedure through which the stress block parameters can be numerically derived for a given strain ratio variation. The material model for concrete is presented and computational procedure is described. This procedure is illustrated with several variations of strain ratio. The advantages of numerical procedure are that it costs less and it can be used with new material models for any new variety of concrete.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.800-808
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• 1998

In this study the thermal stress distribution and deformantion characteristics resulting from the nonuniform temperature fields of the cylinder block of a light 3-cylinder 4-stroke gasoline engine were analyzed using the 3-dimensional finite element method. The temperature distributions req-uisite for the thermoelastic behavior alalysis were obtained from the steady-state heat conduction analysis performed on the basis of experimental data. in order to examine the effect of a ceramic material the cylinder liner was replaced by the silicon nitride($Si_{3}N_{4}$) and its thermal behaviors were compared with those of the original block.

• 콘크리트학회지
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• 제11권1호
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• pp.149-160
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• 1999

본 논문은 고강도 콘크리트기둥에 대한 설계방법을 검증하는 연구의 일부로서, 보통강도 및 고강도 콘크리트기둥시편에 대하여 편심하중의 재하실험을 수행하여 파괴거동을 관찰하고 기둥강도를 측정하였다. 기둥시편은 모두 32개로 콘크리트 압축강도, 종방향 철근비, 세장비, 재하편심을 실험의 주요변수로 선정하였다. 콘크리트 압축강도는 356~951 kg/$cm^$ 이며, 종방향철근비는 1.13~5.51 %, 세장비는 19, 40, 61의 3 종류로 하였다. ACI의 직사각형 응력블럭, Ibrahim과 MacGregor의 수정된 직사각형 응력블럭, 사다리꼴 응력 블럭을 이용한 기둥강도해석과 축력-모멘트-곡률해석을 통한 기둥강도해석을 수행하였으며, 실험결과와 비교분석하였다. 현시방서에서 적용하고 있는 직사각형 응력블럭은 철근비가 낮은 고강도 콘크리트기둥에 대하여 비안전측의 축력-모멘트강도를 제공한다. 축력-모멘트-곡률해석을 통한 기둥강도해석시에는 콘크리트 응력-변형률곡선의 최대응력을 결정하는 $k_3$ 값에 따라 정확성 및 안전성이 좌우된다. 또한, 본 논문에서는 재하실험을 통한 기둥의 파괴거동, 압축연단 극한변형률, 응력블럭변수 등을 비교분석하였다.

• 오토저널
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• 제15권3호
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• pp.55-67
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• 1993

In this study, the thermal behavior characteristics of the cylinder block of a small 3-cylinder, 4-stroke gasoline engine were analyzed, using the 3-dimensional finite element method. Before numerical analyses were conducted, the performance test and the heat transfer experiment of the engine were carried out in order to prepare the input data for the computations. Engine cycle simulation was performed to obtain the heat transfer coefficient and the temperature of the gas and the mean heat transfer coefficient of coolant. Temperature fields as a result of steady-state heat transfer were obtained and compared with experimental results measured at specific points of the inner and the outer walls of the cylinder block. The thermal stress and deformation characteristics resulting from the nonuniform temperature distributions of the block were investigated. The effects of the thermal behaviors of the cylinder block on the engine operations and the unfavourable aspects of excessive thermal loading were examined on the basis of the calculated results.

• 한국기계가공학회지
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• 제17권1호
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• pp.69-75
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• 2018

This study aims to provide ways to achieve structural improvements of the internal flow path of the discharge plenum of a swash plate piston pump valve block vulnerable to cracks. This paper corresponds to Part I, which consists of a structural analysis of the valve block, identification of the stress distribution and stress raisers, and creation of a Simple Model of the valve block to review the optimal design. Structural analysis was performed by assigning the same conditions as those found in the valve block model, and the design was reviewed by examining three different design improvement plans for the internal flow path of the discharge plenum.

• 한국안전학회지
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• 제21권2호
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• pp.80-88
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• 2006

In the present study damage behavior of resilient sleepers on concrete ballasts is analyzed. Cracks of resilient sleepers in a railway track system are concentrated on inside of blocks to which the tie bars are connected. Finite element analysis is performed by dividing a block into the straight section and the curved section according to the load condition of the resilient sleeper, and limited the interpretation within the range of resilience. In addition, the value of stress obtained from the interpretation was compared with the allowable stress of concrete to determine the safety. According to the result of numerical analysis, compared with the stress before unequal settlement, the tensile stress of the inside of the block increased significantly after the settlement considering the entire block, and the tensile stress of this part exceeded the allowable stress of concrete, so was undesirable in terms of safety. In reality, the arrangement of tensile stiffeners inside blocks connected to tie bars is improper in the design of resilient sleepers, and when unequal settlement occurs, tensile stress increases on this part and consequently causes cracking damage. It is necessary to arrange wire meshes or tensile reinforcing bars in a structurally safe way to reinforce the inside of blocks on which cracks are concentrated.

• Computers and Concrete
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• 제11권5호
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• pp.383-397
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• 2013

Two-dimensional tensile stresses are occurring at the back of the anchorage of the tendons of prestressed concrete bridges. A new method named "tensile stress region" for the design of the reinforcement is presented in this paper. The basic idea of this approach is the division of an anchor block into several slices, which are described by the tensile stress region. The orthogonal reinforcing wire mesh can be designed in each slice to resist the tensile stresses. Additionally the sum of the depth of every slice defined by the tensile stress region is used to control the required length of the longitudinal reinforcement bars. An example for the reinforcement design of an anchorage block of an external prestressed concrete bridge is analyzed by means of the new presented method and a finite element model is established to compare the results. Furthermore the influence of the transverse and vertical prestressing on the ordinary reinforcement design is taken into account. The results show that the amount of reinforcement bars at the anchorage block is influenced by the layout of the transverse and the vertical prestressing tendons. Using the "tensile stress region" method, the ordinary reinforcement bars can be designed more precisely compared to the design codes, and arranged according to the stress state in every slice.

• 한국철도학회논문집
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• 제5권3호
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• pp.167-173
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• 2002

The influence of thermal stress at tread breaking in Korean High Speed Train wheel was investigated using the coupled thermal-mechanical analysis technique. The mechanical load or wheel-rail contract load and braking load were considered during FEM analysis. During the stop braking, the effect of mechanical stress on the combined stress is relatively larger than that of thermal stress in the rim of wheel. However, the effect of thermal stress is relatively larger than that of mechanical stress in the plate of wheel. When 300% of the block force was applied, the maximum von Mises stress of 61.0 MPa was found at the outside plate around 400 mm far away from the wheel center.

• 터널과지하공간
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• 제29권1호
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• pp.64-74
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• 2019

지하공동의 굴착 과정에서 암반 절리로 인해 생성되는 암석블록의 거동 여부는 지하공동의 역학적 안정성에 있어서 중요한 요소이다. 본 연구에서는 대심도 지하공동 조건 하에서 지체응력 및 절리물성 조건에 따른 암석블록의 거동 안정성을 정량적으로 분석하였다. 이론적으로 계산된 암석블록의 거동조건과 3DEC 수치해석을 통해 분석된 암석블록의 거동양상을 비교하여, 이론값과 수치해석 결과간의 오차를 지체응력 및 절리물성 조건에 따라 분석하였다. 암석블록의 거동 안정성 분석을 수행한 결과는 수치해석 결과와 비교할 때 약 5% 이하의 오차를 보여 본 연구에서 제시한 이론적 방법론의 적용가능성을 검증하였다.