• 한국해양공학회지
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• 제21권5호
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• pp.25-32
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• 2007

The piled-raft foundation, a new design concept, is one of the most effective kinds of foundation for reducing settlement of structures. An alternative piled-raft system with disconnection cap and a sand cushion between the pile and raft was also investigated to compare the influence of ultimate bearing capacity and settlement. Load-settlement relation curves were used to evaluate the ultimate bearing capacity. In the numerical analyses, a plane strain elasto-plastic finite element model (Mohr-Coulomb model) was used to present the response of the piled-raft foundation.

• 동력기계공학회지
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• 제5권2호
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• pp.57-62
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• 2001

Gas turbine performance is highly dependent on the engine performance which is closely related to the engine materials since they are exposed to severe working environments, i.e, high temperature and high stresses. For this reason, advanced materials with improved properties are required for the engine. The purpose of this research is to develop key materials technologies for aircraft industry and to tester domestic production of related parts. In this paper, the real-time prediction of high temperature creep strength and creep life for nickel-based superalloy Udimet 720(high-temperature and high-pressure the gas turbine engine materials) was performed on round-bar type specimens under pure load at the temperatures of 538, 649 and $704^{\circ}C$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.763-768
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• 2000

The purpose of this paper is to predict the flexural strengthening of reinforced concrete beams by the external bonding of carbon fiber reinforced plate(CFRP) to the tension face of the beam. Used computational equation is derived by relation of stress an strain. This equation is applied to four-nondamage beam and tow-preloading beam. Six scale beams were tested to evaluate the strength enhancement provided by the CFRP. And describes the strength enhancement provided to the flexural capacity of reinforced concrete beam by the external bonding of CFRP. An inelastic section analysis procedure was developed that accurately predicts the load displacement response of the retrofitted beams.

• 한국지진공학회논문집
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• 제24권4호
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• pp.189-196
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• 2020

In this study, two full-scale gravity load-designed reinforced concrete corner beam-column joints were tested by being subjected to uniand bi-directional cyclic lateral loading. The test variable was loading type: uni- or bi-directional loading. To investigate the effect of the loading type on the cyclic behavior of joint specimens, damage progression, force-deformation relation, contribution of joint deformation to total drift, joint stress-strain response, and cumulative energy dissipation were investigated. The test data suggest that bidirectional loading can amplify damage accumulation in the joint region.

• Geomechanics and Engineering
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• 제21권1호
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• pp.53-62
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• 2020

Rheological processes in the rock mass for the stress-strain analysis are quite important when considering the construction of underground structures in soft rock masses, particularly in case of construction in several stages. In the analysis, it can be assumed that the reinforced concrete structure is slightly deformable in relation to the rock mass, and the rheological stress redistribution happens at the expense of the elements of rock mass. The basic elements of rheological models for certain types of rock mass and analysis of these models are presented in the first part of this paper. The second part is dedicated to the analysis of rheological processes in marl rock mass and the influence of these processes on the reinforced-concrete tunnel structure.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권2호
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• pp.132-140
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• 2012

This study aims to assess fatigue property by the static overload and average load in the fillet welded joints which is on the ship structural steel having gusset welds. To this end, a small specimen was made, to which the same welding condition for the actual ship structure was applied, to perform fatigue tests. In this study, a method to simply assess changes in welding residual stress according to different static overload was suggested. By measuring actual strain at the weld toe, the weld stress concentration factor and property which is determined by recrystallization in the process of welding were estimated to investigate the relation between overload and fatigue strength.

• Advances in Computational Design
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• 제8권1호
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• pp.77-96
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• 2023

Calculating size-dependent mechanical properties of the nano-scale materials usually involves cumbersome numerical and theoretical works. In this paper, we aim to present a closed-form relation to calculate the length-dependent Young's modulus of carbon nanotubes (CNTs) based on nonlocal elasticity theory. In this regard, a single wall carbon nanotube (SWCNT) is considered as a rod structure and the governing nonlocal equations are developed under uniaxial tensile load. The equations are solved using analytical methods and strain distribution, total displacement and the size-dependent equivalent Young's modulus are obtained. Further, the results are compared with the molecular dynamics results from the literature. The outcome indicates that the calculated relations are coincident with the molecular dynamics results.

• Steel and Composite Structures
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• 제45권3호
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• pp.389-408
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• 2022

Residual capacity is defined as the load carrying capacity of an RC column after undergoing severe damage. Evaluation of residual capacity of RC columns is necessary to avoid damage initiation in RC structures. The central aspect of the current research is to propose an empirical formula to estimate the residual capacity of RC columns after undergoing severe damage. This formula facilitates decision making of whether a replacement or a repair of the damaged column is adequate for further use. Available literature mainly focused on the simulation of explosion loads by using simplified pressure time histories to develop residual capacity of RC columns and rarely simulated the actual explosive. Therefore, there is a gap in the literature concerning general relation between blast damage of columns with different explosive loading conditions for a reliable and quick evaluation of column behavior subjected to blast loading. In this paper, the Arbitrary Lagrangian Eulerian (ALE) technique is implemented to simulate high fidelity blast pressure propagations. LS-DYNA software is utilized to solve the finite element (FE) model. The FE model is validated against the practical blast tests, and outcomes are in good agreement with test results. Multivariate linear regression (MLR) method is utilized to derive an analytical formula. The analytical formula predicts the residual capacity of RC columns as functions of structural element parameters. Based on intensive numerical simulation data, it is found that column depth, longitudinal reinforcement ratio, concrete strength and column width have significant effects on the residual axial load carrying capacity of reinforced concrete column under blast loads. Increasing column depth and longitudinal reinforcement ratio that provides better confinement to concrete are very effective in the residual capacity of RC column subjected to blast loads. Data obtained with this study can broaden the knowledge of structural response to blast and improve FE models to simulate the blast performance of concrete structures.

• 한국지반공학회논문집
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• 제23권5호
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• pp.131-141
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• 2007

말뚝 기초의 거동은 말뚝을 둘러싼 주변 지반의 특성에 좌우되므로, 항타 중의 지반거동을 계측하고 지반과 말뚝 거동간의 상관관계를 분석하는 연구가 필요하다. 본 연구에서는 말뚝 인접지반에 간극수압계, 경사계, 지표 변위말뚝, 그리고 말뚝 변형률계 등을 매설하여 낙동강 하구지역에 위치한 대심도 연약지반에 약 57m 관입깊이의 PHC 장대 말뚝을 항타하였을 때 말뚝 축하중 분포와 인접지반의 거동을 약 1년간 계측하고 그 결과를 분석하였다. 계측결과 매립하중과 항타에 의해 발생한 점토층 내의 과잉간극수압이 소산되면서 말뚝체 내에 부마찰력이 점차 증가하는 것으로 나타났다. 부마찰력에 의해 발생한 말뚝체의 최대 압축력 중 약 30%는 항타 중 증가한 과잉간극수압의 영향 때문으로 나타났다. 그러므로, 점성토 지반에 설치되는 대부분의 말뚝에 대하여 부마찰력을 고려한 설계를 수행할 필요성이 강조되었다.

• 콘크리트학회논문집
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• 제15권6호
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• pp.802-810
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• 2003

이 논문에서는 균열성장에 따른 파괴기준의 변화를 고려할 수 있는 수정 특이-파괴진행대 이론이 제안되었다. 제안된 파괴이론의 파괴특성은 균열의 성장기준이 되는 미소균열단에서 에너지해방률과 미소균열단 뒤에 형성되는 파괴진행대에서 균열면 응력-변위 관계이다. 제안된 파괴이론에 의한 파괴에너지는 기존의 콘크리트 파괴실험 결과로부터 평가된 파괴에너지를 충분히 만족할 수 있었다. 실험자료의 분석결과는 파괴진행대에서 균열면 응력-변위 관계는 시험편의 기하학적 특성에 큰 영형을 받지 않으나, 에너지해방률의 파괴기준은 시험편의 기하학적 특성과 하중조건뿐만 아니라 균열성장길이에 영향을 받는 것을 보여준다. 25mm의 균열성장까지 일정한 값을 유지하던 에너지해방률은 균열성장에 대해 선형으로 최대 값까지 증가하였다. 충분한 크기의 시험편에서 최대 에너지해방률은 최대하중에서 발생되었으며, 최대하중 이후의 균열성장에 대해 이 값을 유지하였다. 균열성장에 따른 파괴기준의 변화는 미소균열의 성장과 국부화에 의한 것으로 판단된다. 에너지해방률에 의한 파괴기준의 평가는 콘크리트 파괴거동의 크기효과를 단순화하며, 미소균열의 성장과 국부화에 대한 정량화에 사용될 수 있을 것으로 기대된다.