• 콘크리트학회논문집
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• 제14권2호
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• pp.239-248
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• 2002

철근 콘크리트 면부재의 주기거동을 나타내기 위하여 소성모델과 손상모델의 통합구성모델을 개발하였다. 인장-압축을 받는 콘크리트의 응력은 개념적으로 콘크리트의 스트럿 작용에 의한 압축응력과 인장균열에 의한 인장응력의 합으로 정의하였다. 인장균열의 비등방손상에 의하여 영향을 받는 압축파괴의 등방손상을 나타내기 위하여 다중파괴기준을 갖는 소성모델을 사용하였으며, 다중균열 방향에서 인장응력-변형률 관계를 나타내기 위하여 다중고정균열손상모델과 인장균열의 소성유동모델의 개념을 사용하였다. 이러한 통합모델은 주기 인장-압축 상태의 철근 콘크리트의 거동측성, 즉 다중 인장균열 방향, 점진적으로 회전하는 균열 손상, 콘크리트의 압축파괴를 나타낼 수 있다. 제안된 구성모델은 유한요소해석에 적용되었으며, 주기하중을 받는 철근 콘크리트 전단패널 및 전단벽에 대한 기존의 실험결과들과의 비교를 통해 검증되었다.

• Structural Engineering and Mechanics
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• 제66권2호
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• pp.217-227
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• 2018

In the last decades, valuable results have been reported regarding conventional passive, active, semi-active, and hybrid structural control systems on two-dimensional and a few three-dimensional shear buildings. In this research, using a three-dimensional finite element model of high-rise concrete structures, designed by performance based plastic design method, it was attempted to construct a relatively close to reality model of concrete structures equipped with Tuned Mass Damper (TMD) by considering the effect of soil-structure interaction (SSI), torsion effect, hysteresis behavior and cracking effect of concrete. In contrast to previous studies which have focused mainly on linearly designed structures, in this study, using performance-based plastic design (PBPD) design approach, nonlinear behavior of the structures was considered from the beginning of the design stage. Inelastic time history analysis on a detailed model of twenty-story concrete structure was performed under a far-field ground motion record set. The seismic responses of the structure by considering SSI effect are studied by eight main objective functions that are related to the performance of the structure, containing: lateral displacement, acceleration, inter-story drift, plastic energy dissipation, shear force, number of plastic hinges, local plastic energy and rotation of plastic hinges. The tuning problem of TMD based on tuned mass spectra is set by considering five of the eight previously described functions. Results reveal that the structural damage distribution range is retracted and inter-story drift distribution in height of the structure is more uniform. It is strongly suggested to consider the effect of SSI in structural design and analysis.

• 한국농공학회논문집
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• 제63권2호
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• pp.75-84
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• 2021

As the weather changes become frequent, weather disasters are increasing, causing more damage to plastic greenhouses. Among the damage caused by various disasters, damage by snow to the greenhouse takes a relatively long time, so if an alarm system is properly prepared, the damage can be reduced. Existing greenhouse design standards and snow warning systems are based on snow depth. However, even in the same depth, the load on the greenhouse varies depending on meteorological characteristics and snow density. Therefore, this study aims to secure the structural safety of greenhouses by developing sensors that can directly measure snow loads, and analysing the warning criteria for load using a stochastic model. Markov chain was applied to estimate the failure probability of various types of greenhouses in various regions, which let users actively cope with heavy snowfall by selecting an appropriate time to respond. Although it was hard to predict the precise snow depth or amounts, it could successfully assess the risk of structures by directly detecting the snow load using the developed sensor.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.123-128
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• 2002

In this paper, an averaged constitutive model of concrete and reinforcing bars for RC structure and path-dependent Ohsaki's model for soil are applied, and an elasto-plastic interface model having thickness is preposed for seismic analysis of underground RC subway station structure. A finite element analysis technique is developed by applying aforementioned constitutive equations and verified through seismic analysis of underground RC subway station. Then, failure mechanisms of the RC subway station structure under seismic action are numerically derived. Then, failure modes and damage levels of the station are also analytically evaluated for the cases of several designs of the underground RC station.

• Geomechanics and Engineering
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• 제2권1호
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• pp.1-18
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• 2010

The analysis of structure response and design of buried structures subjected to dynamic destructive loads have been receiving increasing interest due to recent severe damage caused by strong earthquakes and terrorist attacks. For a comprehensive design of buried structures subjected to blast loads to be conducted, the whole system behaviour including simulation of the explosion, propagation of shock waves through the soil medium, the interaction of the soil with the buried structure and the structure response needs to be simulated in a single model. Such a model will enable more realistic simulation of the fundamental physical behaviour. This paper presents a complete model simulating the whole system using the finite element package ABAQUS/Explicit. The Arbitrary Lagrange Euler Coupling formulation is used to model the explosive charge and the soil region near the explosion to eliminate the distortion of the mesh under high deformation, while the conventional finite element method is used to model the rest of the system. The elasto-plastic Drucker-Prager Cap model is used to model the soil behaviour. The explosion process is simulated using the Jones-Wilkens-Lee equation of state. The Concrete Damage Plasticity model is used to simulate the behaviour of concrete with the reinforcement considered as an elasto-plastic material. The contact interface between soil and structure is simulated using the general Mohr-Coulomb friction concept, which allows for sliding, separation and rebound between the buried structure surface and the surrounding soil. The behaviour of the whole system is evaluated using a numerical example which shows that the proposed model is capable of producing a realistic simulation of the physical system behaviour in a smooth numerical process.

• Earthquakes and Structures
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• 제11권4호
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• pp.649-664
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• 2016

A seismic damaged bridge may be hit again by a strong aftershock or another earthquake in a short interval before the repair work has been done. However, discussions about the impact of the unrepaired damages on the residual earthquake resistance of a steel bridge are very scarce at present. In this paper, nonlinear time-history analysis of a steel arch bridge was performed using multi-scale hybrid model. Two strong historical records of main shock-aftershock sequences were taken as the input ground motions during the dynamic analysis. The strain response, local deformation and the accumulation of plasticity of the bridge with and without unrepaired seismic damage were compared. Moreover, the effect of earthquake sequence on crack initiation caused by low-cycle fatigue of the steel bridge was investigated. The results show that seismic damage has little impact on the overall structural displacement response during the aftershock. The residual local deformation, strain response and the cumulative equivalent plastic strain are affected to some extent by the unrepaired damage. Low-cycle fatigue of the steel arch bridge is not induced by the earthquake sequences. Damage indexes of low-cycle fatigue predicted based on different theories are not exactly the same.

• 한국산학기술학회논문지
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• 제7권3호
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• pp.409-413
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• 2006

미시학적 비배수 크리프 현상의 누적 변형은 점성토 시공지역 지반의 전반 파괴를 야기 할 수 있다. 본 연구에서는 점성토의 비배수 크리프 거동을 예측하기 위하여 Perzyna의 일반 점성이론을 소성론의 개념에서 간략화하고 수정 Cam clay 모델 및 데미지 이론을 포함하는 하나의 시간의존적 구성방정식을 유도하였다. 유도된 구성방정식을 활용하여 예측한 크리프 거동은 비배수 크리프 파괴를 포함하는 크리프 실험결과와 잘 부합하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.378-381
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• 2009

In this study, the repetitive loading-unloading tensile tests with AZ31B magnesium sheet metal have been conducted under various elevated temperatures to check out how the Young's moduli of the sheets evolve during the plastic deformation. The loading-unloading tests have been carried out at every 1% of strain increment. With the tested results, some damage parameters of magnesium sheets based on the Lemaitre's continuum damage theory could be calculated at room temperature, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$ and $250^{\circ}C$. It has been shown that the critical damage parameters obtained in all temperature conditions are within the range of 0.12 to 0.18.

• 대한기계학회논문집
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• 제9권2호
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• pp.140-149
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• 1985

본 연구는 오오스테나이트계 STS 316 스테인레스강에 대하여 온도 550.deg. C의 대 기중에서, 변형율제어에 의한 인장-압축에 크리이프 유지시간을 갖는 고온저사이클 피 로시험을 하여 변형율폭 및 크리이프 유지시간이 피로수명에 미치는 영향과 파단면을 주사형 전자현미경으로 관찰하여 크리이프-피로 상호작용이 피로파단면에 미치는 크리 이프 효과를 실험 고찰하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.483-488
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• 2002

In this paper numerical algorithm for the continuum large crack model is proposed based on the return-mapping formulation. The numerical test results show that the present algorithm works appropriately under cyclic loading. It is also shown that in continuum damage models a large crack model to prevent excessive tensile plastic strain should be used to have realistic cyclic loading simulation results.