• 한국구조물진단유지관리공학회 논문집
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• 제22권4호
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• pp.19-26
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• 2018

이 연구는 유공보강근의 형상에 따른 철근콘크리트 유공 보의 전단저항성능을 평가하기 위하여 4체의 실험체를 제작하여 전단실험을 수행하였다. 실험의 주요변수는 유공의 유무, 유공보강 유무, 유공 보강근의 형상으로 하였으며, 제안 유공 보강근은 시공성을 고려하여 사각형과 마름모형이 혼합된 나선형 형태이다. 실험결과, 이 연구에서 제안된 유공보강근은 유공 주변의 균열을 효과적으로 제어하여 실험체의 전단력 향상에 효과적임을 확인하였다. 또한 현행설계기준은 유공 보강근을 배근한 실험체의 실험결과를 과소평가하는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권5호
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• pp.102-109
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• 2010

이 논문에서는 고강도 횡보강근을 가진 철근콘크리트 보의 부착 거동을 연구하였다. 제안된 비폐쇄형 U자 보강근의 부착 성능을 평가하기 위하여 총 4개의 철근콘크리트 보를 실험하였다. 제안된 비폐쇄형 U자 보강근은 쉽게 설치할 수 있는 구조를 가졌을 뿐만 아니라 부착 균열을 억제함으로써 철근콘크리트 보의 부착 성능을 증가시킬 수 있다. 이 연구에서는 실험체의 부착 응력과 미끄러짐을 구하기 위하여 Ichinose가 제안한 실험방법을 따랐다. 주요 실험변수는 횡보강근의 항복강도와 보강근비 및 구속의 형태로 하였다. 실험결과, 제안된 비폐쇄형 U자 보강근은 고강도 횡보강근을 사용한 철근콘크리트 보의 부착 성능을 효과적으로 향상시켰음을 확인할 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제25권5호
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• pp.76-85
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• 2021

이 연구에서는 유공보강근의 형상에 따른 RC 유공보의 구조성능을 평가하기 위하여 전단실험을 수행하였다. 실험체는 총 4체이며, 주요변수는 유공의 유무, 유공 보강 유무, 유공 보강근의 형상이다. 이 연구에서는 사각형과 팔각형이 혼합된 나선형의 유공보강근을 개발하였으며, 이를 기존 Band형과 비교하였다. 실험결과, 제안 유공 보강근으로 유공을 보강한 실험체는 타 실험체에 비하여 최대 전단력과 최대 전단력 이후 에너지소산면적이 증가하는 것으로 나타났다. 따라서 제안 유공 보강근은 유공 주위의 균열제어와 함께 전단성능의 향상에 효과적임을 확인하였다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.184-191
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• 2003

In this paper, a mathematical framework based on a homogenisation technique to simulate 'umbrella arch reinforcement system' (UARS) and its implementation into a 3D Finite Element program that can consider stage construction situations are presented. The constitutive model developed allows considering the main design parameters of the problem and only requires geometrical and mechanical properties of the constituents. Additionally, the use of a homogenisation approach implies that the generation of the Finite Element mesh can be easily produced and that re-meshing is not required as basic geometrical parameters such as the orientation of the pipes are changed. The model developed is used to simulate tunnelling with the UARS. From the analyses, the effects of the main design parameters on the elastic and the elastoplastic analyses are considered.

• Structural Engineering and Mechanics
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• 제51권3호
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• pp.361-375
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• 2014

The main aim of this paper is to investigate the relationship between thickness and height of the axially symmetric cylindrical reinforced concrete (RC) walls by the help of a meta-heuristic optimization procedure. The material cost of the wall which includes concrete, reinforcement and formwork, was chosen as objective function of the optimization problem. The wall thickness, compressive strength of concrete and diameter of reinforcement bars were defined as design variables and tank volume, radius and height of the wall, loading condition and unit cost of material were defined as design constants. Numerical analyses of the wall were conducted by using superposition method (SPM) considering ACI 318-Building code requirements for structural concrete. The optimum wall thickness-height relationship was investigated under three main cases related with compressive strength of concrete and density of the stored liquid. According to the results, the proposed method is effective on finding the optimum design with minimum cost.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.254-260
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• 1997

Chloride-induced corrosion of reinforcement is one of the main factors which cause the deterioration of concrete structures. Durability and service lives of the concrete sturctures should be predicted in order to minimize the risk of corrosion of reinforcement. The objective of this study is to suggest the basis of analytical methods of predicting the corrosion threhold time of concrete structures. Based on the chemistry and physics of chloride ion transport and corrosion process, chloride intrusion with various exposure conditions, variability of diffusivity and transport of pore water in concrete are taken into consideration in applying finite element formulation to the predicion of corrosion threhold time. The effects of main factors on the prediction of chloride intrusion and corrosion threhold time are examined. In addition, after chloride diffusivities of several mixture proportions with different parameters are measured by chloride diffusion test, the exemplary anayses of corrosion threhold time of those mixture proportions are carried out.

• 한국공간구조학회지
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• 제24권2호
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• pp.17-23
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• 2024

• Advances in concrete construction
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• 제9권3호
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• pp.313-326
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• 2020

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

• 한국공간구조학회논문집
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• 제23권2호
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• pp.29-36
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• 2023

Reinforcement learning (RL) is widely applied to various engineering fields. Especially, RL has shown successful performance for control problems, such as vehicles, robotics, and active structural control system. However, little research on application of RL to optimal structural design has conducted to date. In this study, the possibility of application of RL to structural design of reinforced concrete (RC) beam was investigated. The example of RC beam structural design problem introduced in previous study was used for comparative study. Deep q-network (DQN) is a famous RL algorithm presenting good performance in the discrete action space and thus it was used in this study. The action of DQN agent is required to represent design variables of RC beam. However, the number of design variables of RC beam is too many to represent by the action of conventional DQN. To solve this problem, multi-agent DQN was used in this study. For more effective reinforcement learning process, DDQN (Double Q-Learning) that is an advanced version of a conventional DQN was employed. The multi-agent of DDQN was trained for optimal structural design of RC beam to satisfy American Concrete Institute (318) without any hand-labeled dataset. Five agents of DDQN provides actions for beam with, beam depth, main rebar size, number of main rebar, and shear stirrup size, respectively. Five agents of DDQN were trained for 10,000 episodes and the performance of the multi-agent of DDQN was evaluated with 100 test design cases. This study shows that the multi-agent DDQN algorithm can provide successfully structural design results of RC beam.

• 한국산학기술학회논문지
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• 제20권8호
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• pp.279-285
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• 2019

다양한 형태의 선체 진동 중, 선체 선미 및 거주구의 횡방향 진동은 대부분 주기관의 횡기진력으로부터 유발되는데, 주기관과 연결된 주변 구조물과의 공진이 발생 할 수 있으므로 공진회피 설계가 반드시 필요하다. 공진 회피를 위한 가진 주파수는 주기관 및 프로펠러 사양으로부터 추정 가능하나, 기관실 주변 구조물의 고유 진동수는 형상의 다양성 등에 의해 추정이 쉽지 않고 경험을 위주로 한 방진 설계가 수행되고 있는 현실이며, 이로 인해 시운전 중에 발생하는 진동 문제는 공정지연, 현장 인력의 과다 투입 및 설계의 반복 수행 등 많은 문제점이 발생하고 있다. 본 연구에서는8,600TEU급 컨테이너선을 대상으로 유연한 설계를 위해 선체 구조배치의 변경 없이 주기관만 12기통에서 10기통으로 변경하는 경우에 대해 주기관 횡진동에 의한 공진 문제를 다루었다. 연구 결과로서, 주기관 횡기진력과 기관실 주변 구조와의 공진 회피를 위한 효율적인 구조보강 설계지침을 제시하였으며, 설계 현장의 실제적인 방진설계 지침으로 활용이 기대된다.