Automated structural design methods for reinforced concrete (RC) beam members have been widely studied with various techniques to date. Recently, artificial intelligence has been actively applied to various engineering fields. In this study, machine learning (ML) is adopted to make automated structural design model for RC beam members. Among various machine learning methods, a supervised learning was selected. When a supervised learning is applied to development of ML-based prediction model, datasets for training and test are required. Therefore, the datasets for rectangular and t-shaped RC beams was constructed by commercial structural design software of MIDAS. Five supervised learning algorithms, such as Decision Tree (DT), Random Forest (RF), K-Nearest Neighbor (KNN), Artificial Neural Networks (ANN), eXtreme Gradient Boosting (XGBoost) were used to develop the automated structural design model. Design moment (Mu), design shear force (Vu), beam length, uniform load (wu) were used for inputs of structural design model. Width and height of the designed section, diameter of top and bottom bars, number of top and bottom bars, diameter of stirrup bar were selected for outputs of structural design model. Performance evaluation of the developed structural design models was conducted using metrics sush as root mean square error (RMSE), mean square error (MSE), mean absolute error (MAE), and coefficient of determination (R2). This study presented that random forest provides the best structural design results for both rectangular and t-shaped RC beams.

By developing molds and facilities to horizontally mold the functional part of the dry-cast concrete block, We intend to develop molds and a series of facilities to horizontally mold the functional part of the dry-cast concrete block to increase production per cycle while maintaining existing production methods and major facilities. In order to do so, CAE analysis is first required to develop molds and facilities for horizontally molding the functional part of the drycast concrete block in the horizontal direction. The procedure will be carried out by reviewing the validity of boundary conditions and physical properties, 3D modeling, grid generation, construction of analysis models, model validity, analysis according to frequency changes, and analysis according to physical properties. First, through the comparison of two-point support, three-point support, and two-point and three-point support in the constraint conditions, We would like to compare it with the actual molded product in the horizontal direction.

By developing molds and facilities to horizontally mold the functional part of the dry-cast concrete block, We intend to develop molds and a series of facilities to horizontally mold the functional part of the dry-cast concrete block to increase production per cycle while maintaining existing production methods and major facilities. In order to do so, CAE analysis is first required to develop molds and facilities for horizontally molding the functional part of the drycast concrete block in the horizontal direction. The procedure will be carried out by reviewing the validity of boundary conditions and physical properties, 3D modeling, grid generation, construction of analysis models, model validity, analysis according to frequency changes, and analysis according to physical properties. First, through the comparison of two-point support, three-point support, and two-point and three-point support in the constraint conditions, We would like to compare it with the actual molded product in the horizontal direction. But first of all, it is considered three-point support in the constraint conditions in this paper.

본 연구에서는 방사선조사 유발 체적팽창(RIVE)이 원자력 발전소의 콘크리트 생체 차폐벽의 구조 건전성에 미치는 영향을 확인하 고자 하였다. 이를 위해 원자로 압력용기 감시 프로그램의 데이터를 사용하여 콘크리트 생체 차폐벽의 누적 중성자 조사 수준을 추정 하는 방법으로 원자로 압력용기(RPV) 내부 표면에서 차폐벽 외부까지의 누적 조사량의 감쇠를 계산하는 과정을 설명하고 콘크리트 의 방사선 조사 유발 체적팽창에 대한 모델을 제시하였다. 콘크리트 생체 차폐벽의 응력 상태는 온도의 영향을 받을 수 있기 때문에 방사선조사유발 체적팽창 효과와 더불어 운전 중 차폐벽의 온도 상승 효과도 고려하였다. 콘크리트 생체 차폐벽 구조에 대한 방사선 조사 유발 체적팽창과 온도의 영향을 평가한 결과, 차폐벽의 안쪽 표면 부근 영역의 압축 응력이 국부적으로 콘크리트의 압축 강도 한 계를 초과할 수 있으며, 외부 영역의 인장 응력은 균열을 유발할 가능성이 있음을 확인할 수 있었다. 또한 중성자 누적 조사량이 증가 하면 응력도 증가하는 경향을 보였다. 온도도 차폐벽의 응력 상태에 영향을 미치지만, 그 영향은 방사선조사 유발 체적팽창의 효과에 비해 그다지 크지 않았다. 향후 추가 연구를 통해 차폐구조물의 보다 현실적인 기하학적 구조, 중성자 조사량 분포, 그리고 차폐벽 내 부 보강 철근 요소 등을 포함하는 상세 모델을 바탕으로 콘크리트 생체 차폐벽에 설치되는 압력용기 지지 구조물 및 앵커 시스템에 대 한 영향 평가를 수행할 계획이다.

The purpose of this study is to experimentally analyze the seismic performance of a vertical irregular beam-column specimen reinforced with RBS (Replaceable Steel Brace System), a steel brace system. To evaluate the seismic performance of RBS, three specimens were manufactured and subjected to cycle loading tests. The stiffness ratio of beam-upper column of the non-retrofitted specimen was 1.2, and those of the two retrofitted specimens were 1.2 and 0.84. The stiffness ratio of the beam-lower column of all specimens was 0.36. And the stiffness ratio were used for variable. As a result of the experiment, the specimen retrofitted with RBS showed improved maximum load, effective stiffness and energy dissipation capacity compared to the non-retrofitted specimen with the same beam-upper column stiffness ratio. The specimen with 0.84 beam-upper column stiffness ratio showed improved performance compared to the specimen with 1.2 stiffness ratio.

This research introduces a novel probabilistic approach to consider the effects of uncertainty parameters during the design and construction process, providing a fresh perspective on the evaluation of the structural performance of reinforced concrete structures. The study, which categorized various random design and construction process variables into three groups, selected a two-story reinforced concrete frame as a prototype and evaluated it using a nonlinear analytical model. The effects of the uncertainty propagations to seismic responses of the prototype RC frame were probabilistically evaluated using non-linear dynamic analyses based on the Monte-Carlo simulation sampling with the Latin hypercube method. The derivation of seismic fragility curves of the RC frame from the probabilistic distributions as the results of uncertainty-propagation and the verification of whether the RC frame can meet the seismic performance objective from a probabilistic point of view represent a novel and significant contribution to the field of structural engineering.

This study was conducted to investigate the proper design of alpha board used to support concrete blocks under high loads. A board height of 50 mm was appropriate to ensure a deflection of 3 mm or less under a load of 5 tons. The trapezoidal shape of the vibration absorbers in the interior of the board reduced the maximum deflection by evenly distributing the deflection across the board width. The height of the board is the most important variable in preventing deflection, and for the same board height, adjusting the thickness of the top and bottom plates was more effective in reducing the amount of deflection than adjusting the thickness of the stiffener. The theoretical solution is a good tool for easily predicting the deflection of the board, as it shows a difference of 5 to 15% from the simulation results. However, as a 2D prediction model, the theoretical solution cannot represent the distribution of deflection over the entire board area, so the 3D simulations are necessary in predicting the amount of deflection over the entire board.

Strong ground motions at specific sites can cause severe damage to structures. Understanding the influence of site characteristics on the dynamic response of structures is crucial for evaluating their seismic performance and mitigating the potential damage caused by site effects. This study investigates the impact of the average shear wave velocity, as a site characteristic, on the seismic response of low-to-medium-rise reinforced concrete buildings. To explore them, one-dimensional soil column models were generated using shear wave velocity profile from California, and nonlinear site response analyses were performed using bedrock motions. Nonlinear dynamic structural analyses were conducted for reinforced concrete moment-resisting frame models based on the regional information. The effect of shear wave velocity on the structural response and surface ground motions was examined. The results showed that strong ground motions tend to exhibit higher damping on softer soils, reducing their intensity, while on stiffer soils, the ground motion intensity tends to amplify. Consequently, the structural response tended to increase on stiffer soils compared to softer soils.

교량, 터널 등 콘크리트 구조물의 건설 또는 사용 중 사고는 심각한 재산 및 인명 피해를 야기하기 때문에, 콘크리트 구조물의 증가와 동시에 Structural health monitoring(SHM)의 중요성 또한 높아졌 다. 하지만 현재까지 콘크리트 구조물의 안전 관리 및 유지관리는 주로 인력에 의한 육안 점검이 주를 이루고 있으며, 이는 주관적이고 정성적인 관리 수준에 머무르고 있어 안전성 평가 결과에 대한 신뢰 성 및 실시간 상태 파악과 대응 측면에 한계가 존재한다. 이에 본 연구에서는 현재 활발하게 연구되고 있는 탄소나노튜브를 활용하여 기다란 바 형태의 Carbon nanotube reinforced polymer(CNRP) Bar를 개발하였으며, 이를 콘크리트 구조물에 적용하였다. 구조물 변형에 따른 CNRP Bar의 센싱 성능을 파 악하기 위해 3점 굽힘 시험을 진행하였고, 동시에 콘크리트 구조물 내 CNRP Bar의 전기적 변화를 분석하였다. 실험 결과 콘크리트 구조물에 균열 발생 전 굽힘 응력에 의해 CNRP Bar의 저항이 감소 하였고, 균열 발생 후 균열이 커짐에 따라 저항이 증가하는 거동을 보였다. 이를 통해 CNRP Bar는 콘크리트 구조물에 용이하게 적용할 수 있는 매립형 센서로써 사용 가능하고, 이는 콘크리트 구조물의 안전성을 효율적으로 모니터링하는 시스템으로 발전 가능할 것으로 판단된다.

구조물 보수 부위의 손상, 재 박리 등의 2차 피해가 이어지며, 보수 부위의 새로운 거동 평가 기법 에 대한 연구의 필요성이 대두되고 있다. 현재 구조물 보수 부위의 거동을 알기 위해서 주로 인력 중 심의 구조물 외관 검사를 진행하고 있으나, 단편적인 검사 결과를 얻게 되어 지속적이고 세밀한 점검 이 어려운 실정이다. 따라서, 본 연구에서는 탄소나노튜브 기반 폴리머 콘크리트를 활용해 압축과 같 은 외부 응력에 대한 탄소나노튜브 함량별 전기적 변화를 분석하였으며, 균열이 발생한 콘크리트 구조 물을 보수 후 응력을 가해 거동에 따른 전기적 변화를 평가하였다. 압축 시험 결과, 응력에 따른 탄소 나노튜브 기반 폴리머 콘크리트의 전기 저항이 감소하며, 탄소나노튜브 함량이 낮을수록 응력에 대한 저항 감소 폭이 넓게 나타나며 민감도가 증가하였다. 균열 보수 시험 결과, 보수 부위에 응력이 가해 졌을 때 전기 저항이 감소해 앞서 진행된 실험 결과와 동일한 경향을 보였으며, 또한 응력이 가해지지 않을 때 초기 저항으로 회복하는 경향을 보여 구조물 보수 부위 거동에 대한 평가가 가능한 것으로 검 증되었다. 이를 통해, 탄소나노튜브 기반 폴리머 콘크리트는 구조물에 적용이 가능하며, 구조물 보수 후에도 가해지는 응력에 대한 지속적인 감지가 가능해 보수 부위 거동 평가가 가능할 것으로 판단된다.

The purpose of this study is to experimentally analyze the seismic performance of beam-column specimens with vertical irregular, which were reinforced with RHS (Replaceable steel haunch system). a steel haunch system. To evaluate the seismic performance of the RHS, three specimens were manufactured and subjected to cycle loading tests. Retrofitted specimens have different beam-upper column stiffness ratio as a variable. The stiffness ratio of beam-upper column were considered to be 1.2 and 0.84. As a result of the test, the specimen reinforced with RHS showed improved maximum load and effective stiffness, and energy dissipation capacity compared to the non-retrofitted specimen with same beam-upper column stiffness ratio. The specimen with 0.84 beam-upper column stiffness ratio showed improved performance than the specimen with 12.

By developing molds and facilities to horizontally mold the functional part of the dry-cast concrete block, We intend to develop molds and a series of facilities to horizontally mold the functional part of the dry-cast concrete block to increase production per cycle while maintaining existing production methods and major facilities. In order to do so, CAE analysis is first required to develop molds and facilities for horizontally molding the functional part of the drycast concrete block in the horizontal direction. The procedure will be carried out by reviewing the validity of boundary conditions and physical properties, 3D modeling, grid generation, construction of analysis models, model validity, analysis according to frequency changes, and analysis according to physical properties. First, through the comparison of two-point support, three-point support, and two-point and three-point support in the constraint conditions, We would like to compare it with the actual molded product in the horizontal direction. But first of all, it is considered two-point support in the constraint conditions in this paper.

Due to the aging of a building, 38.8% (about 2.82 million buildings) of the total buildings are old for more than 30 years after completion and are located in a blind spot for an inspection, except for buildings subject to regular legal inspection (about 3%). Such existing buildings require users to self-inspect themselves and make efforts to take preemptive risks. The scope of this study was defined as the general public's visual self-inspection of buildings and was limited to structural members that affect the structural stability of old buildings. This study categorized possible damage to reinforced concrete to check the structural safety of buildings and proposed a checklist to prevent the damage. A damage assessment methodology was presented during the inspection, and a self-inspection scenario was tested through a chatbot connection. It is believed that it can increase the accessibility and convenience of non-experts and induce equalized results when performing inspections, according to the chatbot guide.

In this study, the structural performance of the specimen fabricated through 3D printing was evaluated through monotonic loading experiments analysis to apply to 3D printed structures. The compression and flexural experiments were carried out, and the experimental results were compared to the finite element model results. The loading directions of specimens were investigated to consider the capacity of specimens with different curing periods, such as 7 and 28 days. As a result, the strength tended to increase slightly depending on the stacking direction. Also, between the 3D-printed panel composite and the non-reinforced panel, the bending performance depended on the presence or absence of composite reinforcement.

PURPOSES : Advancements in science and technology caused by industrialization have led to an increase in particulate matter emissions and, consequently, severity of air pollution. Nitrogen oxide (NOx), which accounts for 58% of road transport pollutants, adversely affects both human health and the environment. A test-bed was constructed to determine NOx removal efficiency at the roadside. TiO2, a material used to reduce particulate matter, was used to remove NOx. It was applied to a vertical concrete structure using the dynamic pressurized penetration TiO2 fixation method, which can be easily applied to vertical concrete structures. This study was conducted to evaluate the NOx removal efficiency of the dynamic pressurized-penetration TiO2 fixation method in a test-bed under real roadside conditions. METHODS : A test-bed was constructed in order to determine the NOx removal efficiency using the dynamic pressurized penetration TiO2 fixation method on the roadside. The dynamic pressurized-penetration TiO2 fixation method was applied by installing a vertical concrete structure. NOx was injected into the test-bed using an exhaust gas generator. By installing a shading screen, the photocatalytic reaction of TiO2 was suppressed to a maximum concentration of 1000 ppb along the roadside. The removal efficiency was evaluated by measuring NOx concentrations. In addition, illuminance was measured using an illuminance meter. RESULTS : From the results of the analysis of the NOx removal efficiency in the test-bed which the dynamic pressurized type TiO2 fixation method was applied to, an average removal efficiency ranging from 18% to 40% was achieved, depending on the illuminance. Similarly, according to the results of the evaluation of the NO removal efficiency, an average of removal efficiency ranging from 20% to 62% was achieved. Thus, the NOx removal efficiency increased when the illuminance was high. CONCLUSIONS : From the results of the experiment conducted, the efficiency of NOx removal per unit volume was obtained according to the illuminance of TiO2 concrete along an actual road. Field applicability of the dynamic pressurized-penetration-type TiO2 fixation method to vertical concrete structures along roads was confirmed.