최근 국내에서는 고층 벽식 아파트 건설 시, 하부 주차공간과 공용공간 확보를 위하여 RC 전이슬래브 시스템을 사용하는 경우가 증가하고 있다. 하지만 두께가 얇은 RC 무량판 슬래브를 위해 개발된 설계방법 및 구조성능평가 방법을 두께가 매우 두꺼운 전이슬래브 구조설계에 그대로 사용하고 있다는 문제점이 있다. 따라서 합리적인 전이슬래브의 구조설계를 위해서는 RC 전이슬래브 시스템의 2면 전단거동 양상에 대한 명확한 분석이 필요하다. 이에 따라 본 연구에서는 전이슬래브의 두께, 콘크리트 강도, 전단경간비, 철근비 등 다양한 설계변수에 따라 비선형 FEM을 이용하여 전이슬래브의 2면 전단거동을 분석 하였다. 또한 비선형 FEM 해석결과와 기존의 2면 전단강도 평가식으로 예측한 전단강도를 비교분석하여 기존 평가식의 전이슬래브 2면 전단강도 평가 유효성을 검토하였다.

초고층 건물의 횡변위 제어를 위하여 사용되는 아웃리거를 기존의 철골 트러스 대신에 철근콘크리트 벽체로 대체할 수 있다. 철근콘크리트 아웃리거 벽체를 외부 기둥에 연결할 경우에는 축력뿐만 아니라 전단력과 모멘트가 외부 기둥에 유발될 수 있다. 본 연구에서는 아웃리거 벽체 외단부의 회전으로 인한 외부 기둥의 전단력을 수식으로 유도하고 그 값을 유한요소해석 결과와 비교하였다. 유한요소해석에서는 층별 연결보의 효과와 전단벽과 아웃리거를 보와 평면응력요소로 모델링한 효과를 분석하였다. 층별 연결보의 효과는 거의 없었으며 평면응력요소는 보요소보다 더 큰 강성을 가진 것으로 해석되었다. 아웃리거 벽체의 외단부 회전으로 인한 외부기둥의 층간 회전각과 전단력은 허용값에 비하여 상당히 작은 값이 발생하였다. 따라서 초고층 건물에 철근콘크리트로 된 아웃리거 벽체를 적용할 경우에도 외부 기둥에 유발되는 전단력과 모멘트에 대하여 별도의 검토를 할 필요는 없을 것으로 판단된다.

ACT Column은 기존 CFT 기둥보다 얇은 강판으로도 동일한 구조적 성능을 발휘할 수 있으며, 콘크리트의 구속효과와 강관의 항복 후 좌굴응력의 향상을 기대할 수 있다. ACT Column은 보-기둥 접합부에 외다이아프램을 사용한 접합상세가 적용된다. 그러나 ACT Column 외부에 콘크리트가 피복되는 SRC 타입에서는 외다이아프램을 사용한 접합부의 적용이 난해하다. 그래서 ACT Column의 외부에 수직 스티프너와 수평 스티프너를 사용한 접합상세를 제안하였다. 본 논문에서는 제안상세를 대상으로 단순인장실험을 통해 성능검증을 수행하였다. 실험체는 현장에 사용량이 많은 크기의 ACT Column 으로 2개의 실험체를 제작하였다. 보 플랜지와 보 플랜지의 양측부에 부착된 윙플레이트를 통해 보 플랜지의 단면 내력이 링다이아프램으로 전달되는 명확한 응력전달매커니즘을 나타내었으며, 보 플랜지 전단면이 소성화되어 파괴되었다. 윙플레이트의 크기가 클수록 하중전달량이 증가하였으며, 제안한 접합상세의 강도평가식을 제시하였다.

Existing reinforced concrete building structures have seismic vulnerabilities under successive earthquakes (or mainshock-aftershock sequences) due to their inadequate column detailing, which leads to shear failure in the columns. To improve the shear capacity and ductility of the shear-critical columns, a fiber-reinforced polymer jacketing system has been widely used for seismic retrofit and repair. This study proposed a numerical modeling technique for damaged reinforced concrete columns repaired using the fiber-reinforced polymer jacketing system and validated the numerical responses with past experimental results. The column model well captured the experimental results in terms of lateral forces, stiffness, energy dissipation and failure modes. The proposed column modeling method enables to predict post-repair effects on structures initially damaged by mainshock.

대부분의 소비자들이 질 좋은 음식을 선호하기 때문에, 농장에서는 소비자들의 욕구를 충족시키기 위해 다양한 시설을 이용하고 있다. 가장 대표적인 시설은 플라스틱 온실과 유리온실이다. 국내의 플라스틱 온실 과 유리 온실의 측고는 3m 내외이다. 결과적으로 작물의 생산성이 제한되고, 이를 해결하기 위해서는 기둥의 높이를 증가시켜 온실의 측고를 높이는 것이다. 온실 기둥상승 장치는 멈춤장치, 공압 실린더 및 수직 부재 등으로 구성된다. 공압 실린더는 안전계수 1.5를 고려하여 직경 160mm와 행정길이 50mm로 설계하였으며, 노즐을 통하여 공기의 압력을 제어하였다. 1행정 시간을 30초 내외로 설계하기 위해서는 21.5L·min-1 공기가 필요한 것으로 나타났다. 따라서 노즐의 직경은 0.5mm로 설계하였다. 압력이 0.9 MPa일 때 평균 인상력은 13,805N으로 계산된 값 15,612N에 근접하였다. 현장 시험결과 같은 열의 기둥과 오차가 발생하지 않았으며, 실제 유리 및 플라스틱 온실에 적용 가능한 것으로 판단되었다

In this study, we compared the MZVI (Microscale Zero-Valent Iron) and NZVI (Nanoscale Zero-Valent Iron) for reactivity and mobility in a column to reduce nitrate, which is a major pollutant in Korea, and investigated the effect of operational parameters on the NZVI filled column. For the comparison of MZVI and NZVI, samples were collected for 990 minutes using fractionator in the similar operation conditions (MZVI 10g, NZVI 2g). The nitrate reduction efficiency of NZVI was about 5 times higher than that of MZVI, which was about 7.45% and 38.75% when using MZVI and NZVI, respectively. In the mobility experiment, the MZVI descended due to gravity while NZVI moved up with water flow due to its small size. Furthermore, the optimum condition of NZVI filled column was determined by changing the flow rate and pH. The amount of Fe ions was increased as the pH of the nitrate solution was lowered, and the nitrate removal rate was similar due to the higher yield of hydroxyl groups. The removal rate of nitrate nitrogen was stable while flow rate was increased from 0.5 mL/min to 2.0 mL/min (empty bed contact time: 2.26 min to 0.57 min). NZVI has a high reduction rate of nitrate, but it also has a high mobility, so both of reactivity and mobility need to be considered when NZVI is applied for drinking water treatment.

As buildings are becoming larger, demand for large-scale composite columns for heavy load is increasing. Welded built-up CFT column (ACT Column I) previously developed by authors of this study is structurally stable and economical. Characteristic of welded built-up CFT column is that there is a limitation of cross-sectional size and application of external diaphragm connection to ensure continuity of rib. Then, composite mega column (ACT Column II) was developed to improve limit of cross-sectional size. Composite mega column has a closed cross section like welded built-up CFT column, but thick plate is inserted between cold-formed steel to expand cross section size. However, when external diaphragm connection is applied to composite mega column, amount of steel is increased greatly and interference with finishing material occurs. In this study, internal diaphragm connection is applied through characteristic of composite mega column to which beam flange or stiffener can be attached to plate. In order to analyze this, simple tensile experiment of composite mega column connection with T-shaped stiffener was performed.

Unlike column-to-beam connections in reinforced concrete frames, column-to-beam connections are generally of the same type. Vertical load (D.L + L.L) and horizontal load (wind load, seismic load) are not the same in the upper and lower flange stress history. In the case of beams bonded to synthetic CFT columns, the tensile force is transmitted through the steel pipe column, and the compressive force is transmitted to the filled concrete, so the seismic performance is excellent even if the column has a relatively thin cross section. Also, in case of beam the composite CFT column, tensile force is taken by the steel pipe column, and the compressive force is caught by the inner concrete, and the shape of the column joint can be changed. In this study, the stress distribution of buildings is investigated according to the size and characteristics of the building, and the load history of the upper and lower flanges according to the building type is checked to show the structural possibility of the Asymmetric Diaphragms joint.

As buildings are becoming larger, demand for mega-sized composite columns (over 1-meter diameter) is increased. We have developed and commercialized welded built-up CFT column (ACT Column I) since 2005 which are structurally stable and economical using cold-formed steel with rib. However, there has a limit in size of cross section (618˟618mm) by a fabrication facilities. And due to characteristics of closed cross section, there has a limit to construction of connection of moment frame. Composite mega column (ACT Column II) has same concept of forming closed cross section. But in order to enlarge cross sectional size, thick plate is inserted between cold-formed steels. Since composite mega column can control thickness and width of thick plate, steel or composite beams can be directly attached to the connection. In this study, we propose strength formula of composite mega column to beam connections with T-shaped stiffener as internal diaphragm and verified through finite element analysis and simple tensile experiment.

This study presents a sustainable design method to optimize the embodied energy and CO2 emission complying with the design code for reinforced concrete column. The sustainable design method effectively achieves the minimization of the environmental load and energy consumption whereas the conventional design method has been mostly focused on the cost saving. Failure of reinforced concrete column exhibits compressive or tensile failure mode against an external force such as flexure and compression; thus, optimization analyses are conducted for both failure modes. For the given sections and reinforcement ratios, the optimized sections are determined by optimizing cost, embodied energy, and CO2 emission and various aspects of the sections are thoroughly investigated. The optimization analysis results show that 25% embodied energy and 55% CO2 emission can be approximately reduced by 10% increase in cost. In particular, the embodied energy and CO2 emission were more effectively reduced in the tensile failure mode rather than in the compressive failure mode. Consequently, it was proved that the sustainable design method effectively implements the concept of sustainable development in the design of reinforced concrete structure by optimizing embodied energy consumption and CO2 emission.

To investigate the cyclic characteristics of the retrofitted exterior joints of RC frame with haunch, 70% scaled 6 beam-column exterior joint subassemblies were designed according to design guideline according to 1988 and tested with cyclic loading up to 3.5% story drift ratio. During the experiments axial forces are applied to columns to simulate gravity load. Experimental results shows that the strength of retrofitted specimens was increased steadily until 2.5% story drift ratio and their strengths increased more than 1.7 times of the non-retrofitted in case that main bar was bent away from exterior joint. The joint strength and effective stiffness of the retrofitted specimen was increased and results in more deformation capacity compared to the non-retrofitted.

As the ridges become larger and larger, a structural type that enables effective utilization of the long span and space is required. In the construction stage, the steel column supports the installation load. However, in order to secure the stability against the out - of - plane deformation of the steel column due to the lateral pressure when the concrete is laid, a binding frame is installed inside the steel pipe at constant intervals to resist the concrete installation pressure. When the concrete is cured and its performance as a composite section is exerted, a stress is generated which pushes the steel pipe out of the plane by the column compressive force. In this case, since the binding frame controls the deformation, the local buckling is delayed and the constraining effect on the concrete is increased. In order to evaluate the structural performance and behavior of the composite mega column according to the eccentricity effect and the effect of the binding frame, we carried out a structural test by fabricating eight monopole specimens with the binding frame reinforcement, reinforcing gap, reinforced cross section and eccentricity , And the experimental results are compared with the KBC2016 design formula.

The utilization of composite columns is increasing due to the construction of high-rise buildings and large buildings. The commercially available concrete chimney steel column (ACT I) is a stable and economical structure, but there is a limit in the section size to be applied to a composite column subjected to a high load. We have developed a composite mega column with an integral structure by adding a plate to the central part of the ACT I column and installing a binding frame at a certain interval inside the central plate. In this study, to evaluate the compressive performance of the composite mega column, four test specimens were constructed with binding frame reinforcement, reinforcement spacing, and reinforced cross - sectional area. The structural performance of the composite section is compared with that of KBC2016 to evaluate the behavior of the specimen.

The paper presents an experimental evaluation of RC columns retrofitted by TRC(Textile fabric Reinforced Concrete). TRC were made using textile fabric fiber and self leveling mortar. A total of three specimens was constructed and was performed cyclic loading test. One specimen was a non-retrofitted column, while others were retrofitted with textile fabric and sheet type fiber. By comparing with non-retrofitted specimen, the maximum strength and ductility of retrofitted RC column was improved compared to non-retrofitted RC column.

This paper investigated impact resistance capacity and failure mode of strengthened column with PROTECT (Poly-Resilience-Oriented hybrid TEChnology plaTe) panel by analytical study. PROTECT panel is the composite panel with two steel plates and nano-composite. In order to perform impact analysis, dynamic properties of concrete, steels and nano-composite were determined. Finite element analysis was performed with these properties under the drop-weight impact. From the FEA, different failure modes corresponding to different columns were derived.

Composite columns are increasingly used due to the construction of super-tall buildings and large-scale buildings. Studies on the shapes of and construction technologies for structural members using steel tubes are being conducted actively. Welded built-up CFT columns previously developed and commercialized by the authors of this study (ACT-1 columns) are structurally stable and economically efficient. However, the 1m limit in the width of the columns and their small interior spaces impose a difficulty in installing reinforcing materials and thus deteriorate the ease and efficiency with which they are constructed. This study suggests placing thick plates at the centers of the surfaces of the existing ACT-1 column and installing a binding frame (binding frames) at the central thick plates to enhance the integrity and resist lateral pressure caused by concrete casting. Finite element analysis was conducted with the variables of the number and cross-sectional size of the binding frame and the cross-sectional size of the steel tube to estimate the structural behavior of the steel tubes. Hydraulic tests were conducted to analyze load-displacement relations and identify the influence of the binding frames on the relations. The variables in the tests were the number and cross-sectional size of the binding frame, welding details, column joint and the cross-sectional size of the steel tube