When reinforcing an existing reinforced concrete beam-column building with a precast concrete panel, special connection between the PC member and the RC member is required to solve the time dependent deformation of the RC member and to receive the large shear forces. The aim of this study is to obtain the shear strength of upper connection between the existing RC beam-column and infilled PC wall panels in experimentally and theoretically. Thus, the static shear loading tests were conducted on the 6 specimens with the plate connection. Shear failure was resulted from the weakest portion of interior PC panel, exterior RC, and the connection, when the PC portion which located at the center of specimen was pulled upward from the bottom. T he experimental result was compared with analytical result from ACI 318M-14 Chapter 17 for the shear strength of post-installed anchor and PCI Handbook 7th edition 6.8 Structural Steel Corbel (PCI Design Handbook 7th edition, 2010) for the strength of cast-in H-beam. The analytical and experimental results show final failure at the same location. The failure loading of experiment showed larger than average 6% to that of the analysis.

Nonlinear analysis for seismic performance evaluation of existing building usually takes 4~5 times more than linear analysis based on KBC code. To obtain accurate results from the nonlinear analysis, there are a lot of things to be considered for nonlinear analysis modeling. For example, reinforcing layout, applied load and seismic details affect behavior of structural members for the existing building. Engineer-oriented computerized system was developed for engineers to evaluate effective seismic performance of existing buildings with abiding by seismic design principles. Using the engineer-oriented program, seismic performance evaluation of reinforced concrete building was performed. Nonlinear hinge properties were applied with real time multiple consideration such as section layout, section analysis result, applied load and performance levels. As a result, the building was evaluated to satisfy LS(Life Safety) performance level. A comparison between engineer-oriented and program-oriented results is presented to show how important the role of structural engineer is for seismic performance evaluation of existing buildings.

Many studies are conducted in several fields for fragility analysis of structures or elements which is a probabilistic seismic safety analysis in consideration with uncertainty of seismic loading. It is hard to directly conduct fragility analysis for an infrastructure with social importance due to its size. Therefore, a fragility analysis for an infrastructure mainly conducted in element level or conducted with scaled model built in accordance with similarity law. In this article, fragility analysis for prototype and scaled model of reinforced concrete column was conducted with numerical models which had been updated by the results of shaking table test and pseudo dynamic test. As a result, response stress from the numerical analysis result of prototype model was higher than that from scaled model due to different stiffness ratios between steel and concrete. However, the probability of failure for scaled model was higher than that for prototype model because failure criteria for scaled model was down due to similarity law. Also it was evaluated that probability of failure by using log normal standard deviation of response stresses by spectrum matched accelerograms was more reliable than probability of failure by using existing coefficient of variation normally used.

본 논문에서는 반응표면법과 다목적최적화 기법을 이용한 유한요소모델개선기법의 절차를 제안하고 이를 저층의 철근콘 크리트건물의 모델개선에 적용하였다. 대상건물은 전단벽 신설 및 댐퍼부착을 위한 부재의 강재보강을 통해 내진보강이 이 루어진 건물로서 보강전후에 소형 가진기를 이용한 진동실험을 실시하여 동특성을 구하였다. 대상건물의 개선에 사용된 변 수는 기존콘크리트, 신규타설된 콘크리트, 조적의 탄성계수, 신축줄눈부의 스프링계수, 강재보강된 부재의 유효강성비이다. 보강전후 건물의 초기모델을 구축한 후 중심합성법에 따라 개선변수의 값을 변화시키면서 얻은 해석결과를 통해 고유진동 수의 오차와 모드형상의 오차를 나타내는 2개의 반응함수를 구하고, 이를 다목적최적화의 목적함수로 사용하였다

This study investigates the seismic performance of solid reinforced concrete columns with triangular reinforcement details using nonlinear seismic analysis. The developed reinforcement details are economically feasible and rational, and facilitate shorter construction periods. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. Solution of the equations of motion is obtained by numerical integration using Hilber-Hughes-Taylor (HHT) algorithm. The proposed numerical method gives a realistic prediction of seismic performance throughout the input ground motions for several column specimens. As a result, developed triangular reinforcement details were designed to be superior to the existing reinforcement details in terms of required performance.

In this study, nonlinear finite element analysis based on the Modified Compression Field Theory has been conducted to evaluate shear strength of RC walls with opening. On the analysis, reinforcement ratio within development length of rebars nearby the opening was reduced in the model in order to investigate the effect of opening on shear strength of RC shear walls. The nonlinear finite element analysis has been verified through comparison with the test result in literature. Through the verification, it was investigated that the analysis considering the development length of rebars well reflected the effect of an opening on shear strength of RC shear walls while current design provisions did not reasonably consider one.

This research describes the impact of vertical earthquake components on the performance of typical non-ductile bridges. To achieve this goal, this research chooses a non-seismically designed reinforced concrete bridge typically found in the California area. Particularly, their columns with inadequate design have a higher possibility of shear failure. To consider this failure, the column model reflects shear-axial interaction effect and is verified by comparing simulated results and experimental data available in literature. Two computational bridge models having column shear model subjected to constant and varying axial load are then built to conduct inelastic dynamic analyses. The responses are employed to construct probabilistic seismic demand models for two bridge models. This results indicate that the consideration of shear-axial interaction effect increases the seismic demand of all bridge components in non-ductile bridges, resulting in their increased seismic vulnerability.

This report offers an economically reasonable seismic reinforcement to non-seismic mid/low reinforced concrete structures. Installed a slit in between the reinforced concrete frame and masonry infilled wall then inserted twist bar to prevent inversion and attached to the lower/upper beam. Confirmed the seismic reinforcement effect through static loading test. Total of 4 specimens were produced for the test, a masonry infilled wall without seismic reinforcement and with seismic slit or twist bar applied. As a result, applying the seismic slit and twisted bar was economically reasonable and seismic reinforcement effect was confirmed by showing stable failure, increase of maximum strength and yield displacement, increase of accumulated energy dissipation.

본 연구에서는 철근콘크리트 건물에 대한 유전자 알고리즘 기반의 최적구조설계기법을 제시하고자 한다. 목적함수는 구조 물의 비용과 이산화탄소 배출량을 동시에 각각 최소화하는 것이다. 비용 및 인산화탄소 배출량은 구조설계안에서 얻을 수 있는 단면치수, 부재길이, 재료강도, 철근량 등과 같은 설계정보를 통해 계산한다. 즉, 구조물의 물량을 기초로 하여 비용과 이산화탄소 배출량을 평가한다. 재료의 운반, 시공 및 건물 운영 단계에서 발생하는 비용 및 이산화탄소 배출량은 본 연구에 서 제외한다. 제약조건은 철근콘크리트 건물을 구성하는 기둥과 보 부재의 강도조건과 층간변위조건이 고려된다. 제약조건 을 평가하기 위해 OpenSees를 활용한 선형정적해석이 수행된다. 제약조건을 만족시키면서 목적함수에 대해 최소의 값을 제 시하는 설계안을 찾기 위해 유전자 알고리즘이 사용된다. 제시한 알고리즘의 적용성을 검증하기 위해 4층 철근콘크리트 모 멘트 골조 예제에 제시하는 기법을 적용하여 검증한다.

Reinforced concrete shear walls with deficient reinforcement details are tested under cyclic loading. The deficiency of reinforcement details includes insufficient splice length in U-stirrups at the ends of horizontal reinforcement and boundary column dowel bars found in existing low- to mid-rise Korean buildings designed non-seismically. Three test specimens have rectangular, babel and flanged sections, respectively. Flexure- and shear-controlled models for reinforced concrete shear walls specified in ASCE/SEI 41-13 are compared with the flexural and shear components of force-displacement relation extracted separately from the top displacement of the specimen based on the displacement data measured at diverse locations. Modification of the shear wall models in ASCE/SEI 41-13 is proposed in order to account for the effect of bar slip, cracking loads in flexure and shear. The proposed modification shows better approximation of the test results compared to the original models.

Piloti-type building is one of typical vertical atypical buildings. These buildings can fail by weak-story or flexible-story mechanism on the first story. They should be designed by taking into account the special seismic load, but those less than six stories are not required to confirm the seismic performance from structural engineers in Korea. For this reason, small-size pilloti-type RC buildings need to be checked for seismic performance. Based on this background, this study performed nonlinear dynamic analysis using the PERFORM-3D for small-size pilloti-type RC buildings and assessed their seismic performance. Examples are two through four story buildings with and without walls in the first story. The walls and columns in the first story satisfied the target performance in the basic of flexural behavior due to quite a large size and reinforcement. However, wall shear demands exceed shear strength in some buildings. When designed for KBC2009, wall shear strength exceed shear demand in some buildings, but still does not in others. Consequently, wall shear must be carefully checked in both existing and new small-size pilloti-type RC buildings.

Behavior of RC(Reinforced-concrete) beam-column connections has been subjected to the earthquake loading has been determined by shear and attachment mechanism. However, since the shear and attachment are very fragile for cycle loadings. Through occurring plastic hinges at the beam, the column and the connection should remain elastic condition and the beam should dissipate the energy from the earthquake. This study was investigate on the seismic performance of 6 RC beam - column connections built with the high strength reinforcements (700MPa) based on design and detailing requirements in the ACI 318-05 Provision and KCI-07 appendix Ⅱ. This is aimed to evaluate the effect of the high-strength reinforcements as used the beam-column connection members. The main comparisons were the seismic performance of the connections affect the seismic performance in terms of strength, stiffness and ductility, joint shear stress-strain. A total of 6 beam-column specimens were built with a 1/2 scale and subjected to the cyclic loadings. Main design considerations were the area of the longitudinal reinforcements of the beam and details of the beam-column joint designed based on the seismic code. Cyclic test results are given and recommendations for the usage of high strength reinforcements for the seismic design is provided.

PURPOSES : The purpose of this study is to investigate characteristics of crack spacing and crack width and their relationship in continuously reinforced concrete pavement (CRCP) based on the data obtained from long-term field observations. METHODS: The crack spacings and crack widths are measured periodically over 10 years at two different CRCP sections: one with asphalt bond breaker beneath concrete slab, and the other with bonded lean concrete base beneath concrete slab. The effects of steel ratio, type of underlying layer, terminal treatment method, and seasonal temperature change on the crack characteristics are evaluated by analyzing the measured data. RESULTS: The CRCP with lean concrete base shows smaller crack spacings than those of the CRCP with asphalt bond breaker. As the steel ratio increases, both the crack spacing and crack width tend to decrease. The crack width becomes larger as the crack age increases, but once the crack age is over a certain value the crack width tends to converge. When the terminal anchor lug system is not used and the expansion joints are employed at the terminals, the crack spacings and crack widths increase near the terminal sections. The crack spacing and crack width seem to be proportional each other, but not necessarily linearly, and their relationship is more distinguished in the summer when the crack widths become smaller. CONCLUSIONS : The steel ratio, underlying layer type, terminal treatment method, and seasonal temperature change affect the characteristics of cracks and the crack spacing and crack width are related to each other.

연속철근 콘크리트 포장(CRCP)은 별도의 줄눈을 설치하지 않고, 온도변화에 의한 슬래브의 자연적인 균열 발생을 허용하는 포장 형식이다. 이러한 CRCP는 연속적으로 철근이 배근되기 때문에 철근 설치에 따른 초기 시공비용이 높고, 균열이 균일하게 발생하지 않을 경우 균열간격이 넓은 곳에서는 균열폭이 과 대하여 균열보수가 필요하며 균열간격이 너무 좁은 곳에서는 펀치아웃, 팝아웃 등의 파손이 발생할 수 있 다는 단점이 있다. 따라서 본 연구에서는 균열의 불규칙적인 발생으로 인한 문제점과 과다한 철근사용으 로 인한 초기시공비용이 크다는 단점을 해결하기 위한 새로운 콘크리트 포장 공법을 개발하고자 하였다. CRCP는 균열간격이 넓은 시공 초기 환경하중에 의하여 그림 1(a)와 같이 중앙부 콘크리트와 균열부 철 근의 인장응력이 높게 발생하게 된다. CRCP의 균열은 콘크리트 인장강도보다 슬래브 인장응력이 더 큰 경우 그림 1(b)와 같이 균열이 발생하게 되며, 어느 곳에서 균열이 발생할지 모를 균열의 벌어짐을 구속하 기 위하여 연속적으로 철근이 설치된다. 하지만 철근은 균열의 벌어짐을 구속하기 위한 목적으로 설치되 기 때문에 균열부를 제외한 슬래브 중앙부에는 응력이 작게 발생한다. 즉, 균열과 균열사이에는 철근의 영향이 크지 않기 때문에 그림 1(c)와 같이 원하는 위치에 균열을 유도하고, 이러한 균열부를 보강하더라 도 기존의 CRCP와 동일한 응력이 발생하게 된다. 따라서 본 연구에서는 기존의 CRCP가 균열 간에 있어 연속철근의 역할이 크지 않음에 착안하여 그림 3과 같이 균열유도를 통하여 균열을 유도시키고 이렇게 균열이 유도될 부분에만 부분철근이 배근되도록 하는 신개념 연속철근 콘크리트 포장 공법을 개발하였다.

일반적인 콘크리트 구조물은 길이가 길 경우 수축에 의한 인장균열의 발생을 억제하기 위하여 수축줄 눈을 설치된다. 하지만 연속철근 콘크리트 구조물은 별도의 수축줄눈을 설치하지 않고 그 대신 자연적으 로 발생하는 횡방향 균열을 허용하며 이러한 횡방향 균열의 과도한 벌어짐을 구속하기 위하여 연속철근이 설치된다. 대표적인 연속철근 콘크리트 구조물은 도로포장에 사용되고 있는 연속철근 콘크리트 포장 (CRCP)와 연속철근 콘크리트 궤도(CRCT)가 있다. CRCP의 횡방향 균열은 대략 0.8 - 1.5m 간격으로 발 생하며, CRCT는 레일을 지지하기 위한 프리캐스트 침목이 슬래브 내에 설치되기 때문에 침목과 슬래브 의 분리에 의하여 0.325m마다 균열이 발생하게 된다. 본 연구에서는 현장실험을 통하여 CRCP와 CRCT의 균열폭 거동을 각각 계측하고 이에 대한 분석 및 비교를 수행하였다. 그림 1~4는 CRCP와 CRCT의 슬래브 깊이에 따른 온도와 균열폭을 나타내었다. 분석 결과 균열간격이 상대적으로 작은 CRCT의 거동이 CRCP의 균열폭의 거동과 비교하여 큰 차이가 발생하 지 않는 것으로 나타나 균열간격에 비례하여 균열폭이 거동하지 않음을 알 수 있다.