• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.451-460
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• 2010

There are many types of remodeling, however, engineers and architectures preferred to merge two or more separate units to one very spacious unit. Performing this type of remodeling, in the case of wall dominant apartments, requires partial removal of structural wall causing a concern of structural integrity. However, there are insufficient studies about partial removal, that is, openings. Presently, ACI standard have no clear way to evaluate the effect of opening on the structural wall. AIJ has the provision about strength reduction factor '$\gamma$'. However, this reduction factor cannot exactly evaluate the reduction effect of openings because this factor '$\gamma$' was determined through the elastic analysis. Therefore, in this study, 2 structural wall specimens were tested and many test results from previous studies were collected. Using these data, this study performed statistical analysis about strength of structural wall which have the opening in wall panel. And this study performed parametric study verifying shear strength reducing effect by opening area. In the results of statistical study, previous reduction factor show very conservative results because this equation did not consider other factors, reinforcement ratio and aspect ratio of openings, which was affect the shear strength of shear walls. Therefore we performed parametric study based on the test data and suggest new equation for shear strength reduction factor '$\gamma$'.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.205-214
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• 2010

Masonry structures have been used throughout the world for the construction of residential buildings. However, from a structural point of view, the masonry material is characterized by a very low tensile strength. Moreover, the bearing and shear capacity of masonry walls have been found to be vulnerable to earthquakes. In this study, to improve the seismic performance of masonry walls, hexagonal blocks were developed and six masonry walls made with hexagonal block were tested to failure under reversed cyclic lateral loading. This paper focuses on an experimental investigation of different types of wall with hexagonal blocks, i.e. walls with different hexagonal blocks and with different reinforcing bar arrangements, subjected to applied cyclic loads. The cracking, damage patterns and hysteretic feature were evaluated. Results from the hexagonal masonry wall were shown more damage reduction and less brittle failure in comparison to the existing rectangular masonry walls.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.521-526
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• 2002

The seismic performance of structural walls subjected to the cyclic lateral loads are influenced by various factors, like sectional shape, aspect ratio, reinforcement ratio, arrangement of reinforcement, and axial load ratio etc. In this research, reinforced concrete structural walls with the T-shaped cross section were selected. The seismic performance of T-shaped wall was affected by the many (actors because T-shaped wall is irregular wall composed to two rectangular walls. Especially the seismic performance of T-shaped wall varies with the flange condition and the various factors including the flange condition were determined. Therefore, the objective of this study is to understand the factors to improve seismic performance of RC T-shaded tv using sectional analysis.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.177-188
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• 2006

Conventional nonlinear finite element analysis requires complicated modeling and analytical technique. Furthermore, it is difficult to interpret the analytical results presented as the stress-strain relationship. In the present study, a design-oriented analytical method using the truss model was developed. A reinforced concrete member to be analyzed was idealized by longitudinal, transverse, and diagonal line elements. Basically, each element was modeled as a composite element of concrete and re-bars. Simplified cyclic models for the concrete and re-bar elements were developed. RC beams and walls with various reinforcement details were analyzed by the proposed method. The inelastic strength, energy dissipation capacity, deformability, and failure mode predicted by the proposed method were compared with those of existing experiments. The results showed that the proposed model accurately predicted the strength and energy dissipation capacities, and to predict deformability of the members, the compression-softening model used for the concrete strut element must be improved.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.6
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• pp.55-66
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• 2011

The purpose of this study was to develop an efficient process in the design and construction of a 1:5 scale 10-story R.C. apartment building model for an earthquake simulation test. The reduction ratio of the specimen was determined by the size ($5m{\times}5m$) and pay load (600kN) of the available shaking table and the availability of model reinforcements. For efficiency and quality control of the reinforcement work, prefabrication was used. Construction was conducted in two steps, the wall in one step, and another step for the slab, because it was impossible to remove the formwork of a wall if the walls and slabs in a story were constructed in one step. The slip form construction method was used repetitively for walls. The formwork of a wall was made with veneer and acryl plate on each side, so it was possible to check the quality of the concrete placing. To construct this model, it took roughly six months with five full-time research assistants, for a total of 602 man days of labor in construction.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.35-43
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• 2009

Two types of piloti-type high-rise RC building structures having irregularity in the lower two stories were selected as prototypes, and nonlinear time history analysis was performed using OpenSees to verify the analysis technique and to investigate the seismic capacity of those buildings. One of the buildings studied had a symmetrical moment-resisting frame (BF), while the other had an infilled shear wall in only one of the exterior frames (ESW). A fiber model, consisting of concrete and reinforcing bar represented from the stress-strain relationship, was adapted and used to simulate the nonlinearity of members, and MVLEM (Multi Vertical Linear Element Model) was used to simulate the behavior of the wall. The analytical results simulate the behavior of piloti-type high-rise RC building structures well, including the stiffness and yield force of piloti stories, the rocking behavior of the upper structure and the variation of the axial stiffness of the column due to variation in loading condition. However, MVLEM has a limitation in simulating the abrupt increasing lateral stiffness of a wall, due to the torsional mode behavior of the building. The design force obtained from a nonlinear time history analysis was shown to be about $20{\sim}30%$ smaller than that obtained in the experiment. For this reason, further research is required to match the analytical results with real structures, in order to use nonlinear time history analysis in designing a piloti-type high-rise RC building.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.287-290
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• 2009

이 논문에서는 가압중수형(Pressurized Heavy Water Reactor) 프리스트레스 콘크리트 격납건물의 1/4 축소모델에 대한 극한내압능력과 전반적인 비선형거동에 관한 유한요소 해석을 수행하였다. 가압중수형 격납건물은 원통형 벽체와 돔으로 구성되었고, 4개의 부벽을 갖는다. 유한요소해석을 위해서 상용코드 ABAQUS를 이용하였고, 콘크리트, 철근 및 텐던에 대한 수치모델링을 작성하여 자중과 내압하중을 적용하였고, 텐던의 2% 변형률을 기준으로 극한내압능력을 평가하였다. 이때 사용된 재료모델로 콘크리트는 Concrete Damaged Plasticity 모델을 사용하였고, 철근과 텐던은 Elasto-Plastic 모델을 적용하였다. 유한요소 해석결과 콘크리트의 초기균열 0.41MPa에서 발생하였고, 극한내압은 0.56MPa 정도로 평가되었다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.215-222
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• 1996

원전 격납구조물의 구조해석에 대한 대부분의 연구에서 격납구조물을 축대칭으로 모델하고 있다. 따라서 격납구조물에 배근된 강재도 축대칭으로 가정하는 것이 일반 적이며, 유한요소모델 구성시 강재는 2절점 트러스나 1절점 링 트러스요소에 의해서 모델한다. 이때 유효철근비는 트러스요소의 단면적에 의해서 표현되며, 원통형 벽체에서는 높이에 따라 배근된 강재량이 일정하므로 실제와 근접한 모델이 가능하다. 그러나, 상부돔의 축대칭모델시 돔의 자오선 방향으로 규정된 강재량이 일정치 않고, 변화하게 된다. 기존에 연구에서는 이러한 강재량의 변화를 고려하지 못하고 반경방향으로 일정한 것으로 가정하여 구조해석을 수행하여 왔다. 이와같은 모델상의 제약으로 인해서 철근이나 텐던의 조기항복, 돔 정상부 부근에서의 부 정확한 변형특성을 보이고 있다. 본 연구에서는 실제 규정된 강재량을 유한요소모델에 반영하기 위해 정점부에서 자오선 방향으로 변화되는 강재량을 모델할 수 있는 기법에 대해서 연구하였으며, 연구결과를 바탕으로 격납구조물의 극한 내압해석을 수행하여 기존 모델방법에 의한 해석결과와 비교하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.411-414
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• 1999

Five reinforced concrete rigid frame and masonry infilled wall and cut off type masonry infilled wall were constructed and tesed during vertical and cycle loads simultaneously. Experimental programs were accomplished to evaluate the structural performance of test spcimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. Test variables are hoop reinforcement ratio and masonry infilled wall with on without. All the specimens were modelling in one-third scale size.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1149-1154
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• 2001

A Seismic retrofit idea based on a first principle is proposed for existing RC walls under various level of axial loading. In application of the proposed retrofit method, designers can choose the size and shape of boundary elements of wall sections for a required level of ductility. For this axial load ratio, steel ratio, and strength of concrete and steel are considered as design parameters. In order to show the usage of the idea, several design charts are presented with an application example.