• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.737-742
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• 2017

Recently, unconventional high-rise building shapes have attracted attention as a landmark of metropolitan cities and the search for innovative building forms in architecture is ongoing. In this study, $Isotruss^{(R)}$ grid(ITG) used in smaller scale structures was applied to building structural systems and its structural performance was examined. The structural behavior of an ITG was compared with that of a diagrid structure as a reference structure. The stiffness-based design method of the diagrid system was used for the preliminary design stage of member sizing in an ITG. The structural design of 16, 32, and 48-story buildings was carried out for the two systems with the same size. The angle of the inclined columns for ITG and diagrid was $59^{\circ}$ and $68.2^{\circ}$, respectively. The lateral stiffness, steel tonnage of the exterior frame, axial strength ratio, story drift ratio, and natural frequency of the two systems were compared. Based on the analysis result of 6 buildings, the two systems had similar structural capacity; 93.3% and 88.7% of the lateral load was carried by the perimeter frame in the ITG system and diagrid system, respectively. This suggests that the ITG system is better in arranging core columns. Therefore, the proposed ITG system has not only a unique façade, but also substantial structural capacity equivalent to the existing system.

• Earthquakes and Structures
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• v.26 no.6
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• pp.417-431
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• 2024

The fundamental period of vibration is one of the most critical parameters in the analysis and design of structures, as it depends on the distribution of stiffness and mass within the structure. Therefore, building codes propose empirical equations based on the observed periods of actual buildings during seismic events and ambient vibration tests. However, despite the fact that infill walls increase the stiffness and mass of the structure, causing significant changes in the fundamental period, most of these equations do not account for the presence of infills walls in the structure. Typically, these equations are dependent on both the structural system type and building height. The different values between the empirical and analytical periods are due to the elimination of non-structural effects in the analytical methods. Therefore, the presence of non-structural elements, such as infill panels, should be carefully considered. Another critical factor influencing the fundamental period is the effect of Soil-Structure Interaction (SSI). Most seismic building design codes generally consider SSI to be beneficial to the structural system under seismic loading, as it increases the fundamental period and leads to higher damping of the system. Recent case studies and postseismic observations suggest that SSI can have detrimental effects, and neglecting its impact could lead to unsafe design, especially for structures located on soft soil. The current research focuses on investigating the effect of infill panels on the fundamental period of moment-resisting and eccentrically braced steel frames while considering the influence of soil-structure interaction. To achieve this, the effects of building height, infill wall stiffness, infill openings and soil structure interactions were studied using 3, 6, 9, 12, 15 and 18-story 3-D frames. These frames were modeled and analyzed using SeismoStruct software. The calculated values of the fundamental period were then compared with those obtained from the proposed equation in the seismic code. The results indicate that changing the number of stories and the soil type significantly affects the fundamental period of structures. Moreover, as the percentage of infill openings increases, the fundamental period of the structure increases almost linearly. Additionally, soil-structure interaction strongly affects the fundamental periods of structures, especially for more flexible soils. This effect is more pronounced when the infill wall stiffness is higher. In conclusion, new equations are proposed for predicting the fundamental periods of Moment Resisting Frame (MRF) and Eccentrically Braced Frame (EBF) buildings. These equations are functions of various parameters, including building height, modulus of elasticity, infill wall thickness, infill wall percentage, and soil types.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.381-388
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• 2010

In this study, characteristics of the seismic response of the non-earthquake resistant reinforced concrete (RC) frame were identified. The test building is designed to withstand only gravity loads and not in compliance with modern seismic codes. Smooth bars were utilized for the reinforcement. Members are provided with minimal amount of stirrups to withstand low levels of shear forces and the core concrete is virtually not confined. Columns are slender and more flexible than beams, and beam-column connections were built without stirrups. Through the modeling of an example RC frame, the feasibility of the fiber elementbased 3D nonlinear analysis method was investigated. Since the torsion is governed by the fundamental mode shape of the structure under dynamic loading, pushover analysis cannot predict torsional response accurately. Hence, dynamic response history analysis is a more appropriate analysis method to estimate the response of an asymmetric building. The latter method was shown to be accurate in representing global responses by the comparison of the analytical and experimental results. Analytical models without rigid links provided a good estimation of reduced stiffness and strength of the test structure due to bond-slip, by forming plastic hinges closer to the column ends. However, the absence of a proper model to represent the bond-slip poased the limitations on the current inelastic analysis schemes for the seismic analysis of buildings especially for those with round steel reinforcements. Thus, development of the appropriate bond-slip model is in need to achieve more accurate analysis.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.683-692
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• 2011

In piloti-type low-rise RC residential buildings, severe damages have been usually concentrated at piloti stories under the earthquake. In this study, a piloti story was retrofitted by installation of buckling-restrained braces (BRB's) to increase strength and stiffness of piloti story and by application of fiber reinforced polymer (FRP) sheet on columns to avoid the brittle shear and axial failure of columns. To verify this retrofit performance, reversed cyclic lateral load tests were performed on 1:5 scale bare and retrofitted frames. The test results showed that yield strength (43.2 kN) appeared to be significantly larger than design value (30 kN) due to the increase of strength in the compression side, but the stiffness value (11.6 kN/mm) turned out to be approximately one-half of the design value (24.2 kN/mm). The reasons for this difference in stiffness were due to slippage at joint between the frame and the BRB's, displacement and rotation at footing. The energy absorption capacity of the retrofitted frame was 7.5 times larger than that of the bare frame. The change of the number of load cells under the footing from 2 to 1 reduced lateral stiffness from 11.6 kN/mm to 6 kN/mm, which was only three times larger than that of the bare frame (2.1 kN/mm).

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.261-273
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• 2011

Recently, the demands for steel frame are increasing because of the trend and due to the demand for bigger and higher buildings. In the analysis of typical steel frame, connections are based on the idealized fixed or pinned connection. A fixed connection assumes that the relative angle of each member before deformation is the same after the transformation. Therefore, the stiffener reinforces the connection to sufficient rigidity and stability of the panel zone. In the economical aspect, however, the necessity of connection that the stiffener reinforcement has omitted is increasing due to the excessive production as well as labor costs of connection. In contrast, pinned connection is assumed that bending moments between the beams and columns do not transfer to each member. This is easy to make in the plant and the construction is simple. However, the structural efficiency is reduced in pinned connection because connection cannot transfer moments. The introduction of this semirigid process can decide efficient cross-sectional dimensions that promote ease in the course of structural erection, as performed by members in the field-a call for safety in the entire frame. Therefore, foreign countries exert efforts to study the practical behavior and the results are applied to criterion. This paper analyzes the semirigid connection of domestic steel by design specifications of AISC/LRFD and make data bank that pertain to each steel. After wards, the results are compared to those of idealized connection; at the same time, this paper presents a design method that matches economic efficiency, end-fixity, and rotational stiffness.

• KIEAE Journal
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• v.7 no.2
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• pp.39-46
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• 2007

A high-rise building construction in Korea has some problems in engineering, construction and management technologies although the high-rise building construction is recently booming. In addition, the lack of skilled construction labors is increasing, so the development for methods is needed to reduce the labors by prefabrication and mechanization. A re-bar work is one of very important works with regard to cost and schedule management in the high-rise building construction. Nevertheless, the re-bar work has some problems that it is needed many re-bars for joints linking and much time for lifting due to high-rise buildings, and it is difficult to level the skill of labors. So, in this study, the pre-fabrication of three-story height in column re-bars is proposed and the results of an implementation are analyzed and explored by a case study. As the results of case study, the pre-fabrication of three-story heights in column re-bars could reduce the cost in the re-bar work and accelerate the time in the structural frame work. In addition, the pre-fabrication of three-story height in column re-bars could solve the problems such as the waste of many re-bars for joints linking, and the lack of the skilled labors.

• Earthquakes and Structures
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• v.14 no.1
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• pp.1-10
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• 2018

Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an optimum seismic performance, in which the maximum structure capacity is used. Then the genetic algorithm which is an evolutionary optimization method is used for optimal arrangement of the steel dampers in the structure. In continuation for specifying the optimal accurate response, the local search algorithm based on the gradient concept has been selected. In this research the introduced optimization methods are used for optimal retrofitting in the moment-resisting frame with inelastic behavior and initial weakness in design. Ultimately the optimal configuration of dampers over the height of building specified and by comparing the results of the uniform deformation method with those of the genetic algorithm, the validity of the uniform deformation method in terms of accuracy, Time Speed Optimization and the simplicity of the theory have been proven.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6915-6921
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• 2014

This study examined the composition and spatial characteristics of the Illinois Institute of Technology (1939-1959) campus by Mies van der Rohe. Studies of the Mies' architecture has been focused mostly on "universal space", structural rationality for a single building. Therefore, it is interesting to study an IIT campus through which Mies composed public space dealing with several buildings together. To determine the relationships with his previous works and the design intentions for IIT campus, this paper studied his preliminary sketches, perspective drawings etc.. By doing so, the paper presents the following conclusions. First, Mies composed the IIT campus with simple linear buildings as walls to create the "flowing space" through the campus. Secondly, the IIT campus could become the "neutral frame" integrating the campus with urban space. Third, Mies also created an open, continuous public space in the center of the campus that allows protective, quiet seclusion for the students.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.52-62
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Top shear connection of the PC panel was required to show the composite strength of RC column and PC wall panel. However, the strength of the connection did not influence directly on the ultimate loading capacities of the specimens in the positive loading because the loaded RC column push the side of PC wall panel and it moved horizontally before the shear connector receive the concentrated shear force in the positive loading process. Under the positive loading sequence(push loading), the reinforced concrete column and PC panel showed flexural strength which is larger than 97% of the composite section because of the rigid binding at the top of precast panel. Similar load-deformation relationship and ultimated horizontal load capacities were shown in the test of PR1-LA and PR1-LP specimens because they have same section dimension and detail at the flexural critical section. An average of 4.7 times increase in the positive maximum loading(average 967kN) and 2.7 times increase in the negative maximum loading(average 592.5kN) had resulted from the test of seismic resistant specimens with anchored and welded steel plate connections than that of unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.0% and 1.4%.

• Journal of Korea Multimedia Society
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• v.17 no.3
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• pp.393-404
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• 2014

This research proposes a method to draw a number of components for roof frame in 3D datum. It is based on the analysis of the roof curvature and their geometric relationship in the traditional wooden buildings. Correlations between the components that generate a roof surface is defined with functional formula. The design system which automatically generates 3D datum for the components is implemented by reflecting the structural mechanics for them. The suggested system provides a control function to easily draw a traditional house. In this system, the components engaged in forming a roof surface are not only automatically generated but also simply modified according to the user's request. It would improves design efficiency and ensure a various roof surface design. Furthermore it makes possible systematic drawing and standardized industrial processing. Consequently, the proposed method is expected to contribute to the popularization of traditional house constructing.