• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.174-182
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• 2014

To monitor the wind-induced responses of buildings, conventional real-time kinematic (RTK) methods based on two global positioning system (GPS) receivers (e.g., a reference and a rover) are widely applied. However, these methods can encounter problems such as difficulty in securing and maintaining a space for a reference station. With the recently developed virtual reference station (VRS)-RTK approach, the position of a structure can be measured using only a rover receiver. In this study, to evaluate the applicability of VRS-RTK methods in monitoring the lateral structural responses of frame structures, we performed free vibration tests on a one-story frame model (the first natural frequency of 1 Hz) and a three-story frame model (the first natural frequency of 0.85 Hz). To assess the reliability of the displacement and acceleration responses measured by the GPS, we performed a concurrent measurement using laser displacement sensors and an accelerometer. The accelerometer results were consistent with the GPS measurements in terms of the time history and frequency content. Furthermore, to derive an appropriate sampling rate for the continuous monitoring of buildings, the errors in the displacement responses were evaluated at different GPS sampling rates (5, 10, 20 Hz). The results indicate that as the sampling rate increased, the errors in the displacement responses decreased. In addition, in the three-story model, all modal components (first, second, and third modes) could be recorded at a sampling rate of 20 Hz.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.118-128
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• 2012

As the bearing wall structure, which has been widely applied to domestic apartment buildings since the 1980s, cause many problems during remodeling of buildings, the government encourages constructors to adopt flat plate or rahmen structure through legal incentives. In line with such a trend, the green frame, an eco-friendly rahmen structure that has removed the shortcomings of previous structures, was developed to enhance structural safety, constructability, and eco-friendliness. The construction of green frame can reduce the labor cost and facilitate the composition of iron bars to reduce rebar loss through calculating the quality and establishing the bar bending schedule automatically on the precast concrete member data collected over the design phase. Therefore, the purpose of this study is to develop the algorithm to automate the calculation of iron bar volume for the green frame designed on composite precast concrete members. Automated algorithm to calculate concrete structural design information and design information. Practices through the application site should prove efficacy. The database established by the developed algorithm will automate the establishment of iron bar processing map and bar cutting list and the calculation of optimal composition and order volume to minimize the rebar loss. This will also reduce the expenses on management staff and overall construction cost through the minimization of rebar loss.

• Journal of the Korean Wood Science and Technology
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• v.40 no.5
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• pp.319-326
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• 2012

Han-green building is one of the modernized Korean traditional buildings developed by Korea Forest Research Institute. This building was developed to increase the competitiveness of Korean traditional building using state-of-art technologies; hence Han-green building has the inherent characteristics of traditional building such as exposed wood frame in wall. Because of discontinuity in wall by the exposed wood frame, there is a concern on heat-air leaking in terms of energy performance. In this study, air-tightness of Han-green building was evaluated to investigate the influence of gaps between frames and in-fill walls. Blower door test was carried out to evaluate the air-tightness, and air-change rate (ACH50) was evaluated by averaging four set of pressurization and depressurization test. The air-change rate of Han-green house was 5.91 $h^{-1}$. To improve energy performance of Han-green house, thermal infrared images of Han-green house were taken in winter with heating to find out where the heat loss occurred. It was found that the building lost more heat through gaps between frames and in-fill walls rather than through other parts of this building. After covering all the gaps by taping, the blower door test was performed again, and the air-change rate was improved to 5.25 $h^{-1}$. From this analysis, it was concluded that the heated air can leak through the gaps between frames and walls. Therefore, when one designs the post and beam building with exposed frame, the detail design between frame and wall needs to be carefully dealt. However, Han-green building showed relatively high air-tightness comparing with other country research results.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.727-734
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• 2005

High-rise residential buildings these days tend to adopt a building frame system as primary earthquake resisting structural system for some architectural reasons. But there exist several ambiguities in designing such building frame systems according to current codes with regards to : the effective stiffness property of RC cracked section in static and dynamic analyses, analytical model to evaluate story drift ratio, and deformation compatibility requirements of frames. The comparative study for these issues by appling KBC 2005 to a typical building frame system shows that demands of member strength and story drift ratio can be different significantly depending on engineer's Interpretation and application of code requirements. And a building frame system can be noneconomical, compared with the dual system, because of higher demands on strength or ductility in both frames and shear walls.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8C
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• pp.667-679
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• 2010

The use of femtocells in buildings and homes has been widely studied as a means to enlarge the cell coverage and increase the network capacity of mobile communication systems. Femtocells for Mobile WiMAX (M-WiMAX) using time division duplexing (TDD) requires frame synchronization with neighboring base stations to avoid interference between uplink and downlink signals. In this paper, we propose a new frame synchronization method for femtocell using IEEE 802.11 based wireless backhaul, which transfers the time information of mobile network to femtocells via the beacon signal provided by IEEE 802.11. Also, in order to reduce timing error of the proposed method, we modify the collision avoidance scheme in the transmitter of IEEE 802.11 and apply a timing estimation technique designed in the sense of least squares to the receiver of IEEE 802.11. Through computer simulations using the proposed scheme, we evaluate the performance of frame synchronization for femtocells and show that the recovered timing information satisfies the timing specification defined by M-WiMAX standard.

• International Journal of High-Rise Buildings
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• v.4 no.3
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• pp.171-180
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• 2015

A shaking table test was conducted at the E-Defense shaking table facility to investigate the damage and collapse behavior of a steel high-rise building under exceedingly large ground motions. The specimen is a one-third scale 18-story steel moment frame designed and constructed according to design specifications and practices used in the 1980s and 1990s. The shaking table tests used a long-duration, long-period ground motion simulated for a sequential Tokai, Nankai, and Nankai earthquake scenario. The building specimen was subjected to a series of progressively increasing scaled motions until it completely collapsed. The damage to the steel frame began through the yielding of beams along lower stories and column bases of the first story. After several excitations by increasing scaled motions, cracks initiated at the welded moment connections and fractures in the beam flanges spread to the lower stories. As the shear strength of each story decreased, the drifts of lower stories increased and the frame finally collapsed and settled on the supporting frame. From the test, a typical progression of collapse for a tall steel moment frame was obtained, and the hysteretic behavior of steel structural members including deterioration due to local buckling and fracture were observed. The results provide important information for further understanding and an accurate numerical simulation of collapse behavior.

• Geomechanics and Engineering
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• v.32 no.1
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• pp.69-84
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• 2023

This paper proposes a novel frame element on Winkler-Pasternak foundation for analysis of a non-ductile reinforced concrete (RC) member resting on foundation. These structural members represent flexural-shear critical members, which are commonly found in existing buildings designed and constructed with the old seismic design standards (inadequately detailed transverse reinforcement). As a result, these structures always experience shear failure or flexure-shear failure under seismic loading. To predict the characteristics of these non-ductile structures, efficient numerical models are required. Therefore, the novel frame element on Winkler-Pasternak foundation with inclusion of the shear-flexure interaction effect is developed in this study. The proposed model is derived within the framework of a displacement-based formulation and fiber section model under Timoshenko beam theory. Uniaxial nonlinear material constitutive models are employed to represent the characteristics of non-ductile RC frame and the underlying foundation. The shear-flexure interaction effect is expressed within the shear constitutive model based on the UCSD shear-strength model as demonstrated in this paper. From several features of the presented model, the proposed model is simple but able to capture several salient characteristics of the non-ductile RC frame resting on foundation, such as failure behavior, soil-structure interaction, and shear-flexure interaction. This confirms through two numerical simulations.

• Journal of the Korea Institute of Building Construction
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• v.5 no.1 s.15
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• pp.89-96
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• 2005

The increase of hish-rise residential-commercial buildings is required to cut down a term of works and the cost of construction. Reinforced concrete structures and steel framed reinforcement concrete that are commonly used have the difficulty in reducing them. Therefore, the purpose of this study is to propose a new precast concrete complex system and to analyze its economical feasibility. The economic analysis is performed through comparing the cost of a high-rise reinforced building that was already constructed with that of the new proposed precast concrete system, which is limited to structural frame work of typical floors. This study shows that the proposed precast concrete complex system is economical. Further research should be directed at including the influence of a term of works.

• Steel and Composite Structures
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• v.18 no.1
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• pp.121-134
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• 2015

This paper is to investigate the potentials of the elastic seismic design of twisted high-rise steel diagrid frame buildings in the strong wind and moderate/low seismicity regions. First, the prototypes of high-rise steel diagrid frames with architectural plans that have a twist angle of 0 (regular-shaped), 1, and 2 degrees were designed to resist wind. Then, the effects of the twist angle on the estimated quantities and structural redundancies of the diagrid frames were examined. Second, the seismic performance of the wind-designed prototype buildings under a low seismicity was evaluated. The response spectrum analysis was conducted for the service level earthquake (SLE) having 43-year return period and the maximum considered earthquake (MCE) having 2475-year return period. The evaluation resulted that the twisted high-rise steel diagrid frames resisted the service level earthquake elastically and most of their diagrid members remained elastic even under the maximum considered earthquake.

• Steel and Composite Structures
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• v.5 no.2_3
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• pp.247-258
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• 2005

This paper outlines the current steel design climate and describes some recent and unusual designs using structural steel or composite steel and concrete which have been carried out in Hong Kong and the East Asia region. Composite structural systems for very tall buildings are outlined. A case study of concept designs for one of these is presented. Two further case studies are presented: a refurbishment project where the use of steel and innovative strengthening techniques allowed an additional five stories to be built on an existing reinforced concrete frame and a monumental sculpture.