• Journal of Korean Society of Steel Construction
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• v.19 no.4
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• pp.383-393
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• 2007

A simplified model which incorporates the moment-axial tension interaction of the double-span beams in a column-removed steel frame is presented in this paper. To this end, material and geometric nonlinear parametric finite element analyses were conducted for the double-span beams by changing the beam span to depth ratio and the beam size within some practical ranges. The beam span to depth ratio was shown to be the most influential factor governing the catenary action of the double-span beams. Based on the parametric analysis results, a simplified piece-wise linear model which can reasonably describe the vertical resisting force versus the beam chord rotation relationship was proposed. It was also shown that the proposed method can readily be used for the energy-based progressive collapse analysis of steel moment frames.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.2
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• pp.93-100
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• 2021

In Korea, one of the most used structural systems for residential apartment buildings is the combination of the reinforced concrete (RC) wall and rahmen structures in the upper and lower floors, respectively. To alleviate the significant difference between the stiffnesses of these two structural systems, large transfer girders are generally required in the transition zone of the structure, which then results in the use of large amounts of construction materials and low economic feasibility. This paper proposes a new RC boundary-beam-wall system that can minimize the disadvantages of the RC transfer girder system. The structural performance of the proposed system subjected to axial loading was evaluated via rigorous three-dimensional nonlinear finite element analysis. Four parameters, namely the ratio of lower wall to upper wall lengths, distance between stirrups, main bar slope ratio, and slab length, were considered in the finite element analysis, and their effects on the maximum axial load were analyzed and discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1081-1084
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• 2008

Column specimens were constructed with main parameters significantly affecting the strength of the compression lap splice, such as lap length, spacing of lapped bars, amount and location of transverse reinforcements, and concrete strength. An experimental study has been conducted with column specimens in concrete strength of 40 to 60 MPa. Diameters of lapped reinforcing bars are 22 mm. An axial load was monotonically applied to the column specimens. All specimens failed in a brittle sudden manner and cover concrete was blasted out at maximum load. Compression lap splice strengths of specimens were evaluated from strains measured at the beginning of the lap length. Effects of the main parameters on the strengths of compression lap splice are assessed. Similarly to strengths of tension lap slice, the compression splice strength is found to be affected by lap length, spacing of lapped bars, transverse reinforcements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.94-101
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• 2023

In this study, the development performance of the head bars, which is SD700, was experimentally evaluated at the RC (reinforced concrete) or SFRC (steel fiber reinforced concrete external beam-column joint. A total of 10 specimens were tested, and variables such as steel fibers, length of settlement, effective depth of the beam, and stirrups of the column were planned. As a result of the experiment, the specimens showed side-face blowout, concrete breakout, and shear failure depending on the experimental variables. In the RC series experiments with development length as a variable, it was confirmed that the development strength increased by 26.5~42.2% as the development length increased by 25-80%, which was not proportional to the development length. JD-based experiments with twice the effective depth of beams showed concrete breakout failure, reducing the maximum strength by 31.5% to 62% compared to the reference experiment. The S-series experiment, in which the spacing of the shear reinforcement around the enlarged head reinforcement was 1/2 times that of the reference experiment, increased the maximum strength by 8.4 to 9.7%. The concrete compressive strength of SFRC was evaluated to be 29.3% smaller than the concrete compressive strength of RC, but the development strength of SFRC specimens increased by 7.3% to 12.2%. Accordingly it was confirmed that the development performance of the head bar was greatly improved by reinforcing the steel fiber. Considering the results of 92% and 99% of the experimental maximum strength of the experiment arranged with 92% and 110% of the KDS-based settlement length, it is judged that the safety rate needs to be considered even more. In addition, it is required to present a design formula that considers the effective depth of the beam compared to the development length.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.1
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• pp.19-27
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• 2020

Reinforced concrete (RC) buildings built in the 1980s are vulnerable to seismic behavior because they were designed without any consideration of seismic loads. These buildings have widely spaced transverse reinforcements and a short lap splice length of longitudinal reinforcements, which makes them vulnerable to severe damage or even collapse during earthquakes. The purpose of this study is to investigate the impact of bidirectional lateral loads on RC columns with deficient reinforcement details. An experimental test was conducted for two full-scale RC column specimens. The test results of deficient RC columns revealed that bidirectional loading deteriorates the seismic capacity when compared with a column tested unidirectionally. Modeling parameters were extracted from the tested load-displacement response and compared with those proposed in performance-based design standards. The modeling parameters proposed in the standards underestimated the deformation capacity of tested specimens by nearly 50% and overestimated the strength capacity by 15 to 20%.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.140-148
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• 1994

RCI 318-8!4 recommends that when the specified cornpresslve strength of concrete In a column is greater than 1.4 times thdt spec~f~ed for a floor svsttm. top surface of the colunm concrete shall extend 2ft(600mm) into the slab from the face of colurnn to avoid unexpected brittle failure. Six test specimens were cast arid tested on 2/3 scale frame specmiens havlng different extension distances and compressive strength of concrete as the major variables. The paper discusses the performance of the frames in terms of ductility and also presents the assessment of the ACI 318-89 provisions.The test results showed that the ductility index were incrrased with increasing of compressive strength of concrete and extension distance. And top surface of the column concrete should extend 2h(h overall depth of beam) into the beam from the face of the column to avoid unexpected brittle failure in frame.

• Journal of agriculture & life science
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• v.45 no.4
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• pp.87-93
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• 2011

This study was carried out to determine more effective way in eave structure between lengthening roof just as standard plan and replacing 3 types of vertical rain roof facility by using computational fluid dynamics (CFD) simulation to reduce the heat stress of Hanwoo, increase the effect of dryness of room floor, rain proof and ventilation efficiency. The simulation which did with mean wind velocity (1.2 m/s) result showed that the case of lengthening of roof just as standard design was more effective than the cases of vertical establishment of rain proof facility.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.71-80
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• 2013

Fire-resistant (FR) test data for a square concrete-filled steel tube (CFT) columns consisting of high-strength steel (fy>650MPa) and high strength concrete (fck>100MPa) under axial loads are insufficient. The FR behavior of square high-strength CFT members was investigated experimentally for two specimens having ${\Box}-400{\times}400{\times}15{\times}3,000mm$ with two axial load cases (5,000kN and 2,500kN). The results show that the FR performance of the high-strength CFT was rapidly decreased at earlier time (much earlier at high axial load) than expected due to high strength concrete spalling and cracks. In addition, a fiber element analysis (FEA) model was proposed and used to simulate the fiber behaviour of the columns. For steel and concrete, the mechanical and thermal properties recommended in EN 1994-1-2 are adopted. Test results were compared to those of numerical analyses considering a combination of temperature and axial compression. The numerical model can reasonably predict the time-axial deformation relationship.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.1-9
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• 2015

In this paper, the RC column-based joint connection part carry out loading test by reinforced hollow or extended Base Plate in order to confirm that RC joint punching shear reinforcement effect of applying the Base Plate. Base Plate thickness, extension length, size, and type as the variable, Base Plate suitable for the stress distribution and shape and dimensions confirmed through experiment and then reinforcing effect was analyzed. Experimentally, vertical load transmitted to the Base Plate from column to foundation is effective to stress distribution and then, type of hollow reinforcement more efficient than a closed. Through experiment, improve performance and ductility due to reinforcement and relative to the thickness of the existing foundation reduced even showed better performance than the existing. The behavior of the reinforced specimens be able to induce from brittle to ductile. Experiment on loading to destroy performed the pattern of cracks, destruction aspect before and after reinforcement.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.3 s.22
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• pp.9-16
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• 2006

In structural health monitoring, the safety of structural members are assessed by the level of stress measured by various strain sensors based on different sensing mechanisms. Since most existing strain sensors used for health monitoring system can cover a relatively small range of structural members, it is very difficult to measure the maximum value of the member subjected to varying amount and types of loads with those point sensors. The reliability of assessed safety of a member may be improved by increasing the number of sensors. It may not be also realistic to increase the number of sensors to overcome these drawbacks. In this paper, a stress measuring method for beam-column members is developed by estimating the maximum stress based on the average strains obtained from long gauge sensor. The average strain from long gage fiber optic sensor is transformed into the maximum strain by multiplication of the modification factor derived in this research.