• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.3
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• pp.261-269
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• 2004

The existing concrete beams can be retrofitted or reinforced by attaching carbon fiber or glass fiber sheet beneath the beams. Although diverse design methods and application techniques of the retrofitting are studied and developed, the testing method of examining retrofitted beams have not been put into practice yet. In this study, a bond delamination has been modeled and studied to provide a basis for the development of actual testing equipments. For this purpose, Gaussian and sinusoidal waves with 3GHz and 5GHz center frequency are used as an incident wave and 1mm and 3mm bond delamination under the reinforcement are modeled. In the modeling, Finite Difference-Time Domain algorithm is used to investigate the behavior of electromagnetic waves in concrete. The results have shown that 5GHz waves are suitable for the detection of delamination.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.55-65
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• 2010

The purpose of this experimental study is to evaluate the seismic performance of a 2 story RC shear wall system by the static reversal loading test. The lower 2 stories of the prototype structure were selected, and the specimens of this study were comprised of a T-type wall with an opening. The specimens were reduced to about 60% of the full scale size and were constructed to measure the result of the experimental variable regarding the existence of a lintel beam. To perform this study, the static repeated loading test was performed. According to the existence or absence of a lintel beam, the structural capacities and behavioral differences of the shear wall system were compared. The test results of this study showed that the specimen with a lintel beam underwent the seismic performance with an ultimate strength and ductility capacity better than the specimen without a lintel beam.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.205-213
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• 2003

The primary purpose of this study is to investigate punching shear capacity of flat plate slab using high strength concrete in column. It may be much contributed to economy efficiency and structural advantages that High Strength Concrete(HSC) used for vertical member and Normal Strength Concrete(NSC) for horizontal member. Therefore, six plate flat slab specimens with HSC column and NSC slab had been made and tested with real scale. The major variables were compressive strength of concrete(fck=285, $460kgf/cm^2$), extended length of HSC from column face and amount of shear reinforcements. As the result of this test, the maximum load and punching shear capacity of specimens is affected by extended length and shear reinforcements.

• Journal of the Daesoon Academy of Sciences
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• v.22
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• pp.133-275
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• 2014

『옥추보경』(玉樞寶經)은 송대의 유명한 도교 경전으로 정식 명칭은 『구천응원뇌성보화천존설옥추보경』(九天應元雷聲普化天尊說玉樞寶經)이다. 송·원시대 이후 『옥추보경』은 중국 각 지역에 광범위하게 전해지면서 많은 영향을 끼쳤으며, 명나라의 세종(世宗)과 신종(神宗)은 『옥추보경』을 새로 간행하여 직접 서문을 쓰고 동시에 매우 숭앙하였다. 『옥추보경』의 집주본이 조선에 전해진 시기는 대략 명대 시기로 보고 있으며, 조선시대에 전해졌던 『옥추보경』 집주본은 융경(隆慶) 4년(1570)에 전라도 무등산(無等山) 안심사(安心寺)에서 최초로 발간되었다. 그러나 당시 안심사 판본은 첫 페이지와 경문 중의 또 다른 페이지가 없는 불완전한 판본이었다. 옹정(擁正) 11년(1733)에 송몽삼(宋夢三), 서두추(徐斗樞) 등의 제안에 따라 영변(寧邊) 묘향산(妙香山) 보현사(普賢寺)에서 『옥추보경』을 새로 간행하게 되었다. 하지만 이 또한 불완전한 판본이었으며, 병진년(1736)에 잃어버린 두 페이지를 우연히 찾게 되면서 완전한 판본을 이루게 되었다. 이후 광서(光緖) 무자년(1888)에 김흡(金潝)이 『옥추보경』을 새로 교정하였고, 계룡산(鷄龍山)에서 이를 다시 간행하였다. 명대의 『도장』에 수록된 『옥추보경』 집주본에는 신장도(神將圖)가 포함되어 있지 않았다. 하지만 조선시대 세 종류의 판본은 모두 신장도(神將圖)가 포함되어 있다. 이 외에도 조선시대 간행본과 비슷한 판본으로 영국의 대영도서관 소장본과 일본 천리대학(天理大學) 도서관의 소장본 및 중국 국가 도서관 고적관의 소장본이 있다. 그런데 안심사 판본은 41명, 보현사 판본은 47명, 계룡산 판본은 48명의 신장도가 포함되어 있으며, 대영도서관은 45명, 중국 국가 도서관은 45명 등으로 차이가 있다. 이러한 판본들에 수록된 신상의 수가 다른 이유는 아직 명확하지 않다. 이에 본문에서 필자는 먼저 계룡산 판본 『옥추보경』에 근거하여 48신장의 내력에 대한 초보적인 고찰을 진행하였다. 언어상의 문제로 『옥추보경』과 관련된 한국의 연구 성과를 반영하지는 못했지만, 『옥추보경』의 48장과 대순진리회의 『전경』에 등장하는 48장이 어떠한 연관이 있는지를 조명하는 데 유의미한 기초 작업이 될 것으로 전망한다. 이를 토대로 나아가 대순진리회의 48신상도와 『옥추보경』의 판본간의 형태적 특징에 주목하여 면밀한 상호 분석을 시도함으로써 대순진리회의 신앙체계와 『옥추보경』의 관련성을 규명하는 데 일조할 수 있기를 기대한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.129-137
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• 2020

In designing a high strength bolted beam splice using steel for building structures, it is necessary to present the appropriate steel grade selection criteria for how to determine the cover plate steel grade. This study examined the difference in tensile behavior according to the steel grades through static tensile tests simulating the beam member high strength bolt joints flange. For this purpose, the specimens were designed and fabricated with the main variables, such as the thickness, steel grade and the strength of flange and cover plate, which are expected to affect the splice strength and behavior. The tensile test results for a total of 48 specimens showed that the tensile-load capacity exceeded the design tensile strength applied with a nominal strength of steel in all specimens. When the design strength of the cover plate exceeded 1.25 times that of the flange plate, the flange plate governed the behavior of splice. The change in maximum tensile load due to the change in flange steel grade is not very large, but there is a difference in deformation. The test results confirmed that the steel grade and thickness of the cover plate were the main factors affecting the beam splice behavior.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.719-727
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• 2009

The requirements of the maximum shear reinforcement in the EC2-02 and CSA-04, which are developed based on the truss model, are quite different to those in the ACI-08 code and AIJ-99 code, which are empirical equations. The ACI 318-08, CSA-04, and EC2-02 codes provide an expression for the maximum amount of shear reinforcement ratio as a function of the concrete compressive strength, but Japanese code does not take the influence of the concrete compressive strength into account. For high strength concrete, the maximum amount of shear reinforcement calculated by the EC2-02 and CSA-04 is much greater than that calculated by the ACI 318-08. Ten RC beams having various shear reinforcement ratios were tested and their corresponding shear stress-shear strain curves and failure modes were compared to the predicted ones obtained by the current design codes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.303-314
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• 2010

A study for the nonlinear analysis method of prestressed concrete(PSC) girders with external tendons is presented. The PSC girders with external tendons show the complex nonlinear behavior due to the slip of external tendons at deviator and the change of eccentricity between the girders and external tendons. The external tendon between anchorage-deviator or deviator-deviator is modeled as an assemblage of the curved elements. The slip effect of the external tendon at deviator is taken into account using the force equilibrium relationship between the friction force and the driving force at each deviator. The finite element model and analysis method of the external tendon suggested herein are integrated in the nonlinear analysis program of segmentally erected PSC frames developed by the authors. The proposed analysis method is verified through the comparison of the analysis and experimental results obtained from other investigators. From the ultimate analysis results of PSC beams with external tendons having different number of deviators, the yielding and ultimate loads of PSC beams found to be increased as the number of deviators are increased. In addition, the ultimate capacity of the PSC beam increases according to the increase of friction coefficient between deviator and external tendon, whereas found to decease over the certain value of friction due to the effect of the moment transmitted to the member by the friction force exerted from the external tendon.

• Journal of the Korean Wood Science and Technology
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• v.29 no.4
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• pp.1-8
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• 2001

This study was carried out to investigate the strength and stiffness of drift pinned and bolted joints with steel-plates by the tension-type lateral strength tests. Specimens were solid wood of Pinus densiflora. Bolt and drift pin were jointed with inserted steel plates. Tests were conducted with combinations of two loading directions (parallel to the grain : 0 degree, perpendicular to the grain : 90 degree) and three diameters of fasteners (d = 6 mm, 10 mm, 12 mm). The results obtained were as follow: 1. In the test of the parallel to the grain, maximum loads were increased with increasing of the diameter of bolt and drift pin in the same end distance. In the test of perpendicular to the grain with diameter 10 mm and 12 mm, specimens mostly were failed with horizontal splits in woods reaching the yield load of drift pinned and bolted joints. 2. The ratio of maximum load to the yield load determined by the so-called "5% offset method", was great in bolted joints in the parallel to the grain This trend become more remarkable as the slenderness ratio was increased. 3. The calculated yield strength was agreed well with the experimental results of drift pinned joint(0 degree).

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.93-101
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• 2010

When doing underground excavation works for the purpose of constructing large underground structures for a building in the limited space in downtown area, the stability of the adjacent ground must be top priority, and to accomplish this, it is essential to review the retaining wall construction carefully. H-Pile, which has been mainly used as a stress-carrying material in temporary earth-retaining structures, is most likely to be abandoned after completion of the works for the basement exterior wall in relation to contiguous bored piles, so it will result in a waste of material. To improve this situation, Basement Composite Wall where H-Pile and basement wall are compounded, has been developed. This wall is being used most frequently in many local construction sites. In this study, five specimens are made in order to evaluate the shear resistance of the basement composite wall and tested. Test parameter is the composition ratio and wall thickness according to shear connectors. Test result shows that the shear strength is improved when the composite ratio is increased but the magnitude is not much. A formula, which considers the contribution of concrete, web of H-pile as well as flange' effect in calculation of shear strength of composite basement wall, is suggested and used to calculation of the strength of specimens. It is found that there is a good co-relation between test result and the calculated one by the formula.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.311-318
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• 2018

When reinforced concrete structures are exposed to fire, their mechanical properties such as compressive strength, elasticity coefficient and rebar yield strength, are degraded. Therefore, the structure's damage assessment is essential in determining whether to dismantle or augment the structure after a fire. In this study, the confinement effect of lateral reinforcement of RC column according to the numbers of fire exposure face and stirrup was verified by fire resistant test with the heating temperatures of $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$. The test results showed that the peak stress decreases and peak strain increases as the temperature is getting higher, also transverse ties are helpful in improving the compressive resistance of concrete subjected to high temperature. Based on the results of this study, the residual stress of confined concrete under thermal damage is higher at the condition of more lateral reinforcement ratio and less fire exposure faces. The decreasing ratio of elastic modulus of more confined and less exposure faces from the relationship of load and displacement was also smaller than that of opposite conditions.