• 한국건축시공학회지
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• 제15권5호
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• pp.465-471
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• 2015

철근콘크리트 기둥에서 횡 보강근의 시공성 및 구속효과를 향상시키기 위하여 본 연구에서는 내부 크로스타이의 대체로서 V형 띠철근의 배근방법을 제시하였다. 제시된 V형 띠철근의 부착응력-미끄러짐 관계를 파악하기 위하여 콘크리트 강도 및 V형 띠철근의 절곡각도와 묻힘길이를 주요변수로 35개의 직접인발 실험체를 제작하였다. V형 띠철근의 부착강도는 절곡각도가 $60^{\circ}$ 이하에서 CEB-FIP 기준 식보다 높게 있었다. V형 띠철근의 시공성 및 부착거동을 고려하면, V형 띠철근의 최적 절곡각도 및 묻힘길이는 각각 $45^{\circ}$와 $6d_b$ 이상으로 제시될 수 있었는데, 여기서 $d_b$는 띠철근 직경이다.

• Journal of the Korean Wood Science and Technology
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• 제16권1호
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• pp.21-44
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• 1988

팔만칩 및 톱밥을 보오드에 활용(活用)하기 위한 방안(方案)의 하나로, 이들의 취약한 처리(物理) 및 기계적(機械的) 성질(性質)을 개선(改善)시키기 위하여 비목질재료(非木質材料)인 폴리프로필렌망(網)을 결체(結締)하여 보오드를 제조(製造)하였다. 보오드의 제조조건(製造條件)은 비중(比重)을 0.40, 0.55, 0.70 및 0.85의 4수준으로 하고 수지첨가율(樹脂添加率)을 8%, 10%, 12% 및 14%의 4수준으로 하였으며, 망수(網數)는 1장에서 4장으로 하여 보오드를 각각 제조(製造)하였다. 이들 보오드의 물리(物理) 및 기계적(機械的) 성질(性質)은 두께팽창율(膨脹率), 휨파괴계수(破壞係數), 휨탄성계수(彈性係數), 인장강도(引張强度), 박리저항(剝離抵抗) 및 나사못보지력(保持力) 등을 측정조사(測定調査)하고 고찰(考察)하였는데 본연구(本硏究)에서 얻은 중요한 결론(結論)은 다음과 같다. 1) 지수첨가율(指數添加率)이 증가함에 따라 두께팽창율(膨脹率)은 감소(減少)하였고, press-lam 보오드는 일반성형(一般成形)보오드 보다 낮은 값을 보여 주었다. 2) 보오드의 휨파괴계수(破壞係數) 및 탄성계수(彈性系數)는 비중(比重)이 증가하였으며 press-lam 보오 드는 일반적형(一般的形)보오드보다 높은 값을 나타내었다. 망수(網數)가 증가함에 따라 휨파괴계수(破壞係數)는 증가하였고, 수지첨가율(樹脂添加率)이 증가함에 따라서도 같은 양상이 나타났으나 휨탄성계수(彈性係數)의 경우 망수(網數)에 따른 효과(效果)는 나타나지 아니하였다. 3) 비중(比重)이 증가함에 따라 보오드의 인장강도(引張强度)는 증가하였으며, 망구성(網構成)보오드는 대조보오드보다 높은 값을 나타내었다. 또 망수(網數)가 증가함에 따라서도 인장강도(引張强度)는 증가하였으며, press-lam 보오드는 일반적형(一般的形)보오드보다 높은 인장강도치(引張强度値)를 보여 주었다. 4) 보오드의 박리저항(剝離抵抗)은 비중(比重)이 증가함에 따라 증가하였으며 망(網)을 결체(結締)한 보오드는 대조보오드 보다 모두 낮은 값을 보여 주었다. 기수매구성(奇數枚構成)보오드는 우수매구성(偶數枚構成)보오드보다 낮은 박리저항치(剝離抵抗値)를 보였다. 5) 수지첨가율(樹脂添加率) 및 비중(比重)이 증가함에 따라 나사못 보지력(保持力)은 증가하였으나, 망구성(網構成)보오드와 대조보오드사이에서의 차이는 크지 아니하였다. presslam 보오드에서 팔만칩보오드의 경우 고비중(高比重)보오드가, 톱밥보오드의 경우 저비중(低比重)보오드가 각각 대조보오드보다 높은 값을 보여 주었다.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.601-609
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• 2018

Steel bolts are used in the construction industry for a large variety of applications that range from fixing permanent installations to temporary fixtures. In the past much research has been focused on developing destructive testing techniques to estimate their pull-out load carrying capacity with very little attention to develop non-destructive techniques. In this regards the presented research work details the combined use of ultrasonic pulse velocity and Schmidt hammer tests to identify anchor bolts with faculty installation and to estimate their pull-out strength by relating it to the Schmidt hammer rebound value. From experimentation, it was observed that the load capacity of bolt depends on its embedment length, diameter, bond quality/concrete strength and alignment. Ultrasonic pulse velocity test is used to judge the quality of bond of embedded anchor bolt by relating the increase in ultrasonic pulse transit time to the presence of internal pours and cracks in the vicinity of steel bolt and the surrounding concrete. This information combined with the Schmidt hammer rebound number, R, can be used to accurately identify defective bolts which resulted in lower pull-out strength. 12 mm diameter bolts with embedment length of 70 mm and 50 mm were investigated using constant strength concrete. Pull-out load capacity versus the Schmidt hammer rebound number for each embedment length is presented.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2004년도 제5회 정기학술발표대회 논문집
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• pp.366-369
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• 2004

정보화 시대에 따라 소비자는 건설에 관한 많은 정보를 축적하게 되었고, 건설 수요는 고품질화되어 가고 있다. 이에 따라 건설업계에서도 점차 높아지는 소비자의 수준을 맞추기 위해 풀질에 더욱 많은 신경을 쓰고 있는 실정이다. 하자담보책임제도는 하자에 관해서 소비자 위주로 다루고 있고, 이 중 하자보수보증보험은 건설업자의 과도한 책임을 간과하고 있다. 이에 본 연구는 하자보수보증보험의 체계적인 문제점과 내용적인 문제점을 지적하여 그에 따른 개선 안을 제시하였다. 프로세스의 개선안은 건설업자의 금융부담을 줄일 수 있을 것이고, 요율산정의 추가 고려사항은 요율을 합리적으로 산정되도록 할 것이다.

• Geomechanics and Engineering
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• 제14권3호
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• pp.233-240
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• 2018

Pullout tests are usually employed to determine the ultimate bearing capacity of reinforced soil, and the load-displacement curve can be obtained easily. This paper presents an analytical solution for predicting the full-range mechanical behavior of a buried planar reinforcement subjected to pullout based on a bi-linear bond-slip model. The full-range behavior consists of three consecutive stages: elastic stage, elastic-plastic stage and debonding stage. For each stage, closed-form solutions for the load-displacement relationship, the interfacial slip distribution, the interfacial shear stress distribution and the axial stress distribution along the planar reinforcement were derived. The ultimate load and the effective bond length were also obtained. Then the analytical model was calibrated and validated against three pullout experimental tests. The predicted load-displacement curves as well as the internal displacement distribution are in closed agreement with test results. Moreover, a parametric study on the effect of anchorage length, reinforcement axial stiffness, interfacial shear stiffness and interfacial shear strength is also presented, providing insights into the pullout behaviour of planar reinforcements of MSE structures.

• Bulletin of the Korean Chemical Society
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• 제5권4호
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• pp.162-167
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• 1984

Equilibrium and dynamical behaviors of an n-alkane poymer (decane) in solution have been investigated by a molecuar dynamics simulation method. The polymer is assumed to be a chain of elements $(CH_2)$ interconnected by bonds having a fixed bond length and bond angle, but esch bond of the polymer is allowed to execute hindered internal rotation. The calculation explicitly considers the molecular naturer of solvent by including the intermolecular interactions between slovent-solvent molecules and chain element-solvent molecule. We present the results of calculations on (1) equilibrium properties (the solvent molecule-chain element pair correlation function, chain element-chain element pair correlation function, the mean square end-to-end distance and the mean square radius of gyration of the polymer) and (2) dynamic properties (four different autocorrelation functions, namely, the autocorrelation functions for the end-to-end distance and the radius of gyration, and the velocity autocorrelation functions for the center of mass and the end point of the chain). We found that the physical properties of the polymer chain depends sensitively on temperature. Comparison of the present work with other authors' results is also presented.

• 센서학회지
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• 제30권6호
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• pp.357-363
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• 2021

We developed a chemiresistive anion sensor using highly conductive carbon nanotube fibers (CNTFs) functionalized with anion receptors. Mechanically robust CNTFs were prepared via wet-spinning utilizing the nematic liquid crystal properties of CNTs in chlorosulfonic acid (CSA). For anion detection, polymeric receptors composed of dual-hydrogen bond donors, including thiourea 1, squaramide 2, and croconamide 3, were prepared and bonded non-covalently on the surface of the CNTFs. The binding affinities of the anion receptors were studied using UV-vis titrations. The results revealed that squaramide 2 exhibited the highest binding affinity toward AcO^-, followed by thiourea 1 and croconamide 3. This trend was consistent with the chemiresistive sensing responses toward AcO^- using functional CNTFs. Selective anion sensing properties were observed that CNTFs functionalized with squaramide 2 exhibited a response of 1.08% toward 33.33 mM AcO^-, while negligible responses (<0.1%) were observed for other anions such as Cl^-, Br^-, and NO₃^-. The improved response was attributed to the internal charge transfer of dual-hydrogen bond donors owing to the deprotonation of the receptor upon the addition of AcO^-.

• Journal of the Korean Wood Science and Technology
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• 제20권2호
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• pp.9-22
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• 1992

The aim of this research was to investigate physical and mechanical properties of various composition panels, each fabricated with a ratio of fiber to particle of 2 to 10. Type A consisted of fiber-faces and particle-core in layered-mat system. Type B consisted of fiberboard-faces on particleboard-core. Type C consisted of fibers and particles in mixed-mat system. The results obtained from tests of bending strength, internal bond, screw holding strength and stability were as follows: 1. The bending strength and internal bonding of both the Type A panel and the Type B panel were higher than those of the Type C panel and three-layered particle board. 2. The mechanical properties of the Type C panel showed the lowest values of all composition methods. It seems that the different compression ratios of the particle and fiber interrupted the densification of the fibers when hot pressed. 3. The dimensional stability of layered-mat system panels consising of fiber-faces and particle-core was better the than control particleboard. 4. In composition methods of particle and fiber, layered-composition method was more resonable than mixed-composition. The Type B panel had the highest mechanical properties of all the composition types. 5. The Type A panel was considered the ideal composition method because of its resistance to delamination between the particle-layer and the fiber-layer and because of its lower adhesive content and more effective manufa cturing process.

• 펄프종이기술
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• 제33권1호
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• pp.38-44
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• 2001

The effects of refining load on the paper properties were investigated. HwBKP, SwBKP and SwUKP were refined with PFI mill at the load of 3.33 N/mm and 6.00 N/mm. Higher Scott bond was obtained at the higher refining load for three pulp used in this study. However any changes in the light scattering coefficient with the change of refining load were not observed. Although the effect of refining load on the formation index for SwUKP was not observed, higher refining load gave the better formation for HwBKP and SwBKP. The fiber mass and fiber crowding factor were not affected by the refining load. Higher apparent density and tensile index were obtained with the higher refining load. However, the higher refining load did not improve the tensile index at the same apparent density. The tear index was decreased with the increase of refining load.

• Bulletin of the Korean Chemical Society
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• 제13권1호
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• pp.59-64
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• 1992

The contrasting behaviour of meso-and d,l-$D_3$-trishomocubylidene-$D_3$-trishomocubane (1 and 2) in the electrophilic addition reaction, the former giving rearranged spiro compound (1a and 1b) and the latter giving 1,2-adduct (2a and 2b), has been explained as arising from the secondary steric effects based on computational evidence. As the degree of out-of-plane deformation of the olefinic carbon atoms increases with reaction progress, the resulting internal congestion in the region behind the double bond becomes unbearably large in meso-1. The absence of symmetry plane across the double bond of d,l-2 helps for the closing fragments to adjust themselves.