• 한국강구조학회 논문집
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• 제14권2호
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• pp.357-364
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• 2002

스터드, 조이스트 및 지붕 트러스에 적용하기 위한 폐단면 냉간성형부재의 휨실험을 수행하고 해석치와 비교하여 보았다. 길이 2.4m, 폭 0.9m의 휨 시편은 46cm 간격의 두 개의 강재보의 한면에 석고보드와 합판을 부착한 시편과 부착하지 않은 시편으로 구성되었고, 각 시편에 대한 정, 부모멘트실험을 수행하여, 강재보에 부착된 합판 및 석고보드가 강재의 좌굴거동에 미치는 영향을 포함한 합성거동을 파악하였다. 또한 합판이 부착된 실물 트러스 실험을 통하여 트러스 부재의 좌굴거동 및 파괴양상에 대하여 연구하였다.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.50.1-50.8
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• 2021

Although several techniques have been proposed to remove fiber-reinforced composite (FRC) post, no safe and efficient technique has been established. Recently, a guided endodontics technique has been introduced in cases of pulp canal obliteration. This study describes 2 cases of FRC post removal from maxillary anterior teeth using this guided endodontics technique with a dental operating microscope. Optically scanned data set from plaster cast model was superimposed with the data set of cone-beam computed tomography. By implant planning software, the path of a guide drill was selected. Based on them, a customized stent was fabricated and utilized to remove the FRC post. Employing guided endodontics, the FRC post was removed quickly and safely with minimizing the loss of the remaining tooth structure. The guided endodontics was a useful option for FRC post removal.

• Restorative Dentistry and Endodontics
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• 제8권1호
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• pp.97-106
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• 1982

The purpose of this study was to evaluate the effect of different polishing procedures on the surfaces of composite resins. Two-paste type comosite restorative resin (Hipol) was selected for this study. 70 cavities prepared on the plaster-stone dies, 6mm in diameter and 2mm in depth, was filled with composite resin according to the manufacturer's specifications and by polymerizing against mylar strips. The polymerized composite resin specimens were polished (surface finished) by using 6 polishing devices; white stones, diamond finishing points, 12-fluted carbide finishing burs, green stones, sand paper disks, and Quasite rubber disk after polished with sand paper disks and green stones. A profilometer (Bendix type) was used to record in microinches the surface roughness of each surface finished composite resin specimens. The results were as follows. 1. The best finished surface that can be obtained is a surface formed by the mylar matrix strip 2. The white stones produced the smoothest surface in the experimental group. 3. The green stones produced the roughest surface in the experimental group. 4. It was proved that the gradual use of finishing instruments from a rough one to fine ones reduced the surface roughness.

• Carbon letters
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• 제15권1호
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• pp.25-31
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• 2014

A microstructure analysis is carried out to optimize the process parameters of a randomly oriented discrete length hybrid carbon fiber reinforced carbon matrix composite. The composite is fabricated by moulding of a slurry into a preform, followed by hot-pressing and carbonization. Heating rates of 0.1, 0.2, 0.3, 0.5, 1, and $3.3^{\circ}C/min$ and pressures of 5, 10, 15, and 20 MPa are applied during hot-pressing. Matrix precursor to reinforcement weight ratios of 70:30, 50:50, and 30:70 are also considered. A microstructure analysis of the carbon/carbon compacts is performed for each variant. Higher heating rates give bloated compacts whereas low heating rates give bloating-free, fine microstructure compacts. The compacts fabricated at higher pressure have displayed side oozing of molten pitch and discrete length carbon fibers. The microstructure of the compacts fabricated at low pressure shows a lack of densification. The compacts with low matrix precursor to reinforcement weight ratios have insufficient bonding agent to bind the reinforcement whereas the higher matrix precursor to reinforcement weight ratio results in a plaster-like structure. Based on the microstructure analysis, a heating rate of $0.2^{\circ}C/min$, pressure of 15 MPa, and a matrix precursor to reinforcement ratio of 50:50 are found to be optimum w.r.t attaining bloating-free densification and processing time.

• Earthquakes and Structures
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• 제11권5호
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• pp.887-904
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• 2016

An efficient, economical and practical strengthening method for hollow brick infill walls was proposed and investigated in the present study, experimentally and numerically. This method aims at increasing the overall lateral strength and stiffness of the structure by increasing the contribution of the infill walls and providing the non-bearing components of the structure with the capability of absorbing earthquake-induced energy to minimize structural damage during seismic excitations. A total of eleven full-scale infill walls strengthened with expanded mild steel plates were tested under diagonal monotonic loading to simulate the loading condition of the non-bearing walls during an earthquake. The contact surface between the plates and the wall was increased with the help of plaster. Thickness of the plates bonded to both faces of the wall and the spacing of the bolts were adopted as test parameters. The experiments indicated that the plates were able to carry a major portion of the tensile stresses induced by the diagonal loads and provided the walls walls with a considerable confining effect. The composite action attained by the plates and the wall until yielding of the bolts increased the load capacities, rigidities, ductilities and energy-absorption capacities of the walls, considerably.

• Steel and Composite Structures
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• 제32권6호
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• pp.807-819
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• 2019

In recent earthquakes, the failure of ceiling systems has been one of the most widely reported damage and the major cause of functionality interruption in some buildings. In an effort to mitigate this damage, some scholars have studied a series of ceiling systems including plaster ceilings and mineral wool ceilings. But few studies have involved the backdrop metal ceiling used in some important constructions with higher rigidity and frequency such as the main control area of nuclear power plants. Therefore, in order to evaluate its seismic performance, a full-scale backdrop metal ceiling system, including steel runners and metal panels, was designed, fabricated and installed in a steel frame in this study. And the backdrop metal ceiling system with two perimeter attachments variants was tested: (i) the ends of the runners were connected with the angle steel to form an effective lateral constraint around the backdrop metal ceiling, (ii) the perimeter attachments of the main runner were retained, but the perimeter attachments of the cross runner were removed. In the experiments, different damage of the backdrop metal ceiling system was observed in detail under various earthquakes. Results showed that the backdrop metal ceiling had good integrity and excellent seismic performance. And the perimeter attachments of the cross runner had an adverse effect on the seismic performance of the backdrop metal ceiling under earthquakes. Meanwhile, a series of seismic construction measures and several suggestions that need to be paid attention were proposed in the text so that the backdrop metal ceiling can be better applied in the main control area of nuclear power plants and other important engineering projects.