• Restorative Dentistry and Endodontics
• /
• 제39권3호
• /
• pp.155-163
• /
• 2014

Objectives: Light-curing of resin-based materials (RBMs) increases the pulp chamber temperature, with detrimental effects on the vital pulp. This in vitro study compared the temperature rise under demineralized human tooth dentin during light-curing and the degrees of conversion (DCs) of three different RBMs using quartz tungsten halogen (QTH) and light-emitting diode (LED) units (LCUs). Materials and Methods: Demineralized and non-demineralized dentin disks were prepared from 120 extracted human mandibular molars. The temperature rise under the dentin disks (n = 12) during the light-curing of three RBMs, i.e. an Ormocer-based composite resin (Ceram. X, Dentsply DeTrey), a low-shrinkage silorane-based composite (Filtek P90, 3M ESPE), and a giomer (Beautifil II, Shofu GmbH), was measured with a K-type thermocouple wire. The DCs of the materials were investigated using Fourier transform infrared spectroscopy. Results: The temperature rise under the demineralized dentin disks was higher than that under the non-demineralized dentin disks during the polymerization of all restorative materials (p < 0.05). Filtek P90 induced higher temperature rise during polymerization than Ceram.X and Beautifil II under demineralized dentin (p < 0.05). The temperature rise under demineralized dentin during Filtek P90 polymerization exceeded the threshold value ($5.5^{\circ}C$), with no significant differences between the DCs of the test materials (p > 0.05). Conclusions: Although there were no significant differences in the DCs, the temperature rise under demineralized dentin disks for the silorane-based composite was higher than that for dimethacrylate-based restorative materials, particularly with QTH LCU.

• 한국공간구조학회논문집
• /
• 제18권4호
• /
• pp.81-88
• /
• 2018

Seismic isolation systems have typically been used in the form of base seams in mid-rise and low-rise buildings. In the case of high-rise buildings, it is difficult to apply the base isolation. In this study, the seismic response was analyzed by changing the installation position of the seismic isolation device in 3D high - rise model. To do this, we used 30-story and 40-story 3D buildings as example structures. Historic earthquakes such as Mexico (1985), Northridge (1994) and Rome Frieta (1989) were applied as earthquake loads. The installation position of the isolation device was changed from floor to floor to floor. The maximum deformation of the seismic isolation system was analyzed and the maximum interlaminar strain and maximum absolute acceleration were analyzed by comparing the LB model with seismic isolation device and the Fixed model, which is the base model without seismic isolation device. If an isolation device is installed on the lower layer, it is most effective in response reduction, but since the structure may become unstable, it is effective to apply it to an effective high-level part. Therefore, engineers must consider both structural efficiency and safety when designing a mid-level isolation system for high-rise buildings.

• Wind and Structures
• /
• 제16권4호
• /
• pp.301-322
• /
• 2013

Recent major post-hurricane damage assessments in the United States have reported that the most common damages result from the loss of building roof coverings and subsequent wind driven rain intrusion. In an effort to look further into this problem, this paper presents a full-scale (Wall of Wind --WoW--) investigation of external and underneath wind pressures on roof tiles installed on a low-rise building model with various gable roofs. The optimal dimensions for the low-rise building that was tested with the WOW are 2.74 m (9 ft) long, 2.13 m (7 ft) wide, and 2.13 m (7 ft) high. The building is tested with interchangeable gable roofs at three different slopes (2:12; 5:12 and 7:12). The field tiles of these gable roofs are considered with three different tile profiles namely high (HP), medium (MP), and low profiles (LP) in accordance with Florida practice. For the ridge, two different types namely rounded and three-sided tiles were considered. The effect of weather block on the "underneath" pressure that develops between the tiles and the roof deck was also examined. These tests revealed the following: high pressure coefficients for the ridge tile compared to the field tiles, including those located at the corners; considerably higher pressure on the gable end ridge tiles compared to ridge tiles at the middle of the ridge line; and marginally higher pressure on barrel type tiles compared to the three-sided ridge tiles. The weather blocking of clay tiles, while useful in preventing water intrusion, it doesn't have significant effect on the wind loads of the field tiles. The case with weather blocking produces positive mean underneath pressure on the field tiles on the windward side thus reducing the net pressures on the windward surface of the roof. On the leeward side, reductions in net pressure to a non-significant level were observed due to the opposite direction of the internal and external pressures. The effect of the weather blocking on the external pressure on the ridge tile was negligible.

• 화약ㆍ발파
• /
• 제28권2호
• /
• pp.99-107
• /
• 2010

국내 발파해체기술은 저층위주로 개발, 적용되어 왔으며 1970년대 이후 건축된 고층 RC 라멘조의 내구연한으로 재건축이 필연적으로 예상돼 경제적이고 안전하며 친환경적인 발파해체기술의 개발이 요구되었다. 이에 따라 저층구조물에 적용되었던 발파해체 요소기술을 고층구조물에서 활용할 수 있도록 적용시험을 수행하였다. 고층구조물 발파해체를 위한 요소기술의 정립과 현장 적용성 여부를 판단하고, 문제점 발생 시 개선방안을 제안 해 고층건물에 대한 발파해체 기술을 개발하고자 대전 중앙데파트 발파해체현장에서 방호방법의 현장검증시험과 분진저감을 위한 물대포 현장 적용시험 및 최적천공방법 선정을 위한 요소시험을 수행해 발파해체 요소기술의 신뢰성 확보와 적용성을 확인하였다. 본 논문은 고층건물 철거 시 친환경적이고 안전하며 경제적인 발파해체 공법을 국내 기술로 시공할 수 있는 능력을 알려 외국 철거업체의 국내 철거시장진입을 방지하고 국내 해체산업의 경쟁력 제고에 이바지하고자 한다.

• Wind and Structures
• /
• 제16권1호
• /
• pp.25-46
• /
• 2013

This paper presents a boundary-layer wind tunnel (BLWT) study on the effect of variable dominant openings on steady and transient responses of wind-induced internal pressure in a low-rise building. The paper presents a parametric study focusing on differences and similarities between transient and steady-state responses, the effects of size and locations of dominant openings and vent openings, and the effects of wind angle of attack. In addition, the necessity of internal volume correction during sudden breaching, i.e., a transient response experiment was investigated. A comparison of the BLWT data with ASCE 7-2010, as well as with limited large-scale data obtained at a 'Wall of Wind' facility, is presented.

• Structural Engineering and Mechanics
• /
• 제14권3호
• /
• pp.365-380
• /
• 2002

Following a series of experiments on isolated low-rise RC shear walls with openings, a theoretical study on the backbone curve of a perforated shear wall shows that there are some important observations from experimental results that make clear a semi-empirical formula of the backbone curve of a perforated wall. Critical shear zones can be depicted from the configuration of shear walls with openings. Different factors, including the size and location of shear wall openings, the wall's height/width ratio, horizontal and vertical steel bar ratios, and location and amount of diagonal steel bars are involved in the derivation of the backbone curve. Bending and shear effects are also considered in the paper. In addition, a comparison of load and displacement for solid and perforated shear walls is discussed. Generally, the comparison between experimental curves and computed backbone curves is favorable.

• Wind and Structures
• /
• 제8권6호
• /
• pp.455-467
• /
• 2005

The effects of upstream velocity profiles on the flow around a low-rise rectangular prism submerged in a turbulent boundary layer have been investigated. Three different boundary layer profiles are generated, which are characterized by boundary layer height, displacement thickness, and momentum thickness. Flow characteristics variations caused by the different layers such as those in turbulent kinetic energy distribution and locations of re-circulating cavities and reattachment points have been precisely measured by using a PIV (Particle Image Velocimetry) technique. Observations were made in a boundary layer wind tunnel at $Re_H$=7900, based on a model height of 40 mm and a free stream velocity of 3 m/s with 15 - 20% turbulence intensity.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
• /
• 제1권2호
• /
• pp.91-101
• /
• 1996

This study is intended to summarize the contents and process of an architectural basic planning for the design competition of K University Hospital. Especially a design of low-rise and compact type hospital in sloped suburb is suggested. The major contents consists of proposed premise of planning, goal of planning, site analysis, site plan, and architectural basic plan To realize the concept of low-rise and compact type hospital which reconciles to the natural environment of the site, 4 nursing units per typical floor and hospital street system are introduced. And to design a "hospital unlike hospital", streamline form of hospital building is proposed.

• Earthquakes and Structures
• /
• 제15권1호
• /
• pp.45-65
• /
• 2018

Over the last three decades, Performance-based Earthquake Engineering (PBEE) has been mainly developed for high seismicity regions. Although information is abundant for PBEE throughout the world, the application of PBEE to lower-seismicity regions, such as those where the magnitude of the maximum considered earthquake (MCE) is less than 6.5, is not always straightforward because some portions of PBEE may not be appropriate for such regions due to geological differences between high- and low-seismicity regions. This paper presents a brief review of state-of-art PBEE methodologies and introduces the seismic hazard of lower-seismicity regions, including those of the Korean Peninsula, with their unique characteristics. With this seismic hazard, representative low-rise RC MRF structures and high-rise RC wall residential structures are evaluated using PBEE. Also, the range of the forces and deformations of the representative building structures under the design earthquake (DE) and the MCE of South Korea are presented. These reviews are used to propose some ideas to improve the practice of state-of-art PBEE in lower-seismicity regions.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1990년도 봄 학술발표회 논문집
• /
• pp.72-77
• /
• 1990

Results are presented of the cyclic loading tests of there low-rise shear wall assembligies using high strength concrete. The possibilities of achieving an acceptable level of energy dissipation in one story shear walls, mainly by flexural yielding, are examined. Mechanisms of flexural and shear resistance are reviewed with emphasis on aspects of sliding shear. Detrimental effects of sliding shear are demonstrated together with improvement achieved by use of diagonal wall reinforcements. It is postulated that with suitably arranged diagonal wall reinforcements a predominantly flexural response mode with good energy dissipation characteristics can be achieved in low-rise shear walls.