• 한국구조물진단유지관리공학회 논문집
• /
• 제15권1호
• /
• pp.180-188
• /
• 2011

최근 대구경철근에 적용할 수 있는 기계적 철근이음장치에 대한 연구가 진행되고 있다. 본 논문에서는 대구경 기계적 철근이음재에 대한 구조적 성능평가에 대하여 연구가 수행되었다. 원자력발전소에 대구경의 기계적 철근이음장치를 적용하기 위해서 2가지 형태의 철근이음장치에 대한 실험이 수행되었으며, 원자력발전소에 적용되는 11번과 14번 및 18번에 대한 대구경 철근 이음 장치가 조립되어 정적 및 동적실험이 수행되었다. 실험은 ASME SEC III DIV.2 CC-4330에 따라 이루어졌다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제15권6호
• /
• pp.212-218
• /
• 2011

본 논문에서는 실험을 통해 섬유복합 보강근이 콘크리트 표면저항치에 미치는 영향을 고찰하였다. 본 실험에서 콘크리트의 표면저항치는 Wenner기법에 의하여 4probe 방식에 의하여 측정되었다. 이형철근과 국내에서 생산된 GFRP 보강근 및 CFRP 보강근이 사용되었으며, 비교를 위하여 무보강 실험체의 표면저항치도 측정되었다. 기존의 연구에 따르면, 내부에 보강된 이형철근에 의하여 저항치가 영향을 받게 되는데, 보강근의 위치, 깊이 및 보강방향에 의하여 영향을 받는 것으로 보고된바 있다. 본 논문에서는 노후된 콘크리트구조물의 보강재와 신설구조물의 철근을 대신하여 사용될 수 있는 GFRP 및 CFRP 보강근이 사용되었을 때, 표면저항치의 변화를 실험적으로 고찰하였으며, 이 결과는 향후 FRP가 사용된 구조물의 부식상태 파악을 위한 비파괴시험 결과에 대한 평가에 유용하게 사용될 수 있다.

• 한국한의학연구원논문집
• /
• 제15권3호
• /
• pp.53-61
• /
• 2009

Oxytocin(OT), classically known to stimulate labour and milk ejection, contributes to play an important role in a wide range of behavioral effects including drug addiction. An increasing body of evidence suggests that OT ameliorates acute and long-term effects of commonly used drugs by means of interacting with the mesolimbic dopamine system. Mesolimbic dopamine system is thought to play a major role in the reinforcing properties of drug abuse. Oxytocin receptors in the nucleus accumbens(NAc) and ventral tegmental area(VTA) have been implicated in the regulation of reinforcing effects in abused drugs. In the same way acupuncture may attenuate the reinforcing effects of abused drugs in the NAc and VTA. We have an interest in similar liaison between the substrates of acupuncture and drug addiction that may involve OT. Here, we described the possibility that acupuncture modulates the reinforcing and sensitizing properties of abused drugs in the dopaminergic system via the regulation of activities in the oxytocinergic system. The elements in this paper are summarized as follows : neuroanatomical studies of oxytocinergic innervation and distribution of oxytocin receptors; experiments related to the methamphetamine, cocaine, morphine and ethanol; experiments related to the oxytocin and acupuncture.

• 한국구조물진단유지관리공학회 논문집
• /
• 제3권3호
• /
• pp.269-277
• /
• 1999

The purpose of this study is to investigate the structural behavior of reinforced concrete columns rehabilitated with epoxy-bonded steel plates subjected to axial load. Eleven specimens were made to evaluate structural capacity of reinforced concrete columns rehabilitated with steel plates. This study considers the change of the internal force and the deformation of reinforced concrete column with reinforcing steel plates, and analyzes the effect of the improvement of strength and ductility. Based on the test results, this study brings the following conclusions. In case of the effect of reinforcement by the ratio of the same volume, the internal force for the test model, which the width of the reinforcing steel plate is small, is effectively higher. The smaller the width and the thickness of reinforcing steel plate, the more effective the effect of reinforcement is. For applying the theorical equation by Uzumeri, the maximum load and the coefficient of effective crossing reinforcement by the width and the thickness of steel plate reflected the properties of reinforcing steel plate.

• Advances in concrete construction
• /
• 제1권1호
• /
• pp.103-119
• /
• 2013

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localization in the reinforcement at cracks. The bond strength of reinforcing bars is not only governed by concrete quality, but also by construction details such as bar ribbing, bar spacing or concrete cover thickness. For new concrete structures, a potentially unfavorable impact on bond strength can easily be anticipated through appropriate code rules on construction details. In existing structures, these requirements may not be necessarily satisfied, consequently requiring additional considerations. This two-part paper investigates in a theoretical study the impacts of the most frequently encountered construction details which may not satisfy design code requirements on bond strength, steel strain localization and plastic deformation capacity of cracked structural concrete. The first part introduces basic considerations on bond, strain localization and plastic deformation capacity as well as the fundamentals of the Tension Chord Model underlying the further investigations. It also analyzes the impacts of the hardening behavior of reinforcing steel and concrete quality. The second part discusses the impacts of construction details (bar ribbing, bar spacing, and concrete cover thickness) and of additional structure-specific features such as bar diameter and crack spacing.

• 한국건축시공학회지
• /
• 제21권6호
• /
• pp.617-627
• /
• 2021

본 연구에서는 공동주택의 리모델링 시 기초보강공법의 하나인 하중전이 장치를 이용한 기초보강공법에 대해 3차원 유한요소 수치해석 연구를 수행하였다. 실대형 현장실험을 통해 수치모형을 검증하였고, 매개변수 해석을 통해 하중전이장치의 마찰계수, 말뚝의 축강성이 기초보강공법의 성능에 미치는 영향을 확인하였다. 그 결과 하중전이 장치를 이용한 기초보강공법은 보강 중, 보강 후에도 기존 말뚝에 작용하는 하중을 자유롭게 조절가능함을 확인하였다.

• Advances in concrete construction
• /
• 제14권2호
• /
• pp.79-92
• /
• 2022

The amount and configuration of transverse reinforcement are known as critical parameters that significantly affect the lateral confinement of concrete, the ductility capacity, and the plastic hinge length of RC columns. Based on test results, this study investigated the effect of the three variables on structural indexes such as neutral axis depth, lateral expansion of concrete, and ductility capacity. Five reinforced concrete column specimens were tested under cyclic flexure and shear while simultaneously subjected to a constant axial load. The columns were reinforced by two types of reinforcing steel: rectangular hoops and spiral type reinforcing bars. The variables in the test program were the shape, diameter, and yield strength of transverse reinforcement. The interactive influence of the amount of transverse reinforcement on the structural indexes was evaluated. Test results showed that when amounts of transverse reinforcement were similar, and yield strength of transverse reinforcement was 600 MPa or less, the neutral axis depth of a column with spiral type reinforcing bars was reduced by 28% compared with that of a column reinforced by existing rectangular hoops at peak strength. While the diagonal elements of spiral-type reinforcing bars significantly contributed to the lateral confinement of concrete, the strain of diagonal elements decreased with increases of their yield strength. It was confirmed that shapes of transverse reinforcement significantly affected the lateral confinement of concrete adjacent to plastic hinges. Transverse reinforcement with a yield strength exceeding 600 MPa, however, increased the neutral axis depth of normal-strength concrete columns at peak strength, resulting in reductions in ductility and energy dissipation capacity.

• 센서학회지
• /
• 제32권3호
• /
• pp.159-163
• /
• 2023

Salt cores have attracted considerable attention for their application to the casting process of electric vehicle parts as a solution to ecological issues. However, the salt core still has low mechanical strength for use in high-pressure die casting. In this study, we investigated the improvements in the bending strength of KCl-based salt cores resulting from the use of reinforcing materials. KCl and Na₂CO₃ powders were used as matrix materials, and glass fiber and carbon fiber were used as reinforcing materials. The effects of carbon fiber and glass fiber contents on the bending strength properties were investigated. Here, we obtained a new fiber-reinforced salt core composition with improved bending strength for high-pressure die casting by adding a relatively small amount of glass fiber (0.3 wt%). The reinforced salt core indicates the improved properties, including a bending strength of 49.3 Mpa, linear shrinkage of 1.5%, water solubility rate of 16.25 g/min·m² in distilled water, and hygroscopic rate of 0.058%.

• Geomechanics and Engineering
• /
• 제28권2호
• /
• pp.135-143
• /
• 2022

Soils are natural granular materials whose mechanical properties differ according to the size and composition of the particles, so soils exhibit an obvious scale effect. Traditional soil mechanics is based on continuum mechanics, which can not reflect the impact of particle size on soil mechanics. On that basis, a matrix-reinforcing-particle cell model is established in which the reinforcing particles are larger-diameter sand particles and the matrix comprises smaller-diameter bentonite particles. Since these two types of particles deform differently under shear stress, a new shear-strength theory under direct shear that considers the stress concentration and bypass phenomena of the matrix is established. In order to verify the rationality of this theory, a series of direct shear tests with different reinforcing particle diameter and volume fraction ratio are carried out. Theoretical analysis and experimental results showed that the interaction among particles of differing size and composition is the basic reason for the size effect of soils. Furthermore, the stress concentration and bypass phenomena of the matrix enhance the shear strength of a soil, and the volume ratio of reinforcing particles has an obvious impact on the shear strength. In addition, the newly proposed shear-strength theory agrees well with experimental values.

• Earthquakes and Structures
• /
• 제25권4호
• /
• pp.283-296
• /
• 2023

This paper presents experimental and numerical studies of seismic performance on reinforced concrete (RC) wide beam (WB) joints. Two RC-WB joint specimens and one conventional RC joint specimen were fabricated using the reinforcing details of longitudinal reinforcing bars in a beam as a variable, and quasi-static cyclic loading tests were performed. The results were used to compare and analyze the load-drift ratio relationship, failure mode, and seismic performance of the specimens quantitatively. In addition, a finite element (FE) analysis of the RC-WB joint was conducted, and the rationality of the FE model was validated by comparing it with the test results. Based on the FE model, a parametric study was conducted, where the ratio of longitudinal reinforcing bars placed on the outer and inner parts of the joint (𝜌_ex/𝜌_in) was a key variable. The results showed that, in the RC-WB joint, an increase of 𝜌_ex/𝜌_in leads to more severe damage to concrete, which reduces the seismic performance of the RC-WB joints.