• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
• /
• pp.150-155
• /
• 2003

Fractures in the form of micro cracks are commonly found in natural rocks. A rock behaves in a complex way due to fracture; in particular, the anisotropic strength of a rock material is significantly influenced by the presence of these fractures. Therefore, it is essential to understand the failure mechanism of a fractured rock. In this study, a fractured rock is formulated in terms of fabric tensor based on geometric and mechanical simplifications. In this way, position, density and shape of fractures can be determined by the fabric tensor so that rocks containing multi-fractures can successfully be modeled. Also an index to evaluate the degree of anisotropy of a fractured rock is proposed. Hence, anisotropic strength of a rock containing fractures under uniaxial compression condition is estimated through a series of numerical analyses for the multi-fractured model. Numerical investigations are carried out by varying the fracture angle from $0^{\circ}\;to\;90^{\circ}$ and relationship between uniaxial compression strength and the degree of anisotropy is investigated. By comparing anisotropic strength of numerical analysis with analytic solution, this study attempts to understand the failure mechanism of rock containing fractures.

• 한국구조물진단유지관리공학회 논문집
• /
• 제2권3호
• /
• pp.212-222
• /
• 1998

In several structural problems, the low concrete strength of compression members has the severest influence on the structural safety. However, the repairing and strengthening techniques for compression members are not established and evaluated. This study aimed to develop and evaluate the rehabilitation techniques to obtain proper structural strength of wall with low concrete strength. The specimens with low strength of concrete were retrofitted with commonly using section increase method and epoxy bonded glass fiber techniques. The tests were executed to failure under concentric and eccentric loads. In this paper, the structural behavior and failure modes were investigated to evaluate the strengthening effects of walls subjected to compression and out-of-plane bending.

• 한국지반환경공학회 논문집
• /
• 제14권8호
• /
• pp.5-9
• /
• 2013

본 연구에서는 저에너지, 친환경적인 방법의 지반개량을 목적으로 하는 유기산재의 지반개량재로서의 강도특성을 모색하였다. 이에 유기산재를 활용하여 재령 28일까지의 일축압축강도시험 및 삼축압축시험을 통한 흙의 강도 변화에 대해 분석하였다. 유기산 재료를 첨가한 점토의 강도는 재령이 길어질수록, 유기산재 혼합비가 커질수록 전반적으로 증가하는 경향을 나타내었다. 유기산계 지반개량재 혼합에 따른 점토의 강도 증진 효과를 파악하는데 있어서, 일축압축강도시험과 삼축압축시험 결과를 통해 유기산재가 지반개량재로 쓰였을 때 가져오는 강도 증대효과가 있다는 것을 알 수 있었다. 결과적으로, 실내시험을 통해 지반개량에 있어 유기산계 지반개량재의 활용가능성을 볼 수 있었다. 향후 세부적인 시험과 현장시험이 좀 더 명확한 강도증진을 규명하는데 도움이 될 것으로 판단된다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2000년도 연약지반처리위원회 학술세미나
• /
• pp.71-78
• /
• 2000

SHANSEP method involves the consolidation to stresses in excess of the preconsolidation pressure in order to overcome sample disturbance effect. The concept of SHANSEP is based on an approach to laboratory test which attempts to reproduce the in-situ conditions more closely than is possible in routine tests and evaluates normalized strength parameters for the soil as a function of OCR. But SHANSEP method can be applied only to fairly uniform clay deposits, and is unsuitable for a random deposit. In this study, CK/sub o/U triaxial compression test and incremental loading consolidation test were performed for the application of SHANSEP method on Yangsan clay. During the K/sub o/-consolidation, triaxial specimens were consolidated to stress equal to two times the in-situ vertical effective stress. And for overconsolidated condition, the specimens were swelled to a known vertical effective stress in order to have the desired OCR. With the results of CK/sub o/U triaxial compression test using the block samples, the relationship between c/sub u//σ/sub vc/' and OCR on Yangsan clay was established. For evaluating the undrained shear strength of Yangsan clay with depth, CK/sub o/U triaxial compression test was performed using the piston samples taken from Yangsan site. And also undrained shear strength was analyzed from the in-situ test such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that of CK/sub o/U triaxial compression test.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.35-40
• /
• 2001

The exact solution of strength of reinforced concrete RC columns subjected to axial compression combined with biaxial bending needs trial and adjustment procedure to find the depth and inclination of the neutral axis. Thus, approximate methods of analysis and design for biaxial bending are used in practice. Load contour interprets the relation of biaxial bending and equivalent uniaxial bending by u factor which is related to material properties and column shapes. The purpose of this study is to investigate the behavior of high strength RC columns subjected to the combined axial compression and biaxial bending. Fifteen test specimens with dimensions of 200mm$\times$200mm and 4-Dl3 longitudinal steel were examined. The variable of the test is compressive strength of concrete (350, 585, 650kgf/$cm^{2}$), compression load ratio (0.2$P_{o}}$, 0.35$P_{o}}$, 0.5$P_{o}}$), and inclination of loading ($\theta$=0, 22.5, $45^{\circ}$). Test results of coefficient $\alpha$ depending on the compressive strength of concrete are compared with ACI code.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
• /
• pp.571-572
• /
• 2009

초고강도 콘크리트의 개발에 따라 철근 압축이음에 대한 연구 필요성이 높아지고 있다. 현행 설계 기준에서 콘크리트강도와 횡보강근의 영향을 고려하지 않기 때문에 압축이음길이가 인장이음길이보다 길어지는 기현상(奇現象)이 발생한다. 본 연구에서는 51개 실험체의 결과를 바탕으로 40MPa부터 70MPa까지 콘크리트에 대한 압축이음길이 설계식을 제안하였다. 본 연구에서 제안된 압축이음길이 설계식을 이용하여 고강도 콘크리트에서 압축이음길이가 인장이음길이보다 길어지는 이상 현상을 해소할 수 있다. 더불어 제안된 압축이음길이 설계식은 통계적 기법에 기반을 두어 재료강도와 동일한 수준의 신뢰성을 확보할 수 있다.

• 천문학회보
• /
• 제37권2호
• /
• pp.114.1-114.1
• /
• 2012

To measure the magnetic field strength in the solar corona, we examined 10 fast (>1000 km/s) limb coronal mass ejections (CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3-15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

• Computers and Concrete
• /
• 제7권2호
• /
• pp.191-202
• /
• 2010

A laboratory investigation was conducted to characterize the constitutive property behavior of Cor-Tuf, an ultra-high-performance composite concrete. Mechanical property tests (hydrostatic compression, unconfined compression (UC), triaxial compression (TXC), unconfined direct pull (DP), uniaxial strain, and uniaxial-strain-load/constant-volumetric-strain tests) were performed on specimens prepared from concrete mixtures with and without steel fibers. From the UC and TXC test results, compression failure surfaces were developed for both sets of specimens. Both failure surfaces exhibited a continuous increase in maximum principal stress difference with increasing confining stress. The DP tests results determined the unconfined tensile strengths of the two mixtures. The tensile strength of each mixture was less than the generally assumed tensile strength for conventional strength concrete, which is 10 percent of the unconfined compressive strength. Both concretes behaved similarly, but Cor-Tuf with steel fibers exhibited slightly greater strength with increased confining pressure, and Cor-Tuf without steel fibers displayed slightly greater compressibility.

• 대한물리치료과학회지
• /
• 제28권1호
• /
• pp.1-10
• /
• 2021

Background: This study is goal to explore the effects of swiss ball exercise on muscular strength, flexibility, and balance in healthy adults with and without pelvic compression belts. Design: Randomized Controlled Trial. Methods: This study randomly divided the experimental and control groups in 24 healthy adults wearing pelvic compression belts, and they conducted Swiss ball exercise programs, 5 times for 40 minutes a week during 3 weeks in conclusion 15 times. Results: The results showed that the experimental groups have increased significantly in muscle strength and flexibility (p<.05). Conclusion: This study showed that pelvic compression belts and Swiss ball exercise programs will help health improvements such as muscle strength, flexibility, and balance in normal adults, and it is also thought to be worth applying to patients with back pain.

• Steel and Composite Structures
• /
• 제43권4호
• /
• pp.431-445
• /
• 2022

A double-skinned composite tubular (DSCT) column, which is an internally confined concrete-filled tubular column with a hollow section, has been developed for efficient use of materials that reduce self-weight and enhance seismic performance. It exhibits excellent material behavior with ductility owing to the confinement induced by outer and inner steel tubes. This study conducted axial compression tests considering the effects of steel tube thickness and hollow diameter ratios of DSCT columns on the material behavior of confined concrete under pure axial compression on concrete cores. From the axial compression tests, various combinations of outer and inner tube thicknesses and two different hollow section ratios were considered. Additionally, confined concrete material behavior, axial strength, failure modes, and ductility of DSCT columns were evaluated. Based on this study, it was concluded that the tests show a good correlation with peak strength and shapes of nonlinear stress-strain curves presented in literature; however, the thinner outer and inner steel tubes may reduce the ductility of DSCT columns when using thinner outer and inner tubes and higher confined stress levels. Finally, the minimum thickness requirements of the steel tubes for DSCT columns were discussed in terms of strength and ductility of test specimens.