• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.339-346
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• 2001

For temporary excavation support in private land area, the strand of ground anchor should be removed In order to get permission to install anchors. The extractable or removable-strand compression anchor system was developed and evaluated by a series of pull-out load tests. Anchor pull-out tests were performed on seven instrumented full-scale low-pressure grouted anchors installed in weathered soil at the Geotechnical Experimentation Site at Sungkyunkwan University, Four anchors are the compression type anchors and three are the tension anchors. Performance test, creep test, and long term relaxation test were performed and presented. Load distributor was developed in order to distribute large compressive stresses in grout.

• 한국지반신소재학회논문집
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• 제15권4호
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• pp.63-69
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• 2016

본 논문은 삼축압축시험(CD)과 개선된 직접전단시험 결과 얻어진 불포화토의 전단특성을 비교분석하여 새로이 개선된 직접전단시험장비의 실용성을 검증하였다. 2010년 경기도 양평군 토석류 발생사면에서 채취한 시료를 대상으로 불포화토 상태의 전단강도실험을 수행하였다. 다른 두 종류의 실험방법에서 낮은 모관흡수력이 작용하는 경우는 전단강도와 선형적인 관계를 나타내며, 모관흡수력의 증가함에 따라 불포화토의 겉보기 점착력 역시 선형적으로 증가하였다. 다른 두 실험장비에 의한 결과를 비교한 결과, 산정된 불포화토의 강도정수($c^{\prime}$, ${\phi}^b$)는 전단 상자의 구속효과가 있는 개선된 직접전단시험에서 다소 크게 나타났다.

• 한국안전학회지
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• 제33권2호
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• pp.94-103
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• 2018

As of July 1, 2017, the method of quality management of construction equipment had been changed completely. In case of manufacturing and distributing pipe supports, the support length according to the safety certification standard shall be not more than 6 m and the compressive strength shall be not less than 40,000 N at the maximum height. However, the field tests for the quality control standard were usually performed at 3.5 m when the length of the pipe supports is 3.5 m to 4.0 m, and the compression strength was specified to be more than 35,300 N. This difference in the two standards can cause confusion in practice. In this study, the compression load of the pipe supports was tested and found to be more than 30% defective. Therefore, it is necessary to review the modification of the safety certification and quality standards to improve the standard requirements.

• Wind and Structures
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• 제12권6호
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• pp.505-517
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• 2009

Synchronous wind-induced pressures, measured in wind-tunnel tests on model buildings instrumented with hundreds of pressure taps, are an invaluable resource for designing safe buildings efficiently. They enable a much more detailed, accurate representation of the forces and moments that drive engineering design than conventional tables and graphs do. However, the very large volumes of data that such tests typically generate pose a challenge to their widespread use in practice. This paper explains how a wavelet representation for the time series of pressure measurements acquired at each tap can be used to compress the data drastically while preserving those features that are most influential for design, and also how it enables incremental data transmission, adaptable to the accuracy needs of each particular application. The loss incurred in such compression is tunable and known. Compression rates as high as 90% induce distortions that are statistically indistinguishable from the intrinsic variability of wind-tunnel testing, which we gauge based on an unusually large collection of replicated tests done under the same wind-tunnel conditions.

• 터널과지하공간
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• 제21권3호
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• pp.216-224
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• 2011

본 연구에서는 Class II 거동에 대해 입자결합모델을 이용하여 수치해석적인 방법으로 살펴보았으며, 횡방향 변형률 제어 압축시험을 수치해석적으로 모사할 수 있는 방법을 제시하였다. 수치해석에서 사용된 미시변수는 스웨덴 Aspo Hard Rock Laboratory에서 수행한 일축압축시험을 이용하여 결정하였다. 제시된 수치해석 기법을 이용해 Aspo 암석의 Class II 거동을 효과적으로 모사할 수 있었으며, 수치해석의 결과는 실험실 시험 결과와 잘 일치하였다.

• 소성∙가공
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• 제20권7호
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• pp.491-497
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• 2011

This work describes a method for determining material parameters included in recrystallization and grain growth models of metallic materials. The focus is on the recrystallization and grain growth models of Ni-Fe based superalloy, Alloy 718. High temperature compression test data at different strain, strain rate and temperature conditions were chosen to determine the material parameters of the model. The critical strain and dynamically recrystallized grain size and fraction at various process conditions were generated from the microstructural analysis and strain-stress relationships of the compression tests. Also, isothermal heat treatments were utilized to fit the material constants included in the grain growth model. Verification of the determined material parameters is carried out by comparing the average grain size data obtained from other compression tests of the Alloy 718 specimens with the initial grain size of $59.5{\mu}m$.

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

• 한국해양공학회지
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• 제16권5호
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• pp.49-55
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• 2002

The compression anchor is characterized by decrement of progressive failure, simple site work, economy and durability compared with tension anchor. In this paper, compression anchor is analysed through the laboratory element tests. The formula to be estimate the grout strength in fixed part of compression anchor and the effective reinforcement method for several types of soil were suggested. The following conclusions were made from this study : (1) A formula, which is able to calculate the grout strength in the fixed part of the compression anchor, is suggested. (2) The strength increment ratios( $R_{si}$) are 100％, 132％, 147％, 217％ according to the reinforcement method of grout. The reinforcement method is Non, Outside spiral, Inside-Outside spiral, Steel pipe, respectively. (3) The strength increment ratios( $R_{si}$) by reinforcing can be 8.23 times the strength increment effect according to the reinforcement types and ground confining pressure. (4) The steel pipe reinforcement is most effective in decomposed soil while, in the case of hard rock ground, high confining pressure is exerted on the grout, so there is no need to use reinforcements.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.120-123
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• 2016

The rotor of a turbomolecular drag pump is generally made of an aluminum alloy. Its surface finish is affected by various processes that the rotor itself undergoes during the manufacturing phase. The impact of different surface finishes on the pumping performances of a turbomolecular pump has been mainly investigated by Sawada et al [1]. The present work aims to broaden the previous bibliographic study to the drag stages of a turbomolecular pump by testing the impact of different surface finishes on the compression ratio of the pump. Experimental tests have been made focusing on two processes: the corundum sandblasting and the glass microspheres shot-peening. Both the processes flatten and/or physically remove EDM melted spheres; in particular, blasted surfaces obtained by glass shot-peening are generally smoother than surfaces obtained by corundum sandblasting. In order to characterize the surface texture left by such processes, preliminary surface roughness measurements have been made on the drag rotor disks of several pumps. The experimental tests conducted on both sandblasted and shot-peened rotors confirms previous results obtained on the turbo stages by Sawada et al. [1], showing that the average roughness of the surface has an impact on the compression ratio of the pump; in particular, an increment in the surface roughness causes a corresponding increment in the compression ratio of the pump and vice versa. For the tested pumps, the higher surface roughness gives a factor of increment of about 2 on the measured hydrogen maximum compression ratio of the pump.

• Steel and Composite Structures
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• 제43권2호
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• pp.201-219
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• 2022

This paper firstly proposed high performance composite columns for cold-region infrastructures using ultra-high performance concrete (UHPC) and ultra-high strength steel (UHSS) Q960E. Then, 24 square UHPC-filled UHSS tubes (UHSTCs) at low temperatures of -80, -60, -30, and 30℃ were performed under axial loads. The key influencing parameters on axial compression performance of UHSS were studied, i.e., temperature level and UHSS-tube wall thickness (t). In addition, mechanical properties of Q960E at low temperatures were also studied. Test results revealed low temperatures improved the yield/ultimate strength of Q960E. Axial compression tests on UHSTCs revealed that the dropping environmental temperature increased the compression strength and stiffness, but compromised the ductility of UHSTCs; increasing t significantly increased the strength, stiffness, and ductility of UHSTCs. This study developed numerical and theoretical models to reproduce axial compression performances of UHSTCs at low temperatures. Validations against 24 tests proved that both two methods provided reasonable simulations on axial compression performance of UHSTCs. Finally, simplified theoretical models (STMs) and modified prediction equations in AISC 360, ACI 318, and Eurocode 4 were developed to estimate the axial load capacity of UHSTCs at low temperatures.