• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.3
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• pp.99-106
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• 1990

This study was aimed to see the effect of chemical grout on fresh granite joint shear strength. The grouting chemical used in this study was composed of 25% water glass. Direct shear tests were performed on the chemical filled joints, which had been made artificially with granite. The test results show that chemical grouted rock jonts have markedly reduced shear strength comparing with the ungrouted fresh joints and they sheared within chemical grout before the rock to rock contact had been established, while the ungrouted joint sheared between rock surfaces from the beginning of shear deformation. With chemical grouted joints the shear stress slowly reached its maximum without showing distinct peak shear strength. Therefore the shear stiffness of joints were decreased with increasing thickness of grout. but the shear strain at failure was increased with it.

• Journal of the Korean GEO-environmental Society
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• v.16 no.6
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• pp.31-38
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• 2015

Recently, the participation on the development of the natural gas pipeline in Russia as well as the recent construction of the second Korean Antarctic research station, the Jangbogo station provide the research interests on the behavior of the permafrost ground. To investigate the effect of fines on the mechanical responses of frozen sands, unconfined compression tests were performed on the frozen sands with 0, 5, 10 and 15% of fine contents at -5, -10 and $-15^{\circ}C$. The poorly graded (SP) Joomunjin sand and kaolinite, silt with low plasticity (ML) were used for the preparation of the frozen soil specimens. The mechanical responses of the tested soils were investigated via unconfined compression tests in the temperature controlled laboratory and analyzed in terms of peak unconfined compressive strength and secant modulus at 50% of the peak strength. As the fine contents increase, the unfrozen water contents increase and thus the strength and stiffness of frozen soils decrease. The increment of the stiffness and strength due to the temperature decrease vary with the fine contents.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.2
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• pp.168-175
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• 2022

With the recent development of nanotechnology, its application in the field of construction materials is continuously increasing. However, until now, studies on the bond characteristics of concrete and rebar for applying high-strength lightweight concrete with a compressive strength of 50 MPa and a unit weight of 16 kN/m³ to structural members are lacking. Therefore, in this paper, 81 specimens of high-strength lightweight concrete with a compressive strength of 50 MPa and a unit weight of about 16 kN/m³ were fabricated and a direct pull-out tests were performed. The design code for the bond strength of ACI-408R and the experimental results are shown to be relatively similar, and as a result of the CEB-FIP and modified CMR bond behavior models through statistical analysis, it is shown to describe well on average.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.17-22
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• 2011

Based on the form of the Tsai-Hill criterion, a new failure criterion for anisotropic material subjected to combined stress is developed and demonstrated. It is capable of accurately calculating the strength of anisotropic materials. The generality and accuracy of the present failure criterion are illustrated by examination through the use of Kraft paperboards under various loading conditions. Compared to the Tsai-Hill theory, which is much too conservative at high levels of shear stress, the present criterion has a good agreement with the experimental data. It also has the ability to calculate the strength more simply, compared to the Tan-Cheng theory.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.895-903
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• 1987

This paper investigates the problem of cracks emanating from a circular hole in an orthotropic infinite plate. The mixed-mode stress intensity factors are obtained by using the modified mapping-collocation method. To investigate the effect of anisotropy and circular hole boundary on crack tip singularity, stress intensity factors are considered as functions of the normalized crack length for various types of laminated composite. The results indicate a strong dependence of the stress intensity factor on the material anisotropy and geometry.

• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.895-901
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• 2009

Fatigue fracture of the welded joints of bogie frames is one of unsolved problems. To improve the fatigue strength of the welded joints, various techniques have been applied. In this study, we have investigated the effect of shot peening on the fatigue characteristics of SS400 welded specimens. The fatigue lives of four kinds of welded specimens were examined; welded, PWHT, shot peened, and shot peened after PWHT. The results of the fatigue tests show that the fatigue limit of the shot-peened specimens is higher than that of the welded specimens, and the PWHT specimens have a lower fatigue limit than the welded specimens. It was found that shot peening is a very effective method to improve the fatigue strength of SS400 welded joints.

• Cement
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• s.66
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• pp.12-15
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• 1977

석회석과 고로수재 slag을 1.6 : 1로 혼합 분쇄한 원료를 1,450$^{\circ}C$에서 소결하여 고$C_3A$ clinker를 얻었다. 이 clinker 중에는 $C_3S$ 40$\%$, $C_2S$ 31$\%$, $C_3A$ 22$\%$, $C_4AF$ 2$\%$를 함유하고 있으며 보통 크링카 보다 $C_3A$ 함량이 2$\~$3배 정도 높고, clinker 색은 연두색을 띄는 것이 특색이다. 이와 같이 $C_3A$ 함량이 높은 시멘트의 특성 및 제조 가능성을 검토한 결과는 다음과 같다. 1) 석회석과 slag를 1.6 : 1(61.5$\%$ : 38.5$\%$)로 사용할 경우 보통 시멘트 제조시 석회석 사용량 보다 약 28$\%$ 정도 절감되나 고품위의 석회석이 요구된다. 2) 동일 free CaO 0.4$\%$를 기준으로 소성할 경우 고$C_3A$ clinker가 보통 clinker 보다 소성 시간이 20분 단축된다. 3) carbonate 분해열을 비교하면 고$C_3A$ 시멘트 원료가 보통 시멘트 원료보다 116Kcal/$\cal{kg}$-cl 절감된다. 4) $C_3A$ 함량이 높아 가소성이 저하되고 표준연도의 시멘트 paste를 얻기 위하여서는 보통 시멘트 보다 많은 물량이 요구되며 응결시간도 빠르다. 5) Blaine 3,000$cm^3$/g으로 분쇄한 고$C_3A$ 시멘트의 3 일강도는 보통 시멘트 보다 40$\~$50$\cal{kg}$/$cm^3$ 더 높으나 28 일 강도는 다소 저하되는 경향이며 Blaine 5,000$cm^2$/g으로 분쇄한 고$C_3A$ 시멘트는 조강 시멘트와 같은 강도 수준이다.

• Journal of Korean Society of Steel Construction
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• v.14 no.2
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• pp.349-356
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• 2002

Cold-Formed C-section and Lipped C-section are commonly used as structural members of steel houses in Korea. Both are made of SGC41 steel. However, special Cold-Formed Sections with unique cross sectional shape have been developed and widely used in advanced countries. This research focused on the newly developed thin-walled Cold-Formed Sections which possess not only high strength and stiffness but also other advantages in construction. A series of compression tests was conducted to investigate the structural behavior of a compression member, including its load carrying capacity. Test results were compared with analytical study results.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.258-265
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• 2001

Compression and bending test have been conducted to evaluate the mechanical performance of CFRC at several different temperature up to $2000^{\circ}C$ . Tools and several grips for the test at high temperature were designed to obtain mechanical properties of CFRP. A major cause of increasing strength according to increasing the density and the temperature were analyzed. SEM method was utilized to find out the damage and the fracture mechanism. The new simple equation for the L(span length)/h(beam height) of specimens and for the failure criterion on the 4 point bending were proposed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.99-102
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• 2008

This study investigates the properties of the flow, air content, strength, hydration heat, and the autogenous shrinkage, and the results are summarized as following. As a properties of fresh concrete, the flow increased and the air content decreased as the replacement ratio of BS increased. The time of set delayed as the replacement ratio of BS increased by latent hydraulicity. The compressive strength of hardening concrete was smaller than OPC as the replacement ratio of BS increased at young concrete, however it was more than equal after 28th day and from then on. The rising temperature ratio which occurs by simplicity insulation decreased as the replacement ratio of BS increased, but it increased by latent hydraulicity reaction at the latter half. The length ratio of autogenous shrinkage of OPC was 319×10^-6, however it was shorter when the replacement ratio was 40% as showing 290×10^-6.