• Journal of the Korean Wood Science and Technology
• /
• 제50권4호
• /
• pp.237-245
• /
• 2022

This study examined the structural performance of experimental parallel strand lumber (PSL) from a Larch veneer strand. The prototype of PSL from a Larch veneer strand was manufactured in the experimental laboratory and tested. The bending and dowel bearing strength were determined from the modulus of elasticity (MOE), modulus of rupture (MOR), and dowel bearing strength based on a 5% offset yield load. The test results indicated that the average MOR of PSL was higher than that of 2 × 4 dimension lumber, and the average MOE of PSL was lower than that of 2 × 4 dimension lumber. A linear relationship was observed between the MOR and MOE. The allowable bending stress of PSL was derived as specified in ASTM D2915 and compared with other research. The dowel bearing strength of PSL in parallel to the grain was approximately double that perpendicular to the grain of PSL. A comparison of several theoretical calculations based on each national code for the dowel bearing strength was conducted, and some theoretical equations produced results closer to the experimental results when it was parallel to the grain, but the difference was higher in the case perpendicular to the grain. The test results showed that PSL made with Japanese larch veneer strands appeared to be suitable for a raw material of structural composite lumber (SCL) appeared to be used as a raw material for SCL.

• 한국세라믹학회지
• /
• 제13권1호
• /
• pp.35-44
• /
• 1976

The effect of quartz which exists in clays, especially in kaolin used for the production of chamotte sagger, on the strength of refractory was examined. In this study, a mixture of chamotte 50%, kaolin 25%, plastic clay 25% in ternary component system was selected as a batch composition. To this mixture 1%, 3% and 5% of feldspar and sericite were added respectively. The plastic clay used here was separated under 170 mesh by dry process. Feldspar and sericite were separated under 325 mesh by dry process. Feldspar and sericite were separated under 325 mesh by dry process. In order to change the particle size and the content of quartz, the kaolin was separated under 60, 115, 170 and 325 mesh by wet process, substituted quartz for coarse parts of it. Chamotte was classified into three grades, coarse (5-10mesh): medium (10-20mesh): fine(20-115mesh) and the ratio was 1:1:1. Samples were formed in 0.8xIx10cm size with 12.5% water at 160kg/$\textrm{cm}^2$ pressure, and fired at 130$0^{\circ}C$ for 1 hr. The fired samples were ivnestigated by means of x-ray diffraction analysis and microscopic observation, and the physical properties of them were also examined, such as firing shrinkage, apparent specific gravity and bulk specific gravity, apparent porosity, water absorption and modulus of rupture. The obtained results are as follows: 1. When screened kaolin with low content of quartz was added to fixed chamotte-plastic clay system, the sample lowered modulus of rupture and increased apparent porosity as the size of kaolin became finer. 2. When kaolin under 325 mesh with 7.2-15.81% quartz between 60-325 mesh was added to fixed chamotte-plastic clay system, the sample had higher apparent porosity and lower modulus of ruputure as the size and the amount of quartz became larger. 3. The addition of feldspar and sericite to chamotte-plastic clay system improved apparent porosity and modulus of rupture. The effect of feldspar was better when quartz content was low, although that of sericite was better than quartz content was high.

• Journal of the Korean Wood Science and Technology
• /
• 제22권1호
• /
• pp.20-27
• /
• 1994

Water repellent preservative (WRP) treated and untreated, small-sized specimens prepared from semiwater resistant, water resistant, and tegofilm-overlaid plywood were exposed to outdoor weathering for one year. Exterior durability of specimens was evaluated on the basis of changes in dynamic modulus of elasticity, degree of delamination, modulus of elasticity, modulus of rupture, and glueline shear strength. Among untreated specimens, tegofilm-overlaid plywood showed the best outdoor durability, and durability between semiwater resistant and water resistant plywood was similar. Although WRP treatment increased the durability of all types of plywoods, the effect of treatment on the increase in durability for semi water resistant plywood was not distinct. Accordingly, it can be concluded that semi water resistant plywood, which is used for temporary construction such as concrete formwork in our country, can not be inadequate for exterior use, regardless of WRP treatment. The bending strength and glueline shear strength of untreated water resistant plywood measured after weathering for one year did not exceed the minimum value specified by Korean Standard (KS), thereby the outdoor use of water resistant plywood was not desirable without WRP treatment. Exterior durability between treated water resistant plywood and untreated tegofilm-overlaid plywood was very similar. This result suggests that if an exposed plywood surface is treated with WRP regularly water resistant plywood can be used for temporary construction. This suggestion, however, needs to be investigated. In summary, semiwater resistant plywood cannot be used for temporay construction regardless of WRP treatment. Water resistant plywood can be used only with WRP treatment. Comparing the cost of tegofilm-overlaid plywood to costs of water resistant plywood and WRP treatment, however, it can be concluded that use of tegofilm-overlaid plywood for temporay constrution is strongly suggested from the point of view of both outdoor durability and costs.

• 콘크리트학회논문집
• /
• 제28권1호
• /
• pp.105-113
• /
• 2016

순환골재를 사용한 콘크리트의 재료 및 역학 특성에 관한 대부분의 연구는 압축강도 40 MPa 이하의 콘크리트에 대하여 수행되었으며, 40 MPa 이상의 순환골재 콘크리트에 대한 역학적 특성에 대한 연구결과는 미비하다. 따라서, 이 연구에서는 순환골재 사용의 확대를 위해 40 MPa 이상의 순환골재 콘크리트의 압축강도 및 역학 특성을 파악하였다. 순환골재 콘크리트의 역학 특성을 파악하기 위하여 콘크리트 압축강도 및 순환굵은골재 치환율을 실험변수로 고려하였다. 실험변수로서 콘크리트의 압축강도는 45 및 60 MPa이고, 순환골재 치환율은 30, 50, 70 및 100%이다. 실험변수에 따른 순환골재 콘크리트의 압축강도, 탄성계수, 인장강도 및 파괴계수 특성을 분석하였다. 실험결과는 고강도 콘크리트일수록 순환골재 치환율에 따른 압축강도 감소량이 작은 것을 나타낸다. 탄성계수 실험결과와 기존설계코드에 의한 탄성계수 예측결과를 비교하였으며, 설계코드에 의한 예측결과는 실험결과를 과다평가하고 있다. 반면에 설계코드에 의한 파괴계수 예측결과와 실험결과는 잘 일치한다.

• Journal of Biosystems Engineering
• /
• 제28권3호
• /
• pp.239-244
• /
• 2003

The potential use of ultrasonic technique for firmness measurement of apples was evaluated. Mechanical properties(bioyield deformation, bioyield strength, rupture deformation, ultimate strength, and elastic modulus) and ultrasonic parameters (ultrasonic velocity, attenuation coefficient and the first peak frequency) of the apple flesh during the storage time were measured and analyzed. Ultrasonic parameters were determined from the measurement of ultrasonic wave transmission through the apple flesh specimen. Mechanical properties were obtained by universal testing machine. The bioyield strength, rupture strength, elastic modulus, ultrasonic velocity, and the first peak frequency of the apple flesh decreased with the storage time. The bioyield deformation, rupture deformation, and ultrasonic attenuation coefficient increased with the storage time. The correlation analysis between ultrasonic parameters and mechanical properties and the storage time was performed. The high correlations were found between the storage time and the ultrasonic parameters, and these relationships seem to be useful for determining the firmness of the apple flesh.

• 한국구조물진단유지관리공학회 논문집
• /
• 제20권2호
• /
• pp.49-59
• /
• 2016

KS기준 및 콘크리트표준시방서에는 순환골재를 사용한 콘크리트의 압축강도를 27 MPa 이하로 제한하고 있으며, 이에 따라 27 MPa를 초과하는 순환골재 콘크리트에 대한 역학적 특성에 대한 연구결과는 부족한 상황이다. 따라서, 이 연구에서는 순환굵은골재 사용의 확대를 위해 압축강도 30~60 MPa 범주의 굵은순환골재를 사용한 콘크리트의 압축강도를 포함한 역학적 특성을 연구하였다. 실험변수로써 물-시멘트 비와 굵은순환골재의 치환율을 고려하였다. 고려된 물-시멘트 비는 0.36, 0.46 및 0.53 이고, 순환굵은골재의 치환율은 30, 50, 70 및 100%이다. 실험변수에 따른 순환골재 콘크리트의 7일 및 28일 압축강도, 탄성계수, 인장강도 및 파괴계수 특성을 분석하였다. 물-시멘트 비가 0.36일 때의 탄성계수에 비해 0.53일 때의 탄성계수는 10% 이상 감소하였다. 탄성계수 실험결과와 기존설계코드에 의한 탄성계수 예측결과를 비교하였으며, 설계코드에 의한 탄성계수 예측결과는 실험결과를 과다평가하고 있다. 반면에 설계코드에 의한 파괴계수 예측결과는 압축강도 40 MPa 이상의 콘크리트의 파괴계수 실험결과를 과소평가하고 있다.

• Computers and Concrete
• /
• 제19권6호
• /
• pp.667-675
• /
• 2017

One of the main disadvantages of Ultra High Performance Concrete exists in the large suggested value of UHPC ingredients. The purpose of this study was to find the models mechanical properties which included a 7, 14 and 28-day compressive strength test, a 28-day splitting tensile and modulus of rupture test for Ultra High Performance Concrete, as well as, a study on the interaction and correlation of five variables that includes silica fume amount (SF), cement 42.5 amount, steel fiber amount, superplasticizer amount (SP), and w/c mechanical properties of UHPC. The response surface methodology was analyzed between the variables and responses. The relationships and mathematical models in terms of coded variables were established by ANOVA. The validity of models were checked by experimental values. The offered models are valid for mixes with the fraction proportion of fine aggregate as; 0.70-1.30 cement amount, 0.15-0.30 silica fume, 0.04-0.08 superplasticizer, 0.10-0.20 steel fiber, and 0.18-0.32 water binder ratio.

• 한국세라믹학회지
• /
• 제31권2호
• /
• pp.194-200
• /
• 1994

Pitchstone(Volcanic ejecta) reacts with CaO in hot water and increases its sedimentary volume by forming Ca(OH)2 and calcium silicate hydrates. ALC was prepared from the various gelling and curing conditions using the ratio of pitchstone/CaO was 2(CaO/SiO2 mol ratio=0.81), and then the products, crystalline phases and physical properties of ALC with experimental conditions was investigated. The crystalline phase of tobermorite with laths and plate type and the porosity were increased, the thermal conductivity was decreased with increasing gelling temperature and time. But modulus of rupture has maximum value when gelling time was 2 hrs. Othwrwise the bulk density nearly unchanged with increasing curing temperature, but the modulus of rupture was increased.

• 한국세라믹학회지
• /
• 제21권1호
• /
• pp.51-59
• /
• 1984

In this paper mechanical properties of reaction-bonded silicon nitride are studied with the variation of initial nitrogen partial pressure. At 1, 25$0^{\circ}C$ the amount of nitridation and the nucleation of nitride increase linearly with the nitrogen partial pressure increase. After the nitridation is completed the density of nitride and modulus of rupture at room temperature are increased with the amount of nitridation. When the partial pressure of nitrogen is 0.5 atm the specimen show the optimum properties that is the highest density of nitride and modulus of rupture. Also the microstructure of $\alpha$-matte is deveoped very well at that pressure of nitrogen which contributes to the strength development of specimen. It is shown that with proper control of initial partial pressure of nitrogen high strength silicon nitride body can be manufactured for dynamic applications.

• 대한화학회지
• /
• 제7권2호
• /
• pp.144-152
• /
• 1963

브리스톨釉藥을 콘 5, 8, 11 番으로 燒成했을때 나타나는 狀態에 對한 組成變化와 粒度의 京鄕을 硏究하여, 밝은 半艶消 또는 艶消釉藥을 얻을 수 있었다. 卽 各 釉藥에 對한 熱成範圍, 曲强度 및 光澤, 平滑性, 乳白度, Eggshelling, 龜裂, Pinholing, Crawling 等에 對한 因子를 決定하므로서 얼마나, 珪酸, 알카리, 石灰를 變化시켜 實際 使用可能한 良好한 釉藥을 얻었다. 製造된 브리스톨釉藥은 最低 콘 5番부터 11번 또는 그 以上에서 긴 熟成範圍를 나타냈다. Crawling의 傾向에 있어서는 ZnO 量이 增加될때 特히 甚했으나, $Al_2O_4:\;SiO_2$의 比가 크고 ZnO 量이 많을때 乳白度가 顯著하였다. 釉藥의 粒子를 가늘게 하면 熱成이 잘되나 微粒이면 Crawling이 커진다. 釉藥두께를 增加해도 Crawling 傾向이 커진다.