http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
구봉근,라재웅,이재범,류연종,이현석 충북대학교 건설기술연구소 2003 建設技術論文集 Vol.22 No.2
As concrete is prevented from shrinking freely, tensile stresses develop which frequently result in cracking. Cracks in reinforced concrete structures reduce overall durability by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of the reinforcing steel. Highway pavement, bridge decks, and industrial floors are especially susceptible to this type of deterioration since these structures exhibit high rates of shrinkage and are frequently exposed to aggressive environmental conditions. The objectives of this investigation included the implement of experimental procedures for assessing shrinkage cracking behavior on recycled aggregate concrete, the selection of replacement rate and mix composition on recycled aggregate concrete. Specifically, the influence of a shrinkage reducing admixture(SRA) and recycled aggregate concrete was investigated. The shrinkage reducing admixture substantially reduces free, shrinkage and restrained shrinkage cracking while providing similar mechanical properties. Restrained shrinkage experiments were developed and shrinkage cracking was shown to be size dependent and recycled aggregate replacement rate. A mechanical properties experiment approach was developed to predict the behavior of a variety of recycled aggregate concrete specimens. This experimentally approach was used to successfully explain experimental results from a variety of mixture compositions and recycled aggregate concrete. This experiment was used to demonstrate the influence of material and structural properties on the potential for cracking.
구봉근,김유식,라재웅,주봉철,김창운 충북대학교 건설기술연구소 1999 建設技術論文集 Vol.18 No.2
This study will make reinforced concrete beams using recycled aggregates, and make an analysis of characteristics by experiment. First, this study will compare and consider characteristics of mechanical behavior for the rate of recycled coarse aggregate substitution. Second, it will look into effects of the shear span to depth ratio (a/d). Also, it will present appropriate methods of appraisal for reinforced concrete beams using recycled aggregates, through comparing experiment values with prediction values of specification, because of supporting basic data for real design. Major experimental variable was the shear span to depth ratio, which was changed from 1.5 to 3.0. For each case of variables, the rate of recycled coarse aggregate substitution was changed to 0, 30, 50, and 100 percent. The total sixteen specimens were producted and tested. From the analysis of the test data, the following conclusions can be drawn: Generally, reinforced concrete beams using recycled aggregates were showing a similar tendency with reinforced concrete beams using broken stones about shear behaviors. So it can be applied to real structures. Using recycled aggregates decreased in diagonal shear strength (V_c). Because Diagonal cracks appeared at 74∼79% of ultimate shear strength, but in the case of using broken stones, diagonal cracks appeared at 82% of ultimate shear strength. Shear beams under 2.0, that's value of a/d, ware sin the failure mode of deep beam. So definition of deep beam is appropriate it under 2.0, that's value of a/d, in the case of shear beams using recycled aggregate.
김영의,김태봉,구봉근,라재웅 충북대학교 건설기술연구소 1994 建設技術論文集 Vol.13 No.1
The fatigue tests were performed on the high strength concrete beams with single edged notch which was reinforced steel fiber. The steel fibers were used 1.0 percent by volume fraction and the lengths of the steel fiber were 30㎜ and 60㎜. These were tested consists of constant amplitude tests for different levels of loading. The test program included endurance limit with repect to flexural fatigue and relation of load-CMOD(crack mouth opening displacement). The results of test, it was found from S-N curve that the fatigue strength for a life of 2 million cycles of load was approximately 70 percent with respect to the static ultimate strength. And the static strength of SFRC after fatigue test was increased average 27% than the static strength that had been not fatigue loading. It is because strain hardening of steel fiber.