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유한요소 모형을 이용한 연속철근 콘크리트 포장의 균열 전파 특성분석
조병휘 경희대학교 대학원 원우회 2007 高凰論集 Vol.40 No.-
In previous studies on the behavior of transverse crack in continuously reinforced concrete pavement (CRCP), the cracks have been assumed to be through cracks. The analysis methods used in those previous studies, however, have a lack of predicting and understanding of the actual crack behavior of CRCP. Therefore, in this study, a structural analysis method to predict crack propagation in CRCP under environmental conditions was developed using a finite element model, and the crack propagation process was investigated. Three different thermal loading conditions were considered. The analysis results show that transverse cracks do not always pass through a slab completely and the aspects of crack propagation depend on the types of thermal loads.
DIC 기법을 통한 산화그래핀 혼입 PVA 섬유보강 시멘트 복합체의 휨거동 특성 분석
조병휘,정성균 한국도로학회 2023 한국도로학회논문집 Vol.25 No.3
PURPOSES : The purpose of this study is to experimentally analyze the flexural strength characteristics of cement mortar mixtures simultaneously incorporated with graphene oxide (GO) and polyvinyl alcohol (PVA) fibers, and to understand the composite effect of those on enhancing resistance against the initiation and progression of micro-cracks, as well as the control of macro-cracks in flexural behavior. METHODS : Cement mortar(w/c=0.5) specimens for flexural strength test, mixing 6 mm and 12 mm PVA fibers at 1% and 2% volume ratios, were fabricated. Additionally, specimens incorporating GO at a cement weight ratio of 0.05% were prepared for each mixture to analyze the effect of GO. Therefore total eight types of mixture were prepared. The fabricated specimens were subjected to flexural strength tests after curing in waterbath for 7 and 28 days. Concurrently, digital images for analyzing deformation in accordance with loading history were obtained at a rate of 20 Hz using the DIC technique. Through displacement and strain calculation via DIC, the flexural behavior characteristics of the mixtures combined with GO and PVA fibers were precisely analyzed. Furthermore, the composite effect on flexural behavior characteristics when GO and PVA fibers are incorporated was discussed. RESULTS : For the PVA fiber-reinforced cement mortar mixture, the incorporation of 0.05% GO increased the crack initiation load by up to 23%, and the maximum resistive load after cracking by up to 24%. Moreover, introducing GO into the PVA fiber-reinforced mixture increased the flexural strain just before cracking by approximately 30 to 50%, while the maximum resistive load after cracking exhibited similar strain levels with or without GO incorporation. Therefore, under flexural behavior, the integration of GO might delay crack initiation by increasing the strain concurrent with the rise in flexural stress before crack occurrence. It also seems to contribute to reducing crack expansion by synergistically interacting with PVA fibers after crack occurrence. CONCLUSIONS : It was experimentally examined that the flexural strength of PVA fiber reinforced cement mortar is improved by incorporating GO. Moreover, GO enhances resistance of crack occurrance and reduces crack propagation in combination with PVA fibers. This study suggests that simultaneous incorporation of GO and PVA fibers can synergistically improve the performance of cement composites.