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RISS 인기검색어
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- 저자 : Dawang Li (검색결과 3 건)
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Early age behavior analysis for reinforced concrete bridge pier
Xianfeng Wang,Dawang Li,Ningxu Han,Feng Xing 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.5
In this study, the construction of a reinforced concrete bridge pier was analyzed from durability point of view. The goal of the study is to analyze the crack iniation condition due to construction and present some recommendations for construction conditions of the reinforced concrete bridge pier. The bridge is located at the western port area of Shenzhen, where the climate is high temperature and humidity. To control the cracking of concrete, a construction simulation was carried out for a heat transfer problem as well as a thermal stress problem. A shrinkage model for heat produced due to cement hydration and a Burger constitutive model to simulate the creep effect are used. The modelling based on Femmasse© is verified by comparing with the testing results of a real underground abutment. For the bridge pier, the temperature and stress distribution, as well as their evolution with time are shown. To simulate the construction condition, four initial concrete temperatures (5°C, 10°C, 15°C, 20°C) and three demoulding time tips (48h, 72h, 96h) are investigated. From the results, it is concluded that a high initial concrete temperature could result in a high extreme internal temperature, which causes the early peak temperature and the larger principle stresses. The demoulding time seems to be less important for the chosen study cases. Currently used 72 hours in the construction practice may be a reasonable choice.
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Tielin Han,Xianfeng Wang,Dawang Li,Ningxu Han,Dongfeng Li,Feng Xing 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.S1
The effects of different dosages of microcapsules, proportion of prepressing stress and curing days on the mechanicalproperties, pore structure and healing efficiency of the specimens were studied through uniaxial compression test and mercuryintrusion porosimetry (MIP) test. The results indicate that the uniaxial strength of the specimens decreased to a certain extentwith an increase of dosage of the microcapsules. Meanwhile, the pore structure parameters (pore volume; porosity; criticalpore size; capillary porosity), as well as the self-healing rate and recovery rate of the mechanical properties increased withincreasing the dosage of microcapsules. The microcapsules have a significant influence on the deformation characteristics ofthe specimens and may improve the brittleness characteristics and strengthen the ductility of the ordinary concrete.
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Molecular dynamics study on mechanical properties of C-S-H composites
Xianfeng Wang,Peng Wei,Rui Han,Wei Xie,Taoran Li,Dawang Li,Yonggang Peng,Zhen Chen,Feng Xing 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.S1
In this paper, the mechanical properties of calcium silicate hydrate gel (C-S-H) are investigated with molecular dynamics (MD)simulations, in which the Tobermorite 9Å, Tobermorite 11Å, Tobermorite 14Å and Jennite crystals are treated as fundamentalmodels of the C-S-H nanostructure. The initial structures of the crystal models are firstly preprocessed and optimized, andthen are simulated in the canonical (NVT) ensemble conditions. The orthotropic elastic constants of the C-S-H nanostructureare determined and used to derive the bulk and shear moduli via the Voigt-Reuss-Hill method. The self-consistent, Mori-Tanaka, and Voigt methods are employed to compute the mechanical properties of various mixtures of C-S-H composites withdifferent porosities. The simulated results are found to be in a reasonable agreement with those obtained from nanoindentationtests, while the result obtained from the Mori-Tanaka method appears to be the closest to the experimental one. It could also be observed that the mechanical properties of C-S-H vary within a certain range as the porosity and proportionsof the components change.
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