Papers by Author: Cheng Yi

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Authors: Hong Guang Zhu, Yao Dong Jiang, Cheng Yi, He Ping Xie
Abstract: The cubic law (CL) is one of the most commonly applied physical laws for flow through rock fractures and fractured media, but many studies indicate that the CL is often not adequate. We investigate the establishment conditions of valid applying the “cubic law” to flow in fractures. A dimensional analysis of the N-S equations yields three conditions for the applicability of cubic law, as a leading order approximation in a local fracture segment with parallel walls. These conditions may not be met in many natural rock fractures as whole and demonstrate that the “cubic law” should be exactly applied in local segments (local cubic law, LCL). In this way, a new 2D discrete equivalent model for natural rough fractures is introduced, and its equivalent aperture and flow formulation are derived. By comparing the developed model and experimental results of different fractures, good accuracy was found, and the model was validated. The model could be useful for theory studies of flows through real rock fractures.
Authors: Cheng Yi, Meng Lan Lin, Fu Yan Sun, Hui Xin Liu, Jing Guo, Yu Kun Hu, Shou Yuan Man
Abstract: In this paper, the rule of index weight is determined by analyzing the existing rules of life assessment for concrete. Based on fuzzy decision making of binary comparison, the weight of different factor taking effect in complicated environment can be analyzed. With known effects of each factor, the classification and score of concrete durability can be made. Thus the assessment of concrete durability in complicated environment can be modeled. The model is used to predict the service life of concrete and provide optimize mix proportion design.
Authors: Cheng Yi, Jing Shi, Xiao Long Zhao, Wen Hai Zhao, Qiang Liu, Hui Xin Liu
Abstract: As pointed out in this paper that, for a common building material, it is relatively difficult to judge its green degree in comparison with that for a special function material because the judgment factors are comprehensive. The relevant factors which affect the greenness index such as physic expenditure, pollution, economic are analyzed and all influential factors are discussed. For the common building materials, their different inter-restrain factors are divided in administrative level and the weight of factors is determined according to the AHP theory. Meanwhile, the assessment scale and criteria for the factors, and the grading standard for the material green degrees are given in the paper. Based on the fuzzy comprehensive evaluation theory, a green degree evaluation model is established. Finally, the reasonability of the model is testified with the instances introduced in the paper.
Authors: Yan Liu, Cheng Yi
Abstract: Micro-crack defects in concrete can affect the Chloride ion permeability of concrete in a certain extent. In the paper, the splitting experiments of concrete specimens from the four different dimensions are carried out in order to build the even damage fields. The displacements of the concrete specimens’ surface are analyzed through DSCM (Digital Speckle Correlation Method). Therefore damage parameters are determined that are damage area based on the MCOD (Micro-Crack Opening Displacement) and damage variable DE based on the weighting-damping elastic modulus. At the same time, Clˉ permeation of concrete specimens before and after the splitting test are studied by NEL method, and Clˉ diffusion coefficients D are recorded in detail. Further relationships between damage parameters and diffusion coefficients of Clˉ are discussed.
Authors: Cheng Yi, Shi Zhao Shen, He Ping Xie, Chang Jun Wang
Abstract: Partially High Percentage Fiber Reinforced Concrete (PHPFRC) is a kind of cement composite in which fibers are concentrated with high volume fraction in the tension region of the component under bending. Therefore, PHPFRC possesses much higher load bearing capacity, rigidity, fatigue and fracture properties than conventional steel fiber reinforced concrete (SFRC) while its cost is similar to that of SFRC. In this paper, the fatigue test of PHPFRC is carried out to gain its flexural fatigue damage evolution rule. It is found from the test that, PHPFRC have long post-crack fatigue life and its fatigue damage is tough damage. Based on the continuum damage mechanics and fatigue behavior of the specimens, a fatigue damage variable D for PHPFRC is defined and the elementary form of damage evolution function is determined. For the specimens in which average fiber volume fraction are 1.2% and local fiber volume fraction are 10%, the function parameters and the damage threshold value are given according to the test results.
Authors: Xin Zheng An, Cheng Yi, Rui Xue Du
Abstract: The analyses of concrete from a bridge in Handan district shows that most bridges concrete should have cracked. The study of the technical measures against the performance deterioration of existing reinforced concrete bridges will undoubtedly become an imperative issue. In recent years, lots of bridges have been built in Handan. We choose a reinforced concrete bridge to investigate the effect of the effective member stiffness degradation and durability degradation induced by vehicle overload, vehicle overflow, rebar corrosion, and concrete deterioration on highway reinforced concrete bridges. And Static loading test was conducted at its middle span. Based on the test data in different circumstances, the seriousness of vehicle overload is discussed. In consequence, the performance of highway reinforced concrete bridges on stiffness degradation and durability degradation is more serious compared with the bridge under the condition of non-overloading. The results show that the process of rebar corrosion in highway reinforced concrete bridges is sped up under the condition of vehicle overload and vehicle overflow on the highway reinforced concrete bridges, which decreases the durability of the bridge structure, and the speed of the durability degradation increases as time goes on. The paper conclusion is instructive for the construction and maintenance of bridge.
Authors: Wen Li Li, Wen Ge Chai, Cheng Yi, Yan Li Gao, Zhao Guang Li
Abstract: In this paper, high-quality mineral admixtures and superplasticizer double mixing technology is used to produce high performance recycled concert (HPRC), and then steel fibers are used to modify the characteristics of HPRAC. The compressive strength, splitting tensile strength, ultimate bending load and fracture energy of HPRC with different content of steel fiber. Experiments suggest that with the increase of steel fiber content, the compressive strength doesn’t change too much, but the splitting tensile strength, ultimate bending load and facture energy increase dramatically. Therefore it can be concluded that increasing the content of steel fiber properly can improve the ductility and resistance to crack propagation of HPRC and enhance the ultimate load of HPRC bending member.
Authors: Cheng Yi, Jun Yi Huang, Fu Yan Sun, Meng Lan Lin, Qiang Liu
Abstract: According to the idea of the life cycle assessment method (LCA), the consumption of the energy and material, which is involved in the whole life cycle in each phase of single green construction technique, and the impact on the environment, is discussed. Based on the fuzzy comprehensive evaluation theory, a green degree evaluation system is established. The Analytic Hierarchy Process method (AHP) is adopted to establish green assessment system of the hierarchical structure model, and by means of 10/10-18/2 scaling method through pairwise comparison on tectonic judgment matrix of each level, the weight of each affecting factor is ultimately determined. Finally, VB program is used to compile visual programs of green degrees assessment. The quantitative assessment of integrated green degree for green construction technology is obtained, after inputting the score of the corresponding index, with reference to the influence of the factors assessment standards. By verifying rationality of the assessment system, the study proves that the system plays a guidance role in the self-assessment and reasonable construction for the construction of green technology.
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