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Yang L.,Guangxi Communications Planning Surveying And Designing Institute | Zeng X.-C.,Nanjing University of Aeronautics and Astronautics | Yu H.-F.,Nanjing University of Aeronautics and Astronautics
Construction and Building Materials | Year: 2015

Abstract A new quantitative method is introduced to depict the micro-cracks in the concrete - crack density, which is closely related to the number and the size of the cracks in concrete. According to the experimental data and relative corrosion depth, the data analysis and numerical simulation are conducted by the scientific plotting and data processing software SigmaPlot 12.0 to the damage process, which can produce the three-dimensional distribution map of propagation of inner crack density of concrete. From the map we can see the formula and character on the propagation of micro-crack density of concrete in corrosive medium. In this paper, three types of concrete under the action of external stress and attack of sulfate was investigated. By analyzing the crack density, we can conclude: GHDC2 has the best stress corrosion resistance in four kinds of concrete; chloride can accelerate the chemical corrosion of magnesium and sulfate brine to concrete; tensile stress and compressive stress can obviously improve the appearance and propagation of micro-cracks. © 2015 Published by Elsevier Ltd. Source


Zheng G.,China Merchants Chongqing Communications Research and Design Institute Co. | Li G.,China Merchants Chongqing Communications Research and Design Institute Co. | Li G.,Guangxi Communications Planning Surveying And Designing Institute
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2013

Based on the three-component yield displacement model, and principal influence factors are analyzed considering the bending, shear and bar-slip deformations. New formulae with five coefficients and three coefficients are respectively proposed for the effective stiffness computation of bridge piers. The coefficients of the new formulae were calibrated with the pseudo-static test results of 75 model columns through regression analysis. The results show that the effective stiffness of bridge piers increases most consistently with axial-load ratio, longitudinal reinforcement ratio and aspect ratio, while decreases with an increase in the fydb/L√fc′. From the point of the average statistical meaning, existing formulae severely overestimate the effective stiffness of piers. Compared with the existing formulas for calculating the effective stiffness of piers, the proposed formulas agree well the test results and can provide higher accuracy and greatly reduce the degree and possibility of possible overestimation. Source


Cheng H.,Dalian University of Technology | Li H.,Dalian University of Technology | Wang D.,Dalian University of Technology | Sun Z.,Dalian Maritime University | And 2 more authors.
Bulletin of Earthquake Engineering | Year: 2016

Following the 1995 Kobe earthquake, many RC bridge columns were demolished due to a residual drift ratio of more than 1.75 % even though they did not collapse. The residual drift ratio is a quantitative index for the performance objective of reparability in the bridge seismic design. Numerical models of the columns are built to study the factors that influence the residual displacement of RC bridge columns. In these models, both column bending and bar pulling out deformation are considered using the fiber column-beam element and zero-length section element, respectively. Then, nonlinear time history analyses are performed. The factors that influence column residual displacement, such as the characteristics of ground motion, the structural responses (the maximum lateral drift ratio and the displacement ductility factor), and the structural characteristics (the aspect ratio and the longitudinal reinforcement ratio) are investigated. It is found that the near-fault ground motion induces a larger residual drift ratio than the far-fault ground motion. The residual drift ratio becomes larger due to the increase of the maximum lateral drift ratio, the displacement ductility factor, and the aspect ratio. Further, a larger longitudinal reinforcement ratio can induce a larger residual drift ratio due to the contribution of the bar pulling out deformation. © 2016 Springer Science+Business Media Dordrecht Source


Li J.,Hunan University | Feng X.-T.,Hunan University | Feng X.-T.,Guangxi Communications Planning Surveying And Designing Institute | Shao X.-D.,Hunan University | And 2 more authors.
Zhongguo Gonglu Xuebao/China Journal of Highway and Transport | Year: 2014

In order to solve the problems of early damage in bridge paving and fatigue crack in steel deck, a new super toughness concrete (STC) steel bridge paving system was presented and applied firstly to the Mafang Bridge, Guangdong Province. The effect of STC paving system was evaluated with the finite element analysis and the actual test. The results indicate that the paving stiffness of steel plate -STC composite structure is improved greatly, and the maximum strain and vertical displacement decrease by 46.82%-90.89% at each control point. Compared with the asphalt pavement, the new system is more effective. The tensile strength of the STC satisfies the required maximum stress of 7.97 MPa. STC paving system can effectively reduce the strain amplitude and vertical displacement of the bridge deck and improve the mechanical performance of paving layers, thus eliminating the risks of steel plate fatigue cracking, pavement cracking and rutting damage. Source


Pu C.-Z.,Central South University | Cao P.,Central South University | Yi Y.-L.,Guangxi Communications Planning Surveying And Designing Institute
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012

The compression test on rock-like specimens with two prefabricated transfixion fissures made by pulling out the embedded metal inserts in the precured period was done using the servo control uniaxial loading tester. Based on the sliding crack model, the fracture failure mechanism of the fissure body was analyzed combined with the stress-strain curve and the failure form of granule on the transfixion surface of the specimen. It was shown by the sliding crack model that: the effective shear, which drove the relative sliding, was a function of the fissure inclination angle (α) and friction coefficient (f) of the fissure surface. It was found during the test that: when the fracture failure of specimens occurred, according to the differences of the fissure and rock-bridge inclination angle, the transfixion failure of micro-cracks at the tip of the signal fissure, the transfixion failure of the prefabricated fissures and the brittle failure without micro-cracks would appear in turn on specimens; and according to the differences of the stress characteristics in the rock-bridge region, when the transfixion failure of fissures occurred, three forms would be shown: tension fracture, shear fracture and tension-shear combined fracture, and the failure forms of the granule on the transfixion surface in the rock-bridge region would present zero-friction, entire-friction and partial friction, respectively. Source

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