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Tang M.-X.,Guangzhou Institute of Building Science | Chen X.-B.,Guangzhou Institute of Building Science | Chen X.-B.,Central South University
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2010

The cover cracking process of rebar corrosion expansion in reinforced concrete was analyzed with cylindrical cavity expansion theory, and animation model was set up for this cover cracking process. By the animation model, the radius and pressing stress analytic equations on plastic zone borderline were deduced respectively for different rebar corrosion ratios in reinforced concrete. Based on cylindrical cavity expansion theory, the critical rebar corrosion ratio ρ(t) for reinforced concrete rebar corrosion cover cracking was presented with the rust counting model and the main factors' effects on this the critical rebar corrosion ratio ρ(t) model's properties were theoretically analyzed. The results show that the critical rebar corrosion ratio ρ(t) is directly relative to the concrete strength grade, relative covering depth and rust expansion rate. The critical rebar corrosion ratio ρ(t) increases quickly as the relative covering depth increases, the critical rebar corrosion ratio ρ(t) decreases quickly as the rust expansion rate increases, and the critical rebar corrosion ratio ρ(t) increases slowly as the concrete's strength grade increases. This animation model presents the basic theory for the concrete cover rust expansion cracking life prediction of Chlorides or carbonization aggression. Source

Xu M.-J.,South China University of Technology | Xu M.-J.,Guangzhou Institute of Building Science | Wei D.-M.,South China University of Technology
Journal of Donghua University (English Edition) | Year: 2010

Considering compression of solid grain and pore fluids, viscous-coupling interactions and inertial force of fluids, dynamic governing equations for unsaturated soils are established by adopting an exact constitutive formula of saturation. These equations are highly versatile and completely compatible with Biot's wave equations for the special case of fully saturated soils. The governing equations in Cartesian coordinates are firstly transformed into a group of state differential equations by introducing the state vector. Then the transfer matrix for layered media are derived by means of a double Fourier transform. Using the transfer matrix followed by boundary and continuity conditions between strata, solutions of steady-state dynamic response for multi-layered unsaturated soils are obtained. Numerical examples show that the echoes generated by boundary and stratum interfaces make the displacement amplitude of the ground surface fluctuate with distance; the relative position of soft and hard strata has a significant influence on displacement. Copyright © 2010 Editorial Department of Journal of Donghua University. All rights reserved. Source

Yan L.-W.,Sun Yat Sen University | Chen S.-H.,Sun Yat Sen University | Li S.,Guangzhou Institute of Building Science | Cheng Y.,Sun Yat Sen University
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2010

An improved generalized genetic algorithm was proposed here. A heterogeneous strategy was introduced to increase population diversity and avoid premature convergence. This algorithm was applied to the robust optimization problems of structures under complicated loading. The objective function of the generalized genetic algorithm was constructed by using the signal-to-noise ratio of Taguchi target. Numerical examples demonstrated that the heterogeneous strategy can raise the convergence probability of the global optimal solution and speed up the process of convergence; combined with the robust design method, the improved generalized genetic algorithm can effectively solve the robust optimization problems of structures with uncertain parameters under complicated loading. Source

Chen X.-B.,Central South University | Chen X.-B.,Guangzhou Institute of Building Science | Xu W.-G.,Central South University | Liu X.-P.,Hunan University
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2011

The rainfall infiltration mechanism analysis for the granular soil embankment was executed, and the metric suction and shearing strength was generalized when the grain diameter were fixed. The law for granular soil's metric suction and shearing strength attenuation was obtained and the rainfall infiltration depth calculation formulas were discussed. According to unsaturated soil's strength attenuation law, the strength discount method was used for the rainfall infiltration effects simulation, and the embankment additional settlement and stability debasement resulting from rainfall infiltration was stimulated by the embankment numerical computation model. The computation results show that rainfall infiltration has effect on the embankment additional settlement, and the additional settlement increases with the increase of the infiltration depth incensement. While the first time infiltration depth reaches 2 m, the additional settlement can reach 1.30 cm. The embankment stability is obviously affected by rainfall infiltration, which expands the plastic zones in the embankment numerical model and thus reduces the stability coefficient. Source

Song B.,South China University of Technology | Song B.,Guangzhou Institute of Building Science | Cai J.,Guangzhou Institute of Building Science
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

To determine the side rock resistance of pile more accurately, the composing and the influence factor of it need to be researched. The mechanism of friction and adhesion between pile and rock is analyzed. It is pointed out that pile-rock interface strength is different from rock shearing resistance; the ultimate side rock resistance of pile is determined by the weak one between pile-rock interface strength and rock strength. Four groups of compression and uplift comparative tests for concrete short piles in medium weathered rock are accomplished. The value of ultimate side rock resistance and the resistance ratio of uplift test and compression test are obtained. Because the upper rock restriction to the rock connected with pile is weaker in uplift test than in compression test; the side rock resistance in uplift test decreases distinctly comparing with the result of compression test. ADINA software is used to analyze the test piles. By comparing the calculated value of ADINA program with the test value, the interface strength condition of pile and rock is analyzed. It is discovered that the ultimate side rock resistance of test pile is determined by the pile-rock interface strength; and the interface adherence force is the main part of interface strength. Source

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