Applied Mechanics and Materials Vols. 166-169

Abstract: Chloride diffusion coefficient is significant to the durability of pre-stressed concrete in chloride environment. The factors which influence chloride diffusion coefficient in pre-stressed concrete structures eroded by chloride ion is of great importance, including porosity, chloride ion binding capacity and the stress of pre-stressed concrete etc. Based on the Fick’s second law and existing models, the model of chloride ion diffusion in pre-stressed concrete with sulfate attack is established. It is analyzed that the influence of water-binder ratio and sulfate ion concentration and erosion time on concentration distribution of chloride ion in concrete. Compared to test data and project examples, it is confirmed that the model is useful.

Abstract: In order to analyze the influence of stochastic pitting corrosion to the reliability of service structure, According to the theory of extreme values of random variables and the basic theory of reliability analysis, the reliability of flexural concrete member based on the randomness of pitting, the change of statistical parameters for both corroded steel bar and resistance is also analyzed based on the randomness of pitting. Based on the checking point method, the development law of reliability of concrete bending members with the number of random variables and the service life are studied. The results indicated that the influence of the randomness of pitting to the reliability of flexural concrete members is of the most significance, the reliability index was found to decline with the increase of number of random variables and the service life. The analysis show the research presented in the paper can provide theoretical basis of life prediction.

Abstract: According to investigations of apparent surface chloride contents and chloride penetration profile of concrete structures exposed to chloride environment, the influences of boundary and initial conditions, geometry parameters such as the geometry dimension and section shape, etc. were discussed. Based on the Fick’s second law of diffusion and different boundary and initial conditions, different analytical models to predict the chloride penetration profile in concrete structural members with different boundary and initial conditions were derived. Some calculations examples were made using those analytical models. Computational results show that the boundary and initial conditions have remarkable influences on chloride penetration profile and service life time of concrete structures. Using prevailing error-function solution model based on the semi-infinite assumption of chloride ingress, the prediction of service life time of concrete structures are over evaluated, in particular for the steel reinforcement in corner of the section. Some modify coefficients should be taken into consideration, concerning the influences of boundary and initial conditions.

Abstract: Purpose: to assess reliability factor of Gable Framed Lightweight Steel Structural and Components, under combination of load effect of permanent loads and snow loads. Method: JC method is adopted in the calculations. From reliability of geometrical meaning, transform the solving of reliability problem into the finding of minimum constraints, and calculate reliability indicators by using a non-linear programming called ‘Lingo’ software. Results: based on dead load plus snow load, and combination of dead load plus snow load and wind load, to calculate reliability indicator of structural components under axial tension, axial compression, and eccentric compression. Conclusion: when combined with snow load, reliability indicator (of Gable Framed Lightweight Steel Structures and Components) is less than the standard permitted reliability indicator, which is beta=3.2.

Abstract: Many before studies showed that it was difficult to ensure the accuracy of assessing the amount of steel corrosion in the cracking concrete with artificial neural network [3] method while the study sample size was small. This paper introduces several different algorithms to assess the amount of steel corrosion in concrete. The experimental results show that compared with other algorithms, the predictive value of the support vector machine algorithm is the closest to the measured value.

Abstract: For long-span pre-stressed concrete continuous box girder bridges, cracks and other damage problem are often found because of influence of loads, climate, operations management and other factors during operation. The problem of cracking is serious increasingly, which has a direct impact on usability, durability and security. In order to analyze the bearing capacity of the bridge with cracks under different parameters, such as cracks width, cracks height and cracks spacing and provide the basis for the safety assessment and reinforcement, the paper puts forward the cracking reduction coefficient that evaluates the bearing capacity of the damaged bridge based on the tensile stress control. A three-span continuous rigid frame bridge is analyzed and the result shows that the bearing capacity of the bridge is in inverse proportion to cracks width and cracks height. The bearing capacity of the bridge is in direct proportion to cracks spacing.

Abstract: To enhance the effective of the land in mining subsidence areas, realize the development of new rural construction and urbanization. According to the geological and mining conditions, the scale, shape and regularity of the potential crack areas in the coal goafs, separated overburden strata, and the influencing factors which affect the deformation foundation of architecture and stability are studied. Probability integral method is used to establish the further deformations formula of the building foundations in mining subsidence areas. The monitoring data from the ground observation stations are used to invert the further deformation predicting parameters, the surface further deformations of each coal goafs, and the whole surface’s further deformations are calculated by the superposition method. The foundation further deformations, geological structures, etc, are comprehensively taken into consideration. The stability of the building foundations in mining subsidence area are analyzed and evaluated. Research results are very valuable to process, design, and plan the foundations of the buildings in coal mining subsidence areas.

Abstract: This paper analyzes the cause and effect of the influence which the change of concrete strength have on the reliability through carrying capacity test of six CFRP repaired and strengthened beams that are different in concrete strength grade. The reliability of CFRP reinforced RC beams increase gradually along with the enhancement of the concrete strength, , and this trend becoming more apparent when the concrete strength grade raise.

Abstract: The numerical model was established using ANSYS software, which took the interaction effect of subsoil and structure into account, the soil was considered as discrete spring elements. The soil’s mechanic parameters were set as random variable, probability analysis was performed on typical construction course of open caisson by Monte-Carlo method, the distribution rule of displacement random variables and their sensitivity to variable factors were studied, and the influence of uncertain factors on open caisson’s sinking attitude was investigated. The analysis model showed good practical value for controlling construction course of open caissons.

Abstract: The main reason that causes the premature failure of concrete structure is rebar corrosion damage. Furthermore, the chloride ion penetration is the main reason of rebar corrosion damage. Stress corrosion in welding joint of rebar is studied. Separate rebar into 5 groups, each group have 3 pieces. Grouping experimental method is used to make welded joints soaked, compare the variation law of mechanical properties of flush welded joint under the influence of corrosive environment. Combining with Finite Element Analysis shows that a higher stress concentration during welding process is the important reason to the performance degradation of rebar in corrosive environments. Comparative tests have shown that stress corrosion cracking more likely occur in the welding zone and welding clamping position. The results show that the rebar production process must be strictly controlled, and effectively prevent the erosion of the corrosive medium to ensure the long-term safety of the building.