Applied Mechanics and Materials Vols. 166-169

Abstract: Introduces common of housing construction damage that result from crack, and analyzes main cause result in housing crack, then discusses how to ascertain cracks’ cause of formation in terms of crack form, and take what proper measure to prevent different cracks of housing construction.

Abstract: Area loss of severely weakened rebar cross sections is a crucial variable in assessment of structural deterioration for corroded concrete structures, which is hard to be measured or estimated precisely in conventional methods. In this paper, rebar samples were taken from naturally corroded RC slabs. Their virtual models were built using 3D laser scanning technique to facilitate geometric measurement. From these models seriously weakened sections were screened out as analyzing samples, and residual areas as well as profiles of the cross-sections were derived and investigated consequently. Shown by the results, corrosion was non-uniformly distributed on rebar surface, and profiles of the residual cross-sections can hardly be formulated efficiently. However, they can be simplified into ellipse with minor axis of minimum residual diameter and major axis of diameter in perpendicular direction. This model has been proved to give an conservative approximation of residual sectional area with 4.27% underestimation and 89.2% degree of confidence.

Abstract: The fatigue damage evolving model of brittle materials for one-dimension stress status, as the critical damage DC unequal to 1, was established with damage mechanics theory. And also a new fatigue damage evolving reliability model was established based on the supposition of the fatigue life obeying the normal distribution ,which was verified by fatigue experiments taking the semi-rigid base material for example ,and the propagate life can be ignored .The value of damage variable Dp corresponding to any given probability p can be effectively calculated ,the results show that D was a random variable, the method that to determine the damage of materials and to estimate the security of structures with the damage value D calculated by traditional determinate damage evolving model may cause a mistake that the damage could be evaluated out as a much smaller value and the potential danger of structures could be completely covered up.

Abstract: The effect of the temperature and immersed time of the alkali solution on the impact toughness of the adhesively bonded steel single lap joint under impact loading is studied using the experimental method. The results obtained show that the impact toughness of the specimen increased when the immersed time increased then it decreased as it beyond 3 days. When the immersed time is longer than 72 h, the higher the temperature is, the lower the impact toughness of the joint. The moisture absorption of the adhesive layer with the immersed time was also investigated and it was found that there is a relationship to the impact toughness of the adhesively bonded single lap joint. The epoxy adhesive layer was analyzed with FT-IR and it was found that the hydroxyl enhanced and bonding strength may increase after 72 h immersed in alkali solution.

Abstract: Due to the dependence of the sample data for a probabilistic reliability model and the fuzzy model, the interval model was used to describe the uncertain parameters through which a new measure of non-probabilistic reliability was established. Studying the model with the non-probabilistic theory, a new measure of non-probabilistic reliability was established which was the minimum distance between the failure region and the total region constructed by all uncertain variables. This kind of measure not only is consistent with the criterion of the non-probabilistic robust reliability, but also has a clearer meaning. The validity and the feasibility were proved through a computational example.

Abstract: In this paper variance of preformance function is calculated according to law of covariance propagation and matrix algorithm is used to calculate reliability index of structures in generalized random space, which is applicable to independent and correlative random variable, linear or nonlinear limit state equation. The given example has shown that the proposed method is very simple and convenient.

Abstract: In order to analyze the uncertainty existing in the stability of slope with geocell, the fuzziness of soil property parameters should be considered. In this paper, probability density function of structural performance function and membership function of the stability of slope with geocell was determined. The fuzzy reliability model of the stability of slope with geocell was established. The fuzzy reliability and fuzzy failure probability of slope with geocell instability were calculated, and the practicability of the calculated model was verified.

Abstract: For concrete structure lack of enough durability due to corrosion by chloride ion under chlorine salt environment, and based on the Fick’s Diffusion Law, a mathematical model for concrete corroded by chloride ion diffusion is established and studied. Based on Galerkin FEM with weighted residuals, numerically discrete analysis of the models and final finite-difference-discrete format about time are obtained. Comparisons of PDE models between traditional heat conduction and chloride ion diffusion have been done. According to different parameters and APDL in ANSYS, a program for transformation of parameters including initial and boundary conditions is designed, so as to solve modeling by resolving module of heat conduction in ANSYS. A two-dimensional example from references, namely a concrete plate corroded by chloride ion under chlorine salt environment, is analyzed. All the results show the investigation is reliable and feasible for the research of durability of concrete structure under corrosion environment.

Abstract: Basing half-cell potential method estimating steel corrosion rate in concrete was studied in this paper. The exponential relationship between the corrosion current and the corrosion potential was regressed by the data collected from the linear polarization method experiment. Potential collected by the half-cell potential method and linear polarization resistance method in the experiment were close, it is reasonable to using regression equation. Regression equation was applied to analysis steel corrosion rate in a concrete structure column.

Abstract: Surface cracks are the most common defects in structures. Ultrasonic has been widely used as a non-destructive evaluation technology in the case of crack characterization. In this investigation, surface waves are applied to a steel block with artificial slots to characterize the crack depth. A series of test specimen with different depths of surface crack ranging from 4mm to 10mm was fabricated. The depth of the surface crack was evaluated using the pitch-catch ultrasonic technology. In this work, 2.25 MHz, 5 MHz and 10 MHz of incident waves were employed to investigate the effect of frequency on the crack depth detection. Experimental test results show that the accuracy of crack depth detection is increasing with the increase of frequency.