Applied Mechanics and Materials Vol. 711

Abstract: To explore the effect of concrete cracks on chloride erosion, different dry-wet cycle immersion experiment for bending cracking component is designed. The chloride content in concrete is tested by using the method of RCT in simulated marine environment. It is showed that the chloride convection diffusion zone depth in the cracking component is between 15mm and 25mm. The chloride erosion process is accelerated by macro-cracks. According to experiment result, a new chloride time-dependent diffusion model is put forward, considering crack width and effective diffusion coefficient. It is found that the chloride concentration is increased with the increase of crack width, approaching to the saturated concentration.

Abstract: The choice of input ground motion in the evaluation of the seismic response is a complicated task. The ground motion parameters need to be determined by the scope of the analysis and the potential damage of new or existing buildings. This work presents nonlinear dynamic analyses on reinforced concrete frame widely present in China. Input ground motions contain uncertainty and variability comes from both natural recordings and modified ones. Magnitude scaling and spectrum matching are used in this study. Nonlinear dynamic analyses of reinforced concrete buildings simulated by SeismoStruct and OpenSEES are carried out to evaluate the seismic response. Findings from the investigation indicate that spectrum matching is generally stable and shows good performance in response prediction.

Abstract: Based on the existing studies about chloride ion erosion in prestressed concrete structures, this paper intends to discuss the effects of the stress level and environment factors (including temperature and humidity, etc.) on chloride ion diffusion under marine atmosphere zone. The investigation from pre-stressed concrete crossbeams which service for 39 years in Lianyungang Port shows the chloride ion concentration distribution and chloride ion diffusion. According to the chloride ion concentration distribution, it finds that chloride ion concentration values in pre-concrete structures is C_max,1> C_max,2. In addition, the free chloride concentration distribution values go down smoothly after the second peak. Therefore, the result shows that the improved model can be used in marine atmosphere zone.

Abstract: The article deals with the issue of wooden buildings in terms of their critical details. Specifically, the details such as the bottom corner in connection with the foundation and the external wall corners or at the level of spatial bracing. Incorrectly performed details may considerably affect the properties of the whole structure both in terms of thermal technical engineering and mechanical stability. In particular, the condensation of water vapor in the construction may cause serious problems.

Abstract: Five conventional tests (Shapiro-Wilk test, Kolmogorov-Smirnov test, Cramer-von Mises test, Anderson-Darling test and Chi-Square test) were carried out in this paper to learn the probability distribution of fracture energy of FRP-concrete interface under the environment of dry-wet cycling at high temperature. The relationship between interfacial fracture energy and the number of cycles was established through nonlinear regression analysis. Then the reliability index and the probability of deterioration of FRP-concrete interface that uses experimental data as design values were analyzed according to the reliability theory. It is shown that the optimum distribution of interfacial fracture energy is lognormal distribution, and the relationship between logarithmic mean value of interfacial fracture energy and number of cycles is subject to the exponential function. As the cycle number increases, reliability index decreases rapidly while the probability of deterioration the other way around in the beginning, yet both are stabilized at a certain level eventually. The probability of deterioration has reached a high value in a few cycles in experiments.

Abstract: The determination of post-tensioning cable forces is one of the most important issues for the design of arch pylon cable stayed bridge. In this paper, the optimization module implemented in MATLB, together with the commercial finite element software MIDAS, were employed to evaluate the minimum bending strain energy of the bridge. After optimizing the cable forces, the bending moment of the pylons were bigger than the values of original design. The bending moment of the main arch pylon within 55m to 70m height increased by 7280 kN•m, and the bending moment of the auxiliary arch pylon within 30m to 60m height increased by 3926 kN•m .The stress of the pylons was still far below the allowance value when the obtained cable forces were applied. However, for the girder, the difference between the maximum positive and maximum negative bending moments due to dead load can be lessened greatly by the application of the obtained cable forces. The results obtained revealed that the method presented could make full use of cable forces and lead to optimal structural performance.

Abstract: In recent years, many approaches were proposed to deal with the settlement prediction problem. However, because of the complexity of geography and other conditions, the current solutions still have some deficiencies and do not work well. To improve the accuracy of settlement prediction, the authors of this paper propose an extended BP network-based approach. This method first designed the model of BP network according to the dataset. This network includes one input layer, one output layer, one middle layer and an extended middle layer. After trained by samples, this network is used to predict the settlement value. The experiment indicates that our approach is available and work well in most situations.

Abstract: To further investigate the mechanism of the interaction between the response of single pile and pile-soil on the condition of lateral load, on the basis of the normal type of the coefficient of subgrade reaction, this paper reaches the transfer matrix solution of single pile subject to lateral load by combining matrix transfer method with finite element method assuming that the coefficient of subgrade reaction is constant in each finite element. With the matrix solutions obtained, a computer program is developed using MATLAB to compute the pile responses and parametric studies are carried out on the effect of the constraint conditions of pile head and tip, effect of soil properties etc. and the results are discussed in detail.

Abstract: Based on the open excavation area from Yulu Station to Wulidian Station in Chongqing subway circle lines, the finite element software Ansys was used to establish three-dimensioned model to calculate and analyze the mechanical characteristic of the pile-support supporting. By simulating the construction process of subway tunnel, the characteristics of supporting structure were analyzed from the stress and displacement of pile and supporting. It can summarize that the internal force characteristics of pile-support supporting conform to the requirements of the construction safety.

Abstract: Shield tunning method has been used widely in urban underground engineering. Based on a certain range of Wuhan subway shield tunnel, the subway shield tunnel segment of the internal force and deformation were studied by the load structure method and stratum structure method. Influence of the formation parameters and the parameters of the lining structure on the segment internal force and deformation was analyzed. And the tunnel construction was modeled by three-dimensional dynamic finite element method. The influence of the construction process about ground subsidence and segment stress was discussed, in order to guide urban subway tunnel construction design.