Applied Mechanics and Materials Vols. 71-78

Abstract: In this paper, a building canopy model is coupled with CFD for the analysis of microclimates within urban blocks under different urban and architectural planning. This model considers radiant heat exchange in the building canopy, water evaporation of vegetations and heat released from the air conditioning systems. Using this model, thermal environment of a real urban block is analyzed. The simulation results show that heat released from the air conditioning systems is one of the most important factors affecting outdoor thermal environment. Temperature of vegetation is significantly lower than that of road surfaces. However, air temperature difference is not great between zones with vegetation and other zones at 1.5m height.

Abstract: Base on the discussion of the wood-plastic composite cushion packaging material progress at home and abroad, this article analyzes foaming mechanism, process conditions and methods on how to improve interface compatibility in preparing WPC material. Point out that bubble quality control during the foaming nucleation stage, the proportion of the compound blowing agent, process condition selection and interface modification are the Key issues in research of the WPC cushion packaging material.

Abstract: In order to study the vertical pre-stressed girder under the action of perforation of the stress distribution characteristics, the paper simulated box beam web under the stress field affected by vertical pre-stressing forces using pairs of force acted on the long and narrow rectangular thin plate, deducted analytical solution to the vertical normal stress, and obtained the numerical solution through the least squares method. On the basis of the uniformity of vertical pre-stressing forces and stress level, the vertical pre-stress diffusive angle of the web fitting to engineering calculations was acquired. Through testing and finite element method simulating the vertical stress dispersive effect of the real bridge web, the result matched well with the deducted equation.

Abstract: This paper presents a nonlinear finite element (FE) analysis on the mechanic behavior of concrete filled steel tubular (CFST) composite frames. The main purpose of the FE analysis was to investigate the seismic behavior of composite frames. Three kinds of nonlinearity, namely material nonlinearity, contact nonlinearity and geometry nonlinearity, were taken into account in the FE model using MSC.Marc. The element type, connection between element, material constitutive law and boundary condition was described in detail. The elasto-plastic behavior, as well as fracture and post-fracture behavior, of the FE analysis models fitted well with those of the test specimens. The beam and panel zone deformation of the analysis models is also in good agreement with that of the test specimen. It is concluded that FE model of CFST composite frame is reliable and could be regarded as a helpful tool to expand the information on seismic behavior of CFST composite frame.

Abstract: This paper focuses on viscous dampers disposition schemes regarding the vibration control of the Mega-Sub Controlled Structure System (MSCSS) subjected to rare earthquake excitation. It is intended in this study to evaluate the dynamic characteristics of the MSCSS compared with the traditional mega frame structure. The optimum arranging scheme matched with dynamic characteristics of MSCSS is given by analyzing the dynamic responses of the structure with different arrangements of viscous dampers on structure. Characteristics of hysteresis curve of viscous dampers in the optimum scheme are also investigated. Results shows that when dampers are installed in the two middle stories of the two sub-structures, the acceleration and displacement of MSCSS are well controlled compared to the conventional mega frame, reaching the optimum control effect. It is also shown that dampers are an indispensable component on MSCSS configuration. Reasonable arrangement of dampers on MSCSS can accurately contribute to improve structure seismic resistance. The efficiency of this structural system is fully presented through the optimum arrangement.

Abstract: Wood knot image obtained by X-ray was done gray transformation. The contrast of the image after gray transformation can be enhanced obviously and the position of knot can be highlighted. Binary processing was adopted for the image after gray transformation. The defects areas of the binary images are filled. Then, invert the best binary image of wood defect, and then adduct the obtained image. The result of wood defect image plus is that defects regions take apart completely with their background, which means the image segmentation is completed. Wood utilization is improved. The experiment results show that this method is feasible and effective.

Abstract: Experiments were carried out to investigate the splitting properties of hybrid fiber reinforced concrete after exposure to elevated temperatures. Based on the experimental observation, the effect of steel fiber dosage, polypropylene (PP) fiber dosage and strength grade of concrete on the residual splitting strength of the concrete after being subjected to high temperature was systematically analyzed. Test data indicated that high temperature caused significant deterioration in the splitting strength of concrete; the addition of PP fiber and steel fiber could all effectively improve the residual splitting properties of concrete; the optimum amount of PP fiber and steel fiber were identified respectively; the degree of strength loss of concrete with different strength grades was very close to each other. A theoretical equation was proposed to predict the residual splitting strength of concrete after being heated to temperatures up to 800°C.

Abstract: Many marine oil pipelines are subject to varied degrees of corrosion, which gradually increases the leakage and fracture and other accidents. Because the marine pipelines are located in the complex environment and there are many forms of corrosion, the paper only studied parts of the corrosion. The finite element software was used to analyze the failure pressure of internal corroded pipeline under the earthquake, so as to provide the basis for appraisal of corroded marine pipeline.

Abstract: In this paper, the repair capacity of SMA wire by using internal and external installation was studied. The SMA wires were embedded in epoxy resin and silicon cement mortar beams made of polymer clay, and then three-point bending test was conducted on the composite beam. The ability of beams which embedded SMA wires was also studied. On the other hand, the SMA wires were installed in the external of the epoxy polymer clay cement mortar, then three point bending test was also used and its self-repair ability was also studied. The results show that the crack can be repaired very well under these two methods. If there are cracks in existing buildings, we can use an external installation method to repair them. In order to ensure the new buildings crack free, both methods are feasible.

Abstract: Glass fiber reinforced polymer (GFRP) bars were exposed to the solutions of different alkaline and chloride salt concentrations in order to examine the influence of different corrosion environment on the compression performance of GFRP bars. The results showed that the stress strain curves of the GFRP bars could be expressed as lines approximately. The compressive strength and elastic modulus gradually decreased with increasing of the corrosion time, and the decrease was more obvious in alkaline corrosion environment.