Applied Mechanics and Materials Vols. 71-78

Abstract: The cement concrete pavement surface are high, and its rigid structural integrity depends on the integrity of institutions and the plate itself, the overall rigidity of the lower body performance. However, the current board of cement concrete pavement breaking, cracking of roads has become an important common quality problems. For cement concrete road surface plate, the type of cracking, resulting in destruction of the reasons, etc., proposed prevention measures and precautions for disposal for the relevant officers.

Abstract: Hou Tian desert is located in the south of Xinjian County, Nanchang, Jiangxi Province, which is the largest sub-tropical land of Desertification. This paper explores and analyzes the existing conditions of the desert and development, under the premise of reasonable governance desert and protecting the surrounding environment, then proposing the green ecological development planning program of this project and the overall spatial layout.

Abstract: The computational model of numerical analysis of a suspended pre-stressed steel reticulated shell subjected to fire load is established with using the software Marc. Based on the model presented here, numerical analysis of thermal response and structural response of the pre-stressed steel structure are computed for the key nodes of the structure. The different location of fire source and different space height are considered for analysis of response temperature, displacements and stresses of the pre-stressed lattice shell. It is shown that the air temperatures was much higher than the response temperatures of the nodes of the lattice shell during a quite period of time after a fire takes place, and the temperature of the cable nodes are also less than the air temperature near the nodes. It is also concluded that displacement of the node right above the inner cable is the maximum among the four nodes as the fire source is located at the position under the middle cable.

Abstract: The post-fire behavior of a set of ceramsite concrete filled steel tubes (note as CCST) after exposure to fire are experimentally studied. Effect of the maximum value of fire response temperatures of the tubes and their geometric parameters on the strength and ductility of the specimens were especially discussed. The test results show that the specimens of CCST have higher post-fire bearing capacity and better ductility, there was no obvious descent segment in post-fire load-displacement curves of the most specimens subjected to fire load. It was concluded that the maximum response temperature of specimens has great effect on the post-fire bearing capacity of concrete-filled steel tubes subjected to fire load.

Abstract: A kind of FGD gypsum from Ningbo Beilun Power Plant of China and fly ash were used as the raw materials with which a complex cementing material was made. Effect of the related factors such as water proportion, mineral admixtures and chemical activators on characteristics of Hemi-hydrate FGD gypsum-fly ash complex cementing material is studied through a number of single factor experiments. The experimental results show that an appropriate amount of admixtures can effectively improve the strength of the Hemi-hydrate FGD gypsum–fly ash complex cementing material presented here. It is concluded that the strength of HFGD-FACM is best as the ratio of HFGD gypsum and fly ash is 1:1 and proper water aggregate proportion is 0.45~0.50.

Abstract: The computational model of numerical analysis of a suspended pre-stressed steel reticulated shell subjected to fire load is established with using the software Marc. Based on the model presented here, numerical analysis of thermal response and structural response of the pre-stressed steel structure are computed. The different space height and different rise-span ratio are considered for analysis of response temperature, displacements and stresses of the pre-stressed lattice shell under fire for one fire source. It is also shown that displacement of the node right above the inner cable is the maximum among the four nodes presented here as the fire source is located at the position right below the second-ring cable of the structure. It is concluded that the influence degree of space height of the structure on the fire response of the structure is not great, but rise-span ratio has obvious and great effect on displacements and stresses of the pre-stressed steel structure with large span in fire.

Abstract: The post-fire performance of a set of ceramsite concrete filled steel tabular short columns (noted as CCSSC) after exposure to fire are experimentally studied. Effect of the maximum value of fire response temperatures and geometrical parameters of the composite columns on the strength and ductility of the specimens were especially discussed. The test results show that the specimens of CCSSC have higher post-fire bearing capacity and better ductility, and both of maximum response temperature and geometrical parameters of the specimens presented here have great effect on the post-fire bearing capacity and ductility of ceramsite concrete-filled steel short columns after exposure to fire.

Abstract: It is the important way to improve thermoelectric properties of skutterudite materials by doping with rare earth elements. The mechanisms of improving properties of bulk RE_xCo₄Sb₁₂ materials prepared by mechanical alloy and spark plasma sintering (MA-SPS) at 650°C were investigated by analyzing the composition, microstructure and atomic occupying locations. According the results it can be considered that the mechanism to improve the thermoelectric properties of rare earth elements is that rare earth element Ce in the samples mainly plays the doping role in reducing the resistivity of the sample and improving the conductivity, so that it makes the figure of merit ZT of samples increase significantly.

Abstract: For investigating the thermoelectric properties, bulk FeSb₂ and the composite of CoSb₃:FeSb₂=7:3 was prepared via sintering. The phases of samples were analyzed by X-ray diffraction and their thermoelectric properties were tested by electric constant instrument and laser thermal constant instrument. Experimental results show that, bulk FeSb₂ and the composite of CoSb₃:FeSb₂=7:3 are P-type semiconductor materials. The electric resistivity of bulk FeSb₂ sample increases with temperature rising while that of the composite (CoSb₃:FeSb₂=7:3) decreases with temperature rising. The Seebeck coefficient of the composite (CoSb₃:FeSb₂=7:3) is evidently higher than that of bulk FeSb₂. The thermal conductivities of the composite (CoSb₃:FeSb₂=7:3) are relatively lower than those of bulk FeSb₂. The ZT values of bulk FeSb₂ sample are lower than those of the composite (CoSb₃:FeSb₂=7:3), that of the later increases with temperature rising at 100~500°C, the maximum value is up to 0.1647.

Abstract: Microwave treatment is a newly developed technique to expel resin from pine wood by generating high internal steam pressure. To understand the mechanism of deresination process during the treatment, a mathematical model was developed and was used to predict its critical conditions. The model indicated that the critical pressure inside Masson pine wood was 1.17×10⁵ Pa and its corresponding critical temperature was 104 °C in order to expel the resin mixture from the interior to the surfaces. The experiment results showed that during microwave deresination large quantities of the resin overflowed to the wood surfaces when the temperature of the pine wood was controlled in the range 104-112°C. The result observed during the microwave treatment matched well with the critical temperature predicted from the simple mathematical model. The validated model could provide some understanding and improvement of microwave deresination process.