Advanced Materials Research Vols. 261-263

Abstract: We generally use methods of statistical forecasting and antithesis in projects post evaluation, but they can only be used as a qualitative evaluation but as a quantitative evaluation. Based on the fuzzy mathematics, this text presents a better quantitative mathematical analysis-fuzzy comprehensive evaluation method. And then, it established a model of comprehensive fuzzy assessment of projects post evaluation. At last, it illustrate that the model of comprehensive fuzzy assessment can evaluate projects post evaluation accurately and quantitatively.

Abstract: The polyurethane foam is a most common fuel in smoldering fire. A small scale experimental compartment was built. The width, thickness and density of polyurethane foam material were changed several times in the experiments. Temperature histories measurement and analysis gaseous were used to explore the transition’s mechanism. The results show that with the width increased, the surface area and the air flow rate which access to the inside of material have also increased, and the quantity of oxygen is sufficient, heat release quantity by carbon oxidation is increased. When the width reaches a certain value, polyurethane foam material transformed easier from smoldering to flaming combustion. The polyurethane foam transforms to the flaming combustion not only depends on the length, width size but also relates to the thickness closely. When thickness reached a certain size, the temperature also reaches a whole jump. And the material transforms to the flaming combustion finally. The oxidation of larger density polyurethane foam material produces more heat, and then accumulates heat in the polyurethane foam center to reach the required temperature of gas phase reaction and ultimately transforms to flaming combustion from smoldering.

Abstract: Flexible piers have been widely used in bridge engineering due to its superior ductility. The stirrup ratio and slenderness ratio were deemed to have a most important impact on hysteretic behavior of them. Five flexible piers were made under static vertical loads and low cyclic horizontal reversed loads. The process of test was introduced and failure mechanism, hysteretic behavior, skeleton curve, ductility, energy dissipation capacity, and stiffness degeneration of flexible piers were analyzed. Experimental studies show that (1) Failure mode of specimen is bending failure and their ductility factor falls between 4.15 and 6.30; (2) displacement ductility factor improves with increasing of the stirrup ratio. Stirrup could greatly improve the capacity on ductility and energy dissipation, while it has little impact on the bearing capacity; (3) ultimate bearing capacity decline with the increase of slenderness ratio, however, when the slenderness ratio member is larger, the hysteresis curve is fuller and energy-dissipation is better.

Abstract: A model of attenuation of residual strength with number of cycles has been founded .In this model the constant confined stress and maximum stress of fatigue loading are both considered. 55 specimens of plain concrete are tested under biaxial compressive fatigue loading with constant confined stress. Based on the data of experiment, the coefficients of the model are determined. The residual strength attenuating curves are shown in the paper. The model can be used to predict the residual life of specimen under biaxial compressive loading with constant confined stress. The results of prediction show that the suggested method is better than the Miner rule.

Abstract: The influence of geometric characteristic of geogrid on pullout behavior is still an unresolved problem in the application of geosynthetic reinforced soils. The laboratory pullout tests were employed to investigate the effects of geometric structure features on the pull-out test results. The results of this study indicate that the effect of geometric structure on pullout behavior is reflected in two aspects: geogrid type and mesh form of geogrid. The variation of geogrid types can lead to the changes of the pullout force and pullout modulus. For the latter one, the reduction of longitudinal and transverse geogrid ribs not only causes the decrease of friction and transverse rib bearing resistance, but also changes the mesh form which is the geometric structure of grids.

Abstract: The stress field around the tip of the blunt crack in rock-type materials under compressive loading is analyzed, and the relation of the stress field is set up. Compared to the stress field of the ideal mathematic crack, the effect on the distribution of the stress field by the thickness or the curvature radius of the blunt crack is considered. Based on the stress field, the two-parameter fracture criterion for the blunt cracks under compressive loading is set up. The two parameters in the criterion are related to the material property, and can be determined by the experiments or theoretical analysis. By the fracture model in the paper, the fracture analysis of the blunt crack under compression are carried out, and the theoretical results are in concordance with the experimental results, which shows the fracture criteria in the paper is available to the fracture analysis of the blunt crack.

Abstract: This article puts forward the design of wire rope tension detection system, and emphatically expounds how to design experiment device to simulate the actual movements of jacks. In the experimental process, the adjustable rheostat is altered to change current value, to simulate the output of sensors. Through breakpoint debugging function, every export of program is verified. The comparison between actual output and program output proves the correctness of synchronization algorithms. Technological aspects like measurement system, electrical system and computer communication are verified as well.

Abstract: Carbonation is one of the most common degradation reactions of concrete which greatly shortens the service life of steel-reinforced concrete structure. The carbonation of synthetic calcium silicate hydration derived from hydrated cement paste is investigated with microstructural characterization method including scanning electron microscopy, X-ray diffraction analysis, coupled TG-DSC analysis and Fourier transform infrared spectroscopy. The changes in the morphology, mineral composition and polymerization degree of the calcium silicate gel before and after the carbonation are investigated. The major finding of the research includes that the C-S-H collapses during the carbonation reaction, which actually densifies the microstructure. The major hydration product is calcite. The carbonation resistance of C-S-H is enhanced with increasing C/S ratio. The polymerization degree of C-S-H is increased by the carbonation reaction.

Abstract: Shrinkage stress of cementitious materials will generate if the dry shrinkage is restrained in drought condition. Shrinkage stress has influence on crack resistance of cementitious materials. The dry shrinkage of cementitious materials in different relative humidity was studied with Climate Simulation System. The dry shrinkage change law of concrete in 20°C, 60% relative humidity for 500 days and in 20°C, 10% relative humidity for 180 days was compared. The relation between water loss rate and shrinkage rate of cementitious materials in drought condition was analyzed.

Abstract: The paper use the finite element method, simulating the solidification process of metal matrix composite. Obtain the changing of temperature field about the solidification process and some temperature curve for special nodes. The results show that, due to the difference of heat transfer coefficient about the matrix and the metal the solidification process for composite materials showed the irregular temperature cloud, namely nonlinear temperature distribution. The simulation actually provides some guidance for synthesis of metal composite materials.