Applied Mechanics and Materials Vols. 587-589

Abstract: The highway and railway bridge across Songhua River in Harbin, which belongs to the existing Bin-Bei line (i.e Harbin-Bei’an ), was built in 1993, and it was formerly named as Dongjiang Bridge. After many years’ operation, tremendous damages occurred. Hence, on December 25th 2006, highway located in upper level was closed, and railway located in lower level took speed-limiting as well as quantity-limiting operation measures. Even though, there were still security risks, and endangered traffic safety. The reconstruction of this bridge has a strategic importance on thoroughly removing bottleneck and security risks caused by railway channel and urban road transport of Bin-Bei line, perfecting overall arrangement of both railway and highway road net, improving integrated transport capacity, as well as developing local economy. Therefore, it is necessary to have comprehensive comparison for the bridge site scheme selection works.

Abstract: Based on existing research and theory about the whole pavement damage at home and abroad. This document introduces single pavement damage indexes, including pavement damage length, width, depth and full lane-width. Then, from the perspective of impact of single pavement damage on vehicle operating, the severity level of pavement damage is quantitatively divided as light, medium, less severe and severe. According to the full width of the lane, the severity level of pavement damage can be divided as the smooth, depression, compact and poor types.

Abstract: Subgrade stress under static vehicle load is different from that under moving load. In order to study the law of subgrade dynamic stress under moving vehicle load, the paper established the three-dimensional analysis model with finite element software and calculated the subgrade dynamic stress of different depth. It is concluded that subgrade dynamic stress decreases with the increase of depth and the smaller the depth is, the faster the degradation is. To a certain depth, subgrade dynamic stress changes a little. Meanwhile, the paper analyzed the effect of surface layer modulus and thickness, roadbase modulus and the thickness, subgrade modulus on subgrade dynamic stress. It is concluded that surface layer modulus and thickness have little effect on subgrade dynamic stress , subgrade dynamic stress decreases when roadbase modulus and the thickness increase, especially for the depth of the subgrade is relatively small. Subgrade dynamic stress increases with the increase of subgrade modulus. Increase trend is more obvious when the depth is small.

Abstract: It was more convenient to describe track irregularity by the spatial frequency.The conventional frequency-domain transfer function can not effectively solve the vibration equation when anlysis of the vibration response to structure of vehicle-track dynamic coupling system, the time domain numerical integration must be used to solve it.The trigonometric series superposition method can be used to convert track irregularity spectrum into time domain frequency power spectral density function, and then turn the simulated irregularity samples into spectral density by the Inverse Fast Fourier Transform (IFFT), which compared with the theoretical spectral density to test the reliability of the sample. The results show that the simulated sample have the same characteristics with the given power spectral density function, which demonstrate the high reliability of this sample and it can be used as the external excitation of the locomotive vehicle system.

Abstract: MHB technique is applied, in superhighway cement concrete pavement resurfacing project (“white to black” project in short), to break the pavement surface and build the new pavement taking the broken one as the base or subbase, which makes good use of the remains in a very economical and environmentally friendly way, and solves the problem of reflective cracks appearing on the pavement surface after reconstruction as well. This thesis confirms the relevant parameters of MHB construction machinery, construction quality and intensity testing, etc by making researches in test sections, discusses the key process in construction with MHB technique and the relevant quality control measures during construction, and puts forward the ideas of reconstructing the pavement with MHB technique while making no influence on the superhighway traffic, even when the traffic if heavy.

Abstract: The load transfer mechanism between the dowel and the concrete is a complex phenomenon. This mechanism depends mainly on a parameter known as the modulus of dowel support (K), the value of which can be determined by load testing. A high modulus of dowel support value indicates a good contact between the concrete and the steel dowel. There is a lack of sound approach to identify with any degree of accuracy the modulus of dowel support (k), which makes it difficult to rely on the analytically developed formulas that are sensitive to its value. The obtained numerical results were validated with classical analytical solutions of shear and moment along the dowel. The group action of the dowel bar system was examined and useful relationships have been developed for estimation of the relative load shared by individual dowel bars. These useful relationships have been used to developed prediction Model to predict the shear force in dowel group action of dowel bar system and deflection at the loading nodal point. The prediction Model results for shear force in dowel group action of dowel bar system and deflection at the loading nodal point were relatively close to the F.E. Model results, with the different range between 2.2% to 7%.

Abstract: In order to explore performance and economic benefits of the most commonly used fiber asphalt mixture, four types of fiber asphalt mixture were studied in this paper through a series of capability tests, such as water stability, high stability, low temperature crack resistance and fatigue stability test. Based on dynamic stability, low temperature bending strain, freeze-thaw splitting strength ratio, fatigue life and cost per square meter as the evaluation index, Grey Relational Analysis (GRA) was proposed in this study to determine the best performance and economic benefits of fiber asphalt mixture. The results show that Fiber B asphalt mixture only has better anti-cracking performance in low temperature and fatigue life,but fiber C asphalt mixture has better performance and economy than the other three fiber asphalt mixtures under the same conditions with grey relational analysis.

Abstract: To study semi-rigid base asphalt pavement response characteristics, two structural APT test roads of cement stabilized aggregate and lime fly-ash stabilized aggregate were constructed, and accelerated loading test was developed. After certain number of wheel loads (70,000 times) pavement deflection basin parameters were detected by using the falling weight deflectometer, then modulus of each pavement layer was back-calculated, dynamic response was analyzed. Studies have shown that the modulus of semi-rigid base decay faster, and with decreasing thickness of the semi-rigid base, the greater the rate of decay of modulus; cement stabilized aggregate decay rate is greater than that of lime fly-ash stabilized aggregate.

Abstract: Segregation is one of the important reasons that cause the early damage of asphalt pavement, so it is of great significance to discuss the standard for evaluating segregation to control quality of pavement during constructing. SMA-13 specimens of different gradation segregation and aggregate-asphalt segregation are designed to discuss the effects of different levels of segregation on air voids and bulk specific gravity of SMA-13 Marshall specimen. And the classification standards for gradation segregation are established based on the test data with reference to the air voids range that proposed by United States. In order to recognize the levels and site of segregation quickly and accurately in the entity project, the ratio of bulk specific gravity and the theoretical maximum specific gravity of standard grading, that is the evaluation standard of compactness, is put forward as the evaluation standard for segregation of SMA-13 asphalt pavement in field test.

Abstract: In the course of road maintenance, importance has been gradually attached by administrative authorities to precast pavement for its advantages like quickness, endurance and eco-friendliness. To ensure the smoothness of precast pavement, analyses and researches were done in terms of, say, precast pavement slab precision control, base course treatment, fabricated pavement slab leveling and treatment of joint faulting, and a control measure to ensure and improve the smoothness of precast pavement is suggested with consideration given to its service effectiveness in actual projects.