Advanced Materials Research Vols. 243-249

Abstract: Based on the bearing capacity behavior and load transfer mechanism of super-long pile in soft soil, the three-stage hyperbolic softening model is presented as the load transfer function of pile-side soil, and tri-linear model is introduced to simulate the characteristics of sediments in pile end. The differential equations are established by dealing with the states of static equilibrium, with considering the character of layered stratum and pile-soil interaction. The analytical solutions on different states are obtained by power series. Based on transfer matrix method, soil mechanics and elastic theory, a set of analytical equations and calculating method for the axial load-settlement curve of pile top in layered ground are established. Lastly, the calculating parameters are obtained by theoretically approaching to actually measure load-settlement curve in soft soil area. The calculating contrast to adjacent test pile is carried out by the method and the results are satisfactory.

Abstract: Currently, super-long piles are designed based on the theory of normal long piles. There is no recognized reasonable mechanical model for qualitative analysis. In this paper, based on load transfer function method, an improved load transfer model is proposed, which gives consideration to both the degradation of skin friction and the asynchronous work between lateral friction resistance and pile-tip resistance caused by pile-soil slip. By applying it in various working conditions, the corresponding pile-soil displacement and axial force of super-long piles are derived. Finally, the proposed model is validated by comparing its analytical solutions to the results of FEM and practical survey of super-long piles, and it provides a new efficient approach for the study of the mechanical behavior of super-long single pile.

Abstract: This article establishes a circular truncated cone model of the post-grouted induration end,brings forward a integrative influence coefficient and edtablishes a simple vertical bearing capacity caculation formula of post-grouted piles with the broaden diameter caculating the end resistance of the pile, which has considered the influence of mortar volumn.According to a certain number of engineering experiment,the tesults derived from this formula can fit the static loading test bearing capacity of the post-grouted drilled piles well,which can provides a certain engineering practical reference value.

Abstract: The conception of twice prestressed composite structures (TPCS) was proposed in order to solve great distortion problems in prestressed concrete structures. Through decomposition of the total prestress, we define the 1st stage as one part of the prestress acting on a prefabricated beam, and the 2nd as the other part on a post-pouring structure. This kind of structure could substantially decrease its distortion and enhance the efficiency of prestress, at the same time contributing to flexibly laying the prefabricated concrete. A continuous curved prestressed concrete box girder bridge was modeled with the FEM software ANSYS, taking into account the ordinary steel and prestressed losses. The aim is to analyze the deformation, stress performance, the impacts of the primary prestressed force value on the anti-deforming performance as well as bearing load performance of the twice prestressed composite curved beam. The conclusion could provide a basis for the application and promotion of the structure.

Abstract: In this paper, two kinds of mega-frame structures have been simplified to the series-parallel-connection model which considered with joint rotation. The stiffness matrix and mass matrix also have been established and predigested. The vertical stiffness matrix and mass matrix have been obtained. There has been a dynamic characteristics analysis on the structures subjected to vertical seismic force with the method of analysis of step-by step integer. From the results some dynamic characters of structures subjected to vertical seismic force have been obtained.

Abstract: Bases on experimental investigations of HSC and NSC, HSC’s mechanical behavior, failure mechanism, fracture toughness, characteristic length and damage feature are discussed in the paper, and the formula for flexural strength and comparative toughness is given. The results show that the HSC has a good uniformity of structural entity and large cracking resistance. In addition, HSC is more brittle and more vulnerable to damage than NSC.

Abstract: Waste concrete, broken bricks, mortar were very good renewable resources. 6 mix proportions were designed with construction waste after sieved and broken, and fiber was added to increase its crack-resistance. It was examined that the mechanics indexes of the cement stable construction waste mixture would change under different aggregates combination and different the proportion by experiment. it was found that the mechanical characteristics and functions varied because of various aggregates, and the regular pattern was also found different aggregates combination and different proportion influence mechanical characteristics of cement stabilized construction waste mixture.

Abstract: In order to research the influence of basalt fiber on the crack and deflection of the reinforced concrete beams, four basalt fiber reinforced concrete beams with the key parameters of length which were 12mm and 30mm and volume ratio which were 0.1% and 0.2% were designed and made. The test data was obtained through the bending experiment and the comparison with the common reinforced concrete beam. The result shows that it is obvious to control the crack and deflection of the test beams with the increasing of basalt fiber characteristic parameters. The calculation method of the maximum crack width of the basalt fiber reinforced concrete beams were presented based on the method of common concrete beam, which can provide the theoretical basis for the engineering practice.

Abstract: Reticulated shell is one type of the common spatial structure form. This paper proposes a vibration reduction method by supplementing viscous dampers in the reticulated shell. It analyzes the seismic performance on the optimum partial double-layer reticulated shell with dampers by ANSYS soft, gains the stress in the members and the nodal displacements, and compares the dynamic responses between the normal and vibration reduction structure. By means of different parameters, the rules of vibration reduction effect in the reticulated shell with viscous dampers are acquired. It is shown through the calculation that the method developed in this paper is efficient for the dynamic analysis of the reticulated shells.

Abstract: Asphalt aging occurs both in the construction period and in the service period of asphalt pavement. It is believed that aging could have a big influence on the rheological mechanical and adhesion characteristics of the asphalt. Asphalt aging is a process associated with a lot of factors as heat, rays, oxygen, and ozone. In the aging process, some chemical compositions of asphalt are subject to be activated by these factors and undergo some chemical changes. A theoretical analysis at a chemical reaction level to the asphalt aging mechanism is presented in this paper. Asphalt aging can be sorted as thermal oxidation aging, ray oxidation aging, and ozone oxidation aging. The thermal oxidation aging usually occurs in the components with chains and double bonds in their molecules. The ray oxidation aging can be found in components with one carbonyl or more carbonyls. Those components with a π key in their molecular structures are prone to the ozone oxidation aging.