Advanced Materials Research Vols. 255-260

Abstract: Analyzing the basic theory of stability, with a high pier of large span prestressed concrete continuous bridge as the example, the stability was analyzed when constructing, considering wind load, hanging basket, pier etc. Both eigenvalue and mode are got for the longest cantilever ting condition, the sensitivity of stability to various loads being analyzed. It is concluded that the unbalanced weight and the falling of basket are the main factors.

Abstract: The impact factors for vehicle load were ever characterized by varied parameters among different countries, and it is now commonly described by the fundamental frequency of the first bending mode for straightened bridges, but there are still no computation formulae proposed for concrete curved bridges. Massive vehicle-bridge interaction analysises are carried out on concrete curved box girder bridges with different span length, curvature radius, section type, span number and boundary conditon, using a validated numerical method. Based on the obtained results, the impact factors for varied effects are discussed, as well as their correlation with parameters of central radius, ratio of bending to torsional rigidity, integral impact coefficient and the fundamental frequency of vertical bending mode. It is indicated that, the impact factor of interal forces, deflection and reaction force are minus correlated with the discussed parameters except for ratio of bending rigidity to torsional rigidity. The impact factors are most closely correlated with the fundamental frequency of vertical bending mode, so it is best suited to characterize the change of impact factors.

Abstract: This paper is described about the research work on the PC beam for extradosed prestressed bridges. After summing up domestic extradosed prestressed bridges with PC beam, we recommended that the PC beam should be more diversity and creative. We have drown some conclusions through the numerical analysis and reduced scale prototype model test for Jiayue Bridge in Chongqing China, this bridge has double-cable-plane, and the PC beam’s broad flange is 8m. Finally, we suggested that further research on the PC beam of extradosed prestressed bridges should focus on the phenomenon of shear lag and extra-prestressing, etc.

Abstract: A narrow steel truss girder suspension bridge was designed for pedestrian and livestock in pasture in Xinjiang Province, China. For the complex wind climate at bridge site, the cautious designers resorted to wind tunnel test to confirm the aerodynamic stability of the bridge. The analysis and results from wind tunnel test conducted in Chang’an Wind Tunnel Laboratory indicated the original scheme must be changed considerably to improve the aerodynamic stability under action of wind. Considering the shape feature of Siudirgol Bridge and its geographical location, section model with such mitigation measures as auxiliary cables and central buckles were re-tested in wind tunnel joint with analysis. The auxiliary cables and central buckles can increase considerably the fundamental frequency of the bridge and hence the critical wind speed of flutter.

Abstract: The hydrodynamic characteristics of a circular cylinder in two-dimensional unsteady uniform cross flow was simulated numerically by the laminar model with the reasonable mesh used the method of fluent. The focus of this numerical simulation was to research the characteristics of pressure distribution, drag coefficient and lift coefficient, and the Strouhal number was calculated at Reynolds-numbers value of 200. The results agree well with experimental data and other numerical results according to the reference. In order to study the control measures of the flow over a circular cylinder, the different baffles inserted at various locations downstream of the cylinder have been compared. The results shows that the vortex shedding of flow over a circular cylinder could be well controlled by place the baffle at a right position of the downstream medial axis of the cylinder, which could reduce drag and resist vibration.

Abstract: According to the recent series of bridge collapse ,and points out the importance of safety testing and bearing capacity evaluating of the bridge in active service. RC simple beam bridge occupies a considerable proportion of the existing bridge in China, this paper discussed the commonly used inspection methods and its advantages and disadvantages, and draw a conclusion that load test method is the most commonly used and the most reliable way.Then, take “Ren jia dam bridge”bearing capacity inspection test as a example ,which in the “5.12 earthquake” disaster areas JiangYou ,MianYang.Discusses the whole prosess of bearing capacity calculation and field inspection in detailed.Compares the calculation results with the field inspection,the bearing capacity of the bridge meets the requirements of passing through "80t" vehicle loads, although is strongly impacted by the seismic force.

Abstract: The reasons why the producing of the difference in temperature distributing and thermal stresses of box aqueduct under solar radiation are analyzed. The difference in temperature distributing and thermal stresses are effectively simulated by the finite element software ANSYS.The calculation results indicate that concrete box aqueduct body inter-surface whatever along the longitudinal and transverse will produce considerable thermal stresses under solar radiation, and its value has exceeded the design of concrete tensile strength. Therefore, the thermal stresses under the solar radiation must be considered in the design of box aqueduct body structural. We should appropriately configure temperature reinforcing steel bar.

Abstract: On the foundation of harms in the analytical arc-arched bridge plant disease up, this text propose the bridge floor makes up the strong level and the arch ring increases the section reinforcement, the arch ring spandrel wall steel member pulls ties supplements the pile foundation synthesis reinforcement with the lower part the plan. It not only improves the bridge bearing capacity and structure whole rigidity, also controls the development of the crack nicely, which shows certain model significance in the old bridge reinforcement transformation.

Abstract: In view of huge destructibility of the near-fault ground motions, structures with long natural vibration period are liable to fall into nonlinear reaction stage. Based on a full understanding of the near-fault seismic spectrum characteristics, the out-of-plane seismic response of a long span concrete-filled steel tube (CFST) arch bridge was studied in depth, and the research result could offer a reference for near-fault aseismic design.

Abstract: Based on the equivalent stiffness and equivalent stiffness ratio method, an approximate method suitable for hand calculation is proposed to calculate the deflection of variable box section girder bearing load, in which, the double effects of shear lag and shear deformation can be taken into account. It shows that the deflection calculated by elementary beam theory without considering shear lag effect and the shear deformation is smaller, comparing to results calculated by the approximate method proposed in the paper. For such variable box sections girder, transverse shear deformation effect is greater than the shear lag effect when calculating the deflection. The approximate method offers a simple and effective calculating method for the design of box girder with variable cross section, in which, analysis formula can be applied in engineering practice through simple revision.