| In order to completely improve the durability of the structure,we need to develop new materials that are more environmentally friendly to replace traditional steel.Carbon fiber reinforced polymer(CFRP)cable has extremely high specific strength and stiffness,far better corrosion resistance than steel,excellent equivalent modulus and excellent fatigue performance fully demonstrate its advantages in the application of bridge structure,and has broad application prospects.However,the anchoring devices of traditional steel cable anchorage are no longer suitable for CFRP cable anchorage and CFRP bars have high creep properties.Therefore,the research on the anchoring system of large tonnage CFRP cable anchorage has great theoretical and practical significance.The main research contents and conclusions of this thesis are as follows:(1)3D finite element analysis was used to optimize the parameters of two new CFRP cable anchoring systems for better application to 5000 k N cable force anchoring systems.When active powder concrete is used as load transfer medium,the radial stress can be well controlled in a low range when the friction coefficient is 0.1.The lower the friction coefficient is,the more beneficial it is to reduce the slip amount.The friction coefficient is recommended to be kept at about 0.1.When the polymer mortar is used as the load transfer medium,the friction coefficient is negatively correlated with the radial stress and slip,and the friction coefficient is recommended to be between 0.1 and 0.2.During the stress process of the lower cable of the variable Angle multi-end internal cone anchoring tool,the clips exert radial extrusion pressure on the prestressed tendons,and rely on the friction between the two to anchor the prestressed tendons,forming a self-locking mechanism.The clips have good selfanchoring performance and self-locking ability.(2)Based on the existing geometric data of Sutong Bridge,a long-span CFRP cable cable-stayed bridge with a main span of 2120 m meters was designed,and a three-dimensional simulation model was established using finite element software.The internal forces of long-span cable-stayed Bridges are analyzed by finite element method.The displacement of the main girder of the bridge should be within L/400,which conforms to the reasonable bridge state.The axial forces of the main beams are distributed symmetrically on the bridge.The bridge is not under all the pressure,it is under tension in the middle of the bridge.The abrupt change of axial force is the bifurcation of the cable tower,and the axial force distribution is divided into two sections.Both segments decrease linearly with increasing height.(3)In view of the fact that the semi-logarithmic model does not consider the effect of stress σ on creep,a creep prediction model is proposed.The creep model is used to fit the data of literature research.The creep properties of three kinds of CFRP bars with different safety factors were studied to determine the parameters of the proposed creep prediction model and verify it.The results show that both the semi-logarithmic model and the creep prediction model proposed in this thesis can predict the creep performance well.However,the creep prediction model proposed in this thesis has reflected the influence of sustained stress in the same equation,and this creep prediction model has certain universality. |
