Mechanics Performance Analysis Of The Super-span Suspension Bridge With CFRP Cables

In the new century, the study of super-span suspension bridge, in particular, the application of new materials in super-span suspension bridge, is attached the growing importance to designer. As super-span brige structure is flexible, its effects of geometric noulinear are become more obvious. The mechanics performance and wind stability are become more complex in the form of bridge, therefore it becomes essential to carry out the research in this field.The calculation theories of suspension bridges, including elastic theory and deflection theory, finite displacement theory and analytic calculation theory used presently are introduced systematically. Moreover, the merits and faults of the latter two methods are compared and analyzed, which provides theoretical basis for the analysis of static and dynamic characteristic of suspension bridges.The static performances of the 2000m-span,3000m-span suspension bridges with CFRP cables and steel cables and 5000m-span suspension bridge with CFRP cables are analyzed making use of the finite-element method, including under the action of dead load, vehicle load and temperature. The main cable tension and suspender force of CFRP cable suspension bridges are less than those of the steel cable suspension bridges, but the stiffening girder moment of the former is slightly larger than that of the later, when they are under the action of dead load. In the vertical load effect, the vertical displacement and torsion angle are greater than those of the steel cable suspension bridge, but the deformations are small, which can meet the actual demand. Temperature effect on steel cable suspension bridge is great, but it is very small on the CFRP cable suspension bridge, which is because that the linear expansion coefficients of two materials are different.The dynamic performances, including the natural vibration frequency and vibration modes of the 2000m-span,3000m-span suspension bridges with CFRP cables and steel cables and 5000m-span suspension bridge with CFRP cables are analyzed making use of the finite-element method. The fundamental vibration mode shapes of CFRP cable suspension bridges are similar to those of the steel cable suspension bridges. The lateral vibration frequencies of CFRP cable suspension bridges are slightly less than those of steel cable suspension bridges, but the vertical vibration fundamental frequencies of the former are slightly larger than those of the later. The torsional vibration fundamental frequencies of the former are significantly higher than those of the later, so the wind stability of the former is better.The preliminary study on structural measures of improving wind stability of super-span CFRP cable suspension bridge is carried out, which provides basis for further research such as wind-induced vibrations and seismic analysis. Different forms of structural models, including cross-cable model, spatial main cable model and cable truss bridge model are established. The wind stabilities of several major programs are compared and some conclusions which has a certain reference value are coincided.