The performance of hybrid long-span cable stayed bridges using advanced composites.

摘要

The development of the cable-stayed bridge central span has almost reached the technical limit for traditional materials, construction technology and bridge system capability. An innovative solution has been proposed in this research, which introduces a new hybrid long span cable stayed bridge system utilizing advanced composite materials for the deck and the stay cables. The system can be constructed for longer spans, as the deck and cable stiffness and strength to weight ratios are significantly improved. This diminishes the critical compressive stresses of the traditional deck in the pylon zones, and enables the use of longer cables.; To overcome the complications resulting from the need to integrate the advanced composite material micro/macro design, and the resulting mechanical properties, to the structural modeling, a holistic iterative analysis and design procedure involving Multi-Scale Modeling Technique is proposed. The Stochastic Finite Element method, using a two-phase stochastic process, is introduced as an integrated part of the analysis and design procedure to evaluate the mechanical properties of the chopped FRP material, with single or multi-fiber types. On the other hand, the "Laminas Dominant Fiber Alignment" principle, LDFA, is introduced together with a simplified rule of laminate lay-up. The resulting laminate architecture gives better static and dynamic performance than simple orientation arrangements.; Four innovative deck section models have been introduced and the hybrid bridge systems are scaled to match the bridge configurations and geometric characteristics of three of the world's longest span cable stayed bridges, of central span ranged from 465 m to 890 m. The hybrid bridge system gives quite acceptable maximum deflections, while the lateral and the longitudinal displacements are very small in general. The Tsai-Hill Failure Functions have values much lower than the criterion limit. The stresses in the stay cables and the chopped FRP parts are far lower than the strength of their materials. The natural frequencies for most of the cases are within the known ranges of this type of structure. Considering the static and the aerodynamic results, it is apparent that some of the proposed deck section models are efficient and stable for extremely long bridge central spans.