Mechanical Characteristics and Defining of Extradosed Bridges

The extradosed bridge is a new bridge system which was developed by Jacques Mathivat with his alternative design for the Arre^t Darre viaduct in South West France.At present,extradosed bridges are developing rapidly in China.The paper summarizes the development trends of the extradosed bridges.When analyzing mechanical properties of extradosed bridges,a conception of the influence degree of cables on load carrying is used to quantitatively analyze the contribution of cables to the main girder.In view of these analyses,a parameter is put forward——the characteristic parameter of extradosed bridge,which signifies the main designing parameters-the height of tower,area of cable and stiffness of girder.It can comprehensively reflect the structural and mechanical properties of extradosed bridges.Then the characteristic parameter values of a typical extradosed bridge——the Xiaoxihu Huanghe River Bridge of Lanzhou——are analyzed on the basis of analysis of the influence degree of cables on load carrying,the properties of the extradosed bridge are quantitatively described by using the coherency of the two above mentioned parameters.Upon analyzing the characteristic parameters and influence degrees of cables on load carrying of ten bridges in China,it is shown that the characteristic parameter of the extradosed bridge can be used to represent mechanical properties of extradosed bridges comprehensively and distinguish between cable-stayed and extradosed bridges.So the characteristic parameter of the extradosed bridge based on the influence degree of cables on load carrying is recommended to define the extradosed bridge.The paper has reference value for design and deep research of extradosed bridges and cable-stayed bridges.