Study On Structural System Of Ex/Intradosed Cable-Stayed Bridges With Continuous Cables For High Speed Railway

As an extension of combined cable-stayed system, the ex/intradosed cable-stayed bridge with continuous cables is an updated version of the extradosed cable-stayed bridge. With the characteristic of slim girder, light weight, large stiffness, low dynamic response, the new system is suitable for high speed railway bridges, which is strict for stiffness requirement. So far, systematic researches on this new bridge system have not been carried out, and most of them are concentrated on highwayrather than railway.Based on the existing researches, structural rearrangement has been carried out, and mechanical properties under loads of high speed railway have been studied, including the stiffness of the system, internal forces of the girder and dynamic performance. Parameters have been analyzed on structural behavior and their reasonable range have been summarized, which can be used for engineering design. The main work and achievements are as follow:1) Structural arrangement and the innovative cable-strut unit is developed for ex/intradosed cable-stayed bridge for high speed railway. Adjustive analysis by the unknown coefficient of load, which is based on the influence matrix theory, shows that the configuration and internal force of the new structural system can be adjusted by drawing the cables. Simple model analysis shows that the stiffness is not sensitive to cable force so that linear analysis is applicable and live load analysis can be discussed separately.2) The equivalent stiffnessequation of the new structure is derived by the displacement method and the influence factors have been qualitatively analyzed. It shows that the equivalent stiffness is relative to pylon’s height, strut’s length, span length, the stiffness of the girder and cables and so on. Qualitative simulation of the construction process is carried out by using traditional cables as temporary support, indicating that it is feasible to construct the new structure by modern technology.3) Comprehensive investigation of structural and geometric parameters derived from equivalent stiffness equation is conducted, and the stiffness of the system, internal forces of the girder, dynamic performance under high speed train and other mechanical indexes have been studied. The mechanical advantage of the new structure is proved in contrast with traditional extradosed cable-stayed bridge. Reasonable range of parameters is presented.4) Further analysis has been expanded considering different pylon-girder-pier connections and models of PPG and PP-G are developed. Compared to traditional structure, mechanical performance under static load, dynamic effect, earthquake action and temperature variation has been studied, which provides comprehensive understanding of structural performance of ex/intradosed cable-stayed bridge.